U.S. patent application number 12/333109 was filed with the patent office on 2010-06-17 for implant planning for multiple implant components using constraints.
This patent application is currently assigned to MAKO Surgical Corp.. Invention is credited to Louis Arata, ALEXANDRA BELLETTRE, Jason Otto, Robert Van Vorhis, Jason Wojcik.
Application Number | 20100153081 12/333109 |
Document ID | / |
Family ID | 42241580 |
Filed Date | 2010-06-17 |
United States Patent
Application |
20100153081 |
Kind Code |
A1 |
BELLETTRE; ALEXANDRA ; et
al. |
June 17, 2010 |
IMPLANT PLANNING FOR MULTIPLE IMPLANT COMPONENTS USING
CONSTRAINTS
Abstract
Described are computer-based methods and apparatuses, including
computer program products, for implant planning for multiple
implant components using constraints. A representation of a bone
and a representation of a first implant component are displayed
with respect to the representation of the bone. A representation of
a second implant component is displayed, wherein the first implant
component and the second implant component are physically separated
and not connected to each other. A positioning of the
representation of the second implant component that violates at
least one positioning constraint is prevented, wherein the
positioning constraint is based on the representation of the first
implant component.
Inventors: |
BELLETTRE; ALEXANDRA; (Salt
Lake City, UT) ; Arata; Louis; (Mentor, OH) ;
Van Vorhis; Robert; (Davis, CA) ; Otto; Jason;
(Plantation, FL) ; Wojcik; Jason; (Weston,
FL) |
Correspondence
Address: |
PROSKAUER ROSE LLP
ONE INTERNATIONAL PLACE
BOSTON
MA
02110
US
|
Assignee: |
MAKO Surgical Corp.
Fort Lauderdale
FL
|
Family ID: |
42241580 |
Appl. No.: |
12/333109 |
Filed: |
December 11, 2008 |
Current U.S.
Class: |
703/11 ;
715/764 |
Current CPC
Class: |
G06F 19/00 20130101;
G06T 19/00 20130101; G06T 7/33 20170101; G06T 17/20 20130101; A61B
34/30 20160201; G16H 20/40 20180101; A61B 2034/2055 20160201; G06T
2200/24 20130101; G16Z 99/00 20190201; G16H 30/20 20180101; G06T
2207/10081 20130101; A61B 2034/102 20160201; G06T 2207/30008
20130101; A61B 5/4504 20130101; A61B 34/10 20160201; A61B 5/4528
20130101; A61B 5/4514 20130101; G16H 50/50 20180101; A61B 5/745
20130101; A61B 2034/105 20160201 |
Class at
Publication: |
703/11 ;
715/764 |
International
Class: |
G06G 7/60 20060101
G06G007/60; G06F 3/048 20060101 G06F003/048 |
Claims
1. A surgical planning computerized method comprising: displaying a
representation of a bone and a representation of a first implant
component with respect to the representation of the bone;
displaying a representation of a second implant component, wherein
the first implant component and the second implant component are
physically separated and not connected to each other; and
preventing a positioning of the representation of the second
implant component that violates at least one positioning
constraint, wherein the positioning constraint is based on the
representation of the first implant component.
2. The method of claim 1 further comprising: calculating a
plurality of areas representing cartilage; and preventing a
positioning of the representation of the first implant component
that violates a second positioning constraint that is based on the
plurality of areas representing cartilage.
3. The method of claim 1 wherein the at least one positioning
constraint comprises a rigid constraint between the representation
of the first implant component and the representation of the second
implant component, wherein the rigid constraint prevents a
positioning of the representation of the second implant component
that is independent of the representation of the first implant
component.
4. The method of claim 1 wherein the at least one positioning
constraint comprises one or more axes of movement of the
representation of the second implant component based on the
representation of the first implant component.
5. The method of claim 4 wherein an axis from the one or more axes
constrains a critical area between the representation of the first
implant component and the representation of the second implant
component.
6. The method of claim 4 wherein an axis from the one or more axes
constrains a distance between the representation of the first
implant component and the representation of the second implant
component.
7. The method of claim 4 wherein an axis from the one or more axes
is based on an arc between the representation of the first implant
component and the representation of the second implant
component.
8. The method of claim 4 wherein preventing comprises preventing a
movement of the representation of the second component that is not
a rotation around the one or more axes, a translation along the one
or more axes, or any combination thereof.
9. The method of claim 4 further comprising displaying a
cross-sectional display at a cross-section point along an axis from
the one or more axes, wherein the cross-sectional display comprises
the representation of the first implant component, the
representation of the second implant component, the representation
of the bone, or any combination thereof.
10. The method of claim 9 further comprising updating the
cross-sectional display based on a new cross-section point along
the axis.
11. The method of claim 1 wherein the at least one positioning
constraint is based on a representation of an extension of an
articular surface of at least one of the first implant component
and the second implant component.
12. The method of claim 11 further comprising determining an
overlap of the representation of the extension of the articular
surface and the representation of the first implant component, the
representation of the second implant component, or any combination
thereof.
13. The method of claim 11 further comprising displaying the
representation of the extension of the articular surface.
14. The method of claim 1 wherein displaying the representation of
the second implant component comprises displaying the
representation of the second implant component with respect to the
representation of the bone.
15. The method of claim 14 wherein displaying the representation of
the second implant component with respect to the representation of
the bone further comprises displaying the representation of the
second implant component based on at least one of a coordinate
space of the representation of the bone or a coordinate space of
the representation of the first implant component.
16. The method of claim 1 further comprising displaying a change
indicator, wherein the change indicator is based on a current
location of the representation of the first implant component and
at least one of an original location of the representation of the
first implant component, a coordinate space of the representation
of the bone, a coordinate space of the representation of the first
implant component, or a coordinate space of a representation of
cartilage.
17. A surgical planning computerized method comprising: displaying
a representation of a bone and a representation of a first implant
component with respect to the representation of the bone; receiving
data associated with a positioning of a representation of a second
implant component, wherein the first implant component and the
second implant component are physically separated and not connected
to each other; comparing the data associated with the positioning
of the representation of the second implant component with a
positioning constraint that is based on the representation of the
bone, the representation of the first implant component, or both;
and displaying the representation of the second implant component
in accord with the data associated with the positioning of the
representation of the second implant component if the data meets
the positioning constraint.
18. A surgical planning system comprising: a computer configured
to: generate a display of a representation of a bone and a
representation of a first implant component with respect to the
representation of the bone; generate a display of a representation
of a second implant component, wherein the first implant component
and the second implant component are physically separated and not
connected to each other; and prevent a positioning of the
representation of the second implant component that violates at
least one positioning constraint, wherein the positioning
constraint is based on the representation of the first implant
component.
19. The surgical planning system of claim 18 further comprising
receiving data associated with a positioning of the representation
of the second implant component.
20. The surgical planning system of claim 18 wherein the computer
is further configured to generate a user interface that enables a
positioning of either the representation of the first implant
component, the representation of the second implant component, or
any combination thereof.
21. The surgical planning system of claim 18 wherein the computer
is further configured to: calculate a plurality of areas
representing cartilage; and adjust a positioning of at least one of
the representation of the first implant component and the
representation of the second implant component based on at least
one of the plurality of areas representing cartilage.
22. A computer program product, tangibly embodied in a computer
readable medium, the computer program product including
instructions being operable to cause a data processing apparatus
to: display a representation of a bone and a representation of a
first implant component with respect to the representation of the
bone; display a representation of a second implant component,
wherein the first implant component and the second implant
component are physically separated and not connected to each other;
and prevent a positioning of the representation of the second
implant component that violates at least one positioning
constraint, wherein the positioning constraint is based on the
representation of the first implant component.
23. A system comprising: displaying a representation of a bone and
a representation of a first implant component with respect to the
representation of the bone; displaying a representation of a second
implant component, wherein the first implant component and the
second implant component are physically separated and not connected
to each other; and means for preventing a positioning of the
representation of the second implant component that violates at
least one positioning constraint, wherein the positioning
constraint is based on the representation of the first implant
component.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to surgical computer
systems, including computer program products, and methods for
implant planning for multiple implant components, particularly to
multiple component implant constraints.
BACKGROUND
[0002] Orthopedic joint replacement surgery may involve
arthroplasty of a knee, hip, or other joint (e.g., shoulder, elbow,
wrist, ankle, fingers, etc.). For example, traditional total knee
arthroplasty (TKA) involves a long incision, typically in a range
of about 6 to 12 inches, to expose the joint for bone preparation
and implantation of implant components. The invasive nature of the
incision results in a lengthy recovery time for the patient.
Minimally invasive surgery (MIS) reduces the incision length for a
total knee replacement surgery to a range of about 4 to 6 inches.
However, the smaller incision size reduces a surgeon's ability to
view and access the anatomy of a joint. Consequently, the
complexity of assessing proper implant position and reshaping bone
increases, and accurate placement of implants may be more
difficult. Inaccurate positioning of implants compromises joint
performance. For example, one problem with TKA is that one or more
components of the implant may improperly contact the patella, which
may be caused by inaccurate positioning of the one or more implant
components within the knee.
[0003] An important aspect of implant planning concerns variations
in individual anatomies. As a result of anatomical variation, there
is no single implant design or orientation of implant components
that provides an optimal solution for all patients. Conventional
TKA systems typically include a femoral component that is implanted
on the distal end of the femur, a tibial component that is
implanted on the proximal end of the tibia, and a patellar
component that replaces the articular surface of the patella. As
mentioned above, conventional TKA systems require an incision large
enough to accept implantation of the femoral and tibial components.
Further, the femoral and tibial components have standard, fixed
geometries and are only available in a limited range of sizes. As a
result, the surgeon may be unable to achieve a fit that addresses
each patient's unique anatomy, ligament stability, and
kinematics.
[0004] Modular TKA knee prostheses comprising multiple components
that are inserted separately and assembled within the surgical site
have been developed to overcome conventional TKA systems. Some
modular TKA system implementations mimic a conventional TKA system
by allowing the multiple components to be inserted separately so
the components can be connected together inside the patient's body.
One disadvantage is that the modular components, once assembled
inside the patient's body, mimic a conventional TKA system and thus
suffer from similar limitations. Once the modular components are
fixed together, the components are dependent upon one another. Such
implant systems do not enable the surgeon to vary the placement or
geometry of each modular component to best suit each patient's
unique anatomy, ligament stability, kinematics, and disease
state.
[0005] Some modular TKA system implementations allow the implant
components to be positioned independently of one another. An
example of independent component placement systems and methods is
described in U.S. patent application Ser. No. 11/684,514, filed
Mar. 9, 2007, published as Pub. No. 2008/0058945, and hereby
incorporated by reference herein in its entirety. One disadvantage
of such systems is the determination of the placement of each
implant component is not constrained based on the other implant
components. Multiple component implant systems, however, often
require that a number of relative constraints between the
components be satisfied so that the implant system functions
properly. If all implants are planned independently, it is nearly
impossible to satisfy all the necessary constraints. For example,
in order to have a smooth transition between the femoral condyle
implant and the patella implant, the relative position of the two
implants to each other is critical.
[0006] Further, proper placement of the implant components on the
femur and tibia require knowledge of the articular cartilage
surfaces of each bone. Articular cartilage is an avascular soft
tissue that covers the articulating bony ends of joints. During
joint motion, cartilage acts as a lubricating mechanism in the
articulating joints and protects the underlying bony structure by
minimizing peak contact force at the joint. A model of each bone
can be generated from a CT scan of the bone to allow models of the
implant components to be positioned relative to the bone models to
plan for the surgery. However, CT scans may not accurately
determine the articular cartilage surface of the bone. As a result,
the planned placement of the implant components match only the
surface of the bone and not the cartilage, while the surface of the
cartilage frequently determines the optimal placement of the
implant. Cartilage surfaces can be determined by capturing the tip
positions of a tracked probe while the probe is dragged over the
cartilage surface. However, this requires that each point is
captured to draw the cartilage surface, which is a timely and
computationally involved procedure.
[0007] In view of the foregoing, a need exists for surgical methods
and devices which can overcome the aforementioned problems so as to
enable intraoperative implant planning for accurate placement and
implantation of multiple joint implant components providing
improved joint performance; consistent, predictable operative
results regardless of surgical skill level; sparing healthy bone in
minimally invasive surgery; achieving a fit of the implant
components that address each patient's unique anatomy, ligament
stability, and kinematics; and reducing the need for replacement
and revision surgery.
SUMMARY OF THE INVENTION
[0008] The techniques described herein provide methods,
apparatuses, and computer program products for implant planning for
multiple implant components using constraints and implant planning
using areas representing cartilage. Such implant planning
facilitates the accurate placement of implant components of a
multiple component implant to fit the unique anatomy of a
patient.
[0009] In one aspect there is a method. The method is a surgical
planning computerized method for displaying a representation of a
bone and a representation of a first implant component with respect
to the representation of the bone. The method also includes
displaying a representation of a second implant component, wherein
the first implant component and the second implant component are
physically separated and not connected to each other. The method
also includes preventing a positioning of the representation of the
second implant component that violates at least one positioning
constraint, wherein the positioning constraint is based on the
representation of the first implant component.
[0010] In another aspect, there is a method. The method is a
surgical planning computerized method for displaying a
representation of a bone and a representation of a first implant
component with respect to the representation of the bone. The
method also includes receiving data associated with a positioning
of a representation of a second implant component, wherein the
first implant component and the second implant component are
physically separated and not connected to each other. The method
also includes comparing the data associated with the positioning of
the representation of the second implant component with a
positioning constraint that is based on the representation of the
bone, the representation of the first implant component, or both.
The method also includes displaying the representation of the
second implant component in accord with the data associated with
the positioning of the representation of the second implant
component if the data meets the positioning constraint.
[0011] In another aspect, there is a system. The system is a
surgical planning system including a computer configured to
generate a display of a representation of a bone and a
representation of a first implant component with respect to the
representation of the bone. The computer is also configured to
generate a display of a representation of a second implant
component, wherein the first implant component and the second
implant component are physically separated and not connected to
each other. The computer is also configured to prevent a
positioning of the representation of the second implant component
that violates at least one positioning constraint, wherein the
positioning constraint is based on the representation of the first
implant component.
[0012] In another aspect, there is a computer program product. The
computer program product is tangibly embodied in a computer
readable medium. The computer program product includes instructions
being operable to cause a data processing apparatus to display a
representation of a bone and a representation of a first implant
component with respect to the representation of the bone. The
instructions are also operable to cause a data processing apparatus
to display a representation of a second implant component, wherein
the first implant component and the second implant component are
physically separated and not connected to each other. The
instructions are also operable to cause a data processing apparatus
to prevent a positioning of the representation of the second
implant component that violates at least one positioning
constraint, wherein the positioning constraint is based on the
representation of the first implant component.
[0013] In another aspect, there is a system. The system includes
displaying a representation of a bone and a representation of a
first implant component with respect to the representation of the
bone. The system also includes displaying a representation of a
second implant component, wherein the first implant component and
the second implant component are physically separated and not
connected to each other. The system also includes means for
preventing a positioning of the representation of the second
implant component that violates at least one positioning
constraint, wherein the positioning constraint is based on the
representation of the first implant component.
[0014] In another aspect, there is a method. The method is a
surgical planning computerized method for determining a
predetermined number of control points for generating a
predetermined number of areas representing cartilage, wherein the
predetermined number of control points are based on an implant
component. The method also includes receiving measurements
corresponding to a plurality of measured cartilage points, wherein
each cartilage point is based on an associated control point from
the predetermined number of control points. The method also
includes generating a plurality of areas representing cartilage,
wherein each area representing cartilage is larger than and
projects to an associated control point from the plurality of
control points. The method also includes positioning a
representation of the implant component based on a representation
of a bone, the representation of the bone comprising
representations of the plurality of areas representing
cartilage.
[0015] In another aspect, there is a system. The system is a
surgical planning system including a computer configured to
determine a predetermined number of control points for generating a
predetermined number of areas representing cartilage, wherein the
predetermined number of control points are based on an implant
component. The computer is further configured to generate a
plurality of areas representing cartilage, wherein each area
representing cartilage is larger than and projects to an associated
control point from a plurality of control points. The computer is
further configured to position a representation of the implant
component based on a representation of a bone, the representation
of the bone comprising the plurality of areas representing
cartilage. The system also includes a probe configured to measure
the plurality of cartilage points, wherein each cartilage point is
based on an associated control point from the predetermined number
of control points.
[0016] In another aspect, there is a computer program product. The
computer program product is tangibly embodied in a computer
readable medium. The computer program product includes instructions
being operable to cause a data processing apparatus to determine a
predetermined number of control points for generating a
predetermined number of areas representing cartilage, wherein the
predetermined number of control points are based on an implant
component. The computer program product also includes instructions
being operable to cause a data processing apparatus to receive
measurements corresponding to a plurality of measured cartilage
points, wherein each cartilage point is based on an associated
control point from the predetermined number of control points. The
computer program product also includes instructions being operable
to cause a data processing apparatus to generate a plurality of
areas representing cartilage, wherein each area representing
cartilage is larger than and projects to an associated control
point from the plurality of control points. The computer program
product includes instructions being operable to cause a data
processing apparatus to position a representation of the implant
component based on a representation of a bone, the representation
of the bone comprising representations of the plurality of areas
representing cartilage.
[0017] In another aspect, there is a system. The system includes
means for determining a predetermined number of control points for
generating a predetermined number of areas representing cartilage,
wherein the predetermined number of control points are based on an
implant component. The system also includes means for receiving
measurements corresponding to a plurality of measured cartilage
points, wherein each cartilage point is based on an associated
control point from the predetermined number of control points. The
system also includes means for generating a plurality of areas
representing cartilage, wherein each area representing cartilage is
larger than and projects to an associated control point from the
plurality of control points. The system also includes means for
positioning a representation of the implant component based on a
representation of a bone, the representation of the bone comprising
representations of the plurality of areas representing
cartilage.
[0018] In other examples, any of the aspects above can include one
or more of the following features. A plurality of areas
representing cartilage can be calculated, and a positioning of the
representation of the first implant component that violates a
second positioning constraint that is based on the plurality of
areas representing cartilage can be prevented. The at least one
positioning constraint can include a rigid constraint between the
representation of the first implant component and the
representation of the second implant component, wherein the rigid
constraint prevents a positioning of the representation of the
second implant component that is independent of the representation
of the first implant component.
[0019] In some examples, the at least one positioning constraint
comprises one or more axes of movement of the representation of the
second implant component based on the representation of the first
implant component. An axis from the one or more axes can constrain
a critical area between the representation of the first implant
component and the representation of the second implant component.
An axis from the one or more axes can constrain a distance between
the representation of the first implant component and the
representation of the second implant component. An axis from the
one or more axes can be based on an arc between the representation
of the first implant component and the representation of the second
implant component.
[0020] In other examples, preventing comprises preventing a
movement of the representation of the second component that is not
a rotation around the one or more axes, a translation along the one
or more axes, or any combination thereof. A cross-sectional display
can be displayed at a cross-section point along an axis from the
one or more axes, wherein the cross-sectional display comprises the
representation of the first implant component, the representation
of the second implant component, the representation of the bone, or
any combination thereof. The cross-sectional display can be updated
based on a new cross-section point along the axis.
[0021] In some examples, the at least one positioning constraint is
based on a representation of an extension of an articular surface
of at least one of the first implant component and the second
implant component. An overlap of the representation of the
extension of the articular surface and the representation of the
first implant component, the representation of the second implant
component, or any combination thereof can be determined. The
representation of the extension of the articular surface can be
displayed. Displaying the representation of the second implant
component can include displaying the representation of the second
implant component with respect to the representation of the
bone.
[0022] In other examples, displaying the representation of the
second implant component with respect to the representation of the
bone further comprises displaying the representation of the second
implant component based on at least one of a coordinate space of
the representation of the bone or a coordinate space of the
representation of the first implant component. A change indicator
can be displayed, wherein the change indicator is based on a
current location of the representation of the first implant
component and at least one of an original location of the
representation of the first implant component, a coordinate space
of the representation of the bone, a coordinate space of the
representation of the first implant component, or a coordinate
space of a representation of cartilage. Data associated with a
positioning of the representation of the second implant component
can be received.
[0023] In some examples, the computer is further configured to
generate a user interface that enables a positioning of either the
representation of the first implant component, the representation
of the second implant component, or any combination thereof. The
computer can be further configured to calculate a plurality of
areas representing cartilage and to adjust a positioning of at
least one of the representation of the first implant component and
the representation of the second implant component based on at
least one of the plurality of areas representing cartilage. The
representation of the implant component can be automatically
aligned to fit the plurality of areas representing cartilage.
[0024] In other examples, generating the plurality of areas
representing cartilage includes transforming the predetermined
number of control points to a coordinate space of the
representation of the bone and transforming the plurality of
cartilage points to the coordinate space of the representation of
the bone. Generating the plurality of areas representing cartilage
can include, for each area representing cartilage from the
plurality of areas, calculating a distance between a point of the
representation of the bone and an associated transformed cartilage
point, calculating a direction between a closest point of the
representation of the bone to an associated transformed control
point, determining a plurality of points of the representation of
the bone that are within a second distance from the associated
transformed control point, and adjusting the plurality of points
based on the second distance and direction to form the plurality of
areas representing cartilage.
[0025] In some examples, each of the plurality of points of the
representation of the bone corresponds to a set of polygons from a
superset of polygons, the representation of the bone comprising the
superset of polygons. Adjusting can include adjusting a vertex of
each polygon from the set of polygons. The superset of polygons can
include triangles. Calculating the distance between the point of
the representation of the bone and the associated transformed
cartilage point can include selecting a closest point of the
representation of the bone to the associated transformed cartilage
point.
[0026] In other examples, for each area representing cartilage of
the plurality of areas representing cartilage, registering a
control point from the transformed predetermined number of control
points to a closest point in the area representing cartilage. The
registered control point can be constrained to automatically adjust
a position of the representation of the implant component. The
representation of the bone can be displayed, and the representation
of the implant component with respect to the representation of the
bone can be displayed. A representation of a second implant
component can be displayed, wherein the implant component and the
second implant component are components of a multiple component
implant. The method can include determining if a positioning of the
representation of the second implant component violates at least
one positioning constraint.
[0027] In some examples, the at least one positioning constraint is
based on the representation of the bone, the representation of the
implant component, or any combination thereof. The computer can be
further configured to generate a display of a second implant
component, wherein the implant component and second implant
component are components of a multiple component implant. The
computer can be further configured to determine if a positioning of
the representation of the second implant component violates at
least one positioning constraint. The at least one positioning
constraint can be based on the representation of the bone, the
representation of the implant component, or both. The computer can
be further configured to generate a user interface that enables a
positioning of either the representation of the implant component,
the representation of the second implant component, or any
combination thereof.
[0028] The techniques for implant planning for multiple implant
components using constraints and implant planning using areas
representing cartilage described herein can provide one or more of
the following advantages. Since each patient's anatomy is unique,
having multiple sizes and shapes for the implant components and
constraining the positioning of the components with respect to
other components and/or the bone allows the system to find a best
fit for each patient. The constraints provide information on
positioning the components accurately and effectively, preventing
improper placement, and enabling the multiple components of the
implant to work with each other as they were designed to do so.
Multiple types of visual displays further enhance proper placement
of the implant components. Further, implant components can be
adjusted to account for cartilage representations. A more
effective, less intrusive implant planning procedure can be
achieved for each individual patient. Implant planning using
constraints allows the placement of components that are physically
separated and not touching to be optimally placed within a
patient's anatomy at locations which ensure the components operate
as designed. Optimal positioning of smaller, separate components
allows for smaller incisions (e.g., due to the smaller components)
and less invasive surgeries.
[0029] Other aspects and advantages of the present invention will
become apparent from the following detailed description, taken in
conjunction with the accompanying drawings, illustrating the
principles of the invention by way of example only.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The foregoing and other objects, features, and advantages of
the present invention, as well as the invention itself, will be
more fully understood from the following description of various
embodiments, when read together with the accompanying drawings.
[0031] FIG. 1 illustrates an exemplary multiple component implant
planning system according to the present invention;
[0032] FIG. 2 is a perspective view of a femur and representations
of components of an exemplary multiple component implant as
presented by the display of FIG. 1;
[0033] FIG. 3 illustrates an exemplary method for implant planning
with constraints for components of a multiple component
implant;
[0034] FIG. 4A illustrates a prospective display including
constraints for representations of components of a multiple
component implant;
[0035] FIG. 4B illustrates a cross-sectional display along a
constraint axis including representations of components of a
multiple component implant;
[0036] FIG. 5 illustrates a split display including constraints for
representations of components of a multiple component implant;
[0037] FIG. 6 illustrates a split display including cartilage areas
along a representation of a bone;
[0038] FIG. 7 illustrates an exemplary method for positioning an
implant component based on areas representing cartilage;
[0039] FIG. 8 illustrates an exemplary method for estimating areas
representing cartilage;
[0040] FIGS. 9A-9D illustrate bone points on a femur for implant
planning;
[0041] FIGS. 10A-10C illustrate implant points on implant
components of a multiple component implant for implant
planning;
[0042] FIGS. 11A-11C illustrate implant component axes relative to
implant components of a multiple component implant for implant
planning; and
[0043] FIG. 12 shows an embodiment of an exemplary surgical
computer system for implant planning using constraints and/or areas
representing cartilage.
DETAILED DESCRIPTION
[0044] Presently preferred embodiments are illustrated in the
drawings. Although this specification refers primarily to knee
joint replacement surgery, it should be understood that the subject
matter described herein is applicable to other joints in the body,
such as, for example, a shoulder, elbow, wrist, spine, hip, or
ankle and to any other orthopedic and/or musculoskeletal implant,
including implants of conventional materials and more exotic
implants, such as orthobiologics, drug delivery implants, and cell
delivery implants.
[0045] In general overview, multiple component implant planning is
achieved by constraining the adjustment of the individual
components of the multiple component implant. Each component can be
adjusted based on the constraints, allowing a proper fit for each
implant component while preventing improper placement. FIG. 1
illustrates an exemplary multiple component implant planning system
100 according to the present invention. The system includes
computer 102. Computer 102 is in communication with input unit 104.
Input unit 104 is in communication with probe 106. Computer 102 is
further in communication with display 108.
[0046] The computer 102 may be any known computing system but is
preferably a programmable, processor-based system. For example, the
computer 102 may include a microprocessor, a hard drive, random
access memory (RAM), read only memory (ROM), input/output (I/O)
circuitry, and any other well-known computer component. The
computer 102 is preferably adapted for use with various types of
storage devices (persistent and removable), such as, for example, a
portable drive, magnetic storage (e.g., a floppy disk), solid state
storage (e.g., a flash memory card), optical storage (e.g., a
compact disc or CD), and/or network/Internet storage. The computer
102 may comprise one or more computers, including, for example, a
personal computer (e.g., an IBM-PC compatible computer) or a
workstation (e.g., a SUN or Silicon Graphics workstation) operating
under a Windows, MS-DOS, UNIX, or other suitable operating system
and preferably includes a graphical user interface (GUI).
[0047] The input unit 104 enables information to be communicated to
the implant planning system 100. For example, the input unit 104
provides an interface for a user to communicate with the implant
planning system. The terms user and operator both refer to a person
using the implant planning system 100 and are sometimes used
interchangeably. The input unit 104 is connected to the computer
102 and may include any device enabling a user to provide input to
a computer. For example, the input unit 104 can include a known
input device, such as a keyboard, a mouse, a trackball, a touch
screen, a touch pad, voice recognition hardware, dials, switches,
buttons, a trackable probe, a foot pedal, a remote control device,
a scanner, a camera, a microphone, and/or a joystick. The input
unit 104 may also include surgical navigation equipment that
provides data to the computer 102. For example, the input unit 104
can include a tracking system for tracking the position of surgical
tools and patient anatomy. The tracking system may be, for example,
an optical, electromagnetic, radio, acoustic, mechanical, or fiber
optic tracking system.
[0048] The probe 106 may be any probe for measuring the thickness
of articular cartilage. An example of a probe is U.S. Pat. No.
6,585,666 ("the '666 patent"), filed Jul. 30, 2001, and
incorporated by reference herein in its entirety. The '666 patent
discloses a diagnostic probe which determines the thickness of
articular cartilage as a function of the true ultrasound speed of
the cartilage. The probe 106 may also be a tracked probe, where tip
positions of the probe are captured (e.g., by an optical camera,
joint encoders, etc.) when the probe tip is touched to the
cartilage surface. Because the patient's bones are in registration
with bone models (created, for example, from CT scans of the
bones), the captured tip positions can be compared to the known
location of the bone surface to estimate the thickness of the
cartilage. The tracked probe may be, for example, a probe having
optical markers affixed thereto or an end effector of an
articulated or robotic arm.
[0049] The probe 106 is in operative communication with the
computer 102. For example, the probe 106 may be coupled to the
computer 102 via an interface (not shown). The interface can
include a physical interface and/or a software interface. The
physical interface may be any known interface such as, for example,
a wired interface (e.g., serial, USB, Ethernet, CAN bus, and/or
other cable communication interface) and/or a wireless interface
(e.g., wireless Ethernet, wireless serial, infrared, and/or other
wireless communication system). The software interface may be
resident on the computer 102. For example, in the case of a tracked
probe that includes optical markers, probe tip position data is
captured and relayed to the computer 102 by an optical camera.
[0050] The display 108 is a visual interface between the computer
102 and the user. The display 108 is connected to the computer 102
and may be any device suitable for displaying text, images,
graphics, and/or other visual output. For example, the display 108
may include a standard display screen (e.g., LCD, CRT, plasma,
etc.), a touch screen, a wearable display (e.g., eyewear such as
glasses or goggles), a projection display, a head-mounted display,
a holographic display, and/or any other visual output device. The
display 108 may be disposed on or near the computer 102 (e.g.,
mounted within a cabinet also comprising the computer 102) or may
be remote from the computer 102 (e.g., mounted on a wall of an
operating room or other location suitable for viewing by the user).
The display 108 is preferably adjustable so that the user can
position/reposition the display 108 as needed during a surgical
procedure. For example, the display 108 may be disposed on an
adjustable arm (not shown) or on any other location well-suited for
ease of viewing by the user. The display 108 may be used to display
any information useful for a medical procedure, such as, for
example, images of anatomy generated from an image data set
obtained using conventional imaging techniques, graphical models
(e.g., CAD models of implants, instruments, anatomy, etc.),
graphical representations of a tracked object (e.g., anatomy,
tools, implants, etc.), digital or video images, registration
information, calibration information, patient data, user data,
measurement data, software menus, selection buttons, status
information, and the like. The terms model and representation can
be used interchangeably to refer to any computerized display of a
component (e.g., implant, bone, tissue, etc.) of interest.
[0051] In some embodiments, the display 108 displays graphical
representations of the bones associated with a joint of interest
(e.g., the femur and tibia of a knee joint). The display 108 can
further display graphical representations of one or more components
of a multiple component implant. FIG. 2 is a perspective view 150
of a representation of a femur 152 and representations of
components of an exemplary multiple component implant as presented
by the display 108 of FIG. 1. The representation of the multiple
component implant includes a central patello-femoral implant
component 154 and a medial implant component 156. The
representation of the multiple component implant may further
include a lateral implant component 158. The display 108 can allow
a user to position one or more of the implant component
representations (e.g., the patello-femoral implant component 154,
the medial implant component 156, and/or the lateral implant
component 158). The positioning of the representations of the
implant components can be based on constraints, as will be
discussed further below. The representations of components and/or
bones can be semi-transparent to demonstrate the relationship among
the components and/or bones. For example, in FIG. 2, the
representation of the femur 152 is semi-transparent so the portions
of both the medial implant component 156 and the lateral implant
component 158 located under the representation of the femur 152,
which would normally be hidden, can be viewed by a user of the
implant planning system 100.
[0052] The components of the multiple component implant are
preferably segmented components. As shown in FIG. 2, a segmented
component is an individual component implanted on the bone as an
independent, self-contained, stand-alone component that is not
physically constrained by any other component of the multiple
component implant (as used herein, the term physically constrained
means that the components are linked through a physical connection
and/or physical contact in such a manner that the link between the
components imposes limitations on the positioning or placement of
either of the components). Thus, the representation of the
patello-femoral implant component 154, the representation of the
medial implant component 156, and the representation of the lateral
implant component 158 are all segmented components. To ensure that
a segmented component is not physically constrained by other
components, the segmented component may be implanted in the joint
so that the component is not connected to and/or in contact with
any other segmented component.
[0053] For example, the components of the multiple component
implant are configured such that the components can be implanted on
a patient's femur without being connected, as shown in FIG. 2.
While FIG. 2 shows a graphical representation of both the implant
components and the bone, the representations of the implant
components and the bone are indicative of the actual implantation
of the implant components on a patient's bone as represented by
FIG. 2. For example, for perspective view 150, the representation
of the patello-femoral implant component 154, the representation of
the medial implant component 156, and the representation of the
lateral implant component 158 are not interconnected when fixed
relative to the representation of the femur 152. Similarly, during
the actual implant procedure for the implant components, the
patello-femoral implant component, the medial implant component,
and the lateral implant component are not interconnected when fixed
relative to the patient's femur. Providing perspective view 150
(e.g., through display 108 of the implant planning system 100)
advantageously allows a user to plan the implant procedure before a
patient surgery to maximize the effectiveness of the implant while
minimizing the invasiveness of the surgery to the patient.
[0054] For example, the system of three implant components (e.g.,
components 154, 156, and 158) can be rotated and translated as one
rigidly attached system to an initial location in the joint. The
initial location can match the representation of the implant to the
representation of one or more bones and/or the representation of
the cartilage surface on the one or more bones. For example, FIG. 2
shows the representations of the three implant components aligned
on the representation of the femur 152. Once the overall location
and orientation have been set, individual components (e.g., the
medial implant component 156) can be rotated around one or more
predefined axes. The axes can be defined, for example, in the
coordinate space of a reference component representation, the
representation of the bone, or any other displayed representation
(e.g., the axes can be defined in the coordinate space of the
central patello-femoral implant component 154).
[0055] In some embodiments the graphical displays are configured to
provide for easy identification of different items within the
display. Items can be visually distinguished from other items in
the display through visual aids, such as color-coding, hatching,
and shading. In some embodiments, all the representations of
components of a multiple component implant are displayed with the
same visual aid. In some embodiments, the representation of the
bone and each implant component representation is displayed with a
unique visual aid to facilitate easy identification of the implant
component and the bone representations.
[0056] The graphical displays are used to provide the user with a
simulation of positioning the implant components on a patient's
anatomy preoperatively. The bone representation and implant
component representations can be generated to the scale of the true
component/bone relative sizes and shapes. Advantageously, the
implant component representations can be positioned (e.g., by an
operator) on the bone representation, and the bone representation
can be moved to mimic actual position changes of the bone that
would occur post-operatively as the joint moves through a range of
motion, as described, for example, in U.S. patent application Ser.
No. 11/963,547, filed Dec. 21, 2007, and hereby incorporated by
reference herein in its entirety. An operator can then adjust the
implant component representations to find an optimal positioning of
the implant components along the bone prior to surgery.
[0057] FIG. 3 illustrates an exemplary method 200 for implant
planning with constraints for components of a multiple component
implant, which will be explained with reference to FIG. 2. The
system (e.g., the implant planning system 100 of FIG. 1) displays
(202) a representation of a bone (e.g., on display 108). For
example, the system displays a three-dimensional representation of
the femur 152 (i.e., a three-dimensional graphical model of a
patient's bone). The displayed bone representation can also be a
two-dimensional representation. For example, the bone
representation can be a cross-sectional representation of the bone.
The graphical model of the bone may be generated in various ways.
For example, as described in U.S. patent application Ser. No.
12/147,997, filed Jun. 27, 2008, and hereby incorporated by
reference herein in its entirety, multiple sequential images of a
patient's anatomy are segmented to discern the outline of the
anatomy and propagated to adjacent images to generate a
three-dimensional model of the patient's anatomy. Alternatively,
for 3D imageless planning, bone atlases may be used to obtain the
3D bone models. A bone atlas is a statistical model that represents
the relevant anatomy, including information on natural variations
typically existing in specific populations with specific
distributions and probabilities. Using known image processing
techniques and statistical data, the bone atlas may be transformed
or "morphed" to find a best fit to the patient's anatomy based on
demographic information, such as gender, age, stage of disease, and
other patient-specific characteristics. Additionally, although
preoperative planning can be accomplished using the initial bone
atlas model, once intra-operative registration data on the actual
physical bones is obtained, the bone atlas can be further morphed
to improve the fit to the patient's anatomy along with
corresponding adjustments to the implant plan. The system displays
(204) a representation of at least a first implant component with
respect to the bone. For example, the system displays the central
patello-femoral implant component 154 with respect to the
representation of the femur 152. The system and/or operator can
position the implant component representation with respect to a
base planning coordinate space. The base planning coordinate space
can be, for example, the coordinate space of the representation of
the bone. For CT image-based bone models, this corresponds to the
coordinate space of the CT scan of the patient's bone. Positioning
by the operator can be accomplished using any input means (e.g.,
input unit 104, a keyboard, mouse, touch screen display, and/or the
like).
[0058] The representation of an implant component can be a
two-dimensional and/or a three-dimensional model. The model can be
stored on the implant planning system 100. There can be multiple
models for each component to represent implant component systems of
various sizes and shapes. Advantageously, since each patient's
anatomy is unique, having multiple sizes and shapes for the implant
components allows the system to find a best fit for each patient
(e.g., based on bone shape and size, joint movement, cartilage
depth, and other physical characteristics unique to the patient).
For example, depending on the representation of the bone, the
system and/or operator can choose a component system from a
plurality of component systems that best fits the representation of
the bone.
[0059] The system 100 displays (206) a representation of a second
implant component. For example, the system 100 displays medial
implant component 156. The system 100 receives (208) data
associated with a positioning of a representation of the second
implant component. For example, an operator can use the implant
planning system 100 to adjust the multiple component
representations during an implant planning procedure to optimize
component placement for a patient. The operator can, for example,
reposition the medial implant component 156. The operator can
reposition the medial implant component 156 using any input means
(e.g., input unit 104, a keyboard, mouse, touch screen display,
and/or the like). In some embodiments, steps 204 and 206 occur
simultaneously. For example, the system displays the
representations of the first and second implants, and the system
and/or operator can position the implant component representations
with respect to the base planning coordinate space. For example,
the operator can rotate and/or translate the multiple implant
components as one rigidly attached system to an initial location
relative to the representation of the bone.
[0060] The system 100 determines (210) if the positioning of the
representation of the second component violates at least one
positioning constraint. Positioning constraints (see, e.g., FIG.
4A) allow an operator to move component representations within
certain limits to ensure, for example, the components operate
properly, are non-intrusive to the patient's anatomy, and are
positioned correctly. Constraints can be associated with points,
axes, lines, volumes, and/or other constraints. For example,
constraints prevent an operator from positioning a component
representation in an improper location. If the system 100
determines the positioning of the representation of the second
component violates a positioning constraint, the system 100
prevents (212) the positioning of the second implant component
(e.g., the representation of the component on the display will not
move as requested by the input of the operator). If the system 100
determines the positioning does not violate the positioning
constraint, the system 100 allows (214) the new positioning. The
system 100 can update the display to reflect the new positioning of
the second implant component. In cases where the system 100
prevents the positioning of the second implant, the system 100 can
optionally provide an error message to the operator indicating why
the second implant cannot be moved to the desired position.
[0061] FIG. 4A illustrates a display 250 including constraints for
representations of components of a multiple component implant. The
display 250 includes the representation of the femur 152, the
representation of the patello-femoral implant component 154, and
the representation of the medial implant component 156. The display
250 includes three constraint axes, axes 252, 254, and 256. The
constraints can be visually distinguished from other items in the
display through visual aids, such as color-coding, hatching, and
shading. While the display 250 includes three constraint axes, the
display 250 can include any number of constraint axes. Those
skilled in the art can appreciate that the constraints can be
applied to any component of the multiple component implant.
[0062] The constraint axes shown in FIG. 4A constrain the movement
of the medial implant component 156 relative to the axes. The
constraint axes can constrain the movement of the implant component
based on one or more other implant components, the representation
of the bone, or a representation of cartilage (see, e.g., FIGS.
3-7). For example, the constraint axes can constrain the movement
of the medial implant component 156 based on the patello-femoral
implant component 154 or the representation of the femur 152.
[0063] The constraints can be axes of rotation and/or translation
directions defined relative to any coordinate space (e.g., anatomic
bone or implant). In some embodiments, the constraint axes can be
transformed from the implant coordinate space into the base
planning coordinate space (e.g., the coordinate space of the
representation of the bone). For example, let [0064] C.sub.B=the
base planning coordinate space; [0065] C.sub.I1=the coordinate
space of a first (1) implant (I) component; [0066] C.sub.I2=the
coordinate space of a second (2) implant (I) component; [0067]
T.sub.I1=homogenous (rigid body) transformation matrix for the
transformation from the coordinate space of the first (1) implant
(I) component to the base planning coordinate space; and [0068]
T.sub.I2=homogenous (rigid body) transformation matrix for the
transformation from the coordinate space of the second (2) implant
(I) component to the base planning coordinate space.
[0069] The rigid body transformation matrices perform translations
while preserving Euclidean distances between coordinate locations.
Homogeneous coordinate transformation matrices operate on
four-dimensional homogenous coordinate vector representations of
traditional three-dimensional coordinate locations. Instead of
representing each point (x,y,z) in a three-dimensional space with a
single three-dimensional vector:
[ x y z ] Equation 1 ##EQU00001##
homogenous coordinates allow each point (x,y,z) to be represented
by any of an infinite number of four dimensional vectors, which
when multiplied by 1.0 results in the vector:
[ x y z 1.0 ] Equation 2 ##EQU00002##
The three-dimensional vector corresponding to any four-dimensional
vector can be computed by dividing the first three elements by the
fourth, and a four-dimensional vector corresponding to any
three-dimensional vector can be created by simply adding a fourth
element and setting it equal to one. Any three-dimensional linear
transformation (e.g., rotation, translation, skew, and scaling) can
be represented by a 4.times.4 homogenous coordinate transformation
matrix. For example, a translation can be represented by a
4.times.4 homogeneous coordinate transformation matrix:
[ 1 0 0 x s 0 1 0 y s 0 0 1 z s 0 0 0 1 ] Equation 3
##EQU00003##
where: [0070] x.sub.s=translation along the x-axis; [0071]
y.sub.s=translation along the y-axis; and [0072]
z.sub.x=translation along the z-axis.
[0073] Multiplying Equation 1 by Equation 2 provides a
transformation from a three-dimensional coordinate position (x,y,z)
to the three-dimensional coordinate position (x', y',z') as shown
below:
[ x ' y ' z ' 1.0 ] = [ 1 0 0 x s 0 1 0 y s 0 0 1 z s 0 0 0 1 ] * [
x y z 1.0 ] Equation 4 ##EQU00004##
[0074] The first implant component is positioned from C.sub.I1 to
C.sub.B using T.sub.I1. The second implant component is positioned
from C.sub.I2 to C.sub.B using T.sub.I2. To transform a point or
vector defining a constraint from C.sub.I1 to C.sub.I2 so that it
can be used to limit the motion of the second implant component
during planning, the point or vector is multiplied by the
homogeneous matrix, T.sub.I1(T.sub.I2.sup.-1), where
T.sub.12.sup.-1 is the inverse of T.sub.I2. In some examples, the
homogeneous matrices can be general transformations from one
coordinate space to another.
[0075] The representation of the medial implant component 156 can
be manipulated based on the constraint axes 252, 254, and 256. For
example, the medial implant component 156 can be rotated around the
constraint axes, translated along the constraint axes, and/or other
movements so that certain constraints (e.g., angles, distances,
degrees of rotation, and/or the like) are preserved between the
medial implant component 156 and a base object (e.g., the
representation of the femur 152 or the representation of the
patello-femoral implant component 154). For example, a constraint
axis can be defined as an axis which minimizes the effect of the
movement of the implant component with respect to a base object
(i.e., the representation of the femur 152 or the representation of
the patello-femoral implant component 154) for a known area that
has a substantial effect on the effectiveness of the overall
multiple component implant. By incorporating constraints into the
implant system 100, a user of the system 100 can freely position an
implant component relative to a patient's bone in a way that does
not compromise the effectiveness of the multiple component implant.
If the user attempts to position the implant component in a
location that could compromise the operation of the implant system,
the constraints automatically prevent such positioning of the
implant component. As such, the constraints act as an automatic
guide for the user, ensuring eventual placement of an implant
component that provides for a successful operation of the multiple
component implant system.
[0076] Any number of constraint axes can be used. A constraint axis
can be based on an arc between the representation of a first
implant component and a representation of a second implant
component. For example, if an implant component comprises an
arc-like shape (e.g., the representation of the medial implant
component 156 is shaped like an arc to properly fit the rounded
surface of the representation of the femur 152), constraints can be
based on the arc to preserve a distance between the implant
component and other implant components. For example, constraint
axis 252 can be based on the arc center of the representation of
the medial implant component 156.
[0077] A constraint axis can constrain a critical area between two
implant components (e.g., an area between the representation of the
first implant component patello-femoral implant component 154 and
the representation of the medial implant component 156). A critical
region can be a region associated with two implant components that
can have a large effect on the overall operability of the multiple
implant component when one or more components of the multiple
component implant are repositioned. For example, constraint axis
254 can be based on an area between the representation of the
patello-femoral implant component 154 and the representation of the
medial implant component 156 where the two implant components are
within a critical distance (e.g., within 3 mm from touching). Axis
254 would constrain movement of the implant components around the
critical area to ensure proper positioning.
[0078] A constraint axis can constrain a distance between a
representation of a first implant component and a representation of
a second implant component. For example, constraint axis 256 can be
selected as an axis between the representation of the
patello-femoral implant component 154 and the representation of the
medial implant component 156 so that movement along axis 256
preserves the distance between the representation of the
patello-femoral implant component 154 and the representation of the
medial implant component 156. The axes can also be constrained
based on the representation of the bone (e.g., the representation
of the femur 152), a representation of a cartilage area, and/or the
like. Translational movements of implant component representations
can also be constrained to two dimensions or an arbitrary plane.
For example, one constraint is facilitating translation only in the
coronal or x/z plane. Another exemplary translational constraint is
translation along an arbitrary curve in 3D space. Another exemplary
constraint is to anchor the implant component to a specific point.
For example, the specific point can be on or off the component, and
can be identified in the coordinate system of a second component.
For example, the implant can be "tied" to this specific point, but
otherwise left unconstrained. Other constraints can include
limiting the component to one or more motions within a defined
"bounding volume." For example, a two or three-dimensional shape or
area can represent the area within which a representation of an
implant component can be moved. Movements which attempt to move the
implant component outside of the shape or area can be prevented by
the system.
[0079] Advantageously, displaying the constraint axes provides an
operator (e.g., a surgeon) information on positioning the
components of a multiple component implant accurately and
effectively. For example, constraining the movement of the
representation of the medial implant component 156 along the three
constraint axes 252, 254, 256 prevents the operator from
inadvertently positioning the medial implant component in a
location which could be harmful to the patient's patella.
Constraints can be used to mirror factors related to the precise,
accurate, and functional placement of the components, allowing an
operator to safely reposition the location of an implant component
without jeopardizing the functionality of the implant. The operator
need not know about the factors, rather the factors are built into
the system 100 through constraints. The operator is automatically
prevented from moving the component in a way which violates the
constraints. This advantageously allows the multiple components to
be placed according to the patient's anatomy while still optimally
working with each other as designed, without the operator having to
know such details.
[0080] FIG. 4B illustrates a cross-sectional display 280 along a
constraint axis including representations of components of a
multiple component implant. The cross-sectional display 280 is a
cross-sectional view of FIG. 4A along constraint axis 252. As such,
the cross-sectional display 280 is at a location of the
three-dimensional display 250 so that the line representing
constraint axis 252 is perpendicular to display 280 (e.g., as if
the viewer is looking straight down constraint axis 252 so that
constraint axis 252 appears only as a point). Those skilled in the
art can appreciate that the cross-sectional display can be
generated about any point of the three-dimensional display 250.
[0081] The cross-sectional display 280 includes the representation
of the femur 152. Because of the location of the cross-sectional
display 280 with respect to the three-dimensional display 250, the
representation of the bone appears as two separate portions.
Subsequent cross-sectional images can be generated along, for
example, constraint axis 252 to portray the entire depth of the
representation of the bone along constraint axis 252. The
cross-sectional display 280 includes the representation of the
patello-femoral implant component 154 and the representation of the
medial implant component 156. The display 280 includes a portion of
the medial implant component 156A located within the representation
of the femur 152. This can be, for example, a portion of the
representation of the medial implant component 156 which protrudes
into the representation of the femur 152 during the operation to
affix the medial implant component to the femur (e.g., a post or
keel of the medial implant component). The cross-sectional display
280 includes an outline of the segmented bone surface 282. This
outline matches the surface which is displayed in the 3D view
(e.g., FIG. 4A). The outline of the segmented bone surface 282 can
be color-coded to facilitate easy identification (e.g., by a user).
For example, the outline of the segmented bone surface can be
colored red.
[0082] In some embodiments, to constrain the rotation of an implant
component around one axis (e.g., the representation of medial
implant component 156 about constraint axis 252), the
representation of the bone and of the implant can be displayed in
the cross-sectional display 280 along the constraint axis. Other
movements of the implant component of interest besides movements
for the implant component about the constraint axis (e.g.,
transformations, rotations, and/or the like along other constraint
axes) can be disabled for the implant component. The
cross-sectional display can be scrolled along the rotation axis,
while the center of rotation in the plane is fixed with respect to
the constraint axis. With respect to FIG. 4B, the medial implant
component 156 can be rotated around constraint axis 252, translated
along constraint axis 252, and/or any other movement in relation to
constraint axis 252. In some embodiments, another constraint is
that the range of each rotation can be limited. For example, the
medial implant component 156 can be constrained so it can be
rotated around constraint axis 252 within .+-.15.degree. from the
current location of the medial implant component.
[0083] An implant component can be constrained along more than one
axis. For example, to constrain the translation of the medial
implant component 156 along two axes (e.g., constraint axes 252 and
254), the representations of the bone and the implant component can
be displayed in a two-dimensional display in which the plane is
defined by the two axes. In some embodiments, the rotations can be
disabled. In some embodiments, the translation in each
two-dimensional display (e.g., each display based on two axes if
multiple axes are present) can be limited to one of the axis.
[0084] For any step of a surgical planning process, points, models
or/and surfaces can be displayed to facilitate the implant
component planning. Like constraint axes, these points and surfaces
can be defined in an arbitrary space (e.g., the coordinate space of
one of the implant components). FIG. 5 illustrates a split display
300 including constraints for representations of components of a
multiple component implant. The split display 300 includes a
three-dimensional display 302 and a two-dimensional display 304.
The display 300 includes an extension surface 306 and an extension
surface 308, which are representations of an extension of an
articular surface. For example, as shown in FIG. 5, the extension
surfaces 306 and 308 may each be a representation of an extension
of a portion of the articular surface of the patello-femoral
implant component 154. Advantageously, providing both the
three-dimensional display 302 and the two-dimensional display 304
with the extension surfaces 306, 308 can provide a user a reference
for the ideal placement of the implant component relative to the
base object (e.g., the representation of the medial component 156
(implant component) with respect to the representation of the
patello-femoral component 154 (base object)). In other examples,
the femur 152 can be the base object.
[0085] The three-dimensional display 302 includes the
representation of the femur 152. The three-dimensional display 302
includes the representation of the patello-femoral implant
component 154 and the representation of the medial implant
component 156. The three-dimensional display 302 includes the
extension surfaces 306, 308. The two-dimensional display 304
includes the representation of the femur 152. The two-dimensional
display 304 includes the representation of the patello-femoral
implant component 154 and the representation of the medial implant
component 156. The two-dimensional display 304 includes extension
surfaces 306, 308 and the outline of the segmented bone surface
282. This outline matches the surface which is displayed in the 3D
view. The two-dimensional display includes a slider 310 and a
change indicator 312. The two-dimensional display 304 is a
cross-sectional view of the three-dimensional display. The slider
310 can move the two-dimensional display 304 along an axis which is
perpendicular to the three-dimensional display 302 to represent
various 2D slices through the three-dimensional display 302. The
change indicator 312 can indicate the difference between the
coordinate system of a representation of an implant component with
reference to a base reference. The base reference can be, for
example, an initial position of the representation of the implant
component, a base coordinate system (e.g., the coordinate system of
the representation of the bone, the coordinate system of the
representation of a cartilage area), and any other reference point.
The change indicator can represent a degree of change from the base
reference, an angle of change from the base reference, a distance
from the base reference, and any other metric between the
representation of the implant component and the base reference. For
example, the change indicator 312 can display a degree of change
between the current location of the representation of the implant
component and an original representation of the implant
component.
[0086] The extension surfaces 306, 308 can be, for example,
three-dimensional shapes which are drawn between two implant
components indicative of the original placement of the two
components. For example, the extension surfaces 306, 308 can be the
surfaces which would connect the two implant components if the
implant components were a single component implant. Movements of
the implant components can be constrained by the extension surfaces
306, 308 based on the location of the implant components relative
to the extension surfaces 306, 308. As representations of the
implant components are adjusted in the implant planning system, the
extension surfaces 306, 308 remain fixed based on the original
placement location of the implant components prior to adjustment.
During adjustment of the implant components, the extension surfaces
306, 308 can be treated as transparent, allowing implant components
to "pass through" the extension surfaces 306, 308 if the component
is adjusted in a way that protrudes into the shape of the extension
surfaces 306, 308. For example, moving the representation of the
medial implant component 156 in one direction can cause the
representation of the medial implant component 156 to protrude into
the representation of extension surface 308. Similarly, moving the
representation of the medial implant component 156 can cause a gap
to form between the representation of extension surface 308 and the
representation of the medial implant component 156. The overlap of
the implant components and the extension surfaces 306, 308, the
distance between the implant components and the extension surfaces
306, 308, or both can be used to constrain the movement of the
implant components relative to the extension surfaces 306, 308.
Constraints can include limiting the overlap between a
representation of an implant component and one or more
corresponding extension surfaces, limiting the distance between a
representation of an implant component and one or more
corresponding extension surfaces, and constraining other relations
between the implant components and the extension surfaces (e.g.,
constraining rotations, translations, and/or the like between the
implant components and the extension surfaces).
[0087] FIG. 6 illustrates a split display 350 including cartilage
areas along a representation of a bone. The split display 350
includes a three-dimensional display 352 and a two-dimensional
display 354. The three-dimensional display 352 includes the
representation of the femur 152, the representation of the
patello-femoral implant component 154, and the representation of
the medial implant component 156. The three-dimensional display 352
includes cartilage points 356A, 356B, and 356C (collectively,
cartilage points 356). The three-dimensional display 352 includes
control points 358A, 358B, 358C and 358D (collectively, control
points 358). The three-dimensional display 352 includes areas
representing cartilage 360A, 360B, 360C and 360D (collectively,
areas representing cartilage 360).
[0088] The two-dimensional display 354 includes the representation
of the femur 152, the representation of the patello-femoral implant
component 154, and the representation of the medial implant
component 156. The two-dimensional display 354 includes cartilage
points 356A, 356B, and 356C. The three-dimensional display 352
includes control points 358A, 358B, and 358C. The two-dimensional
display includes a slider 310 and a change indicator 312 as
discussed above with reference to FIG. 5.
[0089] FIG. 7 illustrates an exemplary process 400 for positioning
an implant component based on areas representing cartilage, using
FIG. 6 as an example. The representation of the femur 152 can be
generated from a CT scan. In some examples, a CT scan only matches
the surface of the bone, but not the surface of articular
cartilage. In some embodiments, the surface of the cartilage can be
used to determine an optimal placement of an implant component. For
example, the thickness of articular cartilage can be determined at
critical places on the bone and used to position the implant
component. In some embodiments, a cartilage surface can be
generated by capturing (e.g., with an optical camera) the tip
positions of a tracked probe which is dragged over the cartilage
surface. The cartilage surface generated from the captured points
can be used to manually or automatically position the implant
component to the resulting surface. For example, to manually
position the implant component, the system 100 can display a
representation of the cartilage surface, and the user can
manipulate the representation of the implant component to achieve
the desired placement of the implant component surface relative to
the cartilage surface. In this example, a sufficient number of
points are captured by the probe to generate a representation of
the cartilage surface. Advantageously, cartilage thickness of the
bone can be estimated over a region by lifting a patch of the bone
model to the estimated position. A predetermined number of control
points 358 are determined (402) based on the representation of the
patello-femoral implant component 154. The control points can be,
for example, along exterior edges of the implant component, at
critical places of the implant component, at the most exterior
points of the component, any other location along the implant
component, or outside or off the implant component surface but
defined in the coordinate space of the implant component. In this
example, four control points are used. In other examples, any
number of control points can be used. Measurements and/or
calculations of the thickness and/or direction of cartilage points
356 are received (404), where each cartilage point is tied to an
associated control point from the control points 358. For example,
cartilage point 356A is measured in proximity to control point
358A. Areas representing cartilage 360 are generated (406), wherein
each area representing cartilage is larger than and projects to the
associated control point. For example, the area representing
cartilage 360A is larger than and projects to control point 358A.
For example, the system can assume the cartilage is about the same
depth within a 10 mm diameter circle from a measurement point.
Measuring one point allows an area of a 10 mm diameter to be
estimated on the bone model, rather than calculating the entire
cartilage area over the bone. Taking cartilage surface measurements
at predetermined locations near the control points allows the
locations to coincide with the control points on the implant
component, making other cartilage portions on the bone irrelevant.
A representation of the patello-femoral implant component 154 is
positioned (408) based on the representation of the femur 152. The
representation of the femur 152 includes the areas representing
cartilage 360.
[0090] In some examples, the areas representing cartilage 360 are
formed from adjusted points on the representation of the femur 152.
Forming the areas representing cartilage 360 on the representation
of the femur 152 causes protrusions along the representation of the
femur 152. The control points 358 on the representation of the
patello-femoral implant component 154 can be used to reposition the
patello-femoral implant component 154 in the coordinate space of
the implant system (e.g., the coordinate space of the
representation of the femur 152). For example, the patello-femoral
implant component 154 can be repositioned away from the
representation of the femur 152 so that the patello-femoral implant
component 154 is positioned adjacent to the representations of the
areas representing cartilage 360. Because the entire cartilage
surface was not generated along the representation of the femur
152, this can result in a gap between the patello-femoral implant
component 154 and the representation of the femur 152 where the
patello-femoral implant component 154 is not adjacent to the areas
representing cartilage 360. In this case, points can be picked on
the bone itself.
[0091] FIG. 8 illustrates an exemplary process (450) for estimating
areas representing cartilage. The surface of the cartilage is
estimated at selected points by taking one cartilage measurement at
locations on the patient's cartilage that correspond to each
control point and using the resulting distance and direction from
the representation of the bone to create an area representing
cartilage using the representation of the bone and the resulting
offset. Using, for example, a tracked probe, an operator captures
cartilage points 356 on the patient in proximity to each of the
control points 358 of the selected implant (e.g., the
representation of the patello-femoral implant 154). Take: [0092]
C.sub.B=the coordinate space of the bone model; [0093] C.sub.I=the
coordinate space of the implant; [0094] C.sub.P=the coordinate
space of the patient; [0095] T.sub.I=the transformation from CI to
CB; and [0096] T.sub.P=the transformation from CP to CB.
[0097] To estimate an area representing cartilage 360 at the
position of each control point 358 relative to the representation
of the femur 152, each cartilage point 356 is transformed (452) to
C.sub.B using T.sub.P. Each control point 358 is transformed (454)
to C.sub.B using T.sub.I. The system 100 determines the closest
point on the representation of the femur 152 to the transformed
cartilage point 356. The system 100 calculates (456) the distance
and direction from the closest point from the representation of the
femur 152 to the transformed cartilage point 356. In some
embodiments, the system 100 calculates a direction between a
closest point of the representation of the femur 152 to an
associated transformed control point and uses the distance
(cartilage thickness) of the transformed cartilage point 356 from
the representation of the femur 152. The system 100 determines
(458) a plurality of points of the representation of the femur 152
that are within a distance from the associated transformed control
point. The plurality of points from the representation of the femur
152 are adjusted (460) based on the distance and direction.
[0098] The three-dimensional representation of the femur 152 can be
made up of geometrical shapes. For example, if the representation
of the femur 152 is created with triangles, a group of triangles on
the representation of the femur 152 which are closest to the
transformed control point are determined. Each vertex in the group
is adjusted using the cartilage distance and direction to form an
area representing cartilage 360. The geometrical shapes of
three-dimensional representation of the femur 152 can be a set of
polygons. Each of the plurality of points of the representation of
the femur 152 can correspond to a set of polygons from the superset
of polygons that make up the representation of the femur 152. The
transformed control points can be registered to the closest points
on the areas representing cartilage 360 using, for example, a
paired-point registration algorithm. Geometrical shapes can be used
to represent any component (e.g., patello-femoral implant component
154, medial implant component 156, and/or lateral implant component
158).
[0099] The final registration to the areas representing cartilage
360 can be suitably constrained (e.g., around an axis) to
automatically adjust the position of one implant relative to
another. For example, if the representation of the patello-femoral
implant component 154 is adjusted based on the generated areas
representing cartilage 360, the representation of the medial
implant component 156 can be automatically adjusted to coincide
with the adjustment of the representation of the patello-femoral
implant component 154. Advantageously, all implant components can
be adjusted to account for the generation of areas representing
cartilage around one implant component.
[0100] FIGS. 9A-9D illustrate bone points along a femur 500 for
implant planning. The femur includes a mechanical axis 502,
anatomic axis 504 at 4.degree. from the mechanical axis 502, and
anatomic axis 506 at 6.degree. from the mechanical axis 502. Bone
500 includes bone points F1 through F10. Bone points F1-F10 can be
extreme points of the femur 500. The bone points can represent, for
example: [0101] F1--Most anterior medial point; [0102] F2--Most
anterior lateral point; [0103] F3--Most distal medial point; [0104]
F4--Most distal lateral point; [0105] F5--Most posterior medial
point; [0106] F6--Most posterior lateral point; [0107] F7--Most
anterior trochlear groove; [0108] F8--Most distal trochlear groove;
[0109] F9--Medial epicondyle; and [0110] F10--Lateral
epicondyle.
[0111] The femur 500 can also include points F14 and F15 (not
shown), where F14 is at the midpoint between F1 and F5, and point
F15 is at the midpoint between F2 and F6. Bone points F3 and F4
make up the distal condylar axis (DCA) 508. The DCA 508 is
approximately 3.degree. from horizontal 510. F7 and F8 represent
the Anterior-posterior axis (AP axis) 512. F9 and F10 represent the
Transepicondylar axis (TEA) 514. The TEA 514 is perpendicular to
the AP axis 512. F5 and F6 make up the posterior condylar axis
(PCA) 516. The PCA 516 is approximately 3.degree. from a line 518
that is parallel to the TEA 514.
[0112] FIGS. 10A-10C illustrate implant points on implant
components of a multiple component implant 600 (i.e., the
patello-femoral implant component 154, the medial implant component
156, and the lateral implant component 158) for implant planning.
The implant points include points C1-C15. The implant points can
represent, for example: [0113] C1--Most anterior medial point;
[0114] C2--Most anterior lateral point; [0115] C3--Most distal
medial point; [0116] C4--Most distal lateral point; [0117] C5--Most
posterior medial point; [0118] C6--Most posterior lateral point;
[0119] C7--Most anterior trochlear groove; [0120] C8--Most distal
trochlear groove; [0121] C9--Center of medial transition arc;
[0122] C10--Center of lateral transition arc; [0123] C11--Medial
transition location; [0124] C12--Lateral transition location;
[0125] C13--Superior transition location; [0126] C14--Midpoint
between points C1 and C5; and [0127] C15--Midpoint between points
C2 and C6.
[0128] Point C9 lies on the primary articular surface with the same
X and Y value as the internal edge arc center of the medial femoral
implant component (i.e., the medial implant component 156). C10
lies on the primary articular surface with the same X and Y value
as the internal edge arc center of the lateral femoral implant
component (i.e., the lateral implant component 158). C11 lies on
the primary articular surface, the midplane between the lateral
edge of the medial femoral implant component and the medial edge of
the patello-femoral implant component 154, and the midplane between
the anterior tip of the medial femoral implant component and the
posterior tip of the patello-femoral implant component 154. C11 can
serve as the location for upsizing/downsizing femoral or
patello-femoral implant components. C12 lies on the primary
articular surface, the midplane between the medial edge of the
lateral femoral implant component and the lateral edge of the
patello-femoral implant component 154, and the midplane between the
anterior tip of the lateral femoral implant component and the
posterior tip of the patello-femoral implant component 154. C12 can
also serve as the location for upsizing/downsizing femoral or
patello-femoral components. C13 lies on a surface that is midway
between the articular surface and the backside surface (1.5 mm
offset from primary articular surface), on the outer profile of the
patello-femoral implant component 154, on the trochlear groove
pathway. C14 is the midpoint between the most anterior and most
posterior medial points. C14 can be used in pre-operative planning.
C15 is the midpoint between the most anterior and most posterior
lateral points. C15 can be used in pre-operative planning.
[0129] FIGS. 11A-11C illustrate implant component axes relative to
the implant components of a multiple component implant 600 (i.e.,
the patello-femoral implant component 154, the medial implant
component 156, and the lateral implant component 158) for implant
planning. The axes can include axes A1-A15, which can represent,
for example: [0130] A1--Medial medial-lateral (ML) axis (x-axis)
through point C11 (e.g., flexion/extension); [0131] A2--Medial
antierior-posterior (AP) axis (y-axis) through point C11 (e.g.,
varus/valgus); [0132] A3--Medial superior-inferior (SI) axis
(z-axis) through point C9 (e.g., internal/external); [0133]
A4--Patello-femoral (PFJ) superior ML axis (x-axis) through point
C13 (e.g., flexion/extension); [0134] A5--Axis through points C11
and C13; [0135] A6--SI axis (z-axis) through point C8 (e.g.,
internal/external); [0136] A7--SI axis (z-axis) through point C13
(e.g., internal/external); [0137] A8--SI axis (z-axis) through
midpoint of C8 and C13 (e.g., internal/external); [0138] A9--Axis
through points C8 and C13; [0139] A10--Lateral ML axis (x-axis)
through point C12 (e.g., flexion/extension); [0140] A11--Lateral AP
axis (y-axis) through point C12 (e.g., varus/valgus); [0141]
A12--Lateral SI axis (z-axis) through point C10 (e.g.,
internal/external); [0142] A13--Axis through points C12 and C13;
[0143] A14--SI axis (z-axis) through C14 (e.g., internal/external);
and [0144] A15--AP axis (y-axis) through point C8 (e.g.,
varus/valgus).
[0145] For pre-operation planning, cartilage points can be assumed.
These cartilage points can include: [0146] F1'--Most anterior
medial point+1 mm in the Y direction; [0147] F2'--Most anterior
lateral point+1 mm in the Y direction; [0148] F3'--Most distal
medial point-2 mm in the Z direction; [0149] F4'--Most distal
lateral point-2 mm in the Z direction; [0150] F5'--Most posterior
medial point-2 mm in the Y direction; [0151] F6'--Most posterior
lateral point-2 mm in the Y direction; [0152] F7'--Most anterior
trochlear groove+2 mm in the Y direction; [0153] F8'--Most distal
trochlear groove-2 mm in the Z direction; [0154] F14'--Midpoint
between F1' and F5'; and [0155] F15'--Midpoint between F2' and
F6'.
[0156] Mapped transition points can be taken (e.g., manually with a
probe). Any number of mapped transition points can be used. These
points, for a femur for example, can include: [0157] M1--Most
anterior medial point mapped on cartilage near C1; [0158] M2--Most
anterior lateral point mapped on cartilage near C2; [0159] M7--Most
anterior trochlear point mapped on cartilage near C7; [0160]
M8--Most distal trochlear groove mapped on cartilage near C8;
[0161] M11--Medial transition mapped on cartilage near C11; [0162]
M12--Lateral transition mapped on cartilage near C12; and [0163]
M13--Superior transition mapped on bone near C13.
[0164] In some embodiments, a tibial onlay or inlay implant
component (e.g., an articular surface) can be calculated. The
tibial onlay or inlay implant component can include, for example:
[0165] P000--a poly centroid at 0.degree. flexion mapped into
femoral implant space; [0166] P090--a poly centroid at 90.degree.
flexion mapped into femoral implant space; and [0167] PXXX--any
other poly centroid at XXX.degree. flexion mapped into femoral
implant space.
[0168] Such onlays or inlays can provide, for example, a
relationship between the tibia and the femur. Advantageously, this
can prevent positioning of the implant components in a way that
adversely affects the tibia (e.g., causing excessive
tightening).
[0169] Preoperative Planning
[0170] The following is one example of preoperative planning.
Preoperative planning can include acquiring the hip center and
ankle center of the patient. Bounding box bone landmarks (e.g., for
the femur and tibia, such as points F1-F10) are acquired. The bones
of interest are orientated, and the bounding box bone landmarks can
be re-acquired based on the final orientation. A proper implant
size is selected from the variety of sizes available to the system
100. In some embodiments, a proper implant size is calculated by
computing the anterior-posterior (AP) distance as the .DELTA.Y
between points F1' and F5'. This will be described for a three
component implant. A three component implant may be, for example, a
tricompartmental implant that includes an implant component for
each of the three compartments of the joint (e.g., the medial
compartment, the lateral compartment, and the patello-femoral
compartment). For example, a tricompartmental implant can include
the patello-femoral implant component, the medial femoral implant
component, and the lateral femoral implant component. A three
component implant may also be an implant that includes three
components that are implanted in one or more compartments of the
joint (e.g., the medial compartment, the lateral compartment,
and/or the patello-femoral compartment). For example, the
patello-femoral implant component can be split into three segmented
components that are each implanted in the patello-femoral
compartment of the joint. In another example, the patello-femoral
implant component 154 could be split into two segmented components
that are used in combination with one other implant component
(e.g., the medial or lateral femoral implant component). In this
example, the three component implant is a tricompartmental implant
that includes the patello-femoral implant component (e.g.,
represented by representation 154), the medial implant component
(e.g., represented by representation 156), and the lateral implant
component (e.g., represented by representation 158). For the
tricompartmental implant, a size is selected that best matches this
distance (.DELTA.Y between points C1 and C5) by finding the size
that has the minimum difference. The system 100 displays the three
component implant, in this example, a tricompartmental implant.
[0171] A best fit is determined for the tricompartmental implant to
points F1' through F8'. In some embodiments, a best fit is found by
performing a number of steps: (1) translate the tricompartmental
implant such that C14 is at the same location as F14', (2) rotate
the tricompartmental implant about axis A14 until C15 has the same
y-value as F15', (3) translate in the medial-lateral (ML) direction
until the midpoint of C1-C2 has the same x-value as the midpoint of
F1'-F2' (or until C8 has same x-value as F8'), (4) translate in the
superior-inferior (SI) direction until C8 has the same z-value as
F8', (5) rotate about axis A15 until .DELTA.Z between points C3 and
F3' is equal to .DELTA.Z between points C4 and F4', (6) repeat
until changes are insignificant.
[0172] Intraoperative Planning
[0173] The following is an exemplary example of steps that can be
performed during intraoperative planning. During the operation, the
patient's bone is registered, as described, for example, in U.S.
Patent Publication 2006/0142657, published Jun. 29, 2006, which is
hereby incorporated by reference herein in its entirety. Bone poses
can be captured, for example, at 0.degree., 90.degree., and other
angles. Transition region points are captured (e.g., medial
cartilage transition, lateral cartilage transition, superior bone
transition, and/or the like).
[0174] An implant size is calculated for the patient. The system
100 computes the AP distance by, for example, computing the
.DELTA.Y between points M13 and P090. The system 100 selects the
tricompartmental implant size by, for example, determining the
tricompartmental implant size that has a minimum difference from
the .DELTA.Y between points C5 and C13. The system 100 can display
a representation of the selected tricompartmental implant (e.g.,
through display 108 of FIG. 1).
[0175] The system 100 fits the implant to pose capture and
transition region acquisition points.
[0176] For example, the system 100 or a user can move (e.g.,
rotate, translate, etc.) the patello-femoral implant component
(e.g., the representation 154) to a desired orientation and
location. In some examples, the femoral components (e.g., the
representations 156, 158) move linked to the patello-femoral
implant component. In some examples, the patello-femoral implant
component can be automatically fit to the bone with movements
(e.g., rotations, translations, etc.) to match the patello-femoral
implant component to the mapped points (e.g., the mapped transition
points M1, M2, M7, M8, M11, M12, M13).
[0177] Other computer operations can be performed, such as a fit to
the femoral condyle of the femur or a fit to all portions of the
bone. This will be described for a two component implant. A two
component implant may be, for example, a bicompartmental implant
that includes an implant component for two of the three
compartments of the joint (e.g., the medial compartment, the
lateral compartment, the patello-femoral compartment). For example,
a bicompartmental implant can include the patello-femoral implant
component and either the medial femoral implant component or the
lateral femoral implant component. In another example, a
bicompartmental implant can include the medial and lateral femoral
implant components. A two component implant may also be an implant
that includes two components that are implanted in one compartment
of the joint (e.g., the medial compartment, the lateral
compartment, or the patello-femoral compartment). For example, the
patello-femoral implant component can be split into two segmented
components that are each implanted in the patello-femoral
compartment of the joint. In this example, the two component
implant is a bicompartmental implant that includes the
patello-femoral implant component (e.g., the representation 154)
and the medial implant component (e.g., the representation 156).
The bicompartmental implant AP can be moved so that C13 has the
same y-value as M13. The bicompartmental implant SI can be moved so
that C8 has the same z-value as M8. The femoral component
internal-external (IE) can be rotated about axis A3 until the
x-value of C5 matches the x-value of P090. The femoral component
flexion-extension (FE) can be rotated about axis A1 until the
z-value of C3 matches the z-value of P000.
[0178] The posterior gap can be calculated and/or displayed by
measuring the .DELTA.Y between points C5 and P090. The system 100
can determine the fit (e.g., if there is a gap/loose or if there is
an overlap/tight). If the system 100 determines the posterior gap
is loose, the length can be increased. To increase length, for
example, the bicompartmental implant can be flexed about axis A4.
The system 100 can determine the rotation angle value for each size
that approximately yields a 0.5 mm length increase. To decrease
length, the bicompartmental implant can be extended about axis A4.
The system 100 can determine the rotation angle value for each size
that approximately yields a 0.5 mm length increase. The user can,
for example, click the display to adjust the length by a
predetermined amount (e.g., increase/decrease the length by 0.5
mm). Any number of these steps can be repeated one or more times to
achieve a desired posterior gap.
[0179] Adjustments can be made to the femoral component (e.g., the
medial implant component 156 or the lateral implant component 158).
For example, the varus/valgus can be adjusted to fit the bone, the
flexion/extension can be adjusted to change the extension gap, and
any other adjustment can be made. To increase or decrease a size of
the implant system or implant components (e.g., the
femoral/patello-femoral), a new component can be placed in at C11.
To upsize and/or downsize the femoral implant component when, for
example, the bone has already been resected to include peg holes to
receive the pegs (or posts) on the back of the femoral implant
component and a pocket to receive the body of the femoral implant
component, the next sized femoral implant component needs can be
placed into position at the peg axes at a predetermined depth.
Tibial inlay and/or onlay implant component articular surfaces can
be matched. The system 100 can calculate the angle change necessary
to increase and/or decrease the size of the bicompartmental
implant. The tricompartmental implant can be automatically fit to
the bone, pose, transition, and/or the like. While the above
example was described with reference to the medial femoral implant
component, those skilled in the art can appreciate these systems
and methods can be extended to any multiple implant component
system.
[0180] FIG. 12 shows an embodiment of an exemplary surgical system
710 in which the techniques described above can be implemented.
Such an exemplary system is described in detail, for example, in
U.S. Patent Publication 2006/0142657, published Jun. 29, 2006,
which is hereby incorporated by reference herein in its entirety.
The surgical system 710 includes a computing system 720, a haptic
device 730, and a navigation system 40. In operation, the surgical
system 710 enables comprehensive, intraoperative surgical planning.
The surgical system 710 also provides haptic guidance to a user
(e.g., a surgeon) and/or limits the user's manipulation of the
haptic device 730 as the user performs a surgical procedure.
Although included for completeness in the illustrated embodiment,
the haptic device 730 and its associated hardware and software is
not necessary to perform the techniques described herein.
[0181] The computing system 720 includes hardware and software
apparatus for operation and control of the surgical system 710.
Such hardware and/or software apparatus is configured to enable the
system 710 to perform the techniques described herein. In FIG. 12,
the computing system 720 includes a computer 721, a display device
723, and an input device 725. The computing system 720 may also
include a cart 729.
[0182] The computer 721 may be any known computing system but is
preferably a programmable, processor-based system. For example, the
computer 721 may include a microprocessor, a hard drive, random
access memory (RAM), read only memory (ROM), input/output (I/O)
circuitry, and any other well-known computer component. The
computer 721 is preferably adapted for use with various types of
storage devices (persistent and removable), such as, for example, a
portable drive, magnetic storage (e.g., a floppy disk), solid state
storage (e.g., a flash memory card), optical storage (e.g., a
compact disc or CD), and/or network/Internet storage. The computer
721 may comprise one or more computers, including, for example, a
personal computer (e.g., an IBM-PC compatible computer) or a
workstation (e.g., a SUN or Silicon Graphics workstation) operating
under a Windows, MS-DOS, UNIX, or other suitable operating system
and preferably includes a graphical user interface (GUI).
[0183] The display device 723 is a visual interface between the
computing system 720 and the user. The display device 723 is
connected to the computer 721 and may be any device suitable for
displaying text, images, graphics, and/or other visual output. For
example, the display device 723 may include a standard display
screen (e.g., LCD, CRT, plasma, etc.), a touch screen, a wearable
display (e.g., eyewear such as glasses or goggles), a projection
display, a head-mounted display, a holographic display, and/or any
other visual output device. The display device 723 may be disposed
on or near the computer 721 (e.g., on the cart 729 as shown in FIG.
12) or may be remote from the computer 721 (e.g., mounted on a wall
of an operating room or other location suitable for viewing by the
user). The display device 723 is preferably adjustable so that the
user can position/reposition the display device 723 as needed
during a surgical procedure. For example, the display device 723
may be disposed on an adjustable arm (not shown) that is connected
to the cart 729 or to any other location well-suited for ease of
viewing by the user.
[0184] The display device 723 may be used to display any
information useful for a medical procedure, such as, for example,
images of anatomy generated from an image data set obtained using
conventional imaging techniques, graphical models (e.g., CAD models
of implants, instruments, anatomy, etc.), graphical representations
of a tracked object (e.g., anatomy, tools, implants, etc.),
constraint data (e.g., axes, articular surfaces, etc.),
representations of implant components, digital or video images,
registration information, calibration information, patient data,
user data, measurement data, software menus, selection buttons,
status information, and the like. In some examples, the display
device 723 displays the two dimensional and/or three dimensional
displays as illustrated in FIGS. 2, 4A-4B, 5, and 6.
[0185] In addition to the display device 723, the computing system
720 may include an acoustic device (not shown) for providing
audible feedback to the user. The acoustic device is connected to
the computer 721 and may be any known device for producing sound.
For example, the acoustic device may comprise speakers and a sound
card, a motherboard with integrated audio support, and/or an
external sound controller. In operation, the acoustic device may be
adapted to convey information to the user. For example, the
computer 721 may be programmed to signal the acoustic device to
produce a sound, such as a voice synthesized verbal indication
"DONE," to indicate that a step of a surgical procedure is
complete. Similarly, the acoustic device may be used to alert the
user to a sensitive condition, such as producing a beep to indicate
that a surgical cutting tool is nearing a critical portion of soft
tissue.
[0186] The input device 725 of the computing system 720 enables the
user to communicate with the surgical system 710. The input device
725 is connected to the computer 721 and may include any device
enabling a user to provide input to a computer. For example, the
input device 725 can be a known input device, such as a keyboard, a
mouse, a trackball, a touch screen, a touch pad, voice recognition
hardware, dials, switches, buttons, a trackable probe, a foot
pedal, a remote control device, a scanner, a camera, a microphone,
and/or a joystick. For example, the input device 725 allows a user
to move one or more components displayed on display device 723
based on one or more constraints, as described above, for planning
the implant installation.
[0187] The computing system 720 is coupled to a computing device
731 of the haptic device 730 via an interface 7100a and to the
navigation system 40 via an interface 100b. Interfaces 7100a and
100b can include a physical interface and a software interface. The
physical interface may be any known interface such as, for example,
a wired interface (e.g., serial, USB, Ethernet, CAN bus, and/or
other cable communication interface) and/or a wireless interface
(e.g., wireless Ethernet, wireless serial, infrared, and/or other
wireless communication system). The software interface may be
resident on the computer 721, the computing device 731, and/or the
navigation system 40. In some embodiments, the computer 721 and the
computing device 731 are the same computing device.
[0188] The surgical system 710 has additional features as described
in U.S. patent application Ser. No. 11/963,547, filed Dec. 21,
2007, which is hereby incorporated by reference herein in its
entirety. In some examples, the surgical system 710 allows a user
to plan the installation of a multiple component implant in a
patient using the computing system 720. The user, for example, uses
the input device 725 to position (e.g., rotate, translate, shift,
etc.) one or more components of a multiple component implant based
on one or more constraints to properly fit the unique anatomy of
the patient. The planning procedure, once completed, is transmitted
to and/or used by the haptic device 730 via interface 7100a to
assist a surgeon during the bone preparation and implant
installation procedure.
[0189] In some examples, the haptic device 730 is the Tactile
Guidance System.TM. (TGS.TM.) manufactured by MAKO Surgical Corp.,
which is used to prepare the surface of the patient's bone for
insertion of the implant system. The haptic device 730 provides
haptic (or tactile) guidance to guide the surgeon during a surgical
procedure. As described in U.S. Patent Publication 2006/0142657,
published Jun. 29, 2006, which is hereby incorporated by reference
herein in its entirety, the haptic device is an interactive
surgical robotic arm that holds a surgical tool (e.g., a surgical
burr) and is manipulated by the surgeon to perform a procedure on
the patient, such as cutting a surface of a bone in preparation for
implant installation. As the surgeon manipulates the robotic arm to
move the tool and sculpt the bone, the haptic device 730 guides the
surgeon by providing force feedback that constrains the tool from
penetrating a virtual boundary.
[0190] For example, the surgical tool is coupled to the robotic arm
and registered to the patient's anatomy. The surgeon operates the
tool by manipulating the robotic arm to move the tool and perform
the cutting operation. As the surgeon cuts, an optical camera 41 of
the navigation system 40 tracks the location of the tool and the
patient's anatomy. The patient's anatomy can be tracked, for
example, by attaching a tracking array 43a to the patient's femur F
and a tracking array 43b to the patient's tibia T, as shown in FIG.
12. The tracking arrays 43a, 43b are detectable by the optical
camera 41. In most cases, the haptic device 730 allows the surgeon
to freely move the tool in the workspace. However, when the tool is
in proximity to the virtual boundary (which is also registered to
the patient's anatomy), the haptic device 730 controls the haptic
device to provide haptic guidance (e.g., force feedback) that tends
to constrain the surgeon from penetrating the virtual boundary with
the tool.
[0191] The virtual boundary may represent, for example, a cutting
boundary defining a region of bone to be removed or a virtual
pathway for guiding the surgical tool to a surgical site without
contacting critical anatomical structures. The virtual boundary may
be defined by a haptic object (e.g., one or more haptic objects, as
described below in further detail), and the haptic guidance may be
in the form of force feedback (i.e., force and/or torque) that is
mapped to the haptic object and experienced by the surgeon as
resistance to further tool movement in the direction of the virtual
boundary. Thus, the surgeon may feel the sensation that the tool
has encountered a physical object, such as a wall. In this manner,
the virtual boundary functions as a highly accurate virtual cutting
guide. For example, the virtual boundary can represent a region of
cartilage and/or bone to be removed for properly fitting the
medial, lateral, and patello-femoral implant components to the
patient's femur as planned through the implant planning procedure
described above. Such virtual boundaries can help to ensure the
efficient and accurate removal of portions of a patient's anatomy
to accurately fit implant components based on a customized implant
planning for the patient. This also ensures that the actual
placement of the implant components meets the constraints that were
used in planning the placement of each of the physically separate
implant components.
[0192] In some examples, the haptic device 730 includes a visual
display (e.g., the display device 723 shown in FIG. 12) showing the
amount of bone removed during the cutting operation. Because the
haptic device 730 utilizes tactile force feedback, the haptic
device 730 can supplement or replace direct visualization of the
surgical site and enhance the surgeon's natural tactile sense and
physical dexterity. Guidance from the haptic device 730 coupled
with computer aided surgery (CAS), enables the surgeon to actively
and accurately control surgical actions (e.g., bone cutting) to
achieve the tolerances and complex bone resection shapes that
enable optimal and customized installation of implants.
[0193] In addition to bone preparation, a CAS system enables the
surgeon to customize the placement of the implant components to
construct a prosthetic device tailored to the specific needs of the
patient based on the patient's unique anatomy, ligament stability,
kinematics, and/or disease state. Implant planning may be
accomplished preoperatively or intraoperatively and may be
evaluated and adjusted in real time during execution of the
surgical procedure. In a preferred embodiment, implant planning is
accomplished using the surgical system 710. For example, as
described above, the surgeon may use the surgical planning features
of the computing system 720 to plan the placement of
representations of each implant component relative to a
preoperative CT image (or other image or model of the anatomy). The
software enables the surgeon to view the placement of each
component relative to the anatomy (e.g., bone, articular cartilage
surfaces, and/or the like) and to other components, as described,
for example, in U.S. Patent Publication 2006/0142657, published
Jun. 29, 2006, which is hereby incorporated by reference herein in
its entirety. Further, the software enables the surgeon to view
constraints associated with the placement of each component (e.g.,
articular surfaces, axes of constraint, and/or the like). The
software may also be configured to illustrate how the components
will interact as the joint moves through a range of motion. Based
on the component placement selected by the surgeon, the haptic
device 730 software generates one or more haptic objects, which
create one or more virtual boundaries representing, for example, a
portion of bone to be removed or critical anatomy to be avoided
based at least in part on the placement of the implant components.
During surgery, the haptic object is registered to the patient's
anatomy. By providing force feedback, the haptic device 730 enables
the surgeon to interact with the haptic object in the virtual
environment. In this manner, the haptic device 730 haptically
guides the surgeon during bone preparation to sculpt or contour the
appropriate location of the bone so that a shape of the bone
substantially conforms to a shape of a mating surface of a
component of the multiple component implant. For example, a haptic
object can be created to represent the portion of the bone and/or
cartilage area to be removed for implanting the medial femoral
implant component (e.g., represented by the representation
156).
[0194] In a preferred embodiment, the haptic device 730 is used by
the surgeon to preoperatively plan implant placement using computer
simulation tools to determine whether the preoperative plan will
result in the desired clinical results (e.g., using constraints).
Then, during surgery, the surgeon may query the soft tissue and
ligaments as the joint is moved through a range of motion using
appropriate instrumentation and sensors as is well known. This
information may be combined with the computer simulation
information of the haptic device 730 to adjust the implant planning
and/or suggest to the surgeon potential changes and adjustments to
implant placement that may achieve the desired clinical
outcomes.
[0195] The above-described systems and methods can be implemented
in digital electronic circuitry, in computer hardware, firmware,
and/or software. The implementation can be as a computer program
product (i.e., a computer program tangibly embodied in an
information carrier). The implementation can, for example, be in a
machine-readable storage device, for execution by, or to control
the operation of, a data processing apparatus. The implementation
can, for example, be a programmable processor, a computer, and/or
multiple computers.
[0196] A computer program can be written in any form of programming
language, including compiled and/or interpreted languages, and the
computer program can be deployed in any form, including as a
stand-alone program or as a subroutine, element, and/or other unit
suitable for use in a computing environment. A computer program can
be deployed to be executed on one computer or on multiple computers
at one site.
[0197] Method steps can be performed by one or more programmable
processors executing a computer program to perform functions of the
invention by operating on input data and generating output. Method
steps can also be performed by and an apparatus can be implemented
as special purpose logic circuitry. The circuitry can, for example,
be a FPGA (field programmable gate array) and/or an ASIC
(application-specific integrated circuit). Modules, subroutines,
and software agents can refer to portions of the computer program,
the processor, the special circuitry, software, and/or hardware
that implements that functionality.
[0198] Processors suitable for the execution of a computer program
include, by way of example, both general and special purpose
microprocessors, and any one or more processors of any kind of
digital computer. Generally, a processor receives instructions and
data from a read-only memory or a random access memory or both. The
essential elements of a computer are a processor for executing
instructions and one or more memory devices for storing
instructions and data. Generally, a computer can include, can be
operatively coupled to receive data from and/or transfer data to
one or more mass storage devices for storing data (e.g., magnetic,
magneto-optical disks, or optical disks).
[0199] Data transmission and instructions can also occur over a
communications network. Information carriers suitable for embodying
computer program instructions and data include all forms of
non-volatile memory, including by way of example semiconductor
memory devices. The information carriers can, for example, be
EPROM, EEPROM, flash memory devices, magnetic disks, internal hard
disks, removable disks, magneto-optical disks, CD-ROM, and/or
DVD-ROM disks. The processor and the memory can be supplemented by,
and/or incorporated in special purpose logic circuitry.
[0200] To provide for interaction with a user, the above described
techniques can be implemented on a computer having a display
device. The display device can, for example, be a cathode ray tube
(CRT) and/or a liquid crystal display (LCD) monitor. The
interaction with a user can, for example, be a display of
information to the user and a keyboard and a pointing device (e.g.,
a mouse or a trackball) by which the user can provide input to the
computer (e.g., interact with a user interface element). Other
kinds of devices can be used to provide for interaction with a
user. Other devices can, for example, be feedback provided to the
user in any form of sensory feedback (e.g., visual feedback,
auditory feedback, or tactile feedback). Input from the user can,
for example, be received in any form, including acoustic, speech,
and/or tactile input.
[0201] The above described techniques can be implemented in a
distributed computing system that includes a back-end component.
The back-end component can, for example, be a data server, a
middleware component, and/or an application server. The above
described techniques can be implemented in a distributing computing
system that includes a front-end component. The front-end component
can, for example, be a client computer having a graphical user
interface, a Web browser through which a user can interact with an
example implementation, and/or other graphical user interfaces for
a transmitting device. The components of the system can be
interconnected by any form or medium of digital data communication
(e.g., a communication network). Examples of communication networks
include a local area network (LAN), a wide area network (WAN), the
Internet, wired networks, and/or wireless networks.
[0202] The system can include clients and servers. A client and a
server are generally remote from each other and typically interact
through a communication network. The relationship of client and
server arises by virtue of computer programs running on the
respective computers and having a client-server relationship to
each other.
[0203] Packet-based networks can include, for example, the
Internet, a carrier internet protocol (IP) network (e.g., local
area network (LAN), wide area network (WAN), campus area network
(CAN), metropolitan area network (MAN), home area network (HAN)), a
private IP network, an IP private branch exchange (IPBX), a
wireless network (e.g., radio access network (RAN), 802.11 network,
802.16 network, general packet radio service (GPRS) network,
HiperLAN), and/or other packet-based networks. Circuit-based
networks can include, for example, the public switched telephone
network (PSTN), a private branch exchange (PBX), a wireless network
(e.g., RAN, bluetooth, code-division multiple access (CDMA)
network, time division multiple access (TDMA) network, global
system for mobile communications (GSM) network), and/or other
circuit-based networks.
[0204] The transmitting device can include, for example, a
computer, a computer with a browser device, a telephone, an IP
phone, a mobile device (e.g., cellular phone, personal digital
assistant (PDA) device, laptop computer, electronic mail device),
and/or other communication devices. The browser device includes,
for example, a computer (e.g., desktop computer, laptop computer)
with a world wide web browser (e.g., Microsoft.RTM.) Internet
Explorer available from Microsoft Corporation, Mozilla.RTM. Firefox
available from Mozilla Corporation). The mobile computing device
includes, for example, a personal digital assistant (PDA).
[0205] Comprise, include, and/or plural forms of each are open
ended and include the listed parts and can include additional parts
that are not listed. And/or is open ended and includes one or more
of the listed parts and combinations of the listed parts.
[0206] One skilled in the art will realize the invention may be
embodied in other specific forms without departing from the spirit
or essential characteristics thereof. The foregoing embodiments are
therefore to be considered in all respects illustrative rather than
limiting of the invention described herein. Scope of the invention
is thus indicated by the appended claims, rather than by the
foregoing description, and all changes that come within the meaning
and range of equivalency of the claims are therefore intended to be
embraced therein.
* * * * *