U.S. patent application number 16/298722 was filed with the patent office on 2019-10-10 for alignment precision.
The applicant listed for this patent is Smith & Nephew, Inc.. Invention is credited to Ryan Lloyd LANDON, Brian W. MCKINNON, Zachary Christopher WILKINSON.
Application Number | 20190307512 16/298722 |
Document ID | / |
Family ID | 55064759 |
Filed Date | 2019-10-10 |
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United States Patent
Application |
20190307512 |
Kind Code |
A1 |
WILKINSON; Zachary Christopher ;
et al. |
October 10, 2019 |
ALIGNMENT PRECISION
Abstract
Alignment precision technology, in which a system accesses image
data of a bone to which a reference marker array is fixed. The
system generates a three-dimensional representation of the bone and
the reference markers, defines a coordinate system for the
three-dimensional representation, and determines locations of the
reference markers relative to the coordinate system. The system
accesses intra-operative image data that includes the bone and a
mobile marker array that is attached to an instrument used in a
surgical procedure. The system co-registers the intra-operative
image data with the three-dimensional representation by matching
the reference markers included in the intra-operative image data to
the locations of the reference markers. The system determines
locations of the mobile markers in the co-registered image and
determines a three-dimensional spatial position and orientation of
the instrument relative to the bone.
Inventors: |
WILKINSON; Zachary Christopher;
(Germantown, TN) ; LANDON; Ryan Lloyd; (Southaven,
MS) ; MCKINNON; Brian W.; (Bartlett, TN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Smith & Nephew, Inc. |
Memphis |
TN |
US |
|
|
Family ID: |
55064759 |
Appl. No.: |
16/298722 |
Filed: |
March 11, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16110297 |
Aug 23, 2018 |
10226301 |
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16298722 |
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15102705 |
Jun 8, 2016 |
10080616 |
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PCT/US2015/039351 |
Jul 7, 2015 |
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16110297 |
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62021551 |
Jul 7, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2034/256 20160201;
A61B 17/157 20130101; A61B 2090/3983 20160201; A61B 17/155
20130101; A61B 34/20 20160201; A61B 34/00 20160201; A61B 2090/364
20160201; A61B 2034/107 20160201; A61B 2090/0818 20160201; A61B
2090/363 20160201; A61B 2090/3966 20160201; A61B 17/1764 20130101;
A61B 2034/2055 20160201; A61B 2034/102 20160201 |
International
Class: |
A61B 34/20 20060101
A61B034/20; A61B 34/00 20060101 A61B034/00; A61B 17/15 20060101
A61B017/15; A61B 17/17 20060101 A61B017/17 |
Claims
1. A system comprising: at least one processor; and at least one
computer-readable medium coupled to the at least one processor
having stored thereon instructions which, when executed by the at
least one processor, causes the at least one processor to perform
operations comprising: accessing first image data of at least a
portion of a bone to which a reference fiducial marker array is
fixed in advance of a surgical procedure, the reference fiducial
marker array comprising at least three reference fiducial markers
and the first image data being captured using a first imaging
modality that is configured to image the reference fiducial markers
and three-dimensional anatomic landmark data for the portion of the
bone; generating a three-dimensional representation of the portion
of the bone and the reference fiducial markers based on the first
image data; defining a coordinate system for the three-dimensional
representation of the portion of the bone; determining locations of
the reference fiducial markers relative to the defined coordinate
system; accessing intra-operative image data that includes the
portion of the bone to which to the reference fiducial marker array
is fixed and a mobile fiducial marker array that is attached to an
instrument used in the surgical procedure on the portion of the
bone, the mobile fiducial marker array comprising at least three
mobile fiducial markers and the intra-operative image data being
captured using a second imaging modality that is different than the
first imaging modality and that is configured to image the
reference fiducial markers and the mobile fiducial markers;
co-registering the intra-operative image data with the
three-dimensional representation of the portion of the bone by
matching the reference fiducial markers included in the
intra-operative image data to the determined locations of the
reference fiducial markers relative to the defined coordinate
system; determining locations of the mobile fiducial markers in the
co-registered intra-operative image data and three-dimensional
representation of the portion of the bone; determining a
three-dimensional spatial position and orientation of the
instrument relative to the portion of the bone based on the
determined locations of the mobile fiducial markers; comparing the
three-dimensional spatial position and orientation of the
instrument relative to the portion of the bone with a designed
alignment of the instrument to the portion of the bone; based on
comparison results, determining an indication of precision of
alignment of the instrument in the surgical procedure on the
portion of the bone relative to the designed alignment of the
instrument to the portion of the bone; and providing output based
on the determined indication of precision of alignment of the
instrument in the surgical procedure relative to the designed
alignment of the instrument.
2. The system of claim 1: wherein accessing first image data of the
portion of the bone to which the reference fiducial marker array is
fixed comprises accessing computed tomography (CT) image data of
the portion of the bone and the reference fiducial markers; and
wherein accessing intra-operative image data that includes the
portion of the bone to which to the reference fiducial marker array
is fixed and the mobile fiducial marker array that is attached to
the instrument used in the surgical procedure on the portion of the
bone comprises accessing intra-operative motion capture data that
includes the portion of the bone to which to the reference fiducial
marker array is fixed and the mobile fiducial marker array that is
attached to the instrument used in the surgical procedure on the
portion of the bone.
3. The system of claim 1, wherein generating the three-dimensional
representation of the portion of the bone and the reference
fiducial markers based on the first image data comprises generating
a three-dimensional solid that includes the portion of the bone and
the reference fiducial marker array.
4. The system of claim 1, wherein determining the three-dimensional
spatial position and orientation of the instrument relative to the
portion of the bone based on the determined locations of the mobile
fiducial markers comprises: accessing data defining
three-dimensional spatial position and orientation of the
instrument relative to the mobile fiducial markers determined using
a computer-aided-design (CAD) model of the instrument with the
mobile fiducial marker array attached; and determining the
three-dimensional spatial position and orientation of the
instrument relative to the portion of the bone by mapping the
three-dimensional spatial position and orientation of the
instrument relative to the mobile fiducial markers to the
determined locations of the mobile fiducial markers.
5. The system of claim 1, wherein determining the three-dimensional
spatial position and orientation of the instrument relative to the
portion of the bone based on the determined locations of the mobile
fiducial markers comprises: accessing data defining
three-dimensional spatial position and orientation of the
instrument relative to the mobile fiducial markers determined using
a coordinate measurement machine (CMM) evaluation of the instrument
with the mobile fiducial marker array attached; and determining the
three-dimensional spatial position and orientation of the
instrument relative to the portion of the bone by mapping the
three-dimensional spatial position and orientation of the
instrument relative to the mobile fiducial markers to the
determined locations of the mobile fiducial markers.
6. The system of claim 1: wherein determining locations of the
reference fiducial markers relative to the defined coordinate
system comprises: accessing CMM data for the reference fiducial
marker array, and validating the determined locations of the
reference fiducial markers using the accessed CMM data for the
reference fiducial marker array; and wherein determining locations
of the mobile fiducial markers in the co-registered intra-operative
image data and three-dimensional representation of the portion of
the bone comprises: accessing CMM data for the mobile fiducial
marker array, and validating the determined locations of the mobile
fiducial markers using the accessed CMM data for the mobile
fiducial marker array.
7. The system of claim 1, wherein the reference fiducial markers
and the mobile fiducial markers are radio-opaque, infrared
reflective spherical markers.
8. The system of claim 7: wherein the reference fiducial marker
array comprises at least five reference spherical markers; and
wherein the mobile fiducial marker array comprises at least five
mobile spherical markers.
9. The system of claim 7: wherein determining locations of the
reference fiducial markers relative to the defined coordinate
system comprises: determining centers of the reference spherical
markers, and determining locations of the reference fiducial
markers as the determined centers of the reference spherical
markers; and wherein determining locations of the mobile fiducial
markers in the co-registered intra-operative image data and
three-dimensional representation of the portion of the bone
comprises: determining centers of the mobile spherical markers, and
determining locations of the mobile fiducial markers as the
determined centers of the mobile spherical markers.
10. The system of claim 7: wherein determining locations of the
reference fiducial markers relative to the defined coordinate
system comprises: identifying the reference spherical markers,
regression fitting each of the identified reference spherical
markers with an ideal sphere shape, and determining locations of
the reference spherical markers using the regression-fitted
reference spherical markers; and wherein determining locations of
the mobile fiducial markers in the co-registered intra-operative
image data and three-dimensional representation of the portion of
the bone comprises: identifying the mobile spherical markers,
regression fitting each of the identified mobile spherical markers
with an ideal sphere shape, and determining locations of the mobile
spherical markers using the regression-fitted reference spherical
markers.
11. The system of claim 1, wherein generating the three-dimensional
representation of the portion of the bone and the reference
fiducial markers based on the first image data and defining the
coordinate system for the three-dimensional representation of the
portion of the bone comprising: identifying a measurement for
cartilage related to the portion of the bone; and adjusting the
three-dimensional representation and the coordinate system to
account for the identified measurement for cartilage related to the
portion of the bone.
12. The system of claim 11, wherein identifying the measurement for
cartilage related to the portion of the bone comprises: accessing
magnetic resonance imaging (MRI) of the portion of the bone; and
determining a measurement of the cartilage based on the MRI of the
portion of the bone.
13. The system of claim 1, wherein the instrument used in the
surgical procedure is a cutting block used in total knee
arthroplasty (TKA).
14. The system of claim 13, wherein the mobile fiducial marker
array is attached to the cutting block through the cutting slot of
the cutting block and at least one other portion of the cutting
block.
15. The system of claim 14, wherein the mobile fiducial marker
array is attached to the cutting block through the cutting slot of
the cutting block and at least one pin hole of the cutting
block.
16. The system of claim 14, wherein the mobile fiducial marker
array is attached to the cutting block through the cutting slot
using a surgical blade designed to be inserted through the cutting
slot and one or more shims that rigidly support the surgical blade
in the cutting slot.
17. The system of claim 1, wherein the operations further comprise:
accessing data descriptive of post-operative validation of cuts
made during the surgical procedure; and validating the determined
indication of precision of alignment based on the accessed data
descriptive of post-operative validation of cuts made during the
surgical procedure.
18. The system of claim 1, wherein providing output based on the
determined indication of precision of alignment of the instrument
in the surgical procedure relative to the designed alignment of the
instrument comprises: aggregating the determined indication of
precision of alignment of the instrument in the surgical procedure
relative to the designed alignment of the instrument with similar
data determined from other similar surgical procedures; performing
statistical analysis of the aggregated data; determining a
representation of general alignment precision in surgical
procedures included in the aggregated data based on the statistical
analysis of the aggregated data; and providing output indicating
the determined representation of general alignment precision.
19. A method comprising: accessing first image data of at least a
portion of a bone to which a reference fiducial marker array is
fixed in advance of a surgical procedure, the reference fiducial
marker array comprising at least three reference fiducial markers
and the first image data being captured using a first imaging
modality that is configured to image the reference fiducial markers
and three-dimensional anatomic landmark data for the portion of the
bone; generating a three-dimensional representation of the portion
of the bone and the reference fiducial markers based on the first
image data; defining a coordinate system for the three-dimensional
representation of the portion of the bone; determining locations of
the reference fiducial markers relative to the defined coordinate
system; accessing intra-operative image data that includes the
portion of the bone to which to the reference fiducial marker array
is fixed and a mobile fiducial marker array that is attached to an
instrument used in the surgical procedure on the portion of the
bone, the mobile fiducial marker array comprising at least three
mobile fiducial markers and the intra-operative image data being
captured using a second imaging modality that is different than the
first imaging modality and that is configured to image the
reference fiducial markers and the mobile fiducial markers;
co-registering the intra-operative image data with the
three-dimensional representation of the portion of the bone by
matching the reference fiducial markers included in the
intra-operative image data to the determined locations of the
reference fiducial markers relative to the defined coordinate
system; determining locations of the mobile fiducial markers in the
co-registered intra-operative image data and three-dimensional
representation of the portion of the bone; determining a
three-dimensional spatial position and orientation of the
instrument relative to the portion of the bone based on the
determined locations of the mobile fiducial markers; comparing the
three-dimensional spatial position and orientation of the
instrument relative to the portion of the bone with a designed
alignment of the instrument to the portion of the bone; based on
comparison results, determining an indication of precision of
alignment of the instrument in the surgical procedure on the
portion of the bone relative to the designed alignment of the
instrument to the portion of the bone; and providing output based
on the determined indication of precision of alignment of the
instrument in the surgical procedure relative to the designed
alignment of the instrument.
20. At least one computer-readable storage medium encoded with
executable instructions that, when executed by at least one
processor, cause the at least one processor to perform operations
comprising: accessing first image data of at least a portion of a
bone to which a reference fiducial marker array is fixed in advance
of a surgical procedure, the reference fiducial marker array
comprising at least three reference fiducial markers and the first
image data being captured using a first imaging modality that is
configured to image the reference fiducial markers and
three-dimensional anatomic landmark data for the portion of the
bone; generating a three-dimensional representation of the portion
of the bone and the reference fiducial markers based on the first
image data; defining a coordinate system for the three-dimensional
representation of the portion of the bone; determining locations of
the reference fiducial markers relative to the defined coordinate
system; accessing intra-operative image data that includes the
portion of the bone to which to the reference fiducial marker array
is fixed and a mobile fiducial marker array that is attached to an
instrument used in the surgical procedure on the portion of the
bone, the mobile fiducial marker array comprising at least three
mobile fiducial markers and the intra-operative image data being
captured using a second imaging modality that is different than the
first imaging modality and that is configured to image the
reference fiducial markers and the mobile fiducial markers;
co-registering the intra-operative image data with the
three-dimensional representation of the portion of the bone by
matching the reference fiducial markers included in the
intra-operative image data to the determined locations of the
reference fiducial markers relative to the defined coordinate
system; determining locations of the mobile fiducial markers in the
co-registered intra-operative image data and three-dimensional
representation of the portion of the bone; determining a
three-dimensional spatial position and orientation of the
instrument relative to the portion of the bone based on the
determined locations of the mobile fiducial markers; comparing the
three-dimensional spatial position and orientation of the
instrument relative to the portion of the bone with a designed
alignment of the instrument to the portion of the bone; based on
comparison results, determining an indication of precision of
alignment of the instrument in the surgical procedure on the
portion of the bone relative to the designed alignment of the
instrument to the portion of the bone; and providing output based
on the determined indication of precision of alignment of the
instrument in the surgical procedure relative to the designed
alignment of the instrument.
21. A method comprising: accessing an MRI image of at least a
portion of a cadaver patient's leg that includes a knee of the
cadaver patient; determining cartilage thickness for the knee of
the cadaver patient based on the accessed MRI image; accessing a CT
image of at least a portion of the cadaver patient's leg that
includes CT imaging of at least a portion of a femur to which a
reference fiducial marker array is fixed in advance of a TKA
procedure and CT imaging of at least a portion of a tibia, the
reference fiducial marker array comprising at least three reference
fiducial markers that are captured in CT imaging and motion capture
imaging; defining, on the accessed CT image and accounting for the
determined cartilage thickness, a first coordinate system for the
femur and a second coordinate system for the tibia; generating a
processed CT image by calculating a three-dimensional
transformation between the CT image on which the first coordinate
system for the femur and the second coordinate system for the tibia
have been defined and a pattern of the reference fiducial marker
array as measured by the CT image; accessing intra-operative motion
capture data of at least a portion of the cadaver patient's leg
that includes motion capture imaging of at least a portion of the
femur to which the reference fiducial marker array is fixed and
motion capture imaging of at least a portion of the tibia, the
intra-operative motion capture data being captured during the TKA
procedure on the cadaver patient's leg and including motion capture
imaging of a mobile fiducial marker array that is attached to a
cutting block used in the TKA procedure on the cadaver patient's
leg, the mobile fiducial marker array comprising at least three
mobile fiducial markers that are captured in motion capture
imaging; co-registering the intra-operative motion capture data
with the processed CT image by regression fitting the reference
fiducial markers included in the intra-operative motion capture
data to the reference fiducial markers included in the processed CT
image; generating a processed motion capture image by calculating a
three-dimensional transformation between the co-registered
intra-operative motion capture data and processed CT image and a
pattern of the mobile fiducial marker array as measured by the
intra-operative motion capture data; accessing a first CAD model of
the mobile fiducial marker array; co-registering the first CAD
model of the mobile fiducial marker array with the processed motion
capture image by regression fitting the mobile fiducial markers
included in the first CAD model of the mobile fiducial marker array
to the mobile fiducial markers included in the processed motion
capture image; accessing a second CAD model that represents
alignment of cutting block relative to the mobile fiducial marker
array based on the mobile fiducial marker array being attached to
the cutting block; generating an alignment image that represents
alignment of the cutting block to the femur during the TKA
procedure by calculating a three-dimensional transformation between
the co-registered first CAD model of the mobile fiducial marker
array and processed motion capture image and the second CAD model
that represents alignment of cutting block relative to the mobile
fiducial marker array; accessing a design for the TKA procedure
that represents a designed alignment of the cutting block to the
femur in the TKA procedure; comparing the alignment image that
represents alignment of the cutting block to the femur during the
TKA procedure with the design for the TKA procedure; based on
comparison results, determining an indication of precision of
alignment of the cutting block to the femur during the TKA
procedure relative to the designed alignment of the cutting block
to the femur in the TKA procedure; and providing output based on
the determined indication of precision of alignment of the cutting
block to the femur during the TKA procedure relative to the
designed alignment of the cutting block to the femur in the TKA
procedure.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 USC .sctn. 119(e)
to U.S. Provisional Patent Application Ser. No. 62/021,551, filed
Jul. 7, 2014, and entitled "ALIGNMENT PRECISION", the entire
contents of which are hereby incorporated by reference.
FIELD
[0002] This disclosure relates to alignment precision.
BACKGROUND
[0003] Computer Assisted Surgery (CAS) tools have been developed
using optical motion capture to convert three-dimensional (3D)
locations of passive reflective fiducial markers into the 3D pose
of surgical instruments relative to user-selected anatomic landmark
points. CAS may be used as a quantitative intra-operative
measurement system to assess alignment performance. CAS systems,
however, were not designed for rigorous analysis required to
validate intra-operative performance. For example, CAS read-outs
have been commonly limited to 1 mm and 0.5-degree increments of
precision, and absolute accuracy to anatomic landmarks has been
difficult to validate. Also, CAS alignment was limited by the
operator's ability to consistently identify anatomic landmark
points. CAS anatomic landmarks have been limited to those that
could be safely and quickly accessed physically on live patients.
CAS systems were not primarily intended as research tools, but as
tools to assist in a clinical procedure. The level of precision of
CAS systems may be useful for surgeons making informed
intra-operative decisions, but may not be sufficient to distinguish
subtle differences between alignment methods.
SUMMARY
[0004] In one aspect, a system comprises at least one processor and
at least one computer-readable medium coupled to the at least one
processor having stored thereon instructions which, when executed
by the at least one processor, causes the at least one processor to
perform operations. The operations include accessing first image
data of at least a portion of a bone to which a reference fiducial
marker array is fixed in advance of a surgical procedure. The
reference fiducial marker array includes at least three reference
fiducial markers and the first image data is captured using a first
imaging modality that is configured to image the reference fiducial
markers and three-dimensional anatomic landmark data for the
portion of the bone. The operations also include generating a
three-dimensional representation of the portion of the bone and the
reference fiducial markers based on the first image data, defining
a coordinate system for the three-dimensional representation of the
portion of the bone, and determining locations of the reference
fiducial markers relative to the defined coordinate system. The
operations further include accessing intra-operative image data
that includes the portion of the bone to which to the reference
fiducial marker array is fixed and a mobile fiducial marker array
that is attached to an instrument used in the surgical procedure on
the portion of the bone. The mobile fiducial marker array includes
at least three mobile fiducial markers and the intra-operative
image data is captured using a second imaging modality that is
different than the first imaging modality and that is configured to
image the reference fiducial markers and the mobile fiducial
markers. In addition, the operations include co-registering the
intra-operative image data with the three-dimensional
representation of the portion of the bone by matching the reference
fiducial markers included in the intra-operative image data to the
determined locations of the reference fiducial markers relative to
the defined coordinate system. The operations also include
determining locations of the mobile fiducial markers in the
co-registered intra-operative image data and three-dimensional
representation of the portion of the bone and determining a
three-dimensional spatial position and orientation of the
instrument relative to the portion of the bone based on the
determined locations of the mobile fiducial markers. The operations
further include comparing the three-dimensional spatial position
and orientation of the instrument relative to the portion of the
bone with a designed alignment of the instrument to the portion of
the bone and, based on comparison results, determining an
indication of precision of alignment of the instrument in the
surgical procedure on the portion of the bone relative to the
designed alignment of the instrument to the portion of the bone.
The operations also include providing output based on the
determined indication of precision of alignment of the instrument
in the surgical procedure relative to the designed alignment of the
instrument.
[0005] Implementations may include one or more of the following
features. For example, the operations may include accessing
computed tomography (CT) image data of the portion of the bone and
the reference fiducial markers and accessing intra-operative motion
capture data that includes the portion of the bone to which to the
reference fiducial marker array is fixed and the mobile fiducial
marker array that is attached to the instrument used in the
surgical procedure on the portion of the bone. In addition, the
operations may include generating a three-dimensional solid that
includes the portion of the bone and the reference fiducial marker
array.
[0006] In some implementations, the operations may include
accessing data defining three-dimensional spatial position and
orientation of the instrument relative to the mobile fiducial
markers determined using a computer-aided-design (CAD) model of the
instrument with the mobile fiducial marker array attached. In these
implementations, the operations may include determining the
three-dimensional spatial position and orientation of the
instrument relative to the portion of the bone by mapping the
three-dimensional spatial position and orientation of the
instrument relative to the mobile fiducial markers to the
determined locations of the mobile fiducial markers.
[0007] Also, the operations may include accessing data defining
three-dimensional spatial position and orientation of the
instrument relative to the mobile fiducial markers determined using
a coordinate measurement machine (CMM) evaluation of the instrument
with the mobile fiducial marker array attached. The operations
further may include determining the three-dimensional spatial
position and orientation of the instrument relative to the portion
of the bone by mapping the three-dimensional spatial position and
orientation of the instrument relative to the mobile fiducial
markers to the determined locations of the mobile fiducial
markers.
[0008] In some examples, the operations may include accessing CMM
data for the reference fiducial marker array and validating the
determined locations of the reference fiducial markers using the
accessed CMM data for the reference fiducial marker array. In these
examples, the operations may include accessing CMM data for the
mobile fiducial marker array and validating the determined
locations of the mobile fiducial markers using the accessed CMM
data for the mobile fiducial marker array.
[0009] In some implementations, the reference fiducial markers and
the mobile fiducial markers may be radio-opaque, infrared
reflective spherical markers. In these implementations, the
reference fiducial marker array may include at least five reference
spherical markers and the mobile fiducial marker array may include
at least five mobile spherical markers. Also, in these
implementations, the operations may include determining centers of
the reference spherical markers and determining locations of the
reference fiducial markers as the determined centers of the
reference spherical markers. Further, in these implementations, the
operations may include determining centers of the mobile spherical
markers and determining locations of the mobile fiducial markers as
the determined centers of the mobile spherical markers.
[0010] In some examples, the operations may include identifying the
reference spherical markers, regression fitting each of the
identified reference spherical markers with an ideal sphere shape,
and determining locations of the reference spherical markers using
the regression-fitted reference spherical markers. In these
examples, the operations may include identifying the mobile
spherical markers, regression fitting each of the identified mobile
spherical markers with an ideal sphere shape, and determining
locations of the mobile spherical markers using the
regression-fitted reference spherical markers.
[0011] In some implementations, the operations may include
identifying a measurement for cartilage related to the portion of
the bone and adjusting the three-dimensional representation and the
coordinate system to account for the identified measurement for
cartilage related to the portion of the bone. In these
implementations, the operations may include accessing magnetic
resonance imaging (MRI) of the portion of the bone and determining
a measurement of the cartilage based on the MRI of the portion of
the bone.
[0012] In some examples, the instrument used in the surgical
procedure may be a cutting block used in total knee arthroplasty
(TKA). In these examples, the mobile fiducial marker array may be
attached to the cutting block through the cutting slot of the
cutting block and at least one other portion of the cutting block.
Also, in these examples, the mobile fiducial marker array may be
attached to the cutting block through the cutting slot of the
cutting block and at least one pin hole of the cutting block.
Further, in these examples, the mobile fiducial marker array may be
attached to the cutting block through the cutting slot using a
surgical blade designed to be inserted through the cutting slot and
one or more shims that rigidly support the surgical blade in the
cutting slot.
[0013] In addition, the operations may include accessing data
descriptive of post-operative validation of cuts made during the
surgical procedure and validating the determined indication of
precision of alignment based on the accessed data descriptive of
post-operative validation of cuts made during the surgical
procedure.
[0014] In some implementations, the operations may include
aggregating the determined indication of precision of alignment of
the instrument in the surgical procedure relative to the designed
alignment of the instrument with similar data determined from other
similar surgical procedures. In these implementations, the
operations may include performing statistical analysis of the
aggregated data, determining a representation of general alignment
precision in surgical procedures included in the aggregated data
based on the statistical analysis of the aggregated data, and
providing output indicating the determined representation of
general alignment precision.
[0015] In another aspect, a method includes accessing first image
data of at least a portion of a bone to which a reference fiducial
marker array is fixed in advance of a surgical procedure. The
reference fiducial marker array includes at least three reference
fiducial markers and the first image data is captured using a first
imaging modality that is configured to image the reference fiducial
markers and three-dimensional anatomic landmark data for the
portion of the bone. The method also includes generating a
three-dimensional representation of the portion of the bone and the
reference fiducial markers based on the first image data, defining
a coordinate system for the three-dimensional representation of the
portion of the bone, and determining locations of the reference
fiducial markers relative to the defined coordinate system. The
method further includes accessing intra-operative image data that
includes the portion of the bone to which to the reference fiducial
marker array is fixed and a mobile fiducial marker array that is
attached to an instrument used in the surgical procedure on the
portion of the bone. The mobile fiducial marker array includes at
least three mobile fiducial markers and the intra-operative image
data is captured using a second imaging modality that is different
than the first imaging modality and that is configured to image the
reference fiducial markers and the mobile fiducial markers. In
addition, the method includes co-registering the intra-operative
image data with the three-dimensional representation of the portion
of the bone by matching the reference fiducial markers included in
the intra-operative image data to the determined locations of the
reference fiducial markers relative to the defined coordinate
system. The method also includes determining locations of the
mobile fiducial markers in the co-registered intra-operative image
data and three-dimensional representation of the portion of the
bone and determining a three-dimensional spatial position and
orientation of the instrument relative to the portion of the bone
based on the determined locations of the mobile fiducial markers.
The method further includes comparing the three-dimensional spatial
position and orientation of the instrument relative to the portion
of the bone with a designed alignment of the instrument to the
portion of the bone and, based on comparison results, determining
an indication of precision of alignment of the instrument in the
surgical procedure on the portion of the bone relative to the
designed alignment of the instrument to the portion of the bone.
The method includes providing output based on the determined
indication of precision of alignment of the instrument in the
surgical procedure relative to the designed alignment of the
instrument.
[0016] In yet another aspect, at least one computer-readable
storage medium encoded with executable instructions that, when
executed by at least one processor, cause the at least one
processor to perform operations. The operations include accessing
first image data of at least a portion of a bone to which a
reference fiducial marker array is fixed in advance of a surgical
procedure. The reference fiducial marker array includes at least
three reference fiducial markers and the first image data is
captured using a first imaging modality that is configured to image
the reference fiducial markers and three-dimensional anatomic
landmark data for the portion of the bone. The operations also
include generating a three-dimensional representation of the
portion of the bone and the reference fiducial markers based on the
first image data, defining a coordinate system for the
three-dimensional representation of the portion of the bone, and
determining locations of the reference fiducial markers relative to
the defined coordinate system. The operations further include
accessing intra-operative image data that includes the portion of
the bone to which to the reference fiducial marker array is fixed
and a mobile fiducial marker array that is attached to an
instrument used in the surgical procedure on the portion of the
bone. The mobile fiducial marker array includes at least three
mobile fiducial markers and the intra-operative image data is
captured using a second imaging modality that is different than the
first imaging modality and that is configured to image the
reference fiducial markers and the mobile fiducial markers. In
addition, the operations include co-registering the intra-operative
image data with the three-dimensional representation of the portion
of the bone by matching the reference fiducial markers included in
the intra-operative image data to the determined locations of the
reference fiducial markers relative to the defined coordinate
system. The operations also include determining locations of the
mobile fiducial markers in the co-registered intra-operative image
data and three-dimensional representation of the portion of the
bone and determining a three-dimensional spatial position and
orientation of the instrument relative to the portion of the bone
based on the determined locations of the mobile fiducial markers.
The operations further include comparing the three-dimensional
spatial position and orientation of the instrument relative to the
portion of the bone with a designed alignment of the instrument to
the portion of the bone and, based on comparison results,
determining an indication of precision of alignment of the
instrument in the surgical procedure on the portion of the bone
relative to the designed alignment of the instrument to the portion
of the bone. The operations also include providing output based on
the determined indication of precision of alignment of the
instrument in the surgical procedure relative to the designed
alignment of the instrument.
[0017] In yet another aspect, a method includes accessing an MRI
image of at least a portion of a cadaver patient's leg that
includes a knee of the cadaver patient and determining cartilage
thickness for the knee of the cadaver patient based on the accessed
MRI image. The method also includes accessing a CT image of at
least a portion of the cadaver patient's leg that includes CT
imaging of at least a portion of a femur to which a reference
fiducial marker array is fixed in advance of a TKA procedure and CT
imaging of at least a portion of a tibia. The reference fiducial
marker array includes at least three reference fiducial markers
that are captured in CT imaging and motion capture imaging. The
method further includes defining, on the accessed CT image and
accounting for the determined cartilage thickness, a first
coordinate system for the femur and a second coordinate system for
the tibia and generating a processed CT image by calculating a
three-dimensional transformation between the CT image on which the
first coordinate system for the femur and the second coordinate
system for the tibia have been defined and a pattern of the
reference fiducial marker array as measured by the CT image. In
addition, the method includes accessing intra-operative motion
capture data of at least a portion of the cadaver patient's leg
that includes motion capture imaging of at least a portion of the
femur to which the reference fiducial marker array is fixed and
motion capture imaging of at least a portion of the tibia. The
intra-operative motion capture data is captured during the TKA
procedure on the cadaver patient's leg and includes motion capture
imaging of a mobile fiducial marker array that is attached to a
cutting block used in the TKA procedure on the cadaver patient's
leg. The mobile fiducial marker array includes at least three
mobile fiducial markers that are captured in motion capture
imaging. The method also includes co-registering the
intra-operative motion capture data with the processed CT image by
regression fitting the reference fiducial markers included in the
intra-operative motion capture data to the reference fiducial
markers included in the processed CT image. The method further
includes generating a processed motion capture image by calculating
a three-dimensional transformation between the co-registered
intra-operative motion capture data and processed CT image and a
pattern of the mobile fiducial marker array as measured by the
intra-operative motion capture data. And, the method includes
accessing a first CAD model of the mobile fiducial marker array and
co-registering the first CAD model of the mobile fiducial marker
array with the processed motion capture image by regression fitting
the mobile fiducial markers included in the first CAD model of the
mobile fiducial marker array to the mobile fiducial markers
included in the processed motion capture image. The method includes
accessing a second CAD model that represents alignment of cutting
block relative to the mobile fiducial marker array based on the
mobile fiducial marker array being attached to the cutting block
and generating an alignment image that represents alignment of the
cutting block to the femur during the TKA procedure by calculating
a three-dimensional transformation between the co-registered first
CAD model of the mobile fiducial marker array and processed motion
capture image and the second CAD model that represents alignment of
cutting block relative to the mobile fiducial marker array. The
method includes accessing a design for the TKA procedure that
represents a designed alignment of the cutting block to the femur
in the TKA procedure, comparing the alignment image that represents
alignment of the cutting block to the femur during the TKA
procedure with the design for the TKA procedure, and, based on
comparison results, determining an indication of precision of
alignment of the cutting block to the femur during the TKA
procedure relative to the designed alignment of the cutting block
to the femur in the TKA procedure. In addition, the method includes
providing output based on the determined indication of precision of
alignment of the cutting block to the femur during the TKA
procedure relative to the designed alignment of the cutting block
to the femur in the TKA procedure.
[0018] The details of one or more implementations are set forth in
the accompanying drawings and the description, below. Other
potential features of the disclosure will be apparent from the
description and drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a diagram of example inter-operative process
control.
[0020] FIG. 2 is a diagram of example inter-operative alignment
process control.
[0021] FIGS. 3 and 14 are diagrams of example systems.
[0022] FIGS. 4, 12, and 13 are flowcharts of example processes.
[0023] FIG. 5 is a diagram of an example assembly of a subject
bone, a subject instrument, a bone rig, an instrument rig, a
reference fiducial marker array, and a mobile fiducial marker
array.
[0024] FIGS. 6-9 are diagrams illustrating example alignment axes
for bone segments.
[0025] FIGS. 10 and 11 are diagrams illustrating example
co-registered and overlaid pre- and post-operative images.
DETAILED DESCRIPTION
[0026] Techniques are described for a system of combined
high-precision imaging methods used to compare intra-operative
alignment performance of total knee arthroplasty (TKA)
instrumentation and techniques to pre-operatively determine
alignment targets. These imaging methods acquire and process
three-dimensional (3D) data of two types: pre-operative anatomic
landmark data and intra-operative motion data. The former are used
to establish the pre-operative alignment axes of the subject bone,
and the latter establish the 3D spatial position and orientation
(e.g., pose) of the subject instrument during use relative to the
pre-operative alignment. Each imaging method may be
non-destructively validated to pre-operative Coordinate Measurement
Machine (CMM) gauge data for each test setup. The CMM data may be
obtained by contact measurement or non-contact scanning. The system
of the two imaging methods also may be destructively validated by
comparing intra-operative and post-operative measurements of the
TKA resection surfaces for each test setup.
[0027] In some implementations, this type of analysis may be
challenging because few tools can simultaneously acquire both
landmark and motion data. Further, a high level of precision and
accuracy may be required to detect small performance differences. A
single method, such as a Computer Aided Surgery (CAS) machine,
which intra-operatively captures both anatomic landmarks and 3D
pose data, may be used. Although CAS streamlines data acquisition,
CAS may have insufficient precision and accuracy for validation
testing. To improve precision and accuracy, in some examples, two,
different modalities of high precision imaging may be used and
co-registered to assess alignment performance. For instance, a
system may use multi-modality fiducial marker arrays to co-register
two specialized high-precision measurement methods. This system may
involve Computed Tomography (CT) imaging for pre-operative anatomic
landmark data and optical motion capture (e.g., ProReflex motion
capture technology provided by Qualisys AB) for 3D intra-operative
instrument pose data. ProReflex is a registered trademark of
Qualisys AB.
[0028] Using the techniques described throughout this disclosure,
precision of a patient matched design process for TKA procedures
may be validated and improved. In some implementations, the
techniques described throughout this disclosure may be used in a
cadaver study to validate and improve precision of the patient
matched design process. In these implementations, many cadavers may
be selected that have similar anatomic features at the knee joint.
Then, for each cadaver, a surgical team performs a patient matched
process to assess alignment precision in TKA procedures.
[0029] In the patient matched process to assess alignment precision
in TKA procedures, the surgical team uses the patient matched
design process to generate an implant design for the cadaver. Next,
the surgical team assembles a bone rig with a reference fiducial
marker array to the cadaver's bone (e.g., femur and/or tibia) and
performs pre-operative imaging (e.g., MRI, CT, etc.) to generate a
representation of the cadaver's bone relative to the reference
fiducial marker array prior to the TKA procedure.
[0030] After the pre-operative imaging, the surgical team
transports the cadaver to a surgical center and performs the TKA
procedure on the cadaver while capturing motion capture imaging of
the TKA procedure. The motion capture imaging captures the
reference fiducial marker array and a mobile fiducial marker array
that is attached to an instrument (e.g., cutting block) used in the
TKA procedure. The motion capture imaging is co-registered with the
pre-operative imaging using the reference fiducial marker array
and, using a known alignment of the mobile fiducial marker array to
the instrument, an alignment of the instrument to the bone during
the TKA procedure is determined.
[0031] Then, the determined alignment of the instrument to the bone
during the TKA procedure is compared to a designed alignment
included in the implant design for the cadaver. The comparison
provides a measure of how precisely the actual alignment meets the
designed alignment. Because many cadavers were selected for the
testing, the precision of the patient matched design process may be
validated using statistical analysis. In addition, the surgical
team may make recommendations on how to improve the patient matched
design process and identify places that introduce error in
alignment.
[0032] FIG. 1 illustrates an example of inter-operative process
control 100. In the example process control 100, a system accesses
pre-operative data 110. The pre-operative data may include image
data of a bone or bone segment (e.g., CT image data, MRI image
data, and/or other types of image data). The system performs a
pre-operative device design process 120 based on the accessed
pre-operative data. For example, the system may develop a
patient-specific instrument design based on the accessed
pre-operative data. In this example, the system may develop a
patient-specific implant and a patient-specific cutting block that
is adapted to the specific anatomy of the patient's bone. In other
examples, the system uses the accessed pre-operative data to
select, from a library of available designs, an instrument design
that best matches the patient's anatomy.
[0033] In addition, the system monitors intra-operative use of
device 130 using an inter-operative measurement system 140. For
instance, the system monitors surgical placement of the designed
device during a surgical procedure. The system may use motion
capture data to monitor the pose of the designed device during the
surgical procedure. The system may focus on the final placement of
the designed device to determine the final alignment of the
designed device.
[0034] The system also may access post-operative data 150 related
to the accuracy and precision of the surgical procedure. The
post-operative data 150 may include non-destructive validation
measurements using imaging technology on the final resection cuts
and/or implant placement. The post-operative data 150 also may
include destructive validation measurements using physical
measurement techniques (e.g., caliper measurements) on the final
resection cuts and/or implant placement. The destructive validation
measurements may be used when the surgical procedure is performed
on a cadaver for the purpose of researching alignment precision of
the alignment technique used in designing the device and performing
the surgical procedure.
[0035] The inter-operative measurement system 140 uses
pre-operative design data from the pre-operative device design
process 120 and the post-operative data 150 to assess alignment
precision during the surgical procedure. For example, the
inter-operative measurement system 140 compares the pre-operative
design and the post-operative data 150 to determine how closely the
actual alignment of the designed device in the surgical procedure
matched the designed alignment. The inter-operative measurement
system 140 may use any of the techniques described throughout this
disclosure to assess alignment precision (e.g., the process 400
described below with respect to FIG. 4).
[0036] The inter-operative measurement system 140 uses the results
of the precision analysis, as well as other available data, to
continuously improve all aspects of the surgical procedure. For
example, the output of the inter-operative measurement system 140
may be used to improve the pre-operative data 110 captured, improve
the pre-operative device design process 120, and/or improve the
intra-operative use of device 130. In this example, the
inter-operative measurement system 140 may monitor data over a
large number of research procedures, identify factors that impact
alignment performance, and use the identified factors to improve
alignment in the overall process.
[0037] The inter-operative measurement system 140 may produce and
output data product(s) to customer(s) 160. The data product(s) to
customer(s) 160 may include accuracy precision in alignment for a
single procedure and/or statistical analysis of a large number of
procedures that indicate general alignment precision of a specific
alignment process. The statistical analysis may include F and/or T
tests that quantitatively indicate the alignment performance over a
large number of sample procedures.
[0038] FIG. 2 illustrates an example of inter-operative alignment
process control 200. The inter-operative alignment process control
200 is similar to the inter-operative process control 100, but
provides additional details. In the example alignment process
control 200, a system accesses pre-operative data 210. The
pre-operative data may include pre-operative knee MRI and full leg
coronal XRay and knee sagittal XRay.
[0039] The inter-operative alignment process control 200 shows
additional operations performed in the pre-operative device design
process 120. As shown, the system establishes landmarks in MRI and
XRays 220, registers XRays to unaligned pre-op MRI bone 222, and
establishes bone alignment 224. The system then applies surgeon
alignment offsets to alignment axes/points 226 and accesses design
rules 228 that are continuously improved by the inter-operative
measurement system 140. The system inputs implant variables and
surgeon aligned anatomy into the accessed block design rules 230,
generates resection device manufacturing (MFG) files 232, and
generates an alignment pre-operative plan 233.
[0040] The generated resection device MFG files 232 are used to
implement intra-operative use of device 130. As part of the
intra-operative use of device 130, the system manufactures the
device 234 and causes the delivery of the manufactured device 236
for surgery. A surgeon applies a surgical technique 238 with the
manufactured device and uses the device to align resection 240 in
the surgical procedure.
[0041] After the surgical procedure, the system obtains
post-operative data 242. The post-operative data 242 may include
full leg coronal XRay and knee sagittal XRay.
[0042] The inter-operative measurement system 140 receives the
alignment pre-operative plan 233 and the post-operative data 242
for comparison. The system establishes landmarks in XRays 244, uses
the established landmarks to register post-operative XRays to
implant models 246, and uses the established landmarks to register
XRays to aligned pre-operative MRI bone 248. The system 140 then
uses the registered post-operative XRays to implant models and the
registered XRays to the aligned pre-operative MRI bone to compare
pre-operative plan versus post-operative result 250. The comparison
of the pre-operative plan versus post-operative result 250 results
in data that indicates alignment precision in the surgical
procedure. The data may indicate alignment precision at each
resection cut and/or at various points of the aligned device. In
addition, the system 140 may perform statistical analysis on a
large number of test cases as described above with respect to FIG.
1. The system 140 may use the results of the comparison to
continuously improve all aspects of the alignment design and
process.
[0043] The system 140 provides and outputs data product(s) to
customer(s) 252 based on the comparison. The system 140 may use
techniques similar to those discussed above with respect to FIG. 1
to provide and output data product(s) to customer(s) 252. Although
the discussion in FIGS. 1 and 2 focus on alignment process
controls, the techniques described in FIGS. 1 and 2 (and
throughout) may be applied to other process controls.
[0044] FIG. 3 illustrates an example alignment measurement system
300, which may be used as the system referenced above with respect
to FIGS. 1 and 2. The system 300 includes an input module 310, a
data store 320, one or more processors 330, one or more I/O
(Input/Output) devices 340, and memory 350. The input module 320
may be used to input any type of information used in alignment
measurement and process control. For example, the input module 310
may be used to receive bone data and images of bone segments both
pre- and post-operative. In some implementations, data from the
input module 310 is stored in the data store 320. The data included
in the data store 320 may include, for example, any type of
alignment or process control related data (e.g., bone images,
three-dimensional models of bones, parameters related to instrument
designs, etc.).
[0045] In some examples, the data store 320 may be a relational
database that logically organizes data into a series of database
tables. Each database table in the data store 320 may arrange data
in a series of columns (where each column represents an attribute
of the data stored in the database) and rows (where each row
represents attribute values). In some implementations, the data
store 320 may be an object-oriented database that logically or
physically organizes data into a series of objects. Each object may
be associated with a series of attribute values. In some examples,
the data store 320 may be a type of database management system that
is not necessarily a relational or object-oriented database. For
example, a series of XML (Extensible Mark-up Language) files or
documents may be used, where each XML file or document includes
attributes and attribute values. Data included in the data store
320 may be identified by a unique identifier such that data related
to a particular process may be retrieved from the data store
320.
[0046] The processor 330 may be a processor suitable for the
execution of a computer program such as a general or special
purpose microprocessor, and any one or more processors of any kind
of digital computer. In some implementations, the system 300
includes more than one processor 330. The processor 330 may receive
instructions and data from the memory 350. The memory 350 may store
instructions and data corresponding to any or all of the components
of the system 300. The memory 350 may include read-only memory,
random-access memory, or both.
[0047] The I/O devices 340 are configured to provide input to and
output from the system 300. For example, the I/O devices 340 may
include a mouse, a keyboard, a stylus, a camera, or any other
device that allows the input of data. The I/O devices 340 may also
include a display, a printer, or any other device that outputs
data.
[0048] FIG. 4 illustrates a process 400 used in alignment precision
measurement. The operations of the process 400 are described
generally as being performed by the system 300. In some
implementations, operations of the process 400 may be performed by
one or more processors included in one or more electronic
devices.
[0049] In some implementations, the process 400 is performed on
cadaver patients to assess the alignment precision in
patient-matched design processes used in performing a surgical
procedure. In these implementations, the results and output
provided by the process 400 are used to validate the precision of
the patient-matched design processes on the cadaver patients and
improve the patient-matched design processes used in future live
patients, where assembling the bone rig to enable image
registration in multiple imaging modalities would not be
performed.
[0050] The system 300 accessing pre-operative image data of at
least a portion of a bone to which a reference fiducial marker
array is fixed (405). The reference fiducial marker array may
include at least three reference fiducial markers and the
pre-operative image data may be captured using a first imaging
modality that is configured to image the reference fiducial markers
and three-dimensional anatomic landmark data for the portion of the
bone. For instance, the system 300 accesses pre-operative computed
tomography (CT) image data of the portion of the bone and the
reference fiducial markers. The system 300 may control the CT
imaging system to capture images of the portion of the bone and the
reference fiducial markers and access the CT images as the
pre-operative image data. Other types of imaging technologies
(e.g., three-dimensional imaging technologies that are capable of
capturing a three-dimensional image of bone) may be used.
[0051] In implementations in which the techniques described
throughout this disclosure are used in knee implants (e.g., TKA),
the system 300 accesses pre-operative image data of at least a
portion of a femur and/or a tibia. For instance, the system 300 may
access pre-operative image data of an entire femur or tibia, or may
access pre-operative image data of a portion of the femur or tibia
located at the knee joint (e.g., the portion of the femur or tibia
that receives an implant during TKA). In addition, the techniques
described throughout this disclosure may be applied to other types
of implant procedures (e.g., hip replacement, shoulder replacement,
etc.). For other types of implant procedures, the system 300 may
access pre-operative image data of a portion of the bone that
receives the implant, such as a portion of the bone located at a
joint associated with the implant procedure.
[0052] FIG. 5 illustrates an example assembly of a subject bone, a
subject instrument, a bone rig, an instrument rig, a reference
fiducial marker array, and a mobile fiducial marker array. As shown
in FIG. 5, multiple spherical fiducial markers are rigidly attached
to a small rectangular frame to form a fiducial marker array. Due
to the properties of the spherical markers (e.g., radio-opaque,
infrared reflective), the fiducial marker array is measurable by
both CT imaging and optical motion capture (e.g., ProReflex motion
capture technology provided by Qualisys AB). One array is rigidly
attached to the subject bone during pre-operative imaging and
remains attached during intra-operative testing in order to serve
as a fixed datum reference between the CT image of subject bone and
the motion capture measured subject instrument 3D pose. Therefore,
this array may be referred to as the reference CT-Qualisys-Fiducial
Marker Array (CT-Q-FMA). A second array is rigidly attached to the
subject instrument during intra-operative testing, thereby enabling
measurement of the 3D pose of the subject instrument with respect
to the reference CT-Q-FMA. This second array may be referred to as
the mobile Q-FMA.
[0053] The reference CT-Q-FMA frame may be composed of CT and MR
compatible Objet Digital ABS Polyjet Photopolymer RGD515/535 and
manufactured on an Objet Connex 500 3D Printer. The spherical
multi-modality markers used in the reference CT-Q-FMA may be
constructed from a CT and MR compatible, radio-opaque plastic
coated with an infrared reflective paint. The manufacturing of the
reference CT-Q-FMA may not affect measurement precision so long as
the shape of the reference CT-Q-FMA remains constant throughout use
of the measurement system. The manufacture of the mobile Q-FMA may
bias measurement system results.
[0054] In some examples, a bone rig designed to rigidly connect the
reference CT-Q-FMA to the subject bone is manufactured. As shown in
FIG. 5, the bone rig is intended to provide a stable relationship
between the reference CT-Q-FMA and the subject bone during and
between measurements. The bone rig may be composed of CT and MR
compatible Objet Digital ABS Polyjet Photopolymer RGD515/535 and
may be manufactured on an Objet Connex 500 3D Printer. The
manufacture of the bone rig may not affect the measurement system
so long as it is able to provide a stable, constant relationship
between the Reference CT-Q-FMA and the subject bone throughout use
of the measurement system.
[0055] In addition, an instrument rig may be used to rigidly
connect the mobile Q-FMA and the subject instrument. The instrument
rig positions the mobile Q-FMA according to a pre-determined pose
with respect to the subject instrument in order to represent the
subject instrument in 3D space. The manufacture of the instrument
rig may bias measurement system results.
[0056] In some examples, subject instrumentation is manufactured
and inspected according to certain specifications. Part numbers and
quantities involved in each case may vary. In these examples, the
manufacture of the subject instrument contributes to the
measurement result. Any influence which the manufacturing process
may have on intra-operative alignment is captured within the
measurement results
[0057] For pre-imaging assembly, the bone rig is assembled to the
subject bone. Aluminum hardware may be used to rigidly attach the
Bone Rig to the subject bone in order to be MR and CT compatible
and reduce (e.g., minimize) potential of imaging distortion. For
instance, two 1/4-20 threaded aluminum rods and lock nuts may be
positioned and spaced on the subject bone in order to increase
(e.g., maximize) stability and reduce (e.g., minimize) the
potential of imaging distortion in the proximal and distal
epiphyses of the subject bone.
[0058] In some implementations, the assembly is designed to
maintain a constant relationship with the subject bone and
precautions are taken throughout use of the measurement system to
preserve that relationship particularly during transport of the
patient (e.g., cadaveric specimen used for testing). Bone rig shift
relative to the subject bone between or during measurements may
bias measurement system results. Zero shift between the bone rig
and the subject bone may be assumed throughout use of the
measurement system, but shift may be measured post-operatively to
confirm and adjust measurements as needed.
[0059] To assemble the reference CT-Q-FMA to the bone rig, nylon
hardware may be used in order to be CT and MR compatible and reduce
(e.g., avoid) image distortion. The assembly may be designed to
maintain a constant relationship with the subject bone and
precautions may be taken between and during measurement methods to
preserve that relationship particularly during transport of the
patient (e.g., cadaveric specimen used for testing). Reference
CT-Q-FMA shift relative to the subject bone between or during
measurements may bias measurement system results. Zero shift
between the reference CT-Q-FMA and the subject bone may be assumed
throughout use of the measurement system, but shift may be measured
post-operatively and accounted for in the final measurement
results.
[0060] In addition, to CT pre-operative imaging, the portion of the
bone (e.g., knee area) is MR imaged with fat-saturation. The
fat-saturated MR image is intended to provide a measurement of the
articular cartilage thickness, which is absent in the processed CT
image. The scan settings are set to be appropriate (per the implant
design tool's imaging protocol) for the machine used. The
fat-saturation setting is turned on. A deficiency of the
fat-saturated MR image may affect measurement system precision.
[0061] In some examples, the mean value of the measured cartilage
thickness is validated to the literature. MRI machine calibration
records defined by the supplier of the MR image may be accessed to
account for measurement variation.
[0062] The subject bone and reference CT-Q-FMA then may be CT
imaged. The following scan settings may be used to generate a
sufficient (e.g., optimized) CT image for processing: --25 cm FOV,
--0.625 mm helical slice thickness, --0.562 mm helical slice pitch,
and --135 mA tube current optimized for bone.
[0063] The system 300 treats the CT image of the subject bone and
reference CT-Q-FMA as being accurate. CT machine calibration
records defined by the supplier of the CT image technology may be
accessed to account for imaging variation.
[0064] With the assembly shown in FIG. 5, the system may implement
a hybrid measurement system which takes advantage of the most
accurate pre-operative and intra-operative imaging methods. CT is
an accurate imaging tool available to assess anatomic landmarks for
use in bone alignment. CT also broadened and enhanced access to
bony anatomy when establishing pre-operative alignment targets.
Passive reflective markers were still used for intra-operative 3D
pose measurement, but optical motion capture measurements were less
noisy due to the addition of redundant cameras and markers. The
Qualisys ProReflex optical motion cameras used are capable of
measuring with micrometer precision. In order to validate that each
imaging measurement method was properly calibrated to physical
measurements, CMM data may be used to gauge the residual error of
the fiducial markers for each method.
[0065] In some implementations, independent data from each method
is co-registered by matching the reference array of fiducial
markers detectable by each of the CT, Qualisys and CMM measurement
methods. In these implementations, the reference CT-Q-FMA is
rigidly affixed to the subject bone and serves as a reference datum
between the pre-operative CT and the intra-operative Qualisys
measurements. Because of the role of the reference CT-Q-FMA to the
measurement system, it allows independent validation of both CT and
Qualisys data to physical CMM measurements. Additionally,
intra-operative Qualisys measurements of the resection surface
alignment may be validated to match the post-operative CT measured
resection surface.
[0066] The quality and quantity of data afforded by this hybrid
measurement system may improve understanding and ultimately the
capability of surgical resection manufacture by design.
Accordingly, the techniques described throughout this disclosure
may be used to confirm precision of current design processes and
may be used to improve design processes in the future.
[0067] Referring again to FIG. 4, the system 300 generates a
three-dimensional representation of the portion of the bone and the
reference fiducial markers based on the pre-operative image data
(410). For example, the system 300 generates a three-dimensional
solid that includes the portion of the bone and the reference
fiducial marker array. In implementations in which the techniques
described throughout this disclosure are used in knee implants
(e.g., TKA), the system 300 may generate a three-dimensional
representation of at least a portion of a femur and/or a tibia. For
instance, the system 300 may generate a three-dimensional
representation of an entire femur or tibia, or may generate a
three-dimensional representation of a portion of the femur or tibia
located at the knee joint (e.g., the portion of the femur or tibia
that receives an implant during TKA). In addition, the techniques
described throughout this disclosure may be applied to other types
of implant procedures (e.g., hip replacement, shoulder replacement,
etc.). For other types of implant procedures, the system 300 may
generate a three-dimensional representation of a portion of the
bone that receives the implant, such as a portion of the bone
located at a joint associated with the implant procedure.
[0068] In some examples, the system 300 may account for cartilage
in generating the three-dimensional representation of the portion
of the bone. In these examples, the system 300 identifies a
measurement for cartilage related to the portion of the bone and
adjusts the three-dimensional representation and the coordinate
system to account for the identified measurement for cartilage
related to the portion of the bone. The system 300 may make an
assumption of cartilage thickness based on historical data (e.g.,
literature on average cartilage thickness for the joint at issue).
In addition, the system 300 measure the cartilage thickness by
accessing magnetic resonance imaging (MRI) of the portion of the
bone and determining a measurement of the cartilage based on the
MRI of the portion of the bone.
[0069] In processing images to generate the three-dimensional
representation, the system 300 may segment the CT image of the
subject bone and reference CT-Q-FMA to create a processed CT image
using an appropriate software application (e.g., MIMICS software).
The system 300 may treat the processed CT image of the subject bone
and reference CT-Q-FMA as accurate. The processed CT image of the
subject bone and reference CT-Q-FMA may be validated by comparison
to CMM measurement of the reference CT-Q-FMA.
[0070] The system 300 defines a coordinate system for the
three-dimensional representation of the portion of the bone (415)
and determines locations of the reference fiducial markers relative
to the defined coordinate system (420). The system 300 may define
the coordinate system based on user input and/or automated
processing. For instance, the system 300 may define the coordinate
system based on a user providing user input placing a coordinate
axis framework on a portion of the bone. Also, the system 300 may
define the coordinate system automatically by identifying one or
more landmarks on the portion of the bone and defining the
coordinate system relative to the one or more identified
landmarks.
[0071] The system 300 may define the coordinate system at any
position and orientation of the bone as long as the coordinate
system enables measurements of locations of the fiducial markers
and co-registration of the multiple modalities of imaging
technology, discussed in more detail below. For example, in TKA,
the femur mechanical axis may be established using proximal and
distal mechanical points defined by the centers of the proximal and
distal joints and the femur mechanical axis may be defined as the
Z-axis of the femur coordinate system. In this example, the tibia
mechanical axis may be established using proximal and distal
mechanical points defining the centers of the proximal and distal
joints and the tibia mechanical axis may be defined as the Z-axis
of the tibia coordinate system.
[0072] After defining the coordinate system, the system 300
determines locations of the fiducial markers in terms of the
defined coordinate system. For example, the reference fiducial
markers may be radio-opaque, infrared reflective spherical markers
and the reference fiducial marker array may include at least five
reference spherical markers. In this example, the system 300
determines a location for each of the at least five reference
spherical markers. In determining locations, the system 300 may
determine centers of the reference spherical markers and may
determine locations of the reference fiducial markers as the
determined centers of the reference spherical markers. In addition,
the system 300 may identify the reference spherical markers,
regression fit each of the identified reference spherical markers
with an ideal sphere shape, and determine locations of the
reference spherical markers using the regression-fitted reference
spherical markers.
[0073] In some implementations, the system 300 validates the
determined locations of the reference fiducial markers. In these
implementations, the system 300 may access CMM data for the
reference fiducial marker array and validate the determined
locations of the reference fiducial markers using the accessed CMM
data for the reference fiducial marker array. The validation may
involve a comparison of the relative locations of the reference
fiducial markers in the CMM data against the relative locations of
the reference fiducial markers as determined using the image data.
The system 300 may continue processing if the comparison reveals
that the determined locations are within a threshold of the
expected locations. If the comparison reveals that the determined
locations are outside of a threshold of the expected locations, the
imaging system may be recalibrated and the imaging may be
repeated.
[0074] FIGS. 6-9 illustrate example alignment axes for bone
segments. FIGS. 6 and 7 illustrate multiple views of anatomic
alignment axes defined by the system 300 for a femur. The gap
between the coordinate system's origin and the bone represents the
cartilage thickness on the preferred distal condyle. As shown in
FIG. 6, the three-dimensional representation 600 includes an entire
femur with a coordinate system defined with the Z-axis aligning
with a mechanical axis of the femur. FIG. 7 illustrates multiple
views of the three-dimensional representation 600 focused on the
portion of the femur relevant to a TKA procedure. As shown, a first
view 710 illustrates the Z and X axes defined relative to the bone,
a second view 720 illustrates the Z and Y axes defined relative to
the bone, and a third view 730 illustrates the X and Y axes defined
relative to the bone.
[0075] FIGS. 8 and 9 illustrate multiple views of anatomic
alignment axes defined by the system 300 for a tibia. The gap
between the coordinate system's origin and the bone represents the
cartilage thickness at the resection reference point. As shown in
FIG. 8, the three-dimensional representation 800 includes an entire
tibia with a coordinate system defined with the Z-axis aligning
with a mechanical axis of the tibia. FIG. 9 illustrates multiple
views of the three-dimensional representation 800 focused on the
portion of the tibia relevant to a TKA procedure. As shown, a first
view 910 illustrates the Z and X axes defined relative to the bone,
second and third views 920 and 930 illustrate the Z and Y axes
defined relative to the bone, and a fourth view 940 illustrates the
X and Y axes defined relative to the bone.
[0076] Referring again to FIG. 4, the system 300 accesses
intra-operative image data that includes the portion of the bone to
which to the reference fiducial marker array is fixed and a mobile
fiducial marker array that is attached to an instrument used in a
surgical procedure on the portion of the bone (425). The mobile
fiducial marker array may include at least three mobile fiducial
markers and the intra-operative image data may be captured using a
second imaging modality that is different than the first imaging
modality and that is configured to image the reference fiducial
markers and the mobile fiducial markers. For instance, the system
300 may access intra-operative motion capture data that includes
the portion of the bone to which to the reference fiducial marker
array is fixed and the mobile fiducial marker array that is
attached to the instrument used in the surgical procedure on the
portion of the bone.
[0077] In implementations in which the techniques described
throughout this disclosure are used in knee implants (e.g., TKA),
the system 300 accesses intra-operative image data of at least a
portion of a femur and/or a tibia. For instance, the system 300 may
access intra-operative image data of an entire femur or tibia, or
may access pre-operative image data of a portion of the femur or
tibia located at the knee joint (e.g., the portion of the femur or
tibia that receives an implant during TKA). In addition, the
techniques described throughout this disclosure may be applied to
other types of implant procedures (e.g., hip replacement, shoulder
replacement, etc.). For other types of implant procedures, the
system 300 may access intra-operative image data of a portion of
the bone that receives the implant, such as a portion of the bone
located at a joint associated with the implant procedure.
[0078] In TKA implementations, the instrument used in the surgical
procedure may be a cutting block. In these implementations, the
mobile fiducial marker array may be attached to the cutting block
through the cutting slot of the cutting block and at least one
other portion of the cutting block. For instance, the mobile
fiducial marker array may be attached to the cutting block through
the cutting slot of the cutting block and at least one pin hole of
the cutting block. In addition, the mobile fiducial marker array
may be attached to the cutting block through the cutting slot using
a surgical blade designed to be inserted through the cutting slot
and one or more shims that rigidly support the surgical blade in
the cutting slot.
[0079] In terms of non-destructive testing, the mobile Q-FMA may be
used to represent the 3D pose of the subject instrument during
intra-operative motion capture (e.g., ProReflex motion capture
technology provided by Qualisys AB) measurements. The mobile Q-FMA
may be mated to the instrument rig and the instrument rig may be
mated to alignment features of the subject instrument. The
instrument rig may be intended to maintain a pre-determined 3D pose
between the mobile Q-FMA and the subject instrument. Assembly
variation around the pre-determined 3D pose between the mobile
Q-FMA and the subject instrument may affect measurement system
precision and may be accounted for in the results output.
[0080] After mating the instrument rig to alignment features of the
subject instrument, the subject instrument may be physically
aligned to the subject bone. Motion capture (e.g., ProReflex motion
capture technology provided by Qualisys AB) may measure the 3D pose
of the mobile Q-FMA with respect to the reference CT-Q-FMA. For
example, an incision may be made and the subject bone may be
exposed. With the reference CT-Q-FMA and the mobile Q-FMA visible
to the motion capture cameras, the surgical operator aligns the
subject instrument to the subject bone. Once the surgical operator
is confident in the alignment of the subject instrument, the motion
capture cameras capture the 3D pose of the mobile Q-FMA with
respect to the reference CT-Q-FMA. These steps may be repeated as
needed for additional instruments. Precision of the intra-operative
alignment of the subject instrument to the subject bone is a
component of the measurement system result.
[0081] The system 300 co-registers the intra-operative image data
with the three-dimensional representation of the portion of the
bone by matching the reference fiducial markers included in the
intra-operative image data to the determined locations of the
reference fiducial markers relative to the defined coordinate
system (430). For example, the system 300 determines locations of
the reference fiducial markers included in the intra-operative
image data using techniques discussed above with respect to
reference numeral 420. In this example, the system 300 takes the
determined locations of the reference fiducial markers in the
intra-operative image data, matches the determined locations of the
reference fiducial markers in the intra-operative image data to the
determined locations of the reference fiducial markers in the
pre-operative image data, and overlays the intra-operative image
data onto the pre-operative image data based on the matching. To
the extent that the determined locations of the reference fiducial
markers in the intra-operative image data do not exactly match the
determined locations of the reference fiducial markers in the
pre-operative image data, the system 300 evaluates the best fit and
matches the locations in a manner that minimizes the aggregate
differences between the locations. FIG. 12, discussed below,
describes additional details of co-registration in TKA
implementations.
[0082] FIGS. 10 and 11 illustrate example co-registered and
overlaid pre- and post-operative images. FIG. 10 illustrates an
example image 1000 of a tibia and FIG. 11 illustrates an example
image 1100 of a femur. In each of the images 1000 and 1100, the
differences are illustrated by shading.
[0083] Referring again to FIG. 4, the system 300 determines
locations of the mobile fiducial markers in the co-registered
intra-operative image data and three-dimensional representation of
the portion of the bone (435). The system 300 may determine
locations of the fiducial markers in terms of the defined
coordinate system. For example, the mobile fiducial markers may be
radio-opaque, infrared reflective spherical markers and the mobile
fiducial marker array may include at least five reference spherical
markers. In this example, the system 300 determines a location for
each of the at least five mobile spherical markers. In determining
locations, the system 300 may determine centers of the mobile
spherical markers and may determine locations of the mobile
fiducial markers as the determined centers of the mobile spherical
markers. In addition, the system 300 may identify the mobile
spherical markers, regression fit each of the identified mobile
spherical markers with an ideal sphere shape, and determine
locations of the mobile spherical markers using the
regression-fitted mobile spherical markers.
[0084] In some implementations, the system 300 validates the
determined locations of the mobile fiducial markers. In these
implementations, the system 300 may access CMM data for the mobile
fiducial marker array and validate the determined locations of the
mobile fiducial markers using the accessed CMM data for the mobile
fiducial marker array. The validation may involve a comparison of
the relative locations of the mobile fiducial markers in the CMM
data against the relative locations of the mobile fiducial markers
as determined using the image data. The system 300 may continue
processing if the comparison reveals that the determined locations
are within a threshold of the expected locations. If the comparison
reveals that the determined locations are outside of a threshold of
the expected locations, the imaging system may be recalibrated and
the imaging may be repeated.
[0085] The system 300 determines a three-dimensional spatial
position and orientation of the instrument relative to the portion
of the bone based on the determined locations of the mobile
fiducial markers (440). For example, the system 300 may use a
computer-aided-design (CAD) model to determine the known
relationship between the instrument and the mobile fiducial
markers. In this example, the system 300 accesses data defining
three-dimensional spatial position and orientation of the
instrument relative to the mobile fiducial markers determined using
the CAD model of the instrument with the mobile fiducial marker
array attached and determines the three-dimensional spatial
position and orientation of the instrument relative to the portion
of the bone by mapping the three-dimensional spatial position and
orientation of the instrument relative to the mobile fiducial
markers to the determined locations of the mobile fiducial markers.
In this regard, the system 300 uses the known relationship of the
instrument to the mobile fiducial markers to determine the position
and orientation of the instrument relative to the portion of the
bone.
[0086] In another example, the system 300 may use CMM data to
determine the known relationship between the instrument and the
mobile fiducial markers. In this example, the system 300 accesses
data defining three-dimensional spatial position and orientation of
the instrument relative to the mobile fiducial markers determined
CMM evaluation of the instrument with the mobile fiducial marker
array attached and determines the three-dimensional spatial
position and orientation of the instrument relative to the portion
of the bone by mapping the three-dimensional spatial position and
orientation of the instrument relative to the mobile fiducial
markers to the determined locations of the mobile fiducial markers.
In this regard, the system 300 uses the known relationship of the
instrument to the mobile fiducial markers to determine the position
and orientation of the instrument relative to the portion of the
bone.
[0087] The system 300 compares the three-dimensional spatial
position and orientation of the instrument relative to the portion
of the bone with a designed alignment of the instrument to the
portion of the bone (445). For example, the system 300 accesses,
from electronic storage, a designed alignment of the instrument to
the portion of the bone from the pre-surgical alignment design for
the surgical procedure. In this example, the system 300 compares a
three-dimensional spatial position and orientation of the
instrument in the designed alignment with the three-dimensional
spatial position and orientation of the instrument in the
co-registered images. Based on the comparison, the system 300
determines differences between the position of the instrument in
the design relative to the intra-operative position of the
instrument captured in the co-registered images.
[0088] In performing the comparison, the system 300 may match the
pre-surgical alignment design for the instrument to the
co-registered images and, based on the matching, overlay the
pre-surgical alignment design for the instrument onto the
co-registered images. After the pre-surgical alignment design for
the instrument is overlaid on the co-registered images, the system
300 may directly compare the designed alignment to the measured
intra-operative alignment and identify areas where the designed
alignment and the measured intra-operative alignment overlap and
areas where the designed alignment and the measured intra-operative
alignment do not overlap.
[0089] Based on comparison results, the system 300 determines an
indication of precision of alignment of the instrument in the
surgical procedure on the portion of the bone relative to the
designed alignment of the instrument to the portion of the bone
(450). For example, based on the comparison, the system 300
identifies differences in the measured intra-operative alignment
and the designed alignment. In this example, the system 300
analyzes the identified differences and determines an indication of
precision of alignment of the instrument in the surgical procedure
based on the analysis. For instance, the system 300 may determine a
percentage that the measured intra-operative alignment overlaps
with the designed alignment. In addition, the system 300 may
identify spaces between an edge of the instrument in the measured
intra-operative alignment and an edge of the instrument in the
designed alignment. The system 300 may, as part of the indication,
determine a mean and/or median distance among the spaces or
determine a maximum and/or minimum distance among the spaces. The
system 300 may use any type of indication of precision of
alignment. In implementations in which the techniques described
throughout this disclosure are used in knee implants (e.g., TKA),
the system 300 may assess the precision relative to the planes of
resection cuts in the measured intra-operative alignment as
compared to the planes of resection cuts in the designed
alignment.
[0090] The system 300 provides output based on the determined
indication of precision of alignment of the instrument in the
surgical procedure relative to the designed alignment of the
instrument (455). For example, the system 300 may provide output
that indicates the alignment precision in the surgical procedure.
In this example, the system 300 may output a percentage of the
alignment fit and/or output a tolerance measurement that indicates
how closely the alignment matches (e.g., matches within two
millimeters). The system 300 may store the output to indicate how
well the surgical procedure was performed by the surgeon.
[0091] In providing output, the system 300 may be used in surgical
procedures involving cadaver patients, rather than during surgery
on a live patient. In these cases, the setup and use of a bone rig
is used to improve the design process and determine precision in
the alignment process. Accordingly, the output provided by the
system 300 is used to validate the patient-matched design process
on the cadaver patient and the post-operative imaging is used to
improve future results on live patients via surgeon feedback. In
this regard, the system 300 may provide the output by simply
storing the results of the measurements and analysis, rather than
displaying the output live during the surgical procedure. The
system 300 then may later access the stored output, perform
analysis on the accessed output, and display the accessed output
and/or results of the analysis on the accessed output.
[0092] In some implementations, the system 300 may compute
statistics related to general alignment precision for the process
used in the surgical procedure. In these implementations, the
system 300 aggregates the determined indication of precision of
alignment of the instrument in the surgical procedure relative to
the designed alignment of the instrument with similar data
determined from other similar surgical procedures. The system 300
then performs statistical analysis of the aggregated data,
determines a representation of general alignment precision in
surgical procedures included in the aggregated data based on the
statistical analysis of the aggregated data, and provides output
indicating the determined representation of general alignment
precision. For instance, the system 300 may compute a mean
precision, a median precision, or any other statistical indication
of the general alignment precision for the process used in the
surgical procedure. In this regard, the system 300 may perform a T
test and/or F test statistical analysis on the aggregated data and
output the results of the T test and/or F test statistical
analysis.
[0093] In some examples, the system 300 uses post-operative data to
validate the alignment precision determined through use of the
intra-operative image data. In these examples, the system 300 may
access data descriptive of post-operative validation of cuts made
during the surgical procedure and validate the determined
indication of precision of alignment based on the accessed data
descriptive of post-operative validation of cuts made during the
surgical procedure. The post-operative data may include either
non-destructive imaging data for any patients and/or destructive
validation data (e.g., caliper measurements) for cadaveric
subjects. FIG. 13, discussed below, describes post-operative
measurement validation in more detail as it relates to validating
precision in TKA procedures.
[0094] FIG. 12 illustrates an example of a process 1200 for
analyzing non-destructive measurement system results. The
operations of the process 1200 are described generally as being
performed by the system 300. In some implementations, operations of
the process 1200 may be performed by one or more processors
included in one or more electronic devices. The process 1200
illustrates an example of processing that may be performed as part
of or in conjunction with the process 400 using the assembly shown
in FIG. 5.
[0095] As discussed above with respect to FIG. 4, the system 300
accesses an MRI image of the subject bone and uses the MRI image to
determine cartilage thickness (1210). In addition, the system 300
accesses a CT image of the subject bone (i.e., CSYS-1-CT) and
determines a coordinate system for the CT image (1220).
[0096] The system 300 then calculates a 3D transformation between
CSYS-1-CT and CSYS-2-CT (1230). As mentioned above, CSYS-1-CT is
defined as the CT image with a coordinate system defined. CSYS-2-CT
is defined by the sphere pattern of the reference CT-Q-FMA as
measured by the processed CT image.
[0097] In some examples, each surface representing a reference
CT-Q-FMA sphere in the processed CT image is identified and
regression-fitted with an ideal sphere. In these examples, the
pattern of regression-fitted ideal spheres defines CSYS-2-CT. The
processed CT image of the reference CT-Q-FMA may be assumed to be
accurate. Also, the processed CT image of the reference CT-Q-FMA
may be validated by comparison to CMM measurement of the reference
CT-Q-FMA.
[0098] The system 300 co-registers CSYS-2-CT with CSYS-2-Q (1240).
CSYS-2-Q is defined by the sphere pattern of the reference CT-Q-FMA
as measured by motion capture (e.g., ProReflex motion capture
technology provided by Qualisys AB). Each [x,y,z] point measured by
motion capture represents the center of one sphere of the reference
CT-Q-FMA. The pattern of [x,y,z] points defines CSYS-2-Q in the
same way that the pattern of regression fitted ideal spheres
defines CSYS-2-CT. The sphere pattern defining CSYS-2-Q is
regression-fitted to the sphere pattern defining CSYS-2-CT.
Residual pattern fit error may affect measurement system precision,
but is inherently captured in the precision measurement that
follows.
[0099] The system 300 calculates each 3D transformation between
CSYS-2-Q and CSYS-3-Q (1250). CSYS-2-Q is already defined as
discussed above. CSYS-3-Q is defined by the sphere pattern of the
mobile Q-FMA as measured by motion capture (e.g., ProReflex motion
capture technology provided by Qualisys AB). Each [x,y,z] point
measured by motion capture represents the center of one sphere of
the mobile Q-FMA. The pattern of [x,y,z] points defines CSYS-3-Q.
Each intra-operative subject instrument alignment measurement made
with motion capture is calculated as one transformation between
CSYS-2-Q and CSYS-3-Q.
[0100] In some implementations, this 3D transformation is subject
to motion capture measurement noise because there is a limit,
however small, to the precision with which motion capture can
determine the [x,y,z] of a particular sphere. Measurement precision
has several physical influences, and the system 300 attempts to
minimize measurement noise by addressing those physical causes. For
instance, the system 300 uses redundant motion capture cameras,
redundant fiducial markers, appropriately sized and spaced fiducial
markers per the measurement volume, and calibration prior to motion
capture usage.
[0101] To measure motion capture precision, the motion captures are
made of the reference CT-Q-FMA and the mobile Q-FMA where the
mobile Q-FMA is known to be stationary with respect to the
reference CT-Q-FMA (e.g., fixed in place with no human influence).
Recorded alignment fluctuations of the mobile Q-FMA with respect to
the reference CT-Q-FMA may be measured as motion capture
measurement precision, which can affect measurement system
precision. The system 300 may account for the motion capture
precision in the results outputted.
[0102] The system 300 co-registers CSYS-3-Q with CSYS-3-CAD (1260).
CSYS-3-Q is defined as discussed above. CSYS-3-CAD is defined by
the sphere pattern of a computer aided design (CAD) model of the
mobile Q-FMA. The sphere pattern defining CSYS-3-Q is
regression-fitted to the sphere pattern defining CSYS-3-CAD.
[0103] In these examples, residual pattern fit error may affect
measurement system precision, but is inherently captured in the
precision measurement of the prior operations. Manufacturing
deviations of the mobile Q-FMA may contribute to residual pattern
fit error, which may bias measurement system results.
[0104] The system 300 calculates the 3D transformation between
CSYS-3-CAD and CSYS-4-CAD (1270). CSYS-3-CAD is defined as
discussed above. CSYS-4-CAD is defined by the subject instrument
alignment typically associated with subject instrument features,
such as a cutting slot, pin holes, reference lines, etc. The 3D
transformation between CSYS-3-CAD and CSYS-4-CAD is known as it is
predetermined by the design of the instrument rig which positions
and orients the mobile Q-FMA to the subject instrument. In this
regard, the position of the instrument is aligned to the subject
bone based on the images of the fiducial markers of the mobile
Q-FMA and the known relationship of the instrument to the fiducial
markers of the mobile Q-FMA, as defined by CSYS-4-CAD.
[0105] In some examples, manufacturing accuracy of the instrument
fixture may bias measurement system results. Assembly variation of
the mobile Q-FMA, instrument fixture and subject instrument may
affect measurement system precision. In addition, manufacturing
accuracy of the subject instrument(s) is a component of the
measurement system results. Accordingly, the accuracy and precision
of each phase of the surgical procedure and non-destructive
analysis may be taken into account and used in the output provided
by the system 300.
[0106] The system 300 calculates the 3D transformation(s) between
CSYS-4-CAD and CSYS-1-CT (1280). The 3D transformation(s) between
CSYS-4-CAD and CSYS-1-CT (1280) may be calculated using previously
calculated 3D transformations or co-registrations. These 3D
transformations are the results of the measurement system.
[0107] FIG. 13 illustrates an example of a process 1300 for
analyzing destructive measurement system validation results. The
operations of the process 1300 are described generally as being
performed by the system 300. In some implementations, operations of
the process 1300 may be performed by one or more processors
included in one or more electronic devices. The process 1300
illustrates an example of processing that may be performed as part
of or in conjunction with the process 400 using the assembly shown
in FIG. 5.
[0108] After completion of all non-destructive testing using the
measurement system, the subject bone is resected for destructive
validation of the measurement system. Calipers may be used to
measure the thickness of the resected subject bone fragment from
the resected surface to the articular cartilage reference used to
determine the resection depth. The subject bone fragment
measurement does not include the saw-blade thickness. Accordingly,
the system 300 combines the subject bone fragment caliper
measurement with the saw-blade caliper measurement and records them
together.
[0109] The system 300 calculates the 3D transformation between
CSYS-1-CT and CSYS-5-CT-Cut. CSYS-1-CT as discussed above with
respect to FIG. 12.
[0110] CSYS-5-CT-Cut is defined on the resected surface of the
subject bone in the post-operative processed CT image. A
post-operative CT image of the resected subject bone and reference
CT-Q-FMA is obtained and processed using the same methods as the
pre-operative CT imaging and processing. The pre- and
post-operative processed CT images are co-registered with each
other by regression-fitting the sphere pattern of the Reference
CT-Q-FMA present in each processed image. The 3D transformation
between CSYS-1-CT and CSYS-5-CT-Cut is the independent
post-operative CT measure of the resection surface alignment, which
will be compared with the results of the measurement system.
[0111] In some implementations, each [x,y,z] point measured by
motion capture (e.g., ProReflex motion capture technology provided
by Qualisys AB) represents the center of one sphere of the
reference CT-Q-FMA. The sphere pattern is regression-fitted to the
CMM sphere pattern. Residual pattern fit error is recorded by the
system 300. Articular cartilage thickness of the subject bone as
measured in the fat-saturated MR image is compared to the
literature reported range of articular cartilage in the
corresponding region. Articular cartilage measurements and the
literature reported range are recorded by the system 300.
[0112] With the data recorded in the process 1300, the system 300
validates each phase of the measurement process. The system 300
then may validate the entire measurement process and determine the
degree of precision in the measurements, which the system 300 may
output as part of the results.
[0113] FIG. 14 illustrates an example of a generic computer system
1400. The system 1400 can be used for the operations described in
association with the processes 100, 200, 400, 1200, and 1300,
according to some implementations. The system 1400 may be included
in the system 400.
[0114] The system 1400 includes a processor 1410, a memory 1420, a
storage device 1430, and an input/output device 1440. Each of the
components 1410, 1420, 1430, and 1440 are interconnected using a
system bus 1450. The processor 1410 is capable of processing
instructions for execution within the system 1400. In one
implementation, the processor 1410 is a single-threaded processor.
In another implementation, the processor 1410 is a multi-threaded
processor. The processor 1410 is capable of processing instructions
stored in the memory 1420 or on the storage device 1430 to display
graphical information for a user interface on the input/output
device 1440.
[0115] The memory 1420 stores information within the system 1400.
In one implementation, the memory 1420 is a computer-readable
medium. In one implementation, the memory 1420 is a volatile memory
unit. In another implementation, the memory 1420 is a non-volatile
memory unit.
[0116] The storage device 1430 is capable of providing mass storage
for the system 1400. In one implementation, the storage device 1430
is a computer-readable medium. In various different
implementations, the storage device 1430 may be a floppy disk
device, a hard disk device, an optical disk device, or a tape
device.
[0117] The input/output device 1440 provides input/output
operations for the system 1400. In one implementation, the
input/output device 1440 includes a keyboard and/or pointing
device. In another implementation, the input/output device 1440
includes a display unit for displaying graphical user
interfaces.
[0118] The features described can be implemented in digital
electronic circuitry, or in computer hardware, firmware, software,
or in combinations of them. The apparatus can be implemented in a
computer program product tangibly embodied in an information
carrier, e.g., in a machine-readable storage device, for execution
by a programmable processor; and method steps can be performed by a
programmable processor executing a program of instructions to
perform functions of the described implementations by operating on
input data and generating output. The described features can be
implemented advantageously in one or more computer programs that
are executable on a programmable system including at least one
programmable processor coupled to receive data and instructions
from, and to transmit data and instructions to, a data storage
system, at least one input device, and at least one output device.
A computer program is a set of instructions that can be used,
directly or indirectly, in a computer to perform a certain activity
or bring about a certain result. A computer program can be written
in any form of programming language, including compiled or
interpreted languages, and it can be deployed in any form,
including as a stand-alone program or as a module, component,
subroutine, or other unit suitable for use in a computing
environment.
[0119] Suitable processors for the execution of a program of
instructions include, by way of example, both general and special
purpose microprocessors, and the sole processor or one of multiple
processors of any kind of computer. Generally, a processor will
receive instructions and data from a read-only memory or a random
access memory or both. The elements of a computer are a processor
for executing instructions and one or more memories for storing
instructions and data. Generally, a computer will also include, or
be operatively coupled to communicate with, one or more mass
storage devices for storing data files; such devices include
magnetic disks, such as internal hard disks and removable disks;
magneto-optical disks; and optical disks. Storage devices suitable
for tangibly embodying computer program instructions and data
include all forms of non-volatile memory, including by way of
example semiconductor memory devices, such as EPROM, EEPROM, and
flash memory devices; magnetic disks such as internal hard disks
and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM
disks. The processor and the memory can be supplemented by, or
incorporated in, ASICs (application-specific integrated
circuits).
[0120] To provide for interaction with a user, the features can be
implemented on a computer having a display device such as a CRT
(cathode ray tube) or LCD (liquid crystal display) monitor for
displaying information to the user and a keyboard and a pointing
device such as a mouse or a trackball by which the user can provide
input to the computer.
[0121] The features can be implemented in a computer system that
includes a back-end component, such as a data server, or that
includes a middleware component, such as an application server or
an Internet server, or that includes a front-end component, such as
a client computer having a graphical user interface or an Internet
browser, or any combination of them. The components of the system
can be connected by any form or medium of digital data
communication such as a communication network. Examples of
communication networks include, e.g., a LAN, a WAN, and the
computers and networks forming the Internet.
[0122] The computer system can include clients and servers. A
client and server are generally remote from each other and
typically interact through a network, such as the described one.
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.
[0123] The tangible computer-readable mediums described throughout
this disclosure may be referred to as non-transitory
computer-readable mediums. Non-transitory computer-readable mediums
may include any type of hardware storage device and the term
non-transitory may be used to distinguish from intangible
information carriers, such as propagating signals.
[0124] A number of implementations have been described.
Nevertheless, it will be understood that various modifications may
be made without departing from the spirit and scope of the
disclosure. Accordingly, other implementations are within the scope
of the following claims.
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