U.S. patent application number 11/850178 was filed with the patent office on 2008-03-06 for implants with transition surfaces and related processes.
Invention is credited to Roger Ryan Dees, Jason Jordan.
Application Number | 20080058949 11/850178 |
Document ID | / |
Family ID | 38969347 |
Filed Date | 2008-03-06 |
United States Patent
Application |
20080058949 |
Kind Code |
A1 |
Dees; Roger Ryan ; et
al. |
March 6, 2008 |
Implants with Transition Surfaces and Related Processes
Abstract
Implants, and processes for installing them, which replace the
medial condyle and portions of the patellofemoral channel but
preferably not portions of the lateral condyle that articulate
relative to the tibia. Processes are provided which allow proper
location and orientation of an anterior resection and a distal
resection on the femur, which make use of a transition point which
can be designated on the bone, for navigating proper positioning of
such implants. Proper positioning of the implant relative to the
femur for insuring a smooth transition between lateral portions of
the implant and the lateral condyle is thus reduced to determining
proper medial/lateral location of the implant on the anterior and
distal resections. Such implants and processes can allow, among
other things, for controlled location and orientation of an implant
on the bone which saves lateral compartment bone, which eliminates
the need to sacrifice the anterior and posterior cruciate
ligaments, and which is adapted for minimally invasive surgery with
its attendant benefits.
Inventors: |
Dees; Roger Ryan;
(Senatobia, MS) ; Jordan; Jason; (Hernando,
MS) |
Correspondence
Address: |
CHIEF PATENT COUNSEL;SMITH & NEPHEW, INC.
1450 BROOKS ROAD
MEMPHIS
TN
38116
US
|
Family ID: |
38969347 |
Appl. No.: |
11/850178 |
Filed: |
September 5, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60828158 |
Oct 4, 2006 |
|
|
|
60824696 |
Sep 6, 2006 |
|
|
|
60825533 |
Sep 13, 2006 |
|
|
|
Current U.S.
Class: |
623/20.35 ;
606/88 |
Current CPC
Class: |
A61B 17/1764 20130101;
A61B 17/155 20130101; A61F 2/3859 20130101; A61F 2/3877 20130101;
A61F 2002/3895 20130101; A61F 2002/30001 20130101; A61F 2/38
20130101 |
Class at
Publication: |
623/20.35 ;
606/88 |
International
Class: |
A61F 2/38 20060101
A61F002/38; A61B 17/90 20060101 A61B017/90 |
Claims
1. A femoral implant for implantation on resected distal portions
of a patient's femur, comprising: An anterior portion which
comprises an anterior medial articulating surface, an anterior
lateral articulating surface, an anterior patellofemoral channel
and an anterior inner surface adapted to correspond to an anterior
resection on the femur; A transition portion which comprises a
transition medial articulating surface, a transition patellofemoral
channel, a transition lateral articulating surface, and a
transition inner surface adapted to correspond to a transition
resection on the femur, the transition inner surface intersecting
the transition medial articulating surface to form a truncation of
the transition medial articulating surface; A distal medial portion
which comprises a distal articulating surface and a distal inner
surface adapted to correspond to a distal resection on the femur;
and A posterior medial portion which comprises a posterior medial
articulating surface and at least one posterior medial inner
surface adapted to correspond to at least one posterior resection
of the femur.
2. An implant according to claim 1 (all elements of which are
incorporated by this reference) wherein the anterior inner surface,
the distal inner surface and the transition inner surface intersect
at an implant point.
3. An implant according to claim 2 (all elements of which are
incorporated by this reference) adapted to be installed on a
resected femur whereby the anterior resection on the femur contains
a transition point, the anterior resection on the femur is oriented
at a predetermined amount of internal/external rotation relative to
the femur, and the distal resection on the femur substantially
intersects the transition point and is oriented at a predetermined
amount of varus/valgus rotation relative to the transition
point.
4. An implant according to claim 3 (all elements of which are
incorporated by this reference) adapted to be installed on a
resected femur wherein the location of the transition resection on
the femur is determined by moving a resection guide, which contains
a slot corresponding to the transition resection and which is in
sliding contact with the anterior resection and the distal
resection, in a medial or lateral direction on the anterior and
distal resections and determining the position at which bone
abutting the transition articulating lateral surface will form a
smooth transition to lateral condylar articulating surfaces of the
femur.
5. An implant according to claim 1 (all elements of which are
incorporated by this reference) further comprising at least one peg
extending from an inner surface.
6. An implant according to claim 1 (all elements of which are
incorporated by this reference) wherein the implant is structured
so that the lateral condyle of the knee rather than the implant
abuts the tibia at between substantially zero and substantially
ninety degrees flexion of the knee.
7. An implant according to claim 1 (all elements of which are
incorporated by this reference) wherein a patella or patella
implant tracks the patellofemoral channel of the implant at between
substantially zero and substantially seventy degrees flexion.
8. An implant according to claim 1 (all elements of which are
incorporated by this reference) further comprising a tibial
component for attachment to a tibia and for articulating relative
to the implant.
9. An instrument adapted to perform a distal resection a patient's
femur comprising; An instrument index adapted to correspond to a
transition point on an anterior resection of the femur; A distal
resection guide surface and a rod connection portion, the rod
connection portion adapted to adjustably connect to an
intermedullary or extramedullary rod, whereby orientation of the
distal resection guide surface is adjustable in varus/valgus
rotation relative to the transition point on the femur by
maintaining the index substantially aligned with the transition
point while adjusting orientation of the instrument relative to the
rod; Whereby the distal resection guide surface is positioned and
oriented properly to form a distal resection on the medial condyle
of the femur when the index corresponds to the transition point and
the instrument is properly oriented in varus/valgus relative to the
rod.
10. An instrument according to claim 9 (all elements of which are
incorporated by this reference) wherein the instrument index is
adapted to correspond to a transition point that is located at the
distal-most point of a lateral portion of an anterior resection on
the knee.
11. An instrument according to claim 9 (all elements of which are
incorporated by this reference) wherein the rod connection portion
comprises a collet adapted to receive an intramedullary rod.
12. An instrument according to claim 9 (all elements of which are
incorporated by this reference) further comprising a transition
resection guide surface for forming a transition resection
positioned and oriented at an angle relative to the anterior
resection and the distal resection.
13. An instrument according to claim 9 (all elements of which are
incorporated by this reference) wherein the distal resection guide
surface is adapted to guide one of the following: a sawblade and a
milling device.
14. A resection guide adapted to resect a patient's femur,
comprising: A distal resection abutment surface adapted to contact
a distal resection on the femur; An anterior resection abutment
surface adapted to contact an anterior resection on the femur; A
transition resection guide surface for guiding a transition
resection of the femur; An index located on the resection guide at
a position that corresponds to a lateral extremity of an implant
that corresponds in size to the resection guide; Whereby the
transition resection guide surface is adapted to be properly
positioned relative to the distal resection and the anterior
resection for performing a transition resection by contacting the
abutment services of the resection guide with the anterior
resection and the distal resections, and moving the guide in a
medial or lateral direction on the femur to a point where the index
indicates proper medial/lateral alignment of the transition
resection guide surface.
15. A resection guide according to claim 14 (all elements of which
are incorporated by this reference) further comprising a chamfer
resection guide surface for guiding a chamfer resection.
16. A resection guide according to claim 15 (all elements of which
are incorporated by this reference) wherein the chamfer resection
guide surface and the transition resection guide surface are
substantially planar and intersect along a line.
17. A process for conducting knee surgery on a knee comprising a
tibia and a femur, the femur in turn comprising a lateral condyle
and a medial condyle, comprising: Resecting an anterior portion of
a distal portion of the femur, thereby creating an anterior
resection, the anterior resection positioned at a predetermined
depth and oriented at a predetermined angle relative to the femur
in internal/external rotation; Selecting a transition point
relative to the anterior resection, wherein the transition point is
located in the vicinity of the distal-most point of a lateral
portion of the anterior resection; Performing a distal resection on
a portion of the medial condyle, the distal resection intersecting
a point in the vicinity of the transition point, and oriented at a
predetermined angle relative to the femur in varus/valgus rotation;
Performing a transition resection on a lateral portion of the femur
at an angle relative to both the anterior resection and the distal
resection, the transition resection intersecting the anterior
resection and distal resection so that an implant installed on the
bone does not project beyond lateral external surfaces of the femur
and so that external surfaces of lateral portions of the implant
form a smooth transition to lateral external surfaces of the femur;
and Installing an implant on the resected femur, the implant having
inner surfaces which substantially fit the resections, which
implant replaces distal articulating surfaces of the medial condyle
and patellofemoral articulating surfaces, but does not replace
surfaces of the lateral condyle which articulate with the
tibia.
18. A process according to claim 17 (all elements of which are
incorporated by this reference) wherein the process is conducted
and the implant is installed without resection of either an
anterior cruciate ligament or a posterior cruciate ligament of the
knee.
19. A process according to claim 17 (all elements of which are
incorporated by this reference) further comprising resecting a
medial portion of the tibia and installing an implant on the
resected portion of the tibia.
20. A process according to claim 17 (all elements of which are
incorporated by this reference) further comprising installing a
patellar implant.
21. A process according to claim 17 (all elements of which are
incorporated by this reference) in which resecting the anterior
portion of the femur creates a substantially hour-glass shaped
anterior resection with two lobes, wherein the transition point is
located at the distal-most point on the lateral lobe.
22. A process according to claim 17 (all elements of which are
incorporated by this reference) in which the distal resection is
performed using a distal resection instrument connected to an
intramedullary rod inserted in the femur.
23. A process according to claim 17 (all elements of which are
incorporated by this reference) in which the distal resection and
the transition resection are formed using the same resection
guide.
24. A process according to claim 17 (all elements of which are
incorporated by this reference) in which at least one of the
resections is formed using a milling device.
25. A process according to claim 17 (all elements of which are
incorporated by this reference) in which at least one of the
resections is curved.
Description
[0001] This application claims the benefit of the following U.S.
Provisional Applications Ser. No. 60/828158, filed Oct. 4, 2006,
titled Instrumentation for Bicompartmental Knee; Ser. No.
60/824696, filed Sep. 6, 2006, titled Instrumentation for
Bicompartmental Knee; and Ser. No. 60/825533 filed Sep. 13, 2006,
titled Variable Transition Referencing Guide, the entire contents
of each of which are hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The invention relates to implants and processes for use in
joint surgery, particularly knee replacement surgery. In certain
embodiments, methods are provided for locating and using a
transition point on the femur for proper positioning of resections
that are intended to receive a femoral component during a surgical
procedure. Implants are provided according to certain embodiments
that replace the medial condyle and part of the patellofemoral
channel of the femur, but preferably do not replace portions of the
lateral condyle that articulate with respect to the tibia.
According to certain embodiments, a resection guide that includes a
guide surface for performing a transition resection can be
positioned relative to the resections on the bone formed using the
transition point. The resection guide can then be moved on the
resection surfaces to position the transition resection guide
surface to form a transition resection that allows implant external
surfaces to transition smoothly to portions of the lateral condyle
that articulate with respect to the tibia.
BACKGROUND
[0003] Knee arthritis and trauma in various forms can cause loss of
joint cartilage, including for example, osteoarthritis, excessive
wear or sudden trauma, rheumatoid arthritis, or infectious
arthritis. When joint cartilage is worn away, the bone beneath the
cartilage is left exposed, and bone-on-bone contact can be very
painful and damaging. Other types of problems can occur when the
bone itself becomes diseased. One conventional solution for these
types of joint problems takes the form of total knee replacements.
In a total knee replacement (TKR), the proximal end of the tibia is
replaced with a tibial component, the distal end of the femoral
bone is replaced with a femoral component, and the patella is
replaced with a patellar component. Such procedures often require
sacrifice of the anterior and posterior cruciate ligaments.
[0004] However, many patients who develop knee arthritis experience
issues isolated to the medial (inner) compartment and the
patellofemoral (knee cap) part of the joint, while the lateral
(outer) compartment of the joint remains healthy. The conventional
treatment for such patients is either the combination of a
unicompartmental knee in conjunction with a patellofemoral implant
or the use of a total knee implant, which requires removal of the
healthy lateral condyle. However, one recent solution is a hybrid
femoral component that preserves the healthy lateral condyle as
well as the anterior and posterior cruciate ligaments, and only
replaces the medial compartment and patellofemoral joint. (Such a
hybrid femoral component may be used in conjunction with a
unicompartmental tibial tray, which only requires resurfacing of
part of the tibia as well). A hybrid femoral component requires a
smaller incision and preserves ligaments that can help the knee
retain its natural kinematics. It can be implanted using a
procedure called a bicompartmental knee replacement.
[0005] A bicompartmental knee replacement is a procedure that
replaces only the medial (inner) parts of the femoral and tibial
components. It does not resurface or resect the lateral parts of
the knee (including the distal femoral articular cartilage), and as
such, can allow the anterior and posterior cruciate ligaments to be
retained. Bicompartmental knee replacements have a number of
advantages over total knee replacements. Because the outer lateral
portion of the joint is not resurfaced, the incision made may be
smaller, resulting in less pain, quicker recovery time, and less
blood loss. Also, because certain ligaments do not need to be
sacrificed, a greater stability of the knee can be maintained.
[0006] The femoral component used in such a replacement is often
called a monolithic implant. It has an anterior portion and a
medial condyle portion, without a lateral condyle portion (again,
because as much of the lateral bone as possible is retained). As
with most typical femoral implants, the component may be made of
titanium, stainless steel, cobalt-chrome, zirconium, oxinium, any
combination thereof, or any other appropriate material that has
sufficient strength and biocompatibility for use in knee
replacement surgery.
[0007] While performing bicompartmental knee replacement with a
monolithic implant, it is necessary to locate the implant on the
bone properly, in order, among other things, to achieve proper
articulation in both the medial and lateral compartments of the
knee between femur and tibia, as well as proper articulation
between the patella and the femur or femoral component interface.
For example, the surgeon wants to retain as much healthy bone as
possible while removing the diseased bone, but also needs to
consider the depth of the medial condyle portion of the implant in
order to ensure that there is a smooth transition from the implant
to the bone and to maintain proper performance of the reconstructed
knee in flexion and extension.
[0008] With conventional patellofemoral replacements, one popular
current method for preparing the bone to receive an implant is to
use an osteotome in conjunction with a trochlea trial to mark the
boundary of the transition between the implant and the bone.
However, there is no known solution or method for marking the
boundary for bicompartmental knee replacement. Accordingly, such
surgeries are conventionally performed using traditional total knee
replacement instrumentation, without any additional components that
help identify certain reference points. For example, recessing the
implant to the cartilage on the lateral side is important, and
without specific instrumentation or techniques for this type of
procedure, the surgeon is left to estimate the cuts that are
needed.
SUMMARY
[0009] Implants and processes for installing them are provided for
replacing the medial condyle of the femur and portions of the
patellofemoral channel, preferably without replacing portions of
the lateral condyle which have not been subject to degradation.
According to some such processes, instrumentation may be used which
allows for an anterior resection and a distal resection of the
femur that are properly located and oriented so that proper
positioning of the implant to ensure smooth transition between bone
and implant on lateral outer surfaces of the femur, as well as
proper functioning of the reconstructed knee in flexion and
extension, can be reduced to determining the proper medial/lateral
position of the implant on those resections.
[0010] In some cases, an anterior resection instrument can be used
to form an anterior resection that is properly located in the
anterior/posterior dimension and in interior/exterior rotation
relative to the femur. A transition point can then be chosen, which
can correspond if desired to the distal-most point on a lateral
portion of the anterior resection, for proper proximal/distal or
superior/inferior location and valgus/varus rotation of a distal
resection. A distal resection guide, of a type which can be used
with cutting devices such as saws, or of a type which can be used
with milling devices, or a type which can be used with both, and
which can be positioned and oriented relative to the transition
point may be used to perform this distal resection of the medial
condyle. Alternatively, a single such instrument can be used to
perform the anterior resection and the distal resection.
[0011] In some cases, an additional resection guide can be used
which can be positioned properly on the anterior resection and the
distal resection and then slid or otherwise manipulated medially or
laterally to determine proper location of a transition resection
which will help form the transition between implant and bone on
outer surfaces of lateral portions of the femur. Alternatively, one
or more of the transition resection guide surface, the distal
resection guide surface, and also the anterior resection guide
surface can be included in one instrument or resection guide.
[0012] In some cases, implants adapted to be installed on such
resected femurs feature a transition surface which corresponds to
the transition resection that has been controllably located and
oriented relative to the femur as mentioned above. Such a
transition when properly located aims to create a smooth transition
from implant surface to bone surface by, among other things,
reducing surface discontinuity such as implant and/or bone
overhang. Preferably, the transition between bone and implant in
such cases is located so that only anatomical lateral condyle
surfaces articulate relative to the tibia in the knee joint in
which the implant has been installed.
BRIEF DESCRIPTION
[0013] FIG. 1 is a front view of an implant according to certain
embodiments of the invention.
[0014] FIG. 2A is a front view of the implant of FIG. 1 in place on
a model of a human knee.
[0015] FIG. 2B is a navigational rose showing translational and
rotational axes which may constitute useful references in
positioning and orienting body parts, instruments and implants of
certain embodiments of the invention.
[0016] FIG. 2C is a front view corresponding generally to FIG. 2A
with the knee shown in approximately full extension.
[0017] FIG. 2D is a front view of the knee of FIGS. 2A and C with
the knee shown in approximately ninety degrees flexion.
[0018] FIG. 2E is a perspective lateral view of an implant
according to one embodiment of the invention made for a left
knee.
[0019] FIG. 3 is a front view of a human femur on which has been
performed an anterior resection according to one embodiment of the
invention.
[0020] FIG. 4 is a perspective view of an anterior resection guide
according to one embodiment of the invention in place on a
patient's femur to perform an anterior resection such as shown in
FIG. 3.
[0021] FIG. 5 is a perspective view of the anterior resection guide
of FIG. 4 in place where the anterior resection has been
performed.
[0022] FIGS. 6A-6F are schematic distal and front views of human
femurs on which anterior resections according to one embodiment of
the invention have been performed, and which show effect of depth
of the anterior resection on its shape and size.
[0023] FIGS. 7A-7F are schematic distal and front views of human
femurs on which anterior resections according to one embodiment of
the invention have been performed, and which show effect of
internal/external rotation of the anterior resection on its
shape.
[0024] FIG. 8A is a front view of a distal resection guide
according to one embodiment of the invention in place on a human
femur, to perform a distal resection on the medial condyle
according to one embodiment of the invention.
[0025] FIG. 8B is a front view of a distal resection guide
according to one embodiment of the invention in place on a human
femur, with a shim, to perform a distal resection on the medial
condyle according to one embodiment of the invention.
[0026] FIG. 9 is a front view of a human knee, with the femur in
approximately ninety degrees flexion, showing the distal part of
the femur after a distal resection to the medial condyle according
to one embodiment of the invention has been made.
[0027] FIG. 10 is a perspective front view of an anterior/posterior
resection guide according to one embodiment of the invention.
[0028] FIG. 11 is a perspective medial view showing the resection
guide of FIG. 10 in place on a human femur, in contact with the
anterior resection and the medial condyle distal resections, so
that it can be positioned (as by sliding) medially or laterally on
the femur in contact with those resections, to position the
transition cutting surface of the resection guide in order to yield
a smooth transition between implant and bone on the lateral side of
the knee.
[0029] FIG. 12 is a perspective posterior view of the resection
guide of FIGS. 10 and 11 in place on a human femur.
[0030] FIG. 13 is a perspective medial side view of the resection
guide of FIGS. 10-12 in place on a human femur.
[0031] FIG. 14 is a perspective medial front view of a resection
guide according to another embodiment of the invention positioned
on a human femur.
[0032] FIG. 15 is a perspective top view of the resection guide of
FIG. 14 positioned on a human femur.
[0033] FIG. 16 is a perspective lateral front view of the resection
guide of FIG. 14 positioned on a human femur.
[0034] FIG. 17 is a perspective medial front view showing a human
femur on which anterior, distal, chamfer and transition resections
have been made according to one embodiment of the invention, using
resection guides according to certain embodiments of the
invention.
[0035] FIG. 18 is a perspective medial front view showing an
implant according to one embodiment of the invention in place on a
femur.
[0036] FIG. 19 is a front view of a resection guide according to an
alternate embodiment of the invention, for use with milling devices
for forming resections on the femur.
[0037] FIG. 20 is a superior view of the guide of FIG. 19 showing
certain milling devices.
[0038] FIG. 21 is a superior view of the guide of FIG. 19 without
an intramedullary rod.
[0039] FIG. 22 is another superior view of the guide of FIG.
19.
[0040] FIG. 23 is a side view of the guide of FIG. 19.
[0041] FIG. 24 is a perspective view of the guide of FIG. 19.
[0042] FIG. 25 is a side perspective view of the guide of FIG.
19.
[0043] FIG. 26 is a superior view of a guide according to another
alternate embodiment of the invention.
[0044] FIG. 27 is a perspective view of the guide of FIG. 26.
[0045] FIG. 28 is a superior view of the guide of FIG. 26.
[0046] FIG. 29 is a superior view of the guide of FIG. 26.
[0047] FIG. 30 is a superior view of the guide of FIG. 26.
[0048] FIG. 31 is a side view of the guide of FIG. 26.
[0049] FIG. 32 is a perspective view of the guide of FIG. 26.
[0050] FIG. 33 is a side view of a guide according to another
alternate embodiment of the invention.
[0051] FIG. 34 is a perspective view of the guide of FIG. 33.
[0052] FIG. 35 is a superior view of the guide of FIG. 33.
[0053] FIG. 36 is a superior view of the guide of FIG. 33.
[0054] FIG. 37 is a perspective view of the guide of FIG. 33.
[0055] FIG. 38 is a perspective view of a milling guide used with a
milling apparatus which rotates about a medial/lateral axis
according to an alternate embodiment of the invention.
[0056] FIG. 39 is a perspective view of a collet 182 for use in
connection with a guide 180 according to another alternate
embodiment of the invention.
[0057] FIGS. 40A and B are side and front views, respectively, of
the collet of FIG. 39.
[0058] FIG. 41 is a perspective view of a resection guide according
to another alternate embodiment of the invention.
[0059] FIG. 42A and FIG. 42B are side and front views,
respectively, of the guide of FIG. 41.
[0060] FIG. 43 is a perspective view of the guide of FIG. 41.
[0061] FIGS. 44A and 44B are front and side views of the guide of
FIG. 41.
[0062] FIG. 45 is a perspective view of the guide of FIG. 41.
[0063] FIGS. 46A and 46B are front and side views of the guide of
FIG. 41.
[0064] FIGS. 47A and 47B are side views of the guide of FIG.
41.
[0065] FIGS. 49A and 49B show a femur resected using the guide of
FIG. 41.
DETAILED DESCRIPTION
[0066] FIGS. 1 and 2A are front views of an implant 10 according to
an embodiment of the invention. Implant 10 is adapted to be
installed on the distal portion 12 of a human femur 14. The femur
can be that of a human or other being with appropriate hinge
joints. FIG. 2A shows an implant 10 placed on a sawbones model of a
human femur 14. Anatomically, the femur 14 cooperates with the
tibia 16 to form the knee joint 18. The distal portion 12 of the
femur 14 includes two condyles, a medial condyle 20 and a lateral
condyle 22. These condyles articulate (move in gross motion,
whether rotational or translational or both) relative to the tibial
plateau 24 which is a surface on the proximal portion 26 of tibia
16. Not shown is a patella which is connected to a patella tendon,
also not shown, which in turn inserts on the tibia and attaches to
the head of quadricep muscles to apply traction for extension of
the knee joint. The patella tracks, as by sliding, in the
patellofemoral channel 30. Patellofemoral channel 30 of implant 10
shown in FIG. 2A replicates the patellofemoral channel in the
anatomical knee, which is a channel on anterior and distal surfaces
of the femur between condyle 20 and lateral condyle 22 for tracking
of the patella during flexion and extension of the knee 18.
Ordinarily, the femur 14 and tibia 16 do not contact each other but
instead each bear against menisci (not shown) which are interposed
between condyles 20, 22 on the one hand and tibial plateau 24 on
the other hand. An anterior cruciate ligament (not shown) and a
posterior cruciate ligament (not shown) are among two of the
ligaments which are connected to both the femur 14 and the tibia
16. One of the primary purposes of these ligaments is to control
translation of the femur 14 and the tibia 16 relative to each other
and in an anterior/posterior direction. These two ligaments in
particular are important for knee stability and it is often
preferred to preserve them if possible during knee surgery.
[0067] FIG. 2B is a navigational rose that corresponds to FIG. 2A.
It shows the three degrees of translational freedom and the three
degrees of rotational freedom that define the six degrees of
potential freedom of motion in a knee such as the one shown in FIG.
2A. Translationally, the degrees of freedom are lateral/medial,
anterior/posterior and superior/inferior. Rotationally, the degrees
of freedom are flexion/extension, internal/external and
varus/valgus. In that respect, FIGS. 2C AND 2D show a knee 18 with
an implant 10 according to an embodiment of the invention installed
on the femur with the knee at essentially zero degrees of flexion,
and approximately 90 degrees of flexion, respectively.
[0068] FIG. 1 shows an implant 10 according to an embodiment of the
invention together with a tibial implant 38 and a corresponding
insert 40 which together form a prosthesis for reconstructing a
portion of the knee 18. The implant 10 preferably does not replace
some portions of the lateral condyle 22 that articulate against the
menisci in the lateral compartment 42, and thus indirectly tibia
16. However, it does replace portions of the knee 18 such as those
discussed above that are often found to be more prone to
osteoarthritis--the portions of the medial condyle 20 that
articulate against medial compartment menisci and thus indirectly
against tibia 16 (for the prostheses installed) and the
patellofemoral channel 30. Such a structure is beneficial for a
number of reasons, including that the lateral compartment 42 of the
knee 18 (which includes portions of the lateral condyle 22 and
lateral portions of tibia 16) is preserved with multiple beneficial
effects. In addition to improved kinematics and greater stability,
such partial knee replacements can reduce contact of soft tissue
connecting the femur 14 and the tibia 16 or lateral and medial
sides of the knee with the implant 10, and thus lesser wear,
particularly on the lateral side of knee 18. Additionally, the
implant can be installed using minimally invasive surgical
procedures to shorten the hospital stay, simplify the surgical
procedure, and improve therapy prospects and long-term results,
among other benefits. Furthermore, the implant can be installed
without sacrificing the anterior cruciate ligament 34 and the
posterior cruciate ligament 36 (not shown).
[0069] Implant 10 and tibial implant 38 may be made of conventional
metallic or other materials conventionally used for knee
prosthetics, including without limitation cobalt-chrome alloys,
alloys which have been treated with zirconium oxide or other
treatments, stainless steel materials and other metals or
materials. Insert 40 may be formed of conventional ultra high
molecular weight polyethylene of the sort conventionally used to
form inserts in knee prosthetics, or it may be formed of any
desired material.
[0070] FIG. 2D is a front view of the anterior portion of tibia 16
with knee 18 in approximate 90 degrees of flexion. The distal
portion of femur 14 is evident, with lateral condyle 22 intact and
the implant 10 replacing portions of the medial condyle 20 and the
patellofemoral channel 30. (The femoral head 50, which forms part
of the hip socket, can also be seen in this view and can give some
degree of intuitive appreciation for why it may be that medial
compartment 52 of the knee is sometimes more prone to
osteoarthritis and other wear than is lateral compartment 42.)
[0071] As shown in FIG. 2D, distal portion 54 of implant 10
generally corresponds to the portion of the implant 10 between the
anterior portion 44 and the posterior medial condylar portion 56 of
implant 10. It also corresponds generally to distal regions of the
medial condyle 20 and patellofemoral channel 30 of the femur 14. On
the medial side of the knee 18, portions of distal articulating
surfaces 58 of implant 10 articulate against tibial insert 40 which
itself is positioned relative to tibial implant 30 on proximal
portions of the tibia 16 where the tibial implant 38 and insert 40
are used. (In circumstances where the tibial components are not
used, distal articulating surfaces 58 of implant 10 can articulate
against menisci and tibial plateau 24). On the lateral side of the
knee, FIG. 2D makes evident a beneficial result of implant 10, that
the lateral distal surfaces of the femur 14 and the tibia 16 remain
in place to articulate relative to each other. According to this
embodiment, the lateral compartment of the knee 42 is left in place
so that the implant 10 does not articulate with the tibia 16 in
that compartment. Rather, the transition 62, discussed below,
between the implant 10 and the lateral articulating surfaces of the
femur 14 is angled and is located sufficiently anterior on the
lateral side of the femur 14 to reduce chances of such
articulation, while yet providing sufficient replacement of
portions of the patellofemoral channel 30 of the femur 16 which
often suffer arthritic or other degradation when the medial condyle
20 does.
[0072] As shown in FIG. 2D, posterior medial articulating surfaces
60 of implant 10 articulate against insert 40 at greater degrees of
knee 18 flexion. In circumstances where implant 38 and insert 40
are not used, the posterior medial articulating surfaces 60
articulate against menisci and thus tibia 16 indirectly.
[0073] FIG. 2D shows, on the lateral side of the knee 18, a
transition portion of implant 10 of this disclosed embodiment of
the invention which includes transition 62. The structure of this
implant 10 aims to create a smooth transition from the natural bone
lateral condyle 22 material to the implant 10 material. A
transition 62 can be considered smooth if it does not suffer undue
implant 10 or bone surface overhang or discontinuity between
implant 10 and bone. Additionally, the transition 62 with its
angled resection of bone does not require any resection of the
anterior cruciate ligament or posterior cruciate ligament. The
reasons for this include that resections required for implant 10 do
not require cutting of those tissues during minimally invasive
surgery or otherwise, and that no portions of the implant 10
interfere with those tissues when the implant 10 is inserted into
the knee 18 and positioned on the femur 14 during minimally
invasive surgery. Other advantages of the structure and shape of
implant 10 are evident to a person of ordinary skill in the art
from FIG. 2D (as well as other figures and other portions of this
document) and bearing in mind how the implant 10 is installed
during surgical procedure. Additionally, as mentioned above, the
transition 62 feature provides an implant 10 structure where the
lateral meniscus preferably does not come into contact with the
femoral implant, but rather articulates preferably only against
natural bone of the lateral condyle 22.
[0074] Accordingly, FIG. 2D shows a distal view of a femoral
implant which differs from implants such as conventional implants
used in bicompartmental knee arthroplasty, because (among other
things) it omits lateral condylar distal and proximal portions and
instead truncates the lateral structure with transition 62.
[0075] FIG. 2E shows a perspective view of the implant 10 of FIG. 1
from another perspective which is helpful in understanding the
transition 62 and other geometric and navigational aspects and
features of certain embodiments of the invention. Among other
things, the inner surfaces of the implant 10 are shaped and
oriented in a manner that allows precise and accurate positioning
of implant 10 on femur 14 in order, among other things, to
replicate motion of the natural knee and optimize the benefits of
maintaining natural bone in the lateral condyle 22 using transition
62 or similar constructs and related geometry and structures, while
producing a smooth transition from bone to implant across
transition 62.
[0076] FIG. 2E shows a navigational rose which is helpful in
understanding the orientation of various surfaces of implant 10.
Anterior articulating surfaces 46, distal articulating surfaces 58
and posterior medial articulating surfaces 60 are evident. A
transition portion of implant 10 including transition 62 is also
evident. A number of surfaces are shown in FIG. 2E as cooperating
to form inner surfaces of implant 10. As is known to those who
design and install femoral implants, these surfaces are formed with
a view to fitting to distal areas of the femur 14 which have been
resected to correspond to the surfaces. Some or all of the surfaces
may be cemented to the bone or may contain bone in-growth material
such as sintered beads or wires or other porous or similar material
which enhances growth of bone into the surface of the implant, or
they may feature any desired surface characteristics. In the
particular implant shown in FIG. 2E, all of these surfaces on the
inner side of implant 10 are substantially planar, that is
generally flat in the shape of a plane but including the
possibility of discontinuities such as bone ingrowth material,
indentations, raised areas, pegs, openings and other surface
discontinuities which could otherwise technically be said to remove
a surface from the strict category of being substantially in a
plane or being planar. However, implants according to the invention
can also feature one or more interior surfaces which are curved, to
fit resected surfaces which have been formed by resection guides of
the present invention that resect curved surfaces onto bone as by
using milling, grinding, routing, machining, or similar apparatus
which is capable of forming curved surfaces on materials
(hereinafter "milling" devices or apparatus).
[0077] In the particular implant 10 shown in FIG. 2E, anterior
inner surface 64, distal inner surface 66, posterior chamfer
surface 68 and posterior inner surface 70 are intended
substantially to abut corresponding portions of resected bone or
shims or inserts which are interposed between bone and implant to
compensate for undue bone loss or for other reasons. Anterior inner
chamfer surface 72 is disposed between distal inner surface 66 and
anterior inner surface 64 to intersect, preferably as a line,
anterior intersection line 74.
[0078] Additionally, transition surface 76 which is also preferably
but not necessarily substantially planar, extends along lateral
portions of implant 10 to intersect anterior inner chamfer surface
72, preferably in a line, the lateral intersection line 78. In this
particular structure of this embodiment of the invention shown in
FIG. 2E, the anterior inner surface 64, anterior inner chamfer
surface 72, and transition surface 76 intersect at a point on
lateral portions of the implant 10, the convergence point 80. As a
corollary in this construct, anterior intersection line 74 and
lateral intersection line 78 intersect at convergence point 80. In
a similar fashion, planes of the anterior inner surface 64,
transition surface 76 and distal inner surface 66 intersect at
implant point 83. Implant point 83 in some embodiments is located
laterally, when the implant 10 is installed on femur 14, to
transition point 82.
[0079] In the particular implant shown in FIG. 2E, transition
surface 76, like other inner surfaces, is planar, although it can
be curved in other implants according to other embodiments of the
invention. A primary aim of some embodiments of the invention is to
define and use a reference or navigation point on the bone for
positioning and orienting resections and therefore implant 10. So
long as a navigational point such as a transition point on the bone
can be designated to properly form resections that will permit an
implant to be properly positioned and oriented on the femur for
good knee kinematics and performance, the particular shape of the
resected surfaces and corresponding implant surfaces, whether
curved or planar, and how the resections are formed, whether by
sawing, milling or otherwise, matter less and can be accommodated
within the principles of the invention.
[0080] FIG. 3 is a front view of distal portions of a femur 14
which shows an anterior resection 84 and a transition point 82
designated on the bone that can be used to position and orient a
distal resection 100 (discussed below) of the femur 14 that, in
combination with the anterior resection, ultimately allow
positioning of an implant such as shown in FIGS. 1 and 2 on the
bone. Accordingly, among other things, the implant can be located
and oriented properly relative to mechanical axes of the anatomy
and otherwise for proper flexion/extension and other kinematics and
functioning of the knee, and also to allow the transition from bone
to implant 10 across transition 62 to be smooth, so that for
instance it suffers minimal discontinuities such as overhang of
implant or bone.
[0081] In the femur 14 shown in FIG. 3, anterior portions of the
femur 14 have been resected to form anterior resection 84 using
instrumentation that corresponds to the implant shown in FIGS. 1
and 2, as discussed more fully below. Anterior resection 84 will
correspond to anterior portion inner surface 64 of implant 10 when
the implant 10 is installed on femur 14. Anterior resection 84 is
often hourglass in shape with a lateral lobe 86 and a medial lobe
88. The transition point 82 can be chosen as the distal-most point
of lateral portions of anterior resection 84, which in the drawing
of FIG. 3 is the distal-most point on the lateral lobe 86 of
anterior resection 84. What point is distal-most for purposes of
determining the location of the transition point 82 on the bone can
be considered as intersection of a line that is parallel to a line
connecting distal-most portions of the medial and lateral condyles
20, 22.
[0082] Alternatively, location of transition point 82 can be at
another location inside or outside of anterior resection, or at any
other desired point on the bone. What matters primarily is anterior
resection 84 be formed properly on the femur 14 in the
anterior/posterior dimension and in internal/external rotation (see
FIGS. 6A-6F) and that a transition point can be designated relative
to which a distal resection 100 (discussed below) can be formed
properly in the superior/inferior dimension relative to the
anterior resection 84 and oriented properly in varus/valgus
rotation. Proper positioning of an implant 10 with corresponding
surfaces can then be achieved so that among other things, the
implant can be located and oriented properly relative to mechanical
axes of the anatomy and otherwise for proper flexion/extension and
other kinematics and functioning of the knee, and also to allow the
transition from bone to implant 10 across transition 62 to be
smooth, so that for instance it suffers minimal discontinuities
such as overhang of implant or bone.
[0083] FIG. 4 shows an anterior resection instrument 90 according
to one embodiment of the invention for performing an anterior
resection 84 on femur 14 to accommodate the implant 10 of FIGS. 1
and 2. Instrument 90 is coupled to an intramedullary rod 92 which
has been inserted into the distal portion 12 of femur 14. An
extramedullary rod can be used instead of the intramedullary rod.
Before instrument 90 is coupled to intramedullary rod 92, a
template or other device may be employed to mark geometry on the
femur 14, such as the anterior-posterior line and/or a line
perpendicular to it. The instrument 90 may be coupled to the
intramedullary rod and aligned with such indicia to ensure that
anterior resection 84 is properly oriented and located. The
instrument 90 shown in FIGS. 4 and 5 includes a body 94 to which
may be connected in sliding fashion for adjustment in the
anterior-posterior direction, an anterior resection guide surface
96. Body 94 may be connected to intramedullary rod 92 or
extramedullary rod with a collar or other desired structure to
allow for translational and/or rotational freedom as desired. In
the embodiment shown in FIG. 4, body 94 can be controllably
constrained from rotating in any direction relative to the rod,
although the rod itself may be rotated in bone to align the body 94
with the indicia marked on the femur 14. However, body 94 can move
in the anterior-posterior direction relative to the rod, and the
guide surface 96 can move relative to body 94 in the same
direction. Body 94 is also able to slide relative to the rod in the
superior/inferior direction. In the particular embodiment shown in
FIGS. 4 and 5, the body 94 is constrained from translating in the
medial/lateral direction, although that need not necessarily be the
case. A paddle 98, with or without other components connected to
body 94, can be used to determine the appropriate size of implant
10 and thus, in some aspects of the invention, in some cases, size
of certain instrumentation which will be used to install the
implant 10. Once the instrument 90 and particularly body 94 and
anterior resection guide surface 96 have been properly positioned,
guide surface 96 may be used to create anterior resection 84.
[0084] FIGS. 6A-F show effects of moving the guide surface 96 in
the anterior-posterior direction to perform the anterior resection
84. FIGS. 6A and 6B show an anterior resection 84 made with the
guide surface 96 position in a "neutral" anterior-posterior
position. If the guide surface 96 is positioned posteriorly to that
"neutral" position, FIG. 6D shows how the shape and size of
anterior resection 84 changes and enlarges, respectively. If the
guide surface 96 is positioned more anterior to the "neutral"
position, FIG. 6F shows that the anterior resection 84 diminishes
in size and changes shape. Although the shape of each of the
particular anterior resections 84 shown in FIGS. 6B, 6D and 6F are
hourglass and feature lateral lobes 86 and medial lobes 88, it is
possible that at some point the shape could be other than hourglass
such as if the guide surface 96 is positioned sufficiently
posterior of the "neutral" position to make it more heart shaped,
or if it is positioned sufficiently anterior of the "neutral"
position to cause the anterior section 84 to take the form of two
ovals or other rounded closed areas.
[0085] FIGS. 7A-F show effects of internal and external rotation of
the guide surface 96 relative to intramedullary or extramedullary
rod 92 to perform the resection. FIG. 7B shows the anterior
resection 84 formed when the guide surface 96 is positioned in a
neutral internal-external rotational orientation. FIG. 7D shows the
anterior resection 84 when the guide surface 96 has been positioned
with two degrees of internal rotation relative to intramedullary
rod 92. The size of the lateral lobe 86 has diminished and the size
the medial lobe 88 has increased. As shown in FIG. 7F, two degrees
of external rotation of the guide surface 96 relative to
intramedullary rod 92 to form the anterior resection 84 causes the
opposite effect: the lateral lobe 86 increases in size and the
medial lobe 88 decreases in size.
[0086] FIGS. 6 and 7 show that positioning of the anterior
resection guide surface 96 and the anterior-posterior translational
and the internal-external rotational direction can change the size
and shape of the anterior resection 84 and therefore in some
embodiments the location of the bone transition point 82 that is
employed to create the right distal resection 100/anterior
resection 84 location and orientation to allow proper positioning
of implant 10 as shown in FIGS. 1 and 2.
[0087] After the anterior resection 84 has been performed using
this particular embodiment of the invention, instrument 90 may be
removed from the intramedullary rod 92 and a distal resection
instrument 102 coupled to that intramedullary rod 92 for performing
a distal resection 100 on the medial condyle of the femur 14. FIGS.
8A and 8B show one such distal resection instrument 102 according
to this embodiment of the invention.
[0088] Distal resection instrument 102 shown in FIGS. 8A and 8B
includes a distal resection guide surface 104 and structure for
connecting it to the intramedullary rod 92. Preferably, that
structure allows distal resection guide 104 to be adjusted in at
least varus/valgus rotational and superior/inferior translational
directions relative to the rod 92. The structure connecting the
distal resection guide surface 104 and the intramedullary rod 92
can include, for example, a collet 106 and a body 108. The collet
106 can be positioned on the intramedullary rod 92 in sliding
relationship and connected directly or indirectly to body 108 which
can be connected directly or indirectly to resection guide surface
104. For example, guide surface 104 can be connected in sliding
relationship to body 108 so that it can move relative to body 108
in anterior/posterior direction but be constrained in the other
degrees of freedom with respect to body 108. Collet 106 can include
indicia to select and/or indicate magnitude of rotation of guide
104 in the varus/valgus direction. One form of such indicia 110 can
be seen on the top surface of collet 106 and FIG. 8B. Alternately,
a series of collets can be provided for selection by the surgeon to
accommodate various angles of varus/valgus. Distal resection guide
surface 104 can also contain a plurality of openings 112 to receive
pins for pinning it to the bone when properly positioned, for
example by pinning it to the anterior resection 84.
[0089] A distal resection 100 can be performed on the medial
condyle 20 such as by using instrument 102 as follows. Other
instrumentation can also be used, and can suffice if it allows a
distal resection to be made to the medial condyle 20 which
substantially passes through or is navigated relative to transition
point 82 and is correctly oriented in the varus/valgus direction.
With reference to FIGS. 8A and 8B, distal resection instrument 102
can be placed on intramedullary rod 92 and positioned by sliding so
that body 108 is positioned correctly to locate distal resection
guide surface 104 so that it can be positioned and oriented
relative to the bone transition point 82 and rotated in
varus/valgus so that a distal resection 100 may be made using
resection guide surface 104 which passes through, near or suitably
relative to, transition point 80 and is properly oriented in
varus/valgus. It may be desirable to position the resection guide
surface 104 so that the distal resection 100 can pass proximal to
the transition point 82 or, if desired, distal to it. Once the
distal resection guide surface 104 has been properly positioned
relative to intramedullary, extramedullary or other rod 92, it can
be pinned to anterior resection 84, if desired, to perform the
distal resection 100. Accordingly, the rod 92, body 108 and collet
106 can be removed from the bone to leave distal resection guide
surface 104 retained in place by the pins. Resection can also be
performed without pins if desired, by relying on rod 92 and the
other structure of instrumentation 102 to retain the resection
guide surface 104 in place while resection 100 is being
performed.
[0090] To serve as a distal resection guide surface 104 index 114,
a portion of the flat surface of the resection guide surface 104
can be employed to visually align the distal resection guide
surface 104 with the transition point 82, or to place this portion
of the resection guide surface 104 near, such as proximal or distal
relative to, the transition point 82 so that distal resection 100
will pass through, near or suitably relative to, transition point
82. Alternatively, index 114 can include a physical indicium (not
shown) such as a mark, engraving, raised portion, or other desired
indicium on any portion of the distal resection guide surface
104.
[0091] After the distal resection 100 has been performed, distal
resection guide surface 104 can removed from the bone (as can
instrumentation 102 and intramedullary rod 92 if they were left in
place).
[0092] FIG. 9 shows a distal view of a distal resection 100 of the
medial condyle 20 of a femur 14 performed using instrumentation as
shown in FIGS. 8A and 8B. At this stage, after the distal resection
100 has been performed, the position and orientation of an implant
10 have been defined in at least four degrees of freedom by
resecting in accordance with certain embodiments of the invention
as disclosed above:
[0093] anterior/posterior translation as defined by the anterior
resection 84;
[0094] superior/inferior translation as defined by the distal
resection 100;
[0095] internal/external rotation as defined by the anterior
resection 84; and
[0096] varus/valgus rotation as defined by the distal resection
100.
[0097] Thus, essentially all that remains for determining proper
location and orientation of the implant 10 on the femur 14 is
medial/lateral positioning on the anterior resection 84 and distal
resection 100.
[0098] For such medial/lateral positioning, a transition resection
guide 116 according to an embodiment of the invention as shown in
FIGS. 10-13, or other desired instrument, can be used. Among other
things, the resection guide 116 shown in those FIGS. can be used to
create transition resection 118 and anterior chamfer resection 120.
Essentially, any structure is sufficient to perform these
resections if a transition resection 118 can be performed using the
instrumentation which positions properly the transition surface 76
of implant 10 or other implant according to the invention with
reference to location and orientation of both anterior resection 84
and distal resection 100.
[0099] Resection guide 116 as shown in FIGS. 10-13 can include a
finger or other index 122 for aligning guide 116 with transition
point 82. Index 122 can correspond to a relevant landmark on the
implant 10, such as a lateral outer extremity of the implant 10, or
with a predetermined lateral/medial and/or superior/inferior offset
distance, to a point located relative to the implant point 81. The
index 122 may be of any particular structure or shape, including
virtual if desired rather than physical. It can be connected to
body 124 of resection guide 116 as by a flange 126 which has, on
its posterior side as seen best in FIG. 13, an anterior resection
alignment surface 128. Anterior resection alignment surface 128 can
be used to position resection guide 116 as by positioning alignment
surface 128 flat against anterior resection 84.
[0100] The body 124 or any other desired portion of resection guide
116 can include a distal resection alignment surface 130 which can
be used to position resection guide 116 as by positioning it flat
against distal resection 100. Resection guide 116 may thus be
positioned against the femur 14 for proper resection of transition
resection 118 and chamfer resection 120 by moving anterior
resection alignment surface 128 on anterior resection 84 and distal
resection alignment surface 130 on distal resection 112 while
aligning or positioning index 122 medially or laterally to position
transition resection guide 134 properly for a smooth transition of
bone to implant across transition 62 which, for instance, features
minimal discontinuities such as overhang of implant or bone. One
way to achieve that result using the guide 116 shown in FIGS. 10-12
is to position index 122 laterally/medially to an extent that shows
the surgeon where the lateral extremity of the implant 10 will be
positioned relative to the bone, if a transition resection 120 is
performed using transition resection guide surface 134 on guide 116
with guide 116 in that position. Condyle marks 125 on posterior
surfaces of guide 116 (see FIG. 12) corresponding, for example, to
condyle width, can also be used in combination with the index 122
for this purpose. Marks 125 or index 122 may be used independently,
or guide 116 can include any other marks or indices for helping the
surgeon determine where best to position the guide 116 and thus
implant 10 laterally/medially for performing the transition
resection 118 at a location that causes minimal surface
discontinuity across transition 62 between implant 10 and bone.
[0101] Transition resection guide 116 can also contain a chamfer
resection guide surface 132 for forming an anterior chamfer surface
on the bone corresponding to chamfer surface 72 of the implant 10
(see FIG. 2E) and a drill guide bore 136 that is tangent to chamfer
resection guide surface 132 and transition resection guide surface
134, or otherwise corresponds to their intersection. Guide 116 can
if desired include a drill guide bore 136 which can operate as
follows: Once the resection guide 116 has been properly positioned
on the femur 14 as disclosed above, a drill may be aligned through
drill guide bore 136 to form a bore 138 in the bone of the femur 14
that will correspond to lateral intersection 78 on the inner
surface of implant 10 that extends from convergence point 80 in an
angular fashion to help form the intersection between transition
surface 76 of the implant and anterior inner chamfer surface 72 of
implant 10 (see FIG. 2E). Transition resection 118 can then be
performed using transition resection guide surface 134, and chamfer
resection 120 can then be performed using chamfer resection guide
surface 132. These resections can be performed without using drill
guide bore 136 to form a bore 138, and drill guide bore 136 can be
omitted from guide 116 if desired.
[0102] Anterior/posterior resection guide 116 may also include a
posterior resection guide surface 137 for forming a posterior
resection 139 that corresponds to posterior inner surface 70 of the
implant 10. Similarly, resection guide 116 can include a posterior
chamfer resection guide surface 140 for forming a posterior chamfer
resection 142 on the bone that corresponds to posterior chamfer
inner surface 68 of implant 10. These latter resections are shown
in FIG. 13.
[0103] FIGS. 14-16 show an alternative form of resection
instrumentation 144 which uses a single instrument 144 for
performing both a anterior resection 84 and the distal resection
100. Anterior resection guide surface 147 can be used to perform an
anterior resection 100 after instrument 144 has been adjusted so
that anterior resection guide surface 147 is properly located in
the anterior/posterior dimension and in internal/external rotation.
Distal resection guide surface 146 is connected through a structure
which allows it to be positioned relative to intramedullary or
extramedullary rod 92 so that resection guide surface 146 can be
oriented correctly relative to transition point 82 on the bone and
oriented in varus/valgus to form the distal resection 100. Such
structure in the embodiment shown in FIGS. 14-16 include a collet
148 and body 150. The collet includes indicia 152 to indicate
desired varus/valgus orientation of the resection guide surface
146. Similar to the way in which distal resection instrumention 102
may be used, the alternate distal resection guide surface 146 can
be positioned in the superior/inferior direction relative to
intramedullary rod 92 by sliding collet 148 on the rod. It can be
adjusted in varus/valgus by using the indicia on the collet 148. As
in the case of distal resection guide surface 104, the alternate
distal resection guide surface 146 surface itself, without any
markings or special physical distinctions, can serve as an index
154 for positioning of the alternate distal resection guide surface
146 so that the distal resection 100 passes through or near or
relative as desired to the transition point 82. As with the case of
distal resection guide surface 104, alternate distal resection
guide surface 146 or other portion of alternate distal resection
instrumentation 144 can contain indica (not shown) or other desired
markings or features to serve as an index 154 for such proper
alignment so that the distal resection 100 extends through, near or
suitably relative to the transition point 82 and is correctly
positioned in varus/valgus.
[0104] Implant sizing markings 156 can also be included, as shown
in FIGS. 14-16 to allow this instrumentation 144, in a manner
similar to anterior resection instrument 90 and/or distal resection
instrumentation 102, to show or suggest to the surgeon what size of
implant 10, and what size of transition resection guide 116, will
be needed.
[0105] FIG. 17 shows distal portion 12 of femur 14 with what is
left of anterior resection 84 after performing a transition
resection 118 and chamfer resection 120 according to one embodiment
of the invention. This view is taken before posterior resection 138
and posterior chamfer resection 142 have been performed.
[0106] FIG. 18 shows implant 10 installed on femur 14, with the
knee in approximately 65 degrees of flexion. The posterior medial
articulating surfaces 60 of implant 10 are articulating against
tibial insert 40 of the medial compartment 52 of the knee, while
natural bone of the lateral condyle 22 of the femur 14 and the
tibial plateau 24, form the lateral compartment 42 of the knee
18.
[0107] FIGS. 19-25 show a resection guide 158 according to an
alternate embodiment of the invention, which can resect bone so
that implants 10 having one or move curved inner surfaces can be
installed. Accordingly, an anterior resection 84, which may be flat
or curved, can be formed using any desired resection device or
guide, such as those discussed above, or milling apparatus with
appropriately positioned guide. As in the devices discussed above,
a bone transition point 82 which may be designated as desired,
including the distal most point on the lateral portion of anterior
resection 84. Upon designation of the transition point 82, guide
158 may be positioned on the distal portion of femur 12. In the
structure shown in FIGS. 19-25, guide 158 features an anterior
paddle 160 which may be substantially flat or curved as appropriate
to correspond to anterior resection 84. The paddle or other portion
of the guide 158 can also include a transition point index 162 for
helping locate guide 158 relative to transition point 82.
Transition point index 162 can be any desired physical or other
marker or structure on guide 158 as desired. Also, helping position
guide 158 relative to femur 14 is a collet 164 which is connected,
preferably in adjustable relationship, to an intramedullary or
extramedullary rod 166. Collet 164 could also be in the form of an
adjustable structure with indica as can be the case with resection
guides discussed above, or a series of collets 164 each
corresponding to a particular desired varus/valgus angle, may be
employed, one of the collets 164 being selected for a particular
application. Thus, guide 158 can be properly navigated and located
relative to distal portion of femur 12 using the transition point
82 to help regulate the depth of the distal resection or distal
surface to be formed by a milling device operating relative to
guide 158, and proper navigation and location in varus/valgus and
otherwise to cause guide 158 properly to guide milling or other
resection devices to form curved surfaces, straight surfaces, or
combinations, in proper orientation and position for proper
kinematics of the reconstructed knee.
[0108] FIG. 20 shows guide 158 properly located on femur 14 to form
a curved distal resection 112 and posterior resection 139, together
with transition resection 118 (not shown in FIGS. 20-25, but
similar in location and orientation to the transition resection 118
discussed in connection with resection guides disclosed above.) As
shown in FIGS. 20-23, one or more medial condyle milling devices
168 can be guided by guide 158 to form distal resection 112 and
posterior resection 139, both of which are curved and preferably
meet in curved continuous fashion in the particular embodiment
shown in FIGS. 20-23. Guide 158 can be constructed to use only one
medial condyle milling device 168, multiple such devices, or as
otherwise desired. Guide 158 can also be structured to allow the
devices 168 to be positioned in order to rotate about a
medial/lateral axis rather than as shown in FIGS. 20-23. A
transition resection milling device 170 can be used to track within
guide 158 to form the transition resection 118. FIGS. 24 and 25
show a shim 172 which may be coupled to guide 158 to help position
guide 158 relative to medial condyle 20.
[0109] FIGS. 26-32 show a version of the guide 158 with a paddle
160 adapted to correspond to a curved anterior resection 84.
[0110] FIGS. 33-38 show a guide 174 according to another embodiment
of the invention adapted to be navigated relative to the transition
point 82 on a flat or curved anterior resection 84, and for forming
a flat posterior resection 139 on medial condyle 20. Guide 174 can
be navigated relative to the femur 14 using the transition point 82
on the femur 14 which has been designated as disclosed above, and
relative to an intramedullary or extramedullary rod 166 using a
collet 176. The collet 176 can be of the same sort as disclosed
above in connection with guide 158. Once the guide 174 has been
properly navigated and located, including if desired, like guide
158, being pinned to the bone in conventional fashion, the distal
resection 112 can be formed using medial condyle milling devices in
a fashion similar to that disclosed in connection with guide 158.
Alternatively, surfaces of guide 174 can be used to guide a milling
device whose rotational axis is in the medial lateral direction, as
shown in FIG. 38 by way of example. Medial/lateral rotational
milling device 176 can be wider than that shown in FIG. 38, if
desired, and used with a guide 174 which uses slots or other
desired structure to allow milling device 176 to rotate against
bone on the medial condyle 20 to shape it appropriately, and for
device 176 to be guided by and manipulated relative to guide 174. A
transition milling device 170, not shown, may be used as in the
guide 158, to form transition resection 118.
[0111] Guides 158 or 174 may be configured and structured as
desired in order to guide one or more medial condyle milling
devices 168 or 176 to form distal resection 112 and/or posterior
resection 139 in a continuous curved fashion, with or without flat
portions, or as otherwise desired. Guide 174 like guide 158 can be
used in connection with flat or curved anterior resections 84 which
resections may be formed using cutting blocks or milling
guides.
[0112] FIGS. 39-49 show a resection guide 180 according to another
alternate embodiment of the invention. Such a guide can incorporate
functionality for forming not only the distal resection 112,
transition resection 118 and posterior resection 139, but also
anterior resection 84. The particular guide 180 shown in these
figures is adapted to be positioned on a generally tubular collet
182. Collet 182 can be located and positioned on intramedullary or
extramedullary rod 92 so that collet 182 and guide 180 may be
properly positioned and then locked in place as desired relative to
the rod 92. Any other collet can be used, whether or not adjustable
or provided in a series to accommodate various angles of
varus/varus. In the particular structure shown in these FIGS.
39-49, guide 180 can slide and then be locked in place relative to
collet 180 in an anterior/posterior direction, as well as rotated
and then locked into place relative to collet 182 to adjust guide
180 in a varus/valgus rotation as desired relative to femur 14.
Accordingly, guide 180 can be positioned relative to intramedullary
or extramedullary rod 92 in a varus/valgus and interior/exterior
rotational direction, and in a superior/inferior and
anterior/posterior translational direction, and then locked in
place as desired in each of these rotations or translations. Guide
180 contains an anterior resection guide surface 184, a distal
resection guide surface 186, a posterior resection guide surface
188, a transition resection guide surface 190, an anterior chamfer
guide surface 192 and a posterior chamfer guide surface 194. A shim
196 can be used to help position guide 180 for proper distal and
other resections. Shim 196 is shown in FIG. 43.
[0113] In use, intramedullary or extramedullary rod 92 is placed
and the guide 190 of FIGS. 39-49 properly positioned relative to it
on collet 182 to form an anterior resection 84 in accordance with
the principles discussed in connection with the embodiment shown in
FIGS. 5-8. Transition point 82 is then designated and a positioner
198 as shown in FIG. 43 can be connected to guide 190 to abut
anterior resection 84 or otherwise referenced to it, and also
reference positioner 198 and guide 180 relative to transition point
82 so that a distal resection 112 can be formed at proper depth to
achieve proper flexion extension of the reconstructed knee.
Positioner 198 can also contain the distal resection guide surface
186 for forming distal resection 112. Guide 180 and positioner 198
are shown properly navigated and located into place on the femur 14
for forming the distal resection 112. The other resections,
including transition resection 118, posterior resection 139,
anterior chamfer resection 120, posterior chamfer resection 142 can
be formed using the respective guide surfaces 188, 190, 192, and
194. FIGS. 49A and B show the resections formed on the bone using
guide 180: anterior resection 84; distal resection 112, posterior
resection 139, anterior chamfer resection 120 and posterior chamfer
resection 142 and transition resection 118.
[0114] An implant such as that shown in FIGS. 1 and 2 can be
installed on the femur 14 so resected.
* * * * *