U.S. patent application number 12/715590 was filed with the patent office on 2010-06-24 for mis patellar preparation.
This patent application is currently assigned to HOWMEDICA OSTEONICS CORP.. Invention is credited to Sandeep K. Chauhan, Carlos E. Collazo, Jerry D'Alessio, II, Philip F. Williams, III.
Application Number | 20100160915 12/715590 |
Document ID | / |
Family ID | 39642064 |
Filed Date | 2010-06-24 |
United States Patent
Application |
20100160915 |
Kind Code |
A1 |
Chauhan; Sandeep K. ; et
al. |
June 24, 2010 |
MIS PATELLAR PREPARATION
Abstract
Instruments and a method for preparing the articular surface of
the patella to receive a patellar implant are utilized without
everting the patella. A medial or lateral parapatellar incision and
an anterior midline incision are made adjacent the patella. The
patella is clamped with a patella clamp, a hole is drilled from the
anterior surface of the patella. A reamer is inserted through the
medial or lateral parapatellar incision and is then attached to the
end of a drive shaft that extends outwardly beyond the articular
surface of the patella. The posterior facing cutting surface of the
reamer device is then placed in contact with the articular surface.
The drive shaft is then rotated and moved anteriorly causing the
cutting surface of the reamer device to remove a desired amount of
patellar cartilage and bone to accommodate a patellar component.
The patellar component is secured into place by aligning a central
peg protruding from the top surface of the patellar component with
the previously drilled hole in the patellar remnant.
Inventors: |
Chauhan; Sandeep K.;
(Plumpton Green, GB) ; Collazo; Carlos E.; (Old
Greenwich, CT) ; D'Alessio, II; Jerry; (Belleville,
NJ) ; Williams, III; Philip F.; (Teaneck,
NJ) |
Correspondence
Address: |
LERNER, DAVID, LITTENBERG,;KRUMHOLZ & MENTLIK
600 SOUTH AVENUE WEST
WESTFIELD
NJ
07090
US
|
Assignee: |
HOWMEDICA OSTEONICS CORP.
Mahwah
NJ
|
Family ID: |
39642064 |
Appl. No.: |
12/715590 |
Filed: |
March 2, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11583469 |
Oct 18, 2006 |
|
|
|
12715590 |
|
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Current U.S.
Class: |
606/80 |
Current CPC
Class: |
A61B 17/1677 20130101;
A61F 2002/4635 20130101; A61B 17/1767 20130101; A61F 2/3877
20130101 |
Class at
Publication: |
606/80 |
International
Class: |
A61B 17/00 20060101
A61B017/00 |
Claims
1. A reamer system for resecting a posterior surface of a patella
comprising: a guide shaft extending from an anterior surface of the
patella through at least the posterior surface of the patella along
a first axis; a reamer having a cutting surface adapted to receive
the guide shaft along the first axis; a drive shaft extending along
a second axis offset from the first axis; and a gear engaged to the
drive shaft and rotatable about the second axis, wherein the gear
when engaged to the reamer is capable of rotating the reamer about
the first axis as the drive shaft is driven about the second
axis.
2. The reamer system of claim 1, wherein the second axis is
substantially parallel to the first axis.
3. The reamer system of claim 1, further comprising means for
moving the reamer anteriorly along the first axis for resecting the
posterior surface of the patella.
4. The reamer system of claim 3, further comprising means for
moving the gear anteriorly along the second axis while the reamer
is moved anteriorly along the first axis.
5. The reamer system of claim 1, wherein at least a portion of the
guide shaft is housed within a first bushing.
6. The reamer system of claim 5, wherein at least a portion of the
drive shaft is housed within a second bushing.
7. The reamer system of claim 6, wherein the first and second
bushings are connected to each other by an arm extending between
the bushings.
8. The reamer system of claim 7, wherein the second bushing is
connected to a base by a pair of arms extending upward from the
base.
9. A reamer system for resecting a posterior surface of a patella
comprising: a guide shaft extending from an anterior surface of the
patella through at least the posterior surface of the patella along
a first axis; a reamer having a cutting surface adapted to receive
the guide shaft; a first gear engaged to the reamer for rotation
therewith about the first axis; a second gear engaged to the first
gear, the second gear capable of rotating the first gear about the
first axis; and a drive shaft engaged to the second gear.
10. The reamer system of claim 9, wherein the second gear is
rotatable about a second axis transverse to the first axis of the
guide shaft.
11. The reamer system of claim 10, wherein the first axis and the
second axis are substantially perpendicular.
12. The reamer system of claim 9, further comprising: a housing
including the first gear and the second gear therein, the housing
having an outside surface including an attachment element fixed
thereto.
13. The reamer system of claim 12, wherein the attachment element
is attached to a clamp having means for moving the reamer
anteriorly along the first axis for resecting the posterior surface
of the patella.
14. The reamer system of claim 12, wherein the housing further
includes an inside bottom surface having an axle fixed thereto.
15. The reamer system of claim 14, wherein the first gear is
centered about the axle along the first axis.
16. The reamer system of claim 15, wherein the guide shaft, reamer,
first gear and axle are all aligned along the first axis.
17. A reamer system for resecting a posterior surface of a patella
comprising: a guide shaft extending from an anterior surface of the
patella through at least the posterior surface of the patella along
a first axis; a reamer having a cutting surface adapted to receive
the guide shaft; a first gear engaged to the reamer for rotating
the reamer about the first axis; and a drive means operatively
engaged to the first gear for driving the first gear.
18. The reamer system of claim 17, further comprising a second gear
engaged to the first gear, the second gear capable of rotating the
first gear about the first axis, wherein the drive means is engaged
to the second gear.
19. The reamer system of claim 18, wherein the second gear is
rotatable about a second axis transverse to the first axis of the
guide shaft.
20. The reamer system of claim 19, wherein the second gear is a
worm gear.
21. The reamer system of claim 18, wherein the second gear is a
rack located on a second axis and the first gear is a pinion, the
second axis being perpendicular to the first axis of the guide
shaft.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 11/583,469, filed on Oct. 18, 2006, the disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a minimally invasive
apparatus and method for preparing the articular surface of the
patella to receive a patellar implant without everting the
patella.
[0003] Several studies have shown that minimizing the patellar
eversion throughout a resection procedure can produce better and
faster functional outcomes. Known methods and surgical tools for
preparing the articular surface of the patella to receive a
patellar component thereon all require eversion of the patella from
its anatomically correct position at some point during either
resecting the patella for implant fixation, or securing a patella
component to the resected patella.
[0004] Prior art devices for preparing the patella for receiving a
patellar implant are well known to those skilled in the art. It is
known in the art to prepare the patella during total knee
replacement by everting, i.e. rotating the articular surface
anteriorly, the patella approximately 180.degree., or with newer
minimally invasive techniques between 45.degree. and 90.degree..
Patella clamps may be used to clamp the anterior and articular
surfaces of the patella before resecting the articular surface of
the patella. Additionally, some patella clamps may require fixation
pegs or keels to engage the patella before everting it to a desired
angle. Common methods to remove bone from the articular surface of
the patella include saw resection or milling/planar systems. The
removal of bone in either of these systems may provide a flat,
stable platform to support, but not secure, a prosthetic patellar
component.
[0005] For example, Waddell, in U.S. Pat. No. 6,174,314 teaches a
patella resection guide and method of resurfacing the patella in
situ. In this teaching, after adjustments in a resection guide are
made, the patella is cut while in its non-everted position. For
non-eversion of the patella to occur during resection, the Peterson
device requires a flat or angled saw cut to be made through the
resection guide.
[0006] U.S. Pat. No. 6,159,246 relates to a surgical method and
tool for preparing a patella of the knee joint. Here, a method and
device are provided which enable the preparation of a natural
patella for accepting a patella implant. The patella is first held
with a patella holder or clamp, then everted, and then shaped by
means of a bone shaping element.
[0007] Other patella resection guides may not evert the patella if
a saw is used to cut a desired amount of the articular surface of
the patella. Generally when the patella is milled or reamed the
patella must be everted at some degree during resection. Further,
in order to secure a patella component in any of the prior art
systems, at least some eversion of the patella must occur during
either resecting the patella or securing a patella component to the
resected patella.
[0008] Many patella resection guides are known, each having various
designs to clamp and mill/saw the patella. Such designs are shown
in prior U.S. Pat. Nos. 5,716,360; 5,575,793; 5,536,271; and
5129907. Improvements in patella resection guides allowing the
patella to be reamed to receive an implant thereon without everting
the patella during the reaming step are desirable. A minimally
invasive method of preparing the patella to receive an implant
thereon without everting the patella is desirable especially where
only two small incisions through the skin of the knee are made.
Specifically, the articular surface of a patella may be prepared to
receive an implant thereon without everting the patella if a medial
or lateral parapatellar incision is made through the knee capsule
adjacent the patella to gain entry into the knee joint, and another
anterior midline incision is made through the skin of the knee down
to the anterior surface of the patella bone. More generally, the
two incisions may be a medial or lateral parapatellar incision and
a small anterior midline incision made above the centerline of the
patella. Currently, there is no system that allows the entire
patella preparation and implantation of a patellar component to be
performed by reaming without everting the patella.
SUMMARY OF THE INVENTION
[0009] The apparatus and method of preparing the articular surface
of a patella to receive a patellar implant without everting the
patella of the present invention addresses and overcomes problems
found in the prior art. All of the steps of the present invention
may be performed without everting the patella. Specifically, during
a reaming step, the reamer device creates a flat, stable platform
to mate with a flat top surface of a patella component and also
creates a recess in the patella to secure the patella component in
place. The recess in the patella is created by a bore forming
element protruding from the cutting surface of the reamer device.
This recess is provided to house a central peg protruding form the
top surface of a patellar component. Therefore, reaming of the
patella will also prepare a recess for housing a central peg on the
patellar component, allowing for patellar preparation in one
reaming step without everting the patella at any time during either
resecting the patella or securing a patella component to the
resected patella.
[0010] The patellar preparation method can be used in patellar
replacement (hemiarthroplasty), total knee replacement or
patellofemoral replacement. Regardless of the treatment option
chosen, two skin incisions may be made in the knee. Specifically, a
medial or lateral parapatellar incision and a small anterior
midline incision.
[0011] A drill bit may be inserted through an anterior midline skin
incision, the drill bit advancing through the patella from the
anterior surface of the patella and exiting the articular surface
of the patella. This hole or pathway can be used to place a drive
shaft through the patella bone, the drive shaft extending outwardly
from the articular surface of the patella. Further, a reamer or
cutter having a receiving end can be placed through the medial or
lateral parapatellar incision and then connected to the end of the
drive shaft that is extending outwardly from the articular surface
of the patella. Preferably, the drive shaft can be assembled to the
reamer or cutter in situ. A bore forming element protruding from
the cutting surface of the reamer device may be placed in contact
with the articular surface of the patella. The drive shaft
connected to the reamer device may then be pulled anteriorly to
plane the patella flat and create a recess in the patella, the
recess later used to receive a central peg of a patellar component
therein. Additionally, force may be applied downward on the
anterior surface of the patella as the drive shaft is pulled
anteriorly so as to create pressure between the articular surface
of the patella and the cutting surface of the reamer device. This
also allows for there to be less strain on the patella and
quadriceps tendon during the reaming step.
[0012] In accordance with one aspect of the invention is a method
of preparing the articular surface of a patella to receive a
patellar component without everting the patella, the method
comprising the steps of making a medial or lateral parapatellar
incision through the skin of the knee; making an anterior midline
incision through the skin of the knee; engaging the articular
surface and anterior surface of the patella with a patella clamp;
drilling a hole from the anterior surface of the patella to the
articular surface of the patella; inserting a drive shaft through
the drilled hole of the patella, the drive shaft having a first end
that extends outwardly beyond the articular surface; attaching the
first end of the drive shaft to a receiving end of a reamer device;
placing the reamer device in contact with the articular surface of
the patella; resecting the articular surface of the patella by
rotating the drive shaft such that the reamer device removes
cartilage and bone from the articular surface of the patella; and
inserting a patellar component through the medial or lateral
parapatellar incision and securing the patellar component to the
resected articular surface of the patella.
[0013] In accordance with another aspect of the present invention,
the method may further include the step of disengaging the patella
clamp from the articular and anterior surface of the patella after
drilling a hole from the anterior surface of the patella to the
articular surface of the patella.
[0014] In accordance with another aspect of the present invention,
the method may further include the step of centering the reamer
device in contact with the articular surface of the patella. The
reamer device may further include a bore forming element protruding
from the cutting surface of the reamer device that is configured to
prepare a recess in the articular surface of the patella as the
drive shaft is rotated.
[0015] In accordance with another aspect of the present invention,
the first clamping part, the second clamping part, and the drill
guide each have a central axis.
[0016] In accordance with another aspect of the present invention,
the method may further include the step of aligning the central
axis of each of the first clamping part, the second clamping part,
and the drill guide before drilling a hole from the anterior
surface of the patella to the articular surface of the patella.
[0017] In accordance with another aspect of the present invention,
the patellar component includes a central peg which is aligned with
the prepared recess of the articular surface of the patella.
[0018] In yet another aspect of the present invention is a method
of preparing the articular surface of a patella without everting
the patella, the method comprising the steps of making a medial
parapatellar incision through the skin of the knee; making an
anterior midline incision through the skin of the knee; inserting a
first clamping part of a patella clamp through the medial
parapatellar incision; engaging the articular surface of the
patella with the first clamping part; engaging the anterior surface
of the patella with a second clamping part of the patella clamp;
inserting a drill bit through a drill guide, the drill guide
attached to the patellar clamp; drilling a hole from the anterior
surface of the patella through the articular surface of the
patella; inserting a drive shaft through the drilled hole of the
patella, the drive shaft having a first end that extends outwardly
beyond the articular surface; inserting a reamer device having a
receiving end through the medial parapatellar incision; attaching
the first end of the drive shaft to a receiving end of a reamer
device; placing the reamer device in contact with the articular
surface of the patella; resecting the articular surface of the
patella by rotating the drive shaft such that the reamer device
removes bone from the articular surface of the patella; and
inserting a patellar component through the medial or lateral
parapatellar incision and securing the patellar component to the
resected articular surface of the patella.
[0019] Thus it is an aspect of the present invention to provide an
apparatus and method for preparing the patella to receive a
patellar component without everting the patella.
[0020] It is another aspect of the present invention to resect and
prepare the patella to receive an implant thereon without everting
the patella during the reaming step.
[0021] As used herein when referring to bones or other parts of the
body, the term "proximal" means close to the heart and the term
"distal" means more distant from the heart. The term "inferior"
means toward the feet and the term "superior" means toward the
head. The term "anterior" means toward the front part or the face
and the term "posterior" means toward the back of the body. The
term "medial" means toward the midline of the body and the term
"lateral" means away from the midline of the body.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] There follows a detailed description of preferred
embodiments of the present invention which are to be read together
with the drawings therein:
[0023] FIG. 1 is an isometric view of a patella connected to the
tibia via patellar tendon and connected to the femur via quadriceps
tendon;
[0024] FIG. 2 is an exploded isometric view of a typical embodiment
of a patellar clamp for use with the present invention;
[0025] FIG. 3. is a partial assembled isometric view of the patella
clamp of FIG. 2 engaging the patella of FIG. 1;
[0026] FIG. 4 is an isometric view of a drill bit inserted into the
drill guide attached to the patella clamp of FIG. 2 and into the
patella of FIG. 1;
[0027] FIG. 5 is an isometric view of the drill bit of FIG. 4;
[0028] FIG. 6 is a bottom view of the drill bit of FIG. 4;
[0029] FIG. 7 is an isometric view of the resulting hole in the
patella of FIG. 1 after the patellar clamp of FIG. 2 and drill bit
of FIG. 4 are removed from the patella;
[0030] FIG. 8 is an isometric view of a reamer drive shaft inserted
into the hole created from the previous drilling operation;
[0031] FIG. 9 is an isometric view of the reamer drive shaft of
FIG. 8;
[0032] FIG. 10 is a bottom view of the drive shaft of FIG. 9;
[0033] FIG. 11 is a side view of the drive shaft of FIG. 9;
[0034] FIG. 12 is an optimal view of cannula which can receive the
drive shaft of FIG. 9;
[0035] FIG. 13 is an isometric view of a reaming device to be
coupled to the drive shaft of FIG. 9;
[0036] FIG. 14 is a side view of the reaming device of FIG. 13;
[0037] FIG. 15 is a top view of the reaming device of FIG. 13
showing the cutting surface;
[0038] FIG. 16 is a cross sectional view taken along line 16-16 of
FIG. 15;
[0039] FIG. 17 is an isometric view of a reaming device in contact
with the articular surface of the patella of FIG. 1 with the
reaming device connected to the drive shaft of FIG. 9;
[0040] FIG. 18 is an isometric view of a patellar component to be
used after the patella is prepared by the reamer of FIG. 13;
[0041] FIG. 19 is a side view of the patellar component of FIG.
18;
[0042] FIG. 20 is a bottom view of the patellar component of FIG.
18 showing the bone contacting surface;
[0043] FIG. 21 is a cross sectional view taken along line 21-21 of
FIG. 20;
[0044] FIG. 22 is an isometric view similar to FIG. 1 showing
patellar component of FIG. 18 with the patella;
[0045] FIG. 23 is an isometric cross-sectional view of a patellar
component connected to the articular surface of the patella of FIG.
1 along lines 23-23 of FIG. 22;
[0046] FIG. 24 shows an alternate embodiment of the patella reaming
system of the present invention wherein a drive is radially offset
from the patella reamer;
[0047] FIG. 25A shows an exploded view of an additional embodiment
of the present invention;
[0048] FIG. 25B shows a top view of this alternate embodiment of
the present invention in an assembled condition;
[0049] FIG. 25C shows a cross-sectional view of the additional
embodiment through the plane of the page;
[0050] FIG. 26A shows an assembled view of yet a further embodiment
of the present invention; and
[0051] FIG. 26B shows an exploded view of the further embodiment of
FIG. 26A.
DETAILED DESCRIPTION
[0052] The patellar tendon attaches to the tibial tubercle on the
front of the tibia just below the front of the knee. It also is
attached to the bottom of the patella. At the top of the patella,
the quadriceps tendon is attached. At the top of the quadriceps
tendon is the quadriceps muscle. The quadriceps muscle is the large
muscle on the front of the thigh. As the quadriceps muscle
contracts, it pulls on the quadriceps tendon, the patella, the
patellar tendon, and the tibia to move the knee from a flexed
position to an extended position. Conversely, when the quadriceps
muscle relaxes, it lengthens. This allows the knee to move from a
position of extension to a position of flexion.
[0053] Referring to FIG. 1, there is shown a knee joint 10 in an
extended position with a patella 12 in a non-everted position.
Patellar tendon 14 attaches a distal end 16 of the patella 12 to
tibia 18. Quadriceps tendon 20 attaches a proximal end 22 of the
patella 12 to femur 24. If the patellar tendon 14 ruptures, the
patella 12 loses its anchoring support to the tibia 18. Without
this anchoring effect of the intact patella tendon 14, the patella
tends to move superiorly (towards the hip) as the quadriceps muscle
contracts. Without intact patella tendon 14, the patient is unable
to straighten the knee 10. If a rupture of patella tendon 14
occurs, and the patient tries to stand up, the knee will usually
buckle and give way because the body is no longer able to hold the
knee in a position of extension.
[0054] In FIG. 1, patella 12 has an anterior surface 24 and a
posterior articular surface 26. When the bone of the articular
surfaces of femur 24 the knee joint and/or surface 26 of patella 12
is damaged through arthritis or other joint disease or injury or
wear, the articular surface 26 may be resected in order to receive
a prosthetic patellar component thereon. This is usually done in
connection with total knee anthroplasty. If patellar tendon 14 is
not ruptured, and the articular surface of the patella is damaged,
it is beneficial for a patient receiving a patellar component to
have the articular surface prepared to receive a patellar component
without everting the patella. In this manner, the patella and
quadriceps tendons are not strained if the procedure is performed
without everting the patella. This allows for easier recovery after
surgery and less post-operative pain.
[0055] Referring to FIG. 2 there is shown an exploded isometric
view of a patellar clamp 30 with a drill guide apparatus 38 for use
in the present invention. Such a clamp is shown in U.S. Publication
2004/0162561 the disclosure of which is incorporated herein by
reference. Patellar clamp 30 comprises a main body portion 32, a
first modular clamping part 34, a second clamping part 36, and a
drill guide 38. Main body portion 32 of patellar clamp 30 includes
a pair of handle portions 54 which are connected to moveable
receptacles 200 and 202 which are coupled to the handle 54 by a
linkage mechanism such as described in U.S. Publication
2004/0162561. Receptacles 200 and 202 include bores 204 and 206
into which insertion portions 208 of clamping part 34 and 210 of
clamping part 36 are inserted. Insertion portions 208 and 210 are
held within receptacles 202 and 204 by spring detent which can be
released by depressing buttons 212 and 214. Likewise an insertion
element 216 is mounted on a frame 218 which is coupled to the
linkage mechanism of main body portion 32. Drill guide 38 may be
releasably attached to insertion portion 216 and, although not
shown in FIG. 2, includes a receptacle similar to 202 and 204 with
a quick release button 220 which operates in a similar manner as
release buttons 212 and 214. Drill guide 38 includes a support arm
222 which allows the drill guide barrel 39 of drill guide 38 to be
placed adjacent the centers of first and second clamping parts 34,
36. Barrel includes an opening 52 through which a drive element or
drill bit (not shown) may be inserted along axis 44. When clamping
parts 34, 36 of patellar clamp 30 are assembled as shown in FIG. 3,
a central axis 40 of first clamping part 34 and a central axis 42,
of second clamping part 36, and a central axis 44 of drill guide 38
are aligned. First clamping part 34 includes a bore 46 to allow a
drill bit inserted through an opening 52 of drill guide 38 to
extend outwardly beyond articular surface 26 of patella 12, and
thus will protect the anterior aspect of a native femur.
[0056] Additionally, the preferred surgical method of the present
invention is a minimally invasive procedure for preparing the
articular surface of the patella to receive a patellar implant
without everting the patella. Before the apparatus of the present
invention is inserted into the body, two skin incisions are
preferably made through the skin of the knee. Specifically, a
medial or lateral parapatellar incision and a small anterior
midline incision are made. Once exposure to the knee is attained,
the clamping part of a standard patellar clamp is inserted into the
joint of the knee. For example with the knee in full extension, a
first clamping part of patella clamp 30 is inserted through the
medial or lateral parapatellar incision. Preferably, patella 12 may
be slightly raised in the anterior direction without everting the
patella, to accommodate first clamping part 34 of patella clamp 30
thereunder. The top surface 43 of first clamping part 34 is brought
into contact with articular surface 26 of patella 12. The articular
surface 26 of patella 12 should be centered along axis 40 on first
clamping part 34, specifically, at the location of counter bore 46.
Preferably, first clamping part 34 of patella clamp 30 may include
fixation pegs or spike 48 to dig into the articular surface of
patella 12 so as to limit the movement of the patella during a
subsequent drilling step.
[0057] Further, second clamping part 36 of patella clamp 30 may be
placed on the anterior skin of the knee with a recess 50
surrounding patella 12. Recess 50 of modular clamping part is
placed over the anterior midline incision and drill guide 38
located at the center of recess 50 along axis 42 so that the axis
40, 42 and 44 are all coaxial. Drill guide 38 is first used to
accommodate a drill bit used to create a hole or pathway through
patella 12 from anterior surface 24 and exiting the articular
surface 26. Drill guide 38 includes an upper stop surface 39
surrounding opening 42. Drill guide 38 may be later used to
accommodate a drive shaft used to connect to a reamer device for
resecting articular surface 26 of patella 12 and preparing the
patella to receive a patella component thereon.
[0058] FIG. 3. is an assembled isometric view of the clamping end
of patella clamp 30 of FIG. 2 engaging the patella of FIG. 1. Drill
guide 38 is attached to patella clamp 30, which is used to center
drill hole 52 on patella 12. The central axis of drill guide 44 is
axially aligned with axis 40, 42 of the first and second clamping
parts. Preferably, the patella clamp 30 extends medially or
laterally and is set perpendicular to the patellar tendon. The
preferred patella clamp is secured into place by squeezing handles
54 shown in FIG. 2.
[0059] FIG. 4 is an isometric view of the clamping end of patella
clamp 30 with a drill bit 56 inserted into an aperture 52 the drill
guide 38 attached to patella clamp 30 of FIG. 2. After passing
through drill guide 38, drill bit 56 may be placed through a small
anterior midline incision made through the anterior skin of the
knee (not shown) until it touches anterior surface 24 of patella
12. Preferably, drill bit 56 is then advanced through anterior
surface 24 and exiting articular surface 26 of patella 12. As shown
in FIG. 2, the first clamping part 34 of the patella clamp 30
preferably includes a counter bore or hole 46 to allow drill bit 56
to extend outwardly beyond articular surface 26 of patella 12. By
lifting the patella 12 the end of the drill bit will be spaced from
the trochlear groove area and this will protect the anterior aspect
of the native femur.
[0060] An isometric view of a preferred embodiment of a drill bit
56 is shown in FIG. 5. Drill bit 56 includes a top portion 58 which
is configured to be inserted into a driver mechanism, such as a
power tool that will rotate a cutting surface 60 of drill bit 56
and thus remove bone from patella 12. It will be understood and
appreciated by those skilled in the art that the structure of the
drill bit, including top portion 58 and cutting surface 60 of this
preferred embodiment is configurable in any one of a number of
designs to create the desired result of drilling through bone,
specifically patella 12. Preferably, drill bit 56 further includes
a stopping portion 62, which has a stop surface 63 configured to
engage surface 39 and prohibit the drill bit 56 from advancing any
further through the aperture 52 of drill guide 38 once the stop
surface 63 of stopping portion 62 comes in contact with top portion
39 of drill guide 38. FIG. 6 is a bottom view of the drill bit 56
with a larger diameter representing the outer diameter of stopping
portion 62, and a smaller diameter 64 representing the diameter of
cutting surface 60 of drill bit 56 with stop surface 63 extending
therebetween.
[0061] FIG. 7 is an isometric view of the knee joint with the
drilled hole 68 in patella 12 after patellar clamp 30 and drill bit
56 are removed from patella 12 upon completion of the drilling
step. The resulting hole 68 has approximately the same to slightly
larger diameter as smaller diameter 64 representing the diameter of
cutting surface 60 of drill bit 56. Preferably, this hole 68 is
able to accommodate a drive shaft therethrough which will attach to
a reamer device and be able to ream articular surface 26 of patella
12 as described below.
[0062] FIG. 8 is an isometric view of a reamer drive 70 inserted
into and through hole 68. FIGS. 9-11 depict a preferred embodiment
of a reamer drive 70 as shown in FIG. 8. Referring to FIGS. 8-11
drive shaft 70 includes an upper drive portion 72 which is
configured to be inserted into a driver mechanism, such as a power
tool used to rotate a drive shaft 71. Drive shaft 71 has a threaded
portion 74 which mates with a threaded receiving portion of a
reamer. It will be obvious to an ordinary person skilled in the art
to have drive shaft 71 include any of a various different
connection portions such as a quick connect portion that can couple
the end of drive shaft 71 with a receiving end 96 of a reamer 90
shown in FIG. 13, such as but not limited to threads, tapers,
press-fit and spring detent mechanisms. Drive shaft 71 further
includes a stopping portion 76, which is configured to prohibit the
drive shaft 70 from advancing any further through aperture 52 of
drill guide 38 once a stop surface 78 of stopping portion 76 comes
in contact with top portion 39 of drill guide 38. FIG. is a bottom
view of the drive shaft 70 with a larger diameter 80 representing
the outer diameter of stopping portion 76, and a diameter 82
representing the diameter of the shaft 71 and diameter 83
representing the diameter of thread 74 which is the preferred
embodiment of a connection feature. Surface 78 is formed between
diameters 76 and 82. Referring to FIG. 11, depth gauge markings 84
are provided along at least part of the length of drive shaft 71.
In the preferred embodiment, once end portion 74 of drive shaft 71
is connected to a thread bore 97 of receiving portion 96 of reamer
90, these depth gauge markings 84 can be used for measuring the
depth of the cut in articular surface 26 of patella 12.
[0063] The depth of the cut can be determined several ways. In a
preferred embodiment, a depth gauge may be placed through the
patella 12 with a surgeon placing its end flush with articular
surface 26 of patella 12 to assess its overall thickness and using
the depth gauge markings 84 on drive shaft 71 to remove the desired
amount of bone from articular surface 26. In an alternate
embodiment, a cannula 86 having a bore 89 as shown in FIG. 12, may
be placed through drilled hole 68 previously made in the patella
12. The cannula 86 has depth gauge markings 88 on the outside
surface which may be used to help set the depth of the resection.
Drive shaft 70 is then inserted into bore 89 of cannula 86 and
connected to receiving end of reamer device 40 shown in FIGS. 13-16
as previously described, through any one of a number of quick
connect features. Once reamer head 90 begins to rotate and is
pulled anteriorly, a top surface 94 of reamer 90 will touch the
cannula 86 and set the depth limit. The cannula bore 89 has a
diameter that is slightly larger than diameter 82 of drive shaft
71.
[0064] Referring to FIGS. 13-16, there is shown a preferred
embodiment of reaming device 90. To assemble reaming device to
drive shaft 71 in situ, reamer device 90 is inserted through a
medial or lateral parapatellar incision made through the skin of
the knee. Preferably, the posterior facing surface 92 of reamer
device 90 is made of a non-abrasive material such as polyethylene
so as to minimize any damage on the anterior femur during reaming.
Preferably, reamer device 90 is available in several diameters to
approximate a range of sizes of patella 12.
[0065] A quick connect feature is provided to couple reamer 90 to
shaft 71. In the preferred embodiment threaded end 74 of drive
shaft 71 is configured to mate with threaded bore 97 of receiving
end 96 of a reamer device 90. After the two threaded elements are
joined the anterior surface 94 of the receiving end 96 is placed in
contact with articular surface of patella. Top surface 94 of
receiving end 96 forms a starting point for a bore cutting surface
98, which on anterior movement, creates a cylindrical recess 13
(shown in FIG. 23) in patella 12 as the reamer device is rotated
during the reaming step. Reamer device 90 further includes cutting
teeth 102 in cutting surface 99. When pressure is applied between
articular surface 26 of patella 12 and surface 94 of receiving end
96 of reamer device 90 while pulling a rotating drive shaft
anteriorly and preferably applying downward force on the anterior
surface 24 of the patella, cartilage and then bone will begin to be
removed from the articular surface 26 of patella 12 and receiving
end 96 will create the cylindrical recess 13 in patella 12.
Eventually, cutting surface 102 of reamer device 90 will begin to
remove cartilage and bone from articular surface 26 of patella 12
and create a flat, stable platform to mate with a flat anterior
surface of a prosthetic patellar component. Preferably, a desired
amount of bone may be removed through use of the depth gauge
markings 84 of drive shaft 71 or cannula 86. FIG. 17 illustrates
reaming device 90 in contact with articular surface 26 of patella
12. The reaming device is shown connected to drive shaft 71.
[0066] After the reaming step takes place, the reamer device 90 may
be disassembled from end 74 of drive shaft 71. Preferably, the
drive shaft 71 is removed back through the anterior midline
incision in the skin of the knee. The reamer device 90 may be
removed back through the medial or lateral parapatellar incision.
Next, a patellar component 110 illustrated in FIGS. 18-21, is
inserted through the medial or lateral parapatellar incision. In
the preferred embodiment patellar component 110 may include a
central peg 112 that protrudes from top surface 114. The central
peg 112 mates with recess 13 of patella 12 created during the
reaming step. The central peg includes a chamfer portion 116 which
may be in the form of a taper for easy insertion of central peg 112
into recess 13. Additionally, central peg 112 may further include a
recessed portion 118. Preferably, the anterior surface 114 of the
patellar component 110 further includes a plurality of grooves 120
which create friction between the prepared resected surface 15 of
the patella and the anterior facing surface 114 of the patella
component 110 that creates a stabilizing fit between the two mated
surfaces. Surface 114 of the patella may contain recesses 121 which
may receive bone cement on cementing the patellar component to the
prepared bone.
[0067] FIG. 22 is alternate view of the assembled patellar
component 110 and patella 12. FIG. 23 is a view of the central peg
112 of the patellar component 110 mated with recess 13 of patella
12. The mated resected surface 15 of patella 12 and top surface 114
of patellar component 110 is also illustrated. After the patellar
component 110 is cemented into place, any skin incision previously
made in the knee may be closed.
[0068] Referring to FIG. 24 there is shown a patella 12 utilizing a
guide pin 250 extending through bore 68 integrally connected to the
reamer 252 having anteriorly facing cutting surfaces or teeth 254.
Reamer 252 includes a plurality of gear teeth 256 around the outer
circumference thereof. Guide pin 250 and reamer 252 are supported
in a jig generally noted as 260 which has a cylindrical bushing 262
housing guide pin 250. Bushing 262 is connected by arm 264 to a
second bushing 266 which houses slidable housing 267. Housing 267
in turn receives drive shaft 268 which is connected to a drive gear
270. It can be seen as gear 270 rotates teeth 272 thereon engage
teeth 256 of reamer 252 to transfer the drive forces from drive
shaft 268 to reamer 252.
[0069] In this embodiment slidable housing 267 is connected via a
pair of arms 274 to a base 276. If desired drive pin 250 and drive
shaft 268 can extend through base plate 278 with the tip of drive
shaft 268 being flush with the posteriorly facing surface of plate
278. Housing 267 can slide within second bushing 267 such that the
cutting teeth 254 of reamer 252 engage the posterior surface of the
patella as housing 267 is moved anteriorly in direction D to
prepare the surface of the patella. The advantage of using an
offset drive system as shown in FIG. 24 is that greater torque can
be transmitted into reamer 252 by a gear drive system than can be
transmitted by a small diameter drive shaft 70.
[0070] Referring to FIG. 25A there is shown an exploded view of an
additional embodiment which is generally denoted as 300. The
embodiment 300 includes a drive shaft 302 coupled to a ball joint
generally denoted as 304 coupled to a worm gear shaft 306. Worm
gear shaft extends through an opening 308 of worm gear 310 which
fits inside housing 312. Housing 312 includes an axle 314 in which
a drive pinion 316 is mounted. Drive pinion 316 is operatively
connected to reamer 318 which has a face 320 for engaging the
posterior surface of the patella. The guide shaft 322 extends
through the patella (not shown) as do the guide and drive shafts
previously described, for example shaft 70. An attachment element
324 is fixed to housing 312 so that the reaming system 300 may be
attached to the clamping handle of FIG. 2. The U-joints and drive
shaft are coupled to the respective gear and U-joint portions by
typical pins 326 for the transmission of the drive torque.
[0071] Referring to FIGS. 25B and 25C there is shown a top and
cross-sectional view respectively, of the alternate reaming system
of FIG. 25A. In FIG. 25B the system 300 is assembled showing the
drive shaft 302 driving the worm gear 310 via U-joint 304. This in
turn drives cutting face 320 of reamer 318 which is rotatably
mounted in housing 312. The coupling element 324 is shown in both
FIGS. 25B and 25C. Referring to FIG. 25C pinion gear 316 is shown
being driven by worm gear 310 via shaft 302, U-joint 304 and worm
gear shaft 306 which is now coupled to the worm gear via pin
326.
[0072] Referring to FIGS. 26A and 26B there is shown yet a further
alternate embodiment generally denoted as 400 which is in the form
of a rack and pinion system. Embodiment 400 includes rack 402 and
pinion 404 again mounted in a housing 412 including an axle 314 to
which pinion 404 is fixedly attached. Again housing 412 includes
attachment coupling element 424 for coupling the drive system 400
to the handle of FIG. 2. Although the reamer is not shown in FIGS.
26 and 26B it is fixedly coupled to pinion 404 for rotation
therewith. Obviously a drive system would be used to reciprocating
rack 402 which in turn would rotate pinion 404 first in one
direction and then in the other direction which in turn drives the
reamer which resects the posterior surface of the patella as
described hereinbefore.
[0073] Although the invention herein has been described with
reference to particular embodiments, it is to be understood that
these embodiments are merely illustrative of the principles and
applications of the present invention. It is therefore to be
understood that numerous modifications may be made to the
illustrative embodiments and that other arrangements may be devised
without departing from the spirit and scope of the present
invention as defined by the appended claims.
* * * * *