U.S. patent application number 10/366014 was filed with the patent office on 2004-08-19 for modular patella instrument.
This patent application is currently assigned to Howmedica Osteonics Corp.. Invention is credited to Barile, Gennaro, Marchyn, Duane J., Neal, David J., Starace, Louis M..
Application Number | 20040162561 10/366014 |
Document ID | / |
Family ID | 32849691 |
Filed Date | 2004-08-19 |
United States Patent
Application |
20040162561 |
Kind Code |
A1 |
Marchyn, Duane J. ; et
al. |
August 19, 2004 |
Modular patella instrument
Abstract
A patella clamp has a first part including a reference surface
engageable with the anterior surface of a patella. The first part
includes a stop surface spaced from the reference surface. A second
clamping part is provided which is moveable with respect to the
first clamping part. A cutting element coupled to the first
clamping part is moveable with respect to the first part. The
cutting element includes a shaft with an adjustable collar mounted
on the shaft for movement with respect to the longitudinal axis of
the shaft and cutting element. The adjustable collar on the shaft
is engageable with a stop surface on the first part for spacing the
cutting element a desired distance from the reference surface. A
pair of gages are provided for selectively setting the position of
the adjustable collar with respect to either the amount of patella
bone being removed or the amount of patella bone remaining.
Inventors: |
Marchyn, Duane J.;
(Portsmouth, OH) ; Starace, Louis M.; (Suffern,
NY) ; Neal, David J.; (Oak Ridge, NJ) ;
Barile, Gennaro; (Secaucus, NJ) |
Correspondence
Address: |
LERNER, DAVID, LITTENBERG,
KRUMHOLZ & MENTLIK
600 SOUTH AVENUE WEST
WESTFIELD
NJ
07090
US
|
Assignee: |
Howmedica Osteonics Corp.
Allendale
NJ
|
Family ID: |
32849691 |
Appl. No.: |
10/366014 |
Filed: |
February 13, 2003 |
Current U.S.
Class: |
606/78 |
Current CPC
Class: |
A61B 17/1677 20130101;
A61B 2090/034 20160201 |
Class at
Publication: |
606/078 |
International
Class: |
A61B 017/32 |
Claims
1. A patellar resurfacing clamp comprising: a first part having a
first surface engageable with a surface of the patella and
including a second surface spaced from said first surface; a second
part moveable with respect to the first part; a patella cutting
element coupled to said first part and moveable with respect to
said first part, said cutting element having a shaft and an
adjustable collar mounted on the shaft for movement with respect to
a longitudinal axis of the shaft, said adjustable collar on said
shaft having a first stop surface engageable with said second
surface on said first part for spacing said cutting element a
distance from said first surface; and at least one gage element for
selectively setting the position of said adjustable collar on said
shaft with respect to the first surface contacting the patella
based on either the amount of patella bone being removed or the
amount of patella remaining.
2. The patella clamp as set forth in claim 1 wherein there are two
gage elements, one for setting the position of said collar along
the shaft with respect to said amount of bone removed and one for
setting the position of said collar along the shaft with respect to
the amount of bone remaining.
3. The patellar clamp as set forth in claim 1 wherein the shaft is
a drive shaft.
4. The patellar clamp as set forth in claim 3 wherein said shaft
has a portion having external teeth for engaging the collar.
5. The patellar clamp as set forth in claim 4 wherein said collar
has an internal locking element for selectively engaging said
external teeth on said shaft to set the adjustment of said collar
along said longitudinal axis.
6. The patellar clamp as set forth in claim 5 wherein said collar
is moveable from a first position where said collar may slide with
respect to said shaft to a second position where said teeth on said
shaft and said collar engage and prevent further axial
movement.
7. The patellar clamp as set forth in claim 1 wherein said second
part includes a tubular clamping jaw for engaging a surface of the
patella opposite a patella surface engaging said first surface of
said first part.
8. The patellar clamp as set forth in claim 7 wherein said tubular
clamping jaw acts as a guide for said cutting element.
9. The patellar clamp as set forth in claim 8 wherein said tubular
clamping jaw is removably attached to said second part so that a
size of said jaw may be varied by providing a plurality of clamping
jaws of different diameters.
10. The patellar clamp as set forth in claim 7 wherein said
clamping jaw includes teeth for engaging the patella bone.
11. The patellar clamp as set forth in claim 1 wherein said second
part includes a scale indicating a posterior-anterior thickness of
said patella.
12. The patellar clamp as set forth in claim 1 wherein said cutting
element is an end mill.
13. The patella clamp as set forth in claim 1 wherein said cutting
element is a reamer.
14. The patellar clamp as set forth in claim 1 wherein said shaft
includes a stop surface for engaging a second stop surface on said
collar and upon engagement of said surfaces said collar first stop
surface is spaced from said first part second stop surface a
distance allowing a cutting face of said cutting element to be
positioned adjacent said first surface of said first part when said
collar first stop surface and said first part second surface
contact.
15. The patellar clamp as set forth in claim 14 wherein the
distance between said collar second stop surface and said shaft
stop surface element along said longitudinal axis is equal to the
bone remaining on the patella after cutting the patellar by moving
said cutting element until said collar first stop surface engages
said second surface of said first part.
16. The patellar clamp as set forth in claim 15 wherein said at
least one gage element has a plurality of steps of different height
for varying the bone remaining thickness on the patella by spacing
the second stop surface of the collar a desired distance from said
stop surface on said shaft.
17. The patellar clamp as set forth in claim 16 wherein the
distance between said collar first stop surface and said first part
second surface is equal to the bone to be removed from the
patella.
18. The patella clamp as set forth in claim 17 wherein said at
least one gage has a plurality of steps of different height for
varying the amount of patella bone removed by spacing the collar
first stop surface a desired distance from said first part second
surface.
19. A patella clamping system comprising: a first clamp part having
a reference surface engageable with an anterior surface of a
patella, said first part including a stop surface spaced from said
reference surface along an axis; a second clamp part moveable with
respect to said first clamp part along said axis; a cutting element
for resecting bone from a patella rotatably mounted on said first
clamp part and moveable with respect to said axis, said cutting
element having a first adjustable stop surface engageable with said
stop surface on said first clamp part; a first gage element for
setting the position of said adjustable stop surface with respect
to the reference surface on said first clamp based on the amount of
bone to be removed from the patella; and a second gage element for
setting the position of said adjustable stop surface with respect
to the reference surface on said first clamp based on the amount of
bone to remain on the patella.
20. The patellar clamp as set forth in claim 19 wherein said
cutting element includes a shaft having a stop surface for engaging
a second adjustable stop on said cutting element surface and upon
engagement of said surfaces, said first adjustable stop surface on
said cutting element is spaced from said first part stop surface a
distance allowing a cutting face of said cutting element to be
positioned adjacent said reference surface of said first part when
said adjustable first stop surface and said first clamp part stop
surface contact.
21. The patellar clamp as set forth in claim 20 wherein the
distance between said second adjustable stop surface and said shaft
stop surface along said axis is equal to the bone remaining on the
patella after cutting the patella by moving said cutting element
until said first adjustable stop surface engages said stop surface
of said first clamp part.
22. The patellar clamp as set forth in claim 21 further comprising
at least one gage element having a plurality of steps of different
height for varying the bone remaining thickness on the patella by
spacing the second adjustable stop surface of a desired distance
from said stop surface on said shaft.
23. The patellar clamp as set forth in claim 22 wherein the
distance between said first adjustable stop surface and said first
clamp part stop surface is equal to the bone to be removed from the
patella.
24. The patella clamp as set forth in claim 23 wherein said at
least one gage has a plurality of steps of different height for
varying the amount of patella bone removed by spacing the first
adjustable stop surface a desired distance from said first clamp
part stop surface.
25. A kit of instruments for preparing a patella for receiving an
implant comprising: a clamp having at least two carriers for
releasably mounting clamping elements; at least two cutting
elements of different size for engaging a posterior surface of the
patella and adapted for releasably mounting on said clamp; and at
least two clamping elements adapted to engage a peripheral surface
of the patella extending between the posterior surface and an
anterior surface of the patella said clamping elements adapted for
releasably mounting on said carriers.
26. The kit as set forth in claim 25 further comprising at least
two clamping elements of different size for engaging a posterior
surface of said patella, said two clamping elements adapted to
releasably engage at least one of said carriers.
27. The kit as set forth in claim 26 further comprising at least
two clamping elements of different size shaped to engage the
anterior surface of a patellar implant, said implant engaging
clamps adapted for releasably mounting on at least one of said
carriers.
28. The kit as set forth in claim 26 further comprising at least
two clamping elements in the form of drill guides for engaging the
posterior side of a patella, said drill guide adapted to releasably
engage at least one of said carriers.
29. The kit as set forth in claim 25 further comprising at least
two clamping elements shaped to engage the posterior surface of a
patellar implant, said implant engaging clamps adapted for
releasably mounting on at least one of said carriers.
30. The kit as set forth in claim 25 further comprising at least
one gage element for setting the amount of bone to be removed from
the patella during preparation and at least one gage element for
setting the amount of bone to remain on the patella after
preparation.
31. The kit as set forth in claim 26 wherein said clamping elements
for engaging the posterior surface of the patella have a tubular
shape.
32. The kit as set forth in claim 31 wherein a circumferential
surface of said tubular clamping element contacting said patella
has teeth for engaging patellar bone.
33. The kit as set forth in claim 25 wherein a bone contacting
surface of said two clamping elements engaging the periphery of the
patella include teeth.
34. The kit as set forth in claim 25 wherein the at least two
cutting elements are milling cutters.
Description
BACKGROUND OF THE INVENTION
[0001] A patellar clamp and reamer are used during a total knee
arthroplasty procedure to prepare the posterior surface of a
patellar bone to accept a prosthetic implant.
[0002] Typically, a surgeon will select to install a patellar
prosthesis either by utilizing a resurfacing technique wherein the
prosthetic patella will be positioned on the prepared surface of
the patella or by an insetting technique wherein the prosthetic
patella will be recessed or inset into the prepared surface of the
patella. Accordingly, two varieties of guides could be available
for connection to the patellar clamp and could be interchangeably
connectable to the clamp. The interchangeable guides permit a
surgeon to use the patellar clamp during either a total patellar
bone resurfacing procedure or a patella insetting procedure.
[0003] In either a total resurfacing procedure or a patella
insetting procedure, it is important that a sufficient amount of
bone stock remain after resection to accept the fixation pegs of
the patellar prosthesis and maintain the integrity of the remaining
patellar bone.
[0004] Prior art devices for aiding the surgeon in performing
patella resections are well known to those skilled in the art. For
example, Peterson, in U.S. Pat. No. 4,633,862, teaches a method and
instruments for the installation of a patella button prosthesis
which involves performing a patella resection.
[0005] In particular, Peterson describes a saw guide which
comprises a pliers-like instrument having a pair of mutually
pivotable jaw members. The jaw members are designed so as to enable
them to surround the outer periphery of the patella with each jaw
member having a respective handle, integrally formed therewith,
which handles may be pivoted so as to pivot the jaw members to and
from engagement with the patella periphery. At the ends of the
handles, a locking device is provided which enables the locking of
the jaw members about the patella periphery. The Peterson device
requires that a flat saw blade be guided over the face of the jaw
members after the patella has been set to the correct depth between
the members.
[0006] U.S. Pat. No. 5,147,365 relates to a patella osteotomy guide
in which the jaw members include a slot for guiding the flat saw
blade and an arm for setting the saw blade depth in the
patella.
[0007] Milling instruments are known in the preparation of the
femur for a prosthetic implant. One such milling system is
disclosed in U.S. Pat. No. 4,721,104 in which the area between the
condyles of a femur is shaped. U.S. Pat. No. 5,417,695 shows the
use of a milling instrument to prepare the condylar area of a femur
prior to receiving an implant.
[0008] U.S. Pat. No. 5,486,177 relates to a patella milling
instrument having a clamp which contacts the underside of the
patella. A similar clamping tool is shown in U.S. Pat. No.
5,284,482.
[0009] U.S. Pat. No. 5,222,955 relates to a reaming system designed
to cut a conical bore in a patella surface while the patella is
being held in a patella clamp similar to that disclosed in U.S.
Pat. No. 5,284,482.
[0010] U.S. Pat. No. 5,941,884, the teachings of which are
incorporated herein by reference, relates to a patella clamp which
includes indicia of both the amount of bone resected and the amount
of bone remaining. The resection depth is set via a stop collar on
a toothed extension. Corvelli et al. does not provide any method of
setting the depth of the patella milling based on the amount of
bone remaining. U.S. Pat. No. 5,575,793 is similar in that a gage
is provided to set the amount of bone to be removed.
SUMMARY OF THE INVENTION
[0011] It is an object of the invention to provide an improved
apparatus and method for facilitating the preparation of the
natural patella to receive a patellar prosthesis.
[0012] It is an additional object of the invention to provide a
clamping system which can hold the patella in position during
resection and which can be set to either resect a predetermined
amount of bone from the patella or, alternately, to set the depth
of the remaining bone on the patella.
[0013] It is an additional object of the invention to provide a
clamping system wherein various modular instruments may be easily
attached and removed from the gripping portion of the clamping
system.
[0014] These and other objects and advantages of the invention are
provided by a patella clamp which has a first part, including a jaw
reference surface engageable with an anterior surface of the
patella and includes a stop surface spaced from the patella
engaging surface. A second part is moveable with respect to the
first part and a cutting element also moveable with respect to
first part is provided. The preferred cutting element includes a
shaft having an adjustable collar mounted on the shaft for movement
with respect to the longitudinal axis of the shaft. The adjustable
collar is engageable with the stop surface on the first part for
spacing the cutting element a desired distance from the first jaw
reference surface. The collar position may be set with at least one
gage to limit the movement of the reamer based on either the
desired amount of bone remaining or the amount of bone removed. A
separate marker is provided for indicating the position of the
reamer with respect to either the patella bone remaining or the
amount of bone removed.
[0015] In a preferred embodiment, two gage elements are provided,
one for setting the position of the collar along the shaft with
respect to the first jaw patella contacting reference surface based
on the amount of bone remaining and one based on the amount of bone
removed. The two gage elements may either be independent of the
structure of the patella clamp or can be made part of the
clamp.
[0016] The shaft includes at one end a cutting element such as a
reamer or end mill which is used to shape the posterior surface of
the patella. At the other end the shaft includes a coupling portion
for engaging a rotary tool such as a drill chuck mounted on an
electric battery or air powered tool. The shaft has a collar
engaging portion with external ratchet like teeth which selectively
engage complementary internal teeth on the collar. The teeth on the
collar may be moveable into and out of engagement with the teeth on
the shaft so that the collar may be easily adjusted axially along
the shaft.
[0017] The second jaw part also includes a clamping element or jaw
which is tubular and has circumferential teeth for engaging the
bone of the patella. The cutting element may be cylindrical in
shape and extend within the tubular clamping jaw. Thus, the tubular
jaw holds the patella in position as the bone removal operation
with the cutting element progresses. Cutting of the patella
proceeds after the first and second part are locked in position
with the patella firmly clamped between the tubular clamping jaw
and the patella engaging surface which engages the anterior side of
the patella. The cutting element then moves independently of the
first and second clamping parts.
[0018] The tubular clamping jaw and the opposite engaging surface
mounted on the first part are removably attached to the body or
frame of the clamp. This permits not only different size clamping
parts to be utilized but allows for the use of other cutting tools
to be mounted on the clamp.
[0019] The shaft has a flange or stop surface for engaging a second
or outwardly facing surface of the collar and upon engagement of
the collar surface and shaft surface the surface of the collar
which contacts the stop surface on the first part is spaced from
the reference surface a distance allowing the cutting element base
to be positioned adjacent the reference surface engageable with the
anterior surface of the patella when the collar and said stop
surface contact. Thus, the distance between the flange and
corresponding collar surface is identical to the amount of the bone
remaining on the patella after the cutter removes bone until the
corresponding collar and first part stop surface is engaged.
Similarly, the distance between the collar stop surface and the
stop surface on the first part equals the amount of bone to be
removed.
[0020] A pair of gage elements are provided with each gage having a
plurality of steps of different height for varying for the bone
remaining or bone removing thicknesses for setting the position of
the collar along the shaft. The steps can be in 1 millimeter
increments with six (6) steps being on each gage element.
Obviously, fewer or a greater number of steps may be included. The
bone remaining thickness gage is inserted between the stop surface
on the collar and the stop surface on the first jaw part and the
bone remaining gage would be inserted between the flange on the
shaft and the top surface of the collar.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is an isometric view of the patella clamp of the
present invention including the reaming system for milling the
posterior face of the patella;
[0022] FIG. 2 is an isometric view of the patella clamp of FIG. 1
minus the reaming system;
[0023] FIG. 3 is an isometric elevation view of the patella clamp
of FIG. 1 including the reaming system with a patella mounted
therein;
[0024] FIG. 4 is an enlarged isometric view of the patella clamp of
FIG. 3;
[0025] FIG. 5 is an isometric view of the patella clamp of FIG. 1
including a modular drill guide template mounted thereon;
[0026] FIG. 6 is an isometric view of the drill guide template
disengaged from the patella clamp of FIG. 5;
[0027] FIG. 7 is an isometric view of the outermost portion of the
reaming system of the present invention including a bone remaining
depth gage;
[0028] FIG. 8 is an isometric view of the depth gage shown in FIG.
7;
[0029] FIG. 9 is an isometric view of the outermost portion of the
patella cutting system including a bone removing depth gage capable
of setting the amount of bone removed from the patella;
[0030] FIG. 10 is an alternate embodiment of the patella clamp in
which a pair of jaw members intended to grip the periphery of the
patella are provided; and
[0031] FIG. 11 is an isometric view of the patellar clamp of the
present invention including a modular clamp for engaging the
posterior surface of a polyethylene patella implant.
DETAILED DESCRIPTION
[0032] Referring now to the drawings, and especially to FIG. 1
thereof, an apparatus constructed in accordance with the present
invention is shown in the form of a patella clamp 20 having a frame
22. An upper arm handle 24 is affixed to the frame 22 and a lower
arm handle 26 is mounted upon the frame 22 at pin 28 for sliding
movement in a slot 33 of frame 22 toward and away from the upper
handle 24. A support platform 30 is attached to frame 22 at a lower
end 32 of a side bar 34 of the frame 22. Preferably, platform 30 is
removably attached to a carrier 43 which in turn is fixed to side
bar 34. A pin 35 mounts arm 24 to frame 22. Platform 30 includes a
bone contacting reference surface 36 extending laterally across the
upper surface of platform 30. Side bar 34 also include slot 33 in
which pin 28 slides. In the preferred embodiment, a patella
clamping member shown in the form of a barrel or tubular shaped
clamp member 40. Clamp 40 is attached to lower arm 26 by a modular
carrier 42 mounted for movement within slot 33 of side bar 34 via
pin 28. Clamp 40 is coupled with the lower handle 26 so that
pivotal movement of the lower handle 26 with respect to arm 24
about pin 39 will move the carrier 42 longitudinally along the side
bar 34 of frame 22 toward and away from platform 30.
[0033] As best seen in FIG. 3, the posterior side of a patella 50
which is to be prepared for the reception of a patellar prosthesis
(not shown), is held in a preparation position within the patella
clamp 20 by clamp 40 and platform 30. This is done by everting
patella 50 and applying patella clamp 20 to the everted patella,
with the handles 24 and 26 essentially perpendicular to the
mechanical axis of the leg. Alternatively, the patella may be
retracted by rotating it less 180.degree. and the clamp 20 applied.
Patella 50 includes an anterior surface 56, which contacts surface
36 of platform 30 and a posterior surface 58 facing clamp 40. The
patella 50 has a bone thickness extending between anterior surface
56 and posterior surface 58. The posterior surface 58 provides the
articular surface of patella 50 and is to be prepared for the
reception of a patellar prosthesis. In the preferred construction,
bone contacting surface 36 of the reference platform 30 includes
spikes 57 to contact and positively locate the anterior surface 56
of the patella 50. Clamp 40 includes teeth 63 around the bone
contacting rim 60 and is dramatically sized to extend around the
bony periphery of the patellar.
[0034] In the preferred embodiment, as shown in FIG. 2, the clamp
member 40 is modular and is removably coupled to carrier 42 of arm
26 by a snap connection 59. Likewise, platform 30 is preferably
removably coupled to carrier 43 of arm 24 by a snap connection 61.
Thus, two or more clamp members 40 of different size can be used.
When the clamp 40 is selected from a plurality of clamp members of
different size, the appropriate size is chosen so that arcuate rim
60 of clamp barrel 40 fits closely around the perimeter of patella
50 while resting upon the peripheral bone of patella 50.
Preferably, rim 60 includes a plurality of serrated teeth 63 to
hold the patella in position during milling. While only two
carriers 42, 43 are shown, additional carriers could be mounted on
arms 24, 26 if it was desired to include additional modular
instruments on clamp 20.
[0035] Clamp 20 is applied to patella 50 by moving clamp member 40
toward reference platform 30 until the bone of patella 50 is
engaged with patella 50 centrally positioned within rim 60 of clamp
member 40. At this point, the patella clamp 20 is secured in place
by locking the lower handle 26 against movement away from the upper
handle 24, as by a locking ratchet system with ratchet teeth 65
engaged by a trigger lock 67. Alternatively, as shown in U.S. Pat.
No. 5,941,884, a lock on one arm can engage a toothed locking rod
mounted to the other arm. In this design, a reliable lock button is
selectively actuated to release the lock to permit relative
movement of the arms and to lock the arms in the selected location
by engaging the lock rod.
[0036] Turning now to FIGS. 3 and 4, a bone-cutting tool is
employed in the resection of patella 50, and is shown in the form
of a reamer or end mill 80 having a rotary cutting face 82 which
engages posterior patella face 58, and a shaft 88 for rotating end
mill 80. In the preferred embodiment, end mill 80 is releasably
attached to shaft 88 by connector 89. Thus end mills of different
size can be attached to shaft 88 as desired. Shaft 88 is driven by
a modular adapter 84 which includes a drive socket 86 adapted to
engage a standard power tool such as a drill (not shown).
Preferably, shaft 88 is journaled for rotation in a bushing member
90, about a central longitudinal axis L of the bushing member 90.
Shaft 88 is free to move linearly within the bushing member 90 in a
direction along the longitudinal axis L. A first stop surface 98
extends laterally along the upper end of the bushing member 90. As
best seen in FIG. 7, a stop member in the form of a stop collar 100
includes a second stop surface 102 juxtaposed with and confronting
the first stop surface 98. Collar 100 can be adjusted along toothed
portion 104 shaft 88. Preferably, collar 100 is releasably engaged
with toothed portion 104 at the upper end of the reamer shaft 88.
The stop collar 100 is coupled to the toothed portion 104 of shaft
88 by a coupler which includes an actuator button 106 selectively
operated to release the stop collar 100. Stop collar 100 moves
longitudinally along the toothed portion 104 and button 106 is used
to selectively lock the stop collar 100 at a selected location
along the toothed extension 104, for purposes to be described
hereinafter. In the preferred embodiment, button 106 has internal
teeth (not shown) which selectively engage tooth portion 104 to
selectively permit movement of collar 100. Toothed portion 104
terminates at a flange 105. Flange 105 may include a socket 107 for
receiving modular drive adapter 84. In the preferred embodiment
flange 105, toothed portion 104 and the lower portion of shaft 88
are made of one piece. The markings shown may be etched on the
lower portion.
[0037] In the preferred embodiment, reamer 80, reamer shaft 88,
collar 100 and bushing member 90 together comprise an outrigger
cutting assembly 110 which is affixed to frame 22 via an attachment
92 as shown in FIG. 2. Attachment 92 is integral with frame 22. A
releasable connection including a pin 93 is coupled to assembly 110
so that assembly 110 may be releasably coupled to frame 22 of the
patella clamp 20 via attachment 92. This connection locates the
bushing member 90 accurately in position relative to the platform
30 reference surface 36 with the axis L intersecting the reference
platform surface 36 generally perpendicular to and at the
approximate center of the patella preparation position. Thus, the
longitudinal axis L is the axis of rotation of shaft 88 and reamer
80 as well as the center of clamp 40.
[0038] Once the outrigger cutting assembly 110 is secured to frame
22 of patella clamp 20, as illustrated in FIGS. 1 to 4, the reamer
80 is allowed to drop downwardly, with the reamer shaft 88, until
the cutting surface 82 of the reamer 80 rests upon the posterior
surface 58 of the patella 50, as shown in FIG. 4. At this point in
the procedure, the surgeon is able to determine the thickness of
the patella 50 merely by observing an indicator in the form of a
visible scale 120 on shaft 88 at the top of recess 122 on the
bushing member 90. Thus, as best seen in FIG. 4, as well as in FIG.
3, recess 122 is located accurately relative to platform 30,
reference surface 36 and scale 120 is calibrated in terms of
distance between cutting surface 82 of reamer 80 and reference
surface 36 on which anterior surface 56 of patella 50 rests. In
this manner, the surgeon is provided with a quick and accurate
direct intra-operative measurement which the surgeon will use to
determine the amount of bone to be removed during subsequent
resection of patella 50, without the necessity for introducing
supplementary instruments or interruption of the procedure.
[0039] Once the surgeon determines the amount of bone to be removed
during resection, the depth of resection is selected readily, again
intra-operatively, directly and without the necessity for
supplemental instruments or other apparatus. As discussed below,
the surgeon may set the amount of bone to be removed based either
on the desired amount of bone the surgeon wants remaining or the
amount the surgeon wants to remove. Referring now to FIGS. 3 and
7-9, the longitudinal distance between the first reference surface
98 and the second reference surface 102 determines the extent of
longitudinal travel of the reamer 80 as the reamer 80 resects the
bone of patella 50. Thus, by setting position of the stop collar
100 on the toothed portion 104, the depth of resection is
determined. The toothed configuration of portion 104 assures that
the stop collar 100 is moved in precisely determined fixed
longitudinal increments related to prescribed increments in the
depth of resection. Typically, the increments are provided with a
magnitude of one millimeter.
[0040] As seen in FIGS. 7-9, the depth of resection may be set in
two ways. First, as shown in FIGS. 7 and 8, a depth gage 300 may be
used to set the amount of bone remaining. Depth gage 300 includes,
in the preferred embodiment, six separate depth gage elements
302-312 which set the amount of bone remaining on patella 50 after
engagement of surface 102 and surface 98. In the preferred
embodiment, depth gage elements 302-312 start at a minimum of 11
millimeters and increase to 16 millimeters in 1 millimeter
increments. Thus, the thickness of the bone remaining may be varied
between 11 and 16 millimeters. The bone remaining is set by
adjusting the difference between upper surface 107 of stop collar
100 and the bottom of surface 109 of flange 105. This requires that
when surface 109 of flange 105 abuts surface 107 of collar 100 and
surface 102 then contacts top surface 98 of bushing 90, cutting
face 82 is flush with surface 36 of platform 30.
[0041] In the preferred embodiment, each gage element 302-312 is in
the form of a U-shaped recess 314 surrounded by a surface 316
recessed from top surface 318. The distance between surface 316 and
top surface 318 of gage 300 varies to produce a thickness between
the bottom surface and the surface 316 equal to the 11 to 16
millimeter desired bone remaining on patella 50. Alternately, the
amount of bone removed can be set with a gage 400 which is in all
respects similar to gage 300 (i.e., preferably includes six (6)
gage elements 402-412) with the exception that to set the bone
removing amount, the gage is inserted between surface 98 and
surface 102 of stop collar 100. In the preferred embodiment, gage
400 has the identical U-shaped recesses, however, the distance
between recessed surfaces 416 and top surfaces 418 are varied to
indicate the distance of travel between surface 98 and surface 102
during reaming and indicating how much bone is removed. This is
indicated on the top surface of the gage with the six (6) U-shaped
openings varying from -7 millimeters to -12 millimeters.
[0042] The surgical method of the present invention will now be
described. After exposing the patella in a standard manner, the
surgeon measures the patella thickness using any one of a number of
suitable instruments. Typical ranges of patella thickness as
measured between the anterior and posterior surfaces of the natural
patella vary from 8 to 40 millimeters and from 30 to 55 millimeters
in diameter. Referring to FIG. 2, the surgeon selects a properly
sized barrel shaped clamp member 40 and attaches it to carrier 42
which carrier is moveable in slot 33 of side bar 34 by the
actuation of handles 24 and 26. Platform 30 is then attached via
modular connection 61 to carrier 43 which carrier is stationary
with respect to side bar 34 and carrier 42. As indicated above, a
plurality of different size clamping barrels 40 may be used so that
the periphery of various size patellas may be engaged. In the
preferred embodiment, five (5) clamping barrel sizes from 34
millimeters to 50 millimeters in 4 millimeter increments are
included in a kit. The teeth 63 of barrel 40 are designed to engage
the patella and not the surrounding ligaments. As seen in FIG. 2, a
ratcheting mechanism 65, 67 is provided so the surgeon can lock the
relative position of carriers 42 and 43 once the patella is firmly
clamped as discussed below.
[0043] The surgeon now assembles the reaming or milling assembly
110 by choosing a resurfacing patella cutter which matches the
clamping barrel 40 size. The assembled cutting assembly 110 is then
assembled to frame 22 by means of a connection 92, 93. In the
preferred embodiment, the lock is obtained when an audible click is
heard, i.e. pin 93 engages extension 92 on frame 22. Of course, any
connection
[0044] The assembled patella clamp is then applied to the everted
or retracted patella 50 with the handles 24, 26 with axis L
preferably perpendicular to the long axis of the leg. As stated
above, the teeth 63 of barrel 40 are moved by the movement of arms
24, 26 towards one another into engagement with the peripheral bone
of the patella 50. The ratchet mechanism 65, 67 may be then
utilized to lock the clamp in position. Reamer or end mill 82 is
then moved into position contacting the posterior surface 58 of
patella 50. The current patella thickness is shown on scale 120 as
best seen in FIG. 4. The surgeon then has two choices for
determining the amount of bone to resect from the patella
articulating surface. He may either decide to use the bone
remaining method as shown in FIGS. 7 and 8 or the bone removing
shown in FIG. 9. As indicated above with regard to gages 300 and
400, there are preferably 6 different bone remaining or bone
removing options. With regard to gage 300 the 6 options are 11
millimeters to 16 millimeters in 1 millimeter increments. The
utilization of gage 300 as shown in FIG. 7 will determine how much
bone the surgeon wishes to remain on the patella. Bone gage 300 is
placed on shaft 104 in contact with upper surface 111 of stop
collar 100. U-shaped opening 314 must sit flush with reamer shaft
111 and must be placed top flange 105 and top surface 107 of collar
100. Of course, depth gage 300 must be removed prior to
milling.
[0045] The surgeon also may wish to set the resection level based
on the amount of bone removed. In this situation, a gage 400, as
shown in FIG. 9, is utilized in a similar manner to gage 300 with
the exception that it is located between surface 98 of bushing 90
and bottom surface 102 of stop collar 100. In the preferred
embodiment, the six (6) depth removing gage portions include six
(6) different bone removing options, -2 millimeters and -8
millimeters to -12 millimeters in 1 millimeter increments. The bone
removing depth gage 400 is designed so there can never be less than
10 millimeters left of bone. Again, the U-shaped portion 414 must
sit flush around reamer shaft 104 to ensure that the proper depth
is set.
[0046] Once the depth has been set by locating collar 100 based on
either the desired bone remaining or the desired bone to be
removed, the drive 84, 86 is coupled to recess 107 in flange 105
and the reaming operation is commenced. Reamer 80 is simultaneously
rotated and advanced. The reamer shaft is advanced until surface
102 of collar 100 contacts surface 98 of bushing 90. The remaining
thickness of the resected patella 50 may then be read from scale
120 on shaft 88. Should the surgeon determine that further
resection is required, the stop collar 100 is merely reset to the
desired further amount of resection and the reamer 80 then is
advanced through the corresponding further amount of linear travel.
Once reaming is complete, the surgeon unlocks the ratchet lock
using trigger mechanism 65, 67 and releases pin 93 so that the
outrigger assembly 110 may be removed thereby exposing the newly
created resected surface 130 of the resected patella 50 as shown in
FIG. 6. Resected surface 130 is essentially planar and normal to
axis L.
[0047] Referring to FIGS. 5 and 6, fixation hole placement can be
done in a well known manner utilizing the drill template 140 and
the drill assembly 141. To accomplish this, barrel clamp 40 is
removed from carrier 42 and the template 140 which includes a
connector 59, is inserted into place in carrier 42. Again, in the
preferred embodiment, there is a series of drill templates for
various size prosthetic patellas with the template chosen providing
the most complete coverage of the resurface patella without any
overhang. With patella clamp 20 secured in place so that the drill
template 140 is located in position against resected surface 130,
as illustrated in FIGS. 5 and 6, an assembly 141 including drill
142 is advanced through the apertures 144 in the drill template 140
for appropriate location of holes in patella surface 130. These
holes correspond to the lugs of a typical patellar prosthesis (not
shown). As is well known, a trial prosthesis may be placed on
surface 130 of the resected patella 50 and the overall
anterior/posterior thickness may be measured to determine whether
the proper patella thickness has been restored. The patella
tracking can then be assessed prior to the permanent implantation
of the prosthetic patella implant. Normally, the prosthetic patella
is made of polyethylene and a clamping element shown in FIG. 11 may
be provided for attachment to arm 26 and used in a manner similar
to barrel clamp 40 and drill template 140. Referring to FIG. 11
there is shown a clamp part 500 for pressing on the posterior side
of the patellar implant 502 while clamp platform 30 presses on the
anterior bony portion of the patella. This clamping can be
performed during the curing of bone cement holding the polyethylene
implant to the prepared patella surface. Also shown in FIG. 11 are
release buttons 504 which are used to disengage the various
clamping elements from carriers 42, 43.
[0048] Thus, after forming the holes, template 140 would be removed
and a modular clamp shaped to receive the posterior surface of the
polyethylene implant would be mounted on connector 42. The
activation of handles 24, 26 then applies pressure on the implant
forcing, in the preferred embodiment, the three lugs on the implant
into the three drilled holes. The implant may be either press fit
or cemented into place on the remaining bone of the patella. If
cementing is used, the clamp 20 may be utilized to maintain
pressure while the cement cures (see FIG. 11).
[0049] Referring to FIG. 10 there is shown an alternate embodiment
of the patella clamp of the present invention. The body of the
clamp including handles 24, 26, frame 22, carriers 42, 43 remains
the same. However, instead of platform 30 and barrel shaped
clamping member 40, a pair of arms 200, 202 are provided with
connection portions similar to 59 and 61. Thus, prior to insertion
of plate 30 and member 40 or after the removal of plate 30 and
barrel member 40, arms 200, 202 are snapped into position in
carriers 42, 43. Arms 200, 202 have bone engaging teeth 204
designed to engage the periphery of the patella. The clamp can now
grip the periphery of a patella. A saw guide 206 can be attached to
either or both arms 200, 202 for guiding a saw blade (not shown).
Thus, after arms 200, 202 securely grip patella 50, the posterior
surface thereof may be resected in a known manner. Arms 200, 202 of
different size can be provided and may be provided as part of a kit
which may include all or some of the clamp 20, two or more
platforms 30 and clamp elements 40 of different size, gages 300,
400, and two or more clamps 500 and two or more cutters 80.
[0050] In the preferred embodiment, buttons 304 have recesses
designed to receive and lockingly engage elements 59, 61. Buttons
504 are spring loaded so that when the buttons are released they
lock onto pins 59, 61. Depressing buttons 504 then releases the
pins 59, 61 so that the modular instruments/clamping elements may
be removed. A similar system is used to releasably mount assembly
110 to pin 92 via button 93.
[0051] 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.
* * * * *