CA1324548C

CA1324548C - Apparatus for knee prosthesis

Info

Publication number: CA1324548C
Application number: CA000589770A
Authority: CA
Inventors: Matthew Paul Poggie; Peter Stanley Walker; Frederick Conrad Ewald
Original assignee: Howmedica Inc
Current assignee: MTG Divestitures LLC
Priority date: 1988-02-03
Filing date: 1989-02-01
Publication date: 1993-11-23
Anticipated expiration: 2010-11-23
Also published as: EP0474320A1; DE68901386D1; DE68923566T2; ATE75592T1; DE68923566D1; EP0327249B1; ATE125140T1; JPH0548699B2; EP0327249A2; US5002547A; DE8901069U1; EP0327249A3; JPH01250250A; EP0474320B1

Abstract

ABSTRACT OF THE DISCLOSURE
A modular apparatus for use in the preparation of bone surfaces and the implantation of a modular total knee prosthesis in a patient, which apparatus comprises cutting guides, templates, alignment devices, a distractor and clamping instruments which provide modularity and facilitate bone resection and prosthesis implantation.

Description

` ~324~8 1 54680~475 Apparatu fGr Knee Prosthesis The present inventlon relates to apparatu~ for a knee prosthe~is. More particularly the invention i~ concerned with a modular apparatus ~or u~e ln the preparation of bona ~urfaces and the implantation of a modular total knee pro~thesis.
The human knee ~oint i~ ubject to greater stre85 than any joint in khe body. Thi~ i8 becau~e lt mu~t bear the full weight of the body, o~ten at di~advantageou~ leverage ratlo~.
Consequently, there ls a premium OD the design o~ a pro~the~is ~or replacement of the knee joint.
Additionally, the implan~ation o~ a prosthe~is should avold resection of any more of the ~olnt than is strictly necessary. ~his is especially true of the knee which include~
ligaments within the ~oint, i.e., the aruciate ligaments which are important for the future functioning of the joint, and, therefore, in the design of the prosthesis lt is important to keep the thickne~s of the prosthe~ls to a minimum ~o a6 to avold re~ection, but yet to do ~o without sacrlficing consistent and lo~g term adequate performance.
: 20 Other faators to be con~idered in the de~ign of a knee prosthe~is include the need to anchor lt against the ~orces of ~hear, tipplng, and torque to whlch the knee jolnt i~ particularly 3uscaptible.
Furthermore, it is desirable to standardlze the manner ln which the prosthesis is implanted and to provi~e in~rumentation by which the tibial plateau a~d femur are resected in such a way as to make the e~ci3ions flt with the components to be applied to the plateau.

1~24~48 2 6~80-~75 The present invention 1~ concerned with improved instrumentation to facilitate lmplantation of a total knee prosthesi~ such as diYclosed in (but not limited to) the aforementioned applications.
In accordance with ~he present invention there i8 provided a modular apparatus for u~e ~n the preparation o~ bone surface~ an~ the implantation of a modular to~al knee prosthe~is in a patient, whl~h apparatus comprisesl (a1 an extendable rod having a di~tal end and a proximal end, means for ad~usttng the length of the rod, means for adjusting the lateral alignme~t and angular orie~t~tion of the proximal end of the rod, clamp mean~ agsociated wlth ~he di~tal end of ~aid rod for cla~ping said distal end to the ankle region of the patient'~ leg and combination fixing ~ean~ and cutting platform as~ociated with said pro~imal end of the rod for at~aching ~ald proximal end to the upper end of the pa~ienk's tibia while aligning the cutting pla~form close to the tlbial plateau;
(b) an ad~u~table stylu~ ~or allgning said cutting platform at the correct level for resecting the tibial plateau;
(c) a modular ste~in ~e~plate for determlning the perlpheral size of the resected proximal tibia and : .

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including a raised cylindrical hollow tube for aligning a stem/fin punch;
(d) a stem/fin punch comprising a central hollow cylindrical ~ube with a dis~al chisel edge and two fins extending radially from said tube at a predetermined angle and each having a distal chisel edge;
(e) a push rod which fits into said hollow cylindrical tube of said stem/fin punch;
(~) an alignment fork attached to an intramedullary rod adapted to be introd~ced into a medullary canal of the patient;
(g) a femoral distractor comprising a handle, a rail adapted to slide onto the alignment fork, a lateral arm and a medial arm, each of which:has associated means for separately raising and lowerlng each-arm;
(h) a drill guide adapted to slide along the rail of the femoral distractor and having a plurali~y of holes for accepting locating pins;
(i) a distal cutting guide comprising a flat plate 20: having a top surface and a bottom-surface and integral1anges extending from said bottom surface and each being.
inset from one edge of said surface~ each of said flanges having a locating hole extending therethrough;
~;) a modular cutting guide for guiding a s~w blade to make cuts required or a femoral component prosthesis, comprising a substantially rectangular rame having a top wall and a bottom wall, each of said walls being defined by substantially parallel planar outer and inner surfaces, wherein each outer ~urace provides a flat cutting plane and the inner surfaces define an open window within which is ~ocated:an intermediate solid : block having an.angled top~sur.ace and an angled bottom surface, each:of said angled surfaces providing -a-guide f~r ma~ing a chamfer cut; said:angled top surface being : 35 spaced apart from the top inner surface of said window : -4- ~3~ g and said angled bottom surface being spaced apart from the bottom inner surface of said window by gaps which provide a surgeon with a clear view of the surfaces being cut.
(k) a femoral sizer for determining ~he size of ~he patient's femur, comprising a body portion having locating holes, a central tubular orifice for accepting a feeler elemen~ and indicating means for indicating the depth of the feeler elemen~ within said orifice when the sizer is located on the patient's femNr, thereby providing a determination of the sizer required for a modular cutting guide;
(1) a reamer guide for.correct location of a reamer for preparing a cavity to locate a femoral proqthesis peg, which reamer guide comprises a flat plate having a top surface and a bottom ~urface, a hole extending through ~he plate~ a tubular bushing ex~ending from said top surace and lined up with said hole and locating pegs extending from said bottom surface;
~m) a patella resection gui:de comprising a -scissor-type clamp having- distal~ gripping arms, ~ach of said arms defining a cutting surface and gripping teeth, said gripping teeth being inset below the plane of the associated cutting surface;
(n) -a patella handling instrument providing alternative template and clamping functions comprising a scissor-type member having a first pivotal arm with a distal end and a ~econd pivotal arm with a distal end;
the first arm having a swivable platform located at its distal end, the surface of said platform facing inwardly toward said second arm and said second arm having means to interchangeably grip and hold either~ -i) a modular patella templat~-having holes-to-accept-drill~ or (ii) ~-clamp member adapted-t-o clamp.a patella prosthesi~ to a resected patella.

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1 3 2 ~ ~ ~ 8 64680-475 The total apparatus deflned above is a novel and unique combination of numerous elementæ ~ome of which are novel per ~e and some of which are modified and improved versions of instruments whlch performed slmllar functions in the prior art.
However, the overall ef~ec~ of the pre~ent novel combination apparatu~ is to facilitate bone preparation and pro~hesis implantation and also provide a degree of modularity hitherto unknown.
The inventlon alrso provides a fe~oral distractor of the type to be mounted on the end of a medullary alignment rod placed withln the femoral ~edullary canal compri~ing: a handle; a body having an anterior ~urface thereof connected to said handle, said body having a key element ~ormed thereon ~or ælidably receiving an end o~ the medullary alignment rod to align the femoral di6tractor with re~pect to the femur; a movable medial arm and lateral arm operatively connected to said body and extending posterlorly and generally parallel to a ~ur~ace o~ said body whlch ls g~nerally perpendiculax to the anterlor surface thereof~ and mean~ mounted wlthin ~aid body for independently rai~ing and lowering said medlal and lateral ar~s.
The lnvention ~urther provide~ a modular cutting yuide for guiding a saw blade to make cuts requlred for a femoral componant of a total knee prosthesis, co~prising a sub~tantially rectangular ~rame having a top wall and a bottom wall, each of ~aid wall6 belng defined by substantially parallel planar outer and lnner sur~aces wherein each ou~er surface provid~s a flat cutting plane and tha inner surface~ deflne an open window within which i~ located an lntermedlate r~olid block havlng an angled top r~3 ' ., , .

Sa 13 2 4 5 4 8 64680-475 surface and an angled bottom surface, each of ~aid anyled surfaces providing a guide for making a cham~er cut, sald angl~d bottom surface being spaced apar~ from the bottom inner æurface of ~aid block, defining said wlndow, a ~irst di~tance greater than the ~hlckness of the saw blade, and ~aid angled top sur~ace being spaced apart fro~ the top inner ~ur~ace of said block, defining said window, a distance greaker than said fir~t distance to provide a surgeon with a clear view o~ the æurfaces being cut.
De~cription of the Drawin~s Preferred embodlments o~ the variou~ elements of the present apparatus are illus~rated in the acco~panying dra~ings in which:-Flgure 1 i~ a ~ide elevation o~ a combination extendable rod, integral cutt~ng platform and ankle clamp according to the invention;
Figure 2 1~ a side elevatlon af the solid ex~endable rod and cuttlng platform of Flgure l;
Figure 3 is a bottom plan view of the cutting platform o~ Figura l;
Figure 4 is a top plan view of ~he ankle clamp and extension rail of ~he allgn~ent in~trument of Figure l;
Figure 5 i8 a side elevation of an adjustable ~tylus accor~lng to the lnvention;
Figure 6 is a top plan view of a modular stem~fin template;
Figure 7 ls a side elevation of the templa~e of Figure 6;

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- . . . - , Sb 132~5~8 64680-475 Figure 8 i~ an end elevation of the ~e~plate of Flgure 6;
Flgure 9 i~ a side elevation o~ a ~tem/fln punch;

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Figure lO is a plan view of the stem/fin punch of Figure 9;
Figure 11 is a-side elevation of a push rod;
Figure 12 is a side elevation of an intramedullary rod and alignment fork;
Figure 13 is an end elevation of the rod of Figure 12, showing the alignment fork.
Figure 14 is another æide eleva*ion of the rod of Figure 12 showing the angulation of the rod relative to the fork; . . - -Figure 15 is a side elevation of a femoral distractor;
Figure 16 is an end elevation of the distractor of Figure lS;
15 Figure 17 is a bottom plan.view of the distractor of Figure 15;
Figure 18 is an end elevation of a modular drill .
guide;
Figure 19 is a bottom plan view-o~.the drill guide Of Figure 18; - ..
Figure-20 is a side elevation of-a dis~al-cut~ing guide or distal femoral resection:guide;.. :
Figure 21 is an end elevation of-the guide of Figure 20; - - -25 Figure 22 is a bottom plan view of the guide of Figure 20;
Figure 23 is a front elevation of a modular cutting guide incorporating an anterior/posterior and chamfer resection guide;
30 Figure 24 is a cross-section through B-B o~ Figure 23; .................................................................... .- . Figure 25 is~ a .ron~ elevation.of a femoral sizer;
- Figure 26 is--a side elevation-o~ th~ izer-o Figure 25;:

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- , . , Figure 27 is a side elevation of a reamer guide positioned against a femoral template.
Figur~ 28 is an end elevation of the reamer guide of Figure 27 Figure 29 is a side elevation of a reamer for -rea~ing the cavity to accomodate a femoral peg;
Figure 30 is a plan view of a patella resection, guide and clamp;
Figure 31 is a partial side elevation of one of the jaws of the patelLa rssection guide o~ Figure 30;
Figure 32 is a side elevation of a patella handling instrument holding a patella template;
Figure 33 is a plan view of a modular patella template for use wi~h the instrument of Fîgure 32;
Figure 34 is a side elev~tion of patella drill with stop for use w~th the te~plate of Figure 33; - .
- Figure 35 is an enlarged sectional view,of a quick-connect device-for interchanging and retaining .
elements of the,ins~rument of.Figure 32, ,~,~
-Figure-36 is a side elevation of an instrument of Figure 32 but with,a cl,amp member in place of the patella template; - . -; , Figure 37 is a plan view of the rlamp element of Figure 36; , ,, Figure 3B is a side elevation of a femoral .
stabilizer box chisel;
Figure 39 is a top plan view of the chisel of Figure 38; and Figure 40 is an end elevation of the chisel of Figure 38.
Figures 41 to 55 are schematic representations illustrating the manner in whieh the instrument,ation--i.llustrated in the ab.ove-~escrib~d.-drawings is utilized to prepare.bone surfaces and the procedure~ illustrated .
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,, , in these schematic drawings will be described in more detail hereinafter.
Referring to the embodiments illustrated in the drawings, Figure 1 illustrates an instrument for the correct alignment of a cutting surface to facilitate the resection of a tibial plateau 43 (see Figure 43) to receive a tibial implant, which instrument comprises an extendable rod 10' having a hollow distal portion 2 and a solid proximal portion 3, said distal portion comprising a hollow cylindrical tube 2 and said proximal portion comprising a solid cylindrical rod 3 which slidably fits wi~hin said hollow cylindrical tube and means or locking the slidable rod within said tube when the desired overall length is achieved. In the preerred embodiment said means for locking the slidable solid rod 3 within the hollow cylindrical tube 2 comprises a locking screw 4 which tightens within a groove 5 ex~ending longitudinally along said solid rod, the locking preventing both rotational and longitudinal movement. The proximal end of the solid rod h~s a prede~ermined radius of curvature R and terminates in an integral cutting platorm 6.-defining a flat cutting surface 1. The distal end of said hollow cyLintrical tube terminates-in a bearing 7 which slides radially along a rail 8-extending -substantially perpendicularly from a flat-plate.9 located in a groove 10 within which said plate may slide .
laterally, said groove being integral with a p.air of tension spring clamping jaws 11, said radial and lateral sliding movement providing means for correctly..aligning said cutting platform close to the tibial plateau.
Each of the jaws 11 open and close about a pivot 12 at the end of an arm 13 and is held in a gripping position.by a-tension spring 14.: .
A~ sh.own in Figure 3, the cutting platform 6 has an improved slim configuration and an inner curved profile - : ': , . . .
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15 adapted ~o fit against the tibia. I~ also has a central hole 16 adapted to accept the peg 17 of a stylus holder (Figure 5) and holes 18 to accept location pins.
The distal portion of the instrument illustrated in Figure l also carries a solid site guide 19 having a 5 site for correctly aligning the instrument relative to the tibia of a patient.
Figure 5 illustrateR an adjustable stylus 20 for use in combination with the cutting platform 6 of the instrument illustrated in Figures 1-3, which comprises a solid base portion 21 having an extending peg adapted to be loca~ed in a cooperating hole in said cut~ing platform 6 to mount said base portion upon said cutting platform, an arm 22 extending upwardly and at an angle from said base, said arm having a distal end-with a female screw thread 23 therein, and a stylus arm 20 having a distal end and a proximal end with a male screw thread 24, said male screw thread of the stylus arm being mated with the .... . ... .
female screw thread of the upwardly extending arm, so ~0 that when the distal end of the stylu~ arm touches the ti~ial plateau 43 the cutting platform may be locked in its correct alignment or resection of the plateau and the stylus arm may then be-wit~drawn by unscrewing at its proximal end without dis~urbin-g the alignmen~ 0f the cuttin~ platform.
Figures 6 to 8 illustrate a modular stem/fin template 25-for determining the peripheral size o~ a resected proximal tibia comprising a handle 26 carrying the te~plate. The handle has a hole 26' which enables it to be ~lidably mounted on an alignment rod (see Figures 44 and 45). The template, which may come in different sizes according to size o the tibia has a cut out por~ion 27 to accommodate t~e cruciate ligaments, and comprises a solid flat plàte 25 deining the periphery of the-~esPcted proximal tibia, a raised cylindrical hollow . t . . ~
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tube 28 comprising a circular hole 29 to accept a stem punch tFigure 9) and slots 30 radiating from said hole to accept a fin punch for aligning a stem/fin punch and also including an enlarged circular hole 31 for a drill around the end of each fin slot distal from said stem hole.
Figures 9 and 10 illustrate a stem/fin punch 32 comprising a central hollow cylindrical tube 33 with a distal chisel edge 34 and two fins 35 extending radially from said tube at a predetermined angle and each having a distal:chi~el edge. The proximal end of the punch terminates in a circular pla~e 37 adap~ed to be struck by a surgeon's mallet for punching out the bone to receive the stem and fins of a tibial implant..
The side of the cylindrical tube ~as a.slot 38 into which a pro~ecting peg 39 (Figure 7); in the raised cylindrical ho~low.~tube of the template may key thereby ensuring proper alignment of the punch within the template. ~.
Figure 11 il~us~rates. a solid push rod 40 which.~fits into the hollow cylindrical tube-of the stem/fin punch.
Figures 12 ~o:14 illustrate an alignment fork 41 attached to an intramed~llary rod 42 adapted to be introduced into a medullary canal of the patient;
. .Figures 15 to 17 illustrate a femoral distractor comprising a handle 44 having a vertical hole 45 there through for-accomodating`an alignment rod.(.not shown) a rail 47 adapted to slide onto an alignment fork,~a lateral arm 48 and a medial arm 49. Each arm may be separately raised or lowered by a rack and pini.on mechanism 50, operated by a turn key 51.
Figures 18 and 19 illustrate a drill guide 52 having a bo.ttom groove 53 adapted to slide.along the rail of the femoral distractor and-~aving a plurality of holes 54 for accepting locating.pins (not shown).
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Figures 20 to 22 illustrate a distal cutting guide comprising a flat plate 55 having a top cutting surface 56 and a bo~tom surface 57 and in~egral flanges 58 extending from said bottom surface and each being inset 59 from one edge thereof, each of said flanges having a locating hole 60 extending therethrough.
Figures 23 and 24 illustrate a modular cutting guide for guiding a saw blade to make cuts required for a femoral component of a total knee prosthesis, comprising a substantially rectangular frame 61 having a top wall -whose outer surface provides a flat top cutting surface 62 and a bottom wall whose outer surface provid~s a flat bottom cutting surf-ace 63 and, located betw~en said top surface and said bottom surface, an in~ermedia~e solid block 64 having an angled top surface 65 and an angled bottom surface 66,`each of said ang-led surfaces providing a guide for making a chamfer cut. ~he-open gaps 64' --between the angled top surface 65 and ~he inner surface of ~he top wall and between the angled-bottom surface 66 and the inner surface of the ~ottom wall providing windows which enable the surgeon to have.a clear view of the surfaces being cut. The intermediate solid cu~ting block carries pegs 67' f~r locating the guide in predrilled holes on the femur. The guide is held by handles 67 projecting from the sides of the block.
Figures 25 and 26 illustrate a femoral sizer for determining the size of a patient's femur to prepare it for resection to receive a modular femoral prosthesis comprising a body'portion 68 having locating holes, a central tubular orifice 69 for accepting a feeler element 70 and-indicating means for indicating the depth of the-eeler--element ~i,thin said orifice when ~he sizer 71 is located on the pa~i'e'n~5 femur, thereby providing-a determination of the size required for a modular cutting 35 ' ~uide. '' , . . .
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Figure6 27 and 28 illustrate a reamer guide for correct location of a reamer (Figure ~9~ for preparing a cavity to locate a femoral prosthesis peg9 whi~h reamer guide comprises a flat plate 72 having a top surface 73 and a bottom surface 74, a hole 75 extending through the plate, a tubular bushing 76 extending from said top surface and lined up with said hole and locating pegs 77 extending from said bottom surface.
Figure 29 illustrates a reamer having cutting edges 78 for reaming a cavity to accep~ the stem of a femoral component prosthesis.
Figures 30 and 31 illustrate a patella resection gulde compr~sing a scissor-type clamp 79 having distal gripping arms 80, each of said arms defining a cutting lS surface and gripping teeth 8~, said gripping teeth being inset 82 below the plane 83 of the associated cutting surface.
The proximal end of the device has a ratchet arm 84' to prevent the clamp from slipping, Figures 32, 33~ 35, 36 and 37 illustrate a patella handling instrument having an interchangeable modular template and clamp, comprising a scissor~type member 84 having a first pivotal arm 85 wi~h a distal end and a second pivotal arm 86 with a distal end, said first arm having a swivable platform 87 located at its distal end, the surface 88 of said platform facing inwardly toward said second arm and said second arm having means 89 to interchangeably grip and hold either:- (i) a modular patella template 90 havlng holes to accept drills, or (ii) a clamp member 91 adapted to clamp a patella prosthesis to a resected patella.
The preferred means for interchanging the template and the clamp member is a quick-connect device illustrated-in detail-in Figure 35. -., .

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132~5~8 The quick connect device comprises a compr2~sion spring 92~ a ball 93, a coupling 94 and a retalning ring 95.
Figure 34 illustrates a drill bit 96 wi~h a chisel edge 97 and a stop 98 for drill holes in a patella u~ing the template illustrated in fi~ure 33.
Figures 38 to 40 illus~rate a femoral stabilizer box chisel for excavating a bone to accept a posterior stabilized femoral component which comprises a handle 99, a anterior ~kid 100 extending from Qaid handle and a box chisel 101 extending parallel to said skid 100 and having a cutting pro~ile for cutting the required cavity to accept the peg of ~he stabilized component.
The surgical procedure for utilizing the instrumentation of the pre~ent invention will now be described with reference to the schematic drawings of Figures 41 to 55.
~1) Cutting the proximal tibia.
The patient's knee is flexed past 90n,and the tibia is drawn forward. A~ shown in Figure 41 the lower clamp arm~ 11 of th~ upper tibial cutting guide 6 are opened and clamped around the ankle joint proximal to the medial malleolas. The distal end has two adjustments, one each for anterior/posterior (A/P) and medial/lateral (M/L).
The alignment tube 2 may be shifted about 2.5 ~m. to compensate for the presence of the fibula. The tube i8 slid along the AtP rail 8 to a specified mark to establish a 3~-5 posterior slope. The site guide 19 on the anterior surface of the tube serves as a vi~ual aid.
The level of the cutting platform is positioned relative to the lowest point on the tlblal plateau uslng the tibial ~tylu~ a~ a guide. Two 1~8" pins are u~ed to fix the cutting platform.to the proximal tibia ~o that --accurate bone cuts can be-m~d~.

- . ~ -~32~5~8 The curvature R in the rod which connects the cutting platform to the alignment tube mimics the posterior angulation o. the proximal tibia. This positions the cutting platform close to the ti~ial plateau and will allow a standard sized saw blade to cut the entire surface of the proximal tibia. The cutting platform is contoured to match the curvature of the anterior tibial plateau.
Pre~aring a Site.for the Prosthesis The peripheral.s.ize of ~he resected proximal tibia is determined using the stem/fin punch templates (Figures 44 and 45). The size which best covers ~he peripheral cortical rim is chosen. Using the alignment-rod through the hole in the handlej--rotational alignment o~ the template is established by lining up the align~ent rod and tibial shaft in the ~rontal plane. The two captured pins are tapped inbo the proximal tibia to securP the-template. The appxopriate sized stem/fin punch is chosen and introduced into the cylindrical projection on the temylate. Rotational.orientation of the punch is established.by engaging the wings within the slotsrin the cylinder. Using a mallet the punch is driven into the tibia until the driving platform bottoms on ~he top;)of the cylinder. Because the stem-portion of the punch.is hollow, cut bone will fill this space. Choose the appropriate size plug pusher 40 and drive it into the bone of the punch stem (Figures.ll and 45). This will force the bone which-occupies the space distally, compacting it. This bone will serve as a cement restrictor in the event that bone cement is utilized in the fi-xation of the tibial baseplate. When bone cement is use~, two holes 31 are drilled in the medial-.and lateral plateaus,-using the-holes 31 in the template as a : guide for the drIll bits 102 which have been marked with an appropriate depth stop (Figure 44).

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Femoral Preparation The lateral anterior prominence is resected from the distal femur for better seating of the distal femoral cutting block to be used later. A 5/16" (8 mm) starter hole is drilled in line with the medullary canal. The location of the drill hole should be midway between the medial and lateral femoral condyles just anterior to the origin of the posterior cruciate. The direction of the drill bit should be in line with the longitudinaly axis of the femur in both planes. The right or left alignment fork is introduced into the medullary canal (Fig~res 46).
The femoral distractor is slid onto the alignment fork and the leg extended (Figure 47). The distractor is now keyed to the-emur at the appropriate angle of valgus from the mecha~ical axis in the frontal plane and perpendicular in the sagittal plane.
Care is taken that the femoral distractor is sitting flush on the cut proximal ~ibia. Distract the lateral and medial arms of the distractor up to the femoral condyles with the knee in full extension. If the lateral and medial ligamen~s are~imbaLanced9 carry out appropriate soft tissue releases at this ~ime. Overall leg alignment can be-furt~er checked with:the long-alignment rod through the ~andle of the distractor. The alignment rod should bisect the malleoli distally and be one inch medial to the anterior-superior spine proximally. Read off the tibial thickness markings as seen in FigurP 47, and select the lower value between lateral and medial.
Slide the drill-guide up to the anterior femur and tap two 3 mm p-ins through the holes corresponding to the just selec~ed ti~ial thickness (Figure 48).
S~i~e ~he drlll guide off~ leavingith~ pins-in place. Relea~e the tension on the distractor and remove.
Flex the knee to 90~ and remove the alignment fork.

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Slide the distal cutting guide onto the pins. The block is stepped to allow the cutting surface to sit close to the surface to be cut. Using an oscillating saw, resect the distal femoral condyles. The cut should be perpendicular to the long axis of the femur in the sagittal plane, and in the appropriate degree of valgus (Figure 49).
Maintain the leg in 90 of flexion and insert the distractor so that it rests flat on the cut proximal tibia. Distract to the same amount as in extension, or slightly less if a more lax posterior cruciate ligament is preferred. ~lide the drill guide flush with the cut distal surface and tap two 3 mm pins thru the previously selected holed (Figure 50). Slide the drill guide off, release tension, and remove the distractor.
Slide the body of the A-P sizer onto the pins (Figure 51) and engage the feeler into the hole in the body. Lower and rotate the feeler until it touches the high point of the anterior cortex. Read the appropriate femoral size by sighting the level of the hash mark.
Remove`the ins~rumen~ and pins.
Select ~he appropriate size A-P/chamfer combo block (Figure 52), and engage the fixed pins-in the under~ized holes in the distal femNr. Tap the block until it sits flush against the distal femur. With this block in place, all femoral cuts can be made. The A-P cuts are made using the top and bottom surfaces of the outer box.
The chamfer block is inset allowing visibility of the bone surfaces to be cut.
The hole for the central stem is prepared once the trial is in place by inserting the peg reamer through the central hole in the pegreamer guide which is po~itioned on ~h~ femoral trial, see Figure 53, ~d reaming to the appropriate depth which is determined by a-~arking, for example a stop 78', on the reamer.

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If a stabilizer femoral component is used, the bone must be excavated to prepare a site for the s~abilizer box. Choose the appropriate size stabilizer chisel (Figure 40). Rest the anterior skid 100 on the cut anterior ~emur and position the chisel midway between the femoral condyles~(Figure 54). With a mallet blow, impact the chisel to its full depth to remove the appropriate amount of bone.-Patella Pr~paration The patella resection guide is used to grip the patella and serves as a guide for the oscillating saw.
The jaws of ~he resection guide clamp the medial/lateral edges of the patella at the level of the proximal quadriceps and distal patellar tendon insertions. The top of the jaws~ar-~-broad and flat and will guide the oscilla~ing saw, making a flat cut.
The size of ~he patella surface is asse~sed using the patella template 90 ~hich includes 3 sizes in one.
Once the appropriate size is determined, holes to accept the three lugs ~re drilled into the patella surface by inserting the patella drill through the hoLes on t~e patella template, and dril~-ing to an appropriate dep~h.
At this point~ all bone surfaces have been prepared to accept the prosthetic components. Each prosth~sis is inserted wit~ its dedicated insertional tool.--The femoral inserter keys into the slots on theoutside edges of the femoral condyles. Varying femoral sizes are accomodated by a gearing mechanism within the inserter. A push pad is forced against the intercondylar region, and locks the prosthesis to the inserter. It can now be impacted onto the bone.
The tibial inserter keys and locks into under cuts provided on the tibial baseplate~, a sliding mechanism is used~to-accommodate varying prosthetic sizes. -. .: ~

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The patelLa forceps clamp (Figure 36) is used to press the patella button into position; and maintain this position while the bone cement is setting.
Implant Components An important feature of the implant system is its modularity and the fact that it has been designed for both cemented use and cementless press-fit applications utilizing the same pros~hetic components.
All bone contact surfaces of both the femoral components and tibial baseplates are generally broad and flat and contain no depressions, historically uset as a reservoir for excess bone cement. Rather, these bone contact surfaces are roughened by a blasting operation which is ideal, both for adhering to bone-cement and for bone ingrowth in the absence of cement.
On the femoral component, fixa~ion pegs have been removed rom the-condyles where they are most often found and ha~e been rep~aeed by one central stem. This allows for minimal dlsturbance of the distal condyles to enhance 20` loud transmissio~ --in a press-fit mode.
The tibial baseplates have a unique~ stem/fin configuration. The wings-extend outwardly and angle posteriorly. This positions the t-abs in the area of the strongest cancellous bone on the proximal tibial ~lateau, providing restraint against rotational forces. The wings sweep upward as they near the central stem allowing for a uniform, uninterrupted cement mantle in a cemented mode.
The patella prosthesis is suitable for cemented fixation only.
The modularity of the system is a result of ~
extensive interchangeability of the different components.
This modularity allows for precise fitting of individual patient anatomy and accomondates-varying degrees of ne~essary prosthetic stability. The tibial baseplates have~be~n desîgned with undercuts, ~hich allow both t ' ' . ' ~ ............................... .. .

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styles (PC/TC and stabilizer) of inserts to be assembled to them at the time of surgery.
Each insert is designed to accept three sizes of corresponding femoral components and are offered in varying thicknesses. The PC/TC inser~s can be used when the posterior cruciate ligament is either present or absen~.
The patella flanges of both the primarv and stabiLizer femoral componen~s are designed to accept any size patella prosthesis.
The pro~thetic system is also applicable when the patient has bone stock deficiencies. Metallic bone wedges for both the tibial basepla~e and femoral components are provided. They are directly attached to the implant components via bone cement to f-ill voids in the host bone cite.
The wedges have the same roughened texture as the tibial and femoral components, this surface is ideal for cement adhesion at both the wedge/prosthesis and wedge/bone interface.
The wedges are offered in sizes which correspond to the tibial and femoral component sizes.
The Posterior Cruciate Total Condylar Knee System consists of femoral, patellar and tibial components in varying sizes to accommodate diferences in patient anatomy.
Femoral Component:
This component made from cast Vitallium R alloy is symmetrical about the vertical a~is so as to be suited for replacement of the bearing surface of either the left or right femur and is designed with a neutral patellar groove. The internal surfaces of the component are flat, containing no depressions and are roughened (by grit blasting) to allow cement bonding. A central tapered '' . ~` ' ", ' `

~32~
stem is located at the base of the anterlor chamfer and extends vertically, perpendicular to the distal surface.
The articulating surfaces of the device - two femoral condyles and a patellar ~lange - are highly polished. The broad femoral condyles present a large medial-lateral radius to evenly distribu~e stresses to the tibial component. The patellar flange is deep and is designed to mate with the patellar prosthesis or the natural bone.
Each femoral component size is designed to mate with either its similar size tibial insert or one size larger or smaller.
Tibial Component:
The tibial prosthesis is a two piece design consisting of a cast Vitallium R tray and UHMW
Polyethylene inserts which are assembled to the tray at the time of surgery. The baseplates are offered in varying sizes to optimally fit the peripheral shape of the tibial plateau. The UHMW Polyethylene inserts mate with ~he corresponding size tibial baseplate and are offered in varying thicknesses to compensate for degrees of ligament laxity.
The tibial baseplate consists of a central stem (available in varying lengths) with supporting ribs which Z5 flare outwardly and posteriorly in the medial and lateral direction. The undersurface of the tray and stem are grit blasted, to provide a roughened surface for cement adhesion.
The articulating surface geometry of the tibial inserts are designed to provide anatomic rollback, flexion-extension and axial rotation. The anterior portion of the insert is raised superiorly to provide resistance to subluxation should the posterior cruciate ligament be resected. Provision is made to allow .
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~2~8 clearance for the posterior cruciate ligament should it remain intact.
The interlocking mechanism of the tibial component operates by means of a snap fit between the metal baseplate and the UHMW Polyethylene insert. The metal baseplate is designed with two undercuts at the pos~eriro margins on either side of the posterior cruciate ligament cutout. The anterior portion is equipped with a raised element which contains an undercut rim. The plastic insert has two elongated tabs which, when slid into position from anterior ~o posterior, engage the posterior undercuts on the metal baseplate. When fully engaged a downward force is applied to the anterior portion of the plastic insert which causes a relieved plastic tab to fle~ back and under th anterior undercut rim on the baseplate. tAn audible "Snap" may be heard as the components are fully engaged). ~his action mechanically secures the plastic insert within the confines of the metal baseplate.
Patellar Component:
The pa~ellar component is manufactured from UHMW
Polyethylene-and is ofered in varying sizes to fit the peripheral shape o ~he resected patella.
The bearing surface g-eometry is asymmetric about the proximal/distal axis to provide a lef~ or right orientation. This asymmetry allows for anatomic tracking against the highly polished surface of the femoral components's patellar flange.
The undersurface consists of three lugs and a central depression which pro~ides interlock for bone cement to securely fix the prosthesis to the resected patella. -The Stabiliver Total Knee System consists offemoral, tibial and patellar components in varying sizes to accommodate differences in patient anatomy.

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:- . : , ~ -22-~ 3 ~
Femoral Component:
This component made from cast Vitallium alloy is symmetrical about the vertical axis so as to be suited for replacement of the bearing surface of either the left or right femur and is designed with a neutral patellar groove. The internal surfaces of the component con~ain no depressions and are roughened (by grit blasting) to enhance cement bonding.
The articulating surfaces of the device - two femoral condyles, intercondylar cavity, and a patellar flange - are highly polished. The broad femoral condyles present a large medial - lateral radius to evenly distribute stresses to the tibial component. The patellar flange is deep and is designed to mate-with the patellar prosthesis or-the natural bone. The intercondylar cavity is designed to mate with-an element of the tibial insert described below.
Each component size is designed to mate with either -its similar size tibial insert or one size larger or smaller.
T_ ial Com~onent:
The tibial prosthesis is a two-piece design consisting of a cast Vitallium tray and UHMW Polyethylene inserts which are assembled to the tray at the time of surgery. Th-e baseplates are offered in varying sizes to optimally fit the peripheral shape of the tibial plateau.
The UHMW Polyethylene inserts mate with the coreesponding size tibial baseplate and are offered in varying thicknesses to accommodate differences in patient anatomy.
The tibial baseplate consists of a central stem (availa~le in varying lengths) ~ith supporting ribs which flare outwardly and posteriorly in the medial and lateral direction. The undersurace of the tray and stem are : .
~ ' -' ~32~48 grit blasted, to provide a roughened surface for cement adhesion, The articulating surface of the tibial insert contains medial and lateral depressions which are designed to ar~iculate with ~he condyles of the femoral component allowing anatomic flexion-extension and internal-external rotation. A postj ex~ending proximally, is positioned between the medial and lateral articulating surfaces. The anterior face is angled posteriorly to avoid infringement of the patella.
The posterior surface is angled anteriorly to present a sloping surface on which the curved portion of the femoral intercondylar ca~ity may articulate against.
When the knee fle~es in the absence of the posterior cruciate ligament this articulation produces postcrior rollback of the femur as in natural knee motion. -.

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Claims

1. A modular apparatus for use in the preparation of bone surfaces and the implantation of a modular total knee prosthesis in a patient, which apparatus comprises:
(a) an extendable rod having a distal end and a proximal end, means for adjusting the length of the rod, means for adjusting the lateral alignment and angular orientation of the proximal end of the rod, clamp means associated with the distal end of said rod for clamping said distal end to the ankle region of the patient's leg and combination fixing means and cutting platform associated with said proximal end of the rod for attaching said proximal end to the upper end of the patients tibia while aligning the cutting platform close to the tibial plateau;
(b) an adjustable stylus for aligning said cutting platform at the correct level for resecting the tibial plateau;
(c) a modular stem/fin template for determining the peripheral size of the resected proximal tibia and including a raised cylindrical hollow-tube for aligning a stem/fin punch;
(d) a stem/fin punch comprising a central hollow cylindrical tube with a distal chisel edge and two fins extending radially from said tube at a predetermined angle and each having a distal chisel edge;
(e) a push rod which fits into said hollow cylindrical tube of said stem/fin punch;
(f) an alignment fork attached to an intramedullary rod adapted to be introduced into a medullary canal of the patient;
(g) a femoral distractor comprising a handle, a rail adapted to slide onto the alignment fork, a lateral arm and a medial arm, each of which has associated means for separately raising and lowering each arm;
(h) a drill guide adapted to slide along the rail of the femoral distractor and having a plurality of holes for accepting locating pins;
(i) a distal cutting guide comprising a flat plate having a top surface and a bottom surface and integral flanges extending from said bottom surface and each being inset from one edge of said surface, each of said flanges having a locating hole extending therethrough;
(j) a modular cutting guide for guiding a saw blade to make cuts required for a femoral component prosthesis, comprising a substantially rectangular frame having a top wall and a bottom wall, each of said walls being defined by substantially parallel planar outer and inner surfaces, wherein each outer surface provides a flat cutting plane and the inner surfaces define an open window within which is located an intermediate solid block having an angled top surface and an angled bottom surface, each of said angled surfaces providing a guide for making a chamfer cut, said angled top surface being spaced apart from the top inner surface of said window and said angled bottom surface being spaced apart from the inner bottom surface of said window by gaps which provide a surgeon with a clear view of the surface being cut;
(k) a femoral sizer for determining the size of the patient's femur, comprising a body portion having locating holes, a central tubular orifice for accepting a feeler element and indicating means for indicating the depth of the feeler element within said orifice when the sizer is located on the patient's femur, thereby providing a determination of the size required for a modular cutting guide;

(l) a reamer guide for correct location of a reamer for preparing a cavity to locate a femoral prosthesis peg, which reamer guide comprises a flat plate having a top surface and a bottom surface, a hole extending through the plate, a tubular bushing extending from said top surface and lined up with said hole and locating pegs extending from said bottom surface;
(m) a patella resection guide comprising a scissor-type clamp having distal gripping arms, each of said arms defining a cutting surface and gripping teeth, said gripping teeth being inset below the plane of the associated cutting surface;
(n) a patella handling instrument providing alternative template and clamping functions comprising a scissor-type member having a first pivotal arm with a distal end and a second pivotal arm with a distal end; the first arm having a swivable platform located at its distal end, the surface of said platform facing inwardly toward said second arm and said second arm having means to interchangeably grip and hold either;- (i) a modular patella template having holes to accept drills, or (ii) a clamp member adapted to clamp a patella prosthesis to a resected patella.

2, An apparatus according to claim 1, wherein the clamp means associated with the distal end of extendable rod (a) comprises a pair of opposing tension spring-loaded jaws.

3. A femoral distractor of the type to be mounted on the end of a medullary alignment rod placed within the femoral medullary canal comprising:
a handle;
a body having an anterior surface thereof connected to said handle, said body having a key element formed thereon for slidably receiving an end of the medullary alignment rod to align the femoral distractor with respect to the femur;
a movable medial arm and lateral arm operatively connected to said body and extending posteriorly and generally parallel to a surface of said body which is generally perpendicular to the anterior surface thereof; and means mounted within said body for independently raising and lowering said medial and lateral arms.

4. The femoral distractor as set forth in claim 3 wherein said means mounted within said body for independently raising and lowering said medial and lateral arms is a rack and pinion mechanism operatively connected to each of said medial and lateral arms.

5. The femoral distractor as set forth in claim 4 wherein said pinion of each of said rack and pinion mechanisms is mounted on a drive shaft extending outwardly of said body with the shaft driving the medial arm extending from said body in the medial direction and the shaft driving said lateral arm extending in the lateral direction.

6. The femoral distractor as set forth in claim 5 wherein each shaft has an outer end including a turn key to enable manual rotation of said shaft.

7. The femoral distractor as set forth in claim 3 wherein said key element of said body is formed on a rail extending outwardly of said body intermediate said lateral and medial arms.

8. The femoral distractor as set forth in claim 7 wherein said rail further includes means for mounting a drill guide thereon.

9. The femoral distractor as set forth in claim 8 wherein said means for mounting said drill guide on said rail is a keyway formed outwardly of said key element from said body so that said drill guide may be mounted on said rail with the femoral distractor mounted on the end of the medullary alignment rod.

10. The femoral distractor as set forth in claim 3 wherein said handle is in the form of a pistol grip capable of being grasped with a single hand.

11. The femoral distractor as set forth in claim 10 wherein said handle has a hole therethrough to receive an alignment rod extending externally of the femur in a direction aligned with the medullary alignment rod.

12. A modular cutting guide for guiding a saw blade to make cuts required for a femoral component of a total knee prosthesis, comprising a substantially rectangular frame having a top wall and a bottom wall, each of said walls being defined by substantially parallel planar outer and inner surfaces wherein each outer surface provides a flat cutting plane and the inner surfaces define an open window within which is located an intermediate solid block having an angled top surface and an angled bottom surface, each of said angled surfaces providing a guide for making a chamfer cut, said angled bottom surface being spaced apart from the bottom inner surface of said block, defining said window, a first distance greater than the thickness of the saw blade, and said angled top surface being spaced apart from the top inner surface of said block, defining said window, a distance greater than said first distance to provide a surgeon with a clear view of the surfaces being cut.