CA1195201A - Prosthetic knee implantation - Google Patents

Abstract

PROSTHETIC KNEE IMPLANTATION
Abstract Of Disclosure A prosthetic knee is implanted after cutting the femor and tibia in the proper manner with the aid of instruments which include axial alignment guides and a series of cutting jigs.

Description

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Background oE Invention Pros-thetic knee components have long been known and used in the art. In order to prepare the femor and tibia Eor the components, it is necessary to make a series of cuts from these bones to conform -to the size and shape of the prosthetic components. Generally these cuts are made by visual reliance on where the cuts should be sometimes with the aid of simplified jigs and/or score lines. Such techniques are necessarily imprecise which limits the ability to provide the ana-tomically most desirable prosthetic knee.
Applicant's copending Canadian application No. ~21,731, filed February 16, 1983, describes such an anatomically desir-able prosthetic knee system.
The aEorenoted prosthesis is designed to reproduce anatomic movement of -the knee without compromising stabili-ty.
This prosthetic knee, as the natural knee, provides a "screw home" rnechanism which increases stability in extension. As flexion proceeds, the femoral condyles initially roll posterior-]y. Through asymmetric condylar and tibial compartments, the natural and changing axes of rotation are preserved, thereby preventlng the developmen-t of abnormal tension in retained liyaments. When abnorrnal liyamentous tension develops, it either restric-ts Elexion and increases shear stress at fixa-tion interEaces and/or leads to eventual proyressive liyament a-ttenu-ation and joint instability. The design also allows na-tural internal and external rotation of the knee in flexion. Further-more, contouriny of the posterior margins of the tibial plateaus facili-tates stabi:Lity in flexion and provides a broad con-tact surface. The cornbination oE these Eac-tors, which balance soft tissue elements in the joint, minimi~es shear stress at the

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fixation interfaces, enhancing the po-tential for long term function of the replaced knee.
In order to make such prosthetic knee systern feasible, the necessary bone cuts must be precisely accomplished. This, in turn, requires a set of proper instruments including guides and jigs. Such instruments should assure reproducibly accurate bone cu-ts, prosthetic seating, and lower limb alignment.
Summary of Invention An objec-t of this invention is to provide techniques which permit the above-noted knee prosthesis to be implanted.
A further object of this invention is to provide instruments including guides and cutting jigs which assure the necessary accurate bone cuts.
A set of instruments is provided which allows for variations in the anatomical axis of the femor. The instruments include cutting jigs which are selectively locked directly to the bone. By use of these instruments, eight basis cone cuts are made to align and seat the femoral and tibial components oE
the prosthesis.
In particular, in accordance witn the present inven-tion, there is provided a distal femoral cut-ting jig for the implantation of a prosthetic knee comprising a cen-tral section, lateral handle means extending laterally outward of said central section from at least one side thereof, a medial handle means extending outwardly from the front face of said central section, a positioning pin ex-tending outwardly from the rear face of said central section, attaching means on -the upper surface of said central section for selective at-tachment of a pin holder alignment guide thereto, and securing means on said upper surface of said central section for selective at-tachmen-t of a dis-tal femoral condyles cutting jiy.

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119~ZVl ll The Drawin~s Il .
Figure l illustrates the anatomical considerations of the legs which ar~ taken into account in accordani~e with the in-¦ vention;
I Figures 2a throug~ 2f illustrate the eîght basis bone ¦ cuts which are made in accordance with the invention;
Figures 3-30 illustrate the ~arious steps and instru-ments used therein from inir.ision ti~ final ti~ial preparatio~ in the practlce of the inve~tion;
. Figures 31-35 are side, top, front, bottom and rea~ -views, respectively, of the distal femoral cuttin~ shown in . Figures 7-13;
Figures 36-40 are side, ront, rea.r, bottom and plan views, respectively, of the pin holder alignment ~uide shown in , Figures 8-9;
Figures 41-44 are cross-sectional views taken through ~, Figure 37 along the lines 41-41, 42-42, 43-43 and 44-44;
Figure 45 is a front elevation view partly in sec~on j, of the distal femoral cutting jig shown in Figures 10-13;
Figures 46-49 are top, bottom" side and rear views, Il respectively, o~ the femoral cutting jig shown in Figure 45;
" Figure 50 is a cross-sectional view taken through Figure 48 along the line 50-50;
Figures 51-55 are bottom, front, rear, side and top views, respectively, of the femoral drill jig shown ln Figures~
13-14;
Flgure 56 ls a cross-sectional view taken through ¦¦ Figùre 57 along the line 56 56;
Figures 57-61 are top, front, rear, bottom and side views, respectively, of the transverse femoral cu.t~ing jig shown in Figures 15-~6;

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9~2 !l li Figure 62 is a cross-sectional view taken through ! Figure 57 along the line 62-62;

i Figure 63-67 are side, top, front, rear and bottom views, respectively, of the ~emoral spacer/tensor jig sh~wn in Figures 17-22;
Figure 68 is a cross-sectional vie~ taken through Figure 66 along the line 68-68;
Figures 69-72 are toP, rear, front and bottom eleva-1 tion views, respectively, of the trans~erse t~ial cutting 3ig ,1i shown in Figures 17-23;~
Figures 73-74 are end elevation view~ of th~ tra~s-, verse tibial cutting jig shown in Figures 29-72;
Figure 7S is a cross-~ectional view taken ~hrough Figure 69 along the line 75-75;
Figures 76-80 are bottom, frant, rearJ top and end views, respectively, of the ~moral chamfer cutting jig ~hown 'l in Figure 24;
Il Figure 81 is a cross-sectional view taken through ,; Figure 76 along the line 81-81;
,I Figures 82-86 are bottom, front, rear, toP and end ,I views~ respectively, of a modified ~orm o femoral chamfer Il cutting jig;
,1 j~ Figure 87 is a cross~sectional view taken through ¦i Figure 82 along the line 87-87;
Figures 88-92 are side, top, bottom, front and rear views, respectively, of the ti~ial positioning/fixation jig shown in Figures 25-30;
Figure 93 i9 a cross-sectional view taken through Figure 89 along the line 93-93; and Figure 94 is a cross-sectional view taken through Figure 88 along the line 94-94.

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Detailed Description The lnstruments utilized in the practice of the inven- ;
Il tion consist of long axial alignment guides and cutting jigs.
¦¦ The jigs may be sequentially numbered relative to their order of .
¦l use to simplify ~he procedure. The alignment guides are designed Il to assist the suxgeon in positioning all primary cutting jigs ¦¦ prior to making the bone cuts. All cuttLn~ jigs lock onto their I
respecti~e bones to insure the accuracy o. the cut~. !
The inventlve instrument system is designed to 3eat I the femoral and tibial components parallel to the anatomic tra~s~
,I verse axis of the knee. Since this axis is parallel to ~he . ground and perpendicular to the vertical in two-legged s~ance, " this posit-Loning achleves~ uniform stre~s distribution at fixation interfaces, (2) optimal alignment 9 and (3) physio-logical ligamentous balance of the knee. It is als~ im~ortant . to recognize that the ankles remain closer to the ~idline ver-~, tical axi~ of the body that either the knees or hips throughout ,, noral gait. To achieve the goals o total knee arthroplasty, Il these allgnment features must be preserved or reconstituted.
The inventive instrument syst:em uses the femoral shaft .
Il axis (S), the center of the knee (K), the center of the ankle Il joint (A), and the transverse axis of the knee (T) as its align-¦l ment references (Fig~e 1). The mechanical axis of the lower ¦l libm, which runs from the center of the hip (H) thorugh.the cen- , ter of the knee (K) to the center of the ankle (A), generally forms an angle of 3 with the vertical (V), because the hips are ;
¦I wlder apart than the ankles in both normal stance and gait (FLgure 1).

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Il Since the femoral head and neck overhang the shaft, i! ~he axls of the femoral shaft does not coincide with that of the leg, but form~ with the leg a more acute valgus angle of &
(SKH, Figure 1). In total, the femoral shaft axis averages 9 of valgus with the vertical. The valgus angle of the femur ~aries relative to body build. Ihe specific femoral valgus for a given individual can be determlned by measu~ing angle HKS
(Figure 1~ on a long x-ray which includes both the hip and the knee, and adding 3 (~he mechanical axis). This method is ' valid for reconstituting a mechanical axis of 3~ regardless of 1~ the degree of pre-operative axial deformity at the knee.
ii For tibial alignment, the center of the knee and the center of the ankle are used as reference points. Instruments which rely on the proximal tibial shaft as their key alignment re~erence tend to be inaccurate due to the frequent occurrence of tibial bowing. Recognizing that the center of the ankle is Il closer to the midline vertical axis t~an the center o the knee ¦¦ in two-legged stance and throughout gait, this system uniquely ,~ requires a small angle at the proximal transverse tibal cut Il (TKA, Figure 1). This angle keeps the transverse axis of the prosthesis parallel to the ground while the mechanical axis o~
the entire lower extremity remains in valgus (HKA, Figure 1).
j Figure 2 illustrates the eight basic bone cu~s required ¦ to align and seat the femoral and tibial com~onents of the prosthesis. As later described in detail, the instrument sys- I
tem consists of seven sequentially numbered cutting jigs and a femoral/tibial alignment guide. These are designed to insure ~¦ the accuracy and alignment o~ all femoral and tibial bone cuts.

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" In the practice of the invention, the knee is approa~hed ¦l through a longitudinal skin incision, followed by a medical para-, patellar ca~sular incision. The quadriceps tendon is incised ~¦i longitudinally, allowing eversion and dislocation of the pa~e'Lla ¦¦ laterally ~Figure 3).
Orientation ~ ith the knee flexed to 90, a 5/16 ineh drill hole is made by drill bit 10 in the distal femur. It is plared ' ' roughly in the center 12 of the intercondylar notch just anterior i to the femoral attachment of the po~terior rruciate ligæment ,' (Figure 4). The position of this hole 13 (Figure 6) i5 t critical to ~e I orientatlon of any femoral bone cuts -- -it is simply a point of purchase for the distal ~emoral cutting jig IA. The laterally " protruding handles 22 are used to rotate the ilg so that the posterior rounded eminences parallel to the posterior femoral condyles and the anterior femur is seen as on a sunrise ~iew 1 ~Figure 5). The jig is then hammered into place. Ji~ IA in-I cludes a pair of locking pi,ns,on the side hidden from view in Figure 5. If there has been signi~icant ~reoperative deformity, the short locking pin acing the most prominent condyle is ham-! mered into place bringing the face of the jig IA flu~h to thatcondyle only, I'he Transverse Distal Femoral Cut: Varus-Valgus And Flexion-Extension Alignment The long axial alignment guide 16 is used to establish I
proper varus-valgus and flexion extension alignment of the distal!
femoral cuts. The ~uide pin 18 is positioned into the pin holderl in the appropriate right or left 7, 9 or 11 hole 20 ~Figure 37)..
. This angle is chosen relative to the ~re-operative x-ray measure-3S2~

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m~n~ technique previously described in the ali~nment rationale section. Most oten 9 will be appropriate. The guide 16 is then placed into the anterior holes oE the distal femoral cut~ing jig IA. Correct axial alignment is achieved when the long alignment guide pin 18 is parallel to the femoral shaft axis in both the anterior and lateral views (Figures 7 and 8). A~
examining finger can be slipped proximally under the quadriceps to get a better idea o ~he direc~ion of thQ femor~l shaft j during th~s alignment procedure. If the alignment pin 18 does not parallel the femoral shaft~ a mallet is used to ta~ the 'i medial handle 20 or lateral handle 22, advanci~g the ji~ IA
away from the deformed condyle until the axial guide pin 18 parallels the femoral shaft (Figure 9). With the alignment ', I completed, one can easily visualize how much bone is mlssin~, from the deformed condyle. The IA jig is not stable at this point but must be manually held during insertion and removal of the alignment pinholder and also while placing the IB jig.
A short alignment pin is available to facilitate alignment in two special circum~tances. The shorter pin av~ds impingement with the tourniquet on an obese thigh or with th~
abdomen of a short patient.
' Locking The Distal Femoral Cutting Jig In Position jl The axial alignment guide 16 is removed and the ¦¦ tongue of the dis~al femoral cuttin~ IA and ~jig IB is s~id into the first ~art of the distal femoral ji~ IA (Figure 1~
, With the teeth of the IB jig resting lightly on the anterior ¦ emur, recheck the alignment for both varus-valgus and flexi~n- i extension prior to hammerin~ it in place. When proper ali~n-.
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ment is assured, first gently tap the IB jig with a mallet so that the teeth engage the bone without slidin~ down an oblique surface, therebY changing alignment. Then remove the alignment guide and hammer the IB jig fir~ly in place. There are also drill holes in the cutting bar of the IB ji~ through which 1/8 inch drill pins can be passed into the condYles if addi-tional stability is necessarY.
Final position of the distal fPmoral cutting jig IA
is rechecked with the alignment ~uide. Measure ~wice, cut onc~
(Figure 12).
Cutting The Distal_Femur Once the distal femoral cutting jig IA is locked on to the femur, the surgeon is free to direct his full atten-tion to the cutting of the distal condyles. Pistol grip, end-cutting oscillating saws are most effective for these cuts. It i9 importan~ that the surgeon pay strict attention to maintain-ing the saw blade flat again~t the proximal cutting surace of the jig in order to achieve a precise cut (Figure 13). Care should be taken to avoid the central intramedullary fixation peg o the jig. Following the initial transverse cut, the saw blade is passed back and forth across tlhe cutting bar to shave the condylar cuts level with the plane o~ the cutting ji~. ~his step is important since the saw blade tends to scive away from t.he desired plane, particul~rly in more sclerotic bonP and toward the deeper portions of the cut. The jigs are now re-moved and the distal femoral cuts are completed. In completing these cu~s, the anterior aspect of the distal femoral cut will serve as the "cutting block" for the remaining pasterior aspect.
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It is, therefore, important that the saw blade be inserted to l~ the full depth of the initial cut beforP the oscillation is Il started. Otherwise, one runs the risk of startin~ a new plane.
'11 Once the posterior part has been conpleted, the broadest blade l,¦ should be passed over the surface to be sure that the eut is a ¦¦ single-flat plane. This can ~lso be checked with a cutting I! block.
Femoral ComDonent Rotational, Medial-Lateral And Anterior-Posteric,r Ali~nment Rotational, medial-lateral and ante~ior posterior orientation of the femoral prosthesis i9 determined by the jl femoral drill jig II. ~his jig has two pasterior skids 24 Il which are slid between the posterior femoral condyles a~d tibial :
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1, rlateaus. These skids automatically position the instr~men~ in - li 0 of rotation relative to the coronal plane of the distal femur (A,A~ Figure 14). m e ji~ should first be centered in !
the medial-lateral position on the flat cut distal femoral sur-face, ignoring the lnitial keying hole or ~he IA jig. The Il jig II is now hammered flush with the flat surface of the dis-j' tal femoral condyles. The ~ig's anterior projectlon containstwo holes 26 marked respectively for right and left knees.
Il When a l/8 inch drill pin 28, placed in the appropriate hole, ¦¦ is aligned with the center of the patello-femoral groove, cor-rect medial-lateral and rotational positioning is assured ¦ (B,B, Figure 14). When correct positioning has been assured, a 5/16 inch drill 30 is used to make the holes or the femoral prosthesis fixation studs (C,C, Figure 14).
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Anterior And Posterior Femoral Cuts _ .
Following the removal of the drill jig II, the two 5/16 inch lockin~ studs 32 of the anterior-posterior femoral cutting jig III, are inserted into the distal fem~ral fixation holes. The jig III is hammered flush with the flat cut surface of the distal femoral condyles. The anterior plane o the c~t-t~ng jig should intersect the anterior cortex o the femur a~
the proximal margin of the patellar facets (Fi~ure 15). If this Plane appears too deep or too anterior, the next m~st apora-priate size jig should be chosen. If there is any qtlestion of which si~e jig ls to be used, always start with the larger ji~. ¦
The anterior and posterior femoral bone cuts are now completed ' (Figure 16). Once again, care mNst be taken to rest the saw blade flush against the flat surface of the jig. ~ith the posterior condyles removed, complete access to the po~terior compartment allows removal of the menisci and anterior cruciate ligament. The tibial attachment of the posterior crueiate is identifie~ and careully avoided during the next step. Also, all remainin~ marginal osteophytes on the tibia and femur must be removed so they do not shorten or constrict ligaments or block full extension.
Tibial Ali~nment And Cuts The femoral spacer/tensor jig IV and transverse tibial cutting jig V are now assembled and positloned. The mortise cut out 34 in the transverse tibial cutting jig V is sllp~,ed over the tongue 36 of the femoral spa~er/tensor jig and slid as far proximally as it will go (Figure 17). Following inser-tion of the ~,ig's studs into the femoral fixation hoLes, the !1. , 11 . . I
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leg i5 brought lnto full extension. A folded towel or shee~
is placed behind the knee to prevent inadvertent hyperexten-sion at this stage of the procedure. Next th~ axial ali~nment uide 16 with both its femoral and tibial alignment Pins in place is positioned into the femoral s~acer/tensor ji~ IV
(Figure 18~.
Axial And ~9539C9~ U~D9~
To achieve correc~ tibial axlal alignment prior to making the transverse tibial cut, longitudinal traction and manipulation are applied from the foot. The goal is to bring the center of the ankle joint directly under the distal dip of the alignment pin. This align~en~ will produce a slight ~ibial angle of 2.5 (A, Figure 19). Anatomically, the c~nters of the ankle joints are closer together than the centers of the knee joints. Overall leg aligNment wil~ still be in valgus.
Correct extension alignment is achieved when the tibial shat parallels the alignment pin when viewed from the side. Rota tional alignment ls correct when the medial malleolus is ap- i proximately 30 anterior to the lateral malleolus in the coronal plane (B, Fi~ure 19).
If correct axial alignment cannot be achieved at this point with the jig IV in place, then one of the special techniques for deallng with the severe de~ormity will have to be employed. The jig V cannot be locked onto the tibia antil ccrrect all~n~ent is achieved.

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¦ Soft Tissue/Joint TensiontAlignment Soft tissue stability is established following initial manual tibial axial alignment. Each side of the femoral spacer tensor jig IV has expandable arms 38 wh~ch spread-when its`ap-propriate thumb screw 40 is tightened (Figure 20). The t~nsor arms ar~ extended to stabilize the joint in the correct ali~n~
ment. Do not overtighten the femoral spacerltensor jig ~V. The I¦ transverse tibialcutting jig V, pushed a~far proximally as it will Il go ensures that only the minimal amount of the tibial pLateaus will be re ved. When one plateau is considera~ly more depressed, ~i than the other, the transverse cutting jig should be ~lid dis-tally so that the plane o~ ~he tlbial cue will remove enough bonei !I from the depressed~plateau to provide a sufflciently flat ur- !
'~ face for seating the tibial prosthesis.
Check Of Overall Alignment ~~ Prîor to locking the transverse tibial cutting jig Y
I in place, overall lower limb alignment should be checked. For ¦ correct alignment, thé femoral alignment pin 18 will ~arallel ~ the femoral shaft in both the anterior and lateral planes. The ¦~ ti.bial alignment pin 19 will extend from the center of the knee ¦I to the center o~ the ankle and be parallel to the tibi~l shaft, ¦l in the lateral plane. Rotation is correct when the medial malleolus i8 appro~imately 3n o anterior to the lateral malleolus , ~¦ (Figure 19~.
The Transverse Tibial Cut _ While still under visual control of the axial ali~n-ment guide pins 18, 19, the transverse tibial cutting jig V is locked in place by drilling two 1/8 inch pins through ~he appro-.

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priate holes in the jig (Figure 21). The alignment guide 16 is now removed and tension is removed from the jig IV by loosening the thumb screws 40. As the knee is flexed to 90, the femoral spacer/tensor jig IV will pull out of its anchor-ing holes in the femur. The jig IV is then slipped pro~imally, disengaging it from the tibial cutting jig V (Fi~ure 22). The transverse tiblal plateau cut is then made by restln~ the saw blade flush against the broad flat surface of the cutting jig V (Figure 23). The cut is made as deeply as the saw bl~de will allow, while care i~ taken to protect collateral ligaments.
Once again, ollowing the initial cut of the oscillating saw 1 blade should be run back and forth across the flat surface o~
the transverse cutting jig to shave off a~y prominen~ bone that may be left posteriorly due to scivin~ of the saw blade in sclerotic bone. The jig V is then slipped off the locking pins and the cut is comPleted, mak~hg sure that the ~osterior rims of the plateaus are level with the plane o~ the trans~erse cut. Additional care should he taken to preserve the posterior cruciate ligament. Since the ~ransverse tibial cut is made parallel to the ground ~or optimal stress distribution as the prosthesis bone inter~ace and because the normal tibial plateau slopes 7 to 10 posteriorly, more bone will be removed anterior-ly than posteriorly.
Femoral Chamfer Cuts The femoral chamfer cutting jig VI is inserted then into the femoral fixation holes. With the saw blade flush against the jig's cutting planes 42, the anterior and posterior cuts are made (Figure 24). As with other cutting jigs, it is l . Il Il important to maintain the saw blade perfectly flush with the ¦, cutting surfaces 42 of the jig to assure ~recise cuts, other-wise the femDral component will not fully seat.
, ~ Tlbial Component Rotational, Medial-Lateral ~nd Anterior-Posterior Alignment The knee is extended and traction is ~pplied rom the foot to open the joint space. The posterior tabs of the appropriate sized tibial positioning/fixation jigs VII are hooked behind the cut proximal tibia (Figure 25). The two posterior tabs 44 of the jig position behind the posterior rlms of the tibial plateau, assurlng correct po~terio~ position of the tibial prosthesis. The knee is then fle~ed and the jig VII is centrally positioned. Since the ~osterior margi~s of il, the tibial plateaus are nearl~ parallel to the transverse axis of the tibia, the posterior tabs 44 will position the jig in correct rotation. Rotational and medial-later~l positioning are , checked by slipping an axlal alignment guide pin l9 through !; the appropriate right or left alignment hole in the anterior "
' flange of the jig. The two anterior thumb screws 46 of the jig are then lightly tightened, securing the jig in place.
I alignment is correct, the distal tip of the alignment pin ! should center over the ankle joint with the medial malleolus ¦1 30 ankerior ~o the lateral malleolus (Flgure 26). If this i is no~ the case, the jig is manipulated into proper alignment~
Rotational malalignment tends to be toward external ro~a~ion of the tibia.
¦ An appropriate size tibial trial prosthesis 48 is inserted on~o the jig (Flgure Z7~. The trial fe~oral prosthesis is then posi~ioned onto the femur.

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Initial Trial Reduct_on Range of motion and stability are now tested. If the joint is too lax, the next thickest tibial trial is slipped onto the tibial positioning/fixation jig VII. ~nce flexion, rotatlon and stability are satisfactory, the overall alig~ment is checked in full extension (Figures 28 and 29). Tha ali~n-ment guide is removed, and the knee is flexed to gno. Ne~t, the femoral trial and tibial spacer are removed. The t~ickness marked on the tibial trial spacer indicates the thickness of ¦ the prosthesis to be implanted.
,I Final Tibial Preparation Il ' When thej,stemm~d ~ibial prosthesis is being used, ii the window 50 in the jig VII is used, as a cuttin~ guide. A
ii 1/2 inch os~eotome 52 is used to prepare the fixation slot i, !I while the jig is still locked onto the proximal tibia (Figure 30).
For the aforenoted prosthe~is resurfacing tibial l~ prosthesis which uses medial and lateral ixation studs, a 5/16 inch drill 54 is used to make the stud holes through the ,I drill guides in the jig VI,I (Figure 30). With fixation peg ¦l or stud holes completed, the ji~ is removed. A flnal check jl of the joint is made for posterior loose bodies, and soft tissue debridement is completed.
Instruments Figures 31-94 illustrate in full scale various in- ' struments used in accordance with this invention. , I
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Figures 31-35 illustrate the distal femoral cutting 1, jig IA which is used for achieving axial alignment when used ¦i with the axial adjustment guide 16. Distal femoral cuts are made when jig IA is used with cut jig IB. As indlcatsd therein, the upper surface of the central portion 56 of jig IA has at ,l tached thereto a pair of lateral handles 22, 22 while a medial ¦ handle 20 also ex~ends from the front face of central section , 56. A positioning pin 58 is disposed on the rear face of cen- !
i' tral section 56 as ~reviously dese~ibed. A~taching means are provided on the upper surface of the central s~ction 56 for selective attachment of the pin holder alignment guide 16. The attaching means is in the form of a pa~r of holes 6~, 62 which ! are of diferent diameter corresponding to the different diame~er locking pins 64, 66 (Figure 37)`of the pin holder 16. In this manner there is assurance that the pin holder can be mounted in only the correct position.
The rear surface of central section ~6 also includes a pair of short alignment pins 68 as previously described.
', A vertical cut-out 70 extend~ completely through central section 56 for receiving the tongue 72 ~Figure 45) of the distal femur cutting jig IB. An adjustable loc~in~ screw ,' 7b~ is movable into cut-out 70 to lock tongue 72 in place.
il Figures 36-44 illustrate the details of pin holder ¦¦ 16 which is used with guide pins 18, l9 (Fi~ure 19) to assure ¦¦ correc~ axial alignment throughout the surgical procedure.
1' Pin holder 16 is in the form of an elongated bar and includes ,ll bifurcated pins 64, 66 to complement the holes 60, 62 in jig IA. The lower portion of pin holder 16 is provided with a palr 9S~
Il , o mirror image tibial holes 76, 76 for selectlvely receiving tibial alignment pin 19. The holes are angled oppositely each other, as previously described, with one holder being for the right knee and the other being for the left knee. Similarly, three sets of holes 78, 80, 82 are provided ~or the femoral alignment pin 18. The holes are disposed at the most l~kely angle required such as 7, 9~ and 11 with one set be~ng for the right knee and the other for the left knee.
Figures 45-50 illustrate the details of distal femoral cu~ting jig IB which is in the form of a plate cr bar having a downwardly extending tongue 72 with non-sym-metric cross-section of complementary size and shape ~o fit within the mortise cut-out 70 o jig IA. Jig IB is used for cutting the distal femoral condyles. Plate 84 includes a pair of femoral securing pins 86 for attachment to the emur with two pairs of posi~ioning pins 88 spaced inwardly thereof. The upper surf~cè of plate 84 is also provided with a pair of non-identical holes 90, 92 for receiving the locking pins 64, 66 of pin holder 16. Plate 84 is also provided with a generally vertical guide surface 94 on each wing portion thereof to act as a saw cutting guide (see Figure 13). A pair of vertical holes 96 are provid~d in plate 84.
Figures 51-56 illustrate the femoral cutting jig II
which is used to determine the rotational, medial-lateral and anterior-posterior orientation of the femoral component and allows drilling of holes for prosthesis fixation stud.
As shown therein, jig lI is in the form of a generally ver-tical pllte 98 havin~ 8 flat inner surface 100. A pair of ` 11 ~ l .

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pos~erior skids 24 extend outwardly from inner surface 100 at the lower portion thereof. A pair of drill holes 2S extend through plate 98 as previously described. If the po~terior condyles are intact, a hole may be drilled there;n throuph the aid of one of the drill holes 102, 102 with holes 102, lQ2 being inclined for the right and left knee. Plate ~8 also ' includes a pair of positioning ~ins 1~4 on its inner surface 1()1~. ' Figures 57-62 illustrate the anterior-poster~or cutting jig III. As indicated therein, jig III is in the form of a bar or plate 106 which has a flat vertical surface 108.
A pair of distal femoral fixation pins 3~ extend rom surace 108. A generally horizont~l lower cutting guide surface 110 is also provided as well as an upwardly inc~ined cutting guide surface 112. A cut-out 114 is located centrally of bar 106.
Preferably jig III would come in small, medium and large sizes.
Figures 63-68 illustrate the detalls of femoral spacer/tensor jig IV which assembles and positions transverse tibial cutting jig V to determine correct sot tissue balance and tibial axial and rotational alignment prior to making the transverse tibial cut. Jig IV comprises a pair o~ spaced fixed legs 116 with each leg having a lower vertical section and an inwardly inclined upper section. A ~ransverse bridge member 118 joins the fixed legs at the junction of the upper and lower sections. A pair of spaced parallel movable legs 38 generally conform in size and shape to fixed legs 116 and are hingedly mounted at their ends thereof by hinge connection 102 to their respective movable legs. Adjusting means in the form of bolts or th~b screws 40 are threadably engaged with and extend through fixed legs 116 into contact with movable legs 38 for ` `
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licontrolling the spacing or relativa positioning of the respec-¦ltive se~s of legs. A pair of studs 126 are provided at the ¦llower portion of legs 116 while rounded contact surfaces 128 ¦extend away from movable legs 38. Legs 38 may thus be moved so that surfaces 128 contact the tibia. Bridge member 118 in-cludes outwardly extending tongue 36 which is of non-symmetrical cross section for complementary engagement with mortise cut-out l'34 in jig V (Figure 17). Jig V could then slide in or out on litongue 36 to adjust for the length o cut.
Figures 69-75 illustrate transverse tibiaL cutting jig V which is in the form of a bar 130 having a flat upper cutting guide surface 132 and cut-out 34 for receiving tongue 36 of jig IV. A locking screw 134 is movable into cut-out 34 to lock tongue 36 in place. A pair of vertical drill hoLes !~ 136 also extend through bar 130.
Figures 76-81 show one form of femoral chamfer cutting jig VI which is in the orm of a bar ~38 having its front ace formed in three sections which include a pair of jinclined upper and lower cutting guide surfaces 42 extend-, ing to the up~er edge and lower edge o bar 138. The inter-mediate surface 140 is generally vertica]L. A pair of posi-tioning studs 142 are provided to extend into the same medial Ij alignment holes which are utilized by various other jigs.
Il ~e(~1 6 ~ r C
¦I Figures 82-87 show a modified form of jig VI~
wherein a condylar cut out 144 is pro~ided in the lower guide surface. Preferably jig VI would come in five different sizes varying in slze of the cut-out 144 andlor bein~ sized small, medium or large.
Figures 88-94 illustrate the tibial positioning/
ixation jig VII. Jig VII generally includes a plate 146 having a lower planar surface 148 from which extend a pair w~_ ~ ~

Il . , jlparallel tabs 44. An osteotome cut-out or window 50 is provided ¦¦in the central portion thereof with an inclined drill hole 150 on lleach side of cut~out 50. A block 152 is connected to plate 146.
; ¦A pair of vertical alignment holes 154 which are inclined for the . Irigh~ and left knee extend through block 152. Additionally thumb .
¦screws 46 are threadedly mounted into and extend through block 152 while a pair of non-identical holes 156, 158 are provided in block 152 for receiving the locking pins 64, 66 of holder 16.
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Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A distal femoral cutting jig for the implantation of a prosthetic knee comprising a central section, lateral handle means extending laterally outward of said central section from at least one side thereof, a medial handle means extending out-wardly from the front face of said central section, a position-ing pin extending outwardly from the rear face of said central section, attaching means on the upper surface of said central section for selective attachment of a pin holder alignment guide thereto, and securing means on said upper surface of said cen-tral section for selective attachment of a distal femoral condyles cutting jig.

2. The jig of claim 1, in combination therewith, a pin holder alignment guide, said pin holder alignment guide includ-ing an elongated bar, complementary attaching means at the lower portion of said bar attaching said bar to said distal femoral cutting jig, a set of mirror image tibial holes extend-ing through said bar at an angle to the central vertical plane of said bar for selective reception of a tibial alignment pin, and at least one set of mirror image femoral holes extending through said bar for selective reception of a femoral alignment pin.

3 The jig of claim 2 including three sets of said femoral holes at angles of 7° and 9° and 11°, respectively.

4. The jig of claim 3, in combination therewith, a distal femoral condyles cutting jig, said distal femoral con-dyles cutting jig comprising a bar, a downwardly extending tongue from said bar mounted to said securing means of distal femoral cutting jig, femoral securing pins extending downwardly from said bar remote from said tongue, a generally vertical cutting guide surface on said bar between said tongue and said securing pins, and pin holder guide attaching means on said bar.