United States Patent r191
`Kenna et al.
`
`[II] Patent Number:
`[45] Date of Patent:
`
`4,646,729
`Mar. 3, 1987
`
`[54] PROSTHETIC KNEE IMPLANTATION
`[75]
`Inventors: Robert V. Kenna, Saddle River, N.J.;
`David S. Hungerford, Cockeysville;
`Kenneth A. Krackow, Baltimore, both
`of Md.
`[73] Assignee: Howmedica, Inc., Wilmington, Del.
`[21) Appl. No.: 811,020
`[22) Filed:
`Dec. 19, 1985
`[51]
`Int. Cl.4 ................................................ A61F 5/04
`[52) U.S. Cl ......................... 128/92 VW; 128/92 VD;
`128/92 VL
`[58) Field of Search ............. 128/1 R, 303, 305, 92 E,
`128/92 EB, 92 C, 92 H
`References Cited
`U.S. PATENT DOCUMENTS
`4,211,228 9/1980 Cloutier .......................... 128/303 R
`
`[56)
`
`OTHER PUBLICATIONS
`David S. Hungerford, M. D., Kenneth A. Krackow, M.
`D., Robert V. Kenna, The Howmedica, "Universal
`Total Knee Instrument System", 1981.
`Nas. S. Eftekhar, M. D., "Total Knee-Replacement
`Arthroplasty", Journal of Bone and Joint Surgery, vol.
`65-A, No. 3, Mar. 1983, pp. 283-309.
`
`Primary Examiner-Stephen C. Pellegrino
`Attorney, Agent, or Firm-Harold Pezzner
`
`[57)
`ABSTRACT
`A prosthetic knee is implanted after cutting the femor
`and tibia in the proper manner with the aid of instru(cid:173)
`ments which include axial alignment guides and a series
`of cutting jigs.
`
`8 Claims, 101 Drawing Figures
`
`22
`
`-1-
`
`Smith & Nephew Ex. 1032
`IPR Petition - USP 7,534,263
`
`

`

`U.S. Patent Mar. 3, 1987
`U.S.Patent Mar. 3, 1987
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`ANTERIOR FEMUR
`
`r:=
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`POSTERIOR FEMUR
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`TRANSVERSE DISTAL FEMUR MEDIAL' LATERAL FEMORAL FlXArI
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`ANTERIOR CHAMFER
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`POSTERIOR CHAMFE.R
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`U.S. Patent Mar. 3, 1987
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`4,646,729
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`PROSTHETIC KNEE IMPLANTATION
`
`BACKGROUND OF THE INVENTION
`Prosthetic knee components have long been known
`and used in the art. In order to prepare the femor and
`tibia for 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(cid:173)
`/or score lines. Such techniques are necessarily impre(cid:173)
`cise which limits the ability to provide the anatomically
`most desirable prosthetic knee.
`Applicant's copending application, filed February
`1982, the details of which are incorporated herein by
`reference thereto, describes such an anatomically desir(cid:173)
`able prosthetic knee system.
`The aforenoted prosthesis is designed to reproduce 20
`anatomic movement of the knee without compromising
`stability. This prosthetic knee, as the natural knee, pro(cid:173)
`vides a "screw home" mechanism which increases sta(cid:173)
`bility in extension. As flexion proceeds, the femoral
`condyles initially roll posteriorly. Through asymmetric 25
`condylar and tibial compartments, the natural and
`changing axes of rotation are preserved, thereby pre(cid:173)
`venting the development of abnormal tension in re(cid:173)
`tained ligaments. When abnormal ligamentous tension
`develops, it either restricts flexion and increases shear 30
`stress at fixation interfaces and/or leads to eventual
`progressive ligament attenuation and joint instability.
`The design also allows natural internal and external
`rotation of the knee inflexion. Furthermore, contouring
`of the posterior margins of the tibial plateaus facilitates 35
`stability in flexion and provides a broad contact surface.
`The combination of these factors, which balance soft
`tissue elements in the joint, minimizes shear stress at the
`fixation interfaces, enhancing the potential for long
`term function of the replaced knee.
`In order to make such prosthetic knee system feasible,
`the necessary bone cuts must be precisely accom(cid:173)
`plished. This, in turn, requires a set of proper instru(cid:173)
`ments including guides and jigs. Such instruments
`should assure reproducibly accurate bone cuts, pros- 45
`thetic seating, and lower limb alignment.
`SUMMARY OF THE INVENTION
`An object of this invention is to provide techniques
`which permit the above-noted knee prosthesis to be 50
`implanted.
`A further object of this invention is to provide instru(cid:173)
`ments including guides and cutting jigs which assure the
`necessary accurate bone cuts.
`In accordance with this invention, a set of instru- 55
`ments 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 compo- 60
`nents of the prosthesis.
`
`2
`FIGS. 3-30 illustrate the various steps and instru(cid:173)
`ments used therein from incision to final tibial prepara(cid:173)
`tion in the practice of the invention;
`FIGS. 31-35 are side, top, front, bottom and rear
`views, respectively, of the distal femoral cutting jig
`shown in FIGS. 7-13;
`FIGS. 36-40 are side, front, rear, bottom and plan
`views, respectively, of the pin holder alignment guide
`shown in FIGS. 8-9;
`FIGS. 41-44 are cross-sectional views taken through
`FIG. 37 along the lines 41-41, 42-42, 43-43 and
`44-44·
`FIG'. 45 is a front elevation view partly in section of
`the distal femoral cutting jig shown in FIGS. 10-13;
`FIGS. 46-49 are top, bottom, side and rear views,
`respectively, of the femoral cutting jig shown in FIG.
`45·
`FIG. 50 is a cross-sectional view taken through FIG.
`48 along the line 50-50;
`FIGS. 51-55 are bottom, front, rear, side and top
`views, respectively, of the femoral drill jig shown in
`FIGS. 13-14;
`FIG. 56 is a cross-sectional view taken through FIG.
`52 along the line 56-56;
`FIGS. 57-61 are top, front, rear, bottom and side
`views, respectively, of the transverse femoral cutting jig
`shown in FIGS. 15-16;
`FIG. 62 is a cross-sectional view taken through FIG.
`57 along the line 62-62;
`FIGS. 63-67 are side, top, front, rear and bottom
`views, respectively, of the femoral spacer/tensor jig
`shown in FIGS. 17-22;
`FIG. 68 is a cross-sectional view taken through FIG.
`66 along the line 68-68;
`FIGS. 69-72 are top, rear, front and bottom elevation
`views, respectively, of the transverse tibial cutting jig
`shown in FIGS. 17-23;
`FIGS. 73-74 are end elevation views of the trans(cid:173)
`verse tibial cutting jig shown in FIGS. 29-72;
`FIG. 75 is a cross-sectional view taken through FIG.
`69 along the line 75-75;
`FIGS. 76-80 are bottom, front, rear, top and end
`views, respectively, of the femoral chamfer cutting jig
`shown in FIG. 24;
`FIG. 81 is a cross-sectional view taken through FIG.
`76 along the line 81-81;
`FIGS. 82-86 are bottom, front, rear, top and end
`views, respectively, of a modified form of femoral
`chamfer cutting jig;
`FIG. 87 is a cross-sectional view taken through FIG.
`82 along the line 87-87;
`FIGS. 88-92 are side, top, bottom, front and rear
`views, respectively, of the tibial positioning/fixation jig
`shown in FIGS. 25-30;
`FIG. 93 is a cross-sectional view taken through FIG.
`89 along the line 93-93; and
`FIG. 94 is a cross-sectional view taken through FIG.
`88 along the line 94-94.
`DETAILED DESCRIPTION
`The instruments utilized in the practice of the inven(cid:173)
`tion consist of long axial alignment guides and cutting
`THE DRAWINGS
`jigs. The jigs may be sequentially numbered relative to
`FIG. 1 illustrates the anatomical considerations of the
`their order of use to simplify the procedure. The align-
`legs which are taken into account in accordance with 65 ment guides are designed to assist the surgeon in posi-
`the invention;
`tioning all primary cutting jigs prior to making the bone
`FIGS. 2a through 2/ illustrate the eight basis bone
`cuts. All cutting jigs lock onto their respective bones to
`cuts which are made in accordance with the invention;
`insure the accuracy of the cuts.
`
`-25-
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`4,646,729
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`3
`The inventive instrument system is designed to seat
`the femoral and tibial components parallel to the ana(cid:173)
`tomic transverse axis of the knee. Since this axis is paral-
`lel to the ground and perpendicular to the vertical in
`two-legged stance, this positioning achieves: (I) uni- 5
`form stress distribution at fixation interfaces, (2) optimal
`alignment; and (3) physiological ligamentous balance of
`the knee. It is also important to recognize that the ankles
`remain closer to the midline vertical axis of the body
`that either the knees or hips throughout noral gait. To 10
`achieve the goals of total knee arthroplasty, these align(cid:173)
`ment features must be preserved or reconstituted.
`The inventive instrument system uses the femoral
`shaft axis (S), the center of the knee (K), the center of
`the ankle joint (A), and the transverse axis of the knee 15
`(T) as its alignment references (FIG. 1). The mechanical
`axis of the lower libm, which runs from the center of the
`hip (H) thorugh the center 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 wider apart than the 20
`ankles in both normal stance and gait (FIG. 1).
`Since the femoral head and neck overhang the shaft,
`the axis of the femoral shaft does not coincide with that
`of the leg, but forms with the leg a more acute valgus
`angle of 6° (SKH, FIG. 1). In total, the femoral shaft 25
`axis averages 9° of valgus with the vertical. The valgus
`angle of the femur varies relative to body build. The
`specific femoral valgus for a given individual can be
`determined by measuring angle HKS (FIG. 1) on a long
`X-ray which includes both the hip and the knee, and 30
`adding 3° (the mechanical axis). This method is valid for
`reconstituting a mechanical axis of 3 ° regardless of the
`degree of pre-operative axial deformity at the knee.
`For tibial alignment, the center of the knee and the
`center of the ankle are used as reference points. Instru- 35
`ments which rely on the proximal tibial shaft as their
`key alignment reference tend to be inaccurate due to the
`frequent occurrence of tibial bowing. Recognizing that
`the center of the ankle is closer to the midline vertical
`axis than the center of the knee in two-legged stance 40
`and throughout gait, this system uniquely requires a
`small angle at the proximal transverse tibal cut (TKA,
`FIG. 1). This angle keeps the transverse axis of the
`prosthesis parallel to the ground while the mechanical
`axis of the entire lower extremity remains in valgus 45
`(HKA, FIG. 1).
`FIG. 2 illustrates the eight basic bone cuts required to
`align and seat the femoral and tibial components of the
`prosthesis. As later described in detail, the instrument
`system consists of seven sequentially numbered cutting 50
`jigs and a femoral/tibial alignment guide. These are
`designed to insure the accuracy and alignment of all
`femoral and tibial bone cuts.
`In the practice of the invention, the knee is ap(cid:173)
`proached through a longitudinal skin incision, followed 55
`by a medical parapatellar capsular incision. The quadri(cid:173)
`ceps tendon is incised longitudinally, allowing eversion
`and dislocation of the patella laterally (FIG. 3).
`Orientation
`With the knee flexed to 90°, a 5/16 inch drill hole is
`made by drill bit 10 in the distal femur. It is placed
`roughly in the center 12 of the intercondylar notch just
`anterior to the femoral attachment of the posterior cru~
`ciate ligament (FIG. 4). The position of this hole 13 65
`(FIG. 6) is not critical to the orientation of any femoral
`bone cuts-it is simply a point of purchase for the distal
`femoral cutting jig IA. The laterally protruding handles
`
`4
`22 are used to rotate the jig so that the posterior
`rounded eminences parallel to the posterior femoral
`condyles and the anterior femur is seen as on a sunrise
`view (FIG. 5). Thejig is then hammered into place. Jig
`IA includes a pair of locking pins on the side hidden
`from view in FIG. 5. lfthere has been significant preop(cid:173)
`erative deformity, the short locking pin facing the most
`prominent condyle is hammered into place bringing the
`face of the jig IA flush to that condyle only.
`The Transverse Distal Femoral Cut: Varus-Valgus And
`Flexion-Extension Alignment
`The long axial alignment guide 16 is used to establish
`proper varus-valgus and flexion extension alignment of
`the distal femoral cuts. The guide pin 18 is positioned
`into the pin holder in the appropriate right or left 7°, 9°
`or 11° hole 20 (FIG. 37). This angle is chosen relative to
`the pre-operative X-ray measurement technique previ(cid:173)
`ously described in the alignment rationale section. Most
`often 9° will be appropriate. The guide 16 is then placed
`into the anterior holes of the distal femoral cutting 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 (FIGS. 7 and
`8). An examining finger can be slipped proximally under
`the quadriceps to get a better idea of the direction of the
`femoral shaft during this alignment procedure. If the
`alignment pin 18 does not parallel the .femoral shaft, a
`mallet is used to tap the medial handle 20 or lateral
`handle 22, advancing the jig IA away from the de(cid:173)
`formed condyle until the axial guide pin 18 parallels the
`femoral shaft (FIG. 9). With the alignment completed,
`one can easily visualize how much bone is missing 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 plac(cid:173)
`ing the IB jig.
`A short alignment pin is available to facilitate align(cid:173)
`ment in two special circumstances. The shorter pin
`avoids impingement with the tourniquet on an obese
`thigh or with the abdomen of a short patient.
`Locking The Distal Femoral Cutting Jig In Position
`The axial alignment guide 16 is removed and the
`tongue of the distal femoral cutting jig IA and jig IB is
`slid into the first part of the distal femoral jig IA (FIG.
`10). With the teeth of the IB jig resting lightly on the
`anterior femur, recheck the alignment for both varus(cid:173)
`valgus and flexion-extension prior to hammering it in
`place. When proper alignment is assured, first gently
`tap the IB jig with a mallet so that the teeth engage the
`bone without sliding down an oblique surface, thereby
`changing alignment. Then remove the alignment guide
`and hammer the IB jig firmly in place. There are also
`drill holes in the cutting bar of the IB jig through which
`k inch drill pins can be passed into the condyles if addi-
`tional stability is necessary.
`Final position of the distal femoral cutting jig IA is
`rechecked with the alignment guide. Measure twice, cut
`60 once (FIG. 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 attention
`to the cutting of the distal condyles. Pistol grip, endcut(cid:173)
`ting oscillating saws are most effective for these cuts. It
`is important that the surgeon pay strict attention to
`maintaining the saw blade flat against the proximal
`
`-26-
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`

`

`6
`Tibial Alignment And Cuts
`The femoral spacer/tensor jig IV and transverse tib(cid:173)
`ial cutting jig V are now assembled and positioned. The
`mortise cut out 34 in the transverse tibial cutting jig V
`is slipped over the tongue 36 of the femoral spacer /ten(cid:173)
`sor jig and slid as far proximally as it will go (FIG. 17).
`Following insertion of the jig's studs into the femoral
`fixation holes, the leg is brought into full extension. A
`folded towel or sheet is placed behind the knee to pre(cid:173)
`vent inadvertent hyperextension at this stage of the
`procedure. Next the axial alignment guide 16 with both
`its femoral and tibial alignment pins in place is posi(cid:173)
`tioned into the femoral spacer/tensor jig IV (FIG. 18).
`Axial And Rotational Alignment
`To achieve correct tibial axial 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 alignment will
`produce a slight tibial angle of 2.5° (A, FIG. 19). Ana(cid:173)
`tomically, the centers of the ankle joints are closer to(cid:173)
`gether than the centers of the knee joints. Overall leg
`alignment will still be in valgus. Correct extension
`alignment is achieved when the tibial shaft parallels the
`alignment pin when viewed from the side. Rotational
`alignment is correct when the medial malleolus is ap(cid:173)
`proximately 30° anterior to the lateral malleolus in the
`coronal plane (B, FIG. 19).
`If correct axial alignment cannot be achieved at this
`point with the jig IV in place, then one of the special
`techniques for dealing with the severe deformity will
`have to be employed. The jig V cannot be locked onto
`the tibia until correct alignment is achieved.
`Soft Tissue/Joint Tension/ Alignment
`Soft tissue stability is established following initial
`manual tibial axial alignment. Each side of the femoral
`spacer/tensor jig IV has expandable arms 38 which
`spread when its appropriate thumb screw 40 is tight-
`ened (FIG. 20). The tensor arms are extended to stabi(cid:173)
`lize the joint in the correct alignment. Do not over(cid:173)
`tighten the femoral spacer/tensor jig IV. The transverse
`45 tibial cutting jig V, pushed as far proximally as it will go
`ensures that only the minimal amount of the tibial pla(cid:173)
`teaus will be removed. When one plateau is considera(cid:173)
`bly more depressed than the other, the transverse cut-
`ting jig should be slid distally so that the plane of the
`tibial cut will rerove enough bone from the depressed
`plateau to provide a sufficiently flat surface for seating
`the tibial prosthesis.
`
`5
`cutting surface of the jig in order to achieve a precise
`cut (FIG. 13). Care should be taken to avoid the central
`intramedullary fixation peg of the jig. Following the
`initial transverse cut, the saw blade is passed back and
`forth across the cutting bar to shave the condylar cuts 5
`level with the plane of the cutting jig. This step is im(cid:173)
`portant since the saw blade tends to scive away from
`the desired plane, particularly in more sclerotic bone
`and toward the deeper portions of the cut. The jigs are
`now removed and the distal femoral cuts are completed. 10
`In completing these cuts, the anterior aspect of the
`distal femoral cut will serve as the "cutting block" for
`the remaining posterior aspect. It is, therefore, impor(cid:173)
`tant that the saw blade be inserted to the full depth of
`the initial cut before the oscillation is started. Other(cid:173)
`wise, one runs the risk of starting a new plane. Once the
`posterior part has been completed, the broadest blade
`should be passed over the surface to be sure that the cut
`is a single-flat plane. This can also be checked with a 20
`cutting block.
`Femoral Corponent Rotational, Medial-Lateral And
`Anterior-Posterior Alignment
`Rotational, medial-lateral and anterior-posterior ori- 25
`entation of the femoral prosthesis is determined by the
`femoral drill jig II. This jig has two posterior skids 24
`which are slid between the posterior femoral condyles
`and tibial plateaus. These skids automatically position
`the instrument in 0° of rotation relative to the coronal 30
`plane of the distal femur (A,A, FIG. 14). The jig should
`first.be centered in the medial-lateral position on the flat
`cut distal femoral surface, ignoring the initial keying
`hole for the IA jig. The jig II is now hammered flush
`with the flat surface of the distal femoral condyles. The 35
`jig's anterior projection contains two holes 26 marked
`respectively for right and left knees. When a i inch drill
`pin 28, placed in the appropriate hole, is aligned with
`the center of the patello-femoral groove, correct medi(cid:173)
`al-lateral and rotational positioning is assured (B,B, 40
`FIG. 14). When correct positioning has been assured, a
`5/16 inch drill 30 is used to make the holes for the femo-
`ral prosthesis fixation studs (C,C, FIG. 14).
`Anterior And Posterior Femoral Cuts
`Following the removal of the drill jig II, the two 5/16
`inch locking studs 32 of the anterior-posterior femoral
`cutting jig III, are inserted into the distal femoral fixa(cid:173)
`tion holes. The jig III is hammered flush with the flat
`cut surface of the distal femoral condyles. The anterior
`plane of the cutting jig should intersect the anterior
`cortex of the femur at the proximal margin of the patel-
`lar facets (FIG. 15). If this plane appears too deep or too
`anterior, the next most appropriate size jig should be 55
`chosen. If there is any question of which size jig is to be
`used, always start with the larger jig. The anterior and
`posterior femoral bone cuts are now completed (FIG.
`16). Once again, care must be taken to rest the saw blade
`flush against the flat surface of the jig. With the poste- 60
`rior condyles removed, complete access to the posterior
`compartment allows removal of the menisci and ante(cid:173)
`rior cruciate ligament. The tibial attachment of the
`posterior cruciate is identified and carefully avoided
`during the next step. Alsci, all remaining marginal osteo- 65
`phytes on the tibia and femur must be removed so they
`do not shorten or constrict ligaments or block full ex(cid:173)
`tension.
`
`50
`
`4,646,729
`
`15
`
`Check Of Overall Alignment
`Prior to locking the transverse tibial cutting jig V in
`place, overall lower limb alignment should be checked.
`For correct alignment, the femoral alignment pin 18
`will parallel the femoral shaft in both the anterior and
`lateral planes. The tibial alignment pin 19 will extend
`from the center of the knee to the center of the ankle
`and be parallel to the tibial shaft, in the lateral plane.
`Rotation is correct when the medial malleolus is ap(cid:173)
`proximately 30° anterior to the lateral malleolus (FIG.
`19).
`
`The Transverse Tibial Cut
`While still under visual control of the axial alignment
`guide pins 18, 19, the transverse tibial cutting jig V is
`
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`

`4,646,729
`
`7
`locked in place by drilling two b inch pins through the
`appropriate holes in the jig (FIG. 21). The alignrent
`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 5
`will pull out of its anchoring holes in the femur. The jig
`IV is then slipped proximally, disengaging it from the
`tibial cutting jig V (FIG. 22). The transverse tibial pla(cid:173)
`teau cut is then made by resting the saw blade flush
`against the broad flat surface of the cutting jig V (FIG. JO
`23). The cut is made as deeply as the saw blade will
`allow, while care is taken to protect collateral liga(cid:173)
`ments. Once again, following the initial cut of the oscil(cid:173)
`lating saw blade should be run back and forth across the
`flat surface of the transverse cutting jig to shave off any 15
`prominent bone that may be left posteriorly due to
`sciving of the saw blade in sclerotic bone. The jig V is
`then slipped off the Jocking pins and the cut is com(cid:173)
`pleted, making sure that the posterior rims of the pla(cid:173)
`teaus are level with the plane of the transverse cut. 20
`Additional care should be taken to preserve the poste(cid:173)
`rior cruciate ligament. Since the transverse tibial cut is
`made parallel to the ground for optimal stress distribu(cid:173)
`tion as the prosthesis bone interface and because the
`normal tibial plateau slopes 7° to 10° posteriorly, more 25
`bone will be removed anteriorly than posteriorly.
`Femoral Chamfer Cuts
`The femoral chamfer cutting jig VI is inserted then
`into the femoral fixation holes. With the saw blade flush 30
`against the jig's cutting planes 42, the anterior and pos(cid:173)
`terior cuts are made (FIG. 24). As with other cutting
`jigs, it is important to maintain the saw blade perfectly
`flush with the cutting surfaces 42 of the jig to assure
`precise cuts, otherwise the femoral component will not 35
`fully seat.
`Tibial Component Rotational, Medial-Lateral And
`Anterior-Posterior Alignment
`The knee is extended and traction is applied from the 40
`· - 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 (FIG. 25). The
`two posterior tabs 44 of the jig position behind the
`posterior rims of the tibial plateau, assuring correct 45
`posterior position of the tibial prosthesis. The knee is
`then flexed and the jig VII is centrally positioned. Since
`the posterior margins of the tibial plateaus are nearly
`parallel to the transverse axis of the tibia, the posterior
`tabs 44 will position the jig in correct rotation. Rota- 50
`tional and medial-lateral positioning are checked by
`slipping an axial alignment guide pin 19 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 55
`place. If alignment is correct, the distal tip of the align(cid:173)
`ment pin should center over the ankle joint with the
`medial malleolus 30° anterior to the lateral malleolus
`(FIG. 26). If this is not the case, the jig is manipulated
`into proper alignment. Rotational malalignment tends 60
`to be toward external rotation of the tibia.
`An appropriate size tibial trial prosthesis 48 is inserted
`onto the jig (FIG. 27). The trial femoral prosthesis is
`then positioned onto the femur.
`Initial Trial Reduction
`Range of motion and stability are now tested. If the
`· joint is too Jax, the next thickest tibial trial is slipped
`
`8
`onto the tibial positioning/fixation jig VII. Once flex(cid:173)
`ion, rotation and stability are satisfactory, the overall
`alignment is checked in full extension (FIGS. 28 and
`29). The alignment guide is removed, and the knee is
`flexed to 90°. Next, the femoral trial and tibial spacer
`are removed. The thickness marked on the tibial trial
`spacer indicates the thickness of the prosthesis to be
`implanted.
`
`Final Tibial Preparation
`When the stemmed tibial prosthesis is being used, the
`window 50 in the jig VII is used, as a cutting guide. A
`! inch osteotome 52 is used to prepare the fixation slot
`while thejig is still locked onto the proximal tibia (FIG.
`30).
`For the aforenoted prosthesis resurfacing tibial pros(cid:173)
`thesis which uses medial and lateral fixation studs, a
`5/16 inch drill 54 is used to make the stud holes through
`the drill guides in the jig VII (FIG. 30). With fixation
`peg or stud holes completed, the jig is removed. A final
`check of the joint is made for posterior loose bodies, and
`soft tissue debridement is completed.
`Instruments
`FIGS. 31-94 illustrate in full scale various instru(cid:173)
`ments used in accordance with this invention.
`FIGS. 31-35 illustrate the distal femoral cutting jig
`IA which is used for achieving axial alignment when
`used with the axial adjustment guide 16. Distal femoral
`cuts are made when jig IA is used with cut jig IB. As
`indicated therein, the upper surface of the central por-
`tion 56 of jig IA has attached thereto a pair of lateral
`handles 22, 22 while a medial handle 20 also extends
`from the front face of central section 56. A positioning
`pin 58 is disposed on the rear face of central section 56
`as previously described. Attaching means are provided
`on the upper surface of the central section 56 for selec(cid:173)
`tive attachment of the pin holder alignment guide 16.
`The attaching means is in the form of a pair of holes 60,
`62 which are of different diameter corresponding to the
`different diameter Jocking pins 64, 66 (FIG. 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 56 also includes a
`pair of short alignment pins 68 as previously described.
`A vertical cut-out 70 extends completely through
`central section 56 for receiving the tongue 72 (FIG. 45)
`of the distal femur cutting jig IB. An adjustable locking
`screw 74 is movable into cut-out 70 to lock tongue 72 in
`place.
`FIGS. 36-44 illustrate the details of pin holder 16
`which is used with guide pins 18, 19 (FIG. 19) to assure
`correct axial alignment throughout the surgical proce(cid:173)
`dure. Pin holder 16 is in the form of an elongated bar
`and includes bifurcated pins 64, 66 to complement the
`holes 60, 62 in jig IA. The lower portion of pin holder
`16 is provided with a pair of mirror image tibial holes
`76, 76 for selectively receiving tibial alignment pin 19.
`The holes are angled oppositely each other, as previ(cid:173)
`ously 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 for the femo(cid:173)
`ral alignment pin 18. The holes are disposed at the most
`likely angle required such as 7°, 9° and 11 •with one set
`65 being for the right knee and the other for the left knee.
`FIGS. 45-50 illustrate the details of distal femoral
`cutting jig IB which is in the form of a plate or bar
`having a downwardly extending tongue 72 with non-
`
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`

`

`25
`
`9
`symmetric cross-section of complementary size and
`shape to fit within the mortise cut-out 70 of jig IA. Jig
`IB is used for cutting the distal femoral condyles. Plate
`84 includes a pair of femoral securing pins 86 for attach(cid:173)
`ment to the femur with two pairs of positioning pins 88 5
`spaced inwardly th