P.F.C. SIGMA KNEE SYSTEM
REVISIONSURGICAL TECHNIQUEP. F. C. S I G M A K N E E S Y S T E MREVISION SURGERYFOR FAILED TOTAL-KNEEREPLACEMENT
CONSULTING SURGEONSTHOMAS S. THORNHILL, MDDOUGLAS A. DENNIS, MDJohn B. and Buckminster Brown Professor ofOrthopedic SurgeryHarvard Medical SchoolClinical Professor, Department of Engineering,Colorado School of MinesOrthopedist-in-ChiefBrigham and Woman’s HospitalBoston, Mass.RICHARD D. SCOTT, MDProfessor of Orthopaedic Surgery, HarvardMedical SchoolOrthopaedic Surgeon, Brigham and Womensand New England Baptist HospitalsBoston, Mass.Clinical Director, Rocky Mountain Musculoskeletal Research LaboratoryCo-Director, Rose Institute for JointReplacementDenver, Colo.
CONTENTSIntroduction1Surgical Technique2Initial Preparation of the TibiaPreparation of the Femur814Distal Resection19Anterior/Posterior Resection21Notch and Chamfer Resection25Final Preparation of the Tibia32Preparation of the Patella36Assembling the Prosthesis38Appendix I: The Cemented Tibial and Femoral Stem Extensions46Appendix II: The IM Device for Tibial Augmentation Resection49Appendix III: The External Tibial Alignment System51Appendix IV: Femoral Revision and Tibial Insert Compatibility55Appendix V: Offset Tibial Tray Preparation for Fluted Stems56
P.F.C. SIGMA REVISION KNEE SURGERY*INTRODUCTIONPREOPERATIVE PLANNINGIn total-knee arthroplasty, failure may resultfrom many causes, including wear, asepticloosening, infection, osteolysis, ligamentousinstability, arthrofibrosis and patellofemoralcomplications. In approaching revisionprocedures, the surgeon must address suchconsiderations as the planning of an incisionin a previously operated site, the condition ofthe soft tissue, mobilization of the extensormechanism, extraction of the primary prosthesis and the attendant conservation of bonestock. Amongst the goals of successful revisionarthroplasty are the restoration of anatomicalaligrument and functional stability fixation ofthe revision implants and accurate re-establishment of the joint line. Careful selection of theappropriate prosthesis is of paramount importance. Ideally, the revision knee-replacementsystem will offer the options of adjunctive stemfixation and variable stem positions, femoraland tibial augmentation and various levels ofprosthetic constraint.Revision total-knee arthroplasty begins withthorough clinical and roentgenographic evaluation. Physical evaluation includes the examination of the soft tissues, taking into accountprevious skin incisions, range of motion, motorstrength, the condition of all neurovascularstructures, ligamentous stability and theintegrity of the extensor mechanism.Biplanar radiographic views are obtained, asare tangential views of the patella and fulllength standing bilateral extremity views forthe assessment of alignment and bone stock,documentation of the joint line and evaluationof the present implant fixation. Stress views arehelpful in evaluating ligamentous instability.CAT and MRI scans may at times be of value incases of massive bone loss or substantialanatomic distortion from trauma and metabolicbone disorders. Templates are employed toestablish replacement implant size and thealignment of bone cuts, to indicate augmentation of skeletal deficits and to confirm theanatomic joint line.*The P.F.C. Sigma Revision Knee System is intended for cemented use only.1
SURGICAL TECHNIQUEINITIAL INCISIONWhere possible, the scar from the primary procedure is followed. Where parallel incisions arepresent, the more lateral is usually preferred, asthe blood supply to the extensor surface ismedially dominant. Where a transverse patellectomy scar is present, the incision shouldtransect it at 90 . Where there are multiple incision scars or substantial cutaneous damage(burn cases, skin grafting, etc.), one may wishto consult a plastic surgeon prior to surgery, todesign the incision, determine the efficacy ofpreoperative soft-tissue expansion, and plan forappropriate soft-tissue coverage at closure.2
CAPSULAR INCISIONThe fascial incision extends from the proximalmargin of the rectus femoris to the distal margin of the tibial tubercle following the medialborder of the patella, maintaining a 1 8” cuff forreapproximation of the vastus medialis aponeurosis at closure. Where mobilization of theextensor mechanism and patella is problematic,the skin and capsular incisions are extendedproximally.Occasionally, an early lateral retinacular releaseis indicated to assist patellar eversion. Whereeversion difficulties persist, a quadriceps snip,a proximal inverted quadriceps incision (modified V-Y) or a tibial-tubercle osteotomy may beindicated. Appropriate ligamentous release isperformed based upon preoperative and intraoperative evaluation. Fibrous adhesions arereleased to re-establish the suprapatellar pouchand medial and lateral gutters.In many revision cases, the posterior cruciateligament will be absent or nonfunctional; anyresidual portion is excised.3
THE P.F.C. SIGMA REVISIONKNEE SYSTEM IS COMPRISED OF THEFOLLOWING COMPONENTS: Stabilized Femoral Component available inseven sizes TC3 Femoral Component available in sixsizes Ability to up/downsize femur to tibia 4 mm, 8 mm, 12 mm and 16 mm DistalFemoral Augmentations 4 mm and 8 mm Posterior FemoralAugmentations Three anteroposterior Femoral StemPositions: 0, 2 mm and -2 mm 125 mm and 175 mm Fluted Femoral StemLengths in 10 mm to 24 mm diameters in 2mm increments at 5 and 7 valgus angles4 90 mm and 130 mm Cemented Femoral StemLengths in 13 mm and 15 mm diameters at 5 and 7 valgus angles Three levels of tibial insert constraint: Posterior Stabilized, Stabilized Plus and TC3 Three types of Tibial Wedge AugmentationComponents: Hemi Wedge in 10 and 20 angles; Step Wedge in 10 mm and 15 mmthickness; and Full Wedge in 10 and 15 angles 75 mm, 115 mm and 150 mm Fluted TibialStem Lengths in 10 mm to 24 mm diametersin 2 mm increments 30 mm and 60 mm Cemented Tibial StemLengths in 13 mm and 15 mm diameters Systematic and simple instrumentationsystem to accommodate each of the component options and surgical preferences basedupon a patented Rod and Sleeve IM alignment system
EXTRACTION OF IMPLANTS FROM THEPRIMARY PROCEDURECare is taken to preserve as much bone as possible. To this end, a selection of tools is assembled, including thin osteotomes, an oscillatingsaw, a Gigli saw, a high-speed burr and variousextraction devices, but may cases will requireonly the osteotome.The bone/cement or bone/prosthesis interfaceis carefully disrupted before extraction isattempted. The implanted components are disengaged and extracted as gently as possible, insuch manner as to avoid fracture and unnecessary sacrifice of bone stock. Where the entireprosthesis is to be replaced, it is advantageousto remove the femoral component first, as thiswill enhance access to the tibia. All residualmethylmethacrylate is cleared with chisels orpower tools.5
INTRAOPERATIVE EVALUATIONRECOMMENDED SURGICALPRIORITY1. Tibial medullary canal preparation2. Proximal tibial resection3. Femoral medullary canal preparation4. Distal femoral resection5. Establishment of femoral rotation6. Anteroposterior, notch and chamfer resection7. Establishment of tibial rotation8. Tibial deficit augmentation9. Final tibial preparation10. Patellar preparation11. Implantation of the componentsThe surgeon should establish two anatomicconditions to facilitate revision arthroplasty:the level of the joint line and the disparity inthe flexion and extension gaps.JOINT LINE EVALUATIONIn an average knee in full extension, the truejoint line can be approximated in reference toseveral landmarks. It lies 12–16 mm distal to the femoral PCLattachment. It lies approximately 3 cm distal to the medialepicondyle and 2.5 cm distal to the lateralepicondyle. It lies distal to the inferior pole of the patella(approx. one finger width). Level with the old meniscal scar, if available Additional preoperative joint line assessmenttools include:1. Review of original preoperativeroentgenogram of the TKA2. Review of roentgenogram of contralateralknee if non-implanted6
JOINT SPACE ASSESSMENTJoint space is evaluated with spacer blocks todetermine the flexion/extension gap relationshipand the symmetry of both the flexion andextension gaps, and to indicate if prosthetic augmentation is needed to ensure postoperativeequivalence. A 1 mm shim should be used forthe extension gap and removed when assessingthe flexion gap. This will compensate for the1 mm component difference between the distaland posterior condyles.The tibia is sized first, and the same size offemoral component is initially chosen. This canthen be adjusted to accommodate the following:WHERE FLEXION GAP EXTENSION GAP:To decrease flexion gap without affecting extension gap, a larger femoral component is applied.This is particularly importantwhere an IM stem extensionis indicated, asthe stem extension willdetermine the anteroposterior positioning of the component and the consequentflexion gap.Where there is insufficient stability, a cementedfemoral stem may be substituted, allowing thecomponent to be seated further posteriorly.Where the joint line is elevated, the preferred correction is posterior femoral augmentation. Thealternative—additional distal femoral resectionand use of a thicker tibial insert to tighten the flexion gap—is not recommended, as considerablebone stock has been sacrificed in the primary procedure, and it is important that additional resectionof the distal femur be avoided. The possible exception is where the joint line is not elevated andminimal distal resection will increase the extensiongap toward equivalency with the flexion gap.Where significant flexion laxity persists, despitethese maneuvers, consider the use of the TC3component.WHERE EXTENSION GAP FLEXION GAP:To decrease extension gap without affecting flexion gap, the distal femur is augmented with bonegraft or prosthetic augmentation. It is importantto note that this will lower the joint line, whichis usually desirable as it is generally found to beelevated in revision cases. This willlessen the incidence of postoperative patellar infera.Where stem positioningwill not permit posterioraugmentation, a 2 mmoffset stem bolt withthe arrow pointinganteriorly is assembled to the component,translating the femoralcomponent2 mm posteriorly.(Refer to page 29 forfurther explanation.)7
INITIAL PREPARATION OF THE TIBIATHE INTRAMEDULLARY ROD & SLEEVETIBIAL ALIGNMENT SYSTEMWhen at preoperative evaluation, roentgenographic evaluation demonstrates the conditionof the proximal tibia to be such that augmentation and/or a fluted stem extension is indicated, it is recommended that the medullarycanal be appropriately prepared and that resection be predicated with reference to the fixedposition of the IM rod within thecanal and accordingly to the subsequent position of the fluted stemextension. Where a cemented tibial stemextension is indicated, see Appendix I.The knee is placed in maximal flexion with thepatella laterally everted and the tibia distractedanteriorly and stabilized. Fibrosis about the tibial border is released or excised as required toensure complete visualization of its periphery.The location of the medullary canal is approximated with reference to preoperative A/P andlateral roentgenograms, and to the medial thirdof the tibial tubercle.A 5 16” drill is introduced into the canal toa depth of 2–4 cm, withcareful attention thatcortical contact beavoided.8
REAMING THE MEDULLARY CANALThe reamer handle is assembled onto a small diameter Specialist 2 reamer. The shaft containsmarkings for lengths of both tibial and femoralstems. See illustration for tibial markings. Flutedtibial stem lengths are available in 75 mm,115 mm and 150 mm. A small-diameter reameris initially used. The canal is sequentially openedwith progressively larger reamers until firmendosteal engagement is established.The length and diameter of the prosthetic stemextension is initially determined with templatesapplied to preoperative roentgenograms. Theline governing the length of the prosthesis isindicated as shown on the shaft of the reamerand is positioned at the most proximal point ofthe proximal tibia.It is important that simple cortical contact not beconstrued as engagement as it is the fixed relationship of the reamer to the cortices that ensuresthe secure fit of the appropriate sleeve and, subsequently, the corresponding fluted stem. It isequally important that osteopenic bone not beoverreamed.The size of the final reamer indicates the size ofboth the sleeve and the implant stem. As thefluted tibial rods and Specialist 2 revision sleevesare available in even sizes (12 through 24 mm),final reaming is accordingly performed with aneven-sized reamer.9
POSITIONING THE ROD AND SLEEVEThe intramedullary rods are provided in threelengths to accommodate various sizes of tibia.The appropriate rod is selected, insertedthrough the sleeve corresponding to the size ofthe final reamer and advanced to the distal end.The handle is subsequently assembled to therod. The sleeve is rotated 180 clockwise on therod and retracted toward the handle untillocked in position. The rod and sleeve assemblyare subsequently introduced into the preparedmedullary canal and carefully advanced. Thesleeve will fit snugly within the reamed canal,but excessive force is not required. Advancement proceeds until the predetermined depthas indicated on the rod is aligned with theproximal surface of the tibia established by theprimary procedure. As the depth markingson the IM rod correspond to those of theT-handled reamer, insertion of the sleeve willnot exceed the depth reamed.For Tibial Fluted Stem Lengths10A75 mmC115 mmE150 mm
With the sleeve thus engaged, the rod is gentlyretracted approximately 15 mm and rotated 180 clockwise by the handle to disengage it from thesleeve and enable it to advance beyond thesleeve until its tip is engaged at the diaphysealisthmus, thereby enhancing stability. Again,excessive force is avoided. The handle is subsequently removed, and the rod remains in place.The IM rod should extend out of the proximaltibia by approximately 12 cm to accommodatethe tibial IM device.THE IM TIBIALALIGNMENT DEVICEThe IM tibial device witha 3 posterior slanted cutting block attached isplaced over the IM rod.11
POSITIONING THE ALIGNMENT DEVICEAND PROVISIONAL ROTATIONALALIGNMENTThe cutting guide is positioned on the IM rodand allowed to descend to the proximal tibialsurface. As considerable bone stock may havebeen sacrificed in the primary TKR, the amountresected is held to a minimum: no more than isneeded to provide a level surface on the lessdeficient side.Resection is basedupon tibial deficiency and the levelof the joint line,with deficienciescompensated withwedges and/orbone grafts. TheStylus Cylinderassembly is lockedCutting Block set atin position withthe 2 mm levelthe lateralsetscrew. The cutting block is advancedto the anterior tibial cortex and lockedinto position by tightening the knurledknob on the outrigger. Provisional rotational alignment is based on the medial third ofthe tibial tubercle. The alignment device issecured to the IM rod with the lateral setscrew.The cylinder foot of the stylus is inserted into theslot of the cutting block and adjusted to theappropriate level. The block is lowered to thislevel by depressing the level on the right side.If tibial augmentation is required, bone defectpreparation is delayed until after initial trialreduction is performed and exact rotational position of the tibial component confirmed.Tibial rotational alignment is confirmed at trial reduction to ensure congruity with the femoral componentthroughout the complete range of motion.12
TIBIAL RESECTIONSteinmann pins are introduced bilaterallythrough the holes designated 0 (boxed).The IM alignment device is unlockedfrom the cutting block, and with the IMrod and sleeve is removed from thetibia. Resection is made through theslots with an oscillating saw and a 1.19mm (.047”) blade.Where full-surface wedge augmentation isindicated, see Appendix II (page 49).13
PREPARATION OF THE FEMURINTRAMEDULLARY ROD & SLEEVEFEMORAL ALIGNMENT SYSTEMRATIONALEThis technique was designed to predicate allfemoral cut and govern the placement of thefemoral component with reference to the fixedposition of a P.F.C. Sigma fluted IM rod. Thelength and diameter of the prosthetic stemextension is determined with templates appliedto preoperative roentgenograms. The procedurebegins with the preparation of the medullarycanal.The midline of the femoral trochlea is identified3 mm anterior to the anterolateral margin of theattachment of the posterior cruciate ligament.The medullary canal is entered with a 5 16” drillto a depth of 3–5 cm. Care is taken that the drillavoid the cortices. It is helpful to palpate thedistal femoral shaft as the drill is advanced.Where impedance of the intramedullaryrod is anticipated, the entry point isadjusted accordingly.14
REAMING THE MEDULLARY CANALThe reamer handle is assembled onto a smalldiameter reamer. The shaft contains markingsfor lengths of both tibial and femoral stems. Seeillustration for femoral markings. The flutedfemoral stem lengths available are 125 mm and175 mm and are available for the Posterior Stabilized and the TC3 femoral components. Themedullary canal is sequentially opened withreamers of progressively greater size until firmendosteal engagement is established.It is important that simple cortical contact ofthe tip not be construed as engagement asit is the fixed relationship of the reamerto the cortices that ensures the securefit of the appropriate sleeve and,subsequently, the correspondingfluted stem.The line governing the lengthof the prosthesis is indicated asshown on the shaft of thereamer and is positioned at themost distal point of the femur.Where a P.F.C. Sigma cemented stem extensionis indicated, the final reaming is made with a17 mm reamer to accommodate the 15 mmdiameter stem extension, or a 15 mm reamerfor the 13 mm stem extension.As P.F.C. Sigma fluted femoral rods and Specialist 2 revision sleeves are available in even sizes(12 through 24 mm), final reaming is accordingly performed with an even-sized reamer.15
POSITIONING THE ROD AND SLEEVEThe intramedullary rods are provided in threelengths to accommodate various sizes of femurs.The appropriate rod is selected, insertedthrough the sleeve corresponding in size to thefinal reamer, and advanced to the further end.The handle is subsequently assembled to therod. The sleeve is rotated 180º clockwise on theIM rod and retracted toward the handle untillocked in position. The rod and sleeve assemblyare subsequently introduced into the preparedmedulllay canal and carefully advanced.The Femoral StemB for the 125 mm Stabilized fluted femoral stemB for the 125 mm TC3 fluted stemE for the 175 mm Stabilized fluted stemF for the 175 mm TC3 fluted stemThe sleeve will fit snuglywithin the reamed canal, butexcessive force is not required.Advancement proceeds until the predetermined depth as indicated on the rod isaligned with the distal surface of the femurestablished by the primary procedure. As thedepth markings on the rod correspond to thoseof the T-handled reamer, insertion of the sleevewill not exceed the depth reamed.16
With the sleeve thus engaged, the rod isretracted gently by the handle approximately15 mm and rotated 180 clockwise to disengageit from the sleeve and enable it to advancebeyond the sleeve until its tip is engaged at thediaphyseal isthmus, thereby enhancing stability.Again, excessive force is avoided. The handleis subsequently disassembled from the rod.The IM rod should extend out of the distalfemur by approximately 12 cm to accommodatethe femoral instruments.17
THE FEMORAL LOCATING DEVICEThe appropriate valgus angle is determinedthrough the application of templates to thepreoperative roentgenogram. The appropriatevalgus angle, 5 or 7 , and Right/Left kneeindication is set and locked into place on thefront of the locating device. The locating deviceis placed over the IM rod and advanced tocontact the distal femur. The calibrated outrigger will be centered at the trochlea and mustbe in its full raised position relative to the prepared anterior surface.18
DISTAL RESECTIONThe distal femoral cutting block is assembledonto the calibrated outrigger by depressing thebutton located on the right proximal end. Thecutting block is advanced to the 0 mm designation which is to the right of the number. Thelevel of distal resection is determined by intraoperative confirmation of the preoperative estimation of the joint line and evaluation of distalcondylar deficiency. The cutting block hasslots to allow for a 0 mm, 4 mm or 8 mmresection level.The outrigger and cutting block assembly islowered onto the anterior cortex by depressing the button on the left-hand side of thelocating device. Either 1 8” drill bits or Steinmann pins are introduced through the holesdesignated zero and enclosed in ’s. The cutting block and outrigger are subsequentlyremoved from the locating device. The locatingdevice is removed from the IM rod, and thedistal femoral cutting block is removedfrom the outrigger and placed backover the Steinmann pins. The rodand sleeve remain in place.19
In many cases little, if any, bone is removedfrom the distal femur as the joint line is effectively elevated with the removal of the primaryfemoral component. As the level of resection ispredicated on the preservation of bone stock,each condyle is cut only to the level requiredto establish a viable surface, with augmentationemployed to correctimbalance.An example of lateralresection at 0 mmAn Resectionexample ofMedialat 8medialmm resectionat 8 mmResection is accordingly performed through theslot appropriate for each condyle, using a standard 1.19 mm blade.20
ANTERIOR/POSTERIOR RESECTIONThe appropriate 5 or 7 , 0 mm, or 2 mm offsetbushing, which corrects for the normal stemposition at the selected femoral valgus angleand interior bone loss, is assembled to theRevision A/P cutting block.Where indicated, the appropriate distal spacer(4, 8, 12 or 16 mm) is assembled to the proximalside of the cutting block to compensate for thecondylar discrepancy as determined duringspacer block assessment. The block, in turn, isassembled onto the IM rod through the appropriate Right/Left opening and seated flush tothe prepared distal surface.ROTATIONAL ALIGNMENTOF THE A/P AND CHAMFERCUTTING DEVICESThe appropriate trial fluted stem isassembled to the trial tibial tray andpositioned within the preparedmedullary canal.21
Rotational positioning of the revision A/P cutting block is critical to the establishment of a symmetrical flexiongap and patellofemoral alignment. Rotation is such that theposterior surface of the cuttingblock is parallel to the resurfaced proximal tibiaunder tension. Symmetry is validated withspacer blocks or laminar spreaders. Whereasymmetry exists, additional soft-tissue balancing may be indicated. Positioning is furtherconfirmed by assuring parallel alignment of thecutting block with the transepicondylar axis.With rotation confirmed, the cuttingblock is secured with Steinmannpins introduced through the holesdesignated .22
The foot plate of the stylus is introduced intothe anterior slot and the height is set at 0 mm.The arm of the stylus in contact with the anterior femur should read “Slotted”.The stylus is passed over the anterior cortex toensure against femoral notching. Whereobstruction is identified, two options are available and are predicated by the flexion gap.If the flexion gap is loose relative to the extension gap, the next larger size femoral component can be used and the posterior condylesaugmented. If the flexion gap is tootight relative to the extension gap, the0 mm bushing is replaced in the A/Pcutting block with the 2/-2 mm bushing in the -2 mm position. This will translatethe femoral component 2 mm anteriorly. Whereminimal anterior separation is identified, it maybe compensated with cement at implantation.Where the cutting block is correct but the stylusindicates no anterior bone will be removed, it isrecommended that the 2/-2 mm bushing besubstituted for the 0 mm and placed in the 2mm position as long as no flexion space tightness exists. This positions the A/P cutting block2 mm posteriorly, thereby ensuring maximalanterior contact.This decreases the flexion gap by 2 mm.23
The stylus assembly is removed. Where unilateral distal augmentation is planned, the appropriate spacer remains positioned between theblock and the deficient condyle. Where bilateraldistal augmentation is planned, the rigidity ofthe system is such that only the larger of theindicated spacers need be used. In either case,further fixation is gained by affixing Steinmannpins through the anterior holes. Anterior resection is performed through the anterior slotusing a 1.19 mm blade.Anterior CutAn Example of Posterolateral Cut at 4 mmPosterior resection is through the slot designated 0 or, where there is posterior condylardeficiency, the appropriate 4 or 8 mm slot isused to accommodate the projectedaugmentation.24
NOTCH AND CHAMFER RESECTIONWhere distal augmentation is planned, theappropriate trial spacer is inserted into itsreceptacle on the notch cutting guide. The trialspacer selected should be the same as was usedon the A/P cutting block.The appropriate notch/chamfer bushing isselected. This corresponds to the bushing thatwas used on the A/P cutting block, 0 mm, 2mm or -2 mm. It is assembled onto thenotch/chamfer cutting guide with the appropriate Right/Left and 0, 2 or -2 designationfacing up and locked into position by rotatingthe tabs anteriorly to the stop. The tibial traytrial assembly remains in position and thespacer block is repositioned. This ensuresappropriate rotational orientation as previouslyestablished.The notch guide is assembled onto the IM rodand advanced to the prepared distal surface.Steinmann pins are introduced in the sequencedisplayed: anterior (1), contralateral distal (2),anterior (3) and distal (4).The spacer block is subsequently removed.25
The notch and chamfer cuts can be madewith an oscillating saw with the rod andsleeve in position.The notch/chamfer bushing is subsequentlyremoved. The rod handle is reassembledand the IM rod and sleeve carefully disengagedfrom the reamed canal to preserve the established configuration. The security of the notchguide is confirmed.26
The length of the intercondylar box differs forthe P.F.C. Sigma Stabilized and TC3 femoralcomponents. Their respective transverse cutpositions are indicated on the anterior surfaceof the guide: basing the TC3 cut on the proximal surface of the guide bar, the Stabilized(designated STAB) on the distal. Resection isperformed either with an oscillating saw usinga 1 2'' blade or with an osteotome.TC3TC3STABTC3STABSTAB27
THE TRIAL FEMORAL COMPONENTTHE FEMORAL COMPONENT BOXASSEMBLY1) Place the two outrigger tabs of the box trial intothe recesses of the posterior condyles.2) Insert the two anterior tabs into the recesses ofthe anterior flange.3) Turn the angled screw, located in the side of thebox, until tight.Note: Do not over tighten the screw or attempt toremove the screw from the box trial as this willresult in damage to the box trial attachment.The femoral trial is positioned on the prepared distal femur, and the accuracy of the cuts is evaluated.Where the component tends to rotate posteriorly(rocking into flexure) the A/P cuts may requireadjustment. Where there is lateral rocking, thedepth of the notch is inadequate.All appropriate modifications are made at this time.28
The trial fluted femoralstem, corresponding insize to the final reameremployed and to theestablished depth, isassembled to the trialfemoral component.The appropriate bolt, 0or 2/-2, corresponding to the bushingselected for the A/P cutting block andnotch/chamfer guide is passed through thehole in the box of the distal femur. As illustrated, if the 2/-2 bolt is used, the arrow ispointing to the direction in which the stem willbe placed. When the arrow is pointing to theanterior part of the femoral component, thestem is located 2 mm anterior to the 0 mm position, resulting in the femoral component shifting 2 mm posterior relative to the stemposition. This is referred to as the 2 mm position. Subsequently, if the arrow ispointing to the posteriorpart of the femoral component, the stem is located2 mm posterior to the0 mm position, resultingin the femoral componentshifting 2 mm anterior relative to the stem position.This is referred to as the–2 mm position.29
The appropriate trial femoral stem collarassembly, 5 or 7 , corresponding to the bushing used on the A/P cutting block and thenotch/chamfer guide is selected. The collarswivels to adjust for either a right or left orientation and is assembled with the markingsfacing the posterior trial femoral component.The bolt is introduced through the femoral boxtrial and into the trial femoral stem assembly,and is tightened with the trial femoral stemassembly wrench.To ensure the proper assembly, there are threevisual checks: (1) the arrow on the bolt is pointing to the desired position; (2) the lateral side ofthe collar and the box trial are aligned, as illustrated on page 29; and (3) the collar is positioned on the trial femoral component such thatthe angle and the orientation are viewed fromthe posterior trial femoral component.The trial fluted femoral stem, corresponding insize to the final reamer employed and to theestablished depth, is assembled to the trialfemoral component.30
Where augmentation is employed, the appropriate trial distal and posterior augmentationcomponents are assembled to the trial. The trialcomponent is gently impacted into positionallowing for possible discrepancy between thestem and prepare
Surgical Technique 2 Initial Preparation of the Tibia 8 Preparation of the Femur 14 Distal Resection 19 Anterior/Posterior Resection 21 Notch and Chamfer Resection 25 Final Preparation of the Tibia 32 Preparation of the Patella 36 Assembling the Prosthesis 38 Appen
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