import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Location**: 2cm posterior to tibial plateau, runs within popliteal fossa between medial and lateral heads of gastrocnemius **Protection**: Mark maximum drill depth on all tibial instruments, use depth stops, avoid posterior cortex breach during tibial stem preparation and cement removal, maintain knee flexion during posterior work **Location**: Crosses fibular neck 3-4cm below fibular head, wraps around lateral fibular neck, at risk with valgus correction and lateral retraction **Protection**: Minimize lateral retraction, use bent retractors around fibular head, release lateral structures before valgus correction >10°, avoid lateral stem perforation **Location**: Patellar tendon from patella to tibial tubercle, quadriceps tendon from VMO/VL/VI/RF to patella, at risk during exposure and closure **Protection**: Never force patellar eversion - use extensile exposure if tight, careful TTO technique (5-7cm osteotomy, 1cm thick, hinge laterally), meticulous repair with non-absorbable suture **Location**: Medial genicular branches supply knee skin; multiple parallel incisions compromise lateral-to-medial flow **Protection**: Use most LATERAL previous incision if multiple scars, avoid undermining flaps, full-thickness skin dissection, never create bridge between parallel scars less than 7cm apart **Location**: Posterior cortex only 2cm anterior to popliteal artery; at risk during tibial stem reaming, cement removal, and component extraction **Protection**: Use fluoroscopy to confirm instrument position, hand ream initially, mark maximum depth on all instruments, avoid excessive posterior angulation of tibial stem ## Anderson Orthopaedic Research Institute Classification **Purpose**: Standardized assessment of bone loss to guide reconstruction strategy ### Type 1 - Intact Metaphysis - Minor bone defects only, intact supportive metaphyseal bone - **Reconstruction**: Primary-style components with or without stems - Small defects: cement fill or morselized bone graft - Stems optional but often used for added stability ### Type 2A - Unilateral Damage - One condyle (femur) or one plateau (tibia) involved - Metaphyseal bone damaged on ONE side only - **Reconstruction**: Unilateral augments (5-10mm metal blocks) - Short stems (100mm) mandatory for fixation bypass - Opposite side intact provides reference for sizing ### Type 2B - Bilateral Damage - BOTH condyles or BOTH plateaus involved - Metaphyseal bone damaged bilaterally - **Reconstruction**: Large augments OR metaphyseal cones/sleeves - Longer stems (150mm) for better diaphyseal fixation - Cones provide osseointegration platform for biologic fixation ### Type 3 - Deficient Metaphysis - Non-supportive metaphyseal bone, cannot support implant - Massive bone loss precludes standard reconstruction - **Reconstruction Options**: - Structural allograft (distal femoral or tibial head) - Tumor prosthesis (distal femoral replacement) - Arthrodesis if salvage impossible - Consider amputation if no viable reconstruction ## Three Extensile Techniques for Difficult Revision ### 1. Quad Snip (Insall) - **Technique**: 45° oblique incision into vastus lateralis, 3-4cm proximal to superior arthrotomy edge - **Indications**: Standard first-line extensile exposure - **Advantages**: Simple, effective, heals without special protocol - **Disadvantages**: Limited additional exposure vs TTO - **Postop**: No special restrictions ### 2. VY Turndown (Coonse-Adams) - **Technique**: Split quadriceps tendon midline proximally 5-8cm, turn down as VY flap - **Indications**: Very stiff knees requiring maximum exposure - **Advantages**: Greatest exposure of three techniques - **Disadvantages**: Compromises extensor mechanism, quad weakness common (10-20% extensor lag) - **Postop**: Protected extension, cautious rehab ### 3. Tibial Tubercle Osteotomy (TTO) - GOLD STANDARD - **Technique**: 5-7cm osteotomy of tibial tubercle, 1cm thick, hinged laterally on periosteum - **Indications**: Difficult revisions, stiff knees, need for maximum exposure with mechanism preservation - **Advantages**: Excellent exposure, preserves extensor mechanism, reliable healing (95-98%) - **Disadvantages**: Requires specific fixation, postop restrictions - **Fixation**: 2-3 bicortical screws (4.5mm lag) + cerclage wire - **Postop**: NWB 6 weeks, NO active SLR 6 weeks, union 8-12 weeks ## Constraint Ladder Based on Ligament Status ### Posterior Stabilized (PS) - **Ligament Status**: Both MCL and LCL intact and functional - **Stability Test**: Less than 5mm varus-valgus opening - **Mechanism**: Cam-post mechanism replaces PCL function - **Constraint Level**: Least constrained, allows full rotation - **Use in Revision**: Uncommon - most revisions have some ligament compromise ### Constrained Condylar Knee (CCK) - **Ligament Status**: MCL attenuated or deficient (5-10mm opening) - **Stability Test**: Firm endpoint with moderate opening - **Mechanism**: Larger post, tighter tolerance, deeper femoral box cut - **Constraint Level**: Varus-valgus constraint within ±8°, allows 5-6° rotation - **Use in Revision**: MOST COMMON choice - provides inherent stability ### Rotating Hinge - **Ligament Status**: Both collaterals deficient or absent (greater than 10mm opening, no endpoint) - **Stability Test**: Gross instability, no soft tissue constraint - **Mechanism**: Linked hinge mechanism with rotating platform - **Constraint Level**: Full coronal and sagittal constraint, axial rotation only - **Use in Revision**: Reserved for severe cases - increases bone-implant stress ### Key Principles - **Under-constraining** = instability, dislocation, reoperation - **Over-constraining** = accelerated loosening from increased interface stress - Match constraint to ligament status, not bone loss ## Defect Reconstruction Options ### Augments (Metal Blocks) - **Indications**: Contained defects 5-10mm - **Types**: Distal, posterior, posterior-oblique (femur); medial, lateral (tibia) - **Fixation**: Cemented separately or modular attachment to component - **Advantages**: Simple, reliable, time-tested - **Limitations**: Contained defects only, limited sizes ### Metaphyseal Cones - **Indications**: Uncontained defects greater than 10mm, Type 2B/3 bone loss - **Types**: Highly porous tantalum (Trabecular Metal) or titanium - **Mechanism**: Press-fit into metaphyseal defect, osseointegrates over time - **Fixation**: Press-fit only (do NOT cement bone-cone interface) - **Component Interface**: Cement component onto cone - **Advantages**: Biologic fixation, excellent outcomes (95%+ survival at 10 years) ### Metaphyseal Sleeves - **Indications**: Similar to cones, alternative design - **Difference**: Cylindrical shape extending into diaphysis vs conical - **Fixation**: Press-fit with cortical contact - **Advantages**: May provide more diaphyseal stability ### Structural Allograft - **Indications**: Type 3 defects, massive bone loss - **Types**: Distal femoral allograft, tibial head allograft - **Fixation**: Plate and screw fixation to host bone - **Disadvantages**: Higher failure rates, infection risk, slow incorporation ### Tumor Prosthesis - **Indications**: Type 3 defects where allograft not feasible - **Types**: Distal femoral replacement, proximal tibial replacement - **Considerations**: Last resort before arthrodesis ## Revision TKR Outcomes and Registry Data ### AOANJRR Data (Australian Registry) - **Primary TKR**: 15-year cumulative revision rate 8.9% - **Revision TKR**: Higher re-revision rates than primary - **Most Common Revision Indications**: Loosening (30%), infection (25%), instability (10%) - **Constraint Level**: Higher constraint associated with higher re-revision rates ### Survival Rates by Reconstruction Type - **Augments Only**: 90-95% survival at 10 years - **Metaphyseal Cones**: 93-97% survival at 10 years (excellent results) - **Metaphyseal Sleeves**: 92-96% survival at 10 years - **Structural Allograft**: 70-85% survival at 10 years (lower than metal options) - **Tumor Prosthesis**: 60-80% survival at 10 years (higher complication rates) ### Constraint Level Outcomes - **PS in Revision**: Limited data, higher instability rates if ligaments compromised - **CCK**: Most commonly used, good balance of stability and loosening risk - **Rotating Hinge**: Higher loosening rates long-term (50-70% at 15 years) ### Key Evidence - **Metaphyseal Cones**: Morgan-Jones, Howard et al. 2015 - 97% survival at 5 years - **Sleeve Fixation**: Dalury, Barrett et al. 2016 - 94% survival at 7 years - **Constraint Selection**: Lachiewicz, Soileau 2011 - CCK preferred for most revisions ### Infection Considerations - **Two-Stage Revision**: Gold standard for infected TKR (90% cure rate) - **One-Stage Revision**: Selected cases only (low-virulence, healthy host) - **Antibiotic Cement**: Spacer contains 3-6g vancomycin + aminoglycoside per 40g cement **Patient Position**: Supine with thigh support/leg holder. Tourniquet available (may limit to 90 min or avoid). Prepare for extensive exposure. **Surgical Approach**: Previous midline incision, may need extensile exposure (quad snip, VY turndown, tibial tubercle osteotomy) **Incision**: Previous midline or most lateral scar, 15-20cm, extending proximal and distal ### Step 1: Preoperative Planning & Infection Workup Preoperative Planning & Infection Workup: MANDATORY INFECTION WORKUP: ESR >30 or CRP >10 mm/hr suggests infection. Joint aspiration with cell count (WCC >3000 cells/μL concerning), differential (>80% PMNs suggests infection), culture (hold 14 days for low-grade organisms), alpha-defensin test (high sensitivity/specificity). If positive: 2-STAGE REVISION protocol. IMPLANT IDENTIFICATION: review operative notes, contact AOANJRR (Australian registry), analyze X-ray features (cruciate-retaining vs PS vs CCK), contact manufacturer for explant tools. CT SCAN with metal artifact reduction for bone loss assessment (AORI classification). TEMPLATE: measure bone defects, plan for AORI reconstruction (augments, cones/sleeves, stems 100-150mm), determine constraint level needed based on ligament status, plan for backup implants. **Technical Tip**: EXAM KEY: 'Before ANY revision TKR, must RULE OUT INFECTION. This is MANDATORY. ESR >30, CRP >10, or aspiration WCC >3000 (>80% PMNs) suggests infection requiring 2-stage revision. Cannot proceed to 1-stage revision with positive infection workup - reinfection rate approaches 80%. Identify implant brand - need correct extraction equipment or risk massive bone destruction. I template comprehensively: AORI bone loss classification, stem lengths (typically 100-150mm for 4-6cm diaphyseal fixation), augment sizes, constraint level. Must have backup implants available - bone loss often worse than expected on X-ray.' - Missing occult infection = disaster (reinfection rate >80%, may lose limb) - Wrong extraction equipment = extensive bone destruction trying to remove components - Inadequate implant inventory = aborted procedure or suboptimal reconstruction - Underestimating bone loss on plain X-rays (CT more accurate) ### Step 2: Positioning & Tourniquet Strategy Positioning & Tourniquet Strategy: Position supine with leg holder or thigh post allowing knee flexion >120°. TOURNIQUET DECISION: Many revision surgeons AVOID tourniquet or limit to 90 minutes. Rationale: (1) Better cement penetration into sclerotic bone when bleeding (cement fills vascular channels), (2) Allows monitoring of vascular status, (3) Avoids tourniquet-related complications in prolonged case. If using tourniquet: set to 100mmHg above systolic, exsanguinate with elevation (not Esmarch if PVD suspected). Prepare ENTIRE leg circumferentially sterile - may need longer stems, may need to extend proximally if bone loss worse than expected. Cell saver available for blood conservation. Antibiotics within 60 minutes (cefazolin 2g or vancomycin 15mg/kg if MRSA risk or PCN allergy). **Technical Tip**: EXAM KEY: 'Supine with leg holder allowing >120° flexion for tibial exposure. Many surgeons AVOID tourniquet in revision - rationale is better cement interdigitation in bleeding sclerotic bone vs bloodless field. If using tourniquet, limit to 90 minutes to reduce compartment syndrome risk in prolonged case. I prepare full leg circumferentially sterile - may need longer stems if metaphyseal bone loss worse than templated, and access to entire leg allows stem passage. Cell saver reduces transfusion needs in these higher blood loss cases.' - Prolonged tourniquet time (>120 min) = compartment syndrome risk increases significantly - Not preparing full leg = unable to extend stem if needed (aborted case) - PVD with tourniquet = ischemic complications - No cell saver = higher transfusion rates (revision TKR loses more blood than primary) ### Step 3: Incision Planning & Skin Entry Incision Planning & Skin Entry: INCISION SELECTION CRITICAL: If multiple previous incisions, use MOST LATERAL incision (preserves medial blood supply to skin). If scars <7cm apart, use most lateral. If scars >7cm apart, use closest to midline. Excise previous scar en bloc with full-thickness elliptical incision. Midline incision preferred if no previous scar. Skin length 15-20cm (longer than primary). Full-thickness flaps to avoid undermining. Raise medial and lateral flaps carefully off deep fascia. Assess flap vascularity - white, non-bleeding edges suggest vascular compromise. Medial parapatellar arthrotomy standard (8-10cm proximal to patella superior pole, curving medially around patella, extending to tibial tubercle). Extend arthrotomy PROXIMALLY into quadriceps tendon to facilitate exposure. Release adhesions between quad tendon and femur. Attempt patellar eversion gently - DON'T FORCE. **Technical Tip**: EXAM KEY: 'Incision choice is critical in revision TKR. Multiple parallel scars <7cm apart increase necrosis risk - use most lateral incision to preserve medial blood supply. I excise previous scar, create full-thickness flaps without undermining. Standard medial parapatellar arthrotomy extended PROXIMALLY into quadriceps. Release all adhesions but don't force patellar eversion - if stuck despite adhesiolysis, need extensile exposure. Forced eversion = patellar tendon avulsion disaster.' - Wrong incision choice (parallel scar <7cm) = skin necrosis requiring flap coverage - Thin flaps with undermining = marginal blood supply, necrosis - Forced patellar eversion = patellar tendon avulsion (catastrophic complication requiring allograft reconstruction) - Inadequate proximal quadriceps release = cannot expose femur, need extensile approach ### Step 4: Extensile Exposure Selection Extensile Exposure Selection: THREE MAIN EXTENSILE TECHNIQUES if standard approach inadequate: (1) QUAD SNIP (Insall): 45° oblique incision into vastus lateralis, 3-4cm proximal to superior arthrotomy edge. Simple, effective, heals reliably, no special postop protocol. Most common. (2) VY TURNDOWN (Coonse-Adams): Split quadriceps tendon in midline proximally 5-8cm, turn down as VY flap. More exposure than quad snip but compromises extensor mechanism - quad weakness common, repair complex. Reserved for very difficult cases. (3) TIBIAL TUBERCLE OSTEOTOMY (TTO): 5-7cm osteotomy of tibial tubercle, 1cm thick, hinged laterally on periosteum and patellar tendon. GOLD STANDARD for difficult revisions - excellent exposure, preserves extensor mechanism, heals reliably. Fixation with 2-3 bicortical screws (4.5mm) and cerclage wire. Postop: NWB or TTWB 6 weeks, no active SLR 6 weeks. **Technical Tip**: EXAM KEY: 'Extensile exposure often needed in revision. Three options: QUAD SNIP most common - 45° into vastus lateralis, 3-4cm proximal to arthrotomy, heals without special protocol. VY TURNDOWN gives most exposure but weakens quad - reserve for very stuck knees. TIBIAL TUBERCLE OSTEOTOMY is my preferred approach for difficult revisions - gold standard because it provides excellent exposure while preserving extensor mechanism and heals reliably. TTO technique: 5-7cm long, 1cm thick, hinged laterally, fixed with 2-3 screws plus wire. Postop NWB 6 weeks, no active SLR 6 weeks, union 8-12 weeks.' - Quad snip too distal = extends into arthrotomy (ineffective) - Quad snip too far lateral = into vastus lateralis muscle belly (bleeding) - VY turndown = significant quad weakness (10-20% extensor lag common) - TTO fracture during osteotomy = complex fixation problem - TTO non-union postop (2-5%) = persistent pain, extensor lag - TTO displacement with early weight-bearing or active extension ### Step 5: Component & Polyethylene Removal Component & Polyethylene Removal: SYSTEMATIC APPROACH: (1) Remove polyethylene INSERT first (easiest with knee flexed, gives access to interfaces). (2) Break cement-bone interface circumferentially: thin flexible osteotomes (3-5mm), Gigli saw posteriorly if accessible. Work methodically around entire component - femoral condyles, posterior condyles, tibial base. (3) FEMORAL COMPONENT removal: universal femoral extractor or brand-specific slap hammer system. Apply to anterior flange, impact carefully. If well-fixed, may need multiple osteotomes simultaneously. (4) TIBIAL COMPONENT removal: universal tibial extractor. Beware posterior cortex perforation. (5) CEMENT REMOVAL: ALL cement must be removed for stem fixation - ultrasonic cement removal (vibrates cement-bone interface), high-speed burr with careful technique, thin straight osteotomes in canals. Curettes for small fragments. May need canal reaming to achieve clean diaphyseal bone for stem. Preserve bone - accept some cement if removal risks significant fracture. Inspect for membrane (indicates loosening). **Technical Tip**: EXAM KEY: 'I remove polyethylene first - gives access. Break cement-bone interface methodically with thin flexible osteotomes and Gigli saw posteriorly. Specialized extraction instruments ESSENTIAL for each brand - universal extractors available but brand-specific better. Key principle: PRESERVE BONE - accept some cement residue if removal risks fracture, but ALL canal cement must be removed for stem fixation. Ultrasonic cement removal extremely useful - vibrates interface without osteotome trauma. Complete cement removal from medullary canals critical - residual cement prevents stem seating and fixation. May need sequential reaming to clear canals.' - Fracture during extraction (femoral condyle, tibial plateau, femoral shaft) - requires immediate fixation and changes implant plan - Aggressive bone loss from osteotomes - increases AORI grade, worsens prognosis - Retained cement in canal = inadequate stem fixation = early loosening - Popliteal artery injury from posterior tibial cortex breach during cement removal or reaming (catastrophic) - Anterior cortex perforation of femur during canal preparation - Not having extraction equipment = prolonged surgery time, excessive bone loss ### Step 6: Bone Loss Assessment - AORI Classification Bone Loss Assessment - AORI Classification: ASSESS WITH TRIAL COMPONENTS IN SITU: AORI (Anderson Orthopaedic Research Institute) CLASSIFICATION guides reconstruction: TYPE 1 (intact metaphyseal bone, minor defects) - primary components with or without stems, minimal augmentation, cement/bone graft for small defects. TYPE 2A (damaged metaphyseal bone, ONE condyle/plateau involved) - small/medium augments (5-10mm), short stems (100mm), unilateral reconstruction. TYPE 2B (damaged metaphyseal bone, BOTH condyles/plateaus involved) - large augments (>10mm), metaphyseal cones or sleeves, longer stems (150mm), bilateral reconstruction. TYPE 3 (deficient metaphysis, non-supportive bone) - massive structural allograft (femoral or tibial head), metaphyseal sleeves with stems, tumor prosthesis (distal femoral replacement or hinged knee with long stems), or consider arthrodesis. Assess BOTH femoral and tibial bone loss separately. Contained vs uncontained defects. Confirm with trial spacers. **Technical Tip**: EXAM KEY: 'AORI classification is the standard: Type 1 = intact metaphysis (primary components work, stems optional). Type 2 = damaged metaphysis - A is one side, B is both sides - requires augments, cones/sleeves, and stems mandatory. Type 3 = deficient unsupportive metaphysis - needs structural allograft, tumor prosthesis, or consider arthrodesis if salvage. I assess bone loss WITH TRIAL COMPONENTS IN PLACE - this shows what will support implants. Classify femur and tibia separately. Type 1: augments <5mm, stems optional. Type 2A/2B: augments 5-15mm or cones/sleeves, stems 100-150mm mandatory. Type 3: consider salvage options, prognosis poor. Know that bone loss often worse than X-ray suggests - CT better for assessment.' - Underestimating bone loss = inadequate implant choice = early failure - Not having appropriate implants available (augments, cones, long stems) = aborted case or suboptimal reconstruction - Type 3 bone loss without salvage options = may require arthrodesis or amputation - Contained vs uncontained distinction important - uncontained requires different reconstruction (cones vs augments) ### Step 7: Soft Tissue & Ligament Assessment Soft Tissue & Ligament Assessment: LIGAMENT-BASED CONSTRAINT DECISION: Insert trial spacer block (8-10mm). Assess MCL and LCL integrity in extension and throughout flexion arc. GRADING: Grade 0 (intact, <5mm opening to varus/valgus stress) = both collaterals functional, PS possible. Grade 1 (5-10mm opening, firm endpoint) = MCL attenuated, CCK recommended. Grade 2 (>10mm opening, no endpoint) = MCL deficient, CCK minimum, consider rotating hinge. Grade 3 (both collaterals deficient) = rotating hinge mandatory. Test in extension, 30° flexion, 90° flexion. PCL rarely relevant in revision (usually sacrificed in primary PS knee or incompetent). EXTENSOR MECHANISM: assess patellar bone stock (may be severely deficient from multiple previous resurfacings), quadriceps and patellar tendon quality (chronic tear?), tracking (lateral subluxation suggests VMO deficiency). May need lateral release. Severely deficient patella = consider patellar resection (patellectomy) vs no resurfacing vs augments. **Technical Tip**: EXAM KEY: 'Constraint decision based on LIGAMENT STATUS with spacer trial in situ. Both collaterals intact (<5mm varus-valgus laxity): PS implant possible but most use CCK for revision given bone loss. MCL attenuated or deficient (5-10mm opening): CCK mandatory - provides varus-valgus constraint. Both collaterals gone (>10mm or no endpoint): rotating hinge. PCL status rarely matters in revision. Key principle: don't UNDER-constrain (leads to instability) but also don't OVER-constrain (increases stress on bone-implant interface, accelerates loosening). CCK allows ±8° varus-valgus but preserves some rotation (5-6°). Hinge fully constrains coronal and sagittal plane (allows axial rotation only). Extensor mechanism: assess patella bone stock - may be paper-thin from multiple resurfacings. Options: resurface if >10mm bone, augment if 5-10mm, leave unresurfaced if <5mm (patelloplasty), or patellectomy if severe arthritis.' - Under-constraining (PS with MCL deficiency) = instability, dislocation, reoperation - Over-constraining (hinge with intact collaterals) = accelerated loosening from increased constraint forces - Poor extensor mechanism assessment = patellar fracture, tendon rupture, maltracking postop - Inadequate lateral release with tight lateral structures = patellar maltracking, anterior knee pain - Patella too thin for resurfacing (<10mm) = fracture risk ### Step 8: Femoral Reconstruction Femoral Reconstruction: DEFECT RECONSTRUCTION LADDER: Small defects (<5mm) = cement or morselized bone graft. Medium defects (5-10mm) = AUGMENTS (modular metal blocks, cemented separately or built-in to component) - posterior, distal, or posterior-oblique. Large defects (>10mm metaphyseal, uncontained) = METAPHYSEAL CONES or SLEEVES (porous metal cones press-fit into metaphysis, provide stable platform, osseointegrate over time). Sleeve vs cone: sleeve cylindrical and extends into diaphysis, cone conical and seats in metaphysis. SIZE FEMORAL COMPONENT after defect reconstruction: choose size matching intact bone (not deficient condyle). AP and ML sizing. ROTATION critical: 3° external to transepicondylar axis, or parallel to posterior condyles of non-deficient side, or perpendicular to Whiteside's line. FEMORAL STEM: press-fit (preferred if canal adequate) requiring 50-100mm diaphyseal fixation (4-6cm), or cemented if poor bone quality. Stems should bypass metaphyseal defects - goal is diaphyseal fixation. Offset stems available for bowed femurs or canals with deformity. Modular vs fixed stem. **Technical Tip**: EXAM KEY: 'Femoral reconstruction follows defect ladder: <5mm use cement, 5-10mm use augments, >10mm use cones or sleeves. Augments are modular metal blocks - cemented separately or built into component. Cones and sleeves for large uncontained metaphyseal defects - press-fit porous metal that osseointegrates, very successful. Size component to INTACT bone not deficient condyle. Rotation absolutely critical in revision - use multiple references (transepicondylar axis +3° ER, posterior condyles if one intact, Whiteside's line). FEMORAL STEM philosophy: must achieve 4-6cm (50-100mm) diaphyseal fixation bypassing metaphyseal defects. Press-fit stems preferred - rely on diaphyseal canal fill. Cemented stems if poor bone quality or cannot achieve press-fit. Modular systems allow intraop adjustment of offset and version. Offset stems essential for bowed femurs or post-fracture deformity.' - Augment not adequately supported by host bone = fracture or subsidence - Stem too short (<50mm diaphyseal fixation) = relies on failed metaphyseal bone, early loosening - Malrotation = patellar maltracking (internal rotation), pain, instability, accelerated wear - Femoral fracture during stem preparation (especially with previous deformity) - Cone/sleeve not adequately seated or press-fit = subsidence, failure to osseointegrate - Varus or valgus stem alignment = eccentric loading, loosening ### Step 9: Tibial Reconstruction Tibial Reconstruction: Similar reconstruction ladder to femur: AUGMENTS for contained defects 5-10mm. METAPHYSEAL CONES for uncontained defects >10mm (highly porous tantalum or titanium cones placed into metaphyseal defect, press-fit, osseointegrate - provide stable platform for tibial component). Cones placed BEFORE tibial tray - tray then cemented onto cone. SLEEVES alternative - cylindrical porous metal extending from metaphysis into diaphysis. SIZE TIBIAL COMPONENT to maximize coverage of intact bone - underhang preferable to overhang (avoid vascular and ligamentous impingement). CHECK ROTATION: align tibial component with 2nd ray (medial 1/3 of tibial tubercle), match native rotation, ensure symmetric flexion/extension gaps. Tibial tubercle should be MIDLINE or slightly lateral (never medial). TIBIAL STEM: 100-150mm length (longer than femoral stem), cemented or press-fit. CRITICAL: POSTERIOR CORTEX AWARENESS - popliteal artery 2cm from posterior cortex. Mark drill depth, use depth stop, careful reaming. Stems must engage diaphysis in at least one plane (press-fit) or can be fully cemented. Offset stems if needed for deformity. **Technical Tip**: EXAM KEY: 'Tibial reconstruction mirrors femur: augments 5-10mm, cones >10mm for metaphyseal defects. Metaphyseal cones are game-changer in revision - tantalum or titanium porous metal cones press-fit into defect, osseointegrate, provide stable biologic platform. Place cone first, then cement tibial component onto cone. Very successful technique for Type 2B/3. Size tibial tray to maximize coverage - slight underhang OK (better than overhang). ROTATION critical - align with 2nd ray, tubercle midline or slightly lateral, match native rotation. Malrotation causes pain and patellar maltracking. TIBIAL STEM must engage diaphysis 4-6cm. Critical danger: POSTERIOR CORTEX perforation during stem prep. Popliteal artery only 2cm from posterior cortex - perforation = catastrophic vascular injury. I always mark maximum drill depth and use depth stop. Press-fit stem needs good canal fit. Cemented stem if poor bone or press-fit inadequate.' - POSTERIOR CORTEX PERFORATION = popliteal artery injury 2cm away (catastrophic, may require amputation) - Malrotation = patellar maltracking, pain, instability, accelerated poly wear - Cone not seated properly = subsidence, failure, pain - Stem perforation lateral = peroneal nerve injury (foot drop) - Stem too short = relies on damaged metaphysis, early subsidence - Tibial tray overhang = soft tissue impingement, pain, neurovascular compression - Undercorrection of tibial slope = instability or hyperextension; overcorrection = flexion loss ### Step 10: Trialing, Gap Balancing & Alignment Trialing, Gap Balancing & Alignment: Insert trial components with appropriate augments, cones/sleeves, and stems. ASSESS ALIGNMENT: mechanical axis should pass through center of knee (55% through lateral compartment). Varus/valgus <3° acceptable. Check with trial components and assess under image intensifier if available. ASSESS STABILITY: Extension gap and flexion gap testing. In revision often have asymmetric gaps due to bone loss - may need to accept slight imbalance to preserve bone stock. Insert trial poly of appropriate thickness - aim for 10-12mm but stability more important than thickness. Test medial/lateral laxity (varus/valgus stress). Test anteroposterior stability (drawer test). CCK should be stable throughout arc with mild varus-valgus laxity preserved. PATELLAR TRACKING: assess with trial components through full ROM. No-thumb test (patella centers without manual pressure). Patella should track centrally without subluxation. May need lateral release if tight (pie-crust technique or formal Z-lengthening). CHECK ROM: aim for 0-110° (0-120° better). Assess extension fully (no flexion contracture). Assess for midflexion instability (loose in midflexion, tight in extension/flexion = indicates incorrect gap balancing). **Technical Tip**: EXAM KEY: 'Revision gap balancing much more challenging than primary due to asymmetric bone loss. May need to accept slight imbalance rather than over-resect and worsen bone stock. CCK provides inherent stability compensating for imperfect soft tissue balance - this is advantage over PS. I assess alignment - mechanical axis through knee center. Check stability throughout arc with trial poly: varus-valgus laxity (should have mild laxity in CCK, none in hinge), AP stability (drawer test). Patellar tracking critical - no-thumb test, should center without subluxation. Lateral release if needed. ROM goals: 0-110° minimum, 0-120° preferred. Flexion contracture unacceptable - may need posterior capsule release or downsize femur. Midflexion instability suggests gap mismatch.' - Over-resection to balance gaps = worsens bone loss, may escalate to Type 3 defects - Under-constraining = instability postop, reoperation - Maltracking patella = anterior knee pain, patellar complications, patient dissatisfaction - Flexion contracture accepted = poor function, patient dissatisfaction - Midflexion instability (loose in midflexion) = cam-post problems or gap mismatch requiring revision - Overstuffing joint (poly too thick) = stiffness, limited ROM; understuffing = instability ### Step 11: Cementation Technique & Final Components Cementation Technique & Final Components: METICULOUS CEMENTATION CRITICAL: Clean and dry all bone surfaces. Pulse lavage entire field. Dry with suction and sponges. Apply cement restrictors in canals if needed. High-viscosity antibiotic-loaded cement (gentamicin or tobramycin). CEMENT APPLICATION: Pressurize into sclerotic bone with cement gun. Paint onto back of augments. Fill metaphyseal defects. For cones/sleeves: cement component onto cone, press-fit cone into metaphysis (do NOT cement cone-bone interface - needs osseointegration). STEM FIXATION STRATEGY: HYBRID (cement component/augments, press-fit stem - most common) or FULLY CEMENTED (cement component AND stem if press-fit inadequate). If cementing stem, centralize in canal, avoid stem-in-cement-in-bone (weak), want stem-cement interdigitation. Remove excess cement especially POSTERIORLY (impingement) and from cam-post mechanism. INSERTION SEQUENCE: (1) Insert tibial component with stem, cement onto cone if used, remove excess cement. (2) Insert femoral component with stem, cement onto augments, remove excess cement. (3) While cement curing, insert TRIAL POLY to compress interfaces and remove excess cement extruding into joint. (4) After cement cured, remove trial poly, insert FINAL POLY (modular locking poly - ensure locked). CHECK FINAL STABILITY: repeat stability testing, confirm ROM, check tracking. **Technical Tip**: EXAM KEY: 'Cement technique is absolutely critical in revision with poor bone quality. I use high-viscosity antibiotic cement, pressurize with cement gun into sclerotic bone. Pulse lavage and dry bone first. Cones/sleeves: DO NOT CEMENT bone-cone interface - press-fit only for osseointegration. Cement component onto cone. Stems: hybrid fixation most common - cement component and augments, press-fit stem into diaphysis. If cannot achieve press-fit (poor bone, wide canal), fully cement stem. Cemented stems: avoid stem-in-cement-in-bone technique (weak) - want cement interdigitated with bone and stem. Remove ALL excess posterior cement - causes impingement and pain. Critical sequence: tibia first, femur second, TRIAL poly while cement cures to compress interfaces and extrude excess cement, then final poly after curing. Ensure final poly locked securely - dissociation is a complication.' - Poor cement penetration in sclerotic bone = early loosening (most common failure mode) - Posterior cement extrusion = impingement, pain, limited flexion, may need reoperation - Cementing cone-bone interface = prevents osseointegration, failure - Stem-in-cement-in-bone technique = weak construct, failure - Components not fully seated = proud component, subsidence, early failure - Cam-post mechanism cement = catching, dissociation, instability - Polyethylene not locked = dissociation (sudden instability and pain) - Cement on articulating surfaces = rapid poly wear ### Step 12: Closure & Tibial Tubercle Fixation Closure & Tibial Tubercle Fixation: If TTO performed: Carefully reduce tibial tubercle to anatomic position. FIX WITH 2-3 bicortical screws (4.5mm cortical screws) placed in lag fashion through tubercle into posterior cortex. Add CERCLAGE WIRE or HEAVY SUTURE (Fiberwire #5) around proximal tibia for rotational control and compression. Test fixation stability with gentle traction. Close periosteum over TTO if possible. CAPSULAR CLOSURE: Repair capsule and arthrotomy in layers with interrupted 0-Vicryl. If quad snip performed, repair with interrupted 0-Vicryl sutures. Ensure extensor mechanism continuity - no gaps. PATELLAR CLOSURE: Repair retinaculum if possible. If tissue deficient, may need synthetic mesh (Marlex) reinforcement. TEST FINAL ROM passive - should maintain 0-110° achieved during trialing. SUBCUTANEOUS: Close in layers, 2-0 Vicryl to deep tissue. SKIN: Staples or interrupted nylon sutures. DRAIN: controversial - many use deep drain (12-24hr removal). DRESSING: Compressive but not circumferential. KNEE IMMOBILIZER or hinged brace if instability concerns or TTO performed. **Technical Tip**: EXAM KEY: 'If TTO: Fixation absolutely critical - 2-3 bicortical screws in lag fashion plus cerclage wire around proximal tibia for rotation control and compression. Test stability. Postop protocol for TTO: NWB or toe-touch weight bearing for 6 weeks, NO active SLR for 6 weeks (protects TTO and extensor mechanism), passive ROM only initially. TTO union takes 8-12 weeks - X-ray surveillance. Quad snip heals without special precautions - just repair well. I close capsule and arthrotomy meticulously in layers - extensor mechanism integrity critical. Test final passive ROM - should maintain trial ROM. Drain controversial - I use for 12-24 hours. Compression dressing, immobilizer if TTO or instability concern.' - TTO inadequate fixation = non-union or displacement (early weight-bearing or active SLR causes this) - TTO screws too anterior = fracture through tubercle; too posterior = intraarticular - Early active extension with TTO = avulsion, failure, extensor lag - Poor capsular repair = extensor lag, weakness - Hematoma formation = arthrofibrosis, infection risk - Drain left >48 hours = increased infection risk - Circumferential tight dressing = compartment syndrome in this higher-risk population ### Step 13: Confirm Final Assessment & Documentation Confirm Final Assessment & Documentation: Before leaving OR: FINAL CHECKS - (1) Stability throughout ROM, (2) Alignment under image intensifier if available, (3) ROM documented (extension/flexion), (4) All sponges and instruments accounted for, (5) Hemostasis adequate. INTRAOPERATIVE X-RAYS: AP and lateral to confirm component position, stem seating, alignment. OPERATIVE NOTE DOCUMENTATION critical: (1) Findings (AORI bone loss grade, ligament status, removed implant details), (2) Reconstruction (augments used, cone/sleeve sizes, stem lengths and fixation method, constraint level, poly thickness), (3) Final alignment and ROM, (4) Complications if any, (5) Implant stickers in chart. IMPLANT TRACKING: Record all lot numbers, register with AOANJRR (Australia), document for future reference. **Technical Tip**: EXAM KEY: 'Before closing, systematic final check: stability throughout arc, alignment verified, ROM measured and documented, all counts correct, hemostasis adequate. Intraop X-rays confirm component position and stem seating - especially important in revision. Operative note documentation is medico-legally critical and helps future surgeons if re-revision needed: record AORI grade, ligaments, implants removed, new implants used with all specifics (stem lengths, augment sizes, cone types, constraint), final alignment and ROM. Register implants with AOANJRR - Australia tracks revision outcomes. Implant stickers in medical record. This documentation may be crucial years later.' - Inadequate final stability check = missed instability requiring immediate reoperation - Poor documentation = medical-legal issues, future surgeons unable to identify implants - Not registering implants = cannot identify for future revision - Missed intraoperative fracture or malposition = poor outcome TTO or structural graft: NWB or TTWB 6 weeks, no active SLR 6 weeks, passive ROM only. Otherwise: WBAT immediately, active ROM day 1-2. Brace if instability concerns. Aggressive physiotherapy to prevent stiffness. Chemical DVT prophylaxis (LMWH or factor Xa inhibitor) for 14 days minimum. TTO X-rays at 2, 6, 12 weeks to assess union. Full clinic follow-up: 2wk (wound), 6wk (X-rays, progress weight-bearing if TTO), 3mo (X-rays, assess ROM and function), 6mo, 1yr, then annually. AOANJRR reporting. ## References 1. **Engh GA, Ammeen DJ.** Bone loss with revision total knee arthroplasty: defect classification and alternatives for reconstruction. *Instr Course Lect.* 1999;48:167-175. [AORI Classification original description] 2. **Parvizi J, Zmistowski B, Berbari EF, et al.** New definition for periprosthetic joint infection: from the Workgroup of the Musculoskeletal Infection Society. *Clin Orthop Relat Res.* 2011;469(11):2992-2994. [MSIS Criteria for PJI] 3. **Morgan-Jones R, Oussedik SIS, Graichen H, Haddad FS.** Zonal fixation in revision total knee arthroplasty. *Bone Joint J.* 2015;97-B(2):147-149. [Metaphyseal cone principles] 4. **Dalury DF, Barrett WP.** The use of metaphyseal sleeves in revision total knee arthroplasty. *Knee.* 2016;23(3):545-548. [Sleeve fixation outcomes] 5. **Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR).** Hip, Knee & Shoulder Arthroplasty: 2023 Annual Report. Adelaide: AOA; 2023. [Australian revision rates and outcomes] 6. **Vince KG, Long W.** Revision knee arthroplasty: the limits of press fit medullary fixation. *Clin Orthop Relat Res.* 1995;317:172-177. [Stem fixation principles] 7. **Barrack RL, Rorabeck C, Burt M, Sawhney J.** Pain at the end of the stem after revision total knee arthroplasty. *Clin Orthop Relat Res.* 1999;367:216-225. [Stem tip pain] 8. **Whiteside LA.** Soft tissue balancing: the knee. *J Arthroplasty.* 2002;17(4 Suppl 1):23-27. [Constraint selection principles] 9. **Kurtz SM, Ong KL, Lau E, Bozic KJ.** Impact of the economic downturn on total joint replacement demand in the United States: updated projections to 2021. *J Bone Joint Surg Am.* 2014;96(8):624-630. [Revision epidemiology] 10. **Lachiewicz PF, Soileau ES.** Ten-year survival and clinical results of constrained components in primary total knee arthroplasty. *J Arthroplasty.* 2006;21(6):803-808. [CCK outcomes]

Revision Total Knee Replacement - Comprehensive

Revision Total Knee Replacement - Comprehensive