import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Popliteal artery**. Location: Posterior to tibia in popliteal fossa, 1-2cm from posterior tibial cortex in flexion. Protection: Flex knee during posterior work, use Hohmann retractors with care, finger palpation before posterior resection. **Common peroneal nerve**. Location: Winds around lateral fibular neck, 2-3cm distal to fibular head. Protection: Avoid valgus correction >10° at once, protect lateral structures, release tourniquet before closure to check vascularity. **Patellar tendon**. Location: Inserts on tibial tubercle, at risk during exposure and extensile approaches. Protection: Careful eversion, tibial tubercle osteotomy if needed (12cm length), protect insertion during all exposure maneuvers. **Medial collateral ligament**. Location: Superficial MCL attaches to medial tibial metaphysis 6cm below joint, deep to pes anserinus. Protection: Preserve during tibial preparation, subperiosteal dissection if exposure needed. **Tibial cortex integrity**. Location: Thin anterior and medial cortex, especially with osteopenia or osteolysis. Protection: Avoid eccentric reaming, use intramedullary guide carefully, stop at cortical chatter, assess for stress risers post-operatively. ## AORI Bone Defect Classification **Type 1: Intact Metaphysis** - Minor cancellous defects only - Intact peripheral cortical rim - No subsidence or significant osteolysis - Treatment: Standard primary-sized components **Type 2A: Damaged Metaphysis, Intact Rim** - Cancellous bone loss but cortical rim intact - Cavitary defects without segmental loss - Treatment: Cement fill, screws, small modular augments (5-10mm) **Type 2B: Rim Deficient One Condyle** - Unilateral cortical rim deficiency - Requires structural support on affected side - Treatment: Metal augments, tantalum cone, metaphyseal sleeve **Type 3: Rim Deficient Both Condyles** - Bilateral cortical rim loss - Massive metaphyseal bone loss - Treatment: Large cones/sleeves both sides, structural allograft, hinged prosthesis, or megaprosthesis **Key Exam Points:** - Always classify defects AFTER cement removal (true defect revealed) - Posterior defects often underestimated - palpate carefully - Document with photographs for surgical planning ## Constraint Ladder for Revision TKR **Level 1: Posterior Cruciate Retaining (PCR)** - Intact PCL with good tension - Balanced flexion-extension gaps - Rare in revision setting - usually reserved for single-component exchange with intact soft tissues **Level 2: Posterior Stabilized (PS)** - PCL deficient or sacrificed - Ligaments otherwise intact - Most common constraint for isolated tibial revision **Level 3: Constrained Condylar Knee (CCK)** - MCL or LCL incompetence - Large femoral box/cam mechanism provides coronal stability - Taller polyethylene post (15-20mm) - Stems required on both components **Level 4: Rotating Hinge Knee (RHK)** - Global ligament insufficiency - Significant bone loss preventing valgus-varus stability - Allows flexion-extension + axial rotation (reduces interface stress) - Linked articulation **Level 5: Fixed Hinge** - Massive bone loss preventing rotation - Tumor reconstruction - Highest constraint and interface stress **Exam Tip:** Always move UP the ladder (increase constraint) if in doubt during surgery. Underconstrained TKR fails early from instability. ## Tibial Stem Fixation Strategies **Press-Fit (Cementless) Stems** - Requires good diaphyseal bone quality - 2° tapered stems achieve 3-point fixation - Biological fixation with porous coating - Best long-term survivorship - Line-to-line reaming (exact stem diameter) - WBAT restrictions first 6 weeks **Cemented Stems** - Useful in poor bone quality or elderly - Immediate full weight-bearing - Over-ream by 2mm for cement mantle - Third-generation cementing technique - Risk of cement extrusion posteriorly **Hybrid Fixation (Most Common)** - Press-fit stem into diaphysis - Cemented baseplate to metaphysis - Combines best of both techniques - Allows immediate weight-bearing - Biological diaphyseal fixation **Offset Stems** - For canal deformity or malunion - 2-4mm offset available - Allows optimal baseplate positioning independent of canal axis **Exam Tip:** Know stem length guidelines - short (50-75mm) for AORI 1-2A, long (100-150mm) for AORI 2B-3. Stem should bypass any defect by 2 cortical diameters. ## Options for Bone Defect Management **Cement + Screws (Type 2A)** - Small contained defects <5mm deep - Place screws in sclerotic bone first - Cement fills around screws - Not for peripheral/uncontained defects **Metal Augments (Type 2A-2B)** - Modular titanium or CoCr blocks/wedges - 5mm, 10mm, 15mm sizes - Screw-fixed to host bone - Cemented to baseplate - Maximum 15-20mm augmentation **Tantalum Cones (Type 2B-3)** - Porous tantalum (trabecular metal) - Press-fit into defect - Biological ingrowth potential - Cement baseplate into cone - Excellent mid-term results (>95% survival at 5 years) **Metaphyseal Sleeves (Type 2B-3)** - Press-fit into proximal tibia - Integral stem connection - Metaphyseal fixation - Less reliance on diaphysis - Good for severe metaphyseal bone loss **Structural Allograft (Type 3)** - Reserved for massive defects - Femoral head or tibial plateau allograft - Risk of resorption, collapse, nonunion - 70-80% 10-year survival - Consider megaprosthesis alternative **Exam Tip:** Tantalum cones and sleeves have largely replaced structural allograft - know their advantages (consistent, no disease transmission, biological fixation). ## Extensile Exposure Options **1. Quadriceps Snip (First Line)** - 45° oblique incision from proximal VMO into quadriceps tendon - Extends exposure proximally 2-3cm - Minimal morbidity, heals reliably - Usually adequate for most revisions - Close with non-absorbable suture **2. V-Y Quadriceps Turndown (Coonse-Adams)** - Inverted V incision in quadriceps tendon - Flap turned distally over patella - Significant exposure gain - Delays rehabilitation (protected ROM 6 weeks) - Risk of extensor lag **3. Tibial Tubercle Osteotomy (TTO)** - 8-12cm length, 2cm wide, 1cm deep - From tibial tubercle extending distally - Lateral hinge preserved - Excellent exposure + patellar tendon protection - Fix with screws or cables - Increased infection risk, nonunion 2% **4. Rectus Snip (Garvin)** - Transverse incision through rectus femoris tendon - Proximal to patella - Less commonly used **Decision Algorithm:** - Stiff knee (<60° flexion): Start with lateral release + quadriceps snip - Patella avulsion risk: TTO preferred - Previous TTO: Avoid if healed well, consider V-Y **Exam Tip:** Know that TTO provides best exposure but highest morbidity. Quadriceps snip is safe first step. ### Step 1: Exposure and Arthrotomy Exposure and Arthrotomy: Use most lateral viable skin scar to reduce wound complications. Develop full-thickness fasciocutaneous flaps to allow medial and lateral mobilization. Perform medial parapatellar arthrotomy extending proximally 5-6cm above patella into quadriceps tendon. Excise hypertrophic synovium and scar tissue. Assess extensor mechanism integrity - document pre-operative extensor lag. **Technical Tip**: EXAM KEY: In stiff knees, start with lateral release of patella from gutter before attempting eversion. Document extensor lag pre-operatively. Consider quadriceps snip (45° angle from proximal VMO) if patella won't evert safely. Tibial tubercle osteotomy (TTO) is last resort - increases infection risk and requires fixation. Always preserve patellar tendon insertion - avulsion is catastrophic. - Patellar tendon avulsion during forced eversion (disaster - avoid by extensile exposure) - Fracture of attenuated patella with thin bone stock - Injury to MCL during aggressive medial dissection - Skin necrosis if previous incision not respected ### Step 2: Component Removal - Polyethylene Insert Component Removal - Polyethylene Insert: Remove polyethylene insert first using curved osteotome or dedicated extraction tools. Flex knee to 90° and deliver insert anteriorly. Inspect for backside wear, delamination, and locking mechanism failure. Document wear pattern - asymmetric wear suggests instability or malalignment. **Technical Tip**: EXAM KEY: Document wear pattern meticulously - asymmetric wear suggests instability or malalignment. Burnishing on backside suggests micromotion at locking mechanism. Send explant for analysis and wear measurement. Photograph all components for medicolegal documentation and registry reporting. Consider sending periprosthetic tissue samples for frozen section if infection suspected. - Scratching or damaging well-fixed components if planning to retain - Losing locking mechanism pieces into knee joint - Missing signs of infection (purulent fluid, soft tissue quality) ### Step 3: Assessment of Tibial Component Fixation Assessment of Tibial Component Fixation: Assess tibial baseplate stability with curved osteotome around periphery. Check for micromotion, subsidence (compare to radiographs). If loose, proceed with extraction. If well-fixed and well-positioned, may retain and only revise femoral/poly - but threshold for removal should be low in revision setting. **Technical Tip**: EXAM KEY: Indications to revise well-fixed tibial component: malalignment more than 3° varus/valgus, rotation more than 10° internal, posterior slope error more than 5°, subsidence more than 2mm, osteolysis requiring access, need for higher constraint stem. If retaining, thoroughly clean backside and check locking mechanism. Low threshold for removal - single best time to address is now. - Creating bone defects during assessment of well-fixed components - Missing fracture lines in osteopenic bone during manipulation - Underestimating extent of osteolysis behind well-fixed component ### Step 4: Tibial Baseplate Removal Tibial Baseplate Removal: Use flexible osteotomes to disrupt cement-bone interface circumferentially. Work from anterior to posterior. Use slap hammer with tibial extraction device or Gigli saws underneath baseplate. Avoid excessive force. Extract in flexion with gentle rocking motion. For well-fixed cementless components, Gigli saws safer than osteotomes. **Technical Tip**: EXAM KEY: For well-fixed cemented components, use ultrasonic cement removal (UCS) first if available - faster, safer, preserves bone. For cementless ingrown components, Gigli saws are safer than osteotomes. Windows in sclerotic bone may be needed to access cement-bone interface. Preserve bone stock - this is the critical step. Takes 15-30 minutes; do not rush. - Tibial plateau fracture propagating to articular surface or tubercle - Posterior cortical breach with vascular injury - Avulsion of MCL or patellar tendon during extraction - Fracture through osteopenic or osteolytic bone ### Step 5: Cement Removal Cement Removal: Remove all cement and fibrous membrane down to bleeding bone. Use narrow osteotomes, curettes, high-speed burr, and ultrasonic cement removal tools (Midas Rex). Work systematically from anterior to posterior. Preserve cortical shell and metaphyseal bone stock. Use pulsatile lavage after cement removal. **Technical Tip**: EXAM KEY: Complete cement removal is critical for achieving fixation and assessing true bone defects. Use headlight and loupe magnification. Cement restrictor deep in canal may need drill or flexible osteotome. Send tissue samples for culture (minimum 5 samples even in 'aseptic' revision - culture-negative PJI in 10-15%). Use vancomycin powder before closure. - Cortical perforation during aggressive cement removal - Propagating undetected fractures - Thermal injury from high-speed burr (irrigate constantly) - Posterior capsule penetration with vascular injury ### Step 6: Bone Defect Assessment (AORI Classification) Bone Defect Assessment (AORI Classification): Classify tibial defects using AORI system after ALL cement removed - cannot assess true defect with cement in situ. Type 1: Intact metaphysis. Type 2A: Damaged metaphysis with intact peripheral rim. Type 2B: Damaged metaphysis, deficient rim one condyle. Type 3: Deficient both condyles requiring major reconstruction. **Technical Tip**: EXAM KEY: Map defects with bone loss diagram documenting anteroposterior depth and mediolateral width. Measure depth from nearest intact bone surface. Uncontained (peripheral rim deficient) defects more than 5mm need structural support - cannot fill with cement alone. Contained defects less than 5mm can use cement or morsalized graft. Check for cavitary vs segmental patterns. Posterior defects are common and often underestimated - assess with finger palpation. - Underestimating defect depth leading to undersizing - Missing posterior or posteromedial defects - Misclassifying contained vs uncontained defects - Inadequate debridement before assessment ### Step 7: Canal Preparation for Stem Canal Preparation for Stem: Use flexible reamers starting 1-2mm larger than canal diameter. Ream to cortical chatter in 1mm increments. For press-fit stems, ream to exact stem diameter (line-to-line). For cemented stems, over-ream 2mm for cement mantle. Aim for 4-6cm of diaphyseal contact with short stems, 10-15cm with long stems. **Technical Tip**: EXAM KEY: Short stems (50-75mm) for AORI 1-2A provide rotational control. Long stems (100-150mm) for AORI 2B-3 bypass defect by 2 cortical diameters and achieve diaphyseal fixation. Press-fit preferred for long-term fixation (biological). Offset stems available for canal deformity. Curved stems for anterior tibial bow. Check alignment with intramedullary rod on fluoroscopy. - Anterior cortical perforation (tibial bow in sagittal plane - apex anterior) - Lateral cortical perforation (varus bowing in coronal plane) - Fracture propagation in osteopenic bone - Creating false passage in deformed or sclerotic canals ### Step 8: Proximal Tibial Preparation Proximal Tibial Preparation: Use intramedullary alignment with stem trial as reference. Set posterior slope 3-7° (match pre-operative slope if functional, increase if PCL deficient). Adjust varus/valgus to neutral mechanical axis. Resect minimum bone (typically 2-4mm more than primary to achieve flat surface on bleeding bone). **Technical Tip**: EXAM KEY: Reference off of intact plateau (usually lateral in varus knees). Goal: perpendicular to mechanical axis in coronal plane (87° to anatomical axis), 3-7° posterior slope in sagittal plane. Proximal tibial angle should be 87° (3° varus). Use intramedullary guide for alignment with extramedullary check if significant deformity. Preserve peripheral rim where possible. - Excessive resection compromising metaphyseal bone stock - Resecting into defect (losing peripheral rim support) - Saw blade penetration posteriorly injuring popliteal vessels - Creating varus or valgus malalignment affecting stability ### Step 9: Defect Reconstruction Defect Reconstruction: Based on AORI classification: Type 2A - use screws and cement or small augments (5-10mm). Type 2B - use metal augments (blocks or wedges) on deficient side, or tantalum cone. Type 3 - use large cones, metaphyseal sleeves, or structural allograft. Augments should be fully supported by host bone peripherally. Secure with screws if possible. **Technical Tip**: EXAM KEY: Metal augments: sized to fill defect, screw fixation to host bone, cement to baseplate. Tantalum cones: press-fit into defect achieving biological fixation, baseplate cemented into cone. Sleeves: bridge defect, achieve diaphyseal press-fit, baseplate cemented into sleeve. Avoid structural allograft if possible due to resorption and collapse risk. Tantalum cones now preferred with more than 95% 5-year survival. - Undersizing augments leading to subsidence - Screw penetration of posterior cortex during augment fixation - Incomplete seating of cones or sleeves - Thermal necrosis during cement polymerization on large surface area ### Step 10: Trial Reduction and Assessment Trial Reduction and Assessment: Insert tibial trial baseplate with stem and augments/cone. Insert femoral trial and appropriate polyethylene thickness. Reduce knee through full ROM. Assess: stability (no lift-off), alignment (neutral mechanical axis), patellar tracking, flexion-extension gap balance (within 2mm), ROM (target 0-120°). **Technical Tip**: EXAM KEY: Stress test in extension and 30° flexion - maximum 5mm opening with varus/valgus stress indicates adequate constraint. Check extension gap (0°) vs flexion gap (90°) - should be equal ±2mm. If extension gap tight, recut tibia or downsize femur distally. If flexion gap tight, increase posterior slope or add distal femoral augment. Assess constraint need: CCK if MCL incompetent (more than 5mm laxity), RHK/hinge if global instability. - Overstuffing joint leading to stiffness and patella baja - Accepting instability (leads to early failure) - Undersizing poly leading to accelerated wear - Missing subtle malalignment or malrotation ### Step 11: Final Implant Preparation Final Implant Preparation: Prepare bone surfaces by pulsatile lavage and dry with suction and swabs. Pack defects with antibiotic-loaded cement (if cemented) or leave clear for press-fit components. Prepare cement using high viscosity, third-generation technique. For hybrid fixation: insert press-fit stem first, then cement baseplate to stem and bone. **Technical Tip**: EXAM KEY: Third generation cementing for tibial: clean dry bone, cement gun application, pressurization, component insertion in doughy phase. For hybrid: insert press-fit stem first, then cement baseplate to stem and bone. Use antibiotic cement (1g vancomycin + 3.6g tobramycin per 40g cement) even in aseptic revision - reduces reinfection rate. Remove excess cement before polymerization. - Cement extrusion posteriorly into neurovascular structures - Air entrapment in cement creating weak spots - Early polymerization before component insertion - Inadequate cement penetration into cancellous bone ### Step 12: Tibial Component Insertion Tibial Component Insertion: Insert stem first (if press-fit hybrid), then apply cement to tibial surface and undersurface of baseplate. Insert baseplate onto stem and impact gently into position. Check rotation (aligned with medial 1/3 of tibial tubercle, approximately 18° external relative to posterior tibial cortex), AP position (centered), and complete seating. **Technical Tip**: EXAM KEY: Rotation: align tibial baseplate with femoral component in neutral flexion gap, typically 15-20° external rotation relative to posterior tibial cortex. Alternative landmark: medial border of tibial tubercle. AP position: baseplate should cover maximal tibial surface without overhang. Overhang anteriorly irritates patellar tendon, posteriorly risks neurovascular compression. Pressurize cement and remove excess. - Component malrotation (internal rotation causes medial poly wear and anterior knee pain) - Incomplete seating leaving gap under baseplate - Anterior overhang damaging patellar tendon - Posterior overhang with neurovascular compression - Cement extrusion into posterior capsule ### Step 13: Polyethylene Insert Insertion and Final Reduction Polyethylene Insert Insertion and Final Reduction: Clean and dry tibial baseplate locking mechanism meticulously. Insert polyethylene insert ensuring proper locking - audible click and visual confirmation. Test that poly cannot be removed with traction. Reduce knee and assess final stability, ROM, patellar tracking. Document final construct. **Technical Tip**: EXAM KEY: Poly thickness selection: should provide stability without overstuffing. Minimum 10mm for PS, 12-15mm for CCK (taller post), 15-20mm for hinges. Final assessment: no varus/valgus laxity more than 5mm at 0° or 30°, no AP laxity more than 5mm at 90°. ROM: target 0-120°, minimum 0-110°. Patellar tracking: should track centrally without subluxation or tilt. Lateral release if persistent lateral subluxation. - Poly insert not fully locked (dislocation, wear, failure) - Overstuffing causing limited flexion and patellofemoral problems - Accepting instability requiring early re-revision - Missing patellar maltracking requiring lateral release ### Step 14: Final Assessment and Closure Final Assessment and Closure: Perform final check: ROM 0-120°, stable through arc, patellar tracking central, no impingement. Remove all loose cement, bone fragments, debris with thorough lavage (6-9L). Meticulous hemostasis. Insert deep drain. Close capsule and extensor mechanism in flexion with interrupted figure-of-8 sutures (No.2 Ethibond). Close subcutaneous layers and skin. **Technical Tip**: EXAM KEY: Tranexamic acid: 1g IV at induction, 1g at closure reduces blood loss by 40%. Drain for 24-48h in revisions due to dead space. Close arthrotomy with interrupted figure-of-8 to prevent disruption. Test closure by extending knee fully - should hold without tension. Apply compression dressing. Extended knee brace for 24h to protect extensor mechanism if TTO performed. - Retained cement or debris causing third-body wear - Inadequate hemostasis causing hematoma and infection risk - Wound closure under tension risking dehiscence - Damage to extensor mechanism during closure ### Step 15: Post-Operative Protocol and Follow-Up Post-Operative Protocol and Follow-Up: Elevate leg, apply ice. TED stockings and prophylactic anticoagulation (apixaban 2.5mg BD or enoxaparin 40mg daily) for 35 days per Australian guidelines. IV antibiotics 24-48h. Immediate quadriceps isometrics. Mobilize day 1 with physiotherapy - WBAT with frame for cemented/hybrid, protected weight-bearing for press-fit. CPM if available. Drain removal 24-48h. **Technical Tip**: EXAM KEY: Post-op radiographs: AP, lateral, skyline views. Check mechanical alignment through knee center, component position, no fractures. Flexion to 90° by week 2, full extension immediately. Outpatient review 2 weeks (wound), 6 weeks (ROM, function, radiographs), 3 months, 1 year, then annually. Monitor for infection: CRP peaks day 2-3, should normalize by 3-4 weeks; ESR peaks week 1, normalizes by 6-8 weeks. Persistent elevation warrants investigation. - Wound dehiscence (especially with TTO or extensile exposure) - Deep infection (5-10% in revision TKR vs 1-2% primary) - Extensor mechanism failure or rupture - Periprosthetic fracture during early mobilization - DVT/PE (higher risk in revision surgery - 35 day prophylaxis mandatory) **Immediate (Days 0-3):** - Leg elevation, ice therapy, compression dressing - IV antibiotics continued 24-48h - DVT prophylaxis (apixaban 2.5mg BD for 35 days or LMWH) - Drain removal at 24-48h when output less than 50mL/8h - Quadriceps isometrics, ankle pumps, SLR if able - Mobilize day 1 with frame - WBAT for cemented/hybrid **Early (Weeks 1-6):** - Wound check at 2 weeks, suture removal - Radiographs at 6 weeks - Progressive ROM - goal 90° by 2 weeks, 120° by 6 weeks - Transition to single crutch/cane by 4-6 weeks - Outpatient physiotherapy for ROM and strengthening **Intermediate (Weeks 6-12):** - Full weight-bearing without aids - Stairs, transfers, functional activities - Driving at 6-8 weeks (automatic, left knee) or 8-12 weeks (right knee) - Return to sedentary work 6-8 weeks, manual work 12+ weeks **Long-term:** - Annual review with radiographs - Lifelong antibiotic prophylaxis for dental/invasive procedures - Report any concerning symptoms (pain, swelling, drainage) promptly - Activity modification - avoid high-impact sports ## References 1. Anderson Orthopaedic Research Institute. AORI Bone Defect Classification for Revision Total Knee Arthroplasty. J Arthroplasty 1997. 2. Australian Orthopaedic Association National Joint Replacement Registry. Annual Report 2024. Hip, Knee & Shoulder Arthroplasty. 3. Vince KG, Abdeen A, Sugimori T. The unstable total knee arthroplasty: causes and cures. J Arthroplasty 2006;21(4 Suppl 1):44-49. 4. Engh GA, Ammeen DJ. Bone loss with revision total knee arthroplasty: defect classification and alternatives for reconstruction. Instr Course Lect 1999;48:167-175. 5. Parvizi J, Gehrke T, Chen AF. Proceedings of the International Consensus on Periprosthetic Joint Infection. Bone Joint J 2013;95-B(11):1450-1452. 6. Meneghini RM, Lewallen DG, Hanssen AD. Use of porous tantalum metaphyseal cones for severe tibial bone loss during revision total knee replacement. J Bone Joint Surg Am 2008;90(1):78-84. 7. 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. 8. Morgan-Jones R, Oussedik SI, Graichen H, Haddad FS. Zonal fixation in revision total knee arthroplasty. Bone Joint J 2015;97-B(2):147-149. 9. Australian Commission on Safety and Quality in Healthcare. Clinical Care Standard: VTE Prevention. 2020. 10. Della Valle CJ, Berger RA, Rosenberg AG. Surgical exposures in revision total knee arthroplasty. Clin Orthop Relat Res 2006;446:59-68.

Revision Total Knee Replacement - Tibial Component

Revision Total Knee Replacement - Tibial Component