import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Posterior to knee joint 1-2cm**. At risk during posterior capsule debridement and cement removal. STAY ON BONE during posterior work. Cement extrusion posteriorly can lacerate vessels - monitor during polymerization. **Wraps around fibular neck laterally**. At risk with lateral dissection, retraction, leg lengthening. Post-op palsy = foot drop. Avoid excessive lateral exposure below joint line. **Patella, patellar tendon, quadriceps**. Disruption = functional disaster. Avoid forced eversion - use TTO if needed. Maintain patellar thickness >10mm for stage 2. Protect from burr heat. **Essential for knee stability**. Preserve during synovectomy. Injury = spacer instability. If disrupted, consider static spacer or hinged brace. Test stability before closure. ### Definite Indications - **Chronic PJI** (>4 weeks symptoms) confirmed by MSIS criteria - **Failed DAIR** for acute PJI - **Difficult organisms**: MRSA, resistant Gram-negatives, fungi, mycobacteria - **Culture-negative PJI** - two-stage safest approach when organism unknown - **Significant bone loss** requiring staged reconstruction ### Consider One-Stage Instead - Known sensitive organism pre-operatively - Healthy soft tissue envelope - Good bone stock - Non-immunocompromised patient - Experienced high-volume centre (strict protocols) ### DAIR May Be Appropriate If - Acute infection (<3-4 weeks symptoms or <6 weeks post-op) - Stable, well-fixed implants - Healthy patient - Known sensitive organism - Intact soft tissues ### Infection Workup - **Aspiration** (off antibiotics 2+ weeks): - Cell count: WBC >3000, PMN% >80% supports PJI - Gram stain, culture (aerobic, anaerobic, fungal, AFB) - Alpha-defensin (97% sensitive/specific for knee PJI) - Crystal analysis (rule out gout) - **Serum markers**: ESR >30, CRP >10 supports PJI - **Imaging**: X-ray (loosening), CT (bone loss), nuclear scan if uncertain ### Exposure Planning - CRITICAL - Assess **patellar height** (patella baja = TTO needed) - Assess **knee flexion** (stiff knee = extensile approach) - Plan **exposure strategy**: - Standard medial parapatellar (most cases) - TTO if patella baja, severe scarring, stiff knee - Quadriceps snip or V-Y turndown if inadequate exposure ### Medical Optimization - **Nutrition**: Albumin >3.0, transferrin >200, lymphocytes >1500 - **Diabetes**: HbA1c <8% - **Smoking cessation**: Ideally 4+ weeks pre-op - **Anticoagulation**: Cease appropriately ### Surgical Planning - **Component identification**: Know manufacturer, size, have extraction equipment - **Blood availability**: Cross-match 2-4 units - **NO TOURNIQUET**: Increases bacteremia, compromises antibiotic delivery ### Procedure-Specific Risks - **Persistent infection** (10-25%) - may need repeat procedures - **Spacer dislocation/instability** (10-20%) - **Extensor mechanism disruption** (3-8%) - devastating complication - **Stiffness** (10-20%) - may be permanent - **Wound complications** (5-15%) - **Vascular injury** (<1%) - rare but catastrophic - **Need for arthrodesis or amputation** (5-10% of two-stage cases) ### Realistic Expectations - Stage 1 = temporizing procedure, NOT definitive - 8-12 weeks with spacer in situ - Protected weight bearing with frame/crutches - Hinged knee brace for stability - Daily ROM exercises critical (90-120° goal) - IV antibiotics for 6 weeks (PICC line) - Final ROM often less than primary TKA ### Alternative Treatments Discussed - DAIR (if acute, stable implants, sensitive organism) - One-stage revision (strict criteria rarely met) - Chronic suppressive antibiotics (palliation) - Knee arthrodesis (stable but severe limitation) - Above-knee amputation (refractory sepsis, severe bone loss) ### Spacer Materials - **Antibiotic cement**: 2-3 × 40g packs (80-120g total) - **Vancomycin powder**: 6-8g (Gram-positive, MRSA coverage) - **Tobramycin powder**: 4.8g or Gentamicin 4g (Gram-negative, biofilm) - **Commercial spacer moulds**: Prostalac, Spacer-K, or femoral/tibial moulds - **Reinforcement**: Steinmann pins if hand-moulding ### Extraction Equipment - **Universal extraction set**: Curved osteotomes, slap hammers - **High-speed burr**: For cement removal - **Oscillating saw**: For TTO if needed - **Screw/post extractors**: For constrained or stemmed components ### Exposure Equipment - **TTO set**: Oscillating saw, drill, screws/cables for fixation - **Retractors**: Hohmann, Army-Navy, lamina spreaders - **Self-retaining retractor**: Restore visibility in deep wound ### General Equipment - **Pulsatile lavage**: 9L minimum - **Tissue sampling supplies**: 5+ sterile containers - **Drains**: 2 deep drains - **Hinged knee brace**: For post-operative stability ### Step 1: Anaesthesia and Positioning - NO TOURNIQUET **CRITICAL**: Do NOT use tourniquet in infected knee. - Tourniquet increases bacteremia during manipulation - Compromises local tissue antibiotic delivery - Accept higher blood loss (have blood available) **Position**: Supine with bump under ipsilateral hip. - Foot of bed flexed to allow knee flexion - Thigh support for stability - All bony prominences padded **FRCS KEY**: NO TOURNIQUET in infected knee. Examiners will test this. Tourniquet increases systemic bacteremia and reduces antibiotic penetration to infected tissue. ### Step 2: Intraoperative Tissue Sampling (BEFORE Antibiotics) **HOLD prophylactic antibiotics** until 5+ tissue samples obtained. Take **minimum 5 separate tissue samples** from: 1. Suprapatellar pouch/synovium 2. Medial gutter synovium 3. Lateral gutter synovium 4. Interface tissue around tibial component 5. Interface tissue around femoral component 6. Any obvious purulent collections Each sample in **separate sterile container**. Send for aerobic, anaerobic, fungal, AFB with prolonged 14-day culture. NOW give antibiotics. ### Step 3: Incision and Exposure **Use previous incision** (most common: midline or medial parapatellar). **Medial Parapatellar Arthrotomy** (standard): - Incise 3cm above superior pole of patella - Curve around medial patella, 1cm from tendon - Extend distally to tibial tubercle - Careful dissection through scar tissue **Decision point**: Can patella evert and flex knee without excessive tension? - **YES**: Proceed with exposure - **NO**: Proceed to Tibial Tubercle Osteotomy NEVER force patellar eversion against resistance. Patella fracture, patellar tendon avulsion, or quadriceps rupture will occur. Use TTO for difficult exposure. ### Step 4: Tibial Tubercle Osteotomy (TTO) - If Required **Indications**: - Patella baja (patella-tendon ratio <0.8) - Severe scarring preventing eversion - Stiff knee (<70° flexion) - Previous quad snip or V-Y turndown **Technique**: 1. Mark osteotomy: 6-8cm long, 1cm wide, start at patellar tendon insertion 2. Use oscillating saw for medial and distal cuts 3. Lateral cut: osteotome to create hinge (protects lateral periosteum) 4. Elevate tubercle fragment with attached patellar tendon 5. Patella can now flip laterally without tension 6. At closure: Fix with screws (bicortical) or cables **FRCS KEY**: TTO protects extensor mechanism, allows excellent exposure, and heals reliably (95%+) when fixed with screws. Far better than forced eversion or muscle-damaging approaches. ### Step 5: Radical Synovectomy and Debridement **Remove ALL infected tissue** - this is the single most important step. **Synovectomy**: - Complete excision of synovium from suprapatellar pouch to posterior capsule - Debride gutters medially and laterally - Remove all granulation tissue **Debridement**: - Excise necrotic tissue to healthy bleeding margins - Debride bone surfaces to fresh bleeding bone - Remove all foreign material (sutures, cement debris) - Preserve MCL and LCL attachments ### Step 6: Tibial Component Removal **Cemented tibial tray**: - Identify cement-bone interface - Use curved osteotomes to disrupt interface - Thin flexible osteotomes for underneath tray - Remove tray, then meticulously remove ALL cement - High-speed burr for retained cement **Cementless tibial tray**: - Curved osteotomes around periphery - Disrupt bone ingrowth progressively - Avoid aggressive levering (fracture risk) **Remove polyethylene insert** and **tibial stem** if modular. ### Step 7: Femoral Component Removal **Cemented femoral component**: - Use thin osteotomes at cement-bone interface - Start anteriorly, work posteriorly - Curved osteotomes for posterior condyles - Remove ALL cement (critical for infection eradication) **Cementless femoral component**: - Disruption osteotomes around periphery - Specialized extraction equipment may be needed - Protect posterior cortex (avoid notching) Cement behind posterior condyles is difficult to remove but MUST be removed. Residual cement harbors bacteria. Use curved curettes, burrs, and visualization. Protect popliteal vessels. ### Step 8: Complete Cement Removal **Remove ALL cement** - any residual cement = potential treatment failure. - High-speed burr for adherent cement - Long curettes for intramedullary cement - Thin flexible osteotomes - Direct visualization from all angles Debride canal to **healthy bleeding bone**: - Sequential reaming if needed - Remove all interface membrane ### Step 9: Copious Pulsatile Lavage **Minimum 9 litres** pulsatile lavage: - 3-6L during debridement - 3L final lavage before spacer insertion - Ensure lavage reaches all recesses (posterior capsule, gutters) **FRCS KEY**: "Dilution is the solution to pollution." High-volume pulsatile lavage mechanically removes bacteria and debris. Essential complement to debridement. ### Step 10: Antibiotic Cement Spacer Fabrication **Standard Knee Formulation** (80g cement): - **80g cement** (2 × 40g) - Palacos preferred for elution - **Vancomycin 6-8g** (Gram-positive, MRSA) - **Tobramycin 4.8g** OR Gentamicin 4g (Gram-negative, biofilm) - Maximum 10% antibiotic by weight **Mixing Technique**: 1. Combine antibiotic powders with cement powder FIRST 2. Mix thoroughly for homogeneous distribution 3. Add liquid monomer 4. Mix to doughy consistency 5. Mould into spacer components **Spacer Types**: - **Commercial articulating** (Prostalac, Spacer-K): Standardized, reliable - **Hand-moulded**: Higher antibiotic dose possible, custom sizing - **Static**: ONLY if MCL/LCL disrupted, massive bone loss, or extreme instability ### Step 11: Tibial Spacer Component Insertion **Technique**: - Size to match tibial plateau dimensions - Create flat articular surface for stability - Insert in doughy phase - Cement interdigitates with cancellous bone for stability - Remove excess cement before polymerization **If hand-moulding**: - Flatten posterior aspect for rotation control - Create slight posterior slope (3-5°) - May reinforce with Steinmann pin if large ### Step 12: Femoral Spacer Component Insertion **Commercial systems**: Follow manufacturer technique. **Hand-moulded technique**: - Form femoral condyle shape - Ensure adequate anterior flange (for patella tracking) - Size to match native femur - Insert in doughy phase - Check alignment in extension and flexion ### Step 13: Stability and ROM Assessment **Test stability**: - Varus/valgus stress in extension and 30° flexion - Check for laxity or dislocation tendency **Test range of motion**: - Goal: 0-90° minimum, ideally 0-120° - Check patella tracking - Assess for impingement **If unstable**: - Thicker spacer construct - Hinged knee brace post-operatively - Consider static spacer if grossly unstable (MCL/LCL deficient) **FRCS KEY**: Articulating spacer allows 90-120° ROM. This prevents stiffness, allows patient mobilization, and makes stage 2 exposure dramatically easier. Static spacer = often permanent stiffness. ### Step 14: TTO Fixation (If Performed) If TTO was performed, fix at closure: - **Screw fixation** (preferred): 2-3 bicortical screws (4.5mm) - **Cable fixation**: 2 cerclage cables - Ensure secure fixation - TTO non-union is rare but problematic ### Step 15: Wound Closure **Layered closure**: - Deep drains (2 minimum) - Capsule/retinaculum - strong absorbable suture - Subcutaneous - absorbable suture - Skin - staples or absorbable subcuticular **Critical**: Tension-free closure. Skin necrosis = exposed spacer = treatment failure. ### Step 16: Post-operative Immobilization - **Hinged knee brace**: Set for ROM 0-90° initially - Prevents hyperextension - Provides stability during mobilization - Gradually increase ROM as tolerated ### Immediate Post-operative - **Weight bearing**: Protected with frame/crutches - **DVT prophylaxis**: LMWH or aspirin per protocol - **Drains**: Remove when <50mL/24hrs - **IV antibiotics**: Start post-operatively based on cultures ### Rehabilitation During Spacer Period - **ROM exercises**: Start POD#1 - critical to prevent stiffness - **Goal**: 90-120° flexion, full extension - **Physiotherapy**: Daily exercises, CPM if available - **Hinged brace**: Worn during mobilization ### Antibiotic Protocol - **Duration**: 6 weeks IV antibiotics minimum - **PICC line**: Insert before discharge - **OPAT**: Outpatient parenteral antibiotic therapy - **Organism-specific**: Adjust when sensitivities available - **ID consultation**: Essential for complex organisms ### Monitoring - **Weekly bloods**: CRP, ESR (expect initial rise then normalization) - **Clinical assessment**: Wound, ROM, pain, systemic symptoms - **Watch for**: Spacer dislocation, wound dehiscence, stiffness ### Criteria for Stage 2 (EXAM ESSENTIAL) 1. **6 weeks IV antibiotics** completed 2. **2-6 week antibiotic holiday** 3. **Normalized markers**: CRP <10, ESR <30 for 2+ consecutive weeks 4. **Knee aspiration during holiday**: WBC <3000, PMN <80%, negative culture 5. **Healed wound**, no drainage 6. **Patient medically optimized** **FRCS KEY**: Do NOT rush to stage 2. Interval typically 8-12 weeks. Knee aspiration during antibiotic holiday only 50% sensitive - clinical judgment and markers equally important. ## References 1. Parvizi J, 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. 2. Deirmengian C, et al. Diagnosing periprosthetic joint infection: has the era of the biomarker arrived? Clin Orthop Relat Res. 2014;472(11):3254-3262. 3. Hofmann AA, et al. Two-stage reimplantation for infected total knee replacement. Knee. 2005;12(1):9-18. 4. Fehring TK, et al. Articulating versus static spacers in revision total knee arthroplasty for sepsis. Clin Orthop Relat Res. 2000;(380):9-16. 5. Freeman MG, et al. Articulating antibiotic spacers in two-stage exchange for prosthetic knee infection. Clin Orthop Relat Res. 2007;464:65-72. 6. Emerson RH, et al. Comparison of a static with a mobile spacer in total knee infection. Clin Orthop Relat Res. 2002;(404):132-138. 7. Whiteside LA. Exposure in difficult total knee arthroplasty using tibial tubercle osteotomy. Clin Orthop Relat Res. 1995;(321):32-35. 8. Osmon DR, et al. Diagnosis and management of prosthetic joint infection: clinical practice guidelines by IDSA. Clin Infect Dis. 2013;56(1):e1-e25. 9. Kurtz SM, et al. Economic burden of periprosthetic joint infection in the United States. J Arthroplasty. 2012;27(8 Suppl):61-65. 10. Diaz-Ledezma C, et al. Revision total knee arthroplasty for periprosthetic joint infection: the positive predictive value of the preoperative workup. J Arthroplasty. 2014;29(9):1802-1806.

Two-Stage Revision TKA - Stage 1: Antibiotic Cement Spacer Insertion

Two-Stage Revision TKA - Stage 1: Antibiotic Cement Spacer Insertion