# THR Revision - Femoral Bone Loss ## Clinical Scenario A 65-year-old female with type 2 diabetes and obesity presents with increasing right hip pain 5 years after cemented THR. She has start-up pain and thigh pain. X-rays show a loose femoral stem with significant metaphyseal bone loss. ESR and CRP are normal. ## Questions & Model Answers Paprosky classification for femoral bone loss: Type I - Minimal metaphyseal cancellous bone loss, intact diaphysis. Type II - Extensive metaphyseal bone loss, intact diaphysis (>4cm scratch fit achievable). Type IIIA - Metaphysis unsupportive, >4cm intact diaphysis available. Type IIIB - Metaphysis unsupportive, <4cm intact diaphysis. Type IV - Extensive metaphyseal and diaphyseal bone loss, widened canal, no isthmus. This patient appears to have Type II or IIIA based on significant metaphyseal loss but likely intact diaphysis. Intraoperative assessment will confirm. The Valley View classification and AAOS/Della Valle system are alternatives. **Key Points:** - Paprosky guides reconstruction strategy - Diaphyseal bone quality is key - Intraoperative assessment essential - >4cm diaphyseal scratch fit = Type IIIA Reconstruction based on Paprosky type: Type I - Cemented or standard cementless stem. Type II - Extensively porous-coated stem (e.g., Solution, AML) with diaphyseal fixation, or proximal-fit cementless if metaphyseal bone adequate. Type IIIA - Extensively porous-coated diaphyseal-fit stem, tapered fluted stems (e.g., Wagner), modular stems. Type IIIB - Modular tapered fluted stem with distal fixation and proximal modular body, impaction bone grafting in younger patients. Type IV - Proximal femoral replacement megaprosthesis, or impaction grafting with structural allograft for younger patients. For this patient (likely Type II-IIIA): extensively porous-coated or modular tapered stem, consider strut allograft for cortical defects. **Key Points:** - Extensively porous-coated for diaphyseal fixation - Modular stems allow intraoperative adjustment - Impaction grafting restores bone stock - Proximal femoral replacement for severe loss Intraoperative femoral fracture management: 1) Immediate recognition and classification - Vancouver B2 most likely (fracture around loose stem), 2) Extend approach - may need extended trochanteric osteotomy (ETO) if not already performed, 3) Remove remaining cement and loose components, 4) Fracture fixation options: cable/wire cerclage, cortical strut allograft, plate fixation, 5) Revision stem selection - long stem bypassing fracture by 2 cortical diameters (minimum 4-5cm), diaphyseal-engaging stem preferred, 6) Consider extensively porous-coated stem if good distal bone, or modular fluted tapered stem. Protected weight-bearing postoperatively. The combination of strut allograft + cables + long stem provides fracture fixation and biological enhancement. **Key Points:** - Extended trochanteric osteotomy may help exposure - Bypass fracture by 2 cortical diameters - Strut allograft + cables effective fixation - Protected weight-bearing essential Infection workup before revision: Mandatory investigations: 1) Inflammatory markers - ESR, CRP (should be normal; elevated values highly suspicious), 2) Joint aspiration - synovial WCC (>3000 cells/μL concerning), neutrophil percentage (>80% concerning), culture and sensitivity (hold antibiotics for 2 weeks prior), 3) Blood cultures if systemically unwell. Additional tests: 1) Alpha-defensin - highly specific synovial marker for PJI, 2) Synovial fluid D-dimer and leukocyte esterase, 3) Nuclear medicine - labelled WBC scan if diagnosis unclear. MSIS criteria (2018 modified): Major criteria (one sufficient): Two positive cultures with same organism, OR sinus tract communicating with joint. Minor criteria (score ≥6 = infection): Elevated serum CRP >1mg/dL (2 pts), Elevated ESR >30mm/hr (1 pt), Elevated synovial WCC (3 pts), Elevated synovial PMN% (2 pts), Positive alpha-defensin (3 pts), Single positive culture (2 pts). This patient has normal ESR/CRP - would proceed with aspiration to confirm sterile before revision. **Key Points:** - ESR/CRP normal = low probability, but still aspirate - Synovial WCC >3000 and PMN >80% concerning - Alpha-defensin highly specific for PJI - Two-stage revision if infection confirmed Extended trochanteric osteotomy (ETO): Indications: 1) Removal of well-fixed cementless stem, 2) Removal of cemented stem with extensive cement mantle, 3) Periprosthetic fracture with retained stem (facilitates removal), 4) Need for improved exposure (stiff hip, severe bone loss), 5) Correction of malrotation. Technique: 1) Length - typically 12-15cm, extend distally from tip of greater trochanter, 2) Width - one-third circumference of femur (posterolateral to anterolateral), 3) Osteotome or oscillating saw for cuts, 4) Protect soft tissue attachment to fragment (abductors, vastus lateralis), 5) Hinge fragment anteriorly for access, 6) Cement removal under direct vision, 7) Repair with cables/wires (minimum 2-3 cerclage). Outcomes: Union rate 90-95% if adequate fixation and protected weight-bearing. Complications: Non-union (5-10%), trochanteric migration, cable/wire breakage, thigh pain from prominence. Postop: Protected weight-bearing 6-12 weeks until healing. **Key Points:** - One-third circumference, 12-15cm length - Preserve soft tissue attachments - Cable fixation for repair - 90-95% union with protected weight-bearing Outcomes of revision THA for aseptic loosening: Function: WOMAC/OHS improvement 60-70% of primary THA improvement, Harris Hip Score improvement from ~45 to ~75 points. Survivorship: 10-year implant survival 85-90% for acetabular revision, 80-85% for femoral revision, lower for complex reconstructions (Paprosky III-IV). Complications: 1) Intraoperative - femoral fracture (5-15%), nerve injury (1-3%), vascular injury (rare but catastrophic), 2) Early postoperative - dislocation (5-15%, higher than primary), wound complications (5%), VTE, 3) Late - re-loosening (10-15% at 10 years), re-infection (2-5%), periprosthetic fracture, leg length discrepancy. Mortality: 90-day mortality 1-2% (higher than primary THA). Factors affecting outcome: 1) Paprosky classification - higher grade = worse outcome, 2) Age - younger patients may need re-revision, 3) Surgeon volume - high-volume centres better outcomes, 4) Bone stock restoration - impaction grafting may restore bone for future revisions. For this patient: counsel regarding expectations - good pain relief expected but higher complication rate than primary. **Key Points:** - 10-year survival 80-90% - Dislocation rate higher than primary (5-15%) - Intraoperative fracture 5-15% - High-volume centres have better outcomes ## Exam Tips **Opening Statement:** This patient has a failed cemented THR with femoral bone loss. After excluding infection with normal inflammatory markers and aspiration, I would plan revision with a reconstruction strategy based on Paprosky classification. **Common Pitfalls:** - Always exclude infection before revision - Preoperative templating but prepare for intraoperative surprises - Intraoperative fracture must be managed definitively