import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Location**: Exits pelvis through greater sciatic notch inferior to piriformis, runs 2cm posterior to posterior capsule and short external rotators, courses along posterior aspect of hip joint descending toward posterior thigh. **Protection**: Early identification and vessel loop placement, gentle retraction, avoid excessive leg lengthening (>2cm increases palsy risk exponentially), minimize traction time. Revision for dislocation has highest sciatic nerve palsy risk (2-7%) of all hip revisions due to scar tissue and exposure needs. **Location**: Exits pelvis above piriformis through greater sciatic notch, enters undersurface of gluteus medius 3-5cm superior to tip of greater trochanter, provides motor innervation to gluteus medius and minimus (hip abductors). **Protection**: Limit proximal dissection to less than 5cm above GT, avoid placing retractors in superior capsular region, identify and preserve if extended trochanteric osteotomy performed. Injury causes permanent Trendelenburg gait. **Location**: Lies anterior to hip joint capsule in femoral triangle - nerve most lateral, then femoral artery, then femoral vein (NAV from lateral to medial). Courses 2-3cm anterior to anterior hip capsule. **Protection**: Relevant if anterior approach used or anterior capsule released, avoid vigorous anterior retraction, identify and protect during acetabular exposure and screw placement (avoid anteroinferior quadrant screws). Rarely at risk in posterior approach but consider during trialing. **Location**: Exits pelvis through obturator foramen on medial wall of acetabulum, runs in obturator canal giving branches to hip adductors and medial thigh skin, lies 1-2cm medial to quadrilateral plate. **Protection**: Avoid medial acetabular wall perforation during reaming, avoid medial or anteroinferior screw placement, recognize quadrilateral plate as medial boundary during cup reaming. Injury causes adductor weakness and medial thigh numbness. **Location**: Posterior column and wall of acetabulum, often compromised in chronic posterior dislocators due to repeated trauma and stress. Typically thin and fragile in revision setting, especially posterosuperior quadrant. **Protection**: Gentle reaming with hand pressure, avoid power reaming posteriorly, assess wall integrity before and during cup insertion, consider protected weight bearing if wall deficient, use screws in safe posterosuperior zone for supplemental fixation. Fracture rate 1-2% in revision for instability. ## Primary Indications **Absolute Indications:** - Recurrent dislocation (≥2 episodes) after primary THR despite closed reduction and rehabilitation - Chronic instability affecting quality of life and activities of daily living - Failed conservative management (bracing, activity modification, physiotherapy) - Identifiable correctable cause (component malposition, soft tissue deficiency) **Relative Indications:** - Single dislocation with identifiable mechanical cause (malpositioned components) - Persistent subluxation episodes causing pain and apprehension - Patient request after single traumatic dislocation in context of high-risk activities **Contraindications:** - Active infection (must stage with explant and spacer first) - Medical comorbidities precluding major revision surgery - Severe abductor deficiency with no reconstruction option (consider expectant management) - Neuromuscular disorder causing instability (Parkinson's, seizures) - surgery may not solve problem - Patient non-compliance with post-operative precautions (relative contraindication) ## Preoperative Assessment **History:** - Number of dislocations, direction (posterior 80%, anterior 15%, superior 5%) - Provocative activities (bending, sitting low chairs, specific movements) - Timing (early <6 weeks vs late >6 weeks post-primary) - Previous closed reductions, attempts at conservative management - Impact on quality of life, activities of daily living **Clinical Examination:** - Trendelenburg test (abductor integrity) - Hip range of motion, stability testing - Leg length assessment - Neurovascular status (baseline documentation) - Gait assessment **Imaging:** - **AP pelvis**: Measure cup inclination (normal 40-45°, >50° = superior escape, <35° = instability) - **Lateral hip or cross-table lateral**: Assess anteversion (15-25° normal) - **CT with 3D reconstruction**: ESSENTIAL for precise cup version measurement, stem version, impingement assessment - **Consider MRI**: Abductor integrity, fatty infiltration, capsular deficiency **Laboratory Investigation:** - **MANDATORY infection workup**: ESR, CRP, joint aspiration - **Aspiration**: Cell count (>3000 concerning), differential (>80% PMNs concerning), 14-day culture, alpha-defensin or synovial CRP/IL-6 - Cannot proceed without ruling out infection **Component Assessment:** - Cup position (in/out of Lewinnek safe zone) - Cup type, liner wear pattern - Stem version, offset restoration - Head size (small heads <32mm higher risk) - Impingement signs (eccentric wear) **Reconstruction Planning:** - Decision: Component repositioning alone? Dual mobility? Constrained liner? - Soft tissue reconstruction needs (abductor repair, capsule reconstruction) - Implant ordering (dual mobility system or constrained liner, backups) ## Patient Positioning **Lateral Decubitus (Posterior Approach):** - Affected side up on radiolucent table - Pelvic stabilization with supports (anterior ASIS, posterior sacrum) - All bony prominences padded - Careful positioning to prevent pressure injuries - Cell saver recommended (blood loss typically 400-800mL) **Approach Selection:** - Use **previous surgical approach** when possible (minimize soft tissue trauma) - Posterior approach most common (80% of Australian primary THRs) - Extended exposure often needed for component assessment ## Exposure Technique **Incision:** - Use previous incision, excise old scar elliptically - Extend proximally and distally as needed (typically 15-20cm) - Multiple previous scars: choose most posterior **Deep Dissection:** - Deepen through scarred subcutaneous tissue - Incise fascia lata in line with previous surgery - Split gluteus maximus in line with fibers (often scarred, difficult planes) - **CRITICAL**: Identify and protect sciatic nerve EARLY - Higher risk due to scar encasement - Place vessel loop or protected retractor - Nerve palsy risk 2-7% (highest of all revision types) **Capsular Assessment:** - Tag any capsule present for repair - Often deficient or absent in chronic dislocators - Note deficiency for reconstruction planning - Assess abductor attachment and quality at greater trochanter ## Component Assessment **Dislocation:** - May be easy (chronically unstable) or difficult (scar tissue) - Gentle maneuvers: flex 90°, adduct, internally rotate - Bone hook on femoral neck if needed - Avoid excessive force (fracture risk) **Systematic Assessment:** 1. **Cup position**: Inclination, version (Lewinnek safe zone 40±10° inclination, 15±10° anteversion) 2. **Cup fixation**: Well-fixed or loose 3. **Liner wear**: Eccentric wear, scratching (impingement signs) 4. **Stem**: Version, stability, offset restoration 5. **Head size**: Small <32mm = higher risk 6. **Impingement**: Wear on femoral neck 7. **Soft tissues**: Abductor quality, capsule integrity ## Component Removal (If Indicated) **Acetabular Cup:** - Remove if malpositioned or converting to dual mobility/constrained - **Well-fixed cup**: Curved osteotomes circumferentially, stay on metal, preserve bone - Specialized extraction tools if needed - Goal: Minimize bone loss **Femoral Stem:** - Usually NOT removed for instability alone unless: - Malaligned (excessive version) - Loose - Wrong offset - Well-fixed cementless: May need Extended Trochanteric Osteotomy - Cemented: Remove cement with high-speed burr, ultrasonic tools **Head Exchange:** - Often simple head size change (28mm → 36mm) - Keeps well-fixed stem in place ## Acetabular Reconstruction - Dual Mobility (Preferred) **Preparation:** - Remove scar tissue to bleeding bone - Assess bone stock (Paprosky classification) - Ream to appropriate size (dual mobility needs larger component) - Medialize to anatomic hip center when possible **Cup Positioning (CRITICAL):** - **Still must be in Lewinnek safe zone** - Target: 40-45° inclination, 15-20° anteversion - Use guide or fluoroscopy for accurate placement - Combined anteversion: Cup + Stem = 35-50° **Cup Insertion:** - Press fit (1-2mm larger than final reamer) - Check stability (should not move) - Add screws in SAFE ZONES if questionable stability - Posterosuperior quadrant safest - Avoid: anteroinferior (vessels), medial (intrapelvic), inferior (obturator nerve) **Liner Insertion:** - System-specific (snap or screw mechanism) - Insert small inner bearing into large outer bearing - Verify smooth articulation ## Acetabular Reconstruction - Constrained Liner (Alternative) **Indications:** - Dual mobility not available - Prior dual mobility failure - Severe abductor deficiency - Severe bone loss preventing dual mobility **Technique:** - Ream acetabulum to appropriate size - Insert specific constrained cup system - Position in safe zone (EVEN MORE CRITICAL) - **Screw fixation MANDATORY** (high torque) - Insert constrained liner - Insert and LOCK femoral head (verify locking) - Check ROM (constrained reduces ROM) **Disadvantages:** - Higher loosening (5-15% at 5 years) due to torque - Liner dissociation risk (3-8%) - Reduced ROM - Higher wear (thicker polyethylene) ## Femoral-Sided Optimization **Assessment:** - Stem version (excessive anteversion >25° or retroversion <5°) - Offset restoration (compare to contralateral) - Stem stability (loose requires revision) - Modularity options (adjust with modular head/neck) **Head Size Change:** - Larger heads reduce dislocation (32mm → 36mm or 40mm) - 36mm has ~50% lower dislocation than 28mm - Limited by cup inner diameter - Appropriate size for dual mobility system (28-32mm inner) **Stem Revision (If Needed):** - Excessive anteversion/retroversion: Revise to neutral (10-15°) - Wrong offset: Higher offset stem - Loose: Revise regardless - Combined anteversion rule: Cup + Stem = 35-50° ## Trial Reduction and Stability Testing **Comprehensive Testing (CRITICAL):** 1. **Posterior stability** (most common): 90° flexion + maximal adduction + maximal IR = shuck test (should be ROCK SOLID) 2. **Anterior stability**: Full extension + 40° ER + slight adduction 3. **Superior escape**: Full abduction + ER (rare) 4. **Full ROM testing**: Flex 110-120°, extend neutral, abduct 45°, adduct to midline, rotations 5. **Impingement assessment**: Look/feel for prosthetic impingement at extremes 6. **Soft tissue tension**: Snug but not excessively tight (nerve palsy risk) 7. **Leg length**: Overlapping patellae, ASIS to medial malleolus, compare to templating (aim <1cm difference) 8. **Fluoroscopy**: Visualize head centering, no subluxation **If unstable**: Must address before proceeding (reposition cup, more constraint, better soft tissue repair) ## Soft Tissue Reconstruction **Abductor Repair (CRITICAL):** - Assess quality and attachment - If detached: Repair with #5 non-absorbable sutures through bone tunnels or anchors - If poor quality: Advance or augment with allograft (Achilles tendon wrapped around GT) - Repair gluteus medius and minimus to GT anatomically - Poor abductors = instability and Trendelenburg **Capsule Repair:** - Repair meticulously if tissue present (#1 or #2 non-absorbable sutures) - Evidence: 50-70% reduction in posterior dislocation with repair - If deficient: Consider allograft reconstruction (dermal/fascial) - Creates posterior restraint **Short External Rotators:** - Repair to posterior capsule or GT with transosseous sutures - Provides posterior soft tissue stability ## Closure **Irrigation:** - 3-6 liters normal saline or antibiotic solution - Remove all debris, bone fragments, PMMA particles **Layered Closure:** 1. Gluteus maximus fascia (#1 absorbable) 2. Subcutaneous (2-0 or 3-0 absorbable) 3. Deep dermal (3-0 or 4-0 absorbable) 4. Skin (staples or subcuticular) **Dressing:** - Sterile dressing - Consider negative pressure wound therapy if high risk **Abduction Pillow:** - Place immediately (15-20° abduction) - CRITICAL for posterior dislocation prevention ## Additional Complications **Intraoperative Fracture:** - Femoral (1-3%): Often during stem removal or dislocation. Cable plates or strut grafts - Acetabular (1-2%): During cup removal or insertion. Protected weight bearing, consider screws or augments **VTE (3-5% with prophylaxis):** - Prevention: LMWH or DOAC for 4-6 weeks, mechanical compression, early mobilization - Management: Anticoagulation, consider IVC filter if contraindication to anticoagulation **Leg Length Discrepancy (10-15%):** - Balance stability (lengthening) vs nerve palsy risk - Aim <1cm, maximum 2cm to avoid nerve palsy - Shoe lift if persistent >1cm and symptomatic **Heterotopic Ossification (10-15%):** - Prevention: NSAIDs for 6 weeks (indomethacin 25mg TDS) or single-dose radiation - Management: Observe if asymptomatic, excision if limiting ROM after maturation (12-18 months) ## Immediate Postoperative (0-6 weeks) **Positioning:** - Abduction pillow CONTINUOUSLY for 6 weeks (15-20° abduction) - Remove only for therapy under supervision - Log roll for position changes **Hip Precautions (STRICT for 12 weeks MINIMUM):** - No hip flexion >90° (elevated toilet seat, no low chairs, no bending to floor) - No adduction past midline (no crossing legs, pillow between legs in bed) - No internal rotation (posterior approach) or external rotation (anterior approach) - Sleep supine or on operative side only with pillow between legs **Weight Bearing:** - Touch-down or partial (20kg) for 6 weeks if soft tissue repair or questionable fixation - Progress to weight bearing as tolerated if well-fixed components and no soft tissue concerns - Walker or crutches for first 6 weeks **Physiotherapy:** - Day 1-2: Supervised mobilization - Gait training with assistive device - Gentle ROM within precautions - Abductor strengthening when healed (6-12 weeks) **Medications:** - **Anticoagulation**: LMWH (enoxaparin 40mg SC daily) or DOAC (apixaban 2.5mg PO BID) for 4-6 weeks - **Antibiotics**: IV cefazolin 2g q8h or vancomycin for 24-48 hours - **Analgesia**: Multimodal (paracetamol, NSAIDs if not contraindicated, opioids PRN) - **VTE prophylaxis**: TED stockings, mechanical compression **Monitoring:** - Neurovascular checks (foot dorsiflexion, sensation) - document any deficit immediately - Wound inspection daily - Hemoglobin (transfusion if <70-80 g/L or symptomatic) **Imaging:** - Post-op AP pelvis and lateral hip within 48 hours - Document component position, leg length, exclude fracture ## Follow-Up Schedule **2 Weeks:** - Wound check, remove sutures/staples - Reinforce hip precautions - Assess pain control and mobility **6 Weeks:** - Clinical assessment (wound healing, pain, mobility, neurovascular status) - X-rays (AP pelvis, lateral hip) - compare to post-op films - Advance to full weight bearing if protected WB used - Continue hip precautions - Advance physiotherapy (ROM, abductor strengthening) **3 Months:** - Functional assessment (Oxford Hip Score, WOMAC, Harris Hip Score) - Discontinue hip precautions if soft tissues healed and appropriate patient compliance - May extend to 6 months if high risk - Advance to full activities gradually - X-rays (assess for loosening, HO) - Discontinue anticoagulation if no VTE **6 Months:** - Assess function, return to activities - X-rays (establish baseline for component position) - Monitor for complications (dislocation, infection, nerve palsy recovery) **Annual (Lifelong):** - Clinical assessment, functional scores - Radiographs (AP pelvis, lateral hip) - Surveil for late complications (loosening, wear, late dislocation/infection) ## Long-Term Outcomes **Re-Dislocation Rate:** - 5-15% with dual mobility (excellent vs historical 30-40%) - Most occur in first 6 months - 60-80% reduction compared to standard revision **Function:** - Significantly improved from chronic instability state - Not to level of uncomplicated primary THR - Hip scores improve average 30-40 points **Survivorship:** - 10-year implant survival 85-90% - Failure from loosening, infection, recurrent instability **Patient Satisfaction:** - 70-80% satisfied or very satisfied - Improvement over chronic instability - Anxiety about re-dislocation persists in many ## References 1. Alberton GM, High WA, Morrey BF. Dislocation after revision total hip arthroplasty: an analysis of risk factors and treatment options. J Bone Joint Surg Am. 2002;84(10):1788-1792. PMID: 12377909 2. Guyen O, Pibarot V, Vaz G, Chevillotte C, Bejui-Hugues J. Use of a dual mobility socket to manage total hip arthroplasty instability. Clin Orthop Relat Res. 2009;467(2):465-472. PMID: 18780135 3. Lewinnek GE, Lewis JL, Tarr R, Compere CL, Zimmerman JR. Dislocations after total hip-replacement arthroplasties. J Bone Joint Surg Am. 1978;60(2):217-220. PMID: 641088 4. Philippot R, Adam P, Reckhaus M, et al. Prevention of dislocation in total hip revision surgery using a dual mobility design. Orthop Traumatol Surg Res. 2009;95(6):407-413. PMID: 19656750 5. Wetters NG, Murray TG, Moric M, Sporer SM, Paprosky WG, Della Valle CJ. Risk factors for dislocation after revision total hip arthroplasty. Clin Orthop Relat Res. 2013;471(2):410-416. PMID: 22956239 6. Biedermann R, Tonin A, Krismer M, Rachbauer F, Eibl G, Stockl B. Reducing the risk of dislocation after revision total hip arthroplasty: the anterior approach. J Bone Joint Surg Br. 2005;87(6):762-769. PMID: 15911655 7. Springer BD, Fehring TK, Griffin WL, Odum SM, Masonis JL. Why revision total hip arthroplasty fails. Clin Orthop Relat Res. 2009;467(1):166-173. PMID: 18975043 8. De Martino I, Triantafyllopoulos GK, Sculco PK, Sculco TP. Dual mobility cups in total hip arthroplasty. World J Orthop. 2014;5(3):180-187. PMID: 25035818 9. Prudhon JL, Steffann F, Ferreira A, Verdier R, Aslanian T, Caton J. Cementless dual-mobility cup in total hip arthroplasty revision. Int Orthop. 2014;38(12):2463-2468. PMID: 25183293 10. Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Hip, Knee & Shoulder Arthroplasty: 2023 Annual Report. Adelaide: AOA; 2023. Available at: https://aoanjrr.sahmri.com/annual-reports-2023

Revision Total Hip Replacement for Recurrent Instability

Revision Total Hip Replacement for Recurrent Instability