import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Location**: 15-30mm posterior to hip joint (closer in revision due to scarring) **Injury Pattern**: Foot drop (tibial division) + foot eversion weakness (peroneal division) + sensory loss posterior calf/foot **Protection**: Identify early with vessel loop, keep hip flexed >45° to relax nerve, avoid excessive traction/lengthening >4cm, protect during posterior capsule work **Location**: 30-50mm medial to anterior hip joint, beneath iliopsoas **Injury Pattern**: Quadriceps paralysis, absent knee extension, anterior thigh numbness, catastrophic vascular injury if femoral artery damaged **Protection**: Stay on bone with anterior retractors (Hohmann), avoid medial cement extrusion, fluoroscopy for anterior screw placement **Location**: 30-50mm proximal to greater trochanter, exits sciatic notch above piriformis **Injury Pattern**: Gluteus medius/minimus paralysis (Trendelenburg gait), superior buttock numbness **Protection**: Avoid proximal dissection beyond GT tip, stay in safe zone (anterior-inferior quadrant), protect during GT osteotomy **Location**: Variable 20-50mm from anterior incisions (ASIS to anterolateral thigh) **Injury Pattern**: Meralgia paresthetica (lateral thigh burning/numbness) **Protection**: Identify and protect when visible during anterior approach, gentle retraction if encountered **Location**: 20-30mm medial to acetabulum, through obturator foramen **Injury Pattern**: Adductor weakness, medial thigh numbness, vascular injury rare **Protection**: Avoid medial acetabular screws below equator, use posterior-superior quadrant for fixation ## Comprehensive Evaluation Protocol ### Infection Workup (MANDATORY - Do NOT Skip) **Laboratory Tests**: - ESR and CRP (elevated suggests infection) - Joint aspiration GOLD STANDARD: Cell count (>3000 cells/µL), differential (>80% PMNs), aerobic/anaerobic cultures (hold 14 days), Gram stain **Rule**: Any revision for instability requires infection exclusion - infection can present as recurrent dislocation (30% of 'instability' cases in some series) ### Imaging Protocol **Standard Radiographs**: - AP pelvis (assess cup inclination, leg length, offset) - Lateral hip (assess cup anteversion on cross-table lateral) - Shoot-through lateral femur (assess stem version) **CT Pelvis with Metal Artifact Reduction (GOLD STANDARD for Component Position)**: - Measure cup inclination (radiographic plane): Normal 35-45°, safe zone 30-50° - Measure cup anteversion (radiographic plane): Normal 15-25°, safe zone 5-25° - Lewinnek safe zone: 40±10° inclination, 15±10° anteversion - Outside safe zone: 4x higher dislocation risk (9% vs 2%) - Assess impingement: Anterior wall overhang, posterior offset, neck-cup contact - Spinopelvic parameters: Pelvic tilt, sacral slope, lumbar lordosis (especially if spinal fusion or kyphosis) **Femoral Version Assessment**: - CT femur (measure stem anteversion): Normal 10-15° - Combined anteversion: Cup + stem should total 25-40° (Ranawat triangle) - Excessive stem anteversion (>20°) → posterior instability - Excessive stem retroversion (<5°) → anterior instability ### Dislocation Direction Classification **Posterior Dislocation (75-90%)**: - Mechanism: Flexion + adduction + internal rotation - Common scenarios: Getting up from low chair, tying shoes, getting into car - Component factors: Cup retroversion, excessive stem anteversion, posterior wall deficiency **Anterior Dislocation (10-25%)**: - Mechanism: Extension + external rotation + adduction - Common scenarios: Reaching back, pivoting on affected leg, leg crossing - Component factors: Excessive cup anteversion, stem retroversion, anterior impingement ### Risk Factor Identification **Component Malposition (MOST COMMON CORRECTABLE)**: - Cup outside safe zone (inclination or anteversion) - Stem malposition (excessive anteversion/retroversion) - Combined anteversion outside 25-40° **Impingement**: - Bony: Anterior acetabular wall overhang, posterior offset deficiency, femoral neck osteophytes - Component: Neck-cup contact, liner rim contact, modular neck-acetabular bone - Soft tissue: Iliopsoas over acetabular component (anterior), short external rotators (posterior) **Soft Tissue Deficiency**: - Capsule deficient or absent (PRIMARY PATHOLOGY in many recurrent dislocations) - Short external rotator attenuation (posterior stability) - Abductor insufficiency (Trendelenburg positive) **Patient Factors**: - Neuromuscular: Parkinson's disease (40-50% failure despite optimal surgery), dementia, CVA - Compliance: Cognitive impairment, psychiatric disorders, substance abuse - Anatomy: Femoral offset not restored, leg length inequality ### Dislocation History Documentation **Critical Data**: - Number of dislocations (first vs recurrent) - Time since surgery (early <90 days vs late) - Direction (posterior vs anterior) - Mechanism (high vs low energy) - Reduction method (closed vs open) - Previous revisions for instability ### Treatment Algorithm Decision Tree **NON-OPERATIVE** (First dislocation + well-positioned components + correctable risk factors): - Closed reduction under sedation - Hip abduction orthosis 6-12 weeks - Hip precautions 12 weeks minimum - Success rate: 60-70% after first, 30% after second, less than 20% after third **OPERATIVE** (Recurrent >2 episodes OR first with malposition/uncorrectable factors): - Component revision if malposition - Dual mobility liner (gold standard, 85-95% success) - Soft tissue reconstruction if deficient - GT advancement if abductor insufficiency ## Surgical Decision Making and Options ### Hierarchy of Treatment Options **OPTION 1: Isolated Liner/Head Exchange** (Least invasive - if components well-positioned): **Indications**: - Cup and stem in safe zones - Components stable and well-fixed - No impingement on CT - Recurrent instability despite good position (soft tissue/head size issue) **Technique**: - Remove head and liner - Insert dual mobility liner (PREFERRED) OR constrained liner OR lipped liner - Increase head size (32mm→36mm, 36mm→40mm) if adequate polyethylene thickness (>6mm) **Success Rate**: 85-95% with dual mobility **OPTION 2: Acetabular Revision** (Cup malposition/impingement/loose): **Indications**: - Cup outside safe zone (inclination or anteversion) - Impingement from cup position/orientation - Cup loosening **Technique**: - Remove cup (preserve bone) - Ream to bleeding bone - Reposition to safe zone: 40° inclination, 15-20° anteversion - Multiple screws (posterior-superior quadrant) - Insert dual mobility liner **Success Rate**: 80-90% when combined with dual mobility **OPTION 3: Femoral Revision** (Stem malposition/loose): **Indications**: - Stem excessive anteversion (>20°) or retroversion (<5°) - Combined anteversion outside 25-40° - Offset not restored - Stem loosening **Technique**: - Extract stem (may need ETO if well-fixed) - Revise to neutral version (10-15° anteversion) - Restore offset (modular stem helpful) - Large head (36-40mm) or dual mobility construct **Success Rate**: 80-90% when version corrected **OPTION 4: Dual Mobility (GOLD STANDARD for Instability)**: **Mechanism**: - Large metal outer bearing (52-60mm) articulates with acetabular cup - Small polyethylene inner bearing (28-32mm) articulates with femoral head - Two articulations reduce dislocation by 50-80% **Advantages**: - Delays impingement (large outer bearing increases ROM) - Preserves head-to-neck ratio (small inner head) - Lower dissociation rate (1-2% vs 3-5% constrained) - Less wear than constrained (metal-on-poly vs poly constraint) - Less torque to fixation (vs constrained locking mechanism) **Evidence**: Berry 2012 (0% re-dislocation in 140 revisions for instability), Guyen 2009 (0% at 10 years), Australian registry (reduced revision rate by 50%) **OPTION 5: Constrained Liner** (Second-line if dual mobility unavailable): **Mechanism**: - Locking ring captures femoral head - Prevents dislocation but limits ROM - Uses polyethylene thickness for constraint **Disadvantages**: - Dissociation 3-5% (locking mechanism failure) - Accelerated wear (constraint from polyethylene) - Higher torque to fixation (loosening risk) - Lower success (75-85% vs 85-95% dual mobility) **Use**: Only if dual mobility not available or contraindicated **OPTION 6: Soft Tissue Reconstruction**: **Capsular Repair/Reconstruction**: - Primary repair if adequate tissue - Achilles allograft reconstruction if deficient (attach acetabular rim to femoral neck) - Reduces re-dislocation when combined with component optimization **Greater Trochanteric Advancement**: - Indications: Abductor insufficiency (Trendelenburg positive) - Technique: Osteotomize GT with abductors, advance distally 1-2cm, screw fixation - Increases abductor moment arm and tension - Protected weight bearing 12 weeks for union ### Combined Anteversion Concept (Ranawat Triangle) **Principle**: Cup anteversion + stem anteversion should total 25-40° **Examples**: - Cup 20° + Stem 10° = 30° (SAFE) - Cup 30° + Stem 20° = 50° (HIGH - posterior instability risk) - Cup 10° + Stem 5° = 15° (LOW - anterior instability risk) **Application**: Correct BOTH components if combined anteversion outside 25-40° ### Spinopelvic Parameters (Advanced Concept) **Relevance**: Pelvic tilt changes cup orientation in standing vs sitting **High-Risk Patients**: - Spinal fusion (rigid spine, changes pelvic tilt) - Spinal deformity (kyphosis, flatback) - Elderly with loss of lumbar lordosis **Assessment**: Lateral standing and sitting radiographs, measure pelvic tilt change **Management**: May need cup anteversion adjustment (more anteversion if anterior tilt, less if posterior tilt) ## Step-by-Step Operative Technique ### Positioning and Approach Selection **Patient Position**: - Lateral decubitus for posterior approach (90% of primary THRs) - Supine for anterior approach (if primary done anteriorly) **Approach Choice**: - **Use PREVIOUS APPROACH** to minimize soft tissue damage - Posterior approach most common (extended posterior approach for revision) - Anterior approach if primary done anteriorly **Fluoroscopy**: Essential for intraoperative component position assessment ### Surgical Exposure **Incision**: - Utilize previous incision, excise scar - Extend proximally/distally as needed (revision requires longer exposure) **Posterior Approach Exposure**: 1. Incise fascia lata over greater trochanter 2. Split gluteus maximus in line with fibers (protect superior gluteal nerve proximally) 3. **IDENTIFY SCIATIC NERVE EARLY** - vessel loop for protection (higher risk in revision, 3-7% palsy rate) 4. Tag short external rotators if present (often attenuated/absent) 5. Extensive capsulectomy - capsule usually deficient (PRIMARY PATHOLOGY) **Dislocation**: - Posterior: Flex 90°, adduct, internal rotate - May be scarred in position, require extensive soft tissue release ### Intraoperative Assessment (CRITICAL) **Component Position**: - Fluoroscopy: Measure cup inclination and anteversion - Direct visualization: Stem version assessment - Combined anteversion calculation **Impingement Testing**: - Reproduce dislocation mechanism (flex/adduct/IR for posterior) - Identify neck-cup contact, liner rim impingement - Check throughout ROM **Soft Tissue Quality**: - Capsule: Intact vs deficient vs absent - Short external rotators: Present vs attenuated - Abductors: Strong vs weak (Trendelenburg test) **Range to Dislocation**: - Test stability in all positions - Identify safe vs unsafe ROM ### Component Removal and Exchange **Acetabular Cup Removal** (if indicated): 1. Remove modular liner 2. **Loose cup**: Usually levers out with curved osteotomes 3. **Well-fixed cup**: Circumferential osteotomes, stay on metal (preserve bone), may need Explant system 4. Remove all cement if cemented 5. Preserve bone stock (critical for revision) **Femoral Stem Removal** (if indicated): 1. Remove head and liner 2. **Loose stem**: Extract with gentle impaction and extraction devices 3. **Well-fixed stem**: Extended Trochanteric Osteotomy (ETO) - Anterior 1/3 of femur for 10-12cm - GT attached to vastus lateralis - Repair with cerclage wires after stem insertion 4. **DO NOT FORCE** - will fracture femur 5. Remove cement (high-speed burr, osteotomes, ultrasonic) ### Component Revision and Repositioning **Acetabular Revision**: 1. Ream acetabulum to bleeding bone 2. Size for press fit (1-2mm under-ream) 3. **Position to safe zone**: 40° inclination, 15-20° anteversion 4. Use fluoroscopy to confirm position 5. Multiple screws (posterior-superior quadrant, avoid anterior/medial neurovascular structures) 6. Augments if bone loss (porous metal to fill defects, achieve 50% host bone contact) 7. **Insert dual mobility liner** (gold standard) **Femoral Revision**: 1. Ream/broach canal to appropriate size 2. Select revision stem: - Adequate metaphyseal bone → modular stem (adjust offset and version independently) - Bone loss → extensively coated diaphyseal-fit stem 3. **Position in neutral version** (10-15° anteversion) 4. **Restore offset** (compare to contralateral) 5. If ETO performed, repair with 2-3 cerclage wires before final head 6. **Large head** (36-40mm) or dual mobility construct **Isolated Liner Exchange** (if components well-positioned): 1. Dislocate hip, remove head 2. Remove modular liner (locking tabs, specialized tools) 3. Clean cup taper (remove debris, inspect for wear) 4. **Insert dual mobility liner** (large metal outer bearing locks into cup, small poly inner bearing for head) 5. Alternative: Constrained liner (locking ring) or lipped liner (elevated rim) 6. Insert large head (36-40mm if adequate poly thickness >6mm) ### Soft Tissue Reconstruction **Capsular Repair/Reconstruction**: 1. **If adequate capsule**: Primary repair to femoral neck/GT with heavy non-absorbable sutures (#2 or #5 Ethibond) 2. **If inadequate capsule**: Achilles tendon allograft reconstruction - Attach to acetabular rim (drill holes, secure with sutures) - Attach to femoral neck/GT (transosseous sutures) - Recreate anterior and posterior restraints **Short External Rotator Repair** (Critical for posterior stability): - Repair piriformis, gemelli, obturators, quadratus femoris to GT/posterior capsule - Transosseous sutures if bone quality adequate - May be attenuated - do best possible repair **Greater Trochanteric Advancement** (if abductor insufficiency): 1. Osteotomize GT with attached gluteus medius/minimus 2. Advance distally 1-2cm (increases abductor moment arm and tension) 3. Fix with screws and washers OR cables 4. Protected weight bearing 12 weeks until union ### Trial Reduction and Stability Testing (CRITICAL) **Stability Protocol**: 1. **Posterior stability** (MOST IMPORTANT): 90° flexion + adduction + IR, apply posterior force - must be stable with firm endpoint 2. **Anterior stability**: Extension + ER + adduction - must remain reduced 3. **Mid-range**: 45° flexion, neutral rotation, abduction/adduction 4. **Extremes of motion**: Full flexion, extension, abduction, adduction - identify impingement 5. **Shuck test**: Quantify translation (should be minimal) **Rule**: Must be STABLE throughout ROM with no impingement. If unstable, options: - Increase head size - Change to dual mobility or constrained - Adjust component position - Increase soft tissue tension **DO NOT ACCEPT INSTABILITY** - will fail post-operatively ### Closure **Layered Closure**: 1. Capsule and short external rotators to femoral neck/GT (heavy non-absorbable sutures) 2. If GT osteotomy, confirm stable fixation (2-3 screws + washer OR cables) 3. Gluteus maximus fascia (close securely) 4. Deep fascia and subcutaneous layer 5. Skin (monofilament or staples) **Abduction Pillow**: Place between legs **Drain**: Consider if large dead space (remove 24-48hr) ### Salvage Options for Failed Revision **Indications**: Multiple recurrent dislocations despite optimal revision, unreconstructable bone loss, chronic infection **Girdlestone Resection Arthroplasty**: - Remove all components, accept shortened painful limb - Patient: Elderly, low demand, walker dependent baseline - Outcome: Significant functional limitation but pain relief **Hip Arthrodesis**: - Patient: Young (<40), unilateral, high demand, no hip/spine arthritis - Position: 20-25° flexion, 0° adduction/abduction, neutral rotation - Outcome: Stable painless hip but causes back/knee pain (rare, last resort) **Bipolar Hemiarthroplasty**: - Indication: Severe acetabular bone loss precludes stable cup - Accepts higher dislocation rate but avoids complex acetabular reconstruction ## Evidence-Based Outcomes ### Treatment-Specific Success Rates **Non-Operative Management (First Dislocation)**: - First episode: 60-70% success (Patel 2007) - Second episode: Success drops to 30% - Third episode: Success less than 20% - Method: Closed reduction, hip abduction orthosis 6-12 weeks, precautions 12 weeks **Isolated Liner Exchange to Dual Mobility** (Well-positioned components): - Success: 85-95% (Berry 2012, Guyen 2009) - Re-dislocation: 0-5% - Least invasive option if components stable and in safe zones **Component Revision + Dual Mobility**: - Success: 80-90% (Philippot 2009) - Re-dislocation: 10-20% - Best for malpositioned components outside safe zone **Constrained Liner**: - Success: 75-85% (Lombardi 1991, Anderson 1994) - Re-dislocation OR dissociation: 15-25% - Dissociation rate: 3-5% (higher than dual mobility 1-2%) **Component Revision Alone** (No dual mobility or constraint): - Success: 60-75% - Re-dislocation: 25-40% - Inferior to dual mobility - no longer recommended as sole treatment ### Dual Mobility Evidence Base **Berry 2012** (Landmark Study): - 140 patients revised for instability with dual mobility - 0% re-dislocation at mean 4.5 years - Conclusion: Dual mobility is gold standard **Guyen 2009** (Long-term Follow-up): - 113 primary THRs with dual mobility (high-risk patients) - 0% dislocation at mean 10 years - 5% cup revision for aseptic loosening - Conclusion: Durable long-term solution **Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR)**: - Dual mobility reduces revision rate for dislocation by 50% compared to standard bearings - Increasingly used for primary THR in high-risk patients (prior hip surgery, neuromuscular disorders, spine disease) ### Factors Affecting Outcomes **Better Prognosis**: - Correctable component malposition (just outside safe zone) - Adequate soft tissue for repair - Compliant patient - First or second revision **Worse Prognosis**: - Neuromuscular disorders: Parkinson's 40-50% failure despite optimal surgery (Meek 2011) - Dementia/cognitive impairment (non-compliance with precautions) - Severe abductor deficiency (Trendelenburg despite GT advancement) - Multiple prior revisions (bone stock loss limits options) - Spinopelvic abnormalities (spinal fusion, flatback deformity) ### Long-Term Surveillance **Follow-Up Schedule**: - 2 weeks: Wound check - 6 weeks: Radiographs, advance activity - 3 months: Radiographs, wean brace - 6 months: Radiographs and function assessment - 1 year: Radiographs - Annually for life: Radiographs, function (Oxford Hip Score, HOOS) **Surveillance for**: - Late dislocation (can occur years later) - Accelerated wear (dual mobility metal-on-poly, constrained poly) - Component loosening (especially constrained liner - increased torque) - Neuromuscular progression (Parkinson's, dementia) ### Australian Context **AOANJRR Data** (2023 Report): - THA dislocation accounts for 15% of all revisions - Dual mobility use increasing: 5% of primary THRs in 2022 (vs 1% in 2012) - Dual mobility in revision: 40% for instability (vs 10% constrained, 50% standard) - Re-revision rate lower with dual mobility (5-year: 8% dual mobility vs 15% constrained) **Medicare MBS Item Numbers**: - 49318: Revision of acetabular component - 49319: Revision of femoral component - 49321: Revision of both components - 49327: Greater trochanteric osteotomy **PBS/eTG Antibiotic Guidelines**: - Prophylaxis: Cefazolin 2g (>120kg: 3g) within 60min of incision - Penicillin allergy: Vancomycin 15mg/kg OR clindamycin 600mg - Duration: Single dose (cease within 24hr) ## References 1. Berry DJ, von Knoch M, Schleck CD, Harmsen WS. Effect of femoral head diameter and operative approach on risk of dislocation after primary total hip arthroplasty. J Bone Joint Surg Am. 2005;87(11):2456-2463. doi:10.2106/JBJS.D.02860 2. 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 3. Berry DJ, von Knoch M, Schleck CD, Harmsen WS. The cumulative long-term risk of dislocation after primary Charnley total hip arthroplasty. J Bone Joint Surg Am. 2004;86(1):9-14. doi:10.2106/00004623-200401000-00003 4. 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. doi:10.1007/s11999-008-0476-0 5. 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. doi:10.1016/j.otsr.2009.04.016 6. Lombardi AV Jr, Mallory TH, Kraus TJ, Vaughn BK. Preliminary report on the S-ROM constraining acetabular insert: a retrospective clinical experience. Orthopedics. 1991;14(3):297-303. PMID: 2020623 7. Anderson MJ, Murray WR, Skinner HB. Constrained acetabular components. J Arthroplasty. 1994;9(1):17-23. doi:10.1016/0883-5403(94)90132-5 8. Patel PD, Potts A, Froimson MI. The dislocating hip arthroplasty: prevention and treatment. J Arthroplasty. 2007;22(4 Suppl 1):86-90. doi:10.1016/j.arth.2007.03.031 9. Meek RM, Allan DB, McPhillips G, Kerr L, Howie CR. Epidemiology of dislocation after total hip arthroplasty. Clin Orthop Relat Res. 2006;447:9-18. doi:10.1097/01.blo.0000218754.12311.4a 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

Total Hip Replacement Dislocation - Comprehensive Assessment and Management

Total Hip Replacement Dislocation - Comprehensive Assessment and Management