import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Location**: Posterior to femur in adductor compartment, gives 3-4 perforating branches through lateral intermuscular septum at levels corresponding to proximal, middle, and distal thirds of femur. **Protection Strategy**: Use lateral approach through vastus lateralis, stay on lateral cortex, blunt dissection perpendicular to muscle fibers. Avoid posterior dissection beyond lateral cortex. Entry point 2-3cm below vastus ridge minimizes risk to first perforating branch. **Location**: Posterior to hip joint and femur, exits pelvis below piriformis through greater sciatic notch, runs between hamstrings and adductors in posterior thigh, 3-5cm posterior to femoral shaft. **Protection Strategy**: Lateral percutaneous approach stays well anterior to nerve. Patient supine with hip in neutral position. Avoid excessive hip flexion which tensions nerve. No dissection posterior to lateral intermuscular septum. **Location**: Exits pelvis above piriformis through greater sciatic notch, runs between gluteus medius and minimus muscles, 3-5cm superior to greater trochanter tip. Supplies gluteus medius/minimus. **Protection Strategy**: Entry point 2-3cm DISTAL to vastus ridge (below greater trochanter) avoids this structure. Avoid proximal entry into or above greater trochanter. Confirm entry point on AP fluoroscopy before incision. **Location**: Overlies entire femoral head articular surface, separated from necrotic zone by 2-5mm thick subchondral bone plate. Anterosuperior weight-bearing dome most critical area. **Protection Strategy**: MANDATORY 5mm safety margin from subchondral bone on both AP and lateral fluoroscopy. Use depth markings on guidewire/drill. Measure from lateral cortex to subchondral bone before drilling. Biplanar imaging prevents 3D misjudgment. **Location**: Anterior cortex of femoral neck is thin (2-3mm) and easily perforated with excessive anterior trajectory, especially in osteoporotic bone. Perforation creates stress riser and fracture risk. **Protection Strategy**: Trajectory planning on BOTH AP and lateral views before drilling. On lateral view, aim for mid-anterior third of femoral head, NOT extreme anterior. If guidewire perforates anterior cortex, remove and redirect. Final fluoroscopy confirms no cortical breach. ## Absolute Indications - **Ficat/ARCO Stage I-II AVN** with failed conservative management (activity modification, bisphosphonates, protected weight-bearing for 3-6 months) - **Small to medium lesion size**: <30% femoral head volume, <250° Kerboul angle on MRI - **Young patient**: <50 years (ideally <40 years) - high THA revision risk justifies aggressive preservation - **Preserved joint space**: >2mm on AP weight-bearing radiograph - **Symptomatic hip pain**: Interfering with activities of daily living, work, or recreation ## Relative Indications - **Asymptomatic Stage I-II AVN** in high-risk patient (bilateral disease, ongoing steroid use) - controversial but may prevent progression - **Medium-large lesion (15-30%)**: Consider adjuncts (tantalum rod, vascularized fibula) to improve outcomes - **Ficat Stage IIC (small crescent)**: Very controversial - most surgeons proceed to arthroplasty but some attempt salvage with vascularized fibula ## Contraindications (Absolute) - **Ficat/ARCO Stage III-IV**: Established collapse (crescent sign), flattening, or secondary arthritis - proceed to arthroplasty - **Large lesion**: >30% femoral head, >250° Kerboul angle - very high failure rate (70-80%), consider primary THA or vascularized fibula - **Active infection**: Septic arthritis or osteomyelitis - contraindication to any hip preservation - **Significant osteoarthritis**: Joint space <2mm, Tönnis grade 2-3 changes - unlikely to benefit ## Contraindications (Relative) - **Elderly/low demand patient**: >65 years - THA may be more predictable option - **Severe osteoporosis**: Fracture risk during procedure or post-op, consider bone optimization first - **Morbid obesity**: BMI >40 - technical difficulty with percutaneous approach, high mechanical load on healing head - **Patient unwilling to comply**: With protected weight-bearing protocol for 12 weeks ## Staging Systems - Know Both! ### FICAT Classification (X-ray based) - **Stage I**: Normal X-ray, MRI shows marrow edema/necrosis - **Stage II**: Sclerosis, cysts, porosis on X-ray, NO collapse - **Stage III**: Crescent sign (subchondral fracture), early collapse - **Stage IV**: Flattening, head deformity, secondary acetabular arthritis ### ARCO Classification (adds MRI quantification) - **Stage 0**: Normal imaging, high-risk patient (bilateral, steroids) - **Stage I**: Normal X-ray, MRI positive - subdivided by lesion size (<15%, 15-30%, >30%) - **Stage II**: Abnormal X-ray, no collapse - subdivided by lesion size - **Stage III**: Subchondral fracture (crescent) - subdivided by flattening (<2mm, 2-4mm, >4mm) - **Stage IV**: Acetabular involvement ### Kerboul Angle Method (Lesion Size Quantification) On MRI: Find coronal cut showing largest necrotic extent, measure angle from center of femoral head to edges of necrotic zone. Repeat on sagittal cut. Sum both angles. - **<200°**: Good prognosis (80-90% success) - **200-250°**: Intermediate (50-70% success) - **>250°**: Poor (30-40% success) ## Evidence Base **Success Rates by Stage/Size**: - Ficat I + <15% lesion = 85-90% avoid arthroplasty at 5 years - Ficat I + 15-30% lesion = 60-75% - Ficat I + >30% lesion = 40-50% - Ficat II + <15% lesion = 70-80% - Ficat II + >30% lesion = 30-40% **AOANJRR Data**: Young AVN patients undergoing THA have 25-30% revision rate at 10 years vs 5-7% for OA patients - supports aggressive joint preservation attempts. ## Femoral Head Blood Supply (Critical for Understanding AVN) ### Normal Vascular Anatomy - **Medial femoral circumflex artery (MFCA)**: Dominant supply (80-90% of head) - Posterior superior retinacular vessels to posterosuperior head - Posterior inferior retinacular vessels to posteroinfeiror head - **Lateral femoral circumflex artery (LFCA)**: Minor supply (10-20%) - Anterior retinacular vessels - **Artery of ligamentum teres**: Minimal (<5% in adults, more in children) ### AVN Pathophysiology Interruption of MFCA supply (trauma, emboli, thrombosis) → ischemia → osteocyte death → necrotic zone formation → mechanical failure of dead bone → subchondral fracture (crescent) → collapse → arthritis ### Typical AVN Lesion Location **Anterosuperior weight-bearing dome** (90% of cases) - watershed zone between MFCA and LFCA territories. This is your TARGET for core decompression trajectory. ## Surgical Approach: Percutaneous Lateral ### Entry Point Selection **Anatomic landmark**: 2-3cm distal to vastus ridge (palpable prominence on lateral femur at base of greater trochanter) **Fluoroscopic confirmation**: - **AP view**: Lateral cortex of femur, below and slightly posterior to greater trochanter - **Lateral view**: Posterior one-third of femoral shaft ### Trajectory Planning (3D Understanding Critical!) From lateral femur entry → through lateral cortex → into intramedullary canal → across femoral neck → into femoral head → toward anterosuperior dome → STOP 5mm from subchondral bone **AP view trajectory**: Directed medially and slightly superiorly toward weight-bearing dome **Lateral view trajectory**: Directed anteriorly toward mid-anterior third of head (NOT extreme anterior - risk of anterior cortex perforation) ### Tissue Layers (Lateral Approach) 1. Skin (1-2cm incision) 2. Subcutaneous fat 3. Fascia lata (incise in line with fibers) 4. Vastus lateralis muscle (blunt dissection perpendicular to fibers) 5. Lateral femoral cortex (entry point for guidewire) ## Critical Anatomic Relationships ### What You're AVOIDING (Danger Zones) - **Posterior**: Profunda femoris perforating branches (through lateral intermuscular septum) - **Anterior-medial**: Femoral neurovascular bundle (far from lateral approach) - **Superior**: Superior gluteal neurovascular bundle (above GT - avoid proximal entry) - **Sciatic nerve**: Posterior to hip (lateral approach stays far anterior) ### What You're TARGETING - **Anterosuperior femoral head**: Weight-bearing dome where AVN lesion typically located - **Center of necrotic zone**: Based on preoperative MRI correlation - **5mm from subchondral bone**: Safety margin to protect articular cartilage ## Fluoroscopy Setup - Biplanar Imaging Essential ### AP Pelvis View - Both hips visible for comparison - Femoral head perfectly circular (not rotated) - Allows visualization of mediolateral trajectory - Shows depth to medial subchondral bone ### Cross-table Lateral OR Frog-Leg Lateral - Shows anteroposterior trajectory - Confirms depth to anterior subchondral bone - Identifies femoral neck anterior cortex position **Critical**: Must check BOTH views alternately during guidewire advancement - 3D trajectory cannot be judged from single view! ## Core Decompression Techniques ### Single Large Core (8-11mm diameter) **Technique**: Cannulated trephine or reamer over guidewire, creates one large channel **Advantages**: - Allows structural graft placement (non-vascularized fibula, tantalum rod) - Removes solid core of necrotic tissue intact for histology - Theoretically better decompression of central lesion **Disadvantages**: - Greater weakening of femoral neck - higher fracture risk - Larger stress riser at entry point (subtrochanteric fracture risk) - May need 10-12 weeks protected weight-bearing vs 6-8 weeks for small cores **Best For**: Medium lesions (15-30%) where adjunct graft/rod planned ### Multiple Small Cores (3-4 × 3.5mm) **Technique**: First guidewire to lesion center, then place 2-3 additional parallel wires around first (1cm spacing), drill each with 3.5mm bit **Advantages**: - Less femoral neck weakening - Multiple drainage pathways - Allows "gradient" decompression around lesion - Shorter protected weight-bearing (6-8 weeks) **Disadvantages**: - Cannot place structural graft - More radiation exposure (multiple wire placements) - Technically more complex - must ensure wires converge on lesion **Best For**: Small lesions (<15%) where adjunct graft not needed ### Evidence Comparison Multiple systematic reviews show **NO SIGNIFICANT DIFFERENCE** in outcomes between single large core vs multiple small cores. Choice based on surgeon preference and whether adjunct graft planned. ## Adjunct Techniques for Medium-Large Lesions ### Tantalum Rod (Porous Trabecular Metal) **Technique**: After core decompression (8-10mm), impact tantalum rod (10-12mm diameter, length to within 5mm of subchondral bone) into track. Tantalum is highly porous allowing biologic ingrowth. **Mechanism**: Provides structural support to subchondral bone + scaffold for revascularization through porous structure **Outcomes**: 50-70% success in Stage II, 40-50% in early Stage III - similar to vascularized fibula but much simpler technique **Advantages**: - No microsurgery required (vs vascularized fibula) - No donor site morbidity - Radiopaque - easy follow-up monitoring - Can revise to THA later without difficulty **Disadvantages**: - Expensive implant - No active blood supply (relies on host ingrowth) - Can migrate if undersized - Metal artifact on MRI (limits post-op imaging) ### Vascularized Fibula Graft **Technique**: Harvest 8-12cm segment of proximal fibula with peroneal artery pedicle. Insert through 12-15mm core track. Microsurgical anastomosis of peroneal artery to ascending branch of LFCA. **Mechanism**: Provides BOTH structural support (load-bearing strut) AND active revascularization via blood supply **Outcomes**: 70-90% success even in Stage III (post-collapse) - BEST outcomes for salvage procedures **Advantages**: - Active blood supply provides revascularization - Structural support prevents collapse - Can treat larger lesions and post-collapse cases **Disadvantages**: - Requires microsurgical training and equipment - Significant donor site morbidity (ankle stiffness 20-30%, peroneal nerve injury 5-10%, chronic pain 15-25%) - 4-6 hour procedure vs 45-60 min for core alone - Higher complication rate - Difficult to revise to THA (fibula incorporation) **Best For**: Large lesions (>30%, >250° Kerboul) in young patients (<35 years) where THA would have very high revision risk ### Non-Vascularized Fibula Strut **Technique**: Harvest 8-10cm fibula segment WITHOUT vascular pedicle, insert through core track, impact into subchondral bone **Mechanism**: Structural support only (no blood supply) - acts as "internal splint" **Outcomes**: 40-60% success - better than core alone for medium lesions but worse than vascularized **Advantages**: - Simpler than vascularized (no microsurgery) - Structural support - Lower donor morbidity than vascularized **Disadvantages**: - No revascularization mechanism - Fibula may resorb over time - Still has donor site morbidity (though less than vascularized) ### Bone Marrow Aspirate Concentrate (BMAC) **Technique**: Aspirate 60-120ml bone marrow from iliac crest, centrifuge to concentrate mesenchymal stem cells, inject into core track(s) **Mechanism**: Theoretical enhancement of revascularization and bone healing via stem cell and growth factor delivery **Outcomes**: CONFLICTING evidence - some studies show 10-15% improvement in success rates, others show no difference **Advantages**: - Minimal additional morbidity (iliac aspiration only) - Can combine with any core technique - Relatively low cost **Disadvantages**: - Evidence limited and inconsistent - No structural support - Requires centrifuge equipment ### Biologic Adjuncts (Investigational) - **BMP-7 or BMP-2**: Theoretical enhancement of bone healing but limited evidence, concerns about HO and malignancy - **Cultured stem cells**: Multiple small trials show promise but not standard practice, regulatory issues - **Platelet-rich plasma (PRP)**: Very limited evidence, most studies show no benefit over core alone ## Comprehensive Operative Steps ### Step 1: Preoperative Planning & Staging Review imaging systematically: 1. **AP pelvis X-ray**: Assess stage (normal = I, sclerosis/cysts = II, crescent = III, collapse = IV), joint space (>2mm required), bilateral involvement (30-70% of cases) 2. **Lateral hip X-ray** (frog-leg best): Look for crescent sign (contraindication!), assess anterior head involvement 3. **MRI T1 + T2**: Measure Kerboul angle (sum of arcs on coronal + sagittal), identify lesion location (usually anterosuperior), look for double-line sign (pathognomonic), assess for marrow edema (high T2) 4. **Document stage**: Ficat and ARCO (exam may ask for both!) 5. **Measure lesion size**: Percentage of head volume and Kerboul angle - determines prognosis and need for adjuncts 6. **Check contralateral hip**: 30-70% bilateral in non-traumatic AVN **Technical Tip**: "I systematically review X-rays for Ficat stage and MRI for ARCO stage and lesion quantification. CRESCENT SIGN is absolute contraindication - indicates subchondral fracture and irreversible collapse. Kerboul angle <200° predicts 80-90% success, >250° only 30-40% success. I counsel patients accordingly and discuss adjuncts or arthroplasty for large lesions. MRI double-line sign is pathognomonic - low T1, high T2 rim surrounding necrotic zone." - Operating on Stage III-IV disease (crescent sign, collapse) - will fail, waste of surgery - Underestimating lesion size leading to unrealistic expectations - Missing bilateral disease (must image and counsel about contralateral hip) - Inadequate staging - need BOTH X-ray and MRI for complete assessment ### Step 2: Patient Setup & Fluoroscopy 1. **Position**: Supine on radiolucent table (fracture table optional but allows traction if needed for C-arm visualization) 2. **Hip position**: Neutral rotation (slight 10-15° internal rotation may relax anterior capsule and improve visualization) 3. **C-arm setup**: Test biplanar imaging BEFORE draping - AP pelvis: Both hips visible, femoral head perfectly circular - Lateral: Cross-table OR frog-leg (surgeon preference) 4. **Mark entry point**: Under fluoroscopy - lateral thigh, 2-3cm distal to palpable vastus ridge 5. **Prep and drape**: Wide prep including hip, lateral thigh, and iliac crest (if BMAC planned) **Technical Tip**: "I position supine on radiolucent table with C-arm for biplanar fluoroscopy - AP and lateral views are MANDATORY for 3D trajectory planning. I test fluoroscopy before draping to ensure perfect visualization of femoral head and subchondral bone on both views. Entry point marked fluoroscopically at 2-3cm below vastus ridge (palpable prominence), confirmed on both AP and lateral to ensure trajectory will reach lesion center. Hip in neutral prevents rotational malalignment." - Poor fluoroscopy quality preventing accurate depth assessment - adjust C-arm before draping - Wrong entry point (too proximal into GT, too distal creating stress riser) - Hip flexion contracture limiting positioning - may need lateral positioning instead - Inadequate radiation protection - lead aprons, thyroid shields, distance ### Step 3: Entry Point & Trajectory Planning 1. **Skin incision**: 1-2cm stab incision over marked entry point 2. **Fascia lata**: Incise in line with fibers (longitudinal split) 3. **Vastus lateralis**: Blunt dissection perpendicular to muscle fibers with curved hemostat - spread to bone 4. **Identify lateral cortex**: Confirm with fluoroscopy on both views 5. **Trajectory planning**: - AP view: Toward weight-bearing dome (slightly superior to head center) - Lateral view: Toward mid-anterior third (NOT extreme anterior) - Correlate with preoperative MRI lesion location 6. **Measure depth**: From lateral cortex to subchondral bone on both views, subtract 5mm for safety margin **Technical Tip**: "I make small 1-2cm stab incision and use blunt dissection through vastus lateralis to lateral cortex - minimizes blood loss and soft tissue trauma. Before drilling, I plan trajectory on BOTH AP and LATERAL views, correlating with preoperative MRI lesion location. Typical lesion is anterosuperior weight-bearing dome. I measure depth from lateral cortex to subchondral bone on fluoroscopy and subtract 5mm safety margin - this is CRITICAL measurement to prevent articular penetration." - Entry too proximal (GT fracture risk) or too distal (subtrochanteric stress riser) - Trajectory misses lesion (ineffective decompression) - correlate with MRI - Perforating vessel injury if dissection too posterior through lateral intermuscular septum - Failure to plan 5mm safety margin leads to articular penetration ### Step 4: Guidewire Placement 1. **Initial wire placement**: 2.0-2.4mm smooth or threaded guidewire through entry point 2. **Penetrate lateral cortex**: With mallet taps or power, confirm intramedullar position 3. **Advance across femoral neck**: Check AP and lateral views alternately - adjust trajectory as needed 4. **Aim for lesion center**: Based on preoperative MRI, typically anterosuperior dome 5. **Approach subchondral bone**: Slow advancement with frequent fluoroscopy checks 6. **STOP at 5mm from articular surface**: Use depth markings on wire, confirm on BOTH views 7. **Final position check**: - AP: Wire in weight-bearing dome, 5mm from medial subchondral bone - Lateral: Wire in mid-anterior head, 5mm from anterior subchondral bone - No cortical perforation (neck or shaft) 8. **If position suboptimal**: Remove wire and redirect - do NOT proceed with wrong trajectory **Technical Tip**: "I advance guidewire under continuous biplanar fluoroscopy, checking AP and lateral views alternately. Wire must reach center of AVN lesion (correlated with preoperative MRI) and stop 5mm from subchondral bone on BOTH views - this 5mm margin is absolutely CRITICAL. Articular penetration is catastrophic, causing rapid joint destruction. I use depth markings on wire and measure from lateral cortex to subchondral bone. If trajectory is off-target on either view, I remove and redirect before drilling - cannot correct after core created." - ARTICULAR CARTILAGE PENETRATION - catastrophic complication, rapid joint destruction, requires salvage THA - Wire misses lesion (wrong trajectory) - ineffective decompression, symptoms persist - Femoral neck anterior cortex perforation - creates stress riser, fracture risk - Subtrochanteric cortex perforation at entry site - fracture risk - Wire breakage if excessive force during advancement ### Step 5: Core Decompression **For SINGLE LARGE CORE (8-11mm)**: 1. Select cannulated trephine or reamer (8-11mm diameter) over guidewire 2. Advance with gentle pressure and rotation, frequent fluoroscopy checks 3. Irrigate copiously during reaming (prevent thermal necrosis) 4. Stop at predetermined depth (5mm from subchondral bone) 5. Remove trephine and extract solid core of necrotic bone 6. Send core for histology (confirms AVN, rules out tumor/infection) **For MULTIPLE SMALL CORES (3-4 × 3.5mm)**: 1. Drill first wire track with 3.5mm cannulated drill bit to planned depth 2. Leave first wire in place as reference 3. Place 2-3 additional guidewires parallel to first, spaced 1cm apart, all converging on lesion center 4. Drill each additional wire track with 3.5mm bit 5. Extract cores from each track 6. Send representative core for histology 7. Copiously irrigate all tracks **Technical Tip**: "Single large core (8-11mm) vs multiple small cores (3-4 × 3.5mm) - literature shows similar outcomes, choice based on whether adjunct graft planned. Large core allows tantalum rod or fibula strut placement. I advance under fluoroscopy to within 5mm of subchondral bone - absolutely DO NOT violate articular cartilage. I send core for histology to confirm AVN diagnosis (empty osteocyte lacunae, necrotic marrow), rule out malignancy or infection. Copious irrigation prevents thermal injury during drilling." - Articular penetration during reaming - use depth stops, frequent fluoroscopy - Femoral neck fracture (especially large trephines >10mm) - minimize weakening - Subtrochanteric fracture from large core stress riser at entry point - Thermal injury from drilling - copious irrigation essential - Inadequate depth (not reaching lesion center) - ineffective decompression ### Step 6: Adjunct Procedures (If Indicated) **TANTALUM ROD** (for medium-large lesions 15-30%): 1. Select rod diameter 1-2mm larger than core (10-12mm typical) 2. Measure rod length to within 5mm of subchondral bone 3. Impact rod through core track with mallet until stable 4. Confirm position on biplanar fluoroscopy - within 5mm margin, stable, no migration **BONE GRAFT** (structural support for large lesions): 1. Harvest non-vascularized fibula (8-10cm segment from proximal fibula) 2. Trim to fit core track (typically 8-10mm diameter) 3. Measure length to within 5mm of subchondral bone 4. Impact into core track, confirm stability and position **BMAC** (adjunct for any core technique): 1. Aspirate 60-120ml bone marrow from posterior iliac crest 2. Centrifuge to concentrate stem cells (follow device protocol) 3. Inject 5-10ml BMAC into each core track under fluoroscopy **Technical Tip**: "For lesions 15-30% (200-250° Kerboul), I consider adjuncts to improve outcomes. TANTALUM ROD provides structural support and porous scaffold for ingrowth - simpler than vascularized fibula with similar outcomes (50-70% success). For lesions >30% (>250°) in young patients (<35 years), VASCULARIZED FIBULA provides best salvage option (70-90% success even Stage III) but requires microsurgical expertise and has significant donor morbidity. BMAC has limited evidence but minimal additional risk." - Tantalum rod migration if undersized or inadequate impaction - Fibula graft donor site morbidity (ankle pain/stiffness 20-30%, nerve injury 5-10%) - Rod/graft too long (articular penetration) or too short (inadequate support) - Increased operative time and complexity with adjuncts - Heterotopic ossification risk with BMP (if used) ### Step 7: Hemostasis & Closure 1. **Copious irrigation** of all core tracks to remove debris and blood 2. **Hemostasis**: Usually minimal due to avascular nature of necrotic bone 3. **Final fluoroscopy check**: - No iatrogenic fracture (femoral neck, subtrochanteric, femoral shaft) - Appropriate depth (5mm from subchondral bone on both views) - Graft/rod position if used (stable, correct depth, no migration) - No articular penetration 4. **Closure**: - Fascia lata: 2-0 absorbable suture (close split in fibers) - Subcutaneous: 3-0 absorbable - Skin: 3-0 monocryl subcuticular OR staples 5. **Sterile compressive dressing** 6. **Postoperative imaging**: AP and lateral radiographs in recovery for documentation **Technical Tip**: "After decompression +/- adjuncts, I perform comprehensive final fluoroscopy check: appropriate depth (5mm safety margin on both AP and lateral), no iatrogenic fractures (neck, subtrochanteric, shaft), and graft/rod position if used. Small incision closed in anatomic layers. Postoperative X-rays document baseline for follow-up comparison and rule out complications. Bleeding is typically minimal due to avascular nature of AVN tissue." - Unrecognized femoral neck fracture (may be non-displaced, subtle on fluoroscopy) - Unrecognized subtrochanteric fracture at entry point - may present late - Graft or rod malposition discovered post-op - Hematoma formation (rare but can cause compartment syndrome if large) ## Postoperative Protocol ### Weight-Bearing Restrictions (CRITICAL for Success) **Rationale**: Reduce mechanical stress on weakened femoral head during revascularization phase (takes 3-6 months) **Standard Protocol**: - Weeks 0-6: Non-weight bearing (NWB) with crutches or walker - Weeks 6-12: Touch-down weight bearing (TDWB) - 10-20kg foot contact only - Weeks 12-16: Progressive weight bearing as tolerated - Month 4-6: Full weight bearing if X-rays stable (no collapse) **Alternative Protocol** (some centers): - Weeks 0-8: Touch-toe weight bearing (TTWB) throughout with crutches - Weeks 8-12: Gradual progression to full weight bearing **With Large Core or Adjunct Graft**: - Consider extended NWB to 8-12 weeks due to greater femoral neck weakening ### Rehabilitation Protocol **Phase 1 (Weeks 0-6): Protection Phase** - ROM exercises (supine): Hip flexion, abduction, external rotation - Ankle pumps and quad sets - Upper body and contralateral leg strengthening - Transfer training with NWB - Aquatic therapy (if available) - reduces load while maintaining ROM **Phase 2 (Weeks 6-12): Progressive Loading** - Continue ROM exercises - Begin hip strengthening (isometric first, then progressive resistance) - Core and pelvic stabilization - Proprioceptive training (single-leg balance once TDWB) - Gait training with assistive device **Phase 3 (Weeks 12-24): Functional Restoration** - Advanced strengthening (hip, core, lower extremity chain) - Sport-specific training (if appropriate) - Gradual return to impact activities after Month 6 if X-rays stable - Continue monitoring for pain or mechanical symptoms ### Imaging Follow-up **X-rays (AP pelvis + lateral hip)**: - 6 weeks: Check for fracture, early collapse - 3 months: Assess for progression - 6 months: Critical time point - most failures evident by now - 1 year: Long-term stability assessment - Annually for minimum 5 years: Late failures can occur up to 2-3 years **MRI (optional but informative)**: - 3-6 months: Assess revascularization - Success: Decreased marrow edema (lower T2 signal), resolution of double-line sign - Failure: Persistent or increased edema, progressive lesion size - MRI can predict outcome earlier than X-ray changes ### Medications **Thromboprophylaxis**: - Aspirin 100mg daily for 6 weeks OR - LMWH for 4-6 weeks (local protocol dependent) - Higher risk if NWB/immobility **Bisphosphonates** (consider for specific etiologies): - Steroid-induced AVN: Alendronate 70mg weekly or zoledronic acid 5mg IV annually - Evidence shows reduced progression risk - PBS coverage for steroid-induced AVN in Australia **Analgesia**: - Paracetamol regular for 2-4 weeks - NSAIDs cautiously (theoretical concern about bone healing, limit to 2 weeks) - Avoid narcotics if possible ## Outcomes & Prognostic Factors ### Success Definition - No radiographic progression to collapse (no crescent sign development, no flattening) - Pain improvement (VAS decrease ≥3 points) - Maintained joint space (no narrowing >1mm) - Return to desired activities - Avoiding arthroplasty at 5 years ### Success Rates (Evidence-Based) **By Ficat Stage**: - Stage I: 70-85% avoid arthroplasty at 5 years - Stage II: 50-70% - Stage III: 20-30% (most proceed to arthroplasty - core decompression not indicated) **By Lesion Size (Kerboul Angle)**: - <200°: 80-90% success - 200-250°: 50-70% - >250°: 30-40% **By Lesion Size (% of Head)**: - <15%: 80-85% success - 15-30%: 55-70% - >30%: 35-45% **Combined Stage + Size (Most Predictive)**: - Stage I + <15% lesion: 85-90% - Stage I + 15-30%: 60-75% - Stage I + >30%: 40-50% - Stage II + <15%: 70-80% - Stage II + 15-30%: 45-60% - Stage II + >30%: 30-40% **With Adjuncts**: - Tantalum rod (Stage II, medium lesions): 50-70% - Vascularized fibula (Stage II-III, large lesions): 70-90% ### Prognostic Factors **Good Prognosis**: - Early stage (Ficat I, ARCO I-II) - Small lesion (<15%, <200° Kerboul) - Young age (<40 years) - Non-weight bearing location (less common) - Compliance with protected weight-bearing protocol **Poor Prognosis**: - Advanced stage (Ficat IIC-III) - Large lesion (>30%, >250° Kerboul) - Anterosuperior weight-bearing location (most common) - Older age (>50 years) - Continued steroid use or alcohol consumption - Non-compliance with weight-bearing restrictions ### Failure Management **Recognition of Failure**: - Progressive collapse on X-ray (crescent sign development if not present initially, increasing flattening) - Joint space narrowing (>1mm loss) - Worsening pain despite initial improvement - Decreased ROM and function **Timing**: Most failures occur within 18-24 months post-op, but can occur up to 3-5 years **Salvage Options**: 1. **Total Hip Arthroplasty** (most common): - Standard treatment for failed core decompression - Good long-term outcomes but HIGH revision rate in young patients - AOANJRR: 25-30% revision at 10 years for AVN patients <55 years vs 5-7% for OA - Challenges: Young age, good bone stock, high activity demands 2. **Hip Resurfacing** (controversial): - Preserves bone stock - Concerns about bone quality in AVN - Higher failure rates than for OA patients - Not standard in Australia 3. **Vascularized Fibula Graft** (salvage attempt): - For very young patients (<35 years) with small-medium lesions who failed core decompression - 60-80% success as salvage in carefully selected cases - Buys time before inevitable THA 4. **Rotational Osteotomy** (transtrochanteric): - Rarely considered in Australia - Rotates defect away from weight-bearing zone - Only for small, contained anterosuperior lesions - Technically demanding, unpredictable outcomes ## Australian-Specific Data (EXAM ESSENTIAL!) ### AOANJRR Registry Data - Young AVN patients (<55 years) undergoing THA: 25-30% revision rate at 10 years - Comparison OA patients same age: 5-7% revision rate at 10 years - 4-5× higher revision risk justifies aggressive joint preservation attempts - Most common failure modes: Aseptic loosening, instability, fracture ### PBS (Pharmaceutical Benefits Scheme) - Alendronate covered for "corticosteroid-induced osteoporosis" (includes AVN prevention) - Zoledronic acid covered for similar indication - Requires minimum 3 months prednisolone ≥7.5mg daily (or equivalent) ### MBS Item Numbers - **49548**: Excision of bone, femur (includes core decompression) - $600-800 - **49318**: Bone graft to femoral head - additional $400-500 - Combined procedure typically $1000-1300 ### eTG (Therapeutic Guidelines) Antibiotic Prophylaxis - Cefazolin 2g IV at induction (single dose) - If penicillin allergy: Vancomycin 25-30mg/kg IV (over 1-2 hours pre-incision) ## References 1. Mont MA, Cherian JJ, Sierra RJ, et al. Nontraumatic Osteonecrosis of the Femoral Head: Where Do We Stand Today? A Ten-Year Update. *J Bone Joint Surg Am*. 2015;97(19):1604-1627. doi:10.2106/JBJS.O.00071 - Comprehensive review of AVN treatment including core decompression outcomes by stage and lesion size. Reports 60-85% success for Stage I-II depending on size. 2. Kerboul M, Thomine J, Postel M, et al. The conservative surgical treatment of idiopathic aseptic necrosis of the femoral head. *J Bone Joint Surg Br*. 1974;56(2):291-296. - Original description of Kerboul angle method for quantifying lesion size on imaging. Established prognostic value: <200° good, >250° poor outcomes. 3. Ficat RP. Idiopathic bone necrosis of the femoral head. Early diagnosis and treatment. *J Bone Joint Surg Br*. 1985;67(1):3-9. - Classic paper defining Ficat staging system (I-IV) for AVN based on radiographic findings. Stage I-II pre-collapse (core decompression candidates), Stage III-IV post-collapse. 4. Marker DR, Seyler TM, Ulrich SD, et al. Do modern techniques improve core decompression outcomes for hip osteonecrosis? *Clin Orthop Relat Res*. 2008;466(5):1093-1103. doi:10.1007/s11999-008-0184-9 - Systematic review showing core decompression superior to non-operative treatment. Success rates: Stage I 70-85%, Stage II 50-70%. Adjuncts (tantalum, fibula) improve medium-large lesion outcomes. 5. Zhao DW, Yu M, Hu K, et al. Prevalence of Nontraumatic Osteonecrosis of the Femoral Head and its Associated Risk Factors in the Chinese Population: Results from a Nationally Representative Survey. *Chin Med J*. 2015;128(21):2843-2850. doi:10.4103/0366-6999.168017 - Epidemiology showing 30-70% bilateral involvement in non-traumatic AVN. Emphasizes need to image and monitor contralateral hip. 6. Tanzer M, Bobyn JD, Krygier JJ, et al. Histopathologic retrieval analysis of clinically failed porous tantalum osteonecrosis implants. *J Bone Joint Surg Am*. 2008;90(6):1282-1289. doi:10.2106/JBJS.F.00847 - Analysis of tantalum rods for AVN showing tissue ingrowth through porous structure. Outcomes 50-70% success for Stage II medium lesions, similar to vascularized fibula but simpler technique. 7. Yoo MC, Kim KI, Hahn CS, et al. Long-term followup of vascularized fibular grafting for femoral head necrosis. *Clin Orthop Relat Res*. 2008;466(5):1133-1140. doi:10.1007/s11999-008-0204-9 - Long-term outcomes of vascularized fibula showing 70-90% success even in Stage III (post-collapse) disease. Donor morbidity: ankle stiffness 20-30%, peroneal nerve injury 5-10%. 8. Steinberg ME, Hayken GD, Steinberg DR. A quantitative system for staging avascular necrosis. *J Bone Joint Surg Br*. 1995;77(1):34-41. - Description of University of Pennsylvania/Steinberg staging (similar to ARCO) adding quantification to Ficat system. Emphasizes lesion size as prognostic factor. 9. Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Hip, Knee & Shoulder Arthroplasty: 2023 Annual Report. Adelaide: AOA; 2023. - Registry data showing AVN patients <55 years have 25-30% THA revision rate at 10 years vs 5-7% for OA patients. Justifies aggressive joint preservation attempts. 10. Therapeutic Guidelines Limited. Therapeutic Guidelines: Antibiotic. Version 16. Melbourne: Therapeutic Guidelines Limited; 2023. [eTG complete] - Australian antibiotic prophylaxis guidelines: Cefazolin 2g IV at induction for orthopaedic procedures. Vancomycin 25-30mg/kg for penicillin allergy.

Core Decompression - Femoral Head AVN

Core Decompression - Femoral Head AVN