import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Lateral femoral cutaneous nerve (LFCN)** - Most commonly injured (15-30% temporary). **Location**: Crosses field 20-40mm medial to TFL, variable anatomy, runs on deep TFL surface or in TFL-sartorius interval, exits pelvis near/lateral to ASIS **Protection**: Fascial incision lateral (over TFL belly not medial edge), identify if visible, gentle retraction, minimize traction time, some release intentionally **Femoral neurovascular bundle** - Catastrophic if injured (<1% but devastating quadriceps palsy). **Location**: Lies 40-60mm medial to interval, deep to iliopsoas and sartorius, at anterior hip capsule level **Protection**: Inferior acetabular retractor MUST be on bone (ischium/inferior rim) NEVER soft tissue, avoid aggressive medial retraction, visualize placement directly **Superior gluteal nerve** - Innervates TFL and abductors, risk if dissection extends proximal. **Location**: Exits greater sciatic notch 40-50mm proximal to GT tip, courses between gluteus medius/minimus, innervates TFL **Protection**: Limit proximal dissection beyond safe zone, avoid splitting TFL proximally, stay distal to GT tip +5cm during anterior dissection **Ascending branch lateral femoral circumflex artery** - Causes troublesome bleeding if not controlled. **Location**: Runs on anterior hip capsule, 10-20mm deep to TFL fascia, courses longitudinally along femoral neck, consistent finding **Protection**: Identify and cauterize/ligate early during capsular exposure, careful coagulation (avoid thermal LFCN injury), control before capsulotomy **Femoral artery and vein** - Catastrophic vascular injury if retractor malpositioned. **Location**: 40-60mm medial to interval, in femoral triangle deep to sartorius, palpable pulse in groin crease **Protection**: Mark femoral pulse pre-incision, incision 2-3cm lateral to ASIS (stays lateral to vessels), retractors on bone not soft tissue, maintain spatial awareness ## Indications ### Absolute Indications - Primary hip osteoarthritis requiring arthroplasty in patient suitable for supine positioning - Displaced femoral neck fractures in elderly (supine positioning advantage for fragile patients) - Bilateral THA same session (supine positioning allows both hips without repositioning) ### Relative Indications - Secondary arthritis (AVN, post-traumatic, inflammatory, DDH mild-moderate) - Obesity (BMI >35) - easier acetabular exposure from anterior vs posterior in obese (though wound complications higher) - Patient preference for muscle-sparing approach and no hip precautions - Previous posterior approach complications (if anterior soft tissues intact) ### Australian Context **Medicare MBS Items**: - 49318: Primary THA unilateral ($1,800+ benefit) - 49319: Primary THA bilateral same session ($2,400+ benefit) - 49324: Revision THA components ($2,200+ benefit) **AOANJRR Data (2023)**: - DAA usage increasing: 15-20% of primary THAs in Australia (vs 5-10% decade ago) - Revision rates comparable to posterior approach at 10 years (~5-6%) - Learning curve evident: higher revision rates in surgeons' first 50-100 cases ## Contraindications ### Absolute Contraindications - Active hip infection (require staged management) - Inadequate anterior soft tissue envelope (previous extensive anterior surgery, radiation, soft tissue deficiency) - Surgeon inexperience without supervision (steep learning curve, consider training/proctoring) ### Relative Contraindications - Severe DDH (Crowe III-IV) - acetabular and femoral exposure very difficult from anterior - Complex femoral deformity (severe varus, prior fracture malunion) - difficult to achieve femoral access - Ankylosed hip (unable to position for femoral exposure - consider posterior approach) - Severe hip flexion contracture (prevents femoral positioning - paradoxically difficult despite anterior access) - Morbid obesity (BMI >45) - wound complications high (3-8%), consider alternative approach or weight loss - Revision THA with posterior bone loss (difficult to address from anterior approach) ## Surgical Anatomy ### Internervous Plane - Smith-Petersen Interval **Lateral Side - Tensor Fascia Lata (TFL)**: - Innervation: Superior gluteal nerve (L4-S1) - Origin: Anterior iliac crest, ASIS - Insertion: Iliotibial band (ITB) → lateral tibial condyle (Gerdy tubercle) - Function: Hip abduction, flexion, internal rotation - Blood supply: Superior gluteal artery, LFCA ascending branch **Medial Side - Sartorius and Rectus Femoris**: - Sartorius innervation: Femoral nerve (L2-L4) - Rectus femoris innervation: Femoral nerve (L2-L4) - Sartorius: ASIS → pes anserinus (medial tibial metaphysis) - Rectus femoris: Direct head AIIS, Reflected head acetabular rim → patella via quadriceps tendon - Function: Hip flexion (both), knee extension (rectus) **True Internervous Plane**: - Between TFL (superior gluteal) and sartorius (femoral) - Different nerve roots: L4-S1 vs L2-L4 - Muscle-sparing: neither muscle violated (split between) - Contrast to posterior approach (divides short external rotators, may denervate) and lateral (splits abductors, risks superior gluteal nerve) ### Neurovascular Structures at Risk **Lateral Femoral Cutaneous Nerve (LFCN)**: - **Course**: Exits pelvis lateral to psoas, crosses iliacus, passes near/lateral to ASIS, runs obliquely across anterior thigh - **Relationship to surgical field**: Crosses 20-40mm medial to TFL, highly variable (5 anatomic variants described) - **Variants**: Subcutaneous (10%), within TFL (20%), between TFL and sartorius (60%), medial to sartorius (10%) - **Function**: Pure sensory - anterolateral thigh sensation - **Injury**: Meralgia paresthetica (numbness/dysesthesia lateral thigh) **Femoral Nerve**: - **Course**: Exits pelvis under inguinal ligament, lateral to femoral artery, 40-60mm medial to TFL-sartorius interval - **Protected by**: Iliopsoas anteriorly, sartorius superficially - **Branches**: Motor to quadriceps (devastating if injured), sensory to anterior thigh/medial leg (saphenous) - **At risk from**: Inferior acetabular retractor if placed in soft tissue (not on bone) **Ascending Branch LFCA**: - **Course**: Branch of profunda femoris, runs on anterior hip capsule longitudinally - **Location**: 10-20mm deep to TFL fascia, crosses femoral neck - **Clinical significance**: Causes troublesome bleeding if not controlled, consistent finding requiring cauterization ### Capsular Anatomy **Anterior Hip Capsule**: - Iliofemoral ligament (Y-ligament of Bigelow): Strongest hip ligament, AIIS → intertrochanteric line, prevents extension/external rotation - Capsule thinner anteriorly than posteriorly (facilitates DAA exposure) - **DAA advantage**: Posterior capsule preserved intact (provides stability, low dislocation rate <1%) ## Patient Positioning ### Standard OR Table Technique - Supine with operative hip at table edge - Allows hip hyperextension off edge during femoral preparation - Non-operative leg: abducted 30-45° (some use leg holder) - Both legs in sterile field (allows leg length comparison) - Assistant maintains femoral position during broaching - **Challenges**: Requires strong assistant, limited hyperextension, assistant fatigue ### Specialized DAA Table (Hana, PROfx, Medacta AMIS) - **Features**: Leg holders/boots, table extension section for hyperextension, split-leg configuration - **Advantages**: Hands-free femoral positioning, greater hyperextension range, reduced assistant requirements, easier fluoroscopy - **Learning curve**: Reduced by 30-50% with specialized table vs standard table - **Disadvantages**: Cost ($15,000-30,000), learning curve with table setup, boot/holder pressure risks (pad well) ### Fluoroscopy Setup - C-arm from contralateral side (allows AP pelvis view without repositioning) - Used for: Acetabular component position verification, stem alignment, trial reduction leg length - **DAA advantage**: Supine positioning easier for true AP pelvis (vs lateral position with pelvic rotation) ## Operative Sequence ### Superficial Dissection (Steps 1-4) 1. **Landmarks**: Palpate ASIS, AIIS, GT, femoral pulse 2. **Incision**: 2-3cm lateral + distal to ASIS, extend 8-12cm distally 3. **Fascia**: Incise TFL fascia laterally (over muscle belly) 4. **Interval**: Develop TFL-sartorius interval (internervous plane) ### Deep Exposure (Steps 5-7) 5. **Hip capsule**: Cauterize ascending LFCA, expose capsule 6. **Rectus release**: Optional if tight (improves acetabular view) 7. **Capsulotomy**: T, H, or box excision (most excise, no clear dislocation difference) ### Acetabular Work (Steps 8-9) 8. **Dislocation**: Anterior (opposite direction from posterior approach) 9. **Neck osteotomy**: Level from templating (typically 10mm above lesser trochanter) 10. **Retractor placement**: Superior (AIIS), inferior (ISCHIUM - critical on bone), lateral (GT) 11. **Acetabular prep**: Ream, position cup 40° inclination/15-25° anteversion (Lewinnek safe zone) ### Femoral Preparation (Steps 10-13) 12. **Femoral positioning**: HEADS mnemonic - Hyperextend, Externally rotate 90°, Adduct, Drop off table edge 13. **Canal preparation**: Box chisel entry, sequential broaching (in-line critical, varus common error) 14. **Trial reduction**: Supine allows direct leg length comparison (both legs same plane) 15. **Final components**: Insert stem (watch version 10-15° AF), head impaction, reduce ## Learning Curve Data **Case Volume to Proficiency**: - Femoral complications plateau: 20-50 cases (fractures, varus stems reduce) - Acetabular component positioning: 30-75 cases (safe zone placement consistent) - Operative time normalization: 50-100 cases (reaches 60-90min plateau) - LFCN injury: Remains 15-30% even with experience (anatomy variable, not technique-dependent) **Surgeon Training Recommendations**: - Formal training course with cadaveric lab (AAHKS, AANA DAA courses) - Proctored first 10-20 cases (experienced DAA surgeon supervising) - Consider specialized DAA table early (reduces learning curve 30-50%) - Patient selection early in curve: Avoid obese (BMI >35), muscular, complex deformity, osteoporotic - Video review and case debriefing **Transition from Posterior Approach**: - Experienced posterior approach surgeons: 30-50 cases to DAA proficiency - Acetabular work easier (familiar), femoral work challenging (opposite direction, positioning different) - Complication rates higher in learning curve (accept this, counsel patients) ## High-Quality Evidence **Randomized Controlled Trials (DAA vs Posterior)**: 1. **Barrett et al. (2013) - J Bone Joint Surg Am** - RCT: DAA vs posterior approach, 100 patients - Findings: DAA faster early recovery (6 weeks), no difference 1 year - Complications: LFCN injury 15% DAA vs 0% posterior - Conclusion: Short-term recovery advantage, no long-term difference 2. **Rykov et al. (2017) - Acta Orthop** - RCT: DAA vs posterior, 120 patients, 2-year follow-up - Findings: No difference pain, function, dislocation rates - Complications: LFCN injury 18% DAA, wound complications equal - Conclusion: No clinically significant difference at 2 years 3. **Mjaaland et al. (2019) - J Bone Joint Surg Am** - RCT: DAA vs lateral vs posterior, 300 patients - Findings: DAA faster early mobilization (days 1-3), equal at 3 months - Dislocation: <1% DAA, 2% posterior, 1% lateral (not statistically significant) - Conclusion: Minor early benefits, no sustained advantage **Meta-analyses**: 4. **Miller et al. (2018) - J Arthroplasty** - Meta-analysis: 15 RCTs, 1,556 patients - Dislocation: OR 0.37 favoring DAA (lower risk) - LFCN injury: OR 12.5 favoring posterior (DAA higher risk) - Conclusion: Trade-off - lower dislocation, higher LFCN injury 5. **Wang et al. (2018) - J Orthop Surg Res** - Meta-analysis: 21 studies, 3,400+ patients - Early function: DAA advantage 6 weeks, no difference 3-12 months - Complications: Femoral fracture slightly higher DAA (learning curve effect) - Conclusion: Short-term recovery benefit, long-term equivalence ## Australian Registry Data (AOANJRR 2023) **Usage Patterns**: - DAA: 15-20% of primary THAs nationally (increasing from 5-10% in 2015) - State variation: Higher in private hospitals (20-25%) vs public (10-15%) - Age group: More common in younger patients <65 years (marketing/"minimally invasive") **Revision Rates**: - 10-year cumulative revision rate: DAA 5.8% vs Posterior 5.4% vs Lateral 6.2% (not statistically significant) - Learning curve evident: Surgeons' first 50 DAA cases - revision rate 8.2% (higher than posterior 5.1%) - After 100 cases: DAA 5.2% vs Posterior 5.1% (equivalent) **Indications for Revision**: - DAA: Aseptic loosening (45%), dislocation (12%), infection (18%), fracture (15%), other (10%) - Posterior: Dislocation slightly higher (15%) in non-enhanced repair era - No approach superiority for any specific failure mode ## Australian Clinical Guidelines **PBS (Pharmaceutical Benefits Scheme) - DVT Prophylaxis**: - Rivaroxaban 10mg daily 10-14 days (PBS subsidized post-THA) - Apixaban 2.5mg BD 10-14 days (alternative) - LMWH if renal impairment (enoxaparin 40mg daily) **eTG (Therapeutic Guidelines) - Antibiotic Prophylaxis**: - Cefazolin 2g IV (3g if >120kg) pre-incision - MRSA risk: Add vancomycin 1.5g IV (or teicoplanin 800mg IV) - Penicillin allergy: Vancomycin 1.5g IV - Single dose (no prolonged post-op antibiotics unless specific indication) ### Step 1: Patient positioning supine on OR table, operative side at table edge Patient positioning supine on OR table, operative side at table edge: Standard OR table or specialized DAA table (allows hyperextension). Patient supine, operative hip at edge of table to allow extension/adduction for femoral exposure. Non-operative leg: abducted and slightly flexed (some tables have leg holder/split configuration). Both legs prepared into sterile field (allows comparison for leg length). Ensure ability to extend hip fully and adduct across midline (test before draping). Fluoroscopy access confirmed (C-arm from contralateral side for AP pelvis) **Technical Tip**: EXAM KEY: Supine positioning is major advantage of DAA - easier anesthesia (neuraxial possible vs GA preferred for lateral), easier patient positioning (vs lateral decubitus complexity), ability to assess leg length intra-operatively (both legs in same plane), patient comfort post-operatively. Table selection important: standard OR table works but specialized DAA table (Hana, PROfx) facilitates femoral exposure with hyperextension and adduction. Learning curve reduced with specialized table. Patient at table edge critical - allows hip extension off table edge during femoral preparation. - Inadequate hip positioning preventing femoral exposure (test hip extension/adduction before draping) - Pressure injuries from table/leg holders (pad boot/holders well, check pulses) - Contralateral leg injury (secure abducted leg, prevent excessive abduction stretch) ### Step 2: Palpate bony landmarks Palpate bony landmarks: ASIS, AIIS, greater trochanter, femoral artery: Mark ASIS (prominent anterior superior iliac spine). Palpate AIIS 20-30mm distal and medial to ASIS (rectus femoris direct head origin). Palpate greater trochanter laterally (reference for incision length). Palpate femoral artery pulse in groin crease (stay lateral to vessels). Internervous interval: 20-40mm lateral to femoral artery, corresponds to TFL-sartorius interval **Technical Tip**: EXAM KEY: Surface anatomy guides incision location and protects neurovascular structures. ASIS is key landmark - incision starts 2-3cm lateral and 2-3cm distal. Too medial risks LFCN and femoral vessels, too lateral makes acetabular exposure difficult. Obese patients: landmarks difficult to palpate, use fluoroscopy to identify ASIS and anterior acetabular rim before incision. Thin patients: landmarks prominent, easier identification. - Incision too medial (risk femoral vessels, LFCN injury increased) - Incision too lateral (difficult acetabular exposure, limits access) - Failure to mark femoral pulse (inadvertent vessel injury during deep dissection) ### Step 3: Skin incision Skin incision: start 2-3cm lateral and distal to ASIS, extend distally 8-12cm: Incision orientation: longitudinal (parallel to TFL/femoral shaft) or slightly oblique (toward lateral femoral shaft). Length 8-12cm for primary THA (can extend if needed). Incise through skin and subcutaneous fat. Identify and cauterize crossing superficial vessels. Expose fascia overlying TFL laterally and sartorius medially. Identify interval between muscles (slight depression between TFL and sartorius) **Technical Tip**: EXAM KEY: Incision starts 2-3cm lateral and 2-3cm distal to ASIS - consistent reproducible landmark. Too proximal (over ASIS) makes femoral exposure difficult, too distal (mid-thigh) makes acetabular exposure difficult. Length 8-12cm sufficient for primary THA in most patients (some experienced surgeons use smaller incisions 6-8cm, but standard is 8-12cm). Extensile if needed for complex primary or revision. Incision orientation: longitudinal (easier for beginners) vs oblique (claimed better cosmesis, follows Langer lines). Either acceptable. - Skin necrosis from excessive tension (undermining, careful closure) - Superficial vessel bleeding (identify and cauterize systematically) - Too small incision causing soft tissue trauma from retraction (extend if needed, no prizes for small scars) ### Step 4: Develop interval between TFL (lateral) and sartorius/rectus femoris (medial) Develop interval between TFL (lateral) and sartorius/rectus femoris (medial): Identify fascia overlying TFL laterally (shiny, thick). Incise fascia just lateral to TFL (over muscle belly, not medial edge where LFCN crosses). Bluntly develop interval between TFL (retract laterally) and sartorius/rectus femoris complex (retract medially). This is internervous plane (TFL = superior gluteal nerve, sartorius = femoral nerve). Interval relatively avascular, contains loose areolar tissue. Develop interval from superficial (subcutaneous) to deep (hip capsule). Protect LFCN which crosses field medially (runs on deep surface of TFL or in interval) - identify if visible (thin white nerve 2-3mm diameter), protect with gentle retraction or release if tethering **Technical Tip**: EXAM KEY: Internervous plane is major theoretical advantage of DAA - avoids denervating any muscles (TFL and sartorius both preserved, innervation intact). Contrast posterior approach (divides external rotators, may denervate some fibers) and lateral approach (splits abductors, risk of superior gluteal nerve injury). However, LFCN crosses this interval in most patients and is at risk (15-30% injury rate causing meralgia paresthetica). Some surgeons intentionally release LFCN to prevent traction injury, others preserve and protect with careful retraction. No consensus on superior approach. - LFCN injury (crosses field 20-40mm medial to TFL, variable anatomy, gentle technique) - Fascial incision too medial (direct nerve transection) - Excessive retraction force/duration (neuropraxia from traction) ### Step 5: Deepen dissection to hip capsule, release rectus femoris if needed for exposure Deepen dissection to hip capsule, release rectus femoris if needed for exposure: Continue blunt dissection deep between TFL (lateral) and sartorius/rectus (medial). Ascending branch of LFCA encountered on anterior capsule - identify and cauterize or ligate to prevent bleeding (runs longitudinally on capsule, 1-2mm diameter). Expose anterior hip capsule from acetabular rim (superiorly) to femoral neck (inferiorly). In muscular patients or tight hips, rectus femoris (direct head from AIIS, reflected head from acetabular rim) may obscure exposure - release direct head from AIIS with diathermy or sharp dissection, tag for later repair if desired. Reflected head usually left attached unless extensive acetabular exposure needed **Technical Tip**: EXAM KEY: Ascending LFCA on anterior capsule is consistent finding - must be cauterized/ligated or causes troublesome bleeding obscuring field. Don't be aggressive coagulating (thermal injury to LFCN possible). Rectus femoris release controversial: some surgeons routinely release direct head for exposure, others only if needed (tight muscular patients). Release improves acetabular visualization but adds step. If released, tag with suture for optional repair at closure (repair vs no repair - no clear evidence, most don't repair as functional deficit minimal). - LFCA bleeding (obscures field, control early with cautery/ligation) - Thermal injury to LFCN during LFCA cauterization (careful technique) - Inadequate capsular exposure (release rectus if needed for visualization) ### Step 6: Capsulotomy - T-shaped or H-shaped capsular incision for exposure Capsulotomy - T-shaped or H-shaped capsular incision for exposure: Perform capsulotomy to expose femoral head-neck junction and acetabular rim. Options: T-shaped (vertical incision along femoral neck, transverse at base), H-shaped (two vertical, connected by horizontal), or box/rectangular capsulectomy (excise anterior capsule). Tag capsular flaps with sutures if planning repair. Expose femoral head-neck junction (neck cut location) and anterior/superior acetabular rim. Some surgeons excise capsule (faster, no repair needed), others preserve for closure (theoretical stability benefit but no clear evidence) **Technical Tip**: EXAM KEY: Capsular management in DAA varies by surgeon preference. Options: preserve and repair (T or H shaped incisions, tag flaps, repair at closure), excise (remove anterior capsule, no repair - faster, less soft tissue in field). No clear evidence of dislocation difference - DAA has very low dislocation rate (<1%) regardless of capsular management, likely due to preserved posterior and inferior capsule + abductor integrity. Most surgeons excise for simplicity, some preserve theorizing improved stability and soft tissue coverage. Know your preference with rationale. - Inadequate capsulotomy (limits head delivery and acetabular exposure, extend if needed) - Capsular releases too extensive (posterior capsule violation reduces stability advantage) - Femoral vessel injury if capsulotomy extends too medially (stay anterior and lateral) ### Step 7: Dislocation and femoral neck osteotomy Dislocation and femoral neck osteotomy: Externally rotate leg, extend hip slightly, apply anterior force to femoral head (assistant or specialized retractors). Head should deliver anteriorly into wound with gentle force (if difficult, release more capsule or check for osteophytes). Perform femoral neck osteotomy using oscillating saw at predetermined level (templating: typically 10mm above lesser trochanter, adjust for head size and leg length plan). Cut perpendicular to neck axis or slightly oblique. Protect soft tissues with retractors. Remove femoral head with corkscrew or Kocher clamp. Measure head size, save head for autograft if needed **Technical Tip**: EXAM KEY: Anterior dislocation is different from posterior/lateral approaches (which dislocate posteriorly). Here, head delivers anteriorly into wound. Should require minimal force - excessive force risks fracture (femoral or acetabular). If difficult, release more capsule anteriorly and medially, remove osteophytes blocking dislocation. Neck cut level from templating - standard 10mm above lesser trochanter but individualize based on leg length goals and head size selection. Save head for autograft (posterior column/acetabular deficiency, offset augmentation). - Femoral or acetabular fracture from excessive dislocation force (gentle technique, release capsule if difficult) - Soft tissue injury from saw (protect with retractors) - Wrong neck cut level (check templating, measure twice, cut once) ### Step 8: Acetabular exposure with specialized retractors, protect femoral nerve medially Acetabular exposure with specialized retractors, protect femoral nerve medially: Place specialized retractors to expose acetabulum: 1) Anterior/superior retractor (double-pronged or curved blade) on anterior rim/AIIS area (retracts rectus and TFL superiorly), 2) Inferior retractor on inferior/medial rim (over obturator internus or ischium - careful placement, MUST be on bone not soft tissue to protect femoral nerve 40-60mm medially), 3) Lateral retractor on lateral rim/GT area (retracts femur and vastus). Confirm 360° rim visualization. Adequate retraction critical for reaming/cup placement - more difficult than posterior approach due to anterior access angle **Technical Tip**: EXAM KEY: Acetabular exposure is technical challenge of DAA - approaching from front vs posterior/lateral approaches from side/back. Retractors must be precisely placed to achieve 360° rim visualization while protecting femoral nerve medially. Inferior/medial retractor position is most critical - MUST stay on bone (ischium, inferior rim), never in soft tissue where femoral nerve lies. Over-aggressive medial retraction or soft tissue placement causes femoral nerve palsy (quadriceps weakness, catastrophic). Specialized retractor systems (Innomed, Thompson, Synvasive) facilitate exposure. Learning curve significant - DAA acetabular exposure harder than femoral. - Femoral nerve injury (inferior retractor on bone not soft tissue - CRITICAL) - Inadequate acetabular exposure (360° rim not visible, risk malposition) - Femoral vessel injury (retractor too medial in soft tissue) ### Step 9: Acetabular preparation Acetabular preparation: labrum excision, reaming, cup insertion (same as posterior approach): Remove labrum and osteophytes to expose true acetabular rim (transverse ligament marks inferior rim and fovea). Sequential reaming from small to final size (templated size), ream to bleeding subchondral bone (Christmas tree sign), medialize to anatomic center of rotation. Final reamer = cup size minus 1-2mm (press-fit). Insert cup at 40° ± 5° inclination, 15-25° anteversion (Lewinnek safe zone). Assess press-fit stability (scratch test, levering). Add screws if needed in safe zones (posterior-superior, anterior-superior). Insert liner, confirm locking **Technical Tip**: EXAM KEY: Acetabular preparation technique identical to posterior approach - same reaming, same cup positioning targets (40° inclination, 15-25° anteversion for Lewinnek safe zone), same press-fit principles. Difference is exposure/visualization (anterior access vs posterior access). Acetabular positioning may be easier in DAA (supine patient, fluoroscopy easier to obtain true AP pelvis vs lateral position accounting for pelvic tilt). However, rim visualization harder from anterior (especially posterior wall). Retractor placement critical. Cup anteversion assessment: use guides, anatomic landmarks, fluoroscopy, navigation if available. - Cup malposition (outside safe zone, increased dislocation/impingement risk) - Acetabular fracture (over-reaming, forceful cup impaction, check stability) - Medial wall perforation (ream to subchondral bone not through, avoid central reaming) ### Step 10: Femoral exposure Femoral exposure: hyperextend hip, externally rotate, adduct across midline: Release retractors from acetabulum. Position leg for femoral exposure: 1) Hyperextend hip (bring proximal femur anterior, hang leg off table edge or use table-mounted femoral elevator), 2) Externally rotate to 90° (brings posterior femur into wound), 3) Adduct across midline (relaxes soft tissues, improves access). Specialized DAA tables facilitate positioning with hyperextension and leg holders. Standard tables: assistant holds leg, or femoral elevator device hooks around proximal femur to lift. Goal: bring proximal femur anteriorly and superficially into wound for broaching **Technical Tip**: EXAM KEY: Femoral exposure is most technically challenging aspect of DAA - learning curve steep. Requires hip hyperextension (difficult on standard table, easier with specialized DAA table that allows table extension or has leg-drop feature), external rotation 90°, adduction. Patient positioning at table edge critical (hip can extend off edge). Elderly/stiff hips difficult to manipulate. Over-aggressive positioning risks femoral fracture (osteoporotic bone during forceful hyperextension/rotation). Retractors placed around proximal femur to elevate into wound: bent Hohmann, specialized femoral elevators. Goal: anteriorize proximal femur to allow in-line broaching along femoral axis. - Femoral fracture from forceful hyperextension/rotation (especially osteoporotic elderly, gentle technique) - Inadequate femoral exposure (leads to varus stem, anterior cortex perforation) - Soft tissue injury from aggressive retractor placement (gentler than acetabular retraction) ### Step 11: Femoral canal preparation Femoral canal preparation: open canal, sequential broaching to metaphyseal fill: Identify entry point on piriformis fossa or GT tip (depends on stem design: straight vs anatomic). Open canal with box chisel directed along femoral axis (slight anterior/lateral). Insert sequential broaches starting small, advance incrementally until achieve: 1) Rotational and axial stability, 2) Appropriate seating level vs neck cut, 3) Metaphyseal fill/cortical contact. Final broach size = final stem size. Version: control stem anteversion during broaching (typically 10-15° AF target, assess by knee position when broach stable) **Technical Tip**: EXAM KEY: Broaching technique same as posterior approach BUT access angle is different (anterior/superior to femoral canal vs posterior/lateral in posterior approach, lateral in direct lateral). In-line access to femoral canal is challenging - requires adequate hip hyperextension/external rotation/adduction. Difficult positioning risks: varus stem alignment (common DAA complication, inadequate proximal femoral elevation causes non-in-line broaching), anterior cortex perforation (broach direction too anterior), femoral fracture (forceful broaching in osteoporotic bone, inadequate femoral exposure causing levering). Fluoroscopy useful to confirm broach alignment (AP and lateral views). - Varus stem alignment (DAA-specific complication, ensure in-line access) - Anterior cortex perforation (trajectory too anterior, fluoroscopy helps) - Femoral fracture (incremental broaching, recognize resistance, gentle impaction) ### Step 12: Trial reduction Trial reduction: assess leg length, offset, stability with trial components: Insert trial stem and trial head (matched to final sizes). Reduce hip (bring leg back to neutral position: extension, neutral rotation). Assessment: 1) Leg length - compare to contralateral leg (both legs in same plane supine, easier than lateral position), use sterile ruler/calipers, measure from fixed pelvic landmark (ASIS or pubis) to medial malleolus, compare heel height, 2) Offset - assess abductor tension (firm not tight), 3) ROM - flexion 110°, IR/ER, 4) Stability - flexion 90° + IR (anterior approach stable in this position unlike posterior), extension + ER. Adjust if needed (head size, stem size/offset) **Technical Tip**: EXAM KEY: Trial reduction in supine position major advantage - both legs in same plane allows direct comparison for leg length (vs lateral position where contralateral leg down, pelvic tilt, difficult comparison). Use multiple methods: visual heel height, measurement from ASIS to malleolus, specialized leg length calipers, fluoroscopy. DAA stability profile different from posterior - stable in flexion/IR (unstable position for posterior approach), potentially less stable in extension/ER if anterior soft tissue disrupted, but overall dislocation rate very low <1% (preserved posterior capsule and abductors protective). - Leg length discrepancy (meticulous measurement, multiple methods, fluoroscopy) - Instability not recognized (check ROM systematically, flexion+IR and extension+ER) - Inadequate offset (causes limp, impingement, adjust with head/stem selection) ### Step 13: Final femoral component insertion, head impaction, reduction, stability check Final femoral component insertion, head impaction, reduction, stability check: Remove trial components. CEMENTLESS: clean canal, insert final stem in same trajectory/rotation as final broach, impact to predetermined level (usually flush with neck cut), confirm seating. CEMENTED: clean canal, dry, restrictor, cement gun retrograde pressurization, insert stem in doughy phase, hold position until polymerization. Insert final femoral head (clean/dry trunnion, align head, impact firmly until fully seated, check no gap). Reduce hip, confirm stable reduction with ROM testing **Technical Tip**: EXAM KEY: Stem insertion technique same as posterior approach (cementless press-fit vs cemented using modern third-generation technique). Challenges specific to DAA: achieving in-line stem insertion (requires adequate hyperextension/external rotation/adduction of hip - difficult positioning), confirming stem version (anteversion target 10-15° typically, assessed by knee/foot position when stem stable or fluoroscopy). Common DAA-specific complications: varus stem (inadequate femoral elevation, non-in-line access), anterior cortex perforation (trajectory too anterior), fracture (forceful impaction, levering). Fluoroscopy confirms seating and alignment. - Stem malposition (varus, excessive anteversion/retroversion) - Intra-operative fracture (gentle impaction, recognize resistance) - Inadequate stem seating (subsidence risk, confirm level vs neck cut) ### Step 14: Closure Closure: capsule (optional), TFL fascia, subcutaneous, skin, no drains usually: If capsule preserved: repair capsular flaps with absorbable suture (restore anterior capsular integrity). Most surgeons excise capsule and don't repair (low dislocation rate without capsular repair in DAA, posterior capsule intact provides stability). Close TFL fascia with absorbable suture (restore muscle envelope). Subcutaneous layer closure (2-0 Vicryl). Skin: staples or subcuticular suture. Drains: not routinely used in DAA (less soft tissue dissection vs posterior/lateral approaches, lower bleeding). Waterproof dressing **Technical Tip**: EXAM KEY: Capsular management varies - some preserve/repair (T or H capsulotomy closed), most excise and don't repair. Evidence: no difference in dislocation (DAA <1% with or without capsular repair due to preserved posterior structures and abductors). Drains: less commonly used in DAA vs posterior approach (smaller dissection, less dead space, lower bleeding). Close TFL fascia to restore anatomy. Layered closure reduces dead space. DAA wound complications higher in some series (wound drainage, dehiscence) especially in obese - meticulous closure important. - Inadequate hemostasis (causes hematoma, wound drainage, infection risk) - Fascial closure under tension (causes dehiscence, release more proximally/distally if needed) - Skin necrosis from tension (undermine if needed, consider delayed closure if severe tension) ### Step 15: Post-operative protocol Post-operative protocol: immediate mobilization, no hip precautions (DAA advantage): Post-operative advantages of DAA: 1) No formal hip precautions needed (preserved posterior capsule and abductors means flexion/adduction/IR not at-risk position unlike posterior approach), 2) Immediate mobilization (same-day PT, weight-bearing as tolerated if stable fixation), 3) Faster recovery (less pain, shorter LOS in some studies, quicker return to function - though evidence mixed). VTE prophylaxis, post-op XR (AP pelvis, lateral hip to confirm component position, assess for fracture), PT for gait training and strengthening **Technical Tip**: EXAM KEY: No hip precautions is theoretical advantage of DAA - preserved posterior soft tissues (capsule, external rotators, abductors) means low dislocation risk without restrictions. Patients allowed full flexion, adduction, IR from day 1 (vs traditional posterior approach precautions: no flexion >90°, no adduction, no IR). However, modern enhanced posterior repair also has very low dislocation (<2%) and some surgeons use no precautions even with posterior approach. Recovery speed: some studies show faster recovery with DAA (earlier mobilization, less pain, shorter LOS), others show no difference vs modern posterior approach by 6-12 weeks. Patient perception and marketing: DAA marketed as 'minimally invasive' and 'fast recovery' but evidence vs optimized posterior approach is mixed at best. - Inadequate VTE prophylaxis (rivaroxaban 10mg daily 10-14 days per PBS guidelines) - Dislocation from excessive ROM testing (rare <1% but check stability gently) - Wound complications (drainage, dehiscence - monitor closely especially obese patients) ## References 1. Barrett WP, Turner SE, Leopold JP. Prospective randomized study of direct anterior vs postero-lateral approach for total hip arthroplasty. J Arthroplasty. 2013;28(9):1634-1638. **RCT comparing DAA vs posterior approach, 100 patients, faster early recovery with DAA (6 weeks) but no difference at 1 year, LFCN injury 15% DAA vs 0% posterior** 2. Rykov K, Reininga IHF, Sietsma MS, Knobben BAS, Ten Have BLEF. Posterolateral vs Direct Anterior Approach in Total Hip Arthroplasty (POLADA Trial): A Randomized Controlled Trial to Assess Differences in Serum Markers. J Arthroplasty. 2017;32(12):3652-3658. **RCT DAA vs posterior, 120 patients, 2-year follow-up, no difference in pain/function/dislocation, LFCN injury 18% DAA** 3. Mjaaland KE, Svenningsen S, Fenstad AM, et al. Implant Survival After Minimally Invasive Anterior or Anterolateral vs Conventional Posterior or Direct Lateral Approach in Total Hip Arthroplasty: A Multicenter Randomized Controlled Trial. J Bone Joint Surg Am. 2019;101(13):1206-1214. **RCT comparing DAA vs lateral vs posterior, 300 patients, DAA faster early mobilization (days 1-3) but equal at 3 months, dislocation <1% all approaches** 4. Miller LE, Gondusky JS, Bhattacharyya S, Kamath AF, Boettner F, Wright J. Does Surgical Approach Affect Outcomes in Total Hip Arthroplasty Through 90 Days of Follow-Up? A Systematic Review With Meta-Analysis. J Arthroplasty. 2018;33(4):1296-1302. **Meta-analysis 15 RCTs, 1,556 patients, dislocation OR 0.37 favoring DAA (lower risk), LFCN injury OR 12.5 favoring posterior (DAA higher risk)** 5. Wang Z, Hou JZ, Wu CH, et al. A systematic review and meta-analysis of direct anterior approach versus posterior approach in total hip arthroplasty. J Orthop Surg Res. 2018;13(1):229. **Meta-analysis 21 studies, 3,400+ patients, early function advantage DAA at 6 weeks, no difference 3-12 months, femoral fracture slightly higher DAA (learning curve)** 6. Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Hip, Knee & Shoulder Arthroplasty: 2023 Annual Report. Adelaide: AOA; 2023. **Australian registry data showing DAA usage 15-20% of primary THAs nationally (increasing), 10-year revision rate 5.8% DAA vs 5.4% posterior (not significant), learning curve evident in first 50 cases (8.2% revision vs 5.1% posterior)** 7. Hartford JM, Bellino MJ. The learning curve for the direct anterior total hip arthroplasty: a single surgeon's first 500 cases. Hip Int. 2017;27(5):483-488. **Learning curve study showing operative time normalization after 50-100 cases (60-90min plateau), femoral complications decrease after 20-50 cases, acetabular positioning consistent after 30-75 cases** 8. Jewett BA, Collis DK. High complication rate with anterior total hip arthroplasties on a fracture table. Clin Orthop Relat Res. 2011;469(2):503-507. **Study showing higher complication rates (13%) in early DAA experience on fracture table including LFCN injury (30%), femoral fractures (4%), wound complications (5%), highlighting learning curve challenges** 9. Meneghini RM, Pagnano MW, Trousdale RT, Hozack WJ. Muscle damage during MIS total hip arthroplasty: Smith-Petersen versus posterior approach. Clin Orthop Relat Res. 2006;453:293-298. **Study comparing muscle damage between DAA (Smith-Petersen) and posterior approach using MRI and serum markers, showing less muscle damage with DAA (true internervous plane advantage)** 10. Post ZD, Orozco F, Dixit V, Purtill JJ, Ong A, Hozack WJ. Direct Anterior Approach for Total Hip Arthroplasty: Indications, Technique, and Results. J Am Acad Orthop Surg. 2014;22(9):595-603. **Comprehensive surgical technique review of DAA including indications, contraindications, step-by-step technique, danger zones (LFCN, femoral nerve), complications management, and learning curve recommendations**

Direct Anterior Approach Total Hip Arthroplasty (DAA THA)

Direct Anterior Approach Total Hip Arthroplasty (DAA THA)