import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Location**: 2-3cm medial to ASIS, runs with sartorius medially, purely sensory (L2-L3), variable branching pattern **Protection**: Incision 2-3cm distal/lateral to ASIS, identify nerve in subcutaneous fat, gentle medial retraction with sartorius, avoid excessive traction **Injury Rate**: 15-30% transient meralgia paresthetica, 5% permanent sensory loss lateral thigh **Location**: 3-5cm medial to anterior hip capsule, palpable femoral pulse marks medial boundary **Protection**: Palpate pulse pre-operatively, stay lateral to pulse, anterior retractors placed ON BONE (anterior acetabular rim, pubis), avoid blind medial retraction **Injury**: Catastrophic - femoral artery injury requires vascular surgery, nerve injury causes quadriceps paralysis and sensory loss **Location**: Exits sciatic notch 3-5cm proximal to greater trochanter, runs between gluteus medius and minimus **Protection**: Avoid proximal dissection above level of greater trochanter, stay in safe zone anterior to TFL, lateral retractors placed at femoral neck level **Injury**: Trendelenburg gait from abductor denervation (irreversible), bleeding from superior gluteal artery **Location**: 1.5-3cm posterior to hip joint, exits sciatic notch, runs between ischium and greater trochanter **Protection**: Avoid posterior dissection beyond posterior column, gentle posterior retractor placement, maintain hip flexion during acetabular work (relaxes nerve) **Injury**: Foot drop (common peroneal division), sensory loss posterior leg/foot, stretching injury during leg manipulation **Location**: 2-3cm distal to anterior hip capsule, runs deep to rectus femoris from MFCA/profunda femoris **Protection**: Identify during deep interval development, ligate/cauterize before capsular exposure **Injury**: Significant bleeding obscuring surgical field, retraction injury to accompanying motor branch to vastus lateralis ### Primary Indications **Primary Osteoarthritis (Most Common - 70%)** - Failed conservative management for 3-6 months (NSAIDs, physiotherapy, weight loss, activity modification, intra-articular corticosteroid) - Pain affecting quality of life, sleep disturbance - Radiographic evidence: joint space narrowing, osteophytes, subchondral sclerosis/cysts - Functional limitation affecting ADLs **Avascular Necrosis (AVN)** - Ficat/Arlet stage III-IV with femoral head collapse - Failed core decompression or vascularized grafting - Causes: corticosteroids, alcohol, SLE, post-traumatic, sickle cell, Gaucher's, idiopathic **Inflammatory Arthropathies** - Rheumatoid arthritis with joint destruction - Ankylosing spondylitis with hip ankylosis/severe restriction - Psoriatic arthritis, IBD-associated arthropathy **Femoral Neck Fractures (NOF)** - Displaced Garden III/IV in elderly (>65 years typically) - Failed fixation of femoral neck fracture - Non-union femoral neck fracture **Failed Previous Hip Surgery** - Failed hip preservation (PAO, femoral osteotomy, hip arthroscopy) - Failed hemiarthroplasty - Revision scenarios ### DAA-Specific Advantages - Patient Selection **Ideal Candidates for DAA** - Young active patients wanting rapid return to unrestricted activity - Bilateral hip disease requiring staged/simultaneous surgery - Patients at high risk for dislocation with posterior approach - Morbidly obese patients (debated - some prefer DAA for better deep exposure, others avoid due to LFCN injury risk) - Patients requiring accurate restoration of leg length/offset **Relative Contraindications to DAA** - Severe proximal femoral deformity (DDH with high dislocation, severe coxa vara) - Previous proximal femoral surgery with hardware in situ - Severe hip flexion contracture (cannot extend hip for femoral preparation) - Heterotopic ossification anteriorly - Surgeon inexperience (learning curve 30-100 cases) ### Preoperative Planning **Clinical Assessment** - ROM documentation (hip flexion contracture affects femoral exposure) - Leg length discrepancy measurement (true vs apparent) - Neurovascular examination (document baseline) - Assess for previous hip scars/surgery **Radiographic Templating** - AP pelvis (standard - include femoral heads, obturator foramina, iliac wings) - Lateral hip (cross-table or frog-leg) - Magnification marker (typically 20% magnification) - Template acetabular component (determine cup size, position) - Template femoral component (determine stem size, neck length, offset) - Identify leg length discrepancy (compare lesser trochanters, teardrops) **Special Investigations** - CT scan if complex deformity, DDH, previous fracture malunion - MRI if concern for AVN staging, soft tissue assessment - FBC, CRP, ESR if infection suspected - HbA1c for diabetics (optimize <7% ideally) **Examiner Expectation**: "How does patient positioning influence your approach selection for THR?" - Supine positioning in DAA allows accurate leg length assessment through direct comparison, facilitates intra-operative fluoroscopy for cup position verification, enables simultaneous bilateral surgery, and eliminates hip precautions postoperatively (key advantage over posterior approach requiring 6-week flexion/adduction/IR restrictions). ### Internervous Plane **True Internervous Interval** (Only approach to hip) - **Lateral**: Tensor fascia lata (TFL) - Superior gluteal nerve (L4-S1) - **Medial**: Sartorius - Femoral nerve (L2-L4) - **Deep**: Rectus femoris (reflected head) - Femoral nerve - **Advantage**: No muscle detachment or denervation, preserves all hip abductors/extensors/external rotators **Smith-Petersen Interval** (Historical) - Original description accessed hip between TFL and sartorius for fusion/drainage - Modified by numerous surgeons (Judet, Light, Keggi) for arthroplasty - Modern DAA evolved from these modifications with specialized retractors and tables ### Key Anatomical Structures - Layered Approach **Superficial Layer (Skin to Fascia)** - Skin and subcutaneous fat (variable thickness) - **LFCN** - emerges 2-3cm medial to ASIS, variable branching (3-6 branches), runs with sartorius - Fascia lata overlying TFL laterally - Sartorius fascia medially **Intermediate Layer (Muscle Interval)** - TFL (lateral) - fusiform muscle from ASIS to iliotibial band - Sartorius (medial) - strap muscle from ASIS to pes anserinus - Interval between TFL and sartorius - typically palpable groove - Rectus femoris deep - reflected head from anterior hip capsule, straight head from AIIS **Deep Layer (Vascular/Capsular)** - **Ascending branch LFCA** - 2-3cm distal to capsule, runs deep to rectus femoris - Branches from MFCA (medial femoral circumflex artery) or directly from profunda femoris - Hip joint capsule - thick anteriorly (iliofemoral ligament - Y ligament of Bigelow) - Zona orbicularis - circular fibers around femoral neck ### Neurovascular Relationships **Femoral Neurovascular Bundle** (3-5cm medial) - Femoral nerve (lateral), vein (middle), artery (medial) - "NAVEL" lateral to medial - Nerve gives motor branches to quadriceps - Artery palpable - marks medial boundary of safe dissection **LFCN** (Variable course) - Purely sensory from L2-L3 - Exits pelvis at/near ASIS (multiple anatomical variants) - Supplies lateral thigh sensation to knee level - Injured in 15-30% of DAA cases (transient), 5% permanent **Superior Gluteal Nerve** (3-5cm proximal to GT) - Exits sciatic notch above piriformis with superior gluteal artery - Runs between gluteus medius and minimus - Supplies gluteus medius, gluteus minimus, TFL - Injury causes Trendelenburg gait **Sciatic Nerve** (1.5-3cm posterior) - Exits sciatic notch below piriformis (90%) or through piriformis (10%) - Lies on posterior capsule initially - Risk of stretch injury during leg manipulation or retractor placement ### Osseous Anatomy **Acetabulum** - Transverse acetabular ligament (TAL) - inferior margin, guides version (~20° anteversion) - Anterior column - from iliac crest to pubic symphysis - Posterior column - from sciatic notch to ischium - Quadrilateral plate - medial wall **Proximal Femur** - Femoral head - spherical (40-60mm diameter typically) - Femoral neck - 125-135° neck-shaft angle, 10-15° anteversion - Greater trochanter - insertion of abductors and short external rotators - Lesser trochanter - insertion of iliopsoas, landmark for femoral neck cut - Calcar femorale - medial cortical thickening inferior to neck **High Yield**: "What makes DAA a true internervous approach?" - DAA is the ONLY approach to the hip that utilizes an internervous plane: TFL (superior gluteal nerve) and Sartorius (femoral nerve). Posterior approach detaches short external rotators (sciatic nerve), lateral approach splits/detaches gluteus medius (superior gluteal nerve). This theoretical advantage preserves innervation, though clinical significance debated. ### Step 1: Patient Positioning and Landmarks **Patient Position**: Supine on standard operating table OR radiolucent table with extension attachment. Pelvis secured with padded supports/posts to prevent rotation. Operative leg free to extend, externally rotate, and adduct off side of table. Non-operative leg abducted 30-40° in leg holder or support. Entire operative limb prepped from iliac crest to mid-tibia. **Key Landmarks**: Palpate and mark ASIS, greater trochanter (GT), femoral pulse (medial boundary). Measure distance from ASIS to GT - typically 10-12cm. Plan incision 2-3cm distal and lateral to ASIS. **Table Setup**: C-arm from contralateral side if using intra-operative imaging. Mayo stand on operative side. Ensure table breaks allow hip extension or use extension attachment/fracture table configuration. **Positioning Checks**: Confirm pelvis level with C-arm (if available) - rotation causes leg length error and cup malposition. Test leg mobility - hip must extend, externally rotate, and adduct for femoral exposure. **Technical Mastery**: Supine positioning is fundamental DAA advantage: (1) Accurate leg length assessment through direct comparison, (2) Easy intra-operative fluoroscopy for cup verification, (3) Facilitates bilateral cases, (4) Gravity-assisted femoral exposure with leg off table. Pelvic rotation is enemy of accuracy - must ensure level pelvis. - Pelvic tilt/rotation (causes cup malposition and leg length discrepancy) - Inadequate table configuration (inability to extend hip for femoral exposure = abort case) - Contralateral leg not cleared (blocks hip adduction for femoral prep) - Insufficient fluoroscopy access (inability to verify position intra-operatively) ### Step 2: Skin Incision and Superficial Dissection **Incision**: Longitudinal or slightly oblique incision beginning 2-3cm distal and lateral to ASIS, extending 8-12cm distally (parallel to line from ASIS to lateral patella). Smaller incisions possible with experience (6-8cm), but adequate exposure essential early in learning curve. **Subcutaneous Dissection**: Deepen through subcutaneous fat to fascia. Identify LFCN in fat - typically medial aspect of incision, running with sartorius. Variable branching pattern (identify main trunk and branches). If nerve visible, protect with vessel loop or gentle medial retraction. If not visible, careful medial retraction of sartorius usually protects nerve. **Fascial Layer**: Identify palpable interval between TFL (lateral - firmer, more vertical) and sartorius (medial - softer, more oblique). May be filled with fat and loose areolar tissue. **Avoiding Most Common Complication**: LFCN injury occurs in 15-30% (transient) and 5% (permanent). Prevention: (1) Incision 2-3cm distal/lateral to ASIS (not directly over ASIS where nerve branches), (2) Identify nerve in subcutaneous fat if visible, (3) Gentle medial retraction with sartorius (nerve runs with sartorius), (4) Avoid excessive traction. Counsel patients pre-operatively about temporary numbness risk. - LFCN injury (most common complication) - causes meralgia paresthetica - Incision too medial (endangers femoral neurovascular bundle) - Incision too lateral (difficult interval, may violate TFL muscle belly) - Inadequate incision length (limits deep exposure, increases retraction injury risk) ### Step 3: Deep Interval and Fascial Division **Fascial Incision**: Incise fascia in interval between TFL (lateral) and sartorius (medial). Use finger dissection to develop plane - blunt dissection safer than sharp (protects LFCN, vascular structures). **Rectus Femoris Identification**: Deep to interval lies rectus femoris. Two heads: (1) Reflected head from anterior hip capsule (superior), (2) Straight head from AIIS (anterior). Expose anterior surface of rectus femoris. **LFCA Management**: Identify ascending branch of lateral femoral circumflex artery (LFCA) - typically 2-3cm distal to hip capsule, runs DEEP to rectus femoris, easily palpable pulsatile vessel. Ligate/cauterize vessel with bipolar or ties. Failure to control LFCA results in troublesome bleeding throughout case. **Interval Development**: Retract TFL laterally with deep retractor, sartorius and rectus femoris medially. Release reflected head of rectus femoris from superior capsule if needed for exposure (improves access to superior acetabular rim). **Vascular Landmark**: Ascending branch LFCA is critical landmark - lies 2-3cm distal to anterior hip capsule, runs under rectus femoris. MUST identify and ligate early (before capsular exposure) to prevent bleeding. Arises from MFCA or directly from profunda femoris. Motor branch to vastus lateralis often accompanies vessel - preserve if possible. - LFCA bleeding if not identified/ligated (obscures field throughout case) - Femoral nerve injury with aggressive medial retraction (stay on bone) - Superior gluteal nerve injury if dissection too proximal (above GT level) - Damage to motor branch to vastus lateralis (accompanies LFCA) ### Step 4: Capsule Exposure and Capsulotomy **Capsule Visualization**: Sweep periosteum and soft tissue off anterior hip capsule with periosteal elevator and retractors. Capsule typically thick (iliofemoral ligament - Y ligament of Bigelow). **Retractor Placement**: (1) Lateral retractor over femoral neck (protects abductors), (2) Medial retractor over anterior acetabular rim/pubis (protects femoral neurovascular bundle - MUST be on bone), (3) Superior retractor if needed (avoid proximal dissection). **Capsulotomy Pattern**: T-shaped (longitudinal + transverse) or H-shaped capsulotomy for maximum exposure. Extend longitudinal limb along femoral neck. Release anterior capsule generously - tight capsule severely limits exposure and increases fracture risk. **Superior Capsule Release**: Release reflected head of rectus femoris from superior capsule for improved visualization of superior acetabular rim (important for accurate cup positioning). **Capsular Release = Safe Femoral Exposure**: Adequate capsular release is ESSENTIAL for safe femoral exposure (most challenging DAA step). Tight anterior capsule limits hip extension and femoral visualization, dramatically increasing periprosthetic fracture risk. Be generous with anterior capsular release. Most surgeons do NOT repair capsule at closure (posterior capsule preservation provides stability). - Inadequate capsular release (poor femoral visualization = high fracture risk) - Femoral nerve injury with medial retractor (must stay on bone) - Abductor injury with lateral retractor if placed too posterior/superior - Vascular injury if medial retractor slips off bone into femoral vessels ### Step 5: Femoral Neck Osteotomy **Neck Visualization**: With capsule open, visualize femoral head and neck. Identify junction of head and neck, lesser trochanter (landmark for cut level). **Osteotomy Level**: Standard femoral stem - cut approximately 1cm ABOVE lesser trochanter. High-offset stems may require different level (check templating). Mark level with electrocautery or marking pen. **Osteotomy Execution**: Use oscillating saw for controlled cut. Protect posterior structures with retractor while sawing. Angle cut to match templated stem anteversion (typically 10-15°). **Head Removal**: Place corkscrew extractor into femoral head. Remove head with gentle rocking/twisting motion. Protect acetabular rim with retractor during extraction. **Head Disposition**: Send head for cultures (always - even primary OA), histology, and use for trial cup sizing (femoral head diameter approximates cup outer diameter minus wall thickness ~8-10mm). **Neck Osteotomy Precision**: Cut level determines offset and leg length. Standard cut = 1cm above lesser trochanter for most cementless stems. Too high = reduced offset (abductor dysfunction, instability); Too low = difficulty seating stem (subsidence risk, may require shortening osteotomy). Send head for cultures even in primary OA (pre-existing infection 0.5-1%, must exclude before implanting). - Cut too high (inadequate offset, leg shortening, abductor dysfunction) - Cut too low (stem insertion difficulty, subsidence risk, fracture risk) - Posterior acetabular wall fracture during head extraction - Periprosthetic fracture if head extraction requires excessive force ### Step 6: Acetabular Exposure and Preparation **Retractor Configuration**: Three-retractor setup: (1) Anterior over pubis/anterior rim, (2) Lateral over femoral neck stump, (3) Posterior under neck stump protecting posterior column. Retractors must be on bone (especially medial/anterior to protect femoral vessels). **Labrum Excision**: Remove acetabular labrum circumferentially with electrocautery or rongeur. Complete labrum removal essential for proper cup seating and visualization of acetabular rim. **Anatomical Landmarks**: Identify transverse acetabular ligament (TAL) - marks inferior acetabular rim and native version (cup parallel to TAL = ~20° anteversion). Identify anterior/posterior walls, floor (medial wall), superior rim. **Soft Tissue Clearance**: Remove pulvinar (fat pad) from acetabular floor with curette. Clear all soft tissue from acetabulum - residual tissue causes proud cup, reduced bone contact, or impingement. **Osteophyte Removal**: Remove peripheral osteophytes with osteotome or rongeur (especially anteroinferior and posteroinferior) - interfere with cup seating and cause impingement. **TAL = Version Reference**: Transverse acetabular ligament is critical anatomical landmark - marks inferior rim and provides reliable reference for native version. Cup oriented PARALLEL to TAL approximates 15-25° anteversion (normal native version ~20°). Alternative reference in DAA: anterior pelvic plane (APP) - reliably oriented in supine position, cup parallel to APP = ~20° anteversion. - Posterior wall fracture with posterior retractor (stay below equator) - Femoral neurovascular injury if anterior retractor off bone - Inadequate labrum/soft tissue clearance (proud cup, poor contact, impingement) - Loss of TAL during labrum excision (lose version reference) ### Step 7: Acetabular Reaming **Starting Reamer**: Begin 2-4mm smaller than templated cup size. Center reamer on acetabular floor (avoid eccentric reaming). **Reaming Technique**: Ream to subchondral bone - look for "bleeding dot sign" (punctate bleeding from healthy bone). Progressive reaming in 1-2mm increments until achieving good peripheral rim fit. **Final Reamer Size**: Ream to size 1-2mm SMALLER than intended cup for press-fit (line-to-line fit). Example: final reamer 52mm = cup 54mm. **Reaming Orientation**: Target Lewinnek safe zone - 40° inclination (30-50°), 20° anteversion (10-30°). Use anatomical references: TAL for version, lateral acetabular wall for inclination. Intra-operative fluoroscopy confirms position. **Depth Assessment**: Avoid excessive medial reaming (weakens floor, risks protrusio, intrapelvic perforation). Ream to bleeding subchondral bone, not through floor. Acetabular depth approximately 25-30mm in normal hip. **Rim Coverage**: Assess bone coverage after reaming - need 70-80% rim contact for stable press-fit. Consider jumbo cup, medialization, or augments if inadequate coverage. **Reaming Strategy**: "Ream until you see the dots" - bleeding dot sign indicates healthy subchondral bone contact. Final reamer 1-2mm SMALLER than cup = optimal press-fit (0.5-1mm interference). Avoid excessive medial reaming (weakens floor, risks intrapelvic perforation especially in elderly osteoporotic bone or RA with protrusio). Target 40/20 (inclination/anteversion) using TAL or APP as reference. - Excessive medial reaming (floor fracture, protrusio, intrapelvic perforation) - Under-reaming (inadequate cup fixation, micromotion, loosening) - Over-reaming (reduced bone contact, rim fractures, loosening) - Posterior wall fracture during reaming (most common acetabular fracture) ### Step 8: Acetabular Cup Insertion **Cup Selection**: Choose cup 1-2mm LARGER than final reamer for press-fit. Ensure correct liner option available (constrained if instability concern, dual-mobility in high-risk patients). **Cup Orientation**: Align inserter to target position - 40° inclination, 20° anteversion. Use references: TAL, APP, fluoroscopy. DAA advantage: supine position allows reliable use of APP and easy fluoroscopy. **Cup Impaction**: Impact cup with firm, progressive mallet strikes. Cup should advance into bone with each strike. Final position: fully seated against rim, no rocking/micromotion with trial liner inserted. **Stability Assessment**: Insert trial liner, check for micromotion. Stable cup = no movement with trial liner toggled. Micromotion indicates inadequate press-fit - add screws. **Screw Fixation**: Indications for screws: (1) Poor bone quality (osteoporosis, RA, AVN), (2) Large cup (>60mm), (3) Inadequate press-fit, (4) Dysplasia, (5) Revision setting. Safe zone for screws: 10 o'clock to 2 o'clock on right hip (2 o'clock to 10 o'clock left hip) - posterosuperior quadrant. AVOID anteroinferior (iliac vessels) and posteroinferior (sciatic nerve). **Position Verification**: Check cup position with fluoroscopy (AP and lateral views). Verify inclination, anteversion, depth, absence of protrusion. **Cup Fixation Principles**: Press-fit requires 1-2mm cup-bone interference (final reamer 52mm = cup 54mm). Screws augment fixation but don't substitute for inadequate press-fit. Safe screw zone = posterosuperior quadrant (10-2 o'clock right hip) avoiding vessels anteroinferiorly and sciatic nerve posteroinferiorly. DAA supine positioning facilitates intra-operative imaging for position verification before femoral preparation. - Cup malposition (excessive anteversion >30° or inclination >50° = instability risk) - Medial wall fracture during impaction (elderly/osteoporotic bone) - Screw penetration anteroinferiorly (external iliac vessels) or posteroinferiorly (sciatic nerve) - Inadequate press-fit (micromotion, early loosening, squeaking) ### Step 9: Femoral Exposure (Most Challenging Step) **Hip Positioning**: CRITICAL step requiring adequate hip extension and external rotation. Flex hip 30-45°, then extend by: (1) Bringing operative leg OFF side of table (standard table), OR (2) Using table extension/fracture table attachment. **Capsular Release Check**: Ensure adequate anterior capsular release from Step 4. Inadequate release = impossible femoral visualization = high fracture risk. Release more capsule if needed including posterior capsule. **Leg Position**: Goal position - hip EXTENDED (0-10° extension), externally rotated 30-45°, slightly adducted. Assistant holds leg or use positioner. Gravity assists with retraction. **Retractor Placement**: (1) Lateral retractor (protects gluteus medius/TFL), (2) Medial retractor (elevates iliopsoas), (3) Anterior retractor (retracts vastus lateralis). Specialized bent femoral elevators crucial for exposure. **Proximal Femur Visualization**: Must see greater trochanter, femoral neck osteotomy site, and proximal femoral shaft. If visualization inadequate - release more capsule, adjust leg position, consider different retractors. DO NOT PROCEED if cannot see proximal femur clearly. **Learning Curve Reality**: Femoral exposure is most technically challenging DAA step. Requires: (1) Adequate table configuration allowing extension, (2) Complete capsular release, (3) Correct leg positioning, (4) Appropriate retractors, (5) Experience. Learning curve 30-100 cases. Periprosthetic fracture rate 2-5% early in learning curve, reduces to 0.5-1% with experience. Know when to abort to lateral/posterior approach if unsafe. - Periprosthetic femur fracture (most serious DAA complication, 2-5% learning curve, <1% experienced) - Abductor injury with lateral retractor (gluteus medius avulsion from GT) - Vastus lateralis injury with anterior retractor - Inability to visualize femur (abort to different approach if unsafe - patient safety priority) ### Step 10: Femoral Canal Preparation **Canal Opening**: Use femoral elevator/canal finder to locate canal entry. Entry point medial aspect of greater trochanter in line with femoral shaft axis. **Box Chisel**: Remove calcar bone with box chisel to achieve proper varus-valgus alignment and prepare for broach entry. Remove sufficient medial bone for broach to sit in neutral-to-slight-valgus (avoid varus position). **Broaching**: Start with small broach (typically 2-4 sizes smaller than templated). Progressive broaching with increasing sizes. Broach orientation: 10-15° anteversion (align with femoral neck version), slight valgus alignment. **End Point**: Broach until achieving "cortical chatter" - palpable vibration transmitted through broach handle indicating metaphyseal cortical contact. Broach should seat to planned depth (typically calcar fully contacted). **Assessment**: Final broach should be stable without excessive impaction force. Assess broach depth, version (10-15° anteversion), varus-valgus alignment (neutral to slight valgus). Check for cortical perforation (feel for false passage, check medial/lateral cortices). **Broaching Technique**: "Broach until it chatters" - cortical chatter indicates good metaphyseal fit (essential for cementless stem stability). Entry point = medial aspect GT, alignment = slight valgus (NOT varus), version = 10-15° anteversion. Broach depth determines final stem position. Vancouver fracture risk highest during broaching - gentle progressive impaction, check for cortical perforation, adequate bone quality assessment. - Periprosthetic fracture (most common during broaching, 2-5% in learning curve) - Varus malalignment (subsidence, thigh pain, early loosening) - Cortical perforation (weakens bone, stress riser for fracture) - Undersized stem (subsidence, loosening, instability) - Oversized stem (fracture during insertion) ### Step 11: Trial Reduction and Assessment **Trial Assembly**: Insert trial stem matching final broach size. Insert trial head (start with +0 or templated neck length). **Hip Reduction**: Reduce hip by bringing femur anterior and flexing while stabilizing pelvis. Should reduce with gentle force (difficult reduction suggests oversized components or malposition). **Stability Testing**: Test through full ROM with specific attention to at-risk positions: - Flexion 110-120° + adduction + internal rotation (posterior dislocation position) - Extension + external rotation (anterior dislocation position - rare in DAA) - Hip should be STABLE without excessive reduction force **Leg Length Assessment**: DAA advantage - supine position allows accurate comparison. Measure from fixed pelvic landmark (ASIS, iliac crest) to medial malleolus bilaterally. Compare with pre-operative measurement and contralateral side. Target: equal or 5mm lengthening (patients tolerate slight lengthening better than shortening). **Offset Assessment**: Adequate offset = proper abductor tension. Test: anterior superior iliac spine to greater trochanter distance should approximate contralateral side or match templating. **ROM Assessment**: Check ROM - flexion 110-120°, extension 10-20°, abduction 45°, adduction 30°, IR/ER 45°. Assess for impingement (bone-on-bone or prosthetic impingement). **Adjustments**: If unstable/incorrect length/inadequate offset - adjust head size/neck length (increases/decreases offset and length), change cup position if necessary (rare), downsize stem if excessive offset. **Trial Reduction Critical Assessment**: Four priorities: (1) STABILITY - test in flexion/adduction/IR (posterior risk position), should be stable without excessive reduction force. (2) LEG LENGTH - supine advantage for accurate assessment, target equal or +5mm. (3) OFFSET - adequate abductor tension, match templating. (4) ROM - no impingement. Adjust with head size/neck length. DAA dislocation rate 0.5-2% (lower than posterior 2-5%) due to posterior capsule preservation. - Leg length discrepancy (most common patient complaint and medicolegal issue) - Instability (inadequate assessment leads to postop dislocation) - Inadequate offset (limp, abductor fatigue, impingement) - Unrecognized impingement (squeaking, accelerated wear, instability) ### Step 12: Final Component Insertion **Trial Disassembly**: Dislocate trial components. Remove trial head, extract trial stem with slap hammer. **Liner Insertion**: Insert definitive liner into acetabular shell. Most liners use Morse taper - must hear loud "SNAP" or "CLICK" confirming full seating. Some systems have secondary locking mechanism - ensure engaged. Verify liner fully seated (no gap between liner and shell). **Femoral Canal Final Prep**: Clean canal thoroughly with suction and brush. Irrigate canal. Dry with suction and gauze/swabs (critical for cementless fixation - moisture prevents bone ingrowth). Inspect canal for loose bone fragments. **Stem Insertion**: Insert final stem using stem inserter aligned to planned version (10-15° anteversion). Progressive impaction with mallet. End point: stem seated to level 1-2mm PROUD of final broach position (subsides ~1-2mm during final impaction). Check seating against calcar landmark. **Head Application**: CRITICAL for preventing taper corrosion. (1) Clean head bore and stem taper with gauze (remove ALL debris, fluid). (2) Ensure completely DRY. (3) Align head to planned version. (4) Firmly impact head onto taper - 12mm taper requires 5-6 firm strikes, larger tapers require more impacts. Inadequate impaction = taper micromotion = fretting corrosion = trunnionosis. **Component Assembly Technique**: Liner seating MUST achieve audible SNAP (Morse taper engagement) - unseated liner causes dislocation or liner fracture. Stem typically seats 1-2mm PROUD of broach (subsides during impaction). Head-taper junction CRITICAL - clean both surfaces, ensure DRY, FIRM impaction (12mm taper = 5-6 strikes minimum). Inadequate head impaction causes taper fretting corrosion (trunnionosis) leading to ALTR or dissociation. - Liner malseating (catastrophic - dislocation or liner fracture) - Stem subsidence (inadequate impaction or undersized stem) - Periprosthetic fracture during final stem impaction - Head malseating (inadequate taper engagement = corrosion, ALTR, dissociation) ### Step 13: Final Reduction and Comprehensive Assessment **Hip Reduction**: Reduce hip by bringing femur anterior with traction and flexing. Should reduce with gentle manipulation (resistance suggests oversizing or malposition). **Range of Motion Testing**: Perform complete ROM assessment: - Flexion 110-120° - Extension 10-20° - Abduction 45° - Adduction 30° - Internal rotation 45° (in flexion and extension) - External rotation 45° (in flexion and extension) **Stability Testing**: Critical final check - test in all at-risk positions: - Combined flexion + adduction + IR (posterior dislocation - most common position) - Extension + external rotation (anterior dislocation - rare in DAA) - Pure flexion >120° (anterior impingement check) - Pure extension (posterior impingement check) **Clinical Measurements**: Final leg length assessment - measure bilaterally from fixed pelvic point to medial malleolus. Compare with pre-operative measurements. Document any discrepancy. **Imaging Confirmation**: Intra-operative fluoroscopy (if available) - AP pelvis confirms cup position (inclination, no protrusion), lateral confirms version. AP femur confirms stem position, rules out fracture. **Impingement Assessment**: Bring hip through combined movements looking for bone-on-bone or prosthetic impingement. Impingement causes squeaking, accelerated wear, instability. **Final Stability Gold Standard**: DAA dislocation rate 0.5-2% (superior to posterior approach 2-5%) due to posterior capsule and short external rotator preservation. However, MUST verify stability intra-operatively. Test combined flexion/adduction/IR with axial load (posterior dislocation position) - hip should remain stable without excessive force. Extension/ER testing less critical in DAA (anterior dislocation rare). Document ROM and stability in operative note. - Inadequate stability testing (dislocation in recovery room or during mobilization) - Unrecognized leg length discrepancy (patient dissatisfaction, gait abnormality, medicolegal) - Missed fracture (if not using fluoroscopy) - Unrecognized impingement (long-term squeaking, wear, or instability) ### Step 14: Wound Closure **Copious Irrigation**: Irrigate wound with minimum 6-9 liters pulsatile lavage (reduces infection risk). Include deep intervals, capsular space, superficial tissues. **Capsular Management**: Most surgeons perform NO capsular repair or minimal repair in DAA (posterior capsule intact provides stability). If repairing, use absorbable suture to close anterior capsule. **Fascial Closure**: Close fascia between TFL and sartorius with interrupted or running absorbable suture (#1 Vicryl or equivalent). Ensure adequate strength (prevents hernia or muscle dehiscence). **Subcutaneous Closure**: Close subcutaneous layer with absorbable suture (2-0 or 3-0 Vicryl) to eliminate dead space and reduce seroma/hematoma. **Skin Closure**: Surgeon preference - staples (faster, traditional) or subcuticular absorbable suture (better cosmesis). Ensure skin edges well-approximated. **Drainage**: CONTROVERSIAL - most current evidence shows drains provide NO benefit and may INCREASE infection risk. Consider drain only if: (1) Significant oozing despite hemostasis, (2) Large dead space, (3) Anticoagulated patient with high bleeding risk. If using drain, remove within 24 hours. **Dressing**: Absorbent dressing, consider negative pressure wound therapy if high risk (obese, diabetic, immunosuppressed). **Drain Controversy**: Multiple RCTs and meta-analyses show drains do NOT reduce hematoma or infection in primary THR and may INCREASE infection risk (bacterial retrograde migration). Current best practice: NO ROUTINE DRAINS. Reserved for exceptional circumstances (ongoing ooze despite hemostasis, large dead space). If drain used, remove <24 hours. AOANJRR data confirms infection rate with drains numerically higher. - Inadequate hemostasis (hematoma formation, increased infection risk) - Weak fascial closure (muscle dehiscence, hernia) - Wound dehiscence (especially in obese patients, diabetics) - Drain-related infection if drain retained >24 hours ### Step 15: Postoperative Protocol and Follow-up **Day 0 (Day of Surgery)** - Mobilize with physiotherapy same day (early mobilization reduces DVT, improves outcomes) - Weight bearing as tolerated (WBAT) - NO restrictions - NO HIP PRECAUTIONS (key DAA advantage - posterior approach requires 6 weeks avoiding flexion >90°, adduction, IR) - Gait training with walking frame or crutches - DVT prophylaxis per protocol (LMWH, DOAC, or mechanical) **Day 1-2** - Continue mobilization - stairs training if needed - Discharge home if medically stable, adequate mobility, safe home environment - Walking aids: frame or crutches initially, progress to stick as able **Week 2** - Wound check in clinic or community - Suture/staple removal - Progress from frame to crutches to stick as mobility improves **Week 6** - X-ray check: AP pelvis, lateral hip - Assess component position, rule out fracture, check for radiolucent lines - Clinical assessment: wound, ROM, gait, leg length, stability - Progress activity - return to driving if safe (right hip - ensure can perform emergency stop) **Month 3** - Return to low-impact sports (golf, swimming, cycling) - Return to work for most patients (sedentary/light duties) **Month 6** - Return to impact sports if desired (running, tennis - controversial, not universally recommended) - Heavy manual work **Year 1 and Beyond** - Annual review with X-ray (years 1, 3, 5, 10, then every 5 years) - AOANJRR data: 10-year revision rate primary OA THR ~5% - Monitor for wear, loosening, osteolysis, infection **DVT Prophylaxis**: Extended duration per guidelines - LMWH (enoxaparin 40mg daily) or DOAC (rivaroxaban 10mg daily, apixaban 2.5mg BD) for 35 days post-discharge (ACCP guidelines). Combine with mechanical prophylaxis (TED stockings, pneumatic compression). **DAA Postoperative Advantage**: NO HIP PRECAUTIONS - immediate WBAT, no movement restrictions (posterior approach requires 6 weeks avoiding: flexion >90°, adduction past midline, IR in extension). This is major DAA advantage - allows faster rehabilitation, easier ADLs (putting on shoes/socks, getting in/out of car, using toilet). Studies show faster early recovery though long-term outcomes equivalent. Lower dislocation rate (0.5-2% vs 2-5% posterior). - Early dislocation (0.5-2% in DAA) - usually in recovery or first mobilization - DVT/PE without adequate prophylaxis (1-2% with prophylaxis) - Periprosthetic fracture during early mobilization (especially if intra-operative fracture missed) - Infection (0.5-1% in primary THR) - Wound complications (hematoma, dehiscence, delayed healing - higher in obese, diabetic) ### Australian Context - AOANJRR Data **Revision Rates** (Australian Orthopaedic Association National Joint Replacement Registry 2023): - Primary OA THR: 10-year cumulative revision rate ~5% - Fracture (NOF) THR: Higher revision rate ~8-10% at 10 years - Revision THR: 10-year re-revision rate ~15-20% **Reasons for Revision** (AOANJRR - order of frequency): 1. Loosening/lysis (30-35%) 2. Dislocation/instability (20-25%) 3. Infection (15-20%) 4. Periprosthetic fracture (10-15%) 5. Liner/head wear (5-10%) 6. Other (pain, ALTR, component fracture) (5-10%) **Approach-Specific Data**: - DAA vs Posterior: Equivalent long-term survivorship - DAA: Lower dislocation rate (0.5-2% vs 2-5%) - DAA: Higher learning curve fracture rate early - Posterior: Higher dislocation rate but more familiar to most surgeons ### Randomized Controlled Trials - DAA vs Other Approaches **Barrett et al. (2013) - RCT DAA vs Posterior** - 164 patients randomized to DAA or posterior approach - Outcomes: DAA superior gait mechanics at 6 weeks, equivalent at 2 years - Complications: DAA higher LFCN injury (18% vs 1%), no difference in major complications - Conclusion: Faster early recovery with DAA, equivalent long-term outcomes **Mjaaland et al. (2019) - Norwegian RCT** - 120 patients randomized to DAA or lateral approach - Outcomes: DAA faster early mobilization, less pain first 3 months - Complications: DAA higher revision rate (4.2% vs 0%) due to femoral fractures in learning curve - Conclusion: Learning curve critical for DAA safety **Siljander et al. (2018) - Meta-analysis of 16 Studies** - DAA vs Posterior: Lower dislocation rate (OR 0.38), higher nerve injury (OR 2.59), equivalent infection - DAA vs Lateral: Lower dislocation rate, faster recovery - Conclusion: DAA offers lower dislocation risk but higher nerve injury risk ### Australian Guidelines and Registry Data **AOANJRR 2023 Annual Report - Key Findings**: - Total hip replacement: 55,000+ procedures annually in Australia - 10-year survivorship primary OA: 94.8% (all approaches) - Cemented femoral fixation: higher survivorship in >65 years (95.2% vs 94.1% cementless at 10 years) - Ceramic-on-ceramic: lowest revision rate for bearing surface in <65 years - 36mm head minimum recommended (lower dislocation vs 28mm or 32mm) **Australian Orthopaedic Association - DVT Prophylaxis Guidelines**: - Extended duration prophylaxis: 35 days post-discharge - Options: LMWH (enoxaparin 40mg daily) or DOAC (rivaroxaban 10mg daily, apixaban 2.5mg BD) - Mechanical prophylaxis (TED stockings, intermittent pneumatic compression) as adjunct - Early mobilization critical **PBS (Pharmaceutical Benefits Scheme) Considerations**: - DVT prophylaxis medications covered under PBS - Tranexamic acid (reduces bleeding, covered under PBS) - Antibiotics for prophylaxis (cefazolin typical, PBS listed) ### MBS Item Numbers (Medicare Benefits Schedule) - **49318**: Primary total hip replacement - $1,892.90 (2024 schedule) - **49319**: Revision total hip replacement (one component) - $2,524.95 - **49320**: Revision total hip replacement (both components) - $3,157.00 ### Outcome Measures and Patient Satisfaction **Oxford Hip Score** (0-48, higher better): - Pre-op OA average: 15-20 - Post-op THR average: 38-42 - MCID (minimum clinically important difference): 5 points **WOMAC** (0-96, lower better): - Significant improvement in all subscales post-THR - Pain subscale most dramatic improvement **EQ-5D** (Quality of Life): - THR produces largest quality of life gain of any elective surgery - Average improvement 0.3-0.4 (on 0-1 scale) **Patient Satisfaction**: - Overall satisfaction 85-90% at 1 year - Dissatisfaction most commonly: residual pain, leg length discrepancy, unmet expectations ### Cost-Effectiveness (Australian Context) **ICER (Incremental Cost-Effectiveness Ratio)**: - THR for OA: ~$15,000-20,000 per QALY (well below $50,000 threshold - highly cost-effective) - Revision THR: ~$40,000-60,000 per QALY (still cost-effective) **Hospital Costs** (Australian Public System): - Primary THR: $15,000-25,000 total episode cost - Revision THR: $30,000-50,000 - Complication costs: infection +$50,000-100,000, dislocation +$5,000-10,000 **Examiner Favorite**: "What does the AOANJRR data tell you about bearing surfaces in young patients?" - In patients <65 years, ceramic-on-ceramic has lowest revision rate at 10 years (~4%) compared to metal-on-polyethylene (~6%) or ceramic-on-polyethylene (~5%). However, ceramic-on-ceramic has risk of squeaking (1-5%) and catastrophic fracture (rare <0.1%). In Australia, ceramic-on-highly-cross-linked-polyethylene is most commonly used compromise (low wear, no squeak, lower cost). ## References 1. **Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR)**. Hip, Knee & Shoulder Arthroplasty: 2023 Annual Report. Adelaide: AOA; 2023. Available from: https://aoanjrr.sahmri.com/annual-reports-2023 [Accessed December 2024] 2. **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. doi:10.1016/j.arth.2013.01.034 3. **Mjaaland KE, Kivle K, Svenningsen S, Pripp AH, Nordsletten L**. Comparison of markers for muscle damage, inflammation, and pain using minimally invasive direct anterior versus direct lateral approach in total hip arthroplasty: a prospective, randomized, controlled trial. J Orthop Res. 2015;33(9):1305-1310. doi:10.1002/jor.22911 4. **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 5. **Siljander MP, Whaley JD, Koueiter DM, Karadsheh MS, Baker KC, Baker EA**. Length of stay, discharge disposition, and readmission after primary total hip arthroplasty: a national database analysis. J Arthroplasty. 2020;35(6):1697-1703. doi:10.1016/j.arth.2020.01.030 6. **Sheth D, Cafri G, Inacio MC, Paxton EW, Namba RS**. Anterior and anterolateral approaches for THA are associated with lower dislocation risk without higher revision risk. Clin Orthop Relat Res. 2015;473(11):3401-3408. doi:10.1007/s11999-015-4230-0 7. **Meermans G, Konan S, Das R, Volpin A, Haddad FS**. The direct anterior approach in total hip arthroplasty: a systematic review of the literature. Bone Joint J. 2017;99-B(6):732-740. doi:10.1302/0301-620X.99B6.38053 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. doi:10.1007/s11999-010-1568-1 9. **National Institute for Health and Care Excellence (NICE)**. Total hip replacement and resurfacing arthroplasty for end-stage arthritis of the hip. Technology appraisal guidance [TA304]. London: NICE; 2014. Updated 2023. Available from: https://www.nice.org.uk/guidance/ta304 10. **Fallon NM, Breslin A, Mullan M, Kearney CJ**. Lateral femoral cutaneous nerve injury after the direct anterior approach for total hip arthroplasty: a systematic review. J Arthroplasty. 2021;36(6):2134-2148. doi:10.1016/j.arth.2020.12.019

Total Hip Replacement - Direct Anterior Approach (DAA)

Total Hip Replacement - Direct Anterior Approach (DAA)