import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Location**: 15-30mm posterior to piriformis tendon insertion at greater trochanter, courses between piriformis and superior gemellus, lies on posterior capsule **Protection**: Maintain hip flexion to relax nerve, palpate digitally posterior to short external rotators before division, stay on bone during rotator release, avoid posterior retractor placement beyond capsule, limit hip extension during exposure **Location**: 30-50mm proximal to greater trochanter tip, exits pelvis through greater sciatic notch above piriformis, runs between gluteus medius and minimus **Protection**: Limit proximal dissection above 5cm from GT, split gluteus maximus in line with fibers only, avoid superior retractor placement in gluteal muscles, stay in surgical safe zone defined by GT boundaries **Location**: 30-50mm medial to anterior acetabular rim, separated by anterior capsule and iliopsoas muscle, vulnerable with anterior retractor placement **Protection**: Place anterior Hohmann retractor directly on bone over anterior acetabular wall, avoid medial retractor angulation, use blunt retractors with rounded tips, visualize retractor position during acetabular exposure **Location**: Runs along medial wall of acetabulum 10-20mm from acetabular fossa, exits pelvis through obturator foramen, vulnerable during inferior retractor placement and medial reaming **Protection**: Place inferior Hohmann in obturator foramen gently without excessive depth, avoid medial wall perforation during reaming, stop reaming when subchondral bleeding appears, avoid anteroinferior acetabular screw placement **Location**: 10-15mm medial to quadratus femoris and deep to short external rotators, provides dominant blood supply to femoral head, branches anteriorly along femoral neck **Protection**: Release short external rotators directly from bone to minimize bleeding, use cautery on bone during rotator detachment, identify and cauterize ascending cervical branches during capsulotomy, maintain hemostasis before proceeding ## Internervous Plane **Gluteus maximus split**: True internervous plane due to dual innervation: - Superior portion: Inferior gluteal nerve (L5, S1, S2) - Inferior portion: Variable innervation from inferior gluteal nerve branches - Splitting muscle in fiber direction (superolateral to inferomedial) avoids nerve injury - Fibers run 45 degrees from vertical when patient in lateral position ## Key Anatomical Relationships ### Short External Rotators (Superior to Inferior) Most superior rotator, inserts on superior-posterior aspect of greater trochanter, sciatic nerve exits 2cm posterior to tendon insertion Thin muscle from ischial spine, joins obturator internus to form conjoint tendon Most robust tendon (15-20mm width), best structure for tagging and repair, tendon runs horizontally along lesser sciatic notch Thin muscle from ischial tuberosity, forms inferior part of conjoint tendon Broad rectangular muscle from ischial tuberosity to posterior femur, may be preserved in enhanced repair techniques ### Neurovascular Structures **Sciatic nerve**: Exits pelvis through greater sciatic notch below piriformis (90% of population), lies on posterior hip capsule, 15-30mm posterior to piriformis insertion depending on patient anatomy and hip position. Hip flexion relaxes nerve and increases safe distance. **Superior gluteal neurovascular bundle**: Exits above piriformis through greater sciatic notch, courses between gluteus medius and minimus. Safe surgical zone is within 5cm of greater trochanter tip. Injury causes Trendelenburg gait from gluteal denervation. **Medial femoral circumflex artery**: Provides 70-80% of femoral head blood supply via lateral epiphyseal vessels. Runs deep to short external rotators, 10-15mm medial to quadratus femoris. Ascending cervical branches on femoral neck are encountered during capsulotomy. **Inferior gluteal artery**: Accompanies sciatic nerve, supplies gluteus maximus. Branches encountered during deep dissection of gluteal muscle split. ## Acetabular Landmarks **Transverse acetabular ligament (TAL)**: Bridges inferior acetabular notch, represents anatomic equator and floor of acetabulum. Critical reference for reaming depth - do not breach TAL or ream inferior to it. Also used as anteversion reference (perpendicular to TAL equals approximately 20 degrees anteversion). **Teardrop**: Radiographic landmark representing medial acetabular wall. Visible on AP pelvis X-rays. Medializing cup to teardrop level restores anatomic hip center. **Fovea**: Central depression in acetabular floor, ligamentum teres insertion. Identifies true center of acetabulum. **Acetabular notch**: Inferior deficiency between anterior and posterior columns, bridged by TAL. ## Capsular Anatomy Posterior capsule is thickest portion of hip joint capsule, reinforced by zona orbicularis and ischiofemoral ligament. Primary posterior stabilizer when hip is flexed. Capsule attaches to acetabular rim peripherally and femoral neck distally (intertrochanteric line anteriorly, above intertrochanteric crest posteriorly). **Anatomical Correlation**: "The posterior approach is termed 'internervous' due to gluteus maximus dual innervation, but it is NOT intermuscular - we split the muscle itself. The subsequent plane between short external rotators and capsule is neither internervous nor intermuscular - it's simply a surgical plane. The key is understanding this approach sacrifices posterior soft tissue stabilizers temporarily, requiring meticulous repair for stability." ## Primary Indications ### Symptomatic Hip Arthritis with Conservative Treatment Failure **Osteoarthritis (most common)**: - Primary OA (idiopathic) - 75% of THR indications - Secondary OA (post-traumatic, dysplasia, SUFE, Perthes) - 15% of indications - Failed conservative management: physiotherapy 12+ weeks, analgesia (paracetamol, NSAIDs, opioids), activity modification, weight loss, walking aids - Functional limitation: Pain affecting activities of daily living, sleep disturbance, reduced mobility, quality of life impairment **Inflammatory Arthropathy**: - Rheumatoid arthritis (10% of THR indications in Australia) - Seronegative spondyloarthropathies (ankylosing spondylitis, psoriatic arthritis) - Systemic lupus erythematosus - Consider bilateral disease, protrusio acetabuli, bone quality issues **Avascular Necrosis (AVN)**: - Alcohol-related (30% of AVN cases) - Corticosteroid-induced (25%) - Idiopathic (20%) - Trauma-related (femoral neck fracture, hip dislocation) (15%) - Other: sickle cell disease, Gaucher disease, dysbaric (Caisson disease) - Ficat stage III-IV (femoral head collapse) requires arthroplasty **Post-traumatic Arthritis**: - Following acetabular fracture (10-20% develop OA at 10 years) - Following femoral neck fracture malunion/nonunion - Following hip dislocation with cartilage injury ### Fracture Indications **Femoral neck fractures** (Garden III-IV in elderly): - Age greater than 65-70 years with displaced femoral neck fracture - Lower functional demand compared to active patients who may undergo fixation or resurfacing **Pathological fractures**: - Metastatic bone disease (breast, lung, kidney, thyroid, prostate) - Primary bone tumors (rare) ### Other Indications **Developmental dysplasia of hip (DDH)**: Severe acetabular dysplasia with secondary OA, may require specialized components or augments **Failed previous surgery**: Failed hemiarthroplasty, failed osteotomy, failed internal fixation, failed hip resurfacing ## Posterior Approach Specific Advantages 1. **Excellent acetabular visualization**: Superior, posterior, and inferior acetabular walls well exposed, easier anatomic landmark identification (TAL, teardrop, fovea) 2. **Extensile**: Can extend proximally along femur for stem revision, distally for femoral access, posteriorly for acetabular column exposure 3. **Preserves hip abductors**: No division of gluteus medius or minimus, no risk to superior gluteal nerve, avoids Trendelenburg gait 4. **Surgeon familiarity**: Most Australian orthopedic surgeons trained in posterior approach, shorter learning curve 5. **Revision-friendly**: Easier to revise components through same approach, can extend exposure as needed ## Australian Registry Data (AOANJRR 2023) - **Posterior approach**: 60% of primary THR procedures - **Revision rate**: 6.8% at 10 years (all causes) - **Dislocation rate**: 1.2% with capsular repair (historical 4.5% without repair) - **Infection rate**: 0.7% deep infection at 2 years - **Implant survival**: 94.7% at 10 years (cumulative percent revision) **Clinical Reasoning**: "When discussing THR indications in the exam, I structure my answer using the pain-function-imaging triad. Pain: severity, duration, night pain, analgesia requirements. Function: ADL limitation, walking distance, stairs, quality of life scores. Imaging: joint space narrowing, sclerosis, osteophytes, subchondral cysts on plain X-rays. This demonstrates comprehensive clinical assessment before recommending surgery." ## Clinical Assessment ### History **Pain characteristics**: Location (groin for hip joint pain vs buttock/trochanteric for extra-articular), severity (VAS score), duration, night pain, analgesic use, relationship to activity **Functional limitation**: Walking distance, stairs, footwear, ADLs (dressing, bathing), work capacity, quality of life impact (Oxford Hip Score, HOOS, WOMAC) **Previous treatments**: Physiotherapy duration and response, medications tried, intra-articular corticosteroid injections (number, response, duration), walking aids **Medical comorbidities**: Cardiac disease, hypertension, diabetes mellitus, chronic kidney disease, liver disease, respiratory disease, previous VTE, medications (anticoagulation, immunosuppression) **Social factors**: Smoking status, alcohol use, home environment (stairs, supports), support systems, expectations ### Examination **Gait**: Antalgic gait, Trendelenburg gait (suggests concurrent abductor pathology), walking aids requirement **Hip ROM**: Flexion (normal 120°), internal rotation in 90° flexion (normal 40°, often most limited in OA), external rotation, abduction, adduction. Fixed flexion deformity measurement. **Leg length**: True leg length (ASIS to medial malleolus) vs apparent leg length (umbilicus to medial malleolus). Identify source of discrepancy (hip vs knee vs ankle vs spine). **Neurovascular**: Distal pulses (femoral, popliteal, dorsalis pedis, posterior tibial), sensation (L2-S1 dermatomes), motor power (hip flexion L2, knee extension L3-L4, ankle dorsiflexion L4-L5, EHL L5, plantar flexion S1) **Spine**: Examine for concurrent spine pathology (may contribute to pain), assess lumbar lordosis (may increase with hip flexion deformity) ## Imaging ### Plain Radiographs (Mandatory) **AP pelvis**: Both hips for comparison, assess: - Joint space narrowing - Osteophytes (femoral head, acetabular) - Subchondral sclerosis and cysts - Femoral head deformity (AVN, dysplasia) - Acetabular deformities (protrusio, dysplasia) - Pelvic obliquity - Previous surgery/hardware **Lateral hip**: Assess femoral head sphericity, anterior/posterior osteophytes, neck-shaft angle ### Advanced Imaging (Selected Cases) **CT scan**: Acetabular bone stock assessment (revision, dysplasia, post-traumatic), femoral deformity planning, 3D reconstruction for complex anatomy, previous hardware planning **MRI**: AVN staging (Ficat/ARCO classification), soft tissue assessment, exclude infection **Bone scan**: Exclude infection (combined with WBC scan), assess AVN, stress fracture ## Templating (Critical Preoperative Step) ### Digital or Acetate Templating **Magnification**: Calibrate with radiographic marker (usually 25mm ball bearing or calibration object). Typical magnification 115-120% on digital radiographs. **Objectives**: 1. Estimate component sizes (acetabular cup, femoral stem) 2. Determine femoral neck osteotomy level 3. Plan for leg length and offset restoration 4. Identify need for specialized implants (dysplasia, revision) ### Acetabular Templating - Identify anatomic landmarks: teardrop, Kohler line, sourcil (acetabular sourcil) - Template cup to restore anatomic hip center (level with teardrop medially) - Typical cup sizes: females 48-54mm, males 54-60mm - Cup should be positioned with 40-45° inclination on radiograph - Check medial wall bone stock adequacy ### Femoral Templating - Template stem size to achieve metaphyseal fit (cementless) or adequate cement mantle (cemented) - Determine osteotomy level (typically 1cm above lesser trochanter for most stems) - Assess for femoral deformity, previous surgery, canal characteristics - Plan neck length/head size for leg length and offset restoration - Estimate 60% of leg length restoration from femoral component, 40% from cup ### Leg Length Planning - Measure existing discrepancy - Plan to equalize leg lengths or slight overlengthening (5mm) preferable to shortening - Intraoperative references: lesser trochanter to ischium, greater trochanter to ASIS, calcar to teardrop ### Offset Planning - Offset affects abductor tension, stability, and range of motion - Restoring offset reduces dislocation risk and improves abductor function - Increased offset options: larger stem size, high offset stems, longer necks **Templating Mastery**: "Templating is MANDATORY for exam scenarios. I demonstrate systematic approach: calibrate magnification first, identify anatomic landmarks, template acetabulum to restore center of rotation at teardrop level, template femur for metaphyseal fit, plan osteotomy level, calculate leg length and offset restoration. I state typical sizes (female 50-54mm cup, male 54-58mm cup) and always have backup sizes available. Examiners expect you to discuss templating limitations and need for intraoperative flexibility." ## Consent Discussion ### Benefits - Pain relief (95% of patients achieve significant pain reduction) - Improved function and quality of life - Predictable long-term outcomes (95% survival at 10 years, 90% at 15 years) ### Common Risks (Quote Australian Registry Data) - **Dislocation**: 1-2% with posterior approach and capsular repair (emphasize hip precautions) - **Infection**: 0.7% deep infection risk, may require long-term antibiotics or revision surgery - **Leg length discrepancy**: 5-10% notice difference, most adapt, 5mm target acceptable - **DVT/PE**: 1-3% DVT with prophylaxis, 0.1-0.5% symptomatic PE - **Nerve injury**: Sciatic nerve 0.7-2%, usually recovers over 6-12 months - **Fracture**: Intraoperative 0.5-1%, postoperative 1-3% over 5 years - **Wear and loosening**: Revision risk 6-7% at 10 years, 10-12% at 15 years - **Need for revision**: 6.8% at 10 years (AOANJRR) ### Rare but Serious Risks - Vascular injury (femoral vessels, iliac vessels with acetabular screws) - Heterotopic ossification (10-20%, severe Brooker 3-4 in 1-3%) - Ceramic fracture (ceramic-on-ceramic bearings, 0.01-0.05%) - Anesthetic complications, MI, stroke - Death (0.2-0.5% at 90 days, higher in frail elderly) ## Medical Optimization **Cardiac**: Assess perioperative cardiac risk (Revised Cardiac Risk Index), optimize medications, consider cardiology review if high risk **Respiratory**: Smoking cessation 6-8 weeks preoperatively, optimize COPD/asthma, incentive spirometry **Diabetes**: HbA1c less than 7.5% (ideally less than 7.0%) reduces infection risk, optimize glucose control **Anticoagulation**: Bridging protocol for high-risk patients, warfarin cessation 5 days preop, DOACs cessation 48-72 hours preop depending on agent **Anemia**: Preoperative hemoglobin optimization, iron supplementation, consider erythropoietin if Hb less than 110 g/L **Nutrition**: Albumin greater than 35 g/L, nutritional supplementation if malnourished **Weight**: BMI less than 35 recommended (higher infection and complication rates with morbid obesity) **Infection screening**: Nasal MRSA swab (decolonization if positive), dental assessment (untreated caries), skin assessment (dermatitis, ulcers) **Urinary**: UTI screening and treatment if present, particularly in females and catheterized patients ## Patient Positioning **Lateral decubitus position**: Affected hip uppermost on radiolucent table **Pelvic positioning**: - Pelvis perpendicular to table (CRITICAL for accurate cup positioning) - Anterior pelvic support at ASIS - Posterior pelvic support at sacrum - Confirm perpendicular alignment fluoroscopically if available or using alignment devices - Any pelvic rotation affects acetabular component anteversion and inclination **Lower extremity positioning**: - Operative leg: free to move, hip and knee can flex - Dependent leg: flexed 90° hip/90° knee for stability and table contact **Upper extremity**: - Dependent arm on arm board, padded to prevent brachial plexus injury - Operative side arm: supported with arm positioner or draped across body **Pressure point padding**: All bony prominences (dependent greater trochanter, lateral malleolus, fibular head, medial malleolus, elbow, radial head) **Table height**: Surgeon's xiphisternum level optimizes ergonomics ## Surgical Steps with Safety Critical Points ### Step 1: Incision and Superficial Dissection **Surface anatomy**: Mark greater trochanter (GT) BEFORE draping - palpate and mark tip with sterile marker **Incision**: Curved incision 10-15cm (adjust for body habitus), centered on GT: - Proximal limb: from GT toward PSIS (5-7cm) - Distal limb: from GT along line of femoral shaft (7-10cm) - Curve allows extensile exposure if needed **Skin and subcutaneous**: Incise with knife, ensure hemostasis with diathermy **Fascia lata/ITB**: Identify and incise in line with skin incision using scissors or knife - Pre-mark greater trochanter before draping (landmark easily lost under drapes) - Curve incision slightly posterior for better rotator access - Longer incision in obese patients reduces soft tissue trauma from retraction - Identify and preserve lateral femoral cutaneous nerve if visible (anterior to incision) ### Step 2: Gluteus Maximus Split **Muscle fiber direction**: Superolateral to inferomedial (45° from vertical in lateral position) **Splitting technique**: - Blunt dissection with finger or sponge stick along fiber direction - May use scissors to initiate split then spread bluntly - Split centered on GT, extends 5-8cm from proximal fascia to distal muscle **Internervous plane**: Dual innervation of gluteus maximus (superior and inferior portions from inferior gluteal nerve) makes this true internervous plane **Trochanteric bursa**: Identify and preserve if possible for repair at closure - Stay within 5cm of GT to avoid superior gluteal neurovascular bundle (30-50mm proximal to GT) - Blunt dissection minimizes muscle trauma and bleeding - Inferior gluteal vessels encountered in deep dissection - cauterize if bleeding - Avoid excessive proximal extension (risk to superior gluteal nerve) **Technical Detail**: "The gluteus maximus split is a TRUE INTERNERVOUS PLANE, not just a muscle split. The muscle has dual innervation from the inferior gluteal nerve, with fibers oriented from superolateral origin (ilium/sacrum) to inferolateral insertion (femoral linea aspera and ITB). Splitting in fiber direction avoids denervation. This is a key exam distinction from anterolateral approach which splits gluteus medius (true muscle damage)." ### Step 3: Short External Rotator Identification and Tagging **Rotator anatomy (superior to inferior - PSOIQ mnemonic)**: 1. **Piriformis**: Most superior, inserts superior-posterior GT at piriformis fossa 2. **Superior gemellus**: Thin muscle from ischial spine 3. **Obturator internus**: Robust tendon (15-20mm), most important for tagging 4. **Inferior gemellus**: Thin muscle from ischial tuberosity 5. **Quadratus femoris**: Broad rectangular muscle to posterior femur **Tagging technique**: - Pass heavy non-absorbable suture (Ethibond #2 or Fiberwire #2) through piriformis tendon near insertion - Pass suture through conjoint tendon (obturator internus with gemelli) near insertion - Quadratus femoris may be preserved (enhanced repair techniques) - Tag with long sutures and clamp separately for identification at closure **Sciatic nerve localization**: - Palpate with finger posteriorly BEFORE cutting rotators - Nerve lies 2cm posterior to piriformis insertion - Hip flexion relaxes nerve and increases safe distance - Protect throughout case - ALWAYS palpate for sciatic nerve before cutting ANY structure - Nerve injury mechanism: traction (most common), sharp division (rare), retractor compression - Sciatic nerve runs between piriformis and superior gemellus - Medial circumflex femoral artery runs deep to rotators (10-15mm medial to quadratus) - Tag rotators with STRONG sutures - will need to repair under tension at closure ### Step 4: Rotator Release and Capsulotomy **Rotator release**: - Piriformis: detach from femoral insertion using diathermy on bone, protect nerve posteriorly - Conjoint tendon: detach from posterior GT with diathermy on bone - Quadratus femoris: may preserve (leave attached to femur) or release if needed for exposure **Capsulotomy**: - T-shaped (vertical incision along femoral neck, horizontal incision along acetabular rim) OR - H-shaped (box around femoral neck-acetabular junction) OR - Posterior L-shaped capsulotomy - TAG all four corners of capsule with strong sutures (Ethibond #2) - Capsular tagging is CRITICAL for repair **Capsular flap development**: - Develop plane between capsule and gluteus minimus anteriorly if needed - Minimal anterior dissection preserves anterior capsule for stability - Release rotators directly on bone to minimize bleeding from medial circumflex branches - Tag capsule at 4 corners BEFORE excising tissue - repair impossible without tags - Capsular repair is single most important factor for preventing dislocation (RR 0.27) - Avoid excessive anterior capsule release (compromises anterior stability) - Protect sciatic nerve - maintain visualization posteriorly **Evidence-Based Technique**: "Capsular repair reduces dislocation from 4.5% to 1.2% based on meta-analysis of over 15,000 patients (Kwon et al. JBJS 2006). Relative risk reduction of 73% makes this the most important modifiable intraoperative factor. I ALWAYS tag capsule with strong sutures for anatomic repair. Enhanced repair with transosseous tunnels may further reduce dislocation. This evidence is highly examinable." ### Step 5: Hip Dislocation **Dislocation maneuver**: 1. Flex hip 90° (brings femoral head posterior to acetabulum) 2. Adduct hip across contralateral leg (rotates head posteriorly) 3. Internally rotate hip (final rotation to dislocate) 4. Apply gentle traction if needed 5. May require gentle levering with bone hook on greater trochanter **Cautions**: - AVOID excessive force (femoral shaft fracture risk, especially osteoporosis, RA, Paget's) - If unable to dislocate: extend capsulotomy, ensure adequate rotator release - Greater trochanter avulsion possible with forceful manipulation **After dislocation**: - Remove femoral head with corkscrew or T-handle extractor - Send femoral head for culture (3 separate samples even in primary cases - baseline) - Mark femoral anteversion on anterior femoral neck with diathermy (reference for stem) - Femoral fracture risk: osteoporosis, rheumatoid, Paget's, metastases, long-standing stiffness - Sciatic nerve traction during dislocation - minimize traction force and duration - Greater trochanter fracture: gentle technique, avoid excessive lateral force - If dislocation difficult: reassess capsulotomy adequacy before forceful manipulation ### Step 6: Femoral Neck Osteotomy **Osteotomy level**: Determined by preoperative templating, typically 1cm above lesser trochanter **Technique**: - Expose femoral neck circumferentially, protect posterior tissues with retractor - Use oscillating saw perpendicular to femoral shaft axis - HORIZONTAL cut preserves calcar (medial femoral buttress - critical for load transfer) - Complete cut, remove femoral head with corkscrew **Osteotomy level effects**: - More proximal cut = longer leg, more stem anteversion, less metaphyseal fill - More distal cut = shorter leg, less anteversion, better metaphyseal fill - Calcar preservation critical for stem stability and load transfer to diaphysis - Cut too distal: short leg, inadequate femoral fill, subsidence risk, difficult stem insertion - Cut too proximal: long leg, nerve stretch injury risk, soft tissue imbalance, dislocation risk - Oblique cut: calcar deficiency, varus stem risk, asymmetric load transfer - Saw injury to posterior soft tissues: retract sciatic nerve, visualize posteriorly - Measure resected head diameter (32mm typical) - 60% leg length from femur, 40% from cup ### Step 7: Acetabular Exposure and Preparation **Retractor placement (3 retractors for exposure triangle)**: 1. **Anterior**: Hohmann retractor over anterior acetabular wall (on bone, visualize tip) 2. **Posterior**: Blunt retractor protecting sciatic nerve (on posterior wall or GT) 3. **Inferior**: Hohmann retractor in obturator foramen (gentle placement, avoid depth) **Acetabular preparation**: - Remove labrum circumferentially (rongeur or knife) - Remove capsule from acetabular rim - Remove all osteophytes (NOT part of true acetabulum) - Remove pulvinar (soft tissue and fat) from fovea - Identify critical landmarks: TAL (transverse acetabular ligament) inferiorly, teardrop medially, fovea centrally - Anterior retractor: Femoral neurovascular bundle 30-50mm medially - stay on bone - Posterior retractor: Sciatic nerve 15-30mm posterior - avoid posterior capsule penetration - Inferior retractor: Obturator NV bundle - gentle placement, avoid excessive depth - Medial wall: Thin (2-3mm), intrapelvic structures immediately medial, avoid perforation - Osteophyte removal: Use rongeur and curettes, expose true acetabular margins before reaming **Anatomic Landmarks**: "Three critical acetabular landmarks guide reaming: (1) TAL inferiorly defines anatomic floor - never ream inferior to this. (2) Teardrop medially on radiographs - goal is to medialize cup to this level. (3) Fovea centrally marks true center. I clear all soft tissue and osteophytes first to expose true acetabular bone margins. Osteophytes are reactive bone, not load-bearing acetabulum, and must be removed before measuring acetabular size." ### Step 8: Acetabular Reaming **Reaming sequence**: 1. Start with reamer 4-6mm SMALLER than templated size 2. Orient reamer at 40-45° inclination (operative), 15-20° anteversion 3. Ream MEDIALLY and SUPERIORLY to subchondral bone (look for bleeding bone, feel resistance change) 4. Ream in 2mm increments 5. Achieve full 180° contact with anterior, posterior, and superior walls 6. Final reamer: slight subchondral bleeding (ideal for osseointegration) 7. Stop when adequate press-fit achieved (final reamer 1-2mm smaller than cup) **Reaming goals**: - Medialize hip center to anatomic position (reduces joint reaction force by 20% per 5mm) - Restore anatomic version and inclination - Maximize host bone contact for biological fixation - Avoid excessive bone removal (preserve stock for future revision) - Medial wall perforation: Thin bone (2-3mm), intrapelvic structures (vessels, bladder, bowel) - Posterior wall insufficiency: Excessive posterior reaming causes instability - Peripheral perforation: Anterior (iliopsoas bursa), posterior (sciatic notch), superior (lateral) - Protrusio: Medial migration of acetabulum - ream back to lateral sourcil, may need augments - Dysplasia: Shallow acetabulum - may need structural grafts or specialized components - Stop reaming when: bleeding subchondral bone, good 3-point contact, press-fit achieved ### Step 9: Acetabular Component Insertion **Component size**: Final reamer + 1-2mm (press-fit), typically 48-60mm in adults **Cup orientation - Lewinnek Safe Zone (MANDATORY KNOWLEDGE)**: - **Inclination**: 40-45° (operative inclination in lateral position, appears more vertical than radiographic 40-45°) - **Anteversion**: 15-20° (perpendicular to TAL approximates 20°, or align with GT-knee axis) - Combined anteversion (cup + stem) should equal 25-45° total **Insertion technique**: - Place cup on introducer with orientation guides aligned - Position cup at desired inclination and anteversion - Impact gently with mallet, progressive seating - Cup should be STABLE (no toggle when stressed) - Assess peripheral rim contact (should be flush or slightly proud) **Supplemental fixation screws**: - Indications: Poor bone quality, large cup (greater than 60mm), revision, insufficient press-fit - Safe zone: POSTEROSUPERIOR quadrant only (10-2 o'clock position) - AVOID: Anteroinferior (external iliac vessels), directly inferior (obturator), directly superior (superior gluteal) - Screw length: Typically 25-35mm (check with depth gauge, avoid intrapelvic penetration) - Cup malposition most common cause of dislocation and impingement - Excessive inclination (greater than 55°): Edge loading, accelerated wear, loosening - Excessive anteversion (greater than 30°): Anterior impingement, posterior dislocation - Insufficient anteversion (less than 5°): Posterior impingement, anterior dislocation - Anteroinferior screws: External iliac vessels injury (potentially fatal), obturator NV injury - Posterior screws (greater than 2 o'clock): Sciatic nerve injury, superior gluteal vessels - Intrapelvic perforation: Iliac vessels, bowel, bladder, ureter **Safe Zone Mastery**: "LEWINNEK SAFE ZONE is mandatory exam knowledge: 40-45° inclination, 15-20° anteversion. These values minimize dislocation and impingement. However, 'safe zone' is population average - individual anatomy varies. Operative inclination in lateral position appears more vertical than radiographic inclination. I reference TAL for anteversion (perpendicular = 20°) and use alignment guides. Modern concept is 'combined anteversion' (cup + stem = 25-45° total) which may be more predictive than isolated cup anteversion." ### Step 10: Liner Insertion **Liner types**: - Polyethylene (highly cross-linked HXLPE standard in Australia, minimum 6-8mm thickness) - Ceramic (smooth surface, reduced wear, squeaking 1-2% with CoC) - Dual mobility (outer PE head + inner femoral head, for high dislocation risk) **Insertion technique**: - Clean cup taper and liner mating surface (dry thoroughly) - Align liner orientation marks with shell marks - Seat liner with impactor and mallet - Check complete seating: no gaps visible circumferentially, audible/palpable "click" - For dual mobility: ensure outer metal or ceramic head fully seated in liner - Incomplete seating: Liner dissociation (catastrophic failure) - Thin polyethylene (less than 6mm): Fracture risk, especially with large heads - Wrong liner orientation: Affects combined version, may increase impingement - Trapped debris: Prevents complete seating, clean thoroughly - Dual mobility: Ensure both articulations properly assembled (intraprosthetic dislocation reported) ### Step 11: Femoral Exposure and Canal Preparation **Femoral delivery**: - Place bent Hohmann retractor in piriformis fossa, lever femur anteriorly - Flex hip, externally rotate, adduct to deliver proximal femur into wound - Remove residual femoral neck and capsule from proximal femur **Canal preparation**: - Start with BOX CHISEL to open piriformis fossa (femoral entry point) - Direct box chisel handle LATERALLY (abduct) to create VALGUS alignment (prevents varus) - Sequential box chisels open metaphysis - Switch to broaches once canal open - Broach progressively to cortical contact circumferentially in metaphysis - Target ANTEVERSION 10-15° (use lesser trochanter as guide - should point posteriorly) **Broaching endpoints**: - Cortical contact felt circumferentially in metaphysis (tight fit) - Broach depth: calcar fully seated on broach shoulder - Broach stability: no toggle with stress - Appropriate anteversion: 10-15° for posterior approach (combined with cup = 25-45° total) - Varus stem alignment: Thigh pain, stress shielding, loosening, calcar fracture - MUST lateralize handle - Anterior perforation: Occurs with anterior femoral bow, curved or deformed femurs - Calcar fracture: Use hand to apply counter-pressure to calcar during broaching - Femoral shaft fracture: Osteoporosis, RA, Paget's, metastases, over-aggressive broaching - Greater trochanter fracture: Excessive lateral retraction force on Hohmann - Undersized stem: Subsidence, thigh pain, loosening - Oversized stem: Fracture during insertion ### Step 12: Trial Reduction and Stability Assessment (CRITICAL STEP) **Trial assembly**: - Insert trial stem (same size as final broach) - Insert trial neck (start with 0 or +3mm length based on templating) - Insert trial head (32mm or 36mm typical) - Reduce hip with traction and rotation **Stability testing (MANDATORY - EXAM CRITICAL)**: **Test 1 - Anterior Stability**: - Position: Hip in EXTENSION + 40° EXTERNAL ROTATION - This tests anterior capsule and anterior femoral head/cup relationship - Should NOT dislocate anteriorly - If unstable: reduce cup anteversion, increase head size, check impingement **Test 2 - Posterior Stability**: - Position: 90° FLEXION + MAXIMAL INTERNAL ROTATION + ADDUCTION - This tests posterior soft tissue repair and posterior stability - Should feel FIRM ENDPOINT before dislocation (surgeon should feel "clunk" resistance) - If unstable posteriorly: increase head size (+4mm jumbo heads improve stability by 30%), increase cup anteversion, ensure adequate posterior capsule for repair, consider dual mobility **Test 3 - Leg Length Assessment**: - Flex both knees equally over table edge - Compare patella heights (should be equal or operative 5mm longer acceptable) - Overlapping patellae test: bring feet together with knees flexed, patellae should overlap - Compare to contralateral hip if known normal - Soft tissue tension: hip should not be "floppy" (indicates overlengthening) **Test 4 - Offset Assessment**: - Adequate soft tissue tension (not too tight, not too loose) - Compare to contralateral side if possible - Shuck test: anterior-posterior translation should have firm endpoint - Inadequate stability testing: Most common cause of postoperative dislocation - Overlengthening (greater than 15mm): Sciatic nerve palsy (traction injury), soft tissue pain, impingement - Shortening (greater than 10mm): Instability, abductor weakness, patient dissatisfaction, litigation - Excessive offset: Impingement, trochanteric bursitis, abductor pain - Insufficient offset: Instability, reduced abductor moment arm, limp - Document stability and leg length: Medicolegal protection **Stability Testing Protocol**: "Stability testing is MANDATORY before final components and is highly examinable. I perform TWO critical tests: (1) Extension + 40° ER tests anterior stability - most important for posterior approach where posterior capsule is violated. (2) 90° flexion + IR + adduction tests posterior stability - should feel firm endpoint. If posteriorly unstable, I increase head size (+4mm significantly improves stability), optimize cup version, ensure adequate tissue for repair, or consider dual mobility. This systematic approach prevents 90% of dislocations." ### Step 13: Final Component Implantation **Cemented vs Cementless Decision**: **Cemented indications**: - Age greater than 75 years - Osteoporotic bone (DEXA T-score less than -2.5) - Dorr type C femur (champagne flute: wide metaphysis, narrow diaphysis) - Rheumatoid arthritis - Inflammatory arthropathy - Paget's disease - Need for immediate full weight-bearing **Cementless indications**: - Age less than 70 years - Good bone quality - Dorr type A or B femur (type A: stovepipe, type B: normal funnel) - Active patients - Adequate metaphyseal bone for press-fit **Cemented stem technique**: 1. Prepare femoral canal: pulsatile lavage, dry with suction and gauze, canal plug 1-2cm beyond stem tip 2. Mix cement (2-3 batches typical for femur) 3. Cement gun retrograde filling from depth to proximal 4. Pressurize cement (cement pressurizer or finger) 5. Insert stem with steady pressure, hold position until cement sets 6. Remove excess cement, ensure cement mantle 2-3mm circumferentially 7. Wait 8-10 minutes for polymerization (warm saline irrigation cools exotherm) **Cementless stem technique**: 1. Final canal preparation (ensure clean, dry) 2. Insert final stem aligned with anteversion (10-15° for posterior approach) 3. Impact progressively to full seating (calcar to shoulder contact) 4. Ensure NO MOVEMENT (rotational or axial stability) 5. Check leg length and offset with trial head first **Femoral head insertion**: - Select head material: ceramic-on-poly (standard), CoC (reduced wear, squeaking risk), metal-on-poly (avoid due to corrosion), dual mobility (high dislocation risk) - Head size: 32mm (standard stability), 36mm (improved stability, increased wear), 28mm (historical, higher dislocation) - Neck length: +0, +3, +5, +8mm options (based on trialing) - Clean morse taper thoroughly (dry) - Impaction: single firm blow (avoid eccentric loading which fractures ceramic) **Final reduction and stability confirmation**: - Reduce hip with traction and rotation - Perform in-situ stability testing (extension + ER, flexion + IR + adduction) - Confirm satisfactory stability before proceeding to closure - Cemented stem: Incomplete cement mantle (thin areas less than 2mm), cement extrusion into soft tissues, thermal injury - Cementless stem: Intraoperative fracture (0.5-1%), malposition, incomplete seating (proud stem) - Ceramic head fracture: Eccentric impaction, contamination, scratched taper - Wrong neck length: Affects final leg length and stability - Morse taper: Ensure clean and dry (corrosion and fretting if contaminated) ### Step 14: Posterior Soft Tissue Repair (MOST CRITICAL FOR PREVENTING DISLOCATION) **Capsular repair (ESSENTIAL - reduces dislocation by 70%)**: - Retrieve tagged capsular sutures (4 corners) - Repair capsule anatomically with interrupted or running sutures - Suture material: Ethibond #2 or equivalent non-absorbable braided - Repair with hip in neutral position (not flexed/extended) - Ensure tensioned repair (not loose) **Short external rotator repair**: - Retrieve tagged piriformis and conjoint tendon sutures - Reattach rotators to original femoral insertion (posterior GT area) - If bone avulsed: transosseous tunnels through GT for stronger repair - Enhanced repair: figure-of-8 sutures, preserving quadratus femoris, double-row repairs **Trochanteric bursa repair**: Close if preserved (reduces fluid collection) **Gluteus maximus fascia**: Running absorbable suture (1-Vicryl) **Fascia lata/ITB**: Running absorbable suture (1-Vicryl) **Subcutaneous layer**: Running or interrupted 2-0 Vicryl **Skin**: Subcuticular 3-0 Monocryl or skin staples **Drain**: Controversial (may increase transfusion but reduces hematoma) - use if extensive dead space or bleeding concerns - Inadequate capsular repair: Increases dislocation from 1.2% to 4.5% (4-fold increase) - Sutures pulling through osteoporotic bone: Use larger bites, transosseous tunnels - Excessive tension on repair: May fail or restrict motion - Inadequate hemostasis: Hematoma, wound complications, infection risk - Layered closure without tension: Reduces wound dehiscence and infection **Repair Evidence**: "Posterior soft tissue repair is the SINGLE MOST IMPORTANT modifiable intraoperative factor for preventing dislocation. Meta-analysis shows capsular repair reduces dislocation from 4.5% to 1.2% (RR 0.27, 95% CI 0.18-0.41). I perform meticulous anatomic repair: tag capsule before cutting, repair with strong non-absorbable sutures, reattach rotators to bone or through transosseous tunnels. Enhanced repair techniques further reduce dislocation. This evidence-based approach is highly examinable and demonstrates surgical excellence." ## Early Complications (0-6 weeks) ### Dislocation **Incidence**: - Without capsular repair: 4-5% - With capsular repair: 1-2% - With enhanced repair: less than 1% - 75% occur within 3 months, 90% within 1 year **Direction**: - Posterior: 85% (posterior approach) - Anterior: 15% **Risk factors**: - Patient: Age greater than 75, cognitive impairment, neuromuscular disease, prior dislocation, multiple medical comorbidities - Technical: Inadequate posterior repair, component malposition (excessive cup anteversion/inclination), femoral head size (28mm higher risk vs 36mm), inadequate offset, spinopelvic mobility issues - Postoperative: Non-compliance with precautions, fall trauma **Prevention**: - Meticulous capsular and rotator repair (most important) - Optimal component positioning (Lewinnek safe zone, combined anteversion) - Larger femoral head size (36mm vs 32mm vs 28mm) - Dual mobility implants (high-risk patients) - Patient education and precautions **Management**: - First dislocation: Closed reduction under sedation, hip precautions 12 weeks, investigate cause (imaging to assess components) - Recurrent dislocation (2 or more events): Revision surgery indicated - options include liner exchange with head size increase, revision for malpositioned components, revision with dual mobility, trochanteric advancement, constrained liner (last resort) ### Infection **Incidence**: - Superficial: 1-2% - Deep (PJI): 0.5-1% at 2 years (AOANJRR) **Risk factors**: Diabetes, obesity (BMI greater than 35), rheumatoid arthritis, immunosuppression, previous surgery, prolonged operative time (greater than 2 hours), wound complications **Prevention**: - Preoperative: MRSA screening and decolonization, dental assessment, skin optimization, glucose control (HbA1c less than 7.5%) - Intraoperative: Prophylactic antibiotics (cephazolin 2g or vancomycin 15mg/kg), laminar flow theatre, minimize traffic, meticulous sterile technique, minimize operative time - Postoperative: Wound monitoring, early mobilization, glycemic control **Diagnosis**: Clinical (wound drainage, fever, pain), laboratory (CRP, ESR, synovial WCC/PMN%, alpha-defensin), synovial culture **Management**: - Acute (less than 3 weeks or less than 3 weeks from symptom onset): DAIR (debridement, antibiotics, implant retention) - liner exchange, thorough debridement, 6-12 weeks IV antibiotics - Chronic (greater than 3 weeks): Two-stage revision - explant components, antibiotic spacer, 6-12 weeks IV antibiotics, reimplantation ### Nerve Injury **Sciatic nerve**: - Incidence: 0.7-2% (most common nerve injury in posterior approach) - Mechanism: Traction injury (most common, 80%), sharp division (rare), hematoma compression, cement extrusion - Presentation: Foot drop (common peroneal division), weak plantar flexion (tibial division), sensory loss (lateral leg/foot) - Prognosis: 60-70% recover by 6-12 months, complete division poor prognosis - Prevention: Hip flexion during exposure, gentle tissue handling, avoid overlengthening (limit to 5-10mm), avoid posterior retractor beyond capsule - Management: Document deficits immediately post-op, nerve studies at 3 weeks (baseline), expectant management with AFO, monitor recovery, explore if sharp division suspected or no recovery by 3 months **Femoral nerve**: Rare with posterior approach (0.1%), more common with anterior approach **Superior gluteal nerve**: Rare with posterior approach (risk with proximal extension greater than 5cm above GT) ### Periprosthetic Fracture (Intraoperative) **Incidence**: 0.5-1% intraoperative, 1-3% postoperative at 5 years **Risk factors**: Osteoporosis, rheumatoid arthritis, Paget's disease, metastases, prior surgery, cementless stems (press-fit), undersizing canal then forceful impaction **Classification**: Vancouver for femoral fractures (AG, AL, B1, B2, B3, C) **Intraoperative fractures**: - Calcar fracture: Most common, treat with cerclage wire/cable if unstable, consider cemented stem - Femoral shaft fracture: Requires internal fixation (plate, cerclage wires) or longer stem bypassing fracture - Greater trochanter fracture: Non-displaced observe, displaced repair with wires/cables - Acetabular fracture: May require column plating before cup insertion, or cage/augments **Prevention**: Avoid varus stem, gentle broaching/impaction, hand pressure on calcar during broaching, appropriate stem sizing ### DVT/PE **Incidence**: - Symptomatic DVT: 1-3% with prophylaxis - Symptomatic PE: 0.1-0.5% - Fatal PE: 0.01-0.05% **Risk factors**: Age, previous VTE, malignancy, obesity, prolonged surgery, immobility **Prevention (Australian guidelines)**: - Mechanical: Early mobilization, TED stockings, intermittent pneumatic compression intraoperatively - Pharmacological: LMWH (enoxaparin 40mg daily) for 4-6 weeks, OR rivaroxaban 10mg daily for 5 weeks - Balance: Bleeding risk vs VTE risk **Diagnosis**: Wells score, D-dimer (if low probability), Doppler ultrasound (DVT), CTPA (PE) **Management**: Therapeutic anticoagulation (LMWH or DOAC) for 3-6 months ### Leg Length Discrepancy **Incidence**: 5-10% patients perceive greater than 5mm difference, most adapt **Acceptable**: Less than 5mm generally well-tolerated, up to 10mm acceptable in some patients **Problematic**: Greater than 10mm causes gait disturbance, Greater than 15mm causes nerve palsy risk and is common litigation source **Prevention**: Preoperative templating, intraoperative measurement (trial components), use anatomic references (lesser trochanter to ischium, calcar to teardrop) **Management**: Shoe raise if symptomatic, revision surgery if extreme (greater than 20mm) and not tolerated ## Intermediate Complications (6 weeks to 2 years) ### Heterotopic Ossification (HO) **Incidence**: 10-20% develop HO, Brooker grade 3-4 (severe, limiting ROM) in 1-3% **Risk factors**: Male gender, ankylosing spondylitis, DISH, previous HO, post-traumatic arthritis, hypertrophic OA, extended surgical approach **Classification**: Brooker grade 0-4 **Prevention**: - Indomethacin 25mg TDS for 6 weeks postoperatively (most effective), OR - Single-dose radiation therapy (700cGy) within 24-72 hours post-op - Gentle soft tissue handling intraoperatively **Management**: Observation if asymptomatic, excision if severe and mature (wait 12-18 months for maturity) ### Aseptic Loosening (Early) **Definition**: Loosening without infection within first 2 years **Causes**: Poor initial fixation, cement technique issues, component malposition, infection (must exclude) **Diagnosis**: Progressive radiolucent lines (greater than 2mm), component migration, pain **Management**: Revision arthroplasty if symptomatic ## Late Complications (Greater than 2 years) ### Aseptic Loosening (Late) **Incidence (AOANJRR 10-year data)**: - Cup loosening: 1-3% - Stem loosening: 2-5% - Most common cause of late revision **Mechanism**: Osteolysis from particle disease (polyethylene wear debris), stress shielding (cemented stems), component malposition **Diagnosis**: Serial radiographs showing progressive radiolucent lines, component migration, cortical thinning, endosteal scalloping **Management**: Revision arthroplasty with bone grafting if osteolysis present ### Polyethylene Wear and Osteolysis **Wear rate**: - Conventional poly: 0.1-0.2mm/year - Highly cross-linked poly (HXLPE): 0.05-0.1mm/year (reduced by 50%) **Osteolysis**: Inflammatory response to PE wear particles causing bone loss **Prevention**: HXLPE standard in modern implants, optimal component positioning to reduce edge loading **Monitoring**: Annual radiographs after first year to assess wear and osteolysis **Management**: Revision before massive bone loss if significant wear or osteolysis ### Squeaking (Ceramic-on-Ceramic) **Incidence**: 1-2% with CoC bearings **Causes**: Edge loading (cup malposition), stripe wear, impingement, third-body wear **Management**: Observation if tolerated, revision if intolerable (liner and head exchange) ## Outcomes ### Functional Outcomes **Patient satisfaction**: 85-90% excellent/good at 2 years **Pain relief**: 95% achieve significant pain relief **Functional improvement**: Mean Oxford Hip Score improvement 20-25 points, Mean WOMAC improvement 40-50 points **Return to activities**: Walking unlimited 95%, stairs normal 90%, return to low-impact sports 70-80% (golf, swimming, cycling) ### Implant Survival (AOANJRR 2023) **10-year cumulative survival**: 94.7% (all causes of revision) **15-year cumulative survival**: 89-91% **20-year cumulative survival**: 85-88% **Causes of revision** (in order of frequency): 1. Aseptic loosening (30-40%) 2. Dislocation (15-20%) 3. Infection (10-15%) 4. Periprosthetic fracture (10-15%) 5. Bearing surface wear/osteolysis (5-10%) 6. Other (liner fracture, squeaking, pain) (10-15%) **Outcomes Discussion**: "When discussing THR outcomes in exams, I quote Australian registry data: 94.7% survival at 10 years, revision rate 6.8% at 10 years (AOANJRR 2023). Main revision causes are loosening (30-40%), dislocation (15-20%), and infection (10-15%). Patient satisfaction is 85-90% excellent/good. I emphasize modern highly cross-linked polyethylene reduces wear from 0.2mm/year to 0.05mm/year, significantly improving longevity. These registry-based answers demonstrate evidence-based practice." ## References 1. Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Hip, Knee & Shoulder Arthroplasty: 2023 Annual Report. Adelaide: AOA, 2023. Available at: https://aoanjrr.sahmri.com/annual-reports-2023 2. Kwon MS, Kuskowski M, Mulhall KJ, Macaulay W, Brown TE, Saleh KJ. Does surgical approach affect total hip arthroplasty dislocation rates? Clin Orthop Relat Res. 2006;447:34-38. doi:10.1097/01.blo.0000218746.84494.df 3. Lewinnek GE, Lewis JL, Tarr R, Compere CL, Zimmerman JR. Dislocations after total hip-replacement arthroplasties. J Bone Joint Surg Am. 1978;60(2):217-220. 4. Ranawat CS, Maynard MJ. Modern techniques of cemented total hip arthroplasty. Tech Orthop. 1991;6:17-25. 5. Dorr LD, Malik A, Dastane M, Wan Z. Combined anteversion technique for total hip arthroplasty. Clin Orthop Relat Res. 2009;467(1):119-127. doi:10.1007/s11999-008-0598-4 6. Masonis JL, Bourne RB. Surgical approach, abductor function, and total hip arthroplasty dislocation. Clin Orthop Relat Res. 2002;(405):46-53. doi:10.1097/00003086-200212000-00006 7. Jolles BM, Zangger P, Leyvraz PF. Factors predisposing to dislocation after primary total hip arthroplasty: a multivariate analysis. J Arthroplasty. 2002;17(3):282-288. doi:10.1054/arth.2002.30286 8. Berry DJ, von Knoch M, Schleck CD, Harmsen WS. Effect of femoral head diameter and operative approach on risk of dislocation after primary total hip arthroplasty. J Bone Joint Surg Am. 2005;87(11):2456-2463. doi:10.2106/JBJS.D.02860 9. Patel PD, Potts A, Froimson MI. The dislocating hip arthroplasty: prevention and treatment. J Arthroplasty. 2007;22(4 Suppl 1):86-90. doi:10.1016/j.arth.2007.03.031 10. Australian and New Zealand Hip Fracture Registry (ANZHFR). Annual Report 2022. Adelaide: Australian and New Zealand Hip Fracture Registry Steering Group, 2022. Available at: https://anzhfr.org/annual-reports/

Total Hip Replacement - Posterior Approach (Moore/Southern)

Total Hip Replacement - Posterior Approach (Moore/Southern)