Comprehensive surgical technique guide for primary uncemented total hip arthroplasty via the posterior approach with AOANJRR context for FRCS exam preparation
Reviewed by OrthoVellum Editorial Team
Orthopaedic clinicians and medical editors • Published by OrthoVellum Medical Education Team
Posterior approach (Moore/Southern) most common in Australia - curved incision centered over greater trochanter, extended posteriorly. Split gluteus maximus. Expose short external rotators. Alternatively: Anterolateral (Watson-Jones/Hardinge), Direct Anterior (muscle-sparing), or Lateral (Hardinge) approaches. | advanced
Sciatic nerve. Location: Posterior to hip joint, courses 15-30mm posterior to posterior capsule. Protection: Avoid excessive posterior retraction, gentle tissue handling, identify nerve in revision cases, avoid prolonged abnormal positioning during dislocation, limit leg lengthening to less than 15mm
Superior gluteal nerve and vessels. Location: Exit pelvis through greater sciatic notch above piriformis, run between gluteus medius and minimus. Protection: Limit dissection to less than 5cm proximal to greater trochanter tip, avoid superior retractor migration, identify before extending incision proximally
Femoral neurovascular bundle. Location: Anterior to hip joint, medial to anterior hip capsule and femoral neck. Protection: Careful placement of anterior acetabular retractor (stay on bone, not into pelvis), avoid anterior perforation during acetabular reaming, gentle medial capsular release
Obturator neurovascular bundle. Location: Passes through obturator foramen inferior-medial to acetabulum. Protection: Avoid inferior acetabular retractor migration medially, careful inferior reaming, avoid screws in inferior quadrant
External iliac vessels. Location: Anterior to hip joint along pelvic brim, at risk with anterior acetabular screws. Protection: Safe screw zones are anterosuperior (10-2 o'clock) and posterosuperior - avoid anterior horizontal screws, limit screw penetration to 20mm beyond cortex, use fluoroscopy for anterior screws
Patient Position: Lateral decubitus position with affected side up. Pelvis stabilized with anterior support against pubis and posterior support against sacrum - must be perpendicular to floor (verify with level). All bony prominences well-padded including axillary roll caudal to axilla (not in axilla to avoid brachial plexus injury), pillows between knees, fibular head padding. Arms positioned on arm boards or chest support. Contralateral leg slightly flexed at hip and knee.
Surgical Approach: Posterior approach (Moore/Southern) most common in Australia (approximately 60% per AOANJRR). Alternatively: Direct Anterior (20%), Hardinge lateral (15%), Watson-Jones anterolateral (5%). Posterior approach advantages: familiar anatomy, extensile, spares abductors. Disadvantages: higher dislocation risk without repair (10-15% vs 2-5% anterior), requires robust soft tissue repair.
Incision: Curved incision centered over greater trochanter, extending 8-10cm proximally-posteriorly along gluteus maximus fibers, then 3-5cm distally along femoral shaft. Mark incision with skin marker before draping.
Complete acetabular exposure requires three retractors in standard positions:
Anterior retractor (12 o'clock): Hohmann over anterior wall - stay on bone to avoid femoral vessels
Inferior retractor (3 o'clock left hip, 9 o'clock right hip): Broad retractor over inferior wall - protect obturator neurovascular bundle
Posterior retractor (6 o'clock): Hohmann around posterior wall - avoid excessive retraction (sciatic nerve 15-30mm posterior)
Remove all soft tissue: Labrum circumferentially, osteophytes (especially posterior-inferior), ligamentum teres remnant, transverse acetabular ligament (TAL) can be preserved as version guide
Start small: Initial reamer 38-40mm typically, engage all quadrants
Incremental progression: Ream 2mm at a time until bleeding subchondral bone visible over greater than 70% of hemisphere
Orientation: 40-45° inclination (from horizontal), 15-20° anteversion (middle of safe zone is safest)
Final size: Under-ream by 1-2mm for press-fit (e.g., if final reamer is 56mm, use 54-55mm cup)
Transverse acetabular ligament (TAL): Connects anterior and posterior horns of acetabulum, typically oriented 15-25° anteverted - useful intraoperative reference
Patient position: If pelvis perpendicular to floor, cup aimed 15-20° anterior to coronal plane
Lateral decubitus reference: Some surgeons use 45° from vertical as target (combines inclination and version)
Exam Pearl
Technical Tip: EXAM KEY - Acetabular reaming goals are threefold: 1) Create hemisphere of bleeding subchondral bone for biological fixation (bony ingrowth), 2) Achieve accurate orientation within Lewinnek safe zone (30-50° inclination, 10-30° anteversion), 3) Maximize bone preservation (stay lateral to medial wall, avoid over-reaming). Common errors: medialization through floor (alters biomechanics, risks pelvic structures), excessive inclination over 50° (edge loading, accelerated wear), inadequate exposure (malposition).
Modern uncemented cups rely on initial press-fit stability (micromotion less than 50 microns allows ingrowth). Under-reaming by 1-2mm creates interference fit. Porous coating or hydroxyapatite promotes ingrowth. Supplemental screws provide initial stability but do not improve long-term fixation per AOANJRR data - use 2-3 screws in safe zones if concerned about initial stability.
| Complication | Recognition | Prevention | Management |
|---|---|---|---|
| Dislocation (2-10% primary THA) | Acute pain, deformity, leg shortening and rotation (posterior dislocation: flexed adducted internally rotated, anterior dislocation: extended abducted externally rotated), inability to bear weight, confirm with AP and lateral X-rays | Accurate cup positioning (Lewinnek safe zone 30-50° inclination, 10-30° anteversion), restore offset and leg length, larger head size (32-36mm better than 28mm), robust posterior soft tissue repair if posterior approach, patient education on hip precautions if used, avoid combined version abnormalities | First dislocation: closed reduction under sedation in emergency department, post-reduction X-ray and CT to assess component position, strict hip precautions 6-12 weeks, abduction brace. Recurrent dislocation (2 or more): CT scan to measure component version and identify impingement, if malpositioned - revision to correct position, if well-positioned - larger head, constrained liner, dual-mobility cup, or revision to different approach. AOANJRR: dislocation is leading cause of early revision |
| Deep infection/PJI (0.5-1.5% primary THA) | Early (less than 3 weeks): wound drainage, erythema, fever, pain. Late chronic (greater than 3 weeks): pain with weight-bearing, elevated CRP/ESR, loosening on X-ray. Diagnosis: joint aspiration with culture, WBC count, CRP/ESR. MSIS criteria for PJI diagnosis | Antibiotic prophylaxis (cefazolin 2g pre-incision, redose every 4h), strict sterile technique, laminar flow theater, minimize operating time under 90 minutes, meticulous hemostasis, copious irrigation (3L minimum), optimize patient factors (HbA1c under 7% in diabetics, smoking cessation, treat remote infections), consider dilute betadine irrigation (controversial) | Early infection (less than 3 weeks): DAIR (debridement antibiotics implant retention) if components stable and organism favorable - remove liner/head, thorough debridement, exchange modular components, IV antibiotics 6-12 weeks, success rate 50-70%. Late chronic infection: usually requires two-stage revision - remove all implants, place antibiotic spacer, IV antibiotics 6 weeks, reimplant after infection cleared (success 85-90%). Single-stage revision for selected low-virulence organisms in Europe. AOANJRR: infection accounts for 15-20% of all THA revisions |
| Periprosthetic fracture (1-3% intraoperative, 1-2% postoperative over 10 years) | Intraoperative: sudden loss of resistance during impaction, audible crack, visible fracture line, stem instability. Postoperative: acute pain after fall, inability to bear weight, X-ray shows fracture (AP and lateral plus obliques). Vancouver classification for femoral fractures guides treatment | Careful surgical technique, adequate femoral exposure, appropriate templating and sizing, recognize tight fits and adjust (do not force impaction), consider cemented stem in very osteoporotic bone (T-score less than -2.5), bisphosphonate therapy for bone health, fall prevention strategies | Intraoperative acetabular: if non-displaced and stable cup - supplemental screws in safe zones, protected weight-bearing 6 weeks. If displaced - plate fixation plus-minus revision to cup with augment. Intraoperative femoral: if non-displaced and stem stable - cerclage cables/wires, protected WBAT. If displaced or unstable - revision to long stem bypassing fracture plus-minus plate. Postoperative femoral per Vancouver: AG (greater trochanter) - ORIF if displaced. B1 (stable stem, good bone) - ORIF with plate. B2 (loose stem) - revision long stem plus-minus plate. B3 (loose stem, poor bone) - revision long stem plus allograft plus-minus plate. C (distal to stem) - ORIF with plate. AOANJRR: uncemented stems have higher periprosthetic fracture risk than cemented, especially in elderly osteoporotic patients |
| Leg length discrepancy (50% have greater than 5mm, 5-10% have greater than 15mm - leading cause of litigation) | Postoperative: patient reports leg feels longer or shorter, asymmetric gait, back pain. Clinical: measure ASIS to medial malleolus bilaterally, compare knee heights supine, assess pelvic obliquity standing. Radiographic: measure vertical distance from ischial tuberosity to lesser trochanter on AP pelvis X-ray, compare to contralateral side | Preoperative templating (digital templating preferred over analog), intraoperative measurement (compare knee heights with legs parallel and pelvis level, measure ASIS to medial malleolus), use of leg length measuring devices or fluoroscopy, careful trialing before final implants. Aim for equal length or up to 5mm lengthening (better for stability than shortening). Discuss with patient preoperatively that perfect equality may not be possible if needed for stability/offset | If detected intraoperatively during trialing: adjust head size/length, adjust stem size, or accept small difference if necessary for stability. Postoperative less than 10mm: most patients adapt, reassure. 10-15mm symptomatic: shoe lift (external in shoe or heel raise). Greater than 15mm symptomatic: consider shoe lift first, revision only for severe symptoms (greater than 20mm) and patient demand - revision is challenging surgery with risk of complications. Important: document discussion preop about possibility of LLD and need to balance with stability |
| Sciatic nerve palsy (0.1-1%, higher in posterior approach, revision, DDH) | Foot drop (inability to dorsiflex ankle/toes), weakness of ankle plantarflexion, numbness in lateral leg and dorsum of foot. May be complete (all motor and sensory) or incomplete (partial function). Assess immediately postop and document (medicolegal). EMG/nerve conduction studies at 3 weeks if no recovery | Avoid excessive retraction posteriorly, protect nerve during exposure (identify in revision cases), avoid prolonged abnormal positioning during dislocation, limit leg lengthening to less than 15mm (lengthening greater than 15mm increases nerve palsy risk 10-fold), gentle tissue handling, ensure pelvis stable (pelvic motion during leg lengthening increases traction injury risk) | Most are neurapraxias (stretch injury) that recover over 3-12 months. Immediate postop if nerve palsy detected: 1) Check leg length (if over-lengthened greater than 15mm, strongly consider revision to shorter construct within 24-48h), 2) Document deficit completely, 3) Ankle-foot orthosis (AFO) for foot drop, 4) Physiotherapy for ROM and strengthening. Monitor recovery with serial exams. EMG/NCS at 3 weeks (baseline) and 3 months (assess recovery). Neurology referral if no recovery by 3-6 months. If complete transection suspected (rare): exploration and nerve repair/grafting (rarely indicated, poor outcomes). Prognosis: 60-80% recover fully, 20-40% have permanent deficit (usually partial) |
| Venous thromboembolism - DVT and PE (without prophylaxis: DVT 40-60%, with prophylaxis: DVT 2-5%) | DVT: leg pain, swelling, warmth, Homan sign (unreliable). Wells score for clinical probability. Duplex ultrasound for diagnosis (sensitivity 95% for proximal DVT). D-dimer if low probability (high sensitivity, low specificity). PE: dyspnea, chest pain, tachycardia, hypoxia. CTPA for diagnosis | All THA patients require pharmacological prophylaxis per Australian guidelines: LMWH (enoxaparin 40mg SC daily x 35 days starting 6-12h postop) OR DOAC (rivaroxaban 10mg daily x 35 days, apixaban 2.5mg BD x 35 days). Mechanical prophylaxis (TED stockings, pneumatic compression devices intraoperatively and postop). Early mobilization day 1. Adequate hydration. Extended prophylaxis 35 days proven to reduce late VTE events (ACCP guidelines) | DVT: anticoagulation for 3-6 months (LMWH bridge to warfarin INR 2-3, OR direct oral anticoagulant). If contraindication to anticoagulation and proximal DVT: consider IVC filter. PE: anticoagulation 3-6 months, supportive care (oxygen, IV fluids). Massive PE with hemodynamic instability: thrombolysis (alteplase) or surgical embolectomy. EXAM KEY: VTE prophylaxis is MANDATORY for all THA patients. Australian guidelines specifically recommend 35 days pharmacological prophylaxis based on level 1 evidence |
| Aseptic loosening (cemented cups 10-20% at 15 years, uncemented cups less than 5% at 15 years) | Progressive groin pain with weight-bearing (start pain indicates loosening), progressive radiolucent lines around component (greater than 2mm continuous), component migration (subsidence, change in position on serial X-rays), osteolysis (focal bone loss from particle disease). Infection must be ruled out (CRP, ESR, aspiration) | Accurate surgical technique (press-fit for uncemented - 1-2mm under-ream, good cement technique for cemented - third generation), highly cross-linked polyethylene to reduce wear and osteolysis (AOANJRR shows 30% reduction in revision versus standard PE), appropriate patient selection (uncemented requires good bone stock), avoid excessive activity in young patients (counsel on activity modification) | Asymptomatic radiographic loosening (radiolucent lines but no pain or progression): observe with serial X-rays 6-12 monthly, optimize bone health, activity modification. Symptomatic loosening (progressive pain, component migration): revision arthroplasty indicated. Preoperative workup essential: rule out infection (CRP, ESR, joint aspiration for culture, WBC, alpha-defensin), assess bone loss (CT scan), plan reconstruction (may need augments, bone graft, trabecular metal). EXAM KEY: Modern uncemented cups and stems have excellent survivorship greater than 95% at 15 years per AOANJRR. HXLPE has dramatically reduced osteolysis and late aseptic loosening |
| Heterotopic ossification/HO (radiographic 15-50%, clinically significant limiting ROM 5-10%) | Progressive stiffness and reduced ROM weeks to months postoperatively, pain with ROM especially terminal range, AP pelvis X-ray shows ectopic bone formation around hip (Brooker classification I-IV, grade III-IV functionally significant). May present as failure to progress in physiotherapy | Risk factors: male sex, prior HO, ankylosing spondylitis, DISH, post-traumatic arthritis, hypertrophic OA. Prophylaxis for high-risk patients: single-dose radiation (7-8 Gy within 24h pre or postop, avoid if young due to malignancy risk) OR indomethacin 75mg daily x 6 weeks (contraindicated if renal impairment, GI ulcer, may impair bone ingrowth - controversial). Routine prophylaxis NOT recommended for standard primary THA per AOANJRR | Brooker I-II (minor HO, full ROM): no treatment required, observe. Brooker III-IV (severe HO limiting ROM and function): initially conservative with aggressive physiotherapy, NSAIDs for pain. If persistent severe limitation after 12-18 months: surgical excision once HO mature (bone scan cold, alkaline phosphatase normal, 12+ months from surgery) PLUS prophylaxis (radiation within 24h or indomethacin x 6 weeks) to prevent recurrence. Success rate 70-80% for improved ROM. EXAM KEY: Brooker classification - I (bone islands), II (greater than 1cm gap between ectopic bone and joint), III (less than 1cm gap), IV (ankylosis) |
Practice these scenarios to excel in your viva examination
"A 68-year-old woman with severe hip osteoarthritis asks about total hip replacement. Describe the Lewinnek safe zone and explain its clinical significance in preventing dislocation."
"You are planning primary THA for a 55-year-old active male with osteoarthritis. What does the AOANJRR data show regarding implant selection, specifically comparing cemented versus uncemented fixation and polyethylene options?"
"Describe your systematic approach to trialing and stability assessment during primary THA via posterior approach. What would you do if the hip feels unstable posteriorly during trialing?"
High-Yield Exam Summary
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. doi:10.2106/00004623-197860020-00014
Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR). Hip, Knee & Shoulder Arthroplasty: 2023 Annual Report. Adelaide: AOA; 2023.
Ranawat CS, Maynard MJ. Modern techniques of cemented total hip arthroplasty. Tech Orthop. 1991;6(3):17-25.
Abdel MP, von Roth P, Jennings MT, Hanssen AD, Pagnano MW. What safe zone? The vast majority of dislocated THAs are within the Lewinnek safe zone for acetabular component position. Clin Orthop Relat Res. 2016;474(2):386-391. doi:10.1007/s11999-015-4432-5
Khatod M, Barber T, Paxton E, Namba R, Fithian D. An analysis of the risk of hip dislocation with a contemporary total joint registry. Clin Orthop Relat Res. 2006;447:19-23. doi:10.1097/01.blo.0000218752.22613.78
Callanan MC, Jarrett B, Bragdon CR, et al. The John Charnley Award: risk factors for cup malpositioning: quality improvement through a joint registry at a tertiary hospital. Clin Orthop Relat Res. 2011;469(2):319-329. doi:10.1007/s11999-010-1487-1
Kurtz SM, Gawel HA, Patel JD. History and systematic review of wear and osteolysis outcomes for first-generation highly crosslinked polyethylene. Clin Orthop Relat Res. 2011;469(8):2262-2277. doi:10.1007/s11999-011-1872-4
White RE Jr, Forness TJ, Allman JK, Junick DW. Effect of posterior capsular repair on early dislocation in primary total hip replacement. Clin Orthop Relat Res. 2001;(393):163-167. doi:10.1097/00003086-200112000-00019
Falck-Ytter Y, Francis CW, Johanson NA, et al. Prevention of VTE in orthopedic surgery patients: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2 Suppl):e278S-e325S. doi:10.1378/chest.11-2404
Grammatopolous G, Pandit HG, da Assunção R, et al. Pelvic position and movement during hip replacement. Bone Joint J. 2014;96-B(7):876-883. doi:10.1302/0301-620X.96B7.32107