Total Hip Arthroplasty (THA) — Approaches & Complications

Total hip arthroplasty (THA) is one of the most successful operations in all of surgery and the most commonly performed elective orthopaedic procedure worldwide. It reliably relieves pain and restores function in end-stage hip disease. Understanding approaches, implant selection, bearing surfaces, and complications is fundamental knowledge for all orthopaedic surgeons.

• Approximately 2.5 million THAs performed globally each year; numbers increasing as population ages and younger patients are offered surgery
• Primary indications: osteoarthritis (80–85%), rheumatoid arthritis, avascular necrosis, fracture (femoral neck in elderly), dysplasia, post-traumatic arthritis, inflammatory arthropathy, tumour
• Contraindications: active infection (absolute), neurological impairment precluding rehabilitation, severe medical comorbidity, non-ambulatory patient with no pain (relative)
• Timing: failure of conservative management (analgesia, activity modification, physiotherapy, walking aids, weight loss) combined with significant impact on quality of life and radiological evidence of joint destruction
• Oxford Hip Score (OHS): validated patient-reported outcome measure for THA; 12 questions; 0–48 scale (48 = best function); used pre- and post-operatively to assess outcomes and justify surgical intervention

• Posterior approach: most widely used worldwide; highest dislocation risk (3–4% without posterior capsule repair; reduced to ~1% with meticulous posterior capsule and short rotator repair); sciatic nerve injury most feared complication
• Direct anterior approach (DAA): growing in popularity; truly internervous; allows intraoperative fluoroscopy for component positioning; faster rehabilitation in some series; higher learning curve; LFCN injury rate 5–15%; fracture risk in femoral preparation
• Hardinge (direct lateral): associated with abductor lurch (Trendelenburg) from gluteus medius damage if trochanteric reattachment fails — up to 15–20% incidence of persistent Trendelenburg in some series
• Safe zone for superior gluteal nerve: stay within 5 cm proximal to the tip of the greater trochanter in anterolateral and direct lateral approaches

• Cement implantation syndrome (BCIS — bone cement implantation syndrome): hypotension, hypoxia, cardiac arrhythmia, and cardiac arrest at time of cement pressurisation or stem insertion; caused by fat, marrow, and cement monomer embolisation; risk highest in elderly with cardiorespiratory disease; venting the femoral canal reduces risk; anaesthetic team must be alerted before cement insertion
• NJR (National Joint Registry, UK): reports 10-year survivorship for primary THA at approximately 95%; cemented and cementless fixation have equivalent long-term outcomes in appropriate patient selection

• Cross-linked polyethylene (XLPE): radiation cross-linking dramatically reduces polyethylene wear rate (approximately 80% reduction vs conventional PE); now standard bearing in most centres; highly oxidised XLPE (Vitamin E-stabilised) further improves oxidation resistance
• Metal-on-metal: all large-head MoM THAs and resurfacings require annual surveillance — serum cobalt and chromium ion levels; MARS MRI for pseudotumour; MHRA guidance mandates follow-up protocol

• Vancouver classification for periprosthetic femoral fractures: Type A (trochanteric); Type B1 (around/below stem — stem well fixed); Type B2 (stem loose); Type B3 (stem loose + poor bone stock); Type C (below stem); B2/B3 = revision surgery; B1 = ORIF with plates ± cables
• Instability after THA: the most common cause of revision in modern practice in the UK (NJR data); assess component positioning (cup anteversion 15–20°, abduction 40–45° — combined anteversion concept); trochanteric advancement for abductor deficiency; constrained liner for recurrent instability when component position is satisfactory
• Corrosion at modular junction (trunnion corrosion): cobalt-chrome taper corrosion in modular THA generates local metal debris even without MoM bearing surface; adverse local tissue reaction (ALTR) mimicking infection; elevated serum cobalt; MARS MRI for assessment; may require modular head exchange
• THA in dysplasia: complex anatomy — high hip centre, deficient acetabular bone stock, femoral deformity, short femur; may require acetabular augmentation (structural allograft, cage, augment), true acetabular cup placement even at high position, and modular or custom femoral stems; high-volume surgeon and centre
• Obesity and THA: BMI >40 associated with higher complication rates (infection, dislocation, VTE, wound problems); frank discussion with patient; optimise BMI pre-operatively; some centres set BMI threshold (<40) before listing

• Posterior approach: highest dislocation risk; sciatic nerve at risk; posterior capsule + short rotator repair reduces dislocation to ~1%
• Hardinge (direct lateral): Trendelenburg from abductor damage; superior gluteal nerve at risk if >5 cm above GT
• DAA: truly internervous (sartorius vs TFL); LFCN injury 5–15%; fluoroscopy-guided component positioning; steeper learning curve
• BCIS: bone cement implantation syndrome; hypotension + hypoxia at cement pressurisation; warn anaesthetist; vent femoral canal
• Cup position safe zone: 40–45° abduction, 15–20° anteversion; combined anteversion concept guides component orientation
• XLPE: 80% reduction in polyethylene wear vs conventional PE — now standard
• MoM: ALVAL, pseudotumour, elevated Co/Cr — largely abandoned; annual surveillance with MARS MRI and ion levels for existing MoM patients
• Vancouver B2/B3 PPF: loose stem = revision; B1: well-fixed stem = ORIF
• PJI: two-stage revision gold standard for chronic infection; DAIR for acute (<3 weeks, well-fixed implant, biofilm-susceptible organism)
• VTE prophylaxis: 28 days post-THA (LMWH or rivaroxaban) — NICE guideline