Primary Total Hip Arthroplasty

Indication. End-stage hip arthritis with pain limiting daily activities, night pain and functional decline that has failed conservative management (analgesia, activity modification, physiotherapy, weight loss). Radiographs show the triad of osteoarthritis — joint-space loss, osteophytes and subchondral sclerosis with cyst formation. Primary idiopathic osteoarthritis is the most common elective indication. The same operation serves a broad set of secondary causes: - Secondary osteoarthritis — developmental dysplasia of the hip (DDH; demands careful templating and often specialist cups), avascular necrosis, post-traumatic arthritis after acetabular or femoral fracture, and the adult sequelae of SUFE or Perthes disease.

• Inflammatory arthritis — rheumatoid arthritis (often bilateral, poor bone stock, younger patients) and ankylosing spondylitis (a fixed spinal deformity alters cup positioning and spinopelvic mobility).
• Acute fracture — a displaced intracapsular neck-of-femur fracture in an active, independent elderly patient with good life expectancy, where total hip arthroplasty outperforms hemiarthroplasty. Contraindications

Preoperative planning. Calibrated templating of an AP pelvis and a lateral femur determines cup size and position (restoring the centre of rotation at the teardrop), stem size, neck length and offset, and the planned leg-length restoration (teardrop to lesser trochanter, bilaterally). Identify bone defects that need augmentation. Approach selection — four options, one default.

Fixation and bearing — a global registry picture. Cementless acetabular components dominate in nearly every high-volume registry (roughly 90 percent of primary cups). Femoral fixation diverges by region: cementless stems predominate in Australia and North America, while the UK NJR and the Nordic registries retain a substantial share of cemented and hybrid stems, particularly in patients over 70-75 years and in osteoporotic bone — because cemented stems virtually eliminate early periprosthetic femoral fracture in the elderly. Ceramic-on-highly-cross-linked-polyethylene and metal-on-XLPE are the dominant bearings; metal-on-metal has been abandoned. Consent specifically for dislocation (and the precautions that prevent it), leg-length discrepancy, sciatic nerve injury (foot drop), periprosthetic fracture, infection (PJI), VTE, and the long-term reality that roughly 58 percent of hips last 25 years on registry data. Setup. Lateral decubitus with the pelvis perpendicular to the floor and securely supported at the sacrum and symphysis (position is the commonest cause of cup malposition). Regional anaesthesia preferred. Mark the greater trochanter, ASIS, PSIS and the femoral shaft axis, and drape the leg free so it can be manoeuvred for dislocation.

The goal is to expose the hip through the posterior approach, remove the arthritic femoral head, implant an acetabular cup in the safe zone and a femoral stem at the correct version and offset, confirm stability, and close with a meticulous capsular and short-rotator repair that protects against dislocation. The exposure — the heart of the operation — is laid out as the first steps below.

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Rehabilitation | Phase | Timing | Milestones & precautions | |-------|--------|--------------------------| | Immediate | Day 0-1 | Multimodal analgesia; VTE prophylaxis (aspirin or a DOAC/LMWH for 28-35 days); sit out of bed and mobilise full weight-bearing as tolerated (uncemented) | | Early | Weeks 1-6 | Posterior precautions (no flexion beyond 90 degrees, no adduction past midline, no internal rotation); wound review at 2 weeks; AP pelvis radiograph | | Recovery | Week 6 to 3 months | Discontinue precautions if the capsule was repaired; driving, walking, swimming; sedentary work | | Return to activity | 3-6 months | Cycling, doubles tennis, golf; avoid running, jumping and contact sports | Long-term surveillance is registry-based: review at 1, 5 and 10 years with an AP pelvis, then periodically for life, and enrol every implant in the national joint registry (NJR, AOANJRR, AJRR, SHAR and others). Complications

Heterotopic ossification occurs in 10-30 percent of cases and is graded by Brooker:

Pathoanatomy. End-stage hip osteoarthritis is progressive cartilage loss with subchondral sclerosis, cyst formation and marginal osteophytes, culminating in joint-space loss, pain and stiffness. Total hip arthroplasty replaces both the acetabular and femoral articular surfaces with durable bearings, restoring a painless, stable, mobile hip. Fixation and bearing — the global registry picture.

Implant survival and outcomes. Pooled national-registry data (Evans, Lancet 2019) give construct survival of about 95 percent at 10 years, about 89 percent at 15 years and about 58 percent at 25 years for primary OA — figures to quote from registries rather than case series, which over-estimate survival at around 78 percent at 25 years. Roughly 90-95 percent of patients report significant pain relief and functional improvement. The leading reasons for revision are aseptic loosening, infection and dislocation. Guidelines, registries and global practice. AAOS appropriate-use criteria and NICE TA304 both endorse THA for end-stage hip OA refractory to conservative care. The major registries — NJR (UK), AOANJRR (Australia), AJRR (US), SHAR (Sweden) and the Norwegian and New Zealand registries — are the gold standard for implant surveillance; the AOANJRR (since 1999) and the Nordic registries hold the longest continuous datasets. Every implant should be enrolled in the national registry.