Hip Posterior Approach (Moore/Southern)

What it exposes. The posterior (Moore/Southern) approach gives versatile, extensile access to the hip joint — the femoral head and neck, the acetabulum (with particularly good exposure of the posterior wall and column), and the proximal femur. It is the workhorse exposure for primary total hip arthroplasty, hemiarthroplasty for femoral neck fracture, and many revision procedures, and it remains the most commonly used approach to the hip worldwide. The eponyms. The approach was popularised by Austin Moore in the 1950s (and the eponymous Austin Moore prosthesis); the "Southern" name derives from the Southern General Hospital, Glasgow. The two terms are used interchangeably for the same exposure. Why posterior. The decisive advantage is the only true internervous plane of any hip approach — between gluteus maximus (inferior gluteal nerve) and gluteus medius (superior gluteal nerve) — so no muscle is denervated and abductor function is preserved. It is extensile in both directions, gives superb posterior-column exposure for trauma and revision, and avoids abductor takedown. Its chief weaknesses are posterior instability if the soft tissues are not repaired, and the sciatic nerve lying in the field.

Position and landmarks. Lateral decubitus with the operative hip uppermost. The single most important factor is the pelvis perpendicular to the floor — any tilt causes an equivalent error in cup anteversion (check with fluoroscopy: obturator foramina symmetric, coccyx midline). Pad well (an axillary roll, and padding between the knees), flex the lower knee 90 degrees for comfort, and leave the operative leg free to move through the full flexion-adduction-internal-rotation arc needed for dislocation and trial reduction. Mark the greater trochanter and the posterior border of the femur to guide the incision.

Global utilisation. Major registries (UK NJR, AOANJRR, NZJR, Swedish/SHAR) all show the posterior approach is the most frequently used exposure for primary THA, with the direct lateral and anterior approaches making up most of the remainder. Crucially, no clinically meaningful difference in long-term revision rate exists between the three approaches in registry data — the approach influences dislocation and abductor-related complications more than overall survival.

Work straight down through the layers from skin to capsule: split gluteus maximus on its internervous plane, use the piriformis as the guide to the short external rotators, and finish with a transosseous repair of the posterior soft tissues — the step that defines a modern posterior approach.

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Structures at risk, by layer

Moore versus Southern

Current consensus: capsular repair is more important than piriformis preservation for preventing dislocation. Either variant is acceptable provided the posterior capsule and short external rotators are repaired. Component position and the safe zone

• Sciatic or motor nerve palsy: roughly 0.5-2% transient, 0.1-0.5% permanent. Risk factors: revision surgery, DDH, lengthening over 4cm, direct trauma. Only about 36% of complete palsies recover fully (Farrell), so prognosis is guarded; manage with an ankle-foot orthosis, physiotherapy, and exploration if progressive or a compressive cause is found.
• Heterotopic ossification: 20-40% radiographic, 5-10% symptomatic. Risk: male gender, DISH, hypertrophic OA, prior HO. Prevent with indomethacin or single-dose radiation (7 Gy); excise if symptomatic after maturation (12 months or more). Extensile options. Extend proximally along the ilium for high-riding DDH or posterior column work (stay under 5cm above the trochanter to protect the superior gluteal nerve); extend distally along the posterior femur for shaft fracture or revision femoral work. The same incision becomes the Kocher-Langenbeck approach for posterior wall and column acetabular fractures. Closure. Re-attach the capsule and short external rotators to the greater trochanter through transosseous tunnels with heavy non-absorbable suture (tendon-to-bone is the most effective technique), close the gluteal split and fascia lata, and close the skin in layers. With a secure repair, many enhanced-recovery pathways use reduced or no hip precautions.

• Primary total hip arthroplasty — the principal operation done through this exposure.
• Posterior approach THA (Kocher-Langenbeck modified) — the standard workhouse THA.
• Minimally invasive posterior THA and SuperPATH tissue-sparing posterior — posterior-based, abductor-sparing variants.
• Revision THA (acetabular component) — direct access to the posterior column and wall.
• Hemiarthroplasty for displaced femoral neck fracture.
• Posterior wall and column acetabular fracture fixation (the Kocher-Langenbeck variant).
• Compatible with ceramic bearings, dual-mobility cups and cemented or cementless femoral stems for stability and fixation strategy.

Registry and society guidance. The posterior approach is the most commonly used approach for primary THA across major registries (UK NJR, AOANJRR, NZJR, SHAR), with no clinically significant difference in long-term revision between posterior, direct lateral and anterior approaches. AAOS (US) and NICE / BOA (UK) both emphasise accurate component position, adequate head size and posterior soft-tissue repair to minimise instability; AO Foundation and arthroplasty consensus recommend transosseous tendon-to-bone repair when a posterior approach is used.