Minimally Invasive Posterior THA

Indication. A primary total hip arthroplasty performed through the posterior (posterolateral, Southern/Moore) approach, using a shortened 6–10 cm incision in place of the standard 15–20 cm. The minimally invasive (mini-posterior) variant is the same operation through a smaller window — same surgical principles, same structures at risk, same posterior repair — chosen when the surgeon is experienced with the approach and the patient's body habitus allows safe exposure. Standard indications for THA apply: end-stage hip osteoarthritis, inflammatory arthritis, avascular necrosis, and post-traumatic arthritis. Mini-posterior versus standard posterior — the only real differences are incision length, instrumentation, and learning curve:

• Complex anatomy — dysplasia, prior surgery, post-traumatic stiffness
• Obese patients (better access than a direct anterior approach)
• When excellent femoral exposure is required (a key posterior-approach strength)
• Revision surgery Consent specifically for dislocation (about 1–2 percent with a sound posterior repair, higher if the repair is omitted) and the posterior hip precautions that follow; leg-length discrepancy; sciatic or other nerve injury (about 0.5–1 percent in primary THA); periprosthetic fracture; infection (about 1–2 percent); and the lifetime risk of revision. Setup. Lateral decubitus on a standard table, the pelvis held truly vertical by anterior and posterior posts or a bean-bag, the operative leg free for dislocation and manipulation, all pressure points padded, and the greater trochanter, ASIS and posterior superior iliac spine marked before draping. Pelvic tilt directly changes the cup-orientation read taken off the patient, so a true vertical pelvis is essential — an anteriorly tilted pelvis makes the measured anteversion read less than the true value.

The goal is to expose the hip through the mini-posterior interval, dislocate posteriorly, prepare and implant the acetabular and femoral components under direct vision, and then reconstruct the posterior soft-tissue sleeve (capsule plus short external rotators) through bone — the step that defines the modern posterior approach. The exposure is laid out step by step below.

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Five structures define the danger zones of the posterior approach — know the location of each before you make a cut.

Closure and post-operative care - Irrigate the wound thoroughly (minimum 3 L); reapproximate the gluteus maximus fascia; close the subcutaneous layer with absorbable sutures; close the skin (staples or subcuticular); apply a sterile dressing.

• Weight bearing as tolerated immediately.
• Posterior hip precautions for 6–12 weeks: avoid flexion past 90 degrees, avoid adduction past the midline, and avoid internal rotation.
• VTE prophylaxis per institutional protocol; standard THA rehabilitation pathway. Complications

Posterior versus direct anterior approach. Both are performed worldwide; registry and Level I data show comparable revision and dislocation when each is done by an experienced surgeon. The posterior approach remains the most widely used because of its versatility and excellent femoral exposure.

Guidelines, registries and global practice. - Registry evidence (implant survivorship and dislocation): national joint registries (NJR England and Wales, AOANJRR Australia, SHAR Sweden, Norwegian, NZJR, AJRR USA) consistently report dislocation and instability among the leading early causes for revision after primary THA, alongside infection and periprosthetic fracture.

• Larger femoral head sizes (32 mm and 36 mm) and dual-mobility constructs are associated with lower instability-related revision in registry data, supporting head-size upsizing or dual mobility when intraoperative stability is marginal.
• Practice variation: "hip precautions" practice differs globally — many high-volume centres have moved to relaxed or no precautions after a well-repaired posterior approach, citing equivalent dislocation rates; others retain 6 weeks of flexion, adduction and internal-rotation restriction. Evidence increasingly supports individualised rather than blanket precautions.
• Society guidance: AAOS, NICE and BOA (UK), AO Foundation and EFORT emphasise accurate component positioning, restoration of offset and leg length, and meticulous soft-tissue repair as the determinants of stability — not the specific approach. There is no single mandated approach.