Hip Anterolateral Approach (Watson-Jones)

What it exposes. The Watson-Jones anterolateral approach gives direct access to the hip joint, the femoral neck and the acetabulum through the interval between tensor fasciae latae (anterior) and gluteus medius (posterolateral). It is a workhorse exposure for primary total hip arthroplasty and femoral neck fracture management, and can be performed with the patient supine or lateral decubitus. Why anterolateral (and not anterior or posterior). It is frequently confused with the anterior (Smith-Petersen) approach - a common exam trap. Watson-Jones uses the TFL–gluteus medius interval (both supplied by the superior gluteal nerve, so NOT internervous), whereas Smith-Petersen uses the TFL–sartorius interval (superior gluteal versus femoral nerve, a TRUE internervous plane). Versus the posterior approach, anterolateral preserves the posterior capsule and short external rotators, giving a lower dislocation rate at the cost of higher abductor risk. Historical context. Sir Reginald Watson-Jones described the approach in 1936 for hip arthrodesis and fracture management. It was popular through the 1950s to 1970s, fell from favour in the 1980s to 1990s due to abductor complications, and was revived in the 2000s with muscle-sparing modifications (the Röttinger/OCM intermuscular variant) that split TFL rather than detaching it. Indications.

Contraindications. - Relative: severe obesity (BMI over 40) - difficult exposure and higher complication rate; prior anterolateral surgery with known abductor damage; pre-existing superior gluteal nerve palsy; severe osteoporosis (fracture risk with retraction).

• Active infection is a general contraindication to elective arthroplasty. Position & landmarks. Supine (with a bump under the ipsilateral hip, allowing 20 to 30 degrees of pelvic tilt) suits trauma, permits bilateral procedures and eases anaesthesia. Lateral decubitus (pelvis held perpendicular to the floor with anterior and posterior supports) gives better acetabular exposure as gravity assists. Palpate and mark the greater trochanter (primary landmark), the ASIS and the iliac crest, and plan a curvilinear incision centred over the trochanter. The defining concept: not a true internervous plane. The interval lies between TFL and gluteus medius, but both are supplied by the superior gluteal nerve (L4 to S1), so this is an intranervous interval rather than an internervous one. The superior gluteal nerve exits the pelvis through the greater sciatic notch superior to piriformis, divides into a superior branch (to gluteus medius and minimus) and an inferior branch (to TFL), and crosses the interval about 5 cm proximal to the greater trochanter tip - the origin of the 5 cm rule that governs proximal dissection.

Deep structures encountered: the hip joint capsule (accessed after splitting TFL and reflecting gluteus medius), the reflected head of rectus femoris from the superior acetabular rim, the iliofemoral ligament (strongest hip ligament, anterior capsule), and the ascending branch of the lateral circumflex femoral artery running deep, which requires ligation.

Work from skin down to capsule along the TFL–gluteus medius interval, protecting the superior gluteal nerve and the abductors at every step. The muscle-sparing modification is the modern standard - split TFL rather than detach it.

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Structures at risk, by layer

Complication rates. - Superior gluteal nerve injury: 1 to 5 percent, producing a Trendelenburg gait.

• Abductor muscle damage: 5 to 15 percent, technique-dependent.
• Heterotopic ossification: 10 to 20 percent overall (higher than posterior); clinically significant Brooker grade III to IV in 3 to 5 percent.
• Dislocation: under 2 percent (lower than the posterior approach).

• Total hip arthroplasty - the principal operation. Acetabular targets are about 40 to 45 degrees inclination and 15 to 20 degrees anteversion; the femoral stem is set at about 10 to 15 degrees anteversion, with offset and leg length restored and stability confirmed on trial reduction.
• Femoral neck fracture - quick joint access for hemiarthroplasty or THA in the elderly, and exposure for screw fixation in the young displaced or non-displaced fracture; supine positioning suits the trauma setting.
• Revision THA (acetabular) - excellent cup and liner exposure; less suited to complex femoral revision (posterior preferred).
• Hip arthroscopy conversion - the anterolateral portal uses the same anatomical corridor, allowing conversion to open if arthroscopy cannot be completed.
• Hip arthrodesis (historical) - Watson-Jones' original indication; rarely performed in modern practice. Postoperative course. Mobilise on day 0 to 1 with full weight-bearing as tolerated (modern implants); abductor strengthening is especially important for this approach. Hip precautions after anterolateral THA are controversial - many surgeons use none, while some avoid extremes of flexion, adduction and internal rotation for 6 weeks. VTE prophylaxis follows local protocol (for example rivaroxaban 10 mg daily, enoxaparin 40 mg daily, or aspirin 100 mg daily) combined with mechanical prophylaxis and early mobilisation. Follow up at 2 weeks (wound check and staple removal), 6 weeks, 3 months, 1 year, then annually; most patients reach maximum improvement by 6 to 12 months.

Guidelines, registries and global practice. - Global practice variation: the anterolateral (Watson-Jones or Röttinger) interval is used worldwide but is less common than the posterior and direct lateral approaches in most national registries; it is more popular in parts of continental Europe (where the Röttinger/OCM muscle-sparing variant originated) than in the UK or North America. Surgeon training and familiarity, rather than country, drive approach choice.

• Registry evidence (approach and outcomes): major arthroplasty registries (NJR for England, Wales and Northern Ireland; AJRR in the US; AOANJRR in Australia; the Swedish and Norwegian registries) record surgical approach and track approach-specific revision and dislocation. Across registries, primary THA implant survival is broadly equivalent between approaches when performed by experienced surgeons; differences in early dislocation and revision-for-instability are the main approach-related signals. Abductor-based approaches show a lower dislocation risk but a higher loosening and abductor-deficiency signal than the posterior approach in pooled data.
• Named-society guidance (side by side): AAOS (US) and NICE or BOA (UK) do not mandate a specific approach for primary THA and emphasise surgeon experience and audited outcomes; AO Foundation and EFORT (Europe) recognise the muscle-sparing anterolateral interval as a valid exposure for primary THA and displaced femoral neck fracture. All major societies agree that informed consent must include approach-specific risks.
• Informed consent (approach-specific): superior gluteal nerve injury and Trendelenburg gait (temporary versus permanent weakness), heterotopic ossification and the role of prophylaxis in high-risk patients, and documentation of the discussion.
• Venous thromboembolism prophylaxis: follow current national society guidance (for example AAOS, NICE or equivalent); combine mechanical and pharmacological prophylaxis with early mobilisation. Agents include aspirin, low-molecular-weight heparin, or a direct oral anticoagulant per local protocol and individual risk.