Surgical Approaches to the Hip

The four workhorse approaches to the hip are the posterior (Moore/southern), the direct lateral (Hardinge, trans-gluteal), the anterolateral (Watson-Jones) and the direct anterior (Smith-Petersen). Only the direct anterior approach uses a true internervous plane; the others rely on muscle splits or detachments, and each trades exposure against a characteristic risk — sciatic nerve injury and dislocation posteriorly, abductor and superior gluteal nerve damage laterally. In UK practice the posterior approach dominates elective total hip replacement (THR), while lateral-family approaches remain popular for hemiarthroplasty.

What planes and intervals define each approach?

Interviewers expect the intervals stated precisely, superficial then deep, with the innervation that makes a plane "internervous" (or not).

What should you say about the posterior approach?

With the patient in lateral decubitus, the incision is centred on the greater trochanter and curved posteriorly. Gluteus maximus is split bluntly in line with its fibres, the short external rotators are tagged and released close to their femoral insertion, and the posterior capsule opened; the hip dislocates by flexion, adduction and internal rotation. The sciatic nerve lies on the short external rotators and is protected by them if the rotators are divided at the bone and reflected posteriorly; direct visualisation is not routinely required, but retractor placement must respect it. Preserving quadratus femoris protects the deep branch of the medial femoral circumflex artery — the dominant blood supply to the femoral head — which matters when the head is being retained (fracture fixation, surgical dislocation) rather than replaced. The abductors are untouched, which is the great functional advantage. The historic weakness is posterior instability, substantially mitigated by meticulous repair of the capsule and short rotators, appropriate component version and larger head sizes.

How do the direct lateral and anterolateral approaches differ?

Hardinge's direct lateral approach, described in 1982, splits gluteus medius in line with its fibres and continues distally through vastus lateralis, elevating the anterior portions of medius and minimus in continuity as an anterior flap off the trochanter. Its defining hazard is the superior gluteal nerve, which runs between gluteus medius and minimus. In the classic cadaveric study, Jacobs and Buxton reported that "the so-called safe area of the gluteus medius muscle was found to be as much as five centimeters adjacent to the greater trochanter" — hence the commonly quoted rule of not extending the gluteal split more than 3–5 cm proximal to the tip of the trochanter. The price of trans-gluteal exposure is abductor morbidity: failure of the repair or nerve injury produces abductor weakness and a Trendelenburg gait.

The anterolateral (Watson-Jones) approach instead uses the intermuscular interval between tensor fasciae latae and gluteus medius. Because both muscles share superior gluteal innervation it is not a true internervous plane, and the nerve remains at risk proximally. Anterior capsular exposure is good, femoral access requires abductor retraction, and posterior structures are left completely undisturbed — one reason it is favoured by many units for hemiarthroplasty.

What about the direct anterior approach?

The direct anterior approach exploits the only true internervous plane to the hip: sartorius/tensor fasciae latae superficially and rectus femoris/gluteus medius deep, femoral nerve territory medially and superior gluteal territory laterally. The lateral femoral cutaneous nerve crosses the superficial interval and is the most commonly injured structure; the ascending branch of the lateral femoral circumflex artery crosses the deep interval and must be ligated. It is muscle-sparing and popular for rapid early recovery in elective THR, but femoral exposure is the difficult step — elevation and external rotation of the femur risk perforation, calcar fracture and trochanteric injury, and there is a well-recognised learning curve. It is also the classical approach for open reduction of developmental dysplasia and for anterior drainage of the septic hip.

How does approach choice affect dislocation and abductor function?

This is the crux of the interview question. The posterior approach spares the abductors but breaches the posterior soft-tissue envelope; the lateral approaches protect against posterior dislocation but at the cost of the abductor mechanism. A systematic review and meta-analysis of prospective studies (Berstock et al., 2015) found that, compared with the lateral approach, the posterior approach significantly reduced the risk of Trendelenburg gait (OR 0.31) and stem malposition, with a non-significant reduction in dislocation — so modern repair techniques appear to have neutralised the traditional dislocation argument against the posterior approach. At registry scale, the analysis of 723,904 elective THRs from the National Joint Registry (Blom et al., BMC Medicine 2020) found lateral approaches associated with more revisions, more self-reported complications and higher 90-day mortality, concluding: "We recommend the posterior approach should be considered the current standard approach for THR."

Which approach for which operation?

• Elective THR: posterior is the commonest UK approach and the registry-supported standard; direct lateral and direct anterior remain acceptable according to surgeon training and patient factors.
• Hip hemiarthroplasty for intracapsular fracture: many UK units prefer an anterolateral or direct lateral approach in frail patients to minimise dislocation risk in a group poorly tolerant of instability — this is established good practice rather than a mandated standard, and either approach is defensible if performed well.
• Revision THR: posterior, because it is extensile proximally and distally and can be converted to an extended trochanteric osteotomy.
• Posterior acetabular and hip fracture-dislocation surgery: the Kocher-Langenbeck approach, the trauma extension of the posterior interval.
• Paediatric open reduction (DDH) and drainage of septic arthritis: anterior (Smith-Petersen), or an anterolateral approach for washout.
• Surgical dislocation for femoral head preservation: a lateral approach with trochanteric flip osteotomy (Ganz), protecting the medial femoral circumflex artery.

Key points

• Only the direct anterior (Smith-Petersen) approach uses a true internervous plane: femoral nerve medially, superior gluteal nerve laterally, at both superficial and deep levels.
• Posterior approach: sciatic nerve at risk on the short external rotators; spares the abductors; instability is mitigated by capsule and rotator repair.
• Direct lateral (Hardinge): superior gluteal nerve at risk if the gluteus medius split extends more than 3–5 cm above the greater trochanter; abductor damage causes Trendelenburg gait.
• Preserve quadratus femoris to protect the deep branch of the medial femoral circumflex artery whenever the femoral head is retained.
• Registry evidence from 723,904 NJR THRs supports the posterior approach as the current standard for elective THR; lateral approaches carry higher revision and complication rates.
• For hemiarthroplasty in the frail hip fracture patient, an anterolateral or lateral approach to reduce dislocation risk is widely regarded as good practice.