Aetiology
- Residual dysplasia after DDH leaves a shallow, anteverted acetabulum with deficient anterolateral cover.
- Perthes disease leaves coxa magna, a short neck and trochanteric overgrowth.
- Slipped capital femoral epiphysis leaves a cam deformity from posterior and inferior slip with neck retroversion.
- Coxa vara shortens the limb and weakens the abductors.
Classification
- Stulberg classes I and II give a spherical head and the best outcome.
- Stulberg classes III and IV give an aspherical but congruent head with earlier osteoarthritis.
- Stulberg class V is a flat head with an incongruent joint and early osteoarthritis.
- Crowe type I is proximal migration under 50 per cent of head height.
- Crowe types II and III are 50 to 75 and 75 to 100 per cent.
- Crowe type IV is a high dislocation above 100 per cent, with a false acetabulum.
Clinical Features
- Dysplasia presents in women in their twenties to forties with groin pain, labral tear and instability.
- Perthes sequelae give Trendelenburg gait from trochanteric overgrowth.
- SUFE sequelae give reduced internal rotation, with obligate external rotation on flexion.
Investigations
- Lateral centre-edge angle below 20° indicates dysplasia and 20 to 25° is borderline.
- Broken Shenton line indicates subluxation.
- CT or MRI assesses femoral version, labrum and cartilage.
Management
- Periacetabular osteotomy (Ganz) suits a congruent joint with minimal arthritis, good range and age under about 40.
- Periacetabular osteotomy preserves the posterior column and the acetabular blood supply.
- Valgus intertrochanteric osteotomy treats coxa vara and Perthes with a hinge abduction deformity.
- Cam resection by arthroscopy or surgical hip dislocation treats mild SUFE and Perthes impingement.
- Surgical hip dislocation with a Dunn procedure or flexion osteotomy corrects moderate to severe slip.
- Surgical hip dislocation protects the medial femoral circumflex artery.
- Arthroplasty in dysplasia needs a small cup placed at the true acetabulum with superolateral graft for uncovering.
- The femoral canal is narrow, needing small or modular stems.
- Excess femoral anteversion in arthroplasty raises dislocation risk.
- Crowe IV needs subtrochanteric shortening osteotomy.
Complications
- Lengthening over about 4 cm risks sciatic nerve palsy.
- Avascular necrosis follows unstable slip and neck osteotomy.
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 12 October 2026.