Paediatrics: Hip disorders: Perthes’ disease

Hip disorders: Perthes’ disease

Also known as Legg–Calve–Perthes disease. It is due to an idiopathic osteonecrosis (avascular necrosis) of the femoral head of unknown aetiol-ogy. Incidence: 1:10,000

Risk factors

Boys > girls (4:1); age 4–10yrs. <20% bilateral (usually staged + asym-metric), 10% family history, low birth weight, 4% children with transient synovitis, delayed skeletal maturity.

Aetiology

Unknown, although several risk factors lead to avascular necrosis: trauma, endocrine (e.g. hypothyroidism, renal disease, steroids), metabolic, coagu-lability (blood dyscrasia, protein C or S deficiency, thrombophilia).

Differential diagnosis

•   Multiple epiphyseal dysplasia.

•   Spondyloepiphyseal dysplasia.

•   Hypofibrinolysis.

•   Slipped upper femoral epiphysis (SUFE).

•   Septic arthritis.

•   TB of hip.

•   Trauma.

•   SCD.

Pathological stages

•   Avascular: hip appears sclerotic with minimal loss of epiphyseal height

•   Fragmentation: initially fissures appear in epiphysis, followed by more severe fragmentation and loss of height.

•   Remodelling: regeneration, new bone formation, and head remodelling

•   Healed: no avascular bone visible on radiographs

Symptoms 

Mild/intermittent anterior thigh/groin/referred knee pain with limp; classical ‘painless limp’. Note: Knee pain: beware hip pathology.

Special signs

•   Look: proximal thigh atrophy, mild short stature, limp/Trendelenburg/ antalgic gait common.

•   Feel: effusion (from synovitis), groin/thigh tenderness.

•   Move: decreased hip range of movement (especially abduction and internal rotation) with muscle spasm.

Investigations

• AP and lateral pelvic X-rays: many different classifications, but most useful is lateral pillar classification. The femoral head is divided into thirds. Group A no loss of height of lateral 1/3, B up to 50% loss of height, group C >50% loss of height.

• MRI may help diagnosis especially in the early stages.

• Technetium 99 bone scan: decreased uptake in femoral epiphysis due to poor vascular supply.

• Dynamic arthrography to delineate hip joint and plan surgery.

Prognosis

This is a local self-healing disorder. Prognosis depends on bone age and

X-ray appearances. Poor prognostic indicators are:

• Clinical: heavy child; ‘fall’ range of movement; adduction contracture;

flexion into abduction, female and older age at presentation (> 6yrs).

• Radiological: Gage’s sign; lateral subluxation of femoral head with lateral calcification; whole head involvement; metaphyseal cysts; lateral pillar group C hips.

Treatment is controversial

The aims are to relieve symptoms and signs by eliminating hip irritability and maintaining hip range of movements. This is achieved by:

• Maintaining sphericity of femoral head.

• Containing femoral head in acetabulum whilst remodelling occurs.

• Preventing epiphyseal collapse and secondary osteoarthritis.

Non-operative treatment 

Observation and activity modification, includ-ing bed rest and walking aids. NSAIDs, physiotherapy. Bracing is controversial.

Operative treatment 

Femoral/pelvic osteotomies to contain femoral head in acetabulum.