Makindo Medical Notes.com

An idiopathic avascular necrosis/osteonecrosis of the femoral epiphysis

About

• Idiopathic avascular necrosis/osteonecrosis of the femoral epiphysis
• Osteonecrosis of the proximal femoral epiphysis
• Flattening and fragmentation of epiphysis

Aetiology

• Avascular necrosis and deformation
• Revascularisation then occurs
• Cycle repeats every 2-4 weeks

Cause

• Unknown. Seen in 1 in 10,000
• Age 5-7 (range 3-12) and Boys > Girls 4:1
• Bilateral in 10% of cases

Clinical

• Present with limp and hip pain without trauma
• Examination of the knee is normal
• Limited and painful rotation and abduction of the ipsilateral hip
• Internal rotation is usually affected more than external rotation

Differentials

• Synovitis
• Septic arthritis
• Juvenile idiopathic arthritis

Investigations

• FBC, U&E, ESR: normal
• X-Ray/CT: joint effusion with the widening of the medial joint space asymmetrical femoral epiphyseal size (smaller on the affected side) apparent increased density of the femoral head epiphysis blurring of the physeal plate. Radiolucency of the proximal metaphysis. Later signs include femoral head deformity with widening and flattening (coxa plana), proximal femoral neck deformity: coxa magna, "sagging rope sign" (the thin sclerotic line running across the femoral neck)
• Hip USS: effusion

Catterall classification

• Stage I: bone absorption changes visible in the anterior aspect of the epiphysis of femoral head changes are visible best in frog-leg lateral view no sclerosis is seen
• Stage II: further bone resorption with the slight femoral head collapse in the anterior aspect of femoral head sclerosis
• Stage III: almost entire femoral head involved in collapse with characteristic head within head appearance sclerosis
• Stage IV: the complete collapse of the femoral head with flattening and formation of dense sclerosis; additional metaphyseal changes may be visible sclerosis posterior remodelling

Differentials of other causes of Osteonecrosis

• Trauma
• Leukaemia, lymphoma, systemic lupus erythematosus
• Haemoglobinopathies
• Coagulopathies
• Corticosteroid treatment.

Management

• Containment of the femoral head helps prevent deformity and restore motion. Later degenerative arthritis may develop. Treatment consists of rest from aggravating activities and range of motion exercises.
• Prognosis is largely dependent on the amount of femoral head involved, with a recent study citing femoral head involvement of more than 50% as the strongest predictor of poor outcome. Age greater than 6 years also conferred a worse prognosis than younger children
• Age onset < 6 then manage symptoms and outcome good
• Age onset 6-8 year: containment with brace or surgery
• Age > 8 needs surgical intervention with femoral/pelvic osteotomy

References