Paediatrics: Hip disorders: slipped upper femoral epiphysis

Hip disorders: slipped upper femoral epiphysis

Displacement of the upper femoral epiphysis on the metaphysis through the hypertrophic zone of the growth plate. The femoral neck displaces anteriorly and the head remains in the acetabulum.

•   Incidence: the most common adolescent hip disorder (3:100 000); 25–60% bilateral.

•   Risk factors: African American, >50% obese (weight >95th percentile), positive family history, puberty, boys (12–16yrs) > girls (10–14yrs).

•   Aetiology: unknown, but associated with the following:

•   Endocrine—hypothyroidism, hypogonadism, renal osteodystrophy;

•   Mechanical—retroversion of femoral neck or vertical growth plate;

•   Other—Down syndrome, radiotherapy/chemotherapy.

Symptoms and signs

Groin, thigh, or knee pain. Antalgic gait, limited hip fl exion and abduction, flexion into external rotation, and thigh atrophy.

Always 

consider hip pathology in a child presenting with knee pain.

Presentation

Characterized by 2 broad types of children.

•   Obese hypogonadal (low circulating sex hormones): delayed skeletal maturation bone age.

•   Tall thin, often boys, post growth spurt (younger age in girls): overabundance of growth hormones.

Diagnostic classification

This is based on duration of symptoms.

•   Preslip: wide epiphysis; mild discomfort, but normal examination; often seen on contralateral hip.

•   Acute slip: mild symptoms <3wks, then sudden slippage usually without trauma; pain so severe child unable to weight bear; usually unstable.

•   Acute on chronic: acute slip on pre-existing chronic slip; usually have previous symptoms (pain, limp, out toe gait) for several months; unable to weight bear; usually unstable.

•   Chronic: most common type; history for several months; symptoms worsen as slip progresses; child able to walk with mildly antalgic externally rotated gait. Usually stable.

•   Slips may be further sub-classified into stable or unstable (Loder): in an unstable slip’ child unable to weight bear, even with crutches, and cannot do straight leg raise actively. These have increased risk of AVN.

Investigations

• X-Ray: AP pelvis and frog lateral hips. Widening of physis, Klein’s line intersects lateral capital epiphysis on AP.

• MRI: useful in pre-slip diagnosis, and evidence of AVN.

• Endocrine tests: if appropriate, e.g. thyroid function.

Treatment

The aim is to prevent further ‘slippage’ and to minimize complications. Operative

Usually pin in situ (to encourage the proximal femoral epiphysis to close, hence preventing further slippage); usually not reduced as manipulation may increase the incidence of avascular necrosis. Prophylactic pinning of opposite hip is controversial. It is recommended in younger children and those with endocrinopathy.

Complications

• Chondrolysis (degeneration of the articular cartilage of the hip with narrowed joint space, pain, decreased motion): associated with more severe slips; occurs more frequently among African American children and females; associated with pins protruding out of the femoral head.

Osteonecrosis/avascular necrosis (higher incidence in unstable hips): due to injury to retinacular vessels (at time of slip or manipulation) or compression from intracapsular haematoma. Commonly leads to degenerative joint disease. Avascular necrosis uncommon in stable slips.