The proximal femoral physis and epiphysis are located within the hip capsule. Although the proximal physis provides length and shape to the femoral neck, most SCFEs occur in adolescence, when little growth remains at this growth plate.

The blood supply to the proximal femoral epiphysis comes from the medial femoral circumflex artery, which travels along the femoral neck. From the circumflex arise the lateral epiphyseal vessels, which enter the epiphysis posterosuperiorly. Small contributions come from the vessels of the round ligament and the posterior inferior epiphyseal vessels off the medial femoral circumflex artery. Injury to this tenuous capsular blood supply can result in osteonecrosis.

In SCFE, the epiphysis stays within the acetabulum while the neck and distal femur slip (most commonly into extension and varus).

SCFE occurs more commonly in boys than girls (60% of patients are boys). Most patients (up to 75%) are adolescents (boys 13.5 years, girls 12.0 years on average). Most patients are obese and in the 90th to 95th weight percentile for age. SCFE occurs bilaterally in about 25% of patients.⁹

Biochemical factors likely play a role. Hormonal changes that occur during adolescent growth influence the strength of the physis.⁴

Biomechanical factors also likely play a role. The physis in SCFE is subjected to higher shear force. The physis is more oblique during adolescence and in obese children; both factors increase shear in normal activities. The proximal femur is relatively retroverted in many cases of SCFE, which also increases the shear force on the physis. The reinforcing perichondral ring of the proximal physis also weakens with age until growth plate closure.

If the physis of an SCFE patient is studied histologically, it looks widened, with abnormal chondrocyte maturation and endochondral ossification. The slip occurs mainly through the hypertrophic zone of the physis.⁶

Patients younger than age 10 years should be evaluated for an underlying endocrine abnormality, including hypothyroidism, renal osteodystrophy, and panhypopituitarism.¹¹

The natural history of untreated SCFE and the ultimate outcome are difficult to predict, although it is widely accepted in adult reconstructive circles that most cases of degenerative hip arthritis are secondary to an underlying structural cause, such as SCFE. The risk of progression exists while the physis remains open. The slip severity increases with the duration of symptoms.⁷

The development of degenerative joint disease is related to the severity of the slip.³

Physical examination methods include the following:

Patients complain of hip or groin pain, thigh pain, or knee pain, which may be exertional and usually occurs without a history of trauma.

The patient may have a limp (stable slip) or frank inability to ambulate (unstable slip).

Examination of the hip can reveal an externally rotated foot and knee, guarding of the hip with ROM, and decreased flexion and internal rotation of the hip.

Findings on the knee examination are normal.

Plain radiographs of the pelvis, including anteroposterior (AP) and frog-leg lateral views, should be obtained in any pediatric patient with hip, thigh, or knee pain.

A widened physis on AP or lateral views can be an early sign of SCFE.

The Klein line, which can demonstrate SCFE, is drawn along the superior neck of the femur, on the AP view. In a normal hip, this line should touch at least some part of the epiphysis, but in SCFE, it will not cross the epiphysis (FIG 1).

The metaphyseal blanch sign of Steel is a crescent-shaped double density along the medial femoral neck where the slipped epiphysis overlaps the metaphysis on the radiograph.

Images of the contralateral hip should be scrutinized for evidence of bilateral SCFE. If present, both sides should be treated.

The severity of an SCFE can be described by displacement relative to the width of the metaphysis⁷:

Another method of describing slip severity is measuring the difference between the epiphyseal shaft angle on each side¹⁶:

If the patient is younger than 10 years of age, underlying endocrine abnormalities should be investigated with laboratory studies, including thyroid function tests and basic chemistries.

Immobilization in a spica cast was the historical treatment but is no longer recommended for SCFE.

Once SCFE is identified in any patient with an open physis, management is surgical to avoid further slippage and the possible development of femoral head AVN.

When SCFE is identified in a patient with an open physis, surgical management with percutaneous in situ cannulated screw fixation should be undertaken on an urgent basis if the slip is stable or on an emergent basis if unstable.² There is a fair amount of evidence that the risk of AVN in unstable SCFE can be reduced if the hip is decompressed in some manner within 24 hours.⁵

Before surgery, the patient should remain strictly non-weight bearing on the affected leg to prevent conversion of a stable SCFE to an unstable SCFE.

In unstable SCFE, purposeful reduction of the displacement is controversial. Both open and closed reduction techniques have been associated with osteonecrosis, but the unstable slip itself may be the more likely cause of osteonecrosis.^{1, 13, 19}