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Imaging in Slipped Capital Femoral Epiphysis

Practice Essentials

Slipped capital femoral epiphysis (SCFE) is the most common hip abnormality presenting in adolescence and is a primary cause of early osteoarthritis. SCFE occurs in 10.8 cases per 100,000 children and usually occurs in children 8 to 15 years of age.
 It is primarily associated with obesity and growth surges but occasionally can occur in patients with endocrine disorders such as hypothyroidism and hypogonadism.

Unfortunately, SCFE frequently is misdiagnosed, and it has symptoms that can be misleading.
Early treatment leads to better outcome but is confounded by frequent delays in diagnosis.
A study by Schur et al of 481 patients diagnosed with SCFE found that the average time from onset of symptoms to diagnosis was 17 weeks, with a range of zero to 169 weeks.
 The pathology is localized to the proximal aspect of the femur, but symptoms may occur in the knee or thigh, thereby leading to misdiagnosis.

(See the image below.)

Slipped capital femoral epiphysis. This child had

Slipped capital femoral epiphysis. This child had undergone radiation treatment for a pelvic malignancy. On this anteroposterior hip image, the pathologic slippage is not subtle.

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Classification and grade

SCFE is commonly classified in 2 ways: (1) as acute or chronic, or (2) as stable or unstable. The slip is classificed as acute if present for less than 3 weeks, as as chronic if present for more than 3 weeks. In the second classification, SCFE is considered stable if the patient can bear weight on the extremity without a crutch or walker; if unable to bear weight, the SCFE is considered unstable.

The Wilson or Southwick method can be used to measure the grade of severity of the slip in SCFE. In the Wilson method, a mild slip is epiphysis displacement that is less than one third the width of the metaphysis; a moderate slip, between one third and one half the width; and a severe slip, more than one half the width. The Southwick method uses the epiphyseal shaft angle on the frog-leg lateral radiograph, with the angle calculated by subtracting the epiphyseal shaft angle on the uninvolved side from that on the SCFE side. A mild slip is considered less than 30 degrees; moderate, between 30 and 50 degrees; and severe, more than 50 degrees.

Preferred examination

Radiographs are the easiest images to obtain and provide an excellent screening examination for hip pain in any patient. In patients with SCFE, advanced stages of the disease are easy to identify; however, subtle changes early in the course are more difficult to detect. Before the femoral epiphysis actually has become displaced, only a slight widening of the affected physis may be evident.

Diagnosis is made using anteroposterior (AP) pelvis and lateral frog-leg radiographs.
 MRI or CT may be able to detect SCFE in early cases. Computed tomography (CT) scanning is a sensitive method of measuring the degree of tilt and detecting early disease, but it is rarely needed. CT may be performed with low doses, and reconstructions may allow viewing of the relationship of the femoral head to the metaphysis in three planes. Magnetic resonance imaging (MRI) depicts the slippage earliest, and MRI can demonstrate early marrow edema and slippage. MRI may be helpful in follow-up studies of the contralateral hip.

A metaphyseal blanch is an increase in density in the proximal metaphysis. It is presumed that metaphyseal blanch represents an attempt at healing that occurs before there is visible displacement of the epiphysis.

For excellent patient education resources, visit eMedicineHealth’s First Aid and Injuries Center. Also, see eMedicineHealth’s patient education article Repetitive Motion Injuries.

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