Slipped upper femoral epiphysis (ECR 2014 Case of the Day)

Clinical History

A 5-year-old Caucasian girl presented with an 8-week-long history of pain in the left knee and upper leg, but no trauma. Her medical history included stem cell transplant for homozygous beta-thalassemia and growth-hormone treatment for short stature. Evaluation in a hospital during her recent holiday did not report any abnormalities.

Imaging Findings

Conventional standard anteroposterior (AP) view of the pelvis displayed small, flattened femoral epiphyses and widened hip joint space bilaterally. Posteromedial displacement of both epiphyses was suggested by a double density created by the epiphysis overlapping the medial metaphysis, the so-called "metaphyseal blanch sign of Steel". Additional frog-leg view confirmed the posteromedial displacement of both epiphyses. Based on the amount of relative displacement of the epiphysis on the metaphysis on the frog-leg view, the slipped capital femoral epiphysis (SCFE) was graded moderate on the right side and severe on the left side.
MRI examination performed in another hospital, 1 month before the presentation at our institution, depicted bilateral hip joint effusion, metaphyseal bone marrow oedema and posteromedially displaced femoral epiphyses.

Discussion

Slipped capital femoral epiphysis (SCFE) is defined as the posterior and inferior slippage of the proximal femoral epiphysis on the metaphysis (femoral neck), occurring through the growth plate. It occurs with a prevalence of 10 : 100, 000 at an average age of 13.5 years for boys and 12.0 years for girls. SCFE presents bilaterally in about 20 percent of patients. It is highly likely that in our case the bilateral pathology was the reason the diagnosis was initially missed.
The aetiology of SCFE is not fully understood and is thought to be multifactorial. It is more common in boys than girls and more common in Afro-Caribbeans than Caucasians. Risk factors include obesity, physeal orientation, growth spurt, abnormal physeal architecture, endocrine disorders, renal osteodystrophy and radiation therapy. Endocrine disorders that have been associated with SCFE include hypothyroidism, growth-hormone supplementation, hypogonadism, and panhypopituitarism.
SCFE should be considered in children who present with limping and poorly localized pain of the knee, groin or thigh. Hip pain is reported less frequently. Typically the child loses hip motion, including internal rotation, flexion and abduction. Because of this loss of motion, the child and the parents often describe a progressive external rotation and shortening of the lower extremity.
X-ray examination needs to include both AP and frog-leg views of both hips. Radiologic signs include:
- decreased epiphyseal height;
- widening of the growth plate compared with the uninvolved side;
- Steel sign: on AP radiography, a double density is found at the metaphysis (caused by the posterior lip of the epiphysis being superimposed on the metaphysis);
- Klein’s line: on AP radiography, a line drawn along the superior edge of the femoral neck should normally cross the epiphysis; the epiphysis will fall below this line in SCFE.
Several methods are commonly used to describe the radiographic magnitude of slip severity. The most straightforward involves the amount of relative displacement of the epiphysis on the metaphysis measured on a true lateral view of the affected hip. In a patient with a mildly SCFE, the amount of displacement is less than one third; in a patient with a moderately SCFE, the amount of displacement is from one third to one half, and in a patient with a severely SCFE, the amount of displacement is greater than one half.
Once a diagnosis is made, the child should immediately stop weight bearing, be placed on crutches or in a wheelchair, and referred to an orthopaedic surgeon.

Differential Diagnosis List

Final Diagnosis

Bilateral slipped capital femoral epiphysis

URL:	https://www.eurorad.org/case/11901
DOI:	10.1594/EURORAD/CASE.11901
ISSN:	1563-4086