Plain films show the most common hip problem of adolescence

CASE

The patient is a 13-year-old boy with pain in the left thigh and no history of trauma. His symptoms started about 2 months ago and have gradually worsened. The boy's mother reports that over the past 2 weeks, he has started to limp. Physical examination of the left knee produces normal results, but examination of the left hip with the patient supine reveals increased external rotation and decreased range of motion with internal rotation, flexion, and abduction compared to the right side. Hip radiographs are obtained (see Figure 1). What do the radiographs show?

The films reveal a normal-appearing right hip, but on the left, there is a step-off deformity at the level of the epiphyseal plate inferiorly and there is minimal widening of the epiphyseal plate (growth plate). The findings are compatible with a slipped capital femoral epiphysis (SCFE, sometimes pronounced as “skiffy”). This patient had a subtle and mild example; more pronounced misalignment between the femoral neck and the femoral head epiphysis occurs in some patients.

DISCUSSION

Drawing what is called a Klein line on the anteroposterior view may be helpful when evaluating the radiograph.
This line is drawn along the superior margin of the femoral neck and should pass through a portion of the femoral head epiphysis. If it does not, the patient has SCFE and immediate orthopedic consultation is necessary. Upon diagnosis, the patient should be instructed not to bear weight on the affected side so that further slippage is avoided.

SCFE is the most common hip problem of adolescence. It is a slippage of the femoral head epiphysis posteriorly
and inferiorly with respect to the femoral neck and usually occurs during periods of accelerated growth (growth spurts). Most cases are idiopathic, but the condition has been associated with delayed bone age, hypogonadism, growth hormone deficiency, hypothyroidism, previous radiation therapy, use of medications (such as steroids or chemotherapy), and renal osteodystrophy. SCFE also has a predilection for African-Americans and for obese patients, although it may occur in any child. Boys are affected about twice as often as girls, and SCFE usually occurs between the ages of 10 and 16 years, although it is rare in females after menses have begun. If unilateral SCFE is encountered, the chances are good that the contralateral hip will be affected. Therefore, obtaining radiographs of the other hip is advised, and parents should be told that if similar symptoms occur on the other side, further evaluation is required.

Patients with SCFE can present with pain in the thigh, hip, groin, or knee. The pain is usually exacerbated
with activity and relieved with rest. The patient may have a limp or antalgic gait. External rotation of the affected leg may also be present. Physical examination may show increased external rotation of the involved hip and possibly decreased internal rotation, abduction, and flexion.

SCFE should be considered in any child who presents with hip, thigh, or knee pain because serious long-term and disabling effects can result from lack of treatment. A thorough physical examination, from hip to knee, is necessary. The patient may present with knee pain even when the hip is the culprit, as the pain may be referred along the obturator nerve. Other diagnoses to consider when evaluating a child with hip or leg pain include Legg-Calvé-Perthes disease, synovitis, septic joint, fracture, chronic developmental hip dysplasia, and femoral hernia.

For diagnosis, radiographs of the hips are useful and may demonstrate widening of the epiphyseal plate, an abnormal Klein line, and misalignment between the femoral head epiphysis and the femoral neck. The amount of slippage is classified radiographically as type I (mild), less than 33% displacement of the femoral head compared to the femoral neck; type II (moderate), between 33% and 50% displacement; and type III (severe), greater than 50% displacement. If symptoms have been present for less than 3 weeks, the condition is considered acute; if they have been present for 3 weeks or longer, the SCFE is considered chroni c. If the patient has had chronic symptoms but presents with an acute exacerbation, the condition is termed acute-on-chronic. Usually no laboratory studies are needed unless the presentation is unusual, such as bilateral SCFE occurring in a patient younger than 10 years. In such a case, evaluation for panhypopituitarism, renal osteodystrophy, hypothyroidism, hypogonadism, and growth hormone abnormality may be necessary. After diagnosis and immediate referral, there is usually no delay in treatment.

Treatment usually consists of pin fixation with a single screw, particularly if displacement is mild (see Figure 2). The prognosis in this case is very good. If displacement is moderate or severe, the orthopedist may try to gently reduce the slippage during surgery before pinning. Uncommon and less effective treatment options include bone graft epiphysiodesis with internal fixation or casting, intracapsular osteotomy, or placement of a spica cast.

The most common complications associated with SCFE are avascular necrosis of the femoral head and chondrolysis. Other complications include premature osteoarthritis, chronic disability, leg length discrepancy, and possibly the need for hip fusion or arthroplasty. After treatment, follow-up radiographs are obtained regularly until closure of the epiphyseal plate is documented. JAAPA

The author practices in a radiology group at North Oaks health System, Hammond, La. She has indicated no relationships to disclose relating to the content o this article.