An 11-Year-Old Boy With Thigh Pain and Worsening Limp

Radiology Quiz
Hone Your Interpretive Skills

An 11-year-old previously healthy boy presents with pain in his left thigh, which started 2 to 3 months ago. He is able to bear weight on the affected leg, but he walks with a progressively worsening limp. He denies any trauma to his leg. There is no history of fever or weight loss.

His weight is above the 95th percentile, and his height is at the 75th percentile. He is sitting on the examination table with his left leg externally rotated and in slight flexion at the hip. There is no point tenderness on palpation of his thigh. Pain is elicited in his left hip on internal rotation and extension of his leg at the hip. Results of knee examination are normal.

Plain radiographs showing anteroposterior views of the left hip in neutral (A) and frog-leg (B) positions lead to the diagnosis.

What is the cause of this boy’s thigh pain?

A. Osteomyelitis.

B. Acute transient synovitis.

C. Slipped capital femoral epiphysis.

D. Legg-Calvé-Perthes disease

(Answer and discussion on next page.)

ANSWER: C, slipped capital femoral epiphysis

The radiographs show widening of the proximal femoral growth plate. A line drawn along the superior edge of the femoral neck (the Klein line) normally crosses the epiphysis. In our patient’s radiograph, however, the epiphysis falls below this line (Figure).

Figure – A radiograph of our patient’s hip shows that the femoral epiphysis lies below the Klein line.

Slipped capital femoral epiphysis (SCFE) is the posterior and inferior slippage of the femoral epiphysis over the metaphysis at the level of the physeal plate. It represents a Salter-Harris type I fracture and is characterized by widening of the physeal growth plate. It presents in children between 8 and 15 years of age, coinciding with the growth spurt of puberty.

SCFE is one of the most commonly missed diagnoses in the pediatric age group. Early detection, prompt diagnosis, and timely treatment are critical to the prognosis. Avascular necrosis is a serious possible complication that can result from a delay in diagnosis of SCFE; it leads to early-onset degenerative arthritis requiring reconstructive surgery.

SCFE has a strong association with obesity, endocrine abnormalities (eg, hypothyroidism, panhypopituitarism, growth hormone treatment) and metabolic conditions such as renal osteodystrophy. Obesity places an abnormal stress on the oblique growth plate, and endocrine abnormalities and metabolic conditions lead to intrinsic weakness of the physis. Consequently, these conditions lead to physeal slippage during the growth spurt.

Clinically, children with SCFE present with a limp along with poorly localized hip, thigh, or knee pain. On examination, they have limited internal rotation and hold the leg in external rotation and slight flexion at the hip. SCFE is bilateral in 18% to 50% of patients. If the patient is ambulatory, the condition is classified as stable SCFE, which is associated with a better prognosis and a lower risk of avascular necrosis than unstable SCFE.

Plain radiographs are used to diagnose SCFE. However, a negative radiography result in a child with classic findings does not rule SCFE out. A computed tomography scan is indicated in such cases.

Once the diagnosis is established, the patient must be wheeled emergently to an orthopedic surgeon. The goal of treatment is to prevent further slippage. The standard treatment of SCFE is in situ fixation with a single screw. Most children who undergo single fixation for SCFE have a favorable prognosis. Athletic activities, including running and contact sports, may be resumed once the growth plate has fused.