He reports the pain began as dull and deep in the right thigh, and that over the previous 2 days he began to have pain in the right knee and a limp on that side. He reports that he has been unable to participate in sports due to pain. Over-the-counter ibuprofen and acetaminophen have been minimally helpful. He has had no fever, nausea, vomiting, or trauma. He denies alcohol, drugs, or sexual activity. His past medical history is positive for mild hypertension noted on the previous year's well-child examination. On physical examination his height is 170 cm (5′7″), weight 100 kg (220 lb), and BMI 34.5 kg/m2. The right leg shows reduced internal rotation, reduced abduction, and reduced flexion. Upon flexion of the right hip the right thigh and leg rotate externally.
Which of the following is the most likely diagnosis?
A. Legg-Calvé-Perthes disease
B. Slipped capital femoral epiphysis
D. Septic arthritis of the hip
E. Transient synovitis
The correct answer is B.
Slipped capital femoral epiphysis is a disease of unknown etiology and occurs typically in adolescents; the disorder is most common among obese boys with delayed skeletal maturation or in thin, tall adolescents having recently enjoyed a growth spurt. The onset of this disorder is frequently gradual; pain referred to the knee in 20% of cases can mask the hip pathology.
Legg-Calvé-Perthes disease is avascular necrosis or idiopathic osteonecrosis of the femoral head; the cause of this disorder is unknown. Boys between the ages of 2 and 12 years are most frequently affected (incidence in boys is four- to fivefold greater than in girls), with a mean of 6-7 years old. Presenting symptoms include a limp and pain in the anterior thigh, groin, or knee, although classic symptoms include a painless limp.
Septic arthritis requires urgent intervention to preserve joint mobility. Joint aspiration is diagnostic and can be helpful in treatment. Opening the joint space may be required in a septic hip to assist in draining purulent material. These children need treatment for 4-6 weeks.
Transient synovitis is a disorder of unknown etiology, affecting children usually from 2 to 6 years of age. These children usually present with a painful limp. This is a diagnosis of exclusion; septic hip and osteomyelitis must be ruled out. The WBC count and ESR may be normal or slightly elevated. Early aspiration of the joint space may assist in diagnosis. Transient synovitis is a self-limited disorder.
Osteomyelitis usually presents with focal bone tenderness and fever. Early evaluation is best done through nuclear medicine studies, as plain film bony changes usually take a week or so before becoming evident.
(Hay et al, pp 783,788-792. Kliegman et al, pp 2360-2365, 2394-2400. McMillan et al, pp 2474-2476, 2497-2500. Rudolph et al, pp 854-856, 934-938.)