Sudden-onset hip pain worsens overnight in a healthy child

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A normally active 6-year-old is stopped in his tracks by pain with no obvious cause.

Jason, 6 years old, was brought to the family practice clinic with onset of hip pain over the previous 24 hours. He had begun complaining about mild pain the night before. In the morning when he awoke, the pain was much worse, and he was unable to bear any weight on his left leg. His mother reported that up until very recently, he had been normally active, playing, running, and jumping on a trampoline. No specific trauma or injury was noted. He denied pain in any other joint.

PHYSICAL EXAMINATION

Jason was a well-developed male in mild distress secondary to pain. His temperature was 99.7ºF. No external swelling, deformity, or discoloration was obvious in the area of his left hip. However, he was extremely uncomfortable with any attempt to move the hip, and pain severely limited his range of motion. When asked to locate the point of maximum discomfort, he pointed at his proximal to mid thigh. There was no deformity, swelling, or pain with motion in the remainder of his leg.

Plain radiographs of the left hip were negative for any abnormalities. Laboratory evaluation revealed an erythrocyte sedimentation rate (ESR) of 45 mm/hr and a WBC count of 16,100/µL. Differential diagnoses under consideration included transient synovitis, inflammatory arthropathy, or septic hip or related infections.

The combination of Jason's clinical findings along with a temperature >99ºF and an ESR >20 pointed to an infectious etiology, such as septic arthritis or abscess formation. We ordered an MRI of his thigh, which revealed an 8-cm area of marrow edema in the femoral mid-shaft area consistent with an abscess (Figure 1).

ASPIRATING THE ABSCESS

Based on the above studies, the patient was taken to the operating room and underwent aspiration of the abscess in his left femur. When cultured, the aspirate grew out methicillin-resistant Staphylococcus aureus (MRSA) that was sensitive to clindamycin. Jason was placed on IV clindamycin and discharged home with a peripherally inserted central catheter (PICC) line for four weeks of therapy. Within several days, he was ambulating normally without pain and had full range of motion of his hip.

Our young patient's recovery was complicated by a PICC line infection with Enterobacter aerogenes that necessitated another hospital stay, removal of the line, and three additional weeks of therapy with trimethoprim/sulfamethoxazole and rifampin. The remainder of his recovery proceeded uneventfully. He returned to his normal active lifestyle without any functional limitations.

DISCUSSION

Most health-care providers are well aware of the emergence of community-acquired MRSA across the United States. The spectrum of infections ranges from common superficial infections of the skin and soft tissues to deeper infections, such as pneumonia and osteomyelitis.

Routes of infection include hematogenous spread from upper respiratory infections and direct spread from adjacent soft tissue and trauma. The source of Jason's infection was not identified, but given the absence of trauma, an upper respiratory infection seems the most likely culprit. This case emphasizes the importance of a heightened index of suspicion for deeper MRSA-related infections, even in previously healthy patients.

Following incision and drainage, treatment of the abscess and osteomyelitis is based on the results of culture and sensitivity testing, with vancomycin and clindamycin being the most effective antibiotics in patients with deep infections.

Trimethoprim/sulfamethoxazole, while effective for the treatment of skin and soft-tissue infections, is much less effective for deep infections.

Dr. McElhannon is assistant professor of family medicine at the Scott and White Hospital and Clinics, Texas A&M University System Health Science Center in Temple, Tex.

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