Adductor insertion avulsion syndrome mimicking neoplastic processes in a 14-year-old long-distance runner.

Adductor insertion avulsion syndrome, also known as thigh splints, is an uncommon condition that can mimic primary bone tumors or osteomyelitis. This article describes the clinical and imaging findings of adductor insertion avulsion syndrome in a 14-year-old male long-distance runner. The patient presented with a 1-month history of progressively worsening pain in the medial aspect of the left thigh. No significant findings were noted on physical examination except slight tenderness to palpation. Radiographs revealed an intracortical radiolucent lesion with a solid periosteal reaction in the medial aspect of the femoral diaphysis. Bone scintigraphy showed an increased uptake corresponding with the lesion of the left medial femoral diaphysis. Computed tomography confirmed the presence of periosteal reaction and intracortical linear hypoattenuation and showed no fracture line. Magnetic resonance imaging revealed periosteal, cortical, and intramedullary signal intensity abnormalities. These clinical and radiologic features suggested adductor insertion avulsion syndrome. The patient was treated with initial avoidance of weight bearing using 2 crutches for ambulation, followed by progressive weight bearing over a period of 2 weeks. The symptom resolved completely 7 weeks after initial evaluation, and the patient had normal gait without pain. Knowledge of this condition is important for the appropriate interpretation of imaging findings and the avoidance of unnecessary biopsy with potentially misleading results. Moreover, this case provides a time line as a reference for the rehabilitation of patients in similar cases.