Fracture of an osteochondroma of the femoral neck caused by impingement against the ischium.

This article describes 2 cases of osteochondroma emanating from the posterior aspect of the femoral neck with a fracture at the base of its stalk caused by impingement between the tumor and the ischium. A 44-year-old man and a 57-year-old man presented with left hip pain. Radiographs revealed a mass at the posterior aspect of the femoral neck. Computed tomography and magnetic resonance imaging revealed that the mass was fractured at the stalk. The relationship between the tumor and the ischium was examined with an image intensifier. The tumor impinged on the ischium with slight flexion and external rotation of the hip joint. In both patients, the tumor was excised, and the pathological report was osteochondroma. At follow-up, the patients had full hip joint range of motion, and lateral radiographs of the left hip joint showed complete resection of the tumor without recurrence. To the authors' knowledge, the current cases are the first reports of fracture of an osteochondroma with confirmed impingement using an image intensifier pre- and intraoperatively. Both patients had histories of restricted hip range of motion and a sudden onset of pain. After excision, the patients recovered to activities of daily living with no complications. An osteochondroma at the posterior aspect of the femoral neck can impinge on the ischium and fracture at its base with a sudden onset of pain. Awareness of this mechanism of impingement may lead to a better understanding of patient symptoms caused by osteochondroma of the femoral neck.