A Rare Case of Synostosis of a Pedunculated Osteochondroma with Its Native Bone: The ‘Mug Handle Sign’

Osteochondromas are one of the commonest benign bone neoplasms, and are typically asymptomatic and non-progressive. They can, however, cause several complications, the most important being malignant transformation into peripheral chondrosarcoma, particularly in patients with hereditary multiple exostoses. Other known complications include either osseous or cosmetic deformities, fracture, vascular compromise, neurologic sequelae from adjacent nerve compression, overlying adventitial bursa formation, pain and rarely pressure erosion of adjacent bones. Synostosis (fusion) of the distal portion of an osteochondroma to its native bone is a rare complication, not described in the existing literature. A case of osteochondroma fusion to the native bone is described in a 17-year-old patient, who was diagnosed with an osteochondroma of the right distal femur 4 years prior and now presented with pain and an enlarging mass in the region. Radiographs and MRI revealed a pedunculated osteochondroma, with its distal portion fused to the native femur, resulting in an unusual ‘mug handle’ like appearance. Due to the clinical symptoms, the osteochondroma was surgically excised. Pathology revealed no evidence of malignancy, and the patient made an uneventful recovery.