Abstract
Dear Sir,
We report a rare case of an osteoid osteoma inside the styloid process of the third metacarpal bone of a 16 year-old man who presented with a painful swelling of his right hand. A bony prominence seen on a standard lateral X-ray was further evaluated by CT scanning to show a 4-mm hypodensity inside an osteoarthritic spur over the middle (third) carpometacarpal joint. The suggested diagnosis was of an osteoid osteoma inside a metacarpal boss (Fig 1). It was decided to treat the painful spur as a metacarpal boss, although the clinical presentation was more typical of osteoid osteoma, and a surgical wedge excision of the metacarpal boss, including part of the dorsal head of the capitate bone, was performed. Histological examination revealed trabecular bone tissue with osteoblastic activity and highly vascularised connective tissue, confirming the two radiological diagnoses. The patient was free of pain and had normal active wrist motion 2 months postoperatively.
We have found only five reported presentations of osteoid osteoma in metacarpal bones (Ambrosia et al., 1987; Bednar et al., 1993; Uda et al., 2002; Wachtl et al., 1995). All were removed surgically with or without grafting or arthrodesis. Osteoid osteoma is commonly treated conservatively with salicylates. The indication for surgery depends on its size and location. Currently, percutaneous CT-guided ablation is advocated for osteoid osteomas surrounded by sufficient bone stock.
Although the reported results of a surgical excision of a metacarpal boss are not always good, we still feel that an adequately planned wedge excision that includes the limits of the involved carpometacarpal joint gives satisfactory relief of symptoms. In our patient, the typical symptoms of an osteoid osteoma were combined with a bony prominence at the typical location of a metacarpal boss. As such, the lesion was considered an atypical presentation of a metacarpal boss. CT-scan assessment is advocated for diagnosis of this condition and for surgical planning of the wedge excision.