Osteoid osteoma of the upper extremity. A diagnostic challenge.

Osteoid osteomas are benign tumors that may commonly mimic other entities in the upper extremity. The purpose of this study is to describe the clinical and imaging features of osteoid osteomas involving the upper extremity, highlight the difficulties in the diagnosis in the various areas and propose a diagnostic workup. Fourty-eight patients with histologically confirmed osteoid osteoma of the upper extremity treated at the authors' department from 1985 to 2000 were retrospectively reviewed. Data pertinent on the patients' history, lesion location, clinical and imaging characteristics as well as any unique features of individual patients were collected. There were 29 males and 19 females with a mean age of 28 years (range 20-42). The average duration of symptoms before definite diagnosis was 18 months (range 2-62). Pain was the presenting symptom in 46 of 48 patients, whereas swelling was the main complaint in 2 of the patients. Mean pre-operative visual analogue pain scale (VAS), was 8.8 ranging from 5.1 to 9.3. Eight lesions were located in the humerus, 4 in the ulna and 7 in the radius. In the carpal bones, 4 were located in the scaphoid, 4 in the capitate and 5 in the hamate. Seven lesions were located at the metacarpals and 9 lesions at the phalanges (5 proximal, no middle and 4 distal phalangeal lesions). Radiographs alone were sufficient to establish the diagnosis of osteoid osteoma in 32 cases. Bone scans identified a "hot spot" in 16 patients without previous radiographic evidence of a lesion and furthermore, computed tomography was performed in 32 patients to assist in the intraosseous localization of the lesion, and in the pre-operative planning. All patients underwent operative excision of the lesion and the diagnosis was confirmed by histology. Mean follow-up was 28 months (range 25-42). Fourty-three patients had an uneventful recovery. Mean post-operative VAS value was 1.8 ranging from 0 to 3. Osteoid osteoma of the upper extremity often mimics other etiologies and the complex anatomy of the upper extremity, as well as the tendency of patients to relate their symptoms to trauma are factors that easily lead to misdiagnosis or delay in the diagnosis. A high index of suspicion is essential and the diagnosis is based on an accurate clinical assessment and careful selection of imaging studies.