Chronic Injury of Sagittal Band by Metacarpal Head Osteoma: A Case Report

Injury of the sagittal band, a crucial component of the extensor hood, can occur in various situations, including spontaneous events, trauma, and rheumatic diseases. This case presents a rupture of the sagittal band resulting from chronic irritation caused by a metacarpal head osteoma. A 22-year-old female presented with ulnar subluxation of the extensor tendon at the left third metacarpophalangeal joint, without any history of trauma or pain. Ultrasonography and computed tomography revealed a 1.7 mm-sized bony lesion on the radial side of the metacarpal head, accompanied by a partial tear of the radial sagittal band. Our hypothesis that chronic irritation of the sagittal band by the adjacent bony lesion led to the partial tear was confirmed by intraoperative findings. The lesion was excised, and the radial sagittal band was reconstructed. Histopathological examination confirmed a diagnosis of osteoma. To our knowledge, this is the first reported case of sagittal band rupture caused by an osteoma of the metacarpal head. This case underscores the importance of considering an underlying metacarpal head osteoma in patients with non-rheumatoid joints presenting, in the absence of a traumatic history, with a sagittal band rupture due to chronic irritation.