LAUSR

Summary Spontaneous attritional extensor tendon ruptures of the index finger due to carpal bone lesions are uncommon. Here, we report the case of a patient with a spontaneous rupture of the extensor indicis proprius (EIP) and index extensor digitorum communis (EDC2) tendons due to a previously symptomatic dorsal scaphoid osteophyte. A healthy 60-year-old man with right-hand dominance experienced mild pain over the dorsum of his left hand for no particular cause. He was a maker of tatami mats. Nine months later, he noted a sudden snap on the dorsum of his right hand while he was making tatami mats and he became unable to extend his index finger. Plain radiography revealed an osteophyte on the dorsal side of the scaphoid. Computed tomography revealed a bone fragment on the dorsal side between the scaphoid and lunate, which seemed to be derived from the scaphoid osteophyte. He underwent surgery 24 days after the incident. First, the fragment was excised; then tendon transfer was performed. EIP and EDC2 tendons were bundled using a side-to-side suture and connected to the middle extensor digitorum communis tendon using interlacing sutures. Histopathological findings of the resected bone were compatible with osteoarthritic change. Tatami mat making requires repeated radioulnar deviation, which could be a risk factor for scaphoid osteophytes. To our knowledge, the present case is the first to report extensor tendon rupture due to a scaphoid osteophyte in a healthy person. Although there is no consensus on the appropriate management of symptomatic scaphoid osteophytes, early intervention at the first sign of tenosynovitis might be necessary to prevent extensor tendon ruptures.