Unrecognized closed mallet thumb injury complicating a closed proximal phalangeal fracture of the thumb

摘要

A 35-year-old man had his left thumb crushed between two wheelbarrows at work. Physical examination showed a dorsal skin abrasion and a painful deformity at the proximal phalanx level. Radiography showed a short oblique fracture of the proximal shaft of the proximal phalanx (Figure 1). Closed reduction and fixation using two crossed Kirschner wires failed owing to a persistent gap at the fracture site on fluoroscopy. In addition, the dorsal skin of the thumb showed an unusual depression while performing axial traction for fracture reduction (Figure 2). This indicated the loss of the cantilever effect of the extensor pollicis longus (EPL) tendon and raised the suspicion of an associated tendon rupture. Therefore, we decided to proceed to surgical exploration. The EPL tendon'was found to be ruptured near its insertion, and its proximal end was found to be entrapped at the fracture site (Figure 3, left). After releasing the proximal stump of the EPL tendon, the fracture was reduced and fixed using two crossed Kirschner wires. The tendon was repaired without difficulty with the interphalangeal joint fixed in extension using temporary Kirschner wires (Figure 3, right).