Abstract
Terminal extensor tendon rupture of the finger results in mallet finger deformity. Although conservative therapy is the primary treatment for tendinous mallets, surgical treatment, such as tendon grafting or tendon transfer, is considered if there is a tendon defect. The external oblique muscle aponeurosis is sheet-like in structure, similar in morphology to the extensor tendons, and can be harvested with perifascial areolar tissue. In the present study, we used the external oblique muscle aponeurosis, including perifascial areolar tissue, as a transplanted tendon for finger zone I extensor tendon rupture with tendon defect. A 23-year-old man cut the extensor tendon of his left middle finger. Although primary tendon suture was attempted, it failed and caused a 20-mm defect after re-suturing several times. Two weeks later, a tendon reconstruction was performed. The external oblique muscle aponeurosis, including the perifascial areolar tissue, was harvested. It was folded in two and sutured between the proximal and distal ends of the extensor tendon. Perifascial areolar tissue was applied to cover the entire circumferential area of the transferred aponeurosis, including the suture area. At 3 months postoperatively, when all rehabilitation was over, the left middle finger distal inter phalangeal joint total active motion was 60° with a 5° angle of insufficient extension. This corresponds to the excellent functional evaluation of the mallet finger reported by Kanie et al. External oblique muscle aponeurosis with perifascial areolar tissue is considered useful for grafting of terminal extensor tendon ruptures. Further case series are warranted.

(a) The harvested aponeurosis was then folded in two and sutured between the proximal and distal tears. (b) Schematic illustration: perifascial areolar tissue was used to cover the entire circumferential area over the tendon membrane, including the suture. (c, d) Wound is closed. The extensor tendon was reconstructed at tension of 0° distal inter phalangeal extension.
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