Longitudinal rupture of the peroneal tendons.

To determine more precisely the injury mechanism of the peroneal tendon longitudinal tear, we studied 15 cadaveric lower extremities. Our study was motivated by our observation from a retrospective study of athletes treated by one surgeon (FHB) over a 17-year period. Eight patients who sustained lateral ankle sprains by plantar flexion and inversion of the foot on the leg also had longitudinal tears (1 to 3 cm) of the peroneal tendon--five in the peroneus longus and three in the peroneus brevis. All of the lateral ankle sprains were successfully managed nonoperatively. However, even after a period of rehabilitation, when their ankles should have been asymptomatic, the patients continued to complain of persistent lateral ankle swelling, popping, and retrofibular pain. On physical examination, all ankles were clinically stable. Palpable retrofibular popping occurred with active foot rotation. There was no evidence of peroneal tendon instability. Radiographs were normal and tenograms were suggestive of peroneal tendon injury but did not have the specificity to reveal the rupture. Primary suture repair of this peroneal tendon split was performed and gave excellent long-term results. The cadaveric studies revealed that the tear of the tendon could occur in the 25 degrees to 15 degrees range of plantar flexion as the peroneus longus impinged against the tip of the fibula and as the peroneus brevis impinged against the lateral wall of the peroneal groove or against the longus tendon.