Peroneal tendon tears: 50% rule, a myth? Biomechanical cadaveric evaluation

Introduction: Peroneus brevis tendon tears are frequently diagnosed when ankle instability is present. No clear guideline exists as to when to repair or resect peroneal tendon tears. Our objective was to analyze the mechanical behavior of cadaveric peroneal tendons subjected to an artificially made damage, compromising 66% of its visible width and tested in a cyclic and failure phase. Methods: 8 cadaveric foot-ankle; distal tibia specimens were included in this study. A longitudinal full thickness tendon defect was created, 3 cm in length, centered behind the tip of the fibula, compromising 66% of the visible width of the peroneal tendons. All tendons were tested in a cyclic fashion using 100 repetitions between 50 N and 200 N, and then to failure. Statistical analysis was performed using the SPSS software. Results: No tendon failed during the cyclic testing. No defect lengthening was observed after the cyclic phase. On the failure phase, the mean load resisted by the peroneus brevis was 416 N, with a 95% confidence interval between 351 N and 481 N. The mean load resisted by the peroneus longus was 723 N, with a 95% confidence interval between 578 N and 868 N. Conclusions: A 33% of remaining peroneal tendon was able to resist very high tensile forces; therefore, it can be suggested that a 66% defect can be repaired and does not necessarily need a tenodesis as it has been historically recommended. The 50% rule, which determines when a peroneal tendon tear needs a tenodesis or repair, should be revisited.