American Association for Hand Surgery
Theme: Beyond Innovation

Back to 2019 Abstracts


A Biomechanical Analysis of Partial Extensor Tendon Lacerations >50% in Zone V: Is Surgical Intervention Necessary?
Deana Mercer, MD1; Darielys Mejias-Morales, BS2; Christina Salas, PhD2; Jasmin Regalado, MS2; Patrick Gilligan, MD2; Jeremiah Johnson, MD2; Lauren Long, BS2
1Department of Orthopaedic Surgery, University of New Mexico, Albuquerque, NM, 2University of New Mexico, Albuquerque, NM

Introduction: There is scare literature on the biomechanical consequences of partial extensor tendon lacerations. Much literature is available for flexor tendon lacerations, but the direct clinical application of these studies to the extensor tendons remains unclear and controversial. There are clinical studies that compare the effects of operative versus non-operative management, with the current guidelines supporting surgical repair when the laceration size is 50% of the width of the tendon or greater. The goal of this study is to quantify the effects of partial extensor tendon lacerations (50% or greater) on finger extension.
Materials & Methods: Forty fresh-frozen cadaver fingers were used (mean age 51). Specimens were dissected to expose the extensor digitorum tendons of the index, middle, and ring fingers. A "fight bite" was simulated at Zone V through a transverse cut of 50-74% (10 ring, 10 index) or 75-90% (10 middle, 10 index) of the width of each tendon. The specimens were fixed at the metacarpal to a custom loading device attached to an MTS servohydraulic load frame (Mini Bionix). Flexor tendons were pre-loaded using a 20 g weight. Fingers were cycled between full extension and full flexion for 3000 cycles. Following cyclic testing the tendon was displaced until failure. We report the mean reduction in force during cyclic testing and the mean failure load for each group.
Results: There was no significant loss in force during full extension/flexion cyclic loading for either group: 50-74% laceration group = 0.02 N (0.0045 lb-force; mean) and 75-90% laceration group = 0.05 N (0.01 lb-force; mean). During failure testing, the 50-74% group had 8/20 specimens that did not fail before the 100 mm actuator limit was reached. All others (12/20) failed at > 90 degrees of hyperextension at a mean load of 23.3 lb-force. The 75-90% group had 2/20 specimens that did not fail. All others (18/20) failed at a mean load of 16.1 lb-force at < 80 degrees of hyperextension.
Conclusions: Our study findings indicate that surgical repair may not be necessary for laceration to the extensor tendon in zone V involving up to 74% of the width of the tendon. In situations where the risk of infection is high, the tendon may not need to be repaired as placement of suture in a contaminated wound increases the chances of infection. With lacerations 75% or greater, or where extension lag is clinically present, surgical repair is recommended.


Back to 2019 Abstracts