The Effect of Hamstring Contraction and Functional Brace Wear on the ACL Deficient Knee
Jeanne M. Schultheis, Dennis D. O’Connor, J. Richard Steadman, William I. Sterett, Scott Hormel, Robert A. Hintermeister
Introduction: Attempt to decrease the anterior tibial translation in ACL deficient patients may be done statically by a functional brace or dynamically via a hamstring contraction. The purpose of this study was to compare the effect of a functional brace, hamstring contraction, and their combination on the anterior tibial translation seen in the ACL deficient knee.
Methods: Nine ACL deficient subjects with a minimum of 6 mm side-to-side difference as measured on instrumented Lachman were studied. Anterior tibial translation of both the non-injured and ACL deficient knee initially were recorded at 90 and 180 Newtons of force. The ACL deficient knee was then tested with a functional ACL brace (CTi Edge, Innovation Sports), during a 50% of maximum hamstring contraction without a brace, and during a 50% of maximum hamstring contraction with a brace. Three trials were completed for each testing condition. The amount of flexion force supplied by the hamstrings was measured using a force transducer.
Results: Mean anterior translation without the brace was 11.9 mm and 16.9 mm at 90 and 180 Newtons, respectively. This decreased to 6.2 mm and 12.0 mm with the brace (p<0.05). During hamstring contraction, these decreased to 1.2 mm and 2.1 mm, a mean improvement of 89% (p<0.05). During a hamstring contraction while wearing the brace, mean anterior tibial translation was 2.3 mm and 3.3 mm, respectively (p<0.05).
Conclusions: Use of a functional brace did significantly decrease the amount of anterior tibial translation at 90 and 180 Newtons of force in the ACL deficient knee. Contraction of the hamstrings significantly reduced anterior tibial translation, as did the combination of hamstring contraction and functional bracing. The addition of a 50% hamstring contraction improved the efficacy of a functional brace in the ACL deficient knee.