Biomechanics Lab - Clinical Studies

Robert J. Johnson, M.D., Bruce D. Beynnon, Ph.D., Benjamin S. Uh, M.D., Braden C. Fleming, Ph.D., Glenn D. Peura, M.S., Claude E. Nichols, M.D., Per A. Renstrom, M.D., Ph.D.

Department of Orthopaedics & Rehabilitation, McClure Musculoskeletal Research Center, University of Vermont, Burlington, Vermont

Many factors have been associated with destruction of knee articular cartilage (i.e., epidemiological, biochemical, and morphological); however, only trauma such as that associated with disruption of the anterior cruciate ligament (ACL) is known to cause osteoarthritis. Another important clinical concern associated with ACL disruption is that it is functionally disabling to an active individual and may lead to repetitive joint trauma. Reconstruction of the ACL can restore normal knee biomechanics (at least at the time of surgery) and reduce repetitive joint trauma; however, the effect of rehabilitation on the knee during ACL graft healing is unclear. Many authors caution that the increase of anterior-posterior translation of the tibia relative to the femur (anterior-posterior knee laxity) that occurs during rehabilitation is deleterious from a biomechanical standpoint, leading to abnormal articular tibiofemoral contact stress distributions, and may be associated with an increase in the incidence of post-traumatic osteoarthritis. There is universal agreement that postoperative rehabilitation is important following ACL reconstruction; however, there is no consensus on what the ideal program entails. The primary objective of this prospective, randomized, double-blinded, controlled trial is to determine the effect of an aggressive versus a non-aggressive rehabilitation program following ACL reconstruction via biomechanical and biochemical analyses. The secondary objective is to determine the relationship between the increase in the anterior-posterior knee laxity and the concentrations of the biochemical markers of articular cartilage matrix synthesis and degradation. The two rehabilitation programs were compared by measuring the increase in anterior-posterior knee laxity and the increase in concentrations of the markers of articular cartilage matrix metabolism at 6, 12, and 24 months postoperatively and correlating these two outcomes. Our long-term goal is to identify those biochemical markers which are highly predictive of changes consistent with the radiographic signs of osteoarthritis.

At the present time we have followed 21 patients to 2 years (9 with aggressive and 12 with non-aggressive rehabilitation). The side to side KT-1000 differences between the ACL disrupted and the patients normal knee were not statistically different immediately before and immediately following the ACL reconstruction for the aggressive and non-aggressive rehabilitation groups. At the two year follow-up there was a strong trend for greater laxity in the aggressive rehabilitation group (3.2 mm side to side difference) compared to the non-aggressive group (1.6 mm side to side difference).

Presented at ACL Study Group, Rhodes Greece, May 2000

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