EFFECT OF TIBIAL ATTACHMENT LOCATION ON THE HEALING OF THE ANTERIOR CRUCIATE LIGAMENT FREEZE MODEL

We studied the healing response of a devitalized anterior cruciate lig ament to a treatment of initial anterior-posterior joint translation i n goats. Devitalization and devascularization were achieved by five su ccessive freeze-thaw cycles. Anterior-posterior translation was surgic ally altered by an osteotomy of the tibial attachment of the devitaliz ed ligament and its reattachment either in the anatomical position or in a position 5 mm posterior. Six weeks after the first surgery, the s ame procedure was performed on the contralateral limb, except that the ligament was reattached in the alternate position. Six months after t he initial surgery, femur-anterior cruciate ligament-tibia specimens w ere tested to determine their Structural and mechanical material prope rties. Anatomic ligament placement resulted in reduced anterior-poster ior translation (p < 0.05) and greater anterior joint stiffness (p < 0 .05). Maximum load (p < 0.05) and ligament stiffness (p < 0.01) also w ere greater for the anatomically placed anterior cruciate ligaments. T he maximum load for anatomically placed ligaments averaged 1,625 +/- 2 11 N (SEM). The strength of the posteriorly placed anterior cruciate l igament, 895 +/- 164 N, was similar to results of historical anterior cruciate autograft reconstructions. Ligament failure occurred near the tibial insertion in the posteriorly placed ligaments more often than in the anatomically placed ligaments (four of five times compared with one of five times). Ligament failure near the tibial insertion occurr ed with lower mean maximum load than failure at the midsubstance or by bone avulsion (796 compared with 1.592 N; p < 0.05). These data suppo rt the hypothesis that ligament laxity is important to the healing and remodeling of anterior cruciate ligament grafts.