EVALUATION OF KNEE-JOINT LAXITY AND THE STRUCTURAL-PROPERTIES OF THE ANTERIOR CRUCIATE LIGAMENT GRAFT IN THE HUMAN - A CASE-REPORT

Much of what is known about the healing response of ACL grafts has bee n learned through investigations performed with various animal models, (5,14) and little is known about the biomechanical behavior of the ACL graft during healing in humans. Investigations of the iliotibial trac t autograft for periods of up to 1 year in animal models have demonstr ated that the ultimate failure load values range between 23% and 40% o f the control ACLs, while the stiffness was 45% of the normal ACL a ye ar or more after the reconstructions. Studies of the patellar tendon a utograft in animals have shown that the ultimate failure load values r ange between 11% and 57% of the control ACLs, while the stiffnesses ha ve been reported to range between 13% and 57% of the healthy ACLs a ye ar or more after the reconstructions.(2,4-8,11-1315,17,19) In addition to having adequate structural properties (including ultimate failure strength and linear stiffness), an ACL graft must also control anterio r displacement of the tibia relative to the femur (i.e., anterior laxi ty). A review of investigations of healing ACL grafts performed in ani mals indicates that anteroposterior (AP) knee laxity initially increas es and becomes much greater than normal after surgery.(11) Anteroposte rior laxity then decreases during healing, never returning to the norm al value during the later stages of healing.(11) After reconstruction of the ACL with the patellar tendon autograft, AP knee laxity has been reported to range between 156% and 269% of the contralateral healthy knee a year or longer after reconstruction.(2,11) The previous studies of healing ACL grafts that have been performed in animals have provid ed the clinical community with insight into the biological remodeling response of the graft, as well as the biomechanical behavior of the gr aft during healing. However, application of these results to clinical practice must be done carefully. Animals have an uncontrolled postoper ative rehabilitative regimen, and the similarity of animal knee models in comparison with that of the human must be carefully considered. Th e objective of this investigation was to evaluate the biomechanical be havior of a matched pair of human knees. One knee was uninjured, and t he other underwent ACL reconstruction with a bone-patellar tendon-bone autograft and 8 months of healing.