METHOD TO ASSESS IN-VIVO KNEE STABILITY LONGITUDINALLY IN AN ANIMAL-MODEL OF LIGAMENT INJURY

The purpose of this study was to develop a method to prospectively qua ntify passive knee stability in an animal model of joint injury over t ime. Knee stability is defined here as the amount of translation or ro tation of the tibia relative to the femur for a given application of f orce or moment, respectively. Five animals that had undergone transect ion of the anterior cruciate ligament and three control animals that h ad undergone a sham operation were anaesthetized and positioned in a s tereotaxic frame. Motion of the tibia relative to the femur was quanti fied with use of reflective markers secured to modified bone pins and a three-dimensional motion analysis system. External forces and moment s in the transverse plane of the tibia were measured with use of force transducers based on a strain-gauge design. Longitudinal measurements of knee stability were made before either sham surgery (control anima ls) or transection of the ligament (experimental animals), immediately after surgery, and at 2 and 4 months after transection. The results s howed that the animals tolerated the procedures well and that systemat ic measurements could be obtained. The method described here has the p ractical advantage over cross-sectional experimental designs in that t he number of subjects can be decreased while maintaining statistical p ower and has the further conceptual advantage that individual changes can be accounted for over time.