A NEW DEVICE AND METHOD FOR CONTROLLING THE LOAD IN RABBIT MEDIAL COLLATERAL LIGAMENT RECONSTRUCTIONS

In order to study the effect of intra-operative tensioning on the laxi ty and strength of healing ligament grafts in an animal model, a metho d of quantifying graft tension was needed. In this study a sensitive l igament tensioning device was developed to measure accurately the pref ixation loads in the rabbit medial collateral ligament (MCL) graft. To verify that reproducible changes in ligament tension could be created with the tensioning device a group of animals had their MCL grafts re placed at one of three different graft loads (tight, anatomic, or loos e). The tensioning device consists of two posts which move relative to one another by means of an axial screw. The movable post, which is in serted into the tibial bone island of the MCL graft has a series of st rain gauges which can measure the tension applied to the graft The sta tionary post attaches to the tibial shaft permitting the ligament graf t to be tensioned relative to this fixed point. After graft tensioning and fixation, the animals were euthanized immediately postoperatively and their ligament load-deformation behavior was measured using an In stron materials testing machine. Specific measures of low load behavio r was taken to quantify ligament laxity Our results demonstrate that t he tensioning device was capable of reproducibly altering prefixation graft lend intra-operatively as well as MCL laxity immediately postope ratively. A baseline of laxity values was thus developed to follow cha nges in this laxity measure for future studies of MCL graft healing in this model.