The Effects of Graft Rotation on Attachment Site Separation Distances in Anterior Cruciate Ligament Reconstruction

Abstract

We created a model to see if twisting the graft in an anterior cruciate ligament reconstruction affected the distance separating the femoral and tibial attachments of the perimeter fibers of a patellar tendon graft. Graft bone plugs were simulated by two 12.5-mm diameter Delrin cylinders. Holes, 1 mm in diameter, were placed at the four corners of a centralized rectangle measuring 5 by 10 mm. Graft ligament fibers were represented by color-coded sutures passed through the holes in the modeled bone plugs. This graft model was fixed in tun nels reamed under arthroscopic guidance at the ante rior cruciate ligament attachment sites of the femur and tibia in six fresh-frozen knee specimens. Spring gauges were used to measure indirectly the changes in distance of separation during knee flexion between the femoral and tibial attachments relative to a zero defined at 90° of knee flexion. The tibial cylinder was rotated at 45° increments from 90° external to 180° internal rotation relative to the femoral cylinder and measurements were repeated after each incremental rotation. External ro tation resulted in a statistically significant higher mean separation distance (4.5 mm) for peripheral graft attach ments than internal rotation (2.8 mm) (P = 0.05).