© J. 3. Lippincott Co. Printed in U.S.A. Tibial Tunnel Placement in Anterior Cruciate Ligament Reconstructions and Graft Impingement

Fifty-six anterior cruciate ligament (ACL) reconstructions had a magnetic resonance scan of the ACL graft six months after operation. The impingement-free grafts (n = 26) had a low mag-netic resonance signal from origin to insertion. Impinged grafts (n = 30) had an increased mag-netic resonance signal confined to the distal two thirds of the graft. The location of the tibial tunnel (TT) was determined from a lateral roentgeno-gram. Positioning the center of the TT 12-23 mm from the anterior edge of the tibia consistently pro-duced graft impingement and flexion contractures. Roof impingement was avoided and hyperexten-sion was regained when the TT was centered more posteriorly within a 6-mm impingement-free zon