Review Question - QID 1399

Graft-screw divergence greater than 15-30 degrees from the trajectory of the femoral tunnel may lead to failure of fixation and early ACL failure.

Technical tips to avoid this complication include: inserting the screw and drill from the same portal (no divergence at all), hyperflexing the knee when inserting the screw if the femoral tunnel was drilled through the tibial tunnel, and using a guide wire to help gauge mismatch. Suspicion should be raised if there is difficulty inserting the screw. Intraoperative and postoperative radiographs can also help detect divergence.

Lemos et al. performed a bovine biomechanical study which noted that only 1/12 cows with parallel placed screws failed, while 4/12 with 15 degree divergent screws failed. They concluded that the pullout strength is highest when screws are placed with divergence 15 degrees or less.

Dworsky et al. reviewed 73 consecutive ACL reconstructions using interference screw fixation. They concluded that femoral screws with under 30 degrees of divergence did not lead to early clinical failure.

Incorrect Answers:
Answer 1: Risk of failure is eliminated by inserting the screw and the drill from the same tunnel.
Answer 4: Excessive graft-screw divergence more commonly occurs during femoral fixation.
Answer 5: Graft-screw divergence is a common cause of early failure in ACL reconstructions