A prospectively randomized double-blind study on the effect of initial graft tension on knee stability after anterior cruciate ligament reconstruction.

Background: No consensus exists on the amount of tension that should be applied to anterior cruciate ligament grafts to best facilitate graft incorporation and re-create normal knee mechanics.

Hypothesis: Differences in initial graft tension will affect postoperative knee stability.

Study Design: Prospective, randomized, double-blind clinical trial.

Methods: Forty-nine patients undergoing bone-patellar tendon-bone autograft anterior cruciate ligament reconstruction by a single surgeon were randomized into high-tension (n = 27) and low-tension (n = 22) groups. Grafts were set at 90 N or 45 N. Arthrometric measurements (KT-1000 arthrometer manual maximum) of anterior tibial displacement and knee range of motion were made before surgery and at 1 week and an average of 20 months after surgery. Knee outcome scores were collected before and after surgery, and a single-leg hop test was also performed at final follow-up.

Results: After anterior cruciate ligament reconstruction, anterior tibial displacement was significantly greater in the patients in the low-tension group (P < .05). The side-to-side difference in anterior tibial displacement in the high-tension and low-tension groups was 1.1 +/- 1.7 mm versus 2.4 +/- 2.4 mm 1 week after surgery and 2.2 +/- 1.6 mm versus 3.0 +/- 2.2 mm at follow-up. Five patients had abnormal anterior tibial displacement (>5 mm side-to-side difference), and all were in the low-tension group (P <.05). Knee outcome scores improved with surgery (P <.01), with similar results for low-tension and high-tension groups. Hop test deficits were not different between groups.

Conclusions: Initial graft tension affects the restoration of knee stability. A graft tension of 45 N was not sufficient for restoring knee stability.