The Effect of Postoperative KT-1000 Arthrometer Score on Long-Term Outcome After Anterior Cruciate Ligament Reconstruction

Background: Many long-term studies have looked at outcomes after anterior cruciate ligament reconstruction (ACLR), but none have correlated long-term outcomes with postoperative laxity greater than 5 mm. It has been stated previously that more than 5 mm of postoperative graft laxity constituted a procedural failure. Purpose: To directly compare tight grafts (<3 mm) and loose grafts (>5 mm) to determine the effect of graft laxity, as measured by KT-1000 arthrometer, after ACLR on long-term clinical outcomes. Study Design: Cohort study; Level of evidence, 2. Methods: The study included 171 consecutive patients who had undergone transtibial bone-patellar tendon-bone ACLR between 1992 and 1998. At 6, 12, and 24 months postoperatively (the immediate postoperative period), patients were evaluated. Group A included patients with a maximal side-to-side (STS) difference in the immediate postoperative period of less than 3 mm (tight grafts), and group B included patients with a maximal STS difference of greater than 5 mm (loose grafts). Any patient with a history of ipsilateral or contralateral ACLR or ACL injury, meniscectomy, or cartilage restoration was excluded. Patients were prospectively followed to long-term follow-up, when a telephone interview was conducted regarding knee function and to document Lysholm, Tegner, Knee injury and Osteoarthritis Outcome Score (KOOS), and International Knee Documentation Committee (IKDC) subjective outcome scores. Results: Eighty-seven patients met inclusion criteria: 66 tight grafts (group A) and 21 loose grafts (group B). The mean SD time to follow-up was 16.3 +/- 1.5 years in group A (n = 46) and 16.8 +/- 1.3 years in group B (n = 15). Tegner (P = .77), Lysholm (P = .85), KOOS (P = .96), and IKDC (P = .42) were found to have no statistically significant difference between groups at long-term follow-up. Both Tegner and Lysholm scores significantly improved in tight and loose grafts in the immediate postoperative period as well as at long-term follow-up compared with preoperatively. There were 2 ACL revisions in group A and none in group B. Eleven of 46 patients (24%) in group A required subsequent procedures versus 1 of 15 patients (6.7%) in group B (P = .146). Conclusion: Postoperative laxity of greater than 5 mm STS difference as measured by KT-1000 arthrometer does not appear to place patients at a worse clinical outcome at long-term follow-up, nor does it lead to significantly more subsequent procedures. In addition, transtibial ACLR can provide excellent clinical results at long-term follow-up.