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

Abstract

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.