Does physiologic posterolateral laxity influence clinical outcomes of anterior cruciate ligament reconstruction?

The purpose of this retrospective study was to evaluate the influence of physiologic posterolateral rotatory laxity on anterior cruciate ligament (ACL) reconstruction in terms of anterior knee stability and clinical outcomes.

We retrospectively studied 113 patients who had undergone ACL reconstruction between June 2004 and August 2008. Patients were categorized into three groups according to the degree of tibial external rotation at 90° of knee flexion: Group 1 (<40°), Group 2 (40° to 50°), and Group 3 (≥50°). Ligament stability was determined with use of the Lachman test, the pivot-shift test, and KT-2000 arthrometer testing. Function was assessed with use of the Lysholm score and the International Knee Documentation Committee (IKDC) score. Clinical outcomes were determined from data obtained before surgery and at the twenty-four-month follow-up visit.

We observed differences in postoperative knee translation between the groups (p < 0.001). A post hoc test showed increased mean knee translation in Group 3 compared with Groups 1 and 2. The degree of external rotation at 90° was positively correlated with anterior knee translation (r = 0.428; p = 0.007). However, there was an inverse correlation with the Lysholm knee scores (r = -0.146; p = 0.015) and IKDC scores (r = -0.205; p = 0.003).

The stability and functional scores after ACL reconstruction had a negative correlation with the degree of external rotation of the tibia at 90° (physiologic posterolateral rotatory laxity). After ACL reconstruction, patients with ≥ 50° of tibial external rotation had increased anterior translation and worse functional outcomes in comparison with those who had < 50° of tibial external rotation.