Medial Meniscus Resection Increases and Medial Meniscus Repair Preserves Anterior Knee Laxity A Cohort Study of 4497 Patients With Primary Anterior Cruciate Ligament Reconstruction

Background: There are still controversies regarding the effects on knee laxity of additional meniscus resection or repair in the setting of anterior cruciate ligament reconstruction (ACLR). Hypothesis/Purpose: The purpose was to determine the effects on knee laxity of resection or repair of medial meniscus (MM) or lateral meniscus (LM) injuries in the ACLR knee. The hypothesis was that patients with an additional meniscus resection would have significantly increased postoperative knee laxity versus that of an isolated ACLR, whereas patients with meniscus repair would have laxity comparable to that of an isolated ACLR. Study Design: Cohort study; Level of evidence, 3. Methods: The KT-1000 arthrometer, with an anterior tibial load of 134 N, was used to evaluate knee laxity preoperatively and at 6-month postoperative follow-up for a total of 4497 patients with primary hamstring tendon ACLR. Patients with isolated ACLR or ACLR with additional MM resection, MM repair, LM resection, LM repair, or MM plus LM resection were compared, with the isolated ACLR group as a control. Results: All patients showed a significant reduction of knee laxity preoperatively (3.6 +/- 3.1 mm) to postoperatively (1.9 +/- 2.2 mm) (P < 0.0001). Patients who had an ACLR with either an MM resection (2.2 +/- 2.55 mm) or MM + LM resection (2.35 +/- 2.30 mm) showed significant increased postoperative knee laxity versus isolated ACLR (1.74 mm +/- 2.11 mm) (P < 0.05), whereas patients with MM repair (1.69 +/- 2.37 mm) did not show significantly different knee laxity when compared with the control group (P > 0.05). LM resection or repair did not significantly affect knee laxity. Significantly more surgical failures, defined as side-to-side difference >5 mm, were found in the ACLR + MM resection group and the ACLR + MM + LM resection group. Conclusion: In ACLR, additional MM resection increased whereas MM repair preserved knee laxity in comparison with the ACLR knee with intact menisci. Neither LM resection or LM repair showed a significant effect on knee laxity. Surgeons should make every effort to repair the meniscus whenever possible to avoid the residual postoperative laxity present in the meniscus-deficient knee.