Summary

Greater rotational knee laxity is associated with failed meniscal repair after ACL reconstruction, highlighting the importance of addressing rotational stability to improve meniscal healing outcomes as demonstrated by second-look arthroscopy.

Abstract

Background

Meniscal injuries are common in patients undergoing anterior cruciate ligament (ACL) reconstruction, and successful meniscal repair is crucial for knee stability. However, the relationship between knee laxity and meniscal healing remains underexplored. This study aims to evaluate the healing of meniscal repairs performed concomitantly with ACL reconstruction using second-look arthroscopy, focusing on the association between meniscal healing and knee laxity, assessed quantitatively under anesthesia, with the objective of determining the impact of knee laxity on meniscal healing outcomes.

Methods

Patients who underwent primary ACL reconstruction between June 2016 and June 2021 were retrospectively included. Exclusion criteria were previous knee surgeries, additional ligament injuries, and missing quantitative measurement data. Second-look arthroscopy was performed at least one year postoperatively to assess meniscal healing, classifying outcomes into healed or failed groups. Knee laxity was measured under anesthesia preoperatively, intraoperatively, and at second-look using anterior tibial translation (ATT) and side-to-side ratios of tibial acceleration and external rotational angular velocity (ERAV). Statistical analysis was conducted using the Mann-Whitney U test, with significance set at P<.05.

Results

Out of 562 ACL reconstructions conducted, 113 knees involving 137 meniscal repairs were selected for analysis. During second-look arthroscopy, 114 menisci (83.2%) were classified as healed, while 23 menisci (16.8%) were identified as failed. Both groups showed significant intraoperative improvements in knee laxity measures: ATT improved from 6.0 mm to -1.0 mm (p<.001), while the side-to-side ratio of acceleration improved from 5.1 to 1.2 in the healed group and from 2.7 to 1.4 in the failed group (both p<.001). Similarly, ERAV improved from 3.6 to 1.3 in the healed group and from 3.6 to 1.6 in the failed group (both p<.001). Despite these improvements, there were no significant differences between the groups in ATT or patient-reported outcome measures (PROMs). However, at one year postoperatively, both acceleration and ERAV remained significantly higher in the failed group compared to the healed group (p<.001).

Discussion

The findings from this study highlight the significant association between rotational stability and successful meniscal healing following ACL reconstruction. The observed link between increased postoperative knee laxity, particularly in rotational movement, and lower meniscal healing rates underscores the importance of managing rotational instability during ACL reconstruction. This is especially pertinent in cases involving complex meniscal injuries, where residual laxity could potentially impact healing outcomes. The use of quantitative knee laxity measurements under anesthesia provided valuable insights into the relationship between knee stability and meniscal healing, offering a more informed approach to postoperative assessment. These findings suggest that improving rotational stability during surgery could enhance meniscal healing, leading to better overall outcomes for patients.

Conclusion

Greater postoperative rotational knee laxity is associated with a lower rate of meniscal healing after ACL reconstruction. This study emphasizes the importance of achieving optimal knee stability, particularly rotational stability, to improve meniscal healing outcomes. Quantitative evaluation of knee laxity under anesthesia may serve as a critical tool in predicting the success of meniscal repairs.