Lateral meniscus root tear in anterior cruciate ligament injured patients is not associated with increased rotatory knee laxity: A quantitative pivot shift analysis

Objectives

Biomechanical investigations conducted in vitro have elucidated the detrimental impact of lateral meniscus posterior root (LMPR) tears on knee contact pressures in the anterior cruciate ligament (ACL)-injured knee. Nevertheless, the influence of LMPR tears on the kinematics of ACL-injured patients remains ambiguous. The purpose of this study was to assess the impact of LMPR tears on anteroposterior and rotatory knee laxity employing a clinically validated quantitative pivot shift (QPS) analysis system.

Methods

Patients with ACL injury recruited in a prospective ACL registry spanning from 2012 to 2020 were retrospectively screened for eligibility. Criteria for inclusion encompassed complete primary ACL tears, absence of concurrent ligamentous or osseous injuries requiring operative treatment, and no prior knee surgeries.

Patients were assigned to two cohorts based on the presence (LMPR+) or absence (LMPR-) of an LMPR tear concomitant with ACL injury. Each patient underwent a standardized PS test, measurement of anterior tibial translation (ATT) (mm) using the Rolimeter, and QPS (mm) with a tablet-based image analysis system (PIVOT App). Comparative analyses of categorical variables were performed using the Fisher exact and Chi-square tests, while non-normally distributed continuous variables were compared between groups with the Mann–Whitney U test. Alfa was set at 0.05.

Results

A total of 99 patients were included in the study, of which 22 were assigned to the LMPR+ and 77 to the LMPR- group. Tear depth was considered partial in 13 (59%) patients and full in 9 (41%) patients. The prevalence of medial meniscus tears was greater in the LMPR+ (n ​= ​16, 73%) compared with the LMPR- (n ​= ​33, 43%) group (p ​= ​0.01). No difference was observed in ATT measured with the Rolimeter (p ​= ​0.63). Similarly, no difference was found in QPS between the LMPR+ (2.3 ​mm) and the LMPR- (1.9 ​mm) group (p ​= ​0.08).

Conclusion

Utilizing QPS in this investigation, LMPR tears do not significantly increase ATT or rotatory knee laxity. Consequently, although repairing LMRT associated with ACL injuries may be advisable for minimizing joint stress, their impact on controlling the PS in patients remains uncertain.

Level of evidence

III, retrospective comparative study.