The pivot-shift test is used to assess for rotatory knee laxity in the anterior cruciate ligament (ACL)-deficient knee and ACL-reconstructed knee; however, the pivot shift uses a subjective grading system that is limited by variability between examiners. Consequently, quantified pivot shift (QPS) test software (PIVOT iPad application) has been developed and validated to measure the magnitude of rotatory knee laxity during the positive pivot-shift test.
To employ intraoperative QPS (iQPS) to assess for differences in residual rotatory knee laxity after ACL reconstruction (ACLR) versus ACLR augmented with lateral extra-articular tenodesis (ACLR + LET), and to employ iQPS to determine if ACLR and/or ACLR + LET result in overconstrained knee kinematics when compared with the contralateral knee.
Cohort study; Level of evidence, 2.
iQPS was performed in 20 patients by a single surgeon on both the operative and contralateral knees before ACLR. ACLR was augmented with a LET if the lateral compartment tibial translation measured during QPS was greater than or equal to double the amount of lateral tibial compartment translation measured for the contralateral knee. After each reconstruction (ACLR or ACLR + LET), iQPS measurements were performed. iQPS data were compared with the preoperative QPS measurements of the operative and contralateral knees. Postoperative iQPS data were compared with both the preoperative QPS measurements of the operative and contralateral knees with paired samples t tests. Categorical variables were compared using the Fisher exact test.
The mean age in the cohort was 17.3 years (range, 15-24 years). There were no significant differences between the groups in terms of the proportion of male patients (ACLR: 5 male, 5 female vs ACLR + LET: 4 male, 6 female) or age (ACLR: 17.7 ± 3.3 years; 95% CI, 15.4-24.0 vs ACLR + LET: 16.8 ± 2.8 years, 95% CI, 14.8-22.0; P = .999). There were no significant differences between the groups with respect to preoperative QPS performed during examination under anesthesia (ACLR: 4.7 ± 2.0 mm; 95% CI, 3.3-6.1 vs ACLR + LET: 3.6 ± 1.8 mm; 95% CI, 2.3-4.9; P = .2). Both ACLR and ACLR + LET resulted in significant decreases in rotatory knee laxity when compared with preoperative QPS measurements (ACLR: –3.4 ± 1.7 mm; 95% CI, −4.6 to −2.2; P < .001: ACLR + LET: –2.6 ± 1.9 mm; 95% CI, −3.9 to −1.3; P < .002). Moreover, when compared with isolated ACLR, ACLR + LET did not result in a significantly smaller magnitude of change in iQPS between the pre- and postoperative states ( P = .3).
Both ACLR and ACLR + LET resulted in significant decreases in rotatory knee laxity. The augmentation of ACLR with LET did not change the constraint of the knee with respect to lateral compartment translation as measured during iQPS.