Dynamic Evaluation of Pivot-Shift Phenomenon in Double-Bundle Anterior Cruciate Ligament Reconstruction Using Triaxial Accelerometer.

Abstract

To evaluate the effect of initial graft tension on rotational stability and to determine the minimum required tension (MRT) based on the pivot-shift phenomenon in isolated anteromedial bundle (AMB), isolated posteromedial bundle (PLB), and double-bundle anterior cruciate ligament (ACL) reconstructions using a triaxial accelerometer during surgery. Primary double-bundle ACL reconstructions were included. The pivot-shift test and N-test were performed before and during surgery with the acceleration measurements using a triaxial accelerometer. The pivot-shift test was also manually graded. The AMB and PLB were fixed to a graft tensioning system during surgery with the following settings: (1) AMB only (AMB), (2) PLB only (PLB), and (3) AMB and PLB (A+P). The total graft tension was first set at 20 N and then was increased in increments of 10 N until the pivot-shift test became negative, which was defined as the MRT in each setting. Twenty-five patients were evaluated. The MRT in the AMB setting averaged 26 N (range, 20 to 40 N); in the PLB setting, 28 N (range, 20 to 40 N); and in the A+P setting, 24 N (range, 20 to 40 N). The MRT in the A+P setting was significantly smaller than that in the PLB setting (P = .008). The acceleration in the A+P setting was significantly smaller than that in the AMB and PLB settings both in the pivot-shift test (vs AMB: P = .007, vs PLB: P = .011) and in the N-test (vs AMB: P < .001, vs PLB: P < .001). Double-bundle ACL reconstruction better controlled rotational stability with smaller MRT than isolated PLB reconstruction at the time of surgery. In double-bundle reconstruction, the MRT based on the pivot-shift phenomenon could be larger than previously reported MRT based on anteroposterior laxity. Level IV, therapeutic case series.