Longitudinal Changes of Patellar Alignment Before and After Anterior Cruciate Ligament Reconstruction With Hamstring Autograft.

Abstract

Evidence has suggested that after anterior cruciate ligament (ACL) reconstruction (ACLR), individuals exhibit patellar malalignment; however, it is unknown if patellar alignment changes over time. To examine the longitudinal changes in patellar alignment before, 6 months after, and 3 years after ACLR and to compare these variations, if present, with patellar alignment in controls. Cohort study; Level of evidence, 2. A total of 35 patients who had ACLR using hamstring autograft (19 male; age, 29.9 ± 7.7 years; body mass index, 23.8 ± 2.5) and 20 controls (13 male; age, 30.4 ± 4.8 years; body mass index, 24.3 ± 2.7) participated. All patients underwent bilateral knee magnetic resonance imaging with the knee in extension and 30° of flexion using sagittal T2-weighted, fat-saturated fast spin-echo images to assess patellar alignment in 6 degrees of freedom: anterior-posterior, medial-lateral, and superior-inferior translations; flexion; tilt; and spin. Patients who had ACLR were assessed before (ACL-deficient state) and 6 months and 3 years after ACLR, while control participants were only assessed once. One-way repeated-measures analysis of variance was used to examine patellar alignment across time in the ACLR group. If changes were present, the independent <i>t</i> test was carried out to examine the differences between ACLR knees and control knees. In the knee-extended condition, greater patellar lateral displacement was observed at the ACL-deficient state and 6 months after ACLR compared with 3 years after ACLR within the ACLR group (<i>P</i> < .001 and <i>P</i> = .043, respectively) and compared with the control group (<i>P</i> = .001 and <i>P</i> = .039, respectively). Greater patellar lateral tilt was observed at the ACL-deficient state compared with 3 years after ACLR (<i>P</i> = .003) and compared with the control group (<i>P</i> = .018). In the knee-flexed condition, greater anterior displacement was observed at the ACL-deficient state compared with 3 years after ACLR (<i>P</i> = .001) and compared with the control group (<i>P</i> = .011), and it was also observed at 6 months after ACLR compared with the control group (<i>P</i> = .019). Less lateral spin was observed at the ACL-deficient state (<i>P</i> = .042) and 6 months after ACLR (<i>P</i> = .004) compared with 3 years after ACLR and compared with the control group (<i>P</i> = .004 for both). No patellar alignment measures in the ACLR knees at 3 years were significantly different from those of the controls. Patellar malalignment in individuals before and after ACLR subjected to longitudinal changes, and the differences in alignment between ACLR and controls diminished over 3 years.