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

Abstract

Background: 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. Purpose: 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. Study Design: Cohort study; Level of evidence, 2. Methods: 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 t test was carried out to examine the differences between ACLR knees and control knees. Results: 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 (P < .001 and P = .043, respectively) and compared with the control group (P = .001 and P = .039, respectively). Greater patellar lateral tilt was observed at the ACL-deficient state compared with 3 years after ACLR (P = .003) and compared with the control group (P = .018). In the knee-flexed condition, greater anterior displacement was observed at the ACL-deficient state compared with 3 years after ACLR (P = .001) and compared with the control group (P = .011), and it was also observed at 6 months after ACLR compared with the control group (P = .019). Less lateral spin was observed at the ACL-deficient state (P = .042) and 6 months after ACLR (P = .004) compared with 3 years after ACLR and compared with the control group (P = .004 for both). No patellar alignment measures in the ACLR knees at 3 years were significantly different from those of the controls. Conclusion: 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.