Patellar Malalignment Is Associated With Patellofemoral Lesions and Cartilage Relaxation Times After Hamstring Autograft Anterior Cruciate Ligament Reconstruction

Abstract

Background: There is growing evidence suggesting a link between patellofemoral joint (PFJ) osteoarthritis in anterior cruciate ligament (ACL)–reconstructed knees and altered joint alignment. Purpose: To determine whether patellar alignment differs between participants with and without ACL reconstruction (ACLR) and to identify possible associations between patellar alignment and PFJ osteoarthritis features over 3 years. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 37 participants with ACLR (sex, 23 male; mean ± SD age, 28.1 ± 7.4 years) and 20 healthy controls (13 male; 30.4 ± 4.8 years) participated. Patients underwent magnetic resonance imaging: (1) sagittal T2-weighted fat-saturated fast spin echo images to calculate patellar alignment, (2) sagittal 3-dimensional intermediate-weighted fast spin echo Cube sequence for clinical morphological grading (modified Whole-Organ Magnetic Resonance Imaging Score [WORMS]), and (3) sagittal combined T1ρ/T2 mapping sequence for performing voxel-based relaxometry. Patellar alignment of the ACLR knees were assessed at 6 months (baseline). One-way analysis of variance was used to compare patellar alignment among the ACLR (at 6 months), contralateral, and control knees. Within the ACLR group, a logistic regression model was used to identify if patellar alignment measures at baseline were risk factors for worsening of PFJ structural changes over 3 years. Statistical parametric mapping was used to evaluate the longitudinal associations between patellar alignment and cartilage relaxation times at 3 years. Results: When compared with control knees, ACLR knees exhibited a laterally and anteriorly displaced patella ( P = .045 and P = .041), less flexion ( P = .031), and less lateral spin ( P = .012). Furthermore, excessive lateral displacement was a significant predictor of worsening of WORMS ( P = .050). Lateral displacement was positively correlated with increased T1ρ and T2 in the patellar and trochlear cartilage at 3 years. Patellar lateral spin revealed similar negative findings. Conclusion: Participants with ACLR exhibited a laterally and anteriorly displaced patella, less flexion, and less lateral spin when compared with healthy controls. Excessive patellar lateral displacement was the strongest predictor to the development of PFJ osteoarthritis features longitudinally.

Patient-Reported Outcomes and Knee Mechanics Correlate With Patellofemoral Deep Cartilage UTE-T2* 2 Years After Anterior Cruciate Ligament Reconstruction

“…5 Although Capin et al 5 found associations between slower walking speed at 3 months after ACLR and higher trochlear cartilage T2 values at 6 months, the absence of T2 associations with other gait metrics in that work likely reflects that gait was assessed just 3 months after surgery when new loading patterns may not have been fully established. Other works compared static, unloaded patellar alignment 32 or tibial rotation 31 (derived from MRI scans) with patellofemoral cartilage T2 and T1ρ times. Liao et al 32 found that excessive patellar lateral displacement 6 months after reconstruction was associated with elevated lateral patellofemoral compartment T1ρ and T2 values 3 years later.…”

“…Other works compared static, unloaded patellar alignment 32 or tibial rotation 31 (derived from MRI scans) with patellofemoral cartilage T2 and T1ρ times. Liao et al 32 found that excessive patellar lateral displacement 6 months after reconstruction was associated with elevated lateral patellofemoral compartment T1ρ and T2 values 3 years later. However, Li et al 31 found only “scattered clusters of voxels” demonstrating elevations of these MRI metrics in cases of ACLR with greater external tibial rotation versus those with more normal rotation.…”

“…Given the lack of a perfect control for the ACL-reconstructed knee, use of the contralateral uninjured knee and/or a separate uninjured cohort is common among published reports of post-ACLR gait and cartilage changes. 5,8,27,30-32,41 Limitations of using the contralateral uninjured knee include that pathological changes also occur to this knee after ACL injury; thus, these knees cannot be considered “normal.” Limitations to use of young and healthy uninjured reference cohorts that can be considered to have normal knees include difficulty matching biological and anatomic factors. Despite mitigation of these limitations through our use of both these reference groups, the possibility remains that aspects of knee pathology not accounted for in the regression models may influence the observed relationships among patellofemoral UTE-T2*, gait, and patient-reported outcomes (eg, morphologic change to the index limb, injury to the contralateral limb, mechanical alignment, knee stability, synovitis, differences in biological age, and the patient’s activity level and lifestyle with respect to deep knee flexion).…”

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

“…Several studies have reported excessive patellar lateral displacement and lateral tilt at 6 months after ACLR in either static or dynamic tasks. 16,17,33 One study reported increased patellar lateral rotation (valgus rotation) during a static lunge, 33 whereas others reported decreased patellar lateral rotation. 16,17 From a biomechanical standpoint, altered patellar kinematics may lead to decreased PFJ contact area and elevated contact forces, 28 suggesting detrimental effects on the articular cartilage of the patella and trochlea.…”

“…16,17,33 One study reported increased patellar lateral rotation (valgus rotation) during a static lunge, 33 whereas others reported decreased patellar lateral rotation. 16,17 From a biomechanical standpoint, altered patellar kinematics may lead to decreased PFJ contact area and elevated contact forces, 28 suggesting detrimental effects on the articular cartilage of the patella and trochlea. Indeed, studies have demonstrated associations between patellar malalignment and worsening of PFJ cartilage lesions as well as changes in cartilage composition, 16,18,19 both of which are features of early OA degeneration.…”