Summary
Long-term cartilage degradation following ACL reconstruction is associated with degree of patellofemoral constraint.
Abstract
Introduction
Within 10 years of ACL reconstruction, approximately 50% of patients develop post-traumatic tibiofemoral or patellofemoral osteoarthritis (OA). The current study uses quantitative MRI to relate patellofemoral anatomy and alignment to patellofemoral and tibiofemoral cartilage properties at least 10 years following ACL reconstruction.
Methods
The study included patients who participated in 3T quantitative MRI at least 10 years following ACL reconstruction with a bone-patellar tendon-bone autograft. Cartilage properties were quantified from T1? and T2 relaxation times. Long T1? and T2 relaxation times indicate low concentrations of proteoglycans and collagen within cartilage, respectively. The population included 61 subjects. The population characteristics were: age = 32.9 ± 4.5 years, BMI = 25.8 ± 4.1 kg/m2, 32 females, 29 males. The study was approved by the IRB. Parameters of anatomy and alignment were measured from a 3D non-fat saturated turbo spin echo scan with a 1 mm slice thickness. Cartilage was segmented from a 3D fat saturated Dual Echo Steady State (DESS) scan using automated deep learning algorithms. T1? and T2 relaxation times from fat saturated Magnetization-prepared Angle-modulated Partitioned-k-space Spoiled gradient-echo Snapshots (MAPSS). Relaxation times were averaged for each compartment. Multivariable linear regressions correlated anatomy and alignment against relaxation times for all regions of cartilage. Separate correlations were performed for males and females. Statistical significance was set at p < 0.05.
Results
The most common parameter significantly correlated with increasing relaxation times for males was increasing lateral trochlear inclination (trochlear depth) at the patella, trochlear groove, and medial femoral condyle (r2 = 0.16-0.24, Table 1). The most common parameter significantly correlated with increasing relaxation times for females was decreasing Caton-Deschamps index (low patella) at the trochlear groove and medial tibia (r2 = 0.14-0.22). Low TT-TG distance (small lateral force vector acting on patella) showed the strongest correlation with increasing T2 relaxation times, which occurred at the lateral tibia (r2 = 0.32). Low patellar tilt and low Wiberg index (symmetric patella) were also correlated with increasing relaxation times for the medial and lateral femur, respectively.
Discussion
All measures of anatomy and alignment correlated with increasing T1? or T2 relaxation times indicated patellofemoral constraint within the trochlear groove, for males and females. The results indicate a deep trochlear groove, a low patella within the trochlear groove, medial patellar tilt, a small lateral force vector acting on the patella, and patellar symmetry indicating contact at the medial and lateral facets of the patella are correlated with cartilage degradation that could develop into patellofemoral or tibiofemoral OA.
SIGNIFICANCE/CLINICAL RELEVANCE: At least 10 years following ACL reconstruction with a bone-patellar-tendon bone autograft, parameters indicating the patella is well constrained by the trochlear groove are correlated with cartilage degradation that could develop into patellofemoral or tibiofemoral OA.