Quantitative MR imaging evaluation of the cartilage thickness and subchondral bone area in patients with ACL-reconstructions 7 years after surgery.

OBJECTIVE: To evaluate the cartilage thickness (ThC) and subchondral bone area (tAB) of the operated and contra-lateral non-operated (healthy) knees in patients with anterior cruciate ligament (ACL)-reconstruction 7 years after surgery using a quantitative and regional cartilage MR imaging (qMRI) technique. METHODS: Charts of 410 patients with ACL-reconstructions were retrospectively reviewed. Fifty-two patients (male/female, 28/24; mean age, 33.3 years) were included. Patients underwent KT-1000 testing and qMRI of both knees using coronal fat-saturated 3D spoiled gradient-recalled echo (SPGR) sequences (TR/TE, 44/4 ms) at 1.5 T. Quantitative analyses of ThC and tAB in the femoro-tibial cartilage plates were performed using a subregional approach. In addition, qualitative and quantitative assessment of femoral condyle shapes was performed. t tests with Bonferroni corrections were used for statistical analysis of side-to-side differences between the operated and non-operated knees. RESULTS: KT-1000 testing was abnormal in 3/52 patients (6%). Lateral femoral tAB was significantly lower (-9.2%), and medial tibial tAB was significantly larger (+2%) in the operated vs non-operated knee (P<0.001). Regional and subregional ThC side-to-side differences were less than 0.1mm and, except for the external lateral femoral subregion, they were not statistically significant. Flattened and broader shapes of medial femoral condyles (P<0.001) were found in operated knees. No significant association of presence of cartilage or meniscus lesions at surgery with ThC 7 years post-operatively was found (P=0.06-0.98). CONCLUSION: There is evidence for changes in the tAB and femoral shape 7 years post-ACL-reconstruction, but no side-to-side differences in subregional ThC were found between the operated and contra-lateral non-operated knees.