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MRI UTE‐T2* shows high incidence of cartilage subsurface matrix changes 2 years after ACL reconstruction

Alteration of deep cartilage matrix has been observed following anterior cruciate ligament (ACL) injury, evidenced by elevated MRI UTE‐T2* values measured in small, 2‐D cartilage regions of interest. This Level I diagnostic study seeks to more thoroughly evaluate deep cartilage matrix changes to medial tibiofemoral UTE‐T2* maps 2 years after ACL reconstruction and examine the relative utilities of 3‐D compared to 2‐D assessments of cartilage UTE‐T2* maps. Thirty‐eight ACL‐reconstructed and 20 uninjured subjects underwent MRI UTE‐T2* mapping. “Small” single mid‐sagittal 2‐D and larger 3‐D “tread mark” regions of interest were manually segmented and found to be correlated in medial cartilage (r > 0.58, p < 0.005). 3‐D analyses of UTE‐T2* maps showed differences to medial tibial cartilage between ACL‐reconstructed and uninjured subjects (p = 0.007) that were not detected by smaller 2‐D regions (p > 0.46). Quantitative comparisons show 14/38 (37%) ACL‐reconstructed subjects have values >2 standard deviations higher than uninjured controls. Among a subset of ACL‐reconstructed subjects with no morphologic MRI evidence of medial tibiofemoral cartilage or meniscal pathology (n = 12), elevated UTE‐T2* values in “small” 2‐D femoral (p = 0.011), but not larger 3‐D tread mark regions of interest (p > 0.13), were observed. These data show the utility of 2‐D UTE‐T2* assessments of mid‐sagittal weight‐bearing regions of medial femoral cartilage for identifying subclinical deep cartilage matrix changes 2 years after ACLR. Clinical Significance: Mid‐sagittal single slice 2‐D UTE‐T2* mapping may be an efficient means to assess medial femoral cartilage for subsurface matrix changes early after ACL reconstruction while 3‐D assessments provide additional sensitivity to changes in the medial tibial plateau. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:370–377, 2019.