Quantitative UTE MRI Differences in the Meniscus Following ACL Reconstruction: A Prospective Cohort Study Using 3D Ultrashort Echo Time Adiabatic T1rho and Magnetization Transfer Imaging.

BACKGROUND

ACLR is associated with altered joint loading and increased risk of post-traumatic osteoarthritis. Conventional MRI has limited sensitivity to early meniscal differences because of short-T2 signal decay and magic-angle effects.

PURPOSE: To evaluate whether 3D ultrashort echo time imaging-based adiabatic T1rho (UTE-Adiab-T1rho) and ultrashort echo time imaging-based macromolecular fraction (UTE-MMF) identify regional quantitative MRI differences after ACLR.

STUDY TYPE: Prospective longitudinal cohort study.

POPULATION: 30 control scans, 19 ACLR scans at 6-12 months, and 13 ACLR scans at 12+ months were analyzed. Mean ages were 34.5, 34.5, and 37.2 years; female/male counts were 15/15, 9/10, and 8/5.

FIELD STRENGTH/SEQUENCE: Participants underwent 3-T knee MRI with 3D fat-saturated UTE-Adiab-T1rho and UTE magnetization transfer sequences.

ASSESSMENT: UTE-Adiab-T1rho and UTE-MMF maps were generated with single-component exponential and two-pool magnetization transfer models. Values were extracted from four meniscal regions of interest by a blinded reader, with blinded redelineation in a subset. Patient-reported outcomes included International Knee Documentation Committee, Knee Injury and Osteoarthritis Outcome Score, and Western Ontario and McMaster Universities Osteoarthritis Index scores.

STATISTICAL TESTS: Linear mixed-effects models accounted for repeated observations. Benjamini-Hochberg FDR correction was applied.

RESULTS

UTE-Adiab-T1rho showed significant group (q = 0.001) and region (q < 0.001) effects. Compared with controls, UTE-Adiab-T1rho was higher in LAM at 6-12 months (+5.60 ms; q = 0.035) and 12+ months (+7.09 ms; q = 0.028), and in LPM at 12+ months (+6.35 ms; q = 0.035). UTE-MMF showed significant group (q = 0.041) and region (q < 0.001) effects. LPM UTE-MMF was lower than controls at 6-12 months (-3.56 percentage points; q = 0.028) and 12+ months (-3.10 percentage points; q = 0.049). No 6-12 versus 12+ month MRI or PROM contrast survived FDR correction. MRI-PROM associations were not FDR-significant (all q ≥ 0.383).

DATA

CONCLUSION

UTE-Adiab-T1rho and UTE-MMF mapping identified regional MRI differences after ACLR. Pairwise differences were concentrated in lateral regions, but corrected group-by-region interactions were not significant. PROMs were worse after ACLR but did not differ between postoperative windows after correction.

EVIDENCE LEVEL: 2.

TECHNICAL EFFICACY STAGE: 2.