Longitudinal Quantitative Mapping of Meniscal Morphological and Signal Intensity Differences After ACL Surgery.

BACKGROUND: Meniscal tears are frequently associated with anterior cruciate ligament (ACL) injuries. Evaluating longitudinal changes in meniscal integrity using quantitative magnetic resonance imaging after ACL surgery may provide valuable insight into joint recovery and subsequent reinjury risk.

HYPOTHESES: (1) The cross-sectional area (CSA) and normalized signal intensity (SI) profiles of the lateral and medial menisci for the surgical knees would be greater than those of the contralateral uninjured knees observed at 6, 12, and 24 months after surgery. (2) The CSA and Constructive Interference in Steady State (CISS) SI profiles obtained at 24 months would be closer to those of the contralateral limb when compared with those of the 6- and 12-month time points.

METHODS: Deidentified postsurgical CISS magnetic resonance imaging scans of patients (n = 82; median age 17.6 years; 42 females and 40 males; 57 ACL restoration and 25 ACL reconstruction) were analyzed. CSA and normalized CISS SI values were extracted from the lateral and medial menisci to create morphological profiles. Statistical parametric mapping was used to compare the CSA and normalized CISS SI profiles between the surgical and contralateral limbs to identify specific regions that were different among the menisci at 6, 12, and 24 months.

RESULTS: The CSA and normalized CISS SI profiles of the anterior region of the medial menisci and lateral menisci for the surgical knees were greater than those of the contralateral uninjured knees, observed at 6, 12, and 24 months after surgery, whereas the posterior region CSA of the medial menisci was smaller. The lateral meniscus on the operated limb had a larger CSA and higher normalized CISS SI values than the lateral meniscus in the contralateral limb. The CSA and CISS SI profiles obtained at 24 months did not approach those of the contralateral limb.

CONCLUSION: Significant changes occurred in both menisci after ACL surgery that did not return to baseline levels within 2 years. It is important to account for anatomic location when evaluating meniscal morphology in surgical knees and when evaluating the effects of ACL injuries on the surrounding tissues.

STUDY DESIGN: Cohort study; Level of evidence, 3.