Delayed Gadolinium-Enhanced MR Imaging of Cartilage (dGEMRIC) following ACL injury

Abstract

Objective: Early detection of glycosaminoglycan (GAG) loss may provide insight into mechanisms of cartilage damage in the anterior cruciate ligament (ACL)-injured patient. We hypothesized that tibial and femoral Delayed Gadolinium-Enhanced MR Imaging of Cartilage (dGEMRIC) indices would be lower in the medial compartment of the ACL-injured knee than in the contralateral, uninjured knee, and that scan order (i.e., whether the injured or the uninjured knee was imaged first) would not affect the indices.

Methods: 15 subjects with unilateral ACL injuries received a double dose of gadolinium [Gd(DTPA)(2-)] intravenously. After 90 min, both knees were sequentially imaged. The injured knee was scanned first in the odd-numbered subjects and second in the even-numbered subjects. The dGEMRIC indices of the median slice of the medial compartment were determined using the MRIMapper software. Index comparisons were made between knee status (ACL-injured vs uninjured), scan order (ACL-injured first vs uninjured first), and cartilage location (tibia vs femur) using a mixed model.

Results: There was a significant difference in the mean dGEMRIC indices of the medial compartment between injured and uninjured knees (P<0.007). On average, there was a 13% decrease in the dGEMRIC index of the injured knee compared to the uninjured knee. There were no significant effects due to test order (P=0.800) or cartilage location (P=0.439).

Conclusions: The results demonstrate lower GAG concentrations in the medial compartment of the femoral and tibial articular cartilage of the ACL-injured knee when compared to the contralateral uninjured knee. The dGEMRIC indices were not sensitive to scan order; thus, sequential imaging of both knees is possible in this patient population.