Detection of Posttraumatic Cartilage Injury Using Quantitative T1rho Magnetic Resonance Imaging

Abstract

Cartilage injuries following trauma are a common problem and can lead to premature, secondary osteoarthritis. Standard magnetic resonance imaging techniques can detect cartilage breakdown associated with morphological changes, such as decreases in cartilage thickness and volume, but it cannot detect early changes of the cartilage matrix. There is a need for a noninvasive method with which to diagnose articular cartilage abnormalities at early stages in order to initiate early treatment prior to the macroadaptive changes seen on radiographs. Early events in the development of cartilage breakdown include the loss of proteoglycans, changes in water content, and molecular-level changes in collagen1,2. Early diagnosis of cartilage injury requires the ability to detect changes in proteoglycan concentration and collagen integrity noninvasively before gross morphological changes occur. Standard cartilage-dedicated magnetic resonance imaging techniques such as T2-weighted, proton-density-weighted fast-spin-echo sequences and spoiled gradient-echo sequences are inconclusive in quantifying early degenerative changes, especially biochemical changes such as proteoglycan loss3. It appears that T1rho-weighted imaging can provide quantitative measures of pathologic cartilage matrix changes. Previous studies have demonstrated significant differences in T1rho relaxation times when patients with symptomatic osteoarthritis have been compared with normal controls4. In the present study, we describe two cases in which cartilage injuries were not detected with standard morphological magnetic resonance imaging but in which T1rho-weighted imaging was able to detect cartilage abnormalities in vivo that were confirmed at the time of arthroscopy. The patients were informed that data concerning these cases would be submitted for publication. Case 1. A forty-five-year-old man presented with a three-week history of pain in the right knee following a motor-vehicle accident. Clinical examination demonstrated a moderate intra-articular knee effusion, a positive grade-2 Lachman test, and a positive pivot-shift test. The patient also had mild discomfort on the McMurray …