Correlation Between T1ρ MRI and Arthroscopy in Adults with Chondromalacia

Walter RT Witschey¹, Ari Borthakur², Matt Fenty², J. Bruce Kneeland³, Jess Lonner⁴, Erin Leigh McArdle², Ravinder Reddy²

To determine whether mild and moderate osteoarthritis (OA) observed during arthroscopy correlates with changes in cartilage as detected with T1rMRI, 9 asymptomatic subjects (2 men and 7 women) and 6 patients (3 men and 3 women) in whom one or more regions of mild or moderate chondromalacia had been demonstrated at arthroscopy were recruited for this study. MRI was performed 2-3 months post-arthroscopy using sagittal T1-weighted and axial and coronal T1r MRI from which spatial T1r relaxation maps were calculated. Statistical analysis of the difference between the asymptomatic subjects and the patients in whom changes of OA had been demonstrated at arthroscopy was performed using multivariate ANOVA and bootstrap confidence interval tests. Correlation between arthroscopy and T1rMRI was determined by either calculating mean compartment T1r or by calculating the mean of a large focally elevated region of T1r within a compartment. Median T1rrelaxation times among symptomatic and asymptomatic subjects were significantly different (p < 0.001) and symptomatic T1r exceeded asymptomatic articular cartilage median T1r by 2.5 to 9.2 ms. Patellar T1r was 2.5-8.3 ms higher than the tibial compartment (p < 0.01). In 8 observations of mild (grade 1 and 2) osteoarthritis at arthroscopy, mean compartment T1r was elevated in 5, but in all cases, large foci of increased Tr were observed. In 6 cases of moderate or severe chondromalacia, compartment mean T1r was always elevated. T1r MRI correlated with arthroscopically confirmed diffuse or focal chondral damage and may be used to noninvasively detect early changes of OA in cartilage.