Osteochondral Lesions of the Talus

Purpose of the study: The purpose of this study was to compare the diagnostic ability of T1-weighted 3-D fatsuppressed FSPGR with that of conventional MRI in the detection of cartilage defects in the ankle by looking at sensitivity, specificity, and accuracy of diagnosis compared with arthroscopic findings.

The study: Thirty-two consecutive patients with clinically suspected cartilage lesions undergoing three-dimensional fat-suppressed FSPGR MRI and conventional MRI were assessed.

Results: Arthroscopy revealed 21 patients with hyaline cartilage defects and 11 with normal ankle joints. The sensitivity, specificity, and accuracy of the two methods for detecting articular cartilage defect were 62%, 100%, and 75%, respectively, for conventional MRI and 91%, 100%, and 94% for three-dimensional fat-suppressed FSPGR MRI.

Author’s conclusion: T1-weighted three-dimensional fat-suppressed FSPGR MRI is more sensitive than is conventional MRI in detecting defects of articular cartilage covering osteochondral lesions of the talus.

Study strengths:

• Appropriate spectrum of patients enrolled prospectively and consecutively  

• Index test compared to appropriate gold standard

• All patients received the index test and the gold standard

• Physicians evaluating the index test were blinded to the reference test  

Study weaknesses:

• None

Comments:

Both tests had the same specificity but FSPGR MRI had a higher sensitivity. This appears to be a carefully planned and reported study limiting bias which allows confidence when interpreting the results. Clinical examination of the author’s population yields a pre test probability of 67%. A negative MRI has a – Likelihood Ratio of 0.38 (0.24-0.69)  which reduces post test probability to 45%, while a negative FSPGR MRI has a – Likelihood Ratio of 0.09 (0.03-0.37) which reduces post test probability to 20%. The FSPGR MRI is a better test to rule out osteochondral lesions of the talus than conventional MRI.

6/2010