Accuracy of MRI scan in the diagnosis of ligamentous and chondral pathology in the ankle
Introduction
Magnetic resonance imaging (MRI) has become the imaging the modality of choice for the diagnosis of many conditions affecting the knee and shoulder [1]. In joints such as the wrist the MRI scan is less useful as a diagnostic tool [2]. The aim of our study is to analyse the accuracy of MRI in diagnosing ligamentous/chondral lesions in the ankle and to compare it with arthroscopic findings. Arthroscopic diagnosis was considered to be the gold standard.
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Methods
Data of all the patients who underwent arthroscopy of the ankle between December 2005 and July 2008 were collected. A total of 24 patients underwent arthroscopy as well as MRI during this period for chronic ankle pain and/or instability. The study specifically looked at accuracy of MRI in detecting tears of the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL) and osteochondral lesions (OCD).
Patients underwent imaging with 1 T MRI machine, using standard imaging sequences and
Results
Analysis of the data confirmed that specificity and positive predictive value of MRI is 100% for detection of tears of ATFL, CFL and OCD. The sensitivity is 67% for ATFL tears, 40% for CFL tears and 73% for OCD. The negative predictive value of MRI is 90% for ATFL tears, 86% for CFL tears and 69% for OCD. The overall accuracy of MRI is 91.7% for ATFL tears, 87.5% for CFL tears and 83.3% for OCD. The results are shown in Table 1.
Four patients had intra deltoid ligament tear with only one being
Discussion
Lateral ankle sprains represent a high proportion of sports related traumatic lesions [3]. The ATFL is the weakest and the most frequently torn ankle ligament followed by CFL [3]. MR imaging of the ankle has received considerably less attention in the past [1]. This could be due to the relative complexity of ankle anatomy and the smaller size of many clinically relevant structures [1].
Normal ankle ligaments are predominantly low signal intensity but may have longitudinal streaks of intermediate
Conclusions
We conclude that MRI scan has very high specificity and positive predictive value in diagnosing tears of ATFT, CFL and osteochondral lesions. However sensitivity and negative predictive value is low with MRI. In a symptomatic patient negative results on MRI must be viewed with caution and an arthroscopy is advisable for a definitive diagnosis and treatment. It could be argued that these findings may differ with higher resolution scanner but the evidence for this is not currently available.
Conflict of interest
None of the authors of the above manuscript has any conflict of interest, which may arise from being named as an author on the manuscript.
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