MRI Evaluation of Bipolar Bone Loss Using the On-Track Off-Track Method: A Feasibility Study.

ABSTRACT

OBJECTIVE: The purpose of this study was to determine whether the simultaneous MRI evaluation of Hill-Sachs lesions and glenoid bone loss by use of the on-track off-track method can be used to predict engagement during arthroscopy. MATERIALS AND METHODS: The records of 75 consecutively registered patients (60 male patients, 15 female patients) with a history of previous anterior shoulder instability who underwent preoperative MRI of the shoulder and arthroscopy at our institution were reviewed. A total of 76 MRI examinations were included. Two readers reviewed the MR images of each patient blindly and independently and used the on-track off-track method to predict engagement. These results were compared with the findings related to engagement seen during arthroscopy, which was performed by one of seven orthopedic surgeons. Statistical analyses included Fisher exact test, logistic regression, ROC analysis, and calculation of intraclass correlation coefficients. RESULTS: Using the on-track off-track technique of reading MR images, the reviewers correctly predicted 13 of the 18 engaging (off-track) lesions (sensitivity, 72.2%). Among the 58 shoulders that did not engage (on-track), they correctly predicted 51 (specificity, 87.9%). Overall, the accuracy of the on-track off-track method was 84.2% with a positive predictive value of 65.0% and negative predictive value of 91.1%. CONCLUSION: Our study showed that the on-track off-track method can be used in MRI to accurately assess the bipolar bone loss seen in patients with anterior shoulder instability for predicting the presence of engaging, or off-track, lesions. This information can be used preoperatively to help guide the type of stabilization procedure performed on patients with anterior shoulder instability.