The importance of CT for the pre-operative surgical planning in recurrent anterior shoulder instability

Abstract

Background: MRI is the current pre-operative imaging standard in recurrent anterior shoulder instability; however, CT has increasingly gained interest due to its advantages in the detection of bony glenoid defects. This study compares the value of CT imaging and MRI for pre-operative surgical planning in recurrent anterior shoulder instability.

Methods: Between 2006 and 2009, 83 patients presented to the author's department with recurrent anterior shoulder instability. For 48 patients, both, pre-operative MRI and CT images were available. The respective patho-morphological descriptions were retrospectively compared with the intra-operative findings. The effect of each imaging technique on the pre-operative surgical planning was analyzed and the accuracy in predicting the necessity of open versus arthroscopic surgery was compared.

Results: In determining the necessity of open versus arthroscopic surgery CT imaging rendered an inaccurate prediction in 4.8 % of the cases which is less than the 25.0 % calculated for MRI. (p = 0.019). MRI showed a low sensitivity (35.3 %) in the detection of significant glenoid bone defects (≥20 % of the glenoid width measured on en-face views using a best-fit circle technique) while CT imaging provided an accurate prediction of the intra-operative finding in all cases.

Conclusion: Despite the advantages of MRI in the detection of soft tissue damages in recurrent anterior shoulder instability CT imaging proved to be more important for pre-operative planning by prevailing in the detection of glenoid defects. Therefore, the replacement of MRI as preoperative imaging standard with CT imaging is recommended.