Value of magnetic resonance arthrography in post-traumatic anterior shoulder instability prior to arthroscopy: a prospective evaluation of MRA versus arthroscopy

Abstract

This prospective study was designed to evaluate the value of magnetic resonance arthrography (MRA) after traumatic anterior shoulder instability prior to arthroscopy. Patients included had two or more shoulder dislocations, at least the first being traumatic. MRA images were scored for Hill Sachs lesions, superior labral anterior posterior (SLAP) lesions, rotator cuff tears, glenohumeral ligament (GHL) lesions and Bankart lesions. Consequently, a standardized shoulder arthroscopy was performed. Five surgeons were involved in the study, initially blinded to the MRA results. MRA and arthroscopic findings were compared. Interobserver agreement was calculated by using Cohen's Kappa coefficients (κ). Eighteen patients (13 male, 5 female) were included (mean age 26.1years). Hill Sachs lesions demonstrated fair agreement (κ=0.33) whereas for SLAP lesions moderate agreement was calculated (κ=0.43). On MRA, four partial thickness rotator cuff lesions were seen, not being stated by arthroscopy. GHL lesions were described on MRA in 15 patients; only two patients turned out to have GHL lesions at arthroscopy. Two arthroscopically diagnosed Bankart lesions which needed surgical treatment were not detected by MRA (moderate agreement, κ=0.47). In patients with post-traumatic anterior glenohumeral instability MRA shows many lesions that can not be confirmed by arthroscopy and therefore do not have therapeutical consequences. On the other hand some labral lesions which do need surgical treatment are not detected on MRA. At least from this study, it can be concluded that MRA has limited value prior to the arthroscopic treatment of post-traumatic shoulder instability.