The greater tuberosity radius ratio: maybe a new predictor in diagnosis of rotator cuff tear

Abstract

Background The role of the greater tuberosity of humerus in subacromial impingement should be of equal important as the acromion. In this study we concerned on the morphological characteristics of the greater tuberosity of humerus and proposed the greater tuberosity radius ratio (GTRR) as a new predictor for the diagnosis of rotator cuff tear. We hypothesized that a larger value of the GTRR could increase the risk of developing rotator cuff tear. Methods This was a retrospective study and clinical data and preoperative computed tomography images of the patients with rotator cuff tears (defined as the RCT group, simple size: 61) or without rotator cuff tears (defined as the control group, simple size: 56) were collected. Three-dimensional models of shoulders were established by multiplanar reconstruction of computed tomography scans. In a standard anteroposterior view, the radius of the best-fit circle of the humeral head (the r) and the radius of the concentric circle passing through the most superolateral edge of the greater tuberosity (the R) were measured for each shoulder. The ratio of R and r (R/r) was defined as the greater tuberosity radius ratio (GTRR). Independent samples t tests were used to find significant differences within the r, the R and the GTRR between groups. Receiver operating characteristic (ROC) curve based on the values of GTRR was performed to determine an applied cutoff value which may be useful in clinical practice. Results There was no significant difference in the values of r or R. However, the mean values of GTRR were 1.339 ± 0.143 (range, 1.087–1.684) and 1.244 ± 0.172 (range, 1.040–1.706) in the two groups respectively (p = 0.002). According to the ROC curve, an optimized cutoff value of GTRR was determined as 1.262, whose sensitivity was 72% and specificity was 65% for diagnosis of rotator cuff tear. Conclusion The greater tuberosity of humerus contributes to the mechanisms of rotator cuff tear. The greater tuberosity radius ratio is recommended as a new predictor for diagnosis of rotator cuff tear, with an optimized cutoff value set as 1.262.