Posterior shift of the humeral head in patients with rotator cuff tears and its clinical implication

Abstract

In some patients with rotator cuff tears, the axial view of magnetic resonance imaging (MRI) shows posterior shift (PS) of the humeral head to the glenoid. This is considered a result of loss of centralization due to loss of rotator cuff function. However, the clinical implication of PS has not been reported. The purpose of this study was to investigate the clinical implication of PS in arthroscopic rotator cuff repair (ARCR). We included consecutive patients who underwent ARCR at our institute and were followed up for at least 1 year. PS was identified as a 2-mm PS of the humeral head to the glenoid in the axial view of MRI preoperatively. The tear size and fatty degeneration (Goutallier classification) were also evaluated using preoperative MRI. Retear was evaluated using MRI at 1 year postoperatively. As a result, 135 shoulders were included in this study. Ten PS cases (including seven retear cases) were observed preoperatively. Fifteen retears (three small-medium tears and seven large-massive tears) were observed postoperatively. PS had significant a correlation with retear, tear size, and fatty degeneration (p = 0.01 for all). The odds ratio of PS for retear was 33.8, which was higher than that of tear size (> 3 cm) and fatty degeneration (grades 3 and 4). In conclusion, PS may be a new predictor of retear after ARCR.