Associations between fatty infiltration of rotator cuff muscles and rotator cuff tear location and severity

Abstract

Abstract Background The fatty infiltration (FI) of rotator cuff muscles in patients with rotator cuff tear is affected by a range of factors, but the associations between FI grade and patient factors, as well as the location and severity of adjacent rotator cuff tears, are not well-known. The hypothesis of this study is the progression of FI grade of each of the rotator cuff muscles is affected by the severity of any tear in the adjacent rotator cuff. Methods The study examined 373 shoulders of 348 patients (264 males and 109 females; mean age was 62.8 years old) who had undergone arthroscopic rotator cuff surgery. Age at surgery, sex, body mass index (BMI), and duration of symptoms were investigated. The FI grades of the supraspinatus (SSP), infraspinatus (ISP), and subscapularis (SSc) muscles were assessed on preoperative MRI according to the Goutallier classification. Intraoperatively, the severity of the posterior-superior rotator cuff (SSP-ISP) tear was classified on a six-grade scale modified the Cofield classification, and that of the SSc tear on a six-grade scale according to the Lafosse classification. We performed descriptive statistics on these results and examined their relationship with FI grade. Results The FI grades of the SSP and the ISP were significantly associated with the severity of the tears in those muscles, and the FI grade of the SSc was significantly associated with the severity of the tear in that muscle. Furthermore, the FI grades of the SSP and the ISP were significantly associated with SSc tear severity, and the FI grade of the SSc was significantly associated with SSP-ISP tear severity. Conclusions The progression of FI grade of each of the rotator cuff muscles is affected not only by the tear severity in the muscle concerned, but also by the severity of any tear in the adjacent rotator cuff.