Supraspinatus muscle atrophy in relation to aging with or without shoulder pathology: A radiographic study.

Introduction: Supraspinatus muscle atrophy is commonly associated with shoulder disease, but the effect of ageing on atrophy is not well understood. It was the aim of this study to investigate this effect using MRI scans in older patients. Methods and materials: A retrospective review of MRI scans in patients aged >70 years was performed between Jan 2016-Dec 2018.Both normal and abnormal scans were included in the analysis which included quantifying muscle atrophy of the supraspinatus using Thomazeu's occupation ratio. Results: There were 39 normal shoulder MRI scans with a mean age of 75 years (range: 70-88) and 163 abnormal scans with a mean age of 77 years (range: 70-93). The mean supraspinatus occupation ratio for normal MRI scans was 0.57 (range: 0.33-0.86) and abnormal scans 0.35 (range: 0.17-0.90). Occupation ratio was maintained with advancing until the age of 85 years before undergoing a significant declin following this. Conclusion: This study has shown that the occupation ratio is significantly reduced with shoulder disease, but normal shoulders do not undergo significant atrophy of supraspinatus tendon with increasing age. An occupation ratio of <0.32 is unlikely to occur in normal shoulders and this awareness may be useful when planning shoulder surgery, specifically shoulder arthroplasty.