Shoulder muscle changes in patients with type 2 diabetes mellitus who have a painful shoulder: a quantitative muscle ultrasound study

Background It is assumed that in patients with diabetic neuropathy, muscle denervation can result in shoulder disorders. Muscle denervation will lead to changes in muscle architecture, which can be assessed by quantitative muscle ultrasound (QMUS). The aim was to investigate whether increased muscle echogenicity, as a sign of neuropathy, is more often present in patients with shoulder pain who have type 2 diabetes mellitus (T2DM) than in those without. Methods Sixty-six patients with T2DM and 23 patients without diabetes mellitus (DM) having shoulder pain were included. Quantitative muscle ultrasound images were obtained bilaterally from the biceps brachii, deltoid, and supra- and infraspinatus muscles. The mean echogenicity (muscle ultrasound grey value) was transformed into z-scores and compared to reference values obtained from 50 healthy participants. Associations between muscle echogenicity and clinical variables were explored. Results In painful shoulders of both patients with T2DM and patients without DM, mean echogenicity z-scores of all muscles were significantly increased compared to healthy controls. No significant differences in echogenicity between patients with T2DM and those without DM were found. In patients with T2DM, a distal symmetric polyneuropathy was significantly associated with increased echogenicity of all muscles except the infraspinatus muscle. Conclusions These findings indicate that patients with painful shoulders, irrespective of having T2DM, seem to have abnormal shoulder muscles. Future studies are needed to elucidate whether neuropathy or other conditions lead to these muscle changes.