To evaluate the relationship between severity of supraspinatus tendon tear and the thickness of acromion, acromiohumeral interval and superior migration of humeral head measured by magnetic resonance imaging (MRI).

A retrospective analysis was performed on 102 patients who underwent shoulder MRI scans, from July 2020 to June 2022, at Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School. Patients with history of surgery, infection, tumour and abnormal bone structure of shoulder were excluded. According to the condition of supraspinatus tendon, the patients were divided into a non-rotator cuff injury group (37 patients), a partial supraspinatus tendon tear group (37 patients) and a complete supraspinatus tendon tear group (28 patients). The thickness of acromion, acromiohumeral interval and distance of superior migration of humeral head were measured on the oblique sagittal plane. Differences between the groups were analysed. Spearman correlation analysis was used to evaluate the relationship between the degree of supraspinatus tendon tear and the acromial thickness, acromiohumeral interval and superior migration of humeral head.

The average thickness of acromion in non-rotator cuff injury group, partial supraspinatus tendon tear group and complete supraspinatus tendon tear group were found at (6.60±0.16) mm, (8.24±0.19) mm and (8.88±0.26) mm, respectively and there were statistical differences between the three groups (F=35.509, P<0.05). There was a significant positive correlation between the thickness of acromion and the degree of supraspinatus tendon tear (r=0.636, P<0.001). The average acromiohumeral interval in non-rotator cuff injury group, partial supraspinatus tendon tear group and complete supraspinatus tendon tear group were found at (8.77±0.22) mm, (7.85±0.21) mm and (5.89±0.31) mm, respectively. Pairwise comparisons among the three groups were statistically significant (F=34.629, P<0.05). There was a negative correlation between an acromiohumeral interval and the degree of supraspinatus tendon tear (r=-0.592, P<0.001). The results of distance of superior migration of humeral head in non-rotator cuff injury group, partial supraspinatus tendon tear group and complete supraspinatus tendon tear group were -0.25 (-0.77, 0) mm, 0 (0, 0) mm and 0.72 (0, 1.52) mm, respectively. There were statistical differences between the three groups (H=43.813, P<0.05). It was found that there was a significant positive correlation between the superior migration of humeral head and the degree of supraspinatus tendon tear (r=0.646, P<0.001).

The thickness of acromion, acromiohumeral interval and superior migration of humeral head measured by MRI were correlated with the severity of supraspinatus tendon tear. It has been found that as a supraspinatus tendon tear is getting aggravated, there will be an increase in the thickness of acromion and the distance of superior migration of humeral head and together with a decrease of acromiohumeral interval.