Histological changes and neural elements in the subacromial bursa on patients with rotator cuff tear: Pilot study

Objective: This study aimed to investigate the neural elements of the subacromial bursa (SAB) in rotator cuff tears. Materials and methods: Twenty patients with rotator cuff tears were recruited, and their visual analog scale (VAS) score, duration of symptoms, and range of motion (ROM), including flexion, external rotation, and internal rotation were evaluated. Tear size was measured using magnetic resonance imaging (MRI). The SAB specimens obtained during arthroscopic rotator cuff repair were studied using routine hematoxylin and eosin staining and immunohistochemistry (S-100 protein and PGP 9.5 protein). The SAB specimen for the control group was obtained from 2 fresh cadavers and 2 patients with acute humeral shaft fracture. The Mann-Whitney U test was applied to assess the difference between histological findings of the rotator cuff tear group and control group. The correlation between the histological findings and clinical features was evaluated using the Spearman correlation coefficient. Results: The mean duration of symptom was 10.2 +/- 6.4 months. The preoperative average VAS score was 2.9 +/- 1.2. The degrees of preoperative ROM in forward flexion and external and internal rotations were 143.8 +/- 19.5, 49.5 +/- 23.1, and -4.3 +/- 4.2, respectively. The tear was 2.0 +/- 0.9 cm. For histological findings, the number of neural elements per low power field in the rotator cuff tear group was significantly less than the control group in both immunohistochemical stainings (S-100: 0.5 +/- 0.7 vs 2.8 +/- 0.5, p < .01; PGP 9.5: 0.4 +/- 0.7 vs 3.5 +/- 0.6, p < .01). During the correlation analysis, the number of neural elements in the PGP 9.5 staining was negatively correlated with the ROM in forward flexion and external rotation. Conclusion: This study revealed that chronic rotator cuff tears may induce degeneration of neural elements in SAB.