No differences in histopathological degenerative changes found in acute, trauma-related rotator cuff tears compared with chronic, nontraumatic tears

PURPOSE: Acute trauma-related rotator cuff tears are believed to have better healing potential than chronic tears due to less degenerative changes of the tendons. However, the histopathological condition of tendons from trauma-related tears is not well investigated. The purpose of this study was to explore specific histopathological features in tendons from acute trauma-related full-thickness rotator cuff tears and to compare them to findings in tendons from nontraumatic, chronic tears. METHODS: In a prospective cohort study, 62 previously asymptomatic patients [14 women, median age 61 years (range 42–75)] with trauma-related full-thickness rotator cuff tears were consecutively included. Arthroscopic repair was performed within 30 (median, IQR 25–37) days after the injury. During surgery, tissue biopsies were harvested from the supraspinatus tendons in 53 (86%) of the patients. In addition, similar biopsies were harvested from 10 patients undergoing surgery for chronic tears without history of trauma. All tissue samples were examined by a well-experienced pathologist under light microscope. Tendon degeneration was determined using the Bonar score whereas immunostaining was used for proliferation (Ki67), inflammation (CD45), apoptosis (p53) and haemosiderin staining to study traces of bleeding. RESULTS: The median (IQR) Bonar score for the acute trauma-related biopsies was 10.5 (7.5–14.5) compared to 11 (5–12.8) for the control group with no statistically significant difference between the groups. No statistically significant between-group difference was found for the inflammatory index whereas tendons from patients with trauma-related full-thickness rotator cuff tears had statistically significantly higher apoptosis [3.1 (0.5–8.9) vs. 0.1 (0–1.5), p = 0.003] and proliferation [4.0 (1.8–6.9) vs. 0.4 (0–2.0), p = 0.001) indices than those undergoing surgery for chronic tears. Positive haemosiderin staining was found in 34% of tissue samples from patients with trauma-related tears compared to 10% in the control group (n.s). CONCLUSION: This study suggests that there is no difference with regard to degenerative changes between supraspinatus tendons harvested from patients with acute, trauma-related rotator cuff tears and patients with nontraumatic, chronic tears. LEVEL OF EVIDENCE: II. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00167-022-06884-w.