Preoperative subacromial autologous conditioned plasma (ACP) injections and histological and immunohistochemical findings in degenerative supraspinatus tendon tears - results of a prospective comparative cohort study.

BACKGROUND: Degenerative supraspinatus tendon quality is a key determinant of healing after rotator cuff repair, and advanced histological degeneration has been associated with increased retear rates. While platelet-rich plasma (PRP) has been extensively studied as an intraoperative adjunct, the potential role of preoperative biological tissue conditioning using platelet-rich plasma remains poorly defined.

HYPOTHESIS/PURPOSE: The purpose of this study was to evaluate the association of preoperative subacromial PRP injections (autologous conditioned plasma, ACP®, Arthrex, Naples, Fl.) with histological and immunohistochemical characteristics of degenerative supraspinatus tendons at the time of rotator cuff repair. It was hypothesized that preoperative ACP treatment would be associated with lower Bonar and degeneration scores compared with untreated controls.

METHODS: A prospective comparative cohort study was performed including patients undergoing arthroscopic repair of isolated, degenerative full-thickness supraspinatus tendon tears. The intervention group received three preoperative subacromial ACP injections (two in one patient) within 3 to 4 weeks before surgery, with the final injection administered no more than 1 week preoperatively. A control group of patients who declined ACP did not receive biological preconditioning. Intraoperatively, tendon biopsies were harvested from the lateral edge of the supraspinatus tendon. The Bonar score and a semiquantitative degeneration score were the co-primary endpoints. Ki-67, CD31 and CD45/LCA immunostaining were exploratory endpoints.

RESULTS: Fifty-four patients were included (ACP group, n = 24, control group, n = 30). The ACP group had lower Bonar scores (6.5 ± 2.0 vs 8.2 ± 1.3, mean difference -1.7, 95% CI -2.7 to -0.7, adjusted P = .044) and lower degeneration scores (1.7 ± 0.8 vs 2.2 ± 0.6, mean difference -0.5, 95% CI -0.9 to -0.1, adjusted P = .044) than controls. CD31 immunostaining was higher in the ACP group, but this difference was not significant after correction for multiple testing (adjusted P = .100). Ki-67, CD45/LCA, reparative changes and the proportion of necrotic tissue did not differ between groups.

CONCLUSION: Preoperative subacromial ACP injections were associated with lower Bonar and degeneration scores in degenerative supraspinatus tendons at the time of rotator cuff repair. The differences were small, the difference in Bonar score was below the predefined minimal clinically important difference, and the clinical relevance of these findings is unclear.