Collagen Injections for Rotator Cuff Diseases: A Systematic Review

Background: Due to its anatomy and function, the rotator cuff (RC) is vulnerable to considerable morbidity. The prevalence of RC diseases (RCD) in the general population is of 5–39%, and it increases with age, reaching over 30% in patients over 60 years old. The aim of the present systematic review is to investigate the effects of collagen injections use for the treatment of RCD. Methods: A systematic search of scientific electronic databases was performed up to October 2023, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Two independent authors performed the search and evaluated the articles. The inter-rater reliability in the quality assessment was evaluated using the Cohen’s kappa coefficient; while the Modified Coleman Methodology Score (CMS) was used to evaluate the methodological quality of the articles included in this systematic review. Results: A total of seven articles were included with the overall quality of the included articles being evaluated as fair. Despite the use of different types of collagen and injections protocols, and different scores applied, each of the included study showed clinically relevant improvements. However, given the high grade of heterogeneity of the included studies, we cannot draw conclusions regarding which type of collagen and injection protocol is the best for the RCD treatment. Discussion: Collagen administration for RCD seem to be effective in reducing pain, improving function, as well as improving tendon structure, especially in partial tears and RC tendinopathy. High-quality and prospective long-term follow-up studies are needed to confirm the outcomes of the articles included in this systematic review.