The aim of this randomized control trial is to evaluate the impact and effectiveness of PRP on tenocyte metabolism and tendon tissue properties in rotator cuff tear.

The refractory to conservative treatment rotator cuff tears are mainly treated with arthroscopic repair. Intraoperative or postoperative platelet rich plasma (PRP) injections have been widely used to enhance the tendon healing and the repair process. Additionally, subacromial PRP injections are related to favorable outcomes in case of partial rotator cuff tears even one month after their application. Laboratory and clinical trials have correlated PRP with an increase in tenocyte metabolic activity, based on the up- or downregulation of specific gene expression.

Patients with rotator cuff tear who will be treated surgically will be included in the current study. After obtaining a signed consent form to participate in this trial, the patients will be randomly divided in two groups; the experimental group, where the PRP intervention will be applied, and the control group, where the patients will receive a placebo injection.

The included patients will undergo an ultrasound-assisted PRP or saline subacromial injection, four to six weeks prior to the scheduled surgery. During the arthroscopic rotator cuff repair procedure, a tendon biopsy will be performed and the sample will be sent for further analysis.

The samples will be sent for histologic analysis and quantification of specific gene expression. The gene analysis will contain the collagen I, collagen III, metalloproteinase 3 and metalloproteinase 13 genes, which are related to tendon repair and remodeling in cases of rupture and/or injury. Furthermore, the two groups will be compared in terms of the MRI imaging findings. After statistical analysis, a conclusion regarding the effect of PRP on the enhancement of biological properties of the ruptured tendon and, consecutively, tendon healing process will be extracted.

Inclusion Criteria:

• Full thickness rotator cuff tear treated with arthroscopic repair
• Age of 18 to 65 years
• Chronic shoulder pain due to rotator cuff tear
• Magnetic resonance imaging study within 6 months prior to arthroscopy
• Goutallier grade 1 or 2 muscle fatty infiltration

Exclusion Criteria:

• Comorbidities, including coagulopathy, liver disease, cancer, nutritional disorder
• Goutallier grade 3 or 4 muscle fatty infiltration
• Shoulder osteoarthritis, rotator cuff arthropathy, rheumatoid arthritis
• History oof shoulder injection within the last 12 months
• History of prior shoulder surgery

After the collection and statistical analysis of the results of this clinical trial, the data will be published in scientific or medical journals.

After data collection and statistical analysis. Within three years from the beginning of this study and will be available for 6 months after publication.

Every individual who has access to ClinicalTrials.gov will have permission to requests the available data. The permission will be given by one of the investigators of this clinical trial.