Background:It is unclear how and which factors affect the clinical efficacy of platelet-rich plasma (PRP) applied during arthroscopic rotator cuff repair.Purpose:To evaluate the clinical efficacy of PRP for arthroscopic repair of full-thickness rotator cuff tear and investigate the factors that affect its clinical efficacy.Study Design:Systematic review; Level of evidence, 1.Methods:We searched Cochrane Library, EMBASE, MEDLINE, and OVID to identify randomized controlled trials (RCTs) of patients who received PRP treatment and arthroscopic rotator cuff repair (PRP group) versus controls (no-PRP group). The primary outcomes included retear rate, Constant-Murley score, University of California Los Angeles (UCLA) score, short-term American Shoulder and Elbow Surgeons (ASES) score, visual analog scale (VAS) score for pain, and adverse events.Results:A total of 14 RCTs were included in this systematic review. Significant improvement in Constant-Murley, UCLA, and VAS pain scores were found in the PRP group during short-term, midterm, and long-term follow-up. The PRP group had a significantly decreased retear rate (risk ratio [RR], 0.57 [95% CI, 0.42 to 0.78]; P = .0003), especially for long-term follow-up (RR, 0.38 [95% CI, 0.17 to 0.83]; P = .02), large to massive tears (RR, 0.58 [95% CI, 0.42 to 0.80]; P = .0008), use of leukocyte-poor PRP (RR, 0.50 [95% CI, 0.33 to 0.76]; P = .001), and intraoperative application of PRP (RR, 0.57 [95% CI, 0.42 to 0.79]; P = .0007). No significant difference between the 2 groups was found in the incidence of adverse events (RR, 1.34 [95% CI, 0.83 to 2.15]; P = .23) or in ASES scores at short-term follow-up (weighted mean difference, 1.04 [95% CI, –3.10 to 5.19]; P = .62).Conclusion:The results of this review indicated that arthroscopic rotator cuff repair with PRP significantly reduced the long-term retear rate and shoulder pain and provided improved long-term shoulder function in patients. Intraoperative application of PRP, use of leukocyte-poor plasma, and large to massive tear size contributed to a significantly decreased retear rate for rotator cuff repair combined with PRP.