Collagen and platelet-rich plasma in partial-thickness rotator cuff injuries. Friends or only indifferent neighbours? Randomised controlled trial

BACKGROUND: Partial-thickness rotator cuff injuries (PTRCI) are the sum of degenerative, overload, and microtrauma processes. An external supply of collagen and platelet-rich plasma (PRP) could potentially counteract the deterioration of degenerative tendinopathy. This study aimed to compare the effectiveness of collagen with PRP, PRP alone, and collagen alone in the treatment of PTRCI. METHODS: Ninety patients with PTRCI were randomised and treated with ultrasound-guided injections into the shoulder bursa every consecutive week: Group A – collagen with PRP (n = 30), Group B – collagen alone (n = 30), and Group C – PRP alone (n = 30). Primary outcomes were pain intensity measured in control points on a numeric rating scale (NRS), QuickDash, and EQ-5D-5L questionnaires at the initial assessment (IA) and control assessments after 6 (T1), 12 (T2), and 24 (T3) weeks, respectively. RESULTS: No statistical differences were found between groups in primary outcomes, although there was a trend towards improvement in Groups A and C (opposite to Group B) between T2 and T3. The following parameters were also observed: rotator cuff discontinuity (n = 3, one case in each group) and rotator cuff regeneration (n = 22 in Group A, n = 20 in Group B, and n = 23 in Group C). CONCLUSIONS: Combined therapy of collagen and PRP in PTRCI presents similar effectiveness to monotherapies with collagen or PRP. TRIAL REGISTRATION: The study was prospectively registered on the NCT Trial Center (identification number: NCT04492748) on 30.07.2020.