Atelocollagen Injection Improves Tendon Integrity in Partial-Thickness Rotator Cuff Tears: A Prospective Comparative Study

Background: Ongoing controversy surrounds the best treatment modality for partial-thickness rotator cuff tears.Purpose: To investigate the effects of atelocollagen injection in patients with small, symptomatic, intratendinous rotator cuff tears.Study Design: Randomized controlled trial; Level of evidence, 1.Methods: From January 2014 to December 2017, 94 patients who had small, symptomatic, intratendinous rotator cuff tears were enrolled and randomly allocated to 1 of 3 groups: intratendinous injection with 0.5 mL of type I atelocollagen (group 1, n = 32), intratendinous injection with 1 mL of type I atelocollagen (group 2, n = 30), and no injection of type I atelocollagen (group 3, n = 32). American Shoulder and Elbow Surgeons score, Constant Shoulder Score, visual analog scale pain score, and range of motion were evaluated before injection; at 3, 6, and 12 months after injection; and at final follow-up. Magnetic resonance imaging (MRI) was performed at least 6 months after injection to evaluate rotator cuff integrity.Results: Demographic data did not differ significantly among the 3 groups before injection ( P > .05). The mean follow-up period was 24.7 months. The functional and pain scores in groups 1 and 2 were significantly improved at final follow-up ( P < .05). No significant improvement was seen in functional or pain scores at final follow-up in group 3 ( P > .05). Groups 1 and 2 had significantly better functional scores compared with group 3 at final follow-up ( P < .05). The proportion of patients with a decrease in size of the torn tendon on follow-up MRI at least 6 months after atelocollagen injection was significantly higher in group 1 (28.1%; P = .02) and group 2 (36.7%; P = .003) compared with group 3 (6.3%).Conclusion: Atelocollagen injection can improve the functional outcome and integrity of the tendon in intratendinous rotator cuff tears.