Title Freeze-Dried Chitosan-Thrombin-Platelet-Rich Plasma Implants Improve Supraspinatus Tendon Regeneration in a Rabbit Rotator Cuff Repair Model

Rotator cuff tears stand as the most prevalent shoulder condition prompting medical intervention. Failure rates as high as 60% have been reported after surgery, indicating the need for improved treatments. The aim of this study was to confirm whether an implant composed of freeze-dried chitosan and thrombin rehydrated in autologous platelet-rich plasma (CS-FIIa-PRP) is effective in improving supraspinatus tendon regeneration in a New Zealand white rabbit model. Complete tears of the supraspinatus tendon were created bilaterally, then repaired using transosseous sutures. On the treated shoulder, CS-FIIa-PRP implants were injected both in the transosseous tunnels and on the tendon at the repaired site. Animals were sacrificed after 1 day (<i>n</i> = 1), 2 weeks (<i>n</i> = 6), 4 weeks (<i>n</i> = 6), and 3 months (<i>n</i> = 6). CS-FIIa-PRP implants were observed in the tunnels and on the tendon surface up to 4 weeks postsurgery and did not induce any deleterious effects. Using those implants in addition to sutures improved the macroscopic attachment of tendon to the humeral head at early time points (2 and 4 weeks), led to a faster improvement of the tendons' mechanical properties (<i>p</i> < 0.05), and inhibited the development of heterotopic ossification (<i>p</i> < 0.01). Rotator cuff regeneration using CS-FIIa-PRP implants is, therefore, a promising treatment for rotator cuff defects when combined with sutures.