Chitosan-platelet-rich plasma implants improve rotator cuff repair in a large animal model: Pilot study

Freeze-dried formulations of chitosan can be solubilized in platelet-rich plasma (PRP) to form injectable implants that are used as an adjunct treatment during surgical repair of the rotator cuff. The purpose of the current study was to assess chitosan-PRP implant residency, test safety, and assess efficacy over standard-of-care controls in a sheep model of rotator cuff repair. The infraspinatus tendon was transected unilaterally and immediately repaired with suture anchors in 22 skeletally mature ewes. In treatment groups, formulations containing chitosan, trehalose, and calcium chloride were solubilized with autologous leukocyte-rich PRP and injected at the tendon-bone interface and on top of the repaired site (1 mL or 2 mL doses). Implant residency was assessed histologically at 1 day. Outcome measures included MRI assessment at baseline, 6 weeks, and 12 weeks, histopathology and clinical pathology. Chitosan-PRP implants were resident at the injection site at 1 day and induced recruitment of polymorphonuclear cells. The tendon gap, which corresponds to the length of abnormally hyperintense tissue attached to the humeral head, was decreased by treatment with the 2 mL dose when compared to controls at 12 weeks on MRI images. Some histological features were improved by the 2 mL dose treatment compared to controls at 12 weeks. There was no treatment-specific effect on all standard safety outcome measures, which suggests high safety. This study provides preliminary evidence on the safety and efficacy of chitosan-PRP implants in a large animal model that could potentially be translated to a clinical setting.