Biphasic Interpositional Allograft for Rotator Cuff Repair Augmentation Is Safe in an Ovine Model

Abstract

This study is a preclinical histological assessment of a biphasic acellular interpositional cancellous allograft in an ovine model of rotator cuff repair (RCR) designed to better understand its safety profile and effects on tendon healing after rotator cuff repair. Thirty skeletally mature sheep with clinically normal shoulders with an artificially created degenerative infraspinatus tendon (IST) tear were randomized to control and treatment groups. Animals were euthanized at 3-weeks, 6-weeks, and 12-weeks. After gross dissection, rotator cuff specimens were fixed with formalin and polymerized for sectioning and staining. Blinded histological scores evaluated inflammatory cell infiltrates, signs of degradation, particulate debris, collagen arrangement, neo-vascularization, and enthesis qualitative measures. There were no treatment specimens that exhibited histological signs of a significant infection, inflammatory infiltrate, or foreign body reaction such as granuloma or fibrous capsule formation. Histological scores in all categories were not significantly different at all time points, including the primary endpoint mean cumulative inflammatory score (control: 3.66 ± 1.21 versus treated: 4.33 ± 1.51, p = 0.42), when comparing the treatment and control RCR groups. In general, the degree of tendon healing and host tissue response was essentially equivalent between the two groups with observation of low overall levels of inflammation and progressive improvements in collagen organization, reduced tenocyte activity, and fibrocartilaginous enthesis reformation. This histological study demonstrated the use of a biphasic interpositional allograft for rotator cuff repair augmentation in an ovine model does not generate an inflammatory response or foreign body reaction. Use of the biphasic interpositional allograft resulted in a histological profile that was essentially equivalent to that of a standard RCR at 3-, 6-, and 12-week post-operative timepoints. These findings suggest that a biphasic interpositional allograft is safe for further clinical investigation in humans before broader clinical application. Patch augmentation of RCR is a popular technique that has shown clinical success in improving the likelihood of a successful repair in patients at elevated risk for retear. Newer augmentation technologies are being developed to address the biology at the interface between the bone and soft tissue where failure typically occurs.