Methods: Eighteen canines had surgical transection and xenograft graft-augmented repair of the Achilles tendon. Nine dogs were studied for 6 weeks and 9 for 12 weeks. For each time period, 3 dogs received a non-cross-linked porcine dermal graft (BIOTAPE XM™, Wright Medical Technology); 3 received a multi-layered porcine small intestine submucosa graft (Restore® Orthobiologic Soft Tissue Implant, DePuy); and 3 dogs received a cross-linked equine pericardium graft (OrthADAPT™ FX Bioimplant, Pegasus Biologics). At the end of the study periods, cellular and vascular infiltration, graft incorporation, remodeling of the grafts, and inflammation were characterized from serial histological sections.

Results: There were distinct differences among the 3 grafts with regard to the degree of inflammation, incorporation by the host, and remodeling and replacement of the implanted collagen matrices. Most of the porcine dermal graft was still evident surrounding the tendon. It was substantially repopulated with fibroblasts and blood vessels, and there were focal sites of incorporation of the graft into tendon. In contrast, only scant remnants of the porcine small intestine submucosa graft remained at 6 and 12 weeks, except for a layer of fibrous tissue surrounding the tendon and foci of inflammatory cells. The cross-linked equine pericardium graft demonstrated a pronounced foreign-body response and little incorporation by host tissue.

Conclusions: The 3 xenografts demonstrated marked differences in rates of remodeling and replacement and the nature and degree of inflammatory response, although clinically, a similar functional result was obtained. The durability and biocompatibility of the porcine dermal graft may be important for continued augmentation of the injured site until complete tendon healing and function is achieved.