Healing of transverse humeral fractures in pigeons treated with ethylene oxide-sterilized, dry-stored, onlay cortical xenografts and allografts

Transverse humeral fractures were created in adult male pigeons (Columbia livia). They were bridged with an allograft or a xenograft, or they were allowed to heal without treatment. Tissues were examined for wound healing, bony union, infection, and sequestration of the graft at 28, 43, 85, 106, and 168 days after surgery. Neither allografts nor xenografts contributed to nor interfered with bone healing. In nontreated pigeons (controls), bony union with marked callus formation developed between misaligned fragment ends. When onlay grafts were used, bone fragments remained aligned, with minor callus formation. There was a significant (P = 0.0001) increase in the number of wounds opening after surgery and infections of the surgical site (xenograft, P = 0.0026; allograft, P = 0.0021) associated with graft use. A significant (P = 0.0001) frequency of graft sequestration was observed, regardless of graft type. A significant (P = 0.0001) frequency of foreign body reaction also was observed. Under these circumstances, the application of a graft should be considered as an alignment device, rather than a stimulus to healing.