The effect of osteogenic protein-1 on the healing of segmental bone defects treated with autograft or allograft bone

Background: Large amounts of bone graft are frequently used to elicit the h ealing of bone defects resulting from reconstructive procedures. Autograft and allograft bone are often used, but each has its limitations. Bone morph ogenetic proteins (BMPs) improve the healing of segmental bone defects trea ted with autograft or allograft. The objective of the present study was to determine the effect of implantation of a recombinant osteogenic protein-1 (OP-1) in combination with bone graft on the healing of a critical-sized (2 .5-cm) segmental defect in canine ulnae. Methods: Either autograft bone, allograft bone, osteogenic protein-1 (OP-1) mixed with type-1 bovine collagen, or various combinations of OP-1 and col lagen (OP-1 device) mixed with allograft or autograft were implanted in the segmental bone defects. The combinations included 67% bone graft with 33% OP-1 device and 33% bone graft with 67% OP-1 device. The healing of the def ects was assessed with radiographic, biomechanical, and histological studie s. The animals were killed at twelve weeks postoperatively. Results: The use of the OP-1 device alone or any combination of autograft o r allograft bone and the OP-1 device demonstrated improved healing on radio graphic, mechanical, and histological studies compared with that demonstrat ed after use of autograft or allograft bone alone. The highest radiographic and histological grades and the greatest mechanical strength were achieved with the use of 33% allograft and 67% OP-1 device although no significant differences were observed among the different groups containing the OP-1 de vice. At twelve weeks post operatively, the defects treated with any amount of the OP-1 device obtained greater mechanical strength than that obtained by autograft bone alone. Conclusions: Major bone defects may be treated with allograft bone combined with the OP-1 device, instead of autograft alone, to avoid complications a ssociated with the use of autograft. The combination of allograft bone and the OP-1 device resulted in optimum healing of the defect, according to the radiographic, mechanical, and histological parameters measured in this stu dy. Clinical Relevance: The combination of freeze-dried allograft bone with the OP-1 device is an attractive graft material for the treatment of large bon e defects. Although similar results were observed when autogenous bone graf t was used in combination with the OP-1 device, the results of the present study suggest that allograft, because of its relatively unlimited supply, c an be substituted without reduced efficacy. In addition, avoiding the need to harvest autogenous bone eliminates the additional operative time and ris k associated with a second surgical procedure.