Background: Large amounts of bone graft are
frequently used to elicit the healing of bone defects resulting
from reconstructive procedures. Autograft and allograft bone are
often used, but each has its limitations. Bone morphogenetic proteins
(BMPs) improve the healing of segmental bone defects treated 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 collagen (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 defects was assessed with radiographic, biomechanical,
and histological studies. The animals were killed at twelve weeks
Results: The use of the OP-1 device alone or any
combination of autograft or allograft bone and the OP-1 device demonstrated
improved healing on radiographic, mechanical, and histological studies
compared with that demonstrated 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 device.
At twelve weeks postoperatively, 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 associated 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 study.
Clinical Relevance: The combination of freeze-dried
allograft bone with the OP-1 device is an attractive graft material for
the treatment of large bone defects. Although similar results were
observed when autogenous bone graft was used in combination with
the OP-1 device, the results of the present study suggest that allograft,
because of its relatively unlimited supply, can be substituted without
reduced efficacy. In addition, avoiding the need to harvest autogenous bone
eliminates the additional operative time and risk associated with
a second surgical procedure.