Posterolateral intertransverse process spinal arthrodesis with rhBMP-2 in a nonhuman primate: Important lessons learned regarding dose, carrier, and safety

Recombinant osteoinductive proteins have been used successfully in canine a nd rabbit models of posterolateral intertransverse process arthrodesis, but little is known about the ability of these compounds to achieve fusion in nonhuman primates. The goals of this investigation were to compare differen t combinations of recombinant human bone morphogenetic protein-2 (rhBMP-2) dosages and carriers in a nonhuman primate model of posterolateral intertra nsverse process spinal fusion and to determine the feasibility of using rhB MP-2 in the presence of exposed dura in a laminectomy model. Posterolateral inter-transverse process arthrodeses were performed at L4-5 in 29 rhesus m onkeys. The most striking findings were as follows: rhBMP-2 could induce bo ne in a nonhuman primate spine; the presence of a laminectomy defect with e xposed dura did not preclude the safe use of rhBMP-2 for posterolateral fus ion; soft tissue compression of the collagen sponge carrier prevented bone induction at standard BMP doses, presumably due to squeezing of the protein out of the sponge; and longer rhBMP-2 loading time into the collagen carri er and mechanical protection from the soft tissue compression both allowed more bone induction at a lower dose of rhBMP-2.