LONG-TERM HEALING OF BONE USING RECOMBINANT HUMAN BONE MORPHOGENETIC PROTEIN-2

A 2.5-cm-long middiaphyseal plate-stabilized segmental defect in the r ight femora of 5 adult sheep was implanted with 1.5 mg of recombinant human bone morphogenetic protein 2 mixed with inactivated demineralize d ovine bone matrix, Bone healing was evaluated for 12 months using cl inical, radiographic, gross pathologic, and histologic techniques, Bon e formation within the defect was first visible radiographically betwe en Weeks 2 and 4 after surgery; bone union was apparent between Weeks 12 and 16, at which time the plates were removed, Recanalization of th e medullary cavity with neocortex formation was near completion at Wee k 52, Bone mineral content at the defect sites equaled that of the non surgically treated intact femora by Week 16, Perifemoral soft tissue m ineralization did not occur, and callus size was not greater than that formed with autograft, By Week 52, the sheep were not lame, and at ne cropsy the surgically treated femora were rigidly healed, Woven and la mellar bone bridged the defect site, An apparently normal sequence of ossification, modeling, and remodeling events had occurred, Recombinan t human bone morphogenetic protein 2 mixed with a suitable carrier cou ld provide an alternative to autograft for use in a variety of orthopa edic procedures.