OP-1 for cervical spine fusion - Bridging bone in only 1 of 4 rheumatoid patients but prednisolone did not inhibit bone induction in rats

We used OP-1 (also called BMP-7) on a collagen type-1 carrier in atlanto-ax ial posterior fusions to promote bony healing after wire fixation. 4 patien ts who had instability between the atlas and axis due to rheumatoid disease received the implants. The patients were examined with conventional radiog raphy postoperatively at 2, 6 and 10 months. In 3 patients, no new bone for mation was detectable. In 1 patient, new bone bridged the fusion site at 6 months. 3 patients were on chronic steroid treatment, including the patient in whom bone formation was detected. To determine whether steroid treatmen t could be responsible for the low rate of bone induction, 24 rats each rec eived OP-1 implants in an abdominal muscle pouch. They were divided into 3 groups receiving saline, 0.1 or 1.0 mg/kg BW of prednisolone daily until th ey were killed 3 weeks postoperatively. Specimens were decalcified for hist ology and the amount of calcium in the decalcifying solution was measured. All groups showed ossicles induced by OP-1, and no effect of prednisolone w as detected. Thus the failures in the patients may have causes other than p rednisolone treatment.