MONTREAL — Results of a randomized, prospective study of patients undergoing single-level anterior lumbar interbody fusion showed that fusion rates were greater when titanium cages and threaded cortical bone dowels were used with recombinant human bone morphogenetic protein-2 instead of autogenous bone graft.
“The groups in which recombinant human bone morphogenetic protein-2 (BMP-2) was used with bone dowels and tapered cages showed faster clinical improvements and higher rates of fusion success than the autograft groups,” said J. Kenneth Burkus, MD, of The Hughston Clinic in Columbus, Ga. Burkus presented his results at the North American Spine Society 17th Annual Meeting, here.
The study, conducted at 22 U.S. investigational sites, assessed the efficacy of recombinant human bone morphogenetic protein-2 (BMP-2) on a collagen sponge, which is marketed as Infuse Bone Graft. In July, the Food and Drug Administration approved Infuse Bone Graft in conjunction with Medtronic Sofamor Danek’s tapered titanium LT-CAGE spine fusion cage for single-level lumbar fusions. The same cage was used in this study.
Three fusion devices implanted
The 387 patients enrolled in the non-blinded study had single-level symptomatic degenerative lumbar spondylosis. They were selected to undergo surgery because they did not respond to nonoperative treatment and underwent an open anterior lumbar interbody fusion. The interbody fusion was done using one of three devices: an impacted femoral ring allograft, a threaded cortical allograft bone dowel or the LT-CAGE device.
All 62 patients treated with femoral rings were also treated with autogenous bone graft. Forty-six patients received threaded bone dowels. They were randomized so that 24 patients received Infuse Bone Graft with the dowel and 22 patients received autogenous bone graft. The same randomization was done for the 279 patients treated with the LT-CAGE device. The cages used in 143 patients were filled with Infuse Bone Graft and subsequently implanted, whereas 136 patients received cages filled with autogenous bone graft.
Investigators assessed clinical outcomes using the Oswestry Low Back Disability Questionnaire at six, 12 and 24 months postop. Fusion was assessed at the same time points by two blinded radiologists using plain radiographs and computed tomography (CT) scans.
Looking at the overall Oswestry scores, “Impacted femoral ring allografts showed the least improvement among the three constructs. Tapered fusion cages generated and maintained the highest Oswestry improvements at all time points of the study,” Burkus said.
A higher percentage of patients treated with fusion cages also had 15-point improvements in their Oswestry scores. At 24 months postop, 84% of the bone dowel/BMP-2 and LT-CAGE patients had improved Oswestry scores of more than 15 points compared to 58% of patients in the bone dowel/autograft and femoral ring groups.
Infuse Bone Graft more greatly impacted clinical results in those patients who were treated with bone dowels. “Those patients in the bone dowel group who received BMP-2 exhibited statistically significant improvement in scores as compared to those who received autogenous grafts,” he said. Similar improvement in Oswestry scores was not seen when patients treated with BMP-2 in the bone dowel and cages groups were directly compared.
Clinical outcomes correlated closely with the fusion outcomes. At postop month six, more than 90% of patients in both LT-CAGE groups and the bone dowel/BMP-2 group had evidence of fusion. Fusion was evident in just 65% of patients in the bone dowel/autograft group (P=.067) and 10% in the femoral ring group.
“Femoral rings showed the lowest rates of fusion and poorest clinical outcomes,” he said. More than 94% of patients in the BMP-2-treated groups showed evidence of fusion at 24 months postop.
“The use of BMP-2 improves clinical outcomes and fusion rates in lumbar interbody fusion procedures over previous standard of care implants,” Burkus said. No adverse events occurred with the use of Infuse Bone Graft in this study.
Dr. Burkus is a paid consultant for Medtronic Sofamor Danek.For your information:
Burkus JK, Dorchak J. Comparison of impacted femoral ring allografts, threaded cortical bone dowels and titanium cages in lumbar fusion. Presented at the North American Spine Society 17th Annual Meeting. Oct. 29-Nov. 2, 2002. Montreal.