Posterior lumbar interbody fusion using recombinant human bone morphogenetic protein type 2 with cylindrical interbody cages

In a large series of human patients undergoing open anterior lumbar interbody fusion with a tapered titanium fusion cage, recombinant human bone morphogenetic protein type 2 (rhBMP-2) on an absorbable collagen sponge carrier has been shown to decrease operative time and blood loss, to promote osteoinduction and fusion and to be a safe and effective substitute for iliac crest harvesting. The purpose of the study was to determine the clinical and radiographic outcomes in patients treated for single-level degenerative lumbar disc disease with a posterior interbody fusion, using stand-alone cylindrical threaded titanium fusion cages with either autogenous bone graft or rhBMP-2 and an absorbable collagen sponge carrier. A prospective, randomized, nonblinded, 2-year pilot study at 14 investigational sites. Between March 1999 and December 1999, 67 patients with symptomatic, single-level degenerative lumbar disc disease of at least 6 months' duration underwent a single-level posterior lumbar interbody fusion using two paired cylindrical threaded titanium fusion devices. Patients were randomly assigned to one of two groups: one (n=34 patients) received rhBMP-2 on a collagen sponge carrier; the other (n=33 patients) autogenous iliac crest bone graft. Clinical outcomes were measured using low back and leg pain numerical rating scales, the Short Form (SF)–36, Oswestry Low Back Pain Disability Questionnaire and work status. Plain radiographs and computed tomographic scans were used to evaluate fusion at 6, 12 and 24 months after surgery. In this prospective nonblinded study, 67 patients were randomly assigned to one of two groups who underwent interbody fusion using two cylindrical threaded fusion cages: the investigational group (34 patients), who received rhBMP-2 on an absorbable collagen sponge, and a control group (33 patients), who received autogenous iliac crest bone graft. Clinical data were collected and analyzed by a commercial entity. The mean operative time and blood loss for the investigational rhBMP-2 group was 2.6 hours and 322.8 ml, respectively. For the autograft control group, these values were 3.0 hours and 372.7 ml. The differences were not significant. Although not statistically different, at 24 months, the investigational group's fusion rate of 92.3% was higher than the control's at 77.8%. At all postoperative intervals, the mean Oswestry, back and leg pain scores and physical components of the SF-36 improved in both treatment groups compared with