Use of recombinant human bone morphogenetic protein-2 as an adjunct in posterolateral lumbar spine fusion - A prospective CT-scan analysis at one and two years

Introduction: This study determines whether recombinant human bone morphogenetic protein-2 (rhBMP-2) (12 mg at the rate of 1.5 mg/mL) delivered on an absorbable collagen sponge with an added bulking agent can increase posterolateral lumbar spine fusion success rates and decrease time for fusion with autogenous bone grafts. Method: A prospective, single institution, clinical case-matched, radiographic, cohort study was undertaken. A total of 52 patients underwent posterolateral lumbar arthrodesis with pedicle screw instrumentation. The experimental group (n = 41) underwent placement of Iliac crest bone graft (ICBG) with InFUSE (12 mg/level at the rate of 1.5 mg/mL). The control group (n = 11) consisted of sex-matched patients, consecutively collected over the same time period with an instrumented posterolateral arthrodesis and ICBG placed in the intertransverse space. Outcome Measures: Thin-cut (2 mm) axial, coronal, and sagittal reconstructions were blindly evaluated for evidence of bridging bone and cortication of the fusion mass by 3 separate reviewers. Fusions were graded and an overall score was given to the quality of the fusion mass. Results: Fifty patients (ICBG alone n = 11; ICBG/rhBMP-2 n = 39) were available for CT evaluation at 2-year follow-up. An overall 97% (68/70 levels; Definite + Probably Fused) fusion rate in the rhBMP-2 group was achieved as compared to the 77% fusion rate (17/22 levels) in the ICBG alone group (P < 0.05). In the rhBMP-2 group, 92% of the patients (36/39 patients) received an overall excellent subjective fusion rating as compared to 27% (3/11) in the control group (P < 0.05). There was no computed tomographic evidence of soft-tissue ossification, dural ossification, or laminar bone regrowth in any patient. Conclusions: The adjunctive use of rhBMP-2 and ICBG seems to be safe and results in significantly larger and more consistent posterolateral fusion masses.