Prospective Analysis of Fusion Rate with a New Demineralized Bone Matrix

Abstract

Study background: Autologous Iliac Crest Bone Graft is considered the gold standard graft for use in instrumented spinal fusion procedures. Due to significant morbidity and complication rate, alternate graft materials have been investigated. This study seeks to determine the fusion rate of one such alternative, the K2M VESUVIUSTM Osteobiologic Fibers, a form of demineralized bone matrix. Methods: Prospectively collected CT scans of 27 patients with 29 instrumented levels were taken 1 year post-operatively. These were reviewed blindly by 5 fellowship trained spine surgeons to evaluate for fusion. The fusion mass was graded as no fusion (grade 1), partial unilateral (grade 2), partial bilateral (grade 3), solid unilateral (grade 4), or solid bilateral (grade 5). The fusion mass was then further classified as solid (grade 4-5), probable fusion (grade 3), or non-union (grade 1-2). The Kappa method was used to assess interrater reliability. We calculated the proportion of successful subjects at both cut-off values of either Grade 3 or Grade 4/5. Results: When using a cut-off grade of 3 or higher, 40% of subjects achieved fusion according to 4 of 5 graders and 50% achieved fusion according to 3 of the 5 graders. When using a cut-off grade of 4 or higher, 28% of subjects were found to achieve fusion by at least 4 graders and approximately 50% achieved fusion according to 3 of the graders. When analyzing correlation between the reviewers, 8 of 10 interrater reliabilities demonstrated moderate to good agreement. Correlation by grade showed that only grade 1 had significant agreement amongst the graders with a kappa value of 0.3394. Otherwise, the combined kappa value was 0.1092. Conclusion: Compared to the literature control using iliac crest bone autograft of 70.6% fusion rate, the results with K2M VESUVIUSTM Osteobiologic Fibers DBM were disappointing regardless of the cut off used.