Bone Graft Extenders: Any Evidence That They Work?
The widespread use of bone graft extenders (BGE) to improve fusion rates is an excellent example of the adoption of new technology in the absence of any high quality clinical data demonstrating their effectiveness. Given the widespread use of these products without any definitive RCT supporting this practice, Drs. Al Saleh and and his colleagues identified the topic as appropriate for systematic review. They identified 13 articles comparing fusion with osteoconductive BGEs (i.e. tricalcium phosphate, hydroxyapatite, calcium sulfate, etc.) with or without local bone or bone marrow aspirate to iliac crest autograft (ICBG). Further evaluation of these studies reveals a remarkable level of heterogeneity in terms of underlying diagnosis (scoliosis vs. degenerative), type of BGE used, the use of local bone, number of levels fused, and method of fusion evaluation. Keeping this heterogeneity in mind, the authors made an effort at meta-analysis that showed no significant differences in fusion rates or clinical outcome scores but a higher adverse event rate for the ICBG patients. Persistent ICBG pain was reported by 11% of patients across all the studies. Given these findings, this study suggests BGEs are not harmful and likely result in fusion rates similar to ICBG when used with local bone and instrumentation (no studies reported results for uninstrumented fusions).
Rather than yielding a result that should change clinical practice, this study should serve as the impetus for well-designed RCTs on this topic. There is now good evidence in the literature that the use of local bone for one and possibly two level instrumented fusions leads to similar fusion rates as ICBG. The important question that now needs to be addressed is whether or not adding osteoconductive BGEs or demineralized bone matrix (DBM) to local bone leads to higher fusion rates or better clinical outcomes compared to local bone alone. While the incidence and severity of ICBG donor site pain can be debated, it is difficult to argue that ICBG should be used instead of local bone if local bone results in a similar fusion rate. However, BGEs and DBM add substantial costs to the operation, and they should only be adopted if it can be shown that they result in a benefit that is measurable. A recent well-designed RCT compared fusion rates and clinical outcomes between one-level degenerative spondylolisthesis patients treated with decompression and fusion with either DBM and local bone or ICBG.1 A similar study comparing the addition of a BGE or DBM with local bone to local bone alone would be a good first step in evaluating these products. Such a study should be relatively simple to perform and should produce a clear result as to whether these products should be used for the most commonly encountered indication for lumbar fusion. The role of these products in more complex cases (i.e. multilevel fusions, revision cases with a lack of local bone, etc.) may never be clearly defined by Level 1 studies, but the spine community should be able to determine if their use is justified for one level posterolateral fusions.
Please read Dr. Wai’s article in the July 15 issue and the accompanying commentary. Will this article affect how you use BGEs in your practice? Let us know by leaving a comment on The Spine Blog.
Adam Pearson, MD, MS
Associate Web Editor
1. Kang J, An H, Hilibrand A, Yoon ST, Kavanagh E, Boden S. Grafton and local bone have comparable outcomes to iliac crest bone in instrumented single-level lumbar fusions. Spine 2012;37:1083-91.