Clinical StudyAccelerating lumbar fusions by combining rhBMP-2 with allograft bone: a prospective analysis of interbody fusion rates and clinical outcomes
Introduction
Recombinant human bone morphogenetic protein-2, rhBMP-2, (InFuse Bone Graft; Medtronic Sofamor Danek, Memphis, TN) is an osteoinductive protein approved for use in the anterior lumbar interspace. Summary analysis of prospective studies has shown that the rhBMP-2 placed within two titanium interbody cages is superior to autograft in obtaining fusion success [1], [2], [3]. Ongoing clinical research is encouraging, and expectations for continued success with BMP remain high [4], [5], [6], [7].
Successful interbody fusions with rhBMP-2 have been reported with threaded, allograft bone dowels [8], [9]. Allograft bone is commonly used as structural interbody graft in the lumbar spine, but fusion rates vary widely and time to incorporation is often prolonged. An advantage of using allograft is that it can be visualized on computed tomographic (CT) scans or radiographs without metal artifact. This allows for more direct and accurate fusion assessment using these readily available radiographic tests [10].
Anterior lumbar interbody fusions (ALIF) are an effective treatment option for symptomatic lumbar disc disease [2], [3], [11], [12], [13], [14], [15], [16], [17], [18]. “Stand-alone” grafts (no pedicle screw instrumentation) have been associated with high rates of pseudarthrosis and clinical failure [13], [18], [19], [20]. Even with the addition of rhBMP-2, stand-alone femoral allograft interbody constructs are not mechanically stable enough to heal reliably [21].
The emergence of rhBMP-2 as a viable alternative to traditional bone grafting is based on two important clinical challenges [7]. The first is to eliminate the need to harvest bone from the iliac crest or other sites when performing a spinal fusion. There is increased pain and morbidity in these operative procedures. The second reason is to try to eliminate or greatly reduce the number of nonunions observed in reconstructive spinal surgeries.
There are extensive data published on the results of lumbar fusions with anterior allograft stabilized with pedicle screw fixation [11], [13], [15], [22]. Although the results of these techniques are generally good, there are still a significant number of failures. Concerning issues with allograft fusions include prolonged time to heal, incomplete graft incorporation, and mechanical failure [20], [23], [24], [25].
As BMP is osteoinductive and allograft bone is osteoconductive, it is logical to combine the two in an effort to improve the reliability and rapidity of a lumbar arthrodesis. Based on the very high fusion rates noted with rhBMP-2, the authors began placing two sponges of rhBMP-2 (InFuse Bone Graft) inside the center of allograft femoral rings in a small number of ALIF cases. We observed rapid incorporation of the grafts with no untoward effects. A formal prospective analysis was therefore initiated. The purpose of this study is to determine if rhBMP-2 will safely accelerate allograft interbody fusions, as compared with allograft alone, and significantly reduce the number of pseudarthrosis.
Section snippets
Methods
A prospective, single-center study of patients undergoing arthrodesis at 1–3 levels of the lumbar spine was conducted with institutional review board approval from September 2002 to July 2004. Group 1 (control) consisted of 30 patients enrolled consecutively. The next 45 patients were then enrolled successively, comprising Group 2 (investigational).
Results
Both groups were similar in demographics including diagnosis, number of levels fused, smoking status, and worker's compensation status (Table 2). At 6 months no patients were lost to follow-up. At 12 months one patient (control group) was lost to follow-up, and at 24 months two additional patients (investigational group) were lost to follow-up.
There were no complications attributable to the use of rhBMP-2. Group 1 had one superficial (anterior) wound dehiscence that granulated closed with local
Discussion
Short- and long-term morbidity associated with graft harvest is of great concern to patients contemplating spinal fusion surgery. Sparing the patient the pain and morbidity of iliac crest harvest is of paramount importance. Published data support the anecdotal observations of patients that residual pain at the donor site is disabling [28], [29], [30]. In order to advance the progress of orthopedic surgery, scientists and surgeons have strived to eliminate the need to harvest bone graft from the
Conclusions
Our study confirms the efficacy of an innovative lumbar fusion technique: an interbody femoral ring allograft, combined with an osteoinductive stimulant (rhBMP-2), protected by pedicle screws. This combination of a structural interbody allograft with rhBMP-2 eliminates the insult of iliac crest harvest, allows for reliable radiographic analysis, and results in successful fusion formation in 100% of the cases in this study.
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2021, Journal of Orthopaedic TranslationrhBMP in lumber fusion for lumbar spondylolisthesis: A systematic review and meta-analysis
2019, Chinese Journal of Traumatology - English EditionCitation Excerpt :In 2002, the US Food and Drug Administration approved the rhBMP-2/absorbable collagen sponge (ACS)/vertebral fusion device for anterior lumbar fusion.38 Slosar et al.39 reported that rhBMP-2 composite allogeneic bone was used in 45 patients with anterior lumbar interbody fusion for 2 years, there were no complications in the rhBMP group, no revision surgery, and 4 patients in the control group underwent revision surgery. Therefore, we analyzed the adverse effects across two groups.
FDA device/drug status: approved but not for this indication (rhBMP-2).
This research was supported by a grant from Medtronic Sofamor Danek. Authors PJS and JR acknowledge a financial relationship (consultant with Medtronic Sofamor Danek) that may indirectly relate to the subject of this research.