Bone substitutes and expanders in Spine Surgery: A review of their fusion efficacies

Abstract

Study Design A narrative review of literature. ObjectiveThis manuscript intends to provide a review of clinically relevant bone substitutes and bone expanders for spinal surgery in terms of efficacy and associated clinical outcomes, as reported in contemporary spine literature. Summary of Background DataEver since the introduction of allograft as a substitute for autologous bone in spinal surgery, a sea of literature has surfaced, evaluating both established and newly emerging fusion alternatives. An understanding of the available fusion options and an organized evidence-based approach to their use in spine surgery is essential for achieving optimal results. MethodsA Medline search of English language literature published through March 2016 discussing bone graft substitutes and fusion extenders was performed. All clinical studies reporting radiological and/or patient outcomes following the use of bone substitutes were reviewed under the broad categories of Allografts, Demineralized Bone Matrices (DBM), Ceramics, Bone Morphogenic proteins (BMPs), Autologous growth factors (AGFs), Stem cell products and Synthetic Peptides. These were further grouped depending on their application in lumbar and cervical spine surgeries, deformity correction or other miscellaneous procedures viz. trauma, infection or tumors; wherever data was forthcoming. Studies in animal populations and experimental in vitro studies were excluded. Primary endpoints were radiological fusion rates and successful clinical outcomes. ResultsA total of 181 clinical studies were found suitable to be included in the review. More than a third of the published articles (62 studies, 34.25%) focused on BMP. Ceramics (40 studies) and Allografts (39 studies) were the other two highly published groups of bone substitutes. Highest radiographic fusion rates were observed with BMPs, followed by allograft and DBM. There were no significant differences in the reported clinical outcomes across all classes of bone substitutes. ConclusionsThere is a clear publication bias in the literature, mostly favoring BMP. Based on the available data, BMP is however associated with the highest radiographic fusion rate. Allograft is also very well corroborated in the literature. The use of DBM as a bone expander to augment autograft is supported, especially in the lumbar spine. Ceramics are also utilized as bone graft extenders and results are generally supportive, although limited. The use of autologous growth factors is not substantiated at this time. Cell matrix or stem cell-based products and the synthetic peptides have inadequate data. More comparative studies are needed to evaluate the efficacy of bone graft substitutes overall.keywords: bone substitutes, allografts, demineralized bone matrix (dbm), spine fusion, ceramics, β tricalcium phosphate (β-tcp), hydroxyapatite, rhbmp-2, osteogenic protein-1 (op-1), autologous growth factors, i-factor, synthetic peptides volume 10 article 33

Comparative Efficacy of Commonly Available Human Bone Graft Substitutes as Tested for Posterolateral Fusion in an Athymic Rat Model

“…Future testing of combinations such as these may reveal synergies not apparent on the single material experiment presented here. However, the results of this study help to address the paucity of clinical data 82 and preclinical data to support decisions on selection of individual grafting materials to optimize bone healing in spinal fusion.…”

Biphasic calcium phosphate with submicron surface topography in an Ovine model of instrumented posterolateral spinal fusion

“…In comparison to previous studies, which show either an inferiority of calcium phosphates compared to autograft or equivalence evidenced through weaker endpoints, we demonstrate equivalent performance of AG, BCP granules and BCP putty by an array of strong assessment methods. In clinical literature, we can find conflicting evidence about the efficacy of calcium phosphate materials as bone graft materials for spine fusion . Physicochemical properties of biomaterials are rarely discussed in clinical literature and it is often overlooked that these properties strongly influence the performance of calcium phosphate bone graft materials.…”

“…Symbols: * P < 0.01; ** P < 0.001; # all significantly different from 6 weeks, P < 0.001; † all significantly different from 12 weeks and 6 weeks, P < 0.001; ‡ significantly different from BCP granules , 6 weeks, P < 0.01; • significantly different from BCP granules , 26 weeks, P < 0.05 evidence about the efficacy of calcium phosphate materials as bone graft materials for spine fusion. 36,37 Physicochemical properties of biomaterials are rarely discussed in clinical literature and it is often overlooked that these properties strongly influence the performance of calcium phosphate bone graft materials. Indeed, during preclinical in vivo studies, grafts with optimized physicochemical properties have presented better outcomes than those with suboptimal properties.…”

In-vivo Performance of Seven Commercially Available Demineralized Bone Matrix Fiber and Putty Products in a Rat Posterolateral Fusion Model

“…Clinical studies have reported the safety and efficacy of DBM as a bone graft extender in lumbar spine fusion (5)(6)(7)(8). One study in 120 patients undergoing 1-2 level instrumented posterolateral fusion (PLF) used a DBM gel (Grafton R ) mixed with local autograft bone implanted on one side, compared to iliac crest autograft implanted on the contralateral side in the same patient (9).…”