The role of Osteocel Plus as a fusion substrate in minimally invasive instrumented transforaminal lumbar interbody fusion

A comprehensive systematic review of marketed bone grafts for load-bearing critical-sized bone defects

Treatment of critical-sized bone defects typically involves implantation of a bone graft. Various types of bone grafts are nowadays marketed, categorized by their origin as allografts, xenografts, or synthetic grafts. Despite their widespread use, a comprehensive understanding of their morphology and mechanical response remains elusive. Controlling these characteristics for promoting bone growth and ensuring mechanical resistance remains challenging, especially in load-bearing districts. This study aims to systematically review existing literature to delineate the principal morpho-mechanical characteristics of marketed bone grafts designed for load-bearing applications. Furthermore, the obtained data are organized and deeply discussed to find out the relationship between different graft characteristics. Among 196 documents identified through PRISMA guidelines, encompassing scientific papers and 510(k) documents, it was observed that a majority of marketed bone grafts exhibited porosity akin to bone (>60%) and mechanical properties resembling those of low-bone volume fraction trabecular bone. The present review underscores the dearth of information regarding the morpho-mechanical characteristics of bone grafts and the incomparability of data derived from different studies, due to the absence of suitable standards and guidelines. The need for new standards and complete and transparent morpho-mechanical characterization of marketed bone grafts is finally emphasized. Such an approach would enhance the comparability of data, aiding surgeons in selecting the optimal device to meet patient's needs.

Advances in implants and bone graft types for lumbar spinal fusion surgery

The increasing prevalence of spinal disorders worldwide necessitates advanced treatments, particularly interbody fusion for severe cases that are unresponsive to non-surgical interventions. This procedure, especially 360° lumbar interbody fusion, employs an interbody cage, pedicle screw-and-rod instrumentation, and autologous bone graft (ABG) to enhance spinal stability and promote fusion. Despite significant advancements, a persistent 10% incidence of non-union continues to result in compromised patient outcomes and escalated healthcare costs. Innovations in lumbar stabilisation seek to mimic the properties of natural bone, with evolving implant materials like titanium (Ti) and polyetheretherketone (PEEK) and their composites offering new prospects. Additionally, biomimetic cages featuring precisely engineered porosities and interconnectivity have gained traction, as they enhance osteogenic differentiation, support osteogenesis, and alleviate stress-shielding. However, the limitations of ABG, such as harvesting morbidities and limited fusion capacity, have spurred the exploration of sophisticated solutions involving advanced bone graft substitutes. Currently, demineralised bone matrix and ceramics are in clinical use, forming the basis for future investigations into novel bone graft substitutes. Bioglass, a promising newcomer, is under investigation despite its observed rapid absorption and the potential for foreign body reactions in preclinical studies. Its clinical applicability remains under scrutiny, with ongoing research addressing challenges related to burst release and appropriate dosing. Conversely, the well-documented favourable osteogenic potential of growth factors remains encouraging, with current efforts focused on modulating their release dynamics to minimise complications. In this evidence-based narrative review, we provide a comprehensive overview of the evolving landscape of non-degradable spinal implants and bone graft substitutes, emphasising their applications in lumbar spinal fusion surgery. We highlight the necessity for continued research to improve clinical outcomes and enhance patient well-being.

Cellular Bone Matrix in Spine Surgery - Are They Worth the Risk: A Systematic Review

STUDY DESIGN

Systematic Review.

OBJECTIVE

To review the literature for complications and outcomes after the implantation of cellular bone matrix (CBM) during spine fusion.

METHODS

The PubMed database was queried from inception to January 31, 2023 for any articles that discussed the role of and identified a specific CBM in spinal fusion procedures. Adverse events, reoperations, methods, and fusion rates were collected from all studies and reported.

RESULTS

Six hundred articles were identified, of which 19 were included that reported outcomes of 7 different CBM products. Seven studies evaluated lumbar fusion, 11 evaluated cervical fusion, and 1 study reported adverse events of a single CBM product. Only 4 studies were comparative studies while others were limited to case series. Fusion rates ranged from 68% to 98.7% in the lumbar spine and 87% to 100% in the cervical spine, although criteria for radiographic fusion was variable. While 7 studies reported no adverse events, there was no strict consensus on what constituted a complication. One study reported catastrophic disseminated tuberculosis from donor contaminated CBM. The authors of 14 studies had conflicts of interest with either the manufacturer or distributor for their analyzed CBM.

CONCLUSIONS

Current evidence regarding the use of cellular bone matrix as an osteobiologic during spine surgery is weak and limited to low-grade non-comparative studies subject to industry funding. While reported fusion rates are high, the risk of severe complications should not be overlooked. Further large clinical trials are required to elucidate whether the CBMs offer any benefits that outweigh the risks.

Twenty-four-month interim results from a prospective, single-arm clinical trial evaluating the performance and safety of cellular bone allograft in patients undergoing lumbar spinal fusion

BACKGROUND

Autologous bone grafts are the gold standard for spinal fusion; however, harvesting autologous bone can result in donor site infection, hematomas, increased operative time, and prolonged pain. Cellular bone allografts (CBAs) are a viable alternative that avoids the need for bone harvesting and may increase fusion success alone or when used as an adjunct material. The present study examined the efficacy and safety of CBA when used as an adjunct graft material to lumbar arthrodesis.

METHODS

A prospective, single-arm, multicenter clinical trial (NCT02969616) was conducted in adult subjects (> 18 years of age) undergoing lumbar spinal fusion with CBA graft (CBA used as primary (≥ 50% by volume), with augmentation up to 50%). Radiographic fusion status was assessed by an independent review of dynamic radiographs and CT scans. Clinical outcomes were assessed with the Oswestry Disability Index (ODI), and Visual Analog Scales (VAS) score for back and leg pain. Adverse events were assessed through the 24-month follow-up period. The presented data represents an analysis of available subjects (n = 86) who completed 24 months of postoperative follow-up at the time the data was locked for analysis.

RESULTS

Postoperative 24-month fusion success was achieved in 95.3% of subjects (n = 82/86) undergoing lumbar spinal surgery. Clinical outcomes showed statistically significant improvements in ODI (46.3% improvement), VAS-Back pain (75.5% improvement), and VAS-Leg pain (85.5% improvement) (p < 0.01) scores at Month 24. No subject characteristics or surgical factors were associated with pseudoarthrosis. A favorable safety profile with a limited number of adverse events was observed.

CONCLUSIONS

The use of CBA as an adjunct graft material showed high rates of successful lumbar arthrodesis and significant improvements in pain and disability scores. CBA provides an alternative to autograft with comparable fusion success rates and clinical benefits.

TRIAL REGISTRATION

NCT02969616.

12-Month clinical and radiographic outcomes of ViBone viable bone matrix in patients undergoing cervical and lumbar spinal fusion surgery

BACKGROUND

To investigate the clinical safety and efficacy of ViBone^® Viable Bone Matrix (VBM), a next generation cellular bone matrix allograft that comprises all three essential bone-forming components: osteogenic, osteoinductive, and osteoconductive factors, and is optimized to enhance cell viability and bone formation.

METHODS

This was a multi-center, prospective, post-market study evaluating the safety and efficacy of ViBone VBM in patients undergoing 1-3 level anterior cervical discectomy and fusion or lumbar interbody fusion surgery. Patients were evaluated at baseline, 6-month, and 12-month follow-up clinically and radiographically. Clinical assessment included Visual Analog Scale for pain (VAS-pain), the Neck Disability Index (NDI) for patients with cervical pathologies, and the Oswestry Disability Index (ODI) for patients with lumbar pathologies. Fusion success defined by an independent radiologist was determined radiographically by plain films.

RESULTS

Clinical outcomes evaluated with VAS-pain, NDI, and ODI scales were improved significantly at 6 and 12 months compared to baseline. All patients reached clinically significant improvements at 12 months. There were no adverse events or infections attributed to ViBone VBM. At 12 months, the fusion rate per patient was 88.1% in cervical and 97.6% in lumbar patients, while per-level fusion was 98.5% for cervical and 100% for lumbar segments.

CONCLUSIONS

Patients undergoing cervical and lumbar spinal fusion implanted with ViBone VBM demonstrated favorable outcomes at 6 months and 12 months as measured by subjective clinical measures and radiographic fusion rates. Trial registration This study was registered as NCT03425682 on 1/29/2018.

Comparing Rates of Fusion and Time to Fusion in Viable Cellular Allograft and Autograft

BACKGROUND

Autograft or allograft frequently are used to enhance bone union in foot and ankle surgery. Viable cellular bone allograft uses viable cells and bone scaffolding in a gel base, but uncertainty remains around allograft's greater efficacy than autograft regarding rates of fusion (ROF) and time to fusion (TTF).

METHODS

Autograft, viable cellular allograft, and viable cellular allograft with autograft were compared in 199 forefoot, midfoot, and hindfoot arthrodeses performed over a 6-year period. Data collected from electronic medical records and radiographs were analyzed to determine ROF and TTF as well as rates of revision surgery for delayed or nonunion and compared among groups.

RESULTS

Eighty-seven patients comprised the autograft group, 81 the allograft group, and 31 the combined group. No significant differences were noted in patient demographics among the groups. No statistically significant differences in ROF were noted among the 3 groups, with 86% (75 of 87) fusion in the autograft group, 93% (75 of 81) in the allograft group, and 84% (26 of 31) in the combined group (P = .20). After conducting a multivariate analysis, we found no statistically significant difference for allograft or combined graft on TTF (P = .1379 and .2311, respectively). No significant difference was found in rate of revision surgery for nonunion, which was 1.2% (1 of 81) in the allograft group, 3.4% (3 of 87) in the autograft group, and 6.5% (2 of 31) in the combined group (P = .3).

CONCLUSION

No significant difference was found in ROF, TTF, or rate of revision surgery when comparing viable cellular allograft to autograft or combined allograft-autograft. Viable cellular allograft may be a reasonable alternative to the gold standard of autograft and should be considered an option in patients undergoing arthrodesis in foot and ankle surgery.

LEVEL OF EVIDENCE

Level III, therapeutic.

3D-Printing for Critical Sized Bone Defects: Current Concepts and Future Directions

The management and definitive treatment of segmental bone defects in the setting of acute trauma, fracture non-union, revision joint arthroplasty, and tumor surgery are challenging clinical problems with no consistently satisfactory solution. Orthopaedic surgeons are developing novel strategies to treat these problems, including three-dimensional (3D) printing combined with growth factors and/or cells. This article reviews the current strategies for management of segmental bone loss in orthopaedic surgery, including graft selection, bone graft substitutes, and operative techniques. Furthermore, we highlight 3D printing as a technology that may serve a major role in the management of segmental defects. The optimization of a 3D-printed scaffold design through printing technique, material selection, and scaffold geometry, as well as biologic additives to enhance bone regeneration and incorporation could change the treatment paradigm for these difficult bone repair problems.

Twelve-Month Results from a Prospective Clinical Study Evaluating the Efficacy and Safety of Cellular Bone Allograft in Subjects Undergoing Lumbar Spinal Fusion

BACKGROUND

While autologous bone grafts remain the gold standard for spinal fusion procedures, harvesting autologous bone is associated with significant complications, including donor site infection, hematomas, increased operative time, and prolonged pain. Cellular bone allograft (CBA) presents an alternative to autologous bone harvesting, with a favorable efficacy and safety profile. The current study further investigates CBA as an adjunct to lumbar spinal fusion procedures.

METHODS

A prospective, multicenter, open-label clinical study was conducted in subjects undergoing lumbar spinal fusion with CBA (NCT02969616). Radiographic fusion status was assessed by an independent review of dynamic radiographs and CT scans. Clinical outcome measures included the Oswestry Disability Index (ODI) and visual analogue scale (VAS) for back and leg pain. Adverse-event reporting was conducted throughout 12 months of follow-up. Available subject data at 12 months were analyzed.

RESULTS

A total of 274 subjects were enrolled into the study, with available data from 201 subjects (73.3%) who completed 12 months of postoperative radiographic and clinical evaluation at the time of analysis. Subjects had a mean age of 60.2 ± 11.5 years. A higher number of women (n = 124, 61.7%) than men (n = 77, 38.3%) were enrolled, with a collective mean BMI of 30.6 + 6.5 kg/m² (range 18.0-51.4). At month 12, successful fusion was achieved in 90.5% of subjects. A significant (<i>p</i> &amp;lt; 0.001) improvement in ODI, VAS-back, and VAS-leg clinical outcomes was also observed compared to baseline scores. One adverse event related to CBA (postoperative radiculopathy) was reported, with surgical exploration demonstrating interbody extrusion of graft material. This subject reported successful fusion at month 12.

CONCLUSIONS

CBA represents a viable substitute for harvesting of autograft alone with a high rate of successful fusion and significant improvements in subject-reported outcomes, such as pain and disability. Positive benefit was observed in subjects reporting single and multiple risk factors for pseudoarthrosis.

A Retrospective Analysis of Outcomes From Foot and Ankle Arthrodesis and Open Reduction and Internal Fixation Using Cellular Bone Allograft Augmentation

BACKGROUND

ViviGen is an allogeneic cellular bone matrix product containing lineage-committed bone cells, and can be used as an alternative to autograft bone or other augments to aid in arthrodesis or to enhance bony healing in open reduction and internal fixation (ORIF) procedures.

METHODS

This study included 153 consecutive patients undergoing ankle, midfoot, or hindfoot arthrodesis or ORIF procedures from January 2017 to October 2018, in which an allogeneic cellular bone matrix product was used to aid in bony healing. Retrospective chart review identified patient demographic factors and medical comorbidities and evaluated clinical and radiographic data to determine fusion/union rate and complications.

RESULTS

The overall fusion rate for the arthrodesis cohort was 97/113 (85.8%). The overall complication rate in this cohort was 22/113 (19.5%). Smokers had significantly lower rates of fusion compared with nonsmokers (P = .01). The observed bony healing rate for the ORIF cohort was 19/22 (86.4%), with a complication rate of 3/22 (13.6%).

CONCLUSION

With satisfactory fusion rates and relatively few complications, our findings suggest that ViviGen is a safe and efficacious alternative to other forms of bone graft augmentation for fusion and ORIF procedures about the foot and ankle. Further study is needed to compare the efficacy of ViviGen with autograft bone and other augments.

LEVELS OF EVIDENCE

Level IV: Case series.

A Review of Commercially Available Cellular-based Allografts

STUDY DESIGN

This was a narrative review.

OBJECTIVE

This review discusses our current knowledge regarding cellular-based allografts while highlighting the key gaps in the literature that must be addressed before their widespread adoption.

SUMMARY OF BACKGROUND DATA

Iliac crest bone graft is the gold-standard bone graft material but is associated with donor site morbidity. Commonly utilized bone graft extenders such as demineralized bone matrix and bone morphogenetic protein have conflicting data supporting their efficacy and lack the osteogenic potential of new cellular-based allograft options.

METHODS

An extensive literature review was performed. The literature was then summarized in accordance with the authors' clinical experience.

RESULTS

There is not widespread evidence thus far that the addition of the osteogenic cellular component to allograft enhances spinal fusion, as a recent study by Bhamb and colleagues demonstrated superior bone formation during spine fusion in an aythmic rat model when demineralized bone matrix was used in comparison to Osteocel Plus. Furthermore, the postimplantation cellular viability and osteogenic and osteoinductive capacity of cellular-based allografts need to be definitively established, especially given that a recent study by Lina and colleagues demonstrated a paucity of bone marrow cell survival in an immunocompetent mouse posterolateral spinal fusion model.

CONCLUSIONS

This data indicates that the substantially increased cost of these cellular allografts may not be justified.

LEVEL OF EVIDENCE

Level V.

Osteobiologics

BACKGROUND

Osteobiologics are engineered materials that facilitate bone healing and have been increasingly used in spine surgery. Autologous iliac crest bone grafts have been used historically, but morbidity associated with graft harvesting has led surgeons to seek alternative solutions. Allograft bone, biomaterial scaffolds, growth factors, and stem cells have been explored as bone graft substitutes and supplements.

OBJECTIVE

To review current and emerging osteobiologic technologies.

METHODS

A literature review of English-language studies was performed in PubMed. Search terms included combinations of "spine," "fusion," "osteobiologics," "autologous," "allogen(e)ic," "graft," "scaffold," "bone morphogenic protein," and "stem cells."

RESULTS

Evidence supports allograft bone as an autologous bone supplement or replacement in scenarios where minimal autologous bone is available. There are promising data on ceramics and P-15; however, comparative human trials remain scarce. Growth factors, including recombinant human bone morphogenic proteins (rhBMPs) 2 and 7, have been explored in humans after successful animal trials. Evidence continues to support the use of rhBMP-2 in lumbar fusion in patient populations with poor bone quality or revision surgery, while there is limited evidence for rhBMP-7. Stem cells have been incredibly promising in promoting fusion in animal models, but human trials to this point have only involved products with questionable stem cell content, thereby limiting possible conclusions.

CONCLUSION

Engineered stem cells that overexpress osteoinductive factors are likely the future of spine fusion, but issues with applying viral vector-transduced stem cells in humans have limited progress.

Commercial Bone Grafts Claimed as an Alternative to Autografts: Current Trends for Clinical Applications in Orthopaedics

In the last twenty years, due to an increasing medical and market demand for orthopaedic implants, several grafting options have been developed. However, when alternative bone augmentation materials mimicking autografts are searched on the market, commercially available products may be grouped into three main categories: cellular bone matrices, growth factor enhanced bone grafts, and peptide enhanced xeno-hybrid bone grafts. Firstly, to obtain data for this review, the search engines Google and Bing were employed to acquire information from reports or website portfolios of important competitors in the global bone graft market. Secondly, bibliographic databases such as Medline/PubMed, Web of Science, and Scopus were also employed to analyse data from preclinical/clinical studies performed to evaluate the safety and efficacy of each product released on the market. Here, we discuss several products in terms of osteogenic/osteoinductive/osteoconductive properties, safety, efficacy, and side effects, as well as regulatory issues and costs. Although both positive and negative results were reported in clinical applications for each class of products, to date, peptide enhanced xeno-hybrid bone grafts may represent the best choice in terms of risk/benefit ratio. Nevertheless, more prospective and controlled studies are needed before approval for routine clinical use.

Perioperative Management of Antirheumatic Medications in Patients with RA and SLE Undergoing Elective Foot and Ankle Surgery: A Critical Analysis Review

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Recent literature has shown that continued use rather than discontinuation of various antirheumatic agents throughout the perioperative period may present an opportunity to mitigate the risks of elective surgery.

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For patients with rheumatoid arthritis and systemic lupus erythematosus, perioperative management of medication weighs the risk of infection against the risk of disease flare when immunosuppressive medications are withheld.

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Broadly speaking, current evidence, although limited in quality, supports perioperative continuation of disease-modifying antirheumatic drugs, whereas biologic drugs should be withheld perioperatively, based on the dosing interval of the specific drug.

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For any withheld biologic drug, it is generally safe to restart these medications approximately 2 weeks after surgery, once the wound shows evidence of healing, all sutures and staples have been removed, and there is no clinical evidence of infection. The focus of this recommendation applies to the optimization of wound-healing, not bone-healing.

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In most cases, the usual daily dose of glucocorticoids is administered in the perioperative period rather than administering "stress-dose steroids" on the day of surgery.

Investigating the efficacy of allograft cellular bone matrix for spinal fusion: a systematic review of the literature

OBJECTIVE

The use of allograft cellular bone matrices (ACBMs) in spinal fusion has expanded rapidly over the last decade. Despite little objective data on its effectiveness, ACBM use has replaced the use of traditional autograft techniques, namely iliac crest bone graft (ICBG), in many centers.

METHODS

In accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, a systematic review was conducted of the PubMed, Cochrane Library, Scopus, and Web of Science databases of English-language articles over the time period from January 2001 to December 2020 to objectively assess the effectiveness of ACBMs, with an emphasis on the level of industry involvement in the current body of literature.

RESULTS

Limited animal studies (n = 5) demonstrate the efficacy of ACBMs in spinal fusion, with either equivalent or increased rates of fusion compared to autograft. Clinical human studies utilizing ACBMs as bone graft expanders or bone graft substitutes (n = 5 for the cervical spine and n = 8 for the lumbar spine) demonstrate the safety of ACBMs in spinal fusion, but fail to provide conclusive level I, II, or III evidence for its efficacy. Additionally, human studies are plagued with several limiting factors, such as small sample size, lack of prospective design, lack of randomization, absence of standardized assessment of fusion, and presence of industry support/relevant conflict of interest.

CONCLUSIONS

There exist very few objective, unbiased human clinical studies demonstrating ACBM effectiveness or superiority in spinal fusion. Impartial, well-designed prospective studies are needed to offer evidence-based best practices to patients in this domain.

Existing clinical evidence on the use of cellular bone matrix grafts in spinal fusion: updated systematic review of the literature

OBJECTIVE

Spinal fusion surgery is increasingly common; however, pseudarthrosis remains a common complication affecting as much as 15% of some patient populations. Currently, no clear consensus on the best bone graft materials to use exists. Recent advances have led to the development of cell-infused cellular bone matrices (CBMs), which contain living components such as mesenchymal stem cells (MSCs). Relatively few clinical outcome studies on the use of these grafts exist, although the number of such studies has increased in the last 5 years. In this study, the authors aimed to summarize and critically evaluate the existing clinical evidence on commercially available CBMs in spinal fusion and reported clinical outcomes.

METHODS

The authors performed a systematic search of the MEDLINE and PubMed electronic databases for peer-reviewed, English-language original articles (1970-2020) in which the articles' authors studied the clinical outcomes of CBMs in spinal fusion. The US National Library of Medicine electronic clinical trials database (www.ClinicalTrials.gov) was also searched for relevant ongoing clinical trials.

RESULTS

Twelve published studies of 6 different CBM products met inclusion criteria: 5 studies of Osteocel Plus/Osteocel (n = 354 unique patients), 3 of Trinity Evolution (n = 114), 2 of ViviGen (n = 171), 1 of map3 (n = 41), and 1 of VIA Graft (n = 75). All studies reported high radiographic fusion success rates (range 87%-100%) using these CBMs. However, this literature was overwhelmingly limited to single-center, noncomparative studies. Seven studies disclosed industry funding or conflicts of interest (COIs). There are 4 known trials of ViviGen (3 trials) and Bio4 (1 trial) that are ongoing.

CONCLUSIONS

CBMs are a promising technology with the potential of improving outcome after spinal fusion. However, while the number of studies conducted in humans has tripled since 2014, there is still insufficient evidence in the literature to recommend for or against CBMs relative to cheaper alternative materials. Comparative, multicenter trials and outcome registries free from industry COIs are indicated.

Stem Cells and Spinal Fusion

BACKGROUND

This manuscript is a review of the literature investigating the use of mesenchymal stem cells (MSCs) being applied in the setting of spinal fusion surgery. We mention the rates of pseudarthrosis, discuss current bone grafting options, and examine the preclinical and clinical outcomes of utilizing MSCs to assist in successfully fusing the spine.

METHODS

A thorough literature review was conducted to look at current and previous preclinical and clinical studies using stem cells for spinal fusion augmentation. Searches for PubMed/MEDLINE and ClinicalTrials.gov through January 2021 were conducted for literature mentioning stem cells and spinal fusion.

RESULTS

All preclinical and clinical studies investigating MSC use in spinal fusion were examined. We found 19 preclinical and 17 clinical studies. The majority of studies, both preclinical and clinical, were heterogeneous in design due to different osteoconductive scaffolds, cells, and techniques used. Preclinical studies showed promising outcomes in animal models when using appropriate osteoconductive scaffolds and factors for osteogenic differentiation. Similarly, clinical studies have promising outcomes but differ in their methodologies, surgical techniques, and materials used, making it difficult to adequately compare between the studies.

CONCLUSION

MSCs may be a promising option to use to augment grafting for spinal fusion surgery. MSCs must be used with appropriate osteoconductive scaffolds. Cell-based allografts and the optimization of their use have yet to be fully elucidated. Further studies are necessary to determine the efficacy of MSCs with different osteoconductive scaffolds and growth/osteogenic differentiation factors.

LEVEL OF EVIDENCE

3.

Allografts and Spinal Fusion

BACKGROUND

Back pain is a common chief complaint within the United States and is caused by a multitude of etiologies. There are many different treatment modalities for back pain, with a frequent option being spinal fusion procedures. The success of spinal fusion greatly depends on instrumentation, construct design, and bone grafts used in surgery. Bone allografts are important for both structural integrity and providing a scaffold for bone fusion to occur.

METHOD

Searches were performed using terms "allografts" and "bone" as well as product names in peer reviewed literature Pubmed, Google Scholar, FDA-510k approvals, and clinicaltrials.gov.

RESULTS

This study is a review of allografts and focuses on currently available products and their success in both animal and clinical studies.

CONCLUSION

Bone grafts used in surgery are generally categorized into 3 main types: autogenous (from patient's own body), allograft (from cadaveric or living donor), and synthetic. This paper focuses on allografts and provides an overview on the different subtypes with an emphasis on recent product development and uses in spinal fusion surgery.

Development of AOSpine BOnE (Bone Osteobiologics and Evidence) Classification

STUDY DESIGN

Classification development.

OBJECTIVES

The aim of our study was to develop a 3-tier classification for the levels of evidence for osteobiologics and provide a description of the principles by which osteobiologics can be evaluated. BOnE (Bone Osteobiologics and Evidence) classification evaluates each osteobiologic based on the available evidence, and if the published evidence is based on clinical, in vivo or in vitro studies.

METHODS

The process of establishing the BOnE classification included 5 face-to-face meetings and 2 web calls among members of the AOSpine Knowledge Forum Degenerative.

RESULTS

The 3 levels of evidence were determined based on the type of data on osteobiologics: level A for human studies, level B for animal studies, and level C for in vitro studies, with level A being the highest level of evidence. Each level was organized into 4 subgroups (eg, A1, A2, A3, and A4).

CONCLUSIONS

The use and the variety of osteobiologics for spine fusion has dramatically increased over the past few decades; however, literature on their effectiveness is inconclusive. Several prior systematic reviews developed by AOSpine Knowledge Forum Degenerative reported low level of evidence primarily due to the high risk of bias, small sample size, lack of control groups, and limited patient-reported outcomes. BOnE classification will provide a universal platform for research studies and journal publications to classify a new or an existing product and will allow for creating decision-making algorithms for surgical planning.

Comparing cellular bone matrices for posterolateral spinal fusion in a rat model

INTRODUCTION

Cellular bone matrices (CBM) are allograft products that provide three components essential to new bone formation: an osteoconductive scaffold, extracellular growth factors for cell proliferation and differentiation, and viable cells with osteogenic potential. This is an emerging technology being applied to augment spinal fusion procedures as an alternative to autografts.

METHODS

We aim to compare the ability of six commercially-available human CBMs (Trinity ELITE®, ViviGen®, Cellentra®, Osteocel® Pro, Bio4® and Map3®) to form a stable spinal fusion using an athymic rat model of posterolateral fusion. Iliac crest bone from syngeneic rats was used as a control to approximate the human gold standard. The allografts were implanted at L4-5 according to vendor specifications in male athymic rats, with 15 rats in each group. MicroCT scans were performed at 48 hours and 6 weeks post-implantation. The rats were euthanized 6 weeks after surgery and the lumbar spines were harvested for X-ray, manual palpation and histology analysis by blinded reviewers.

RESULTS

By manual palpation, five of 15 rats of the syngeneic bone group were fused at 6 weeks. While Trinity ELITE had eight of 15 and Cellentra 11 of 15 rats with stable fusion, only 2 of 15 of ViviGen-implanted spines were fused and zero of 15 of the Osteocel Pro, Bio4 and Map3 produced stable fusion. MicroCT analysis indicated that total bone volume increased from day 0 to week 6 for all groups except syngeneic bone group. Trinity ELITE (65%) and Cellentra (73%) had significantly greater bone volume increases over all other implants, which was consistent with the histological analysis.

CONCLUSION

Trinity ELITE and Cellentra were significantly better than other implants at forming new bone and achieving spinal fusion in this rat model at week 6. These results suggest that there may be large differences in the ability of different CBMs to elicit a successful fusion in the posterolateral spine.

A Comparative Evaluation of Commercially Available Cell-Based Allografts in a Rat Spinal Fusion Model

Background

To evaluate the comparative abilities of commercially available, viable, cellular bone allografts to promote posterolateral spinal fusion.

Methods

Human allografts containing live cells were implanted in the athymic rat model of posterolateral spine fusion. Three commercially available allogeneic cellular bone matrices (Trinity Evolution, Trinity ELITE and Osteocel Plus) were compared with syngeneic iliac crest bone as the control. All spines underwent radiographs, manual palpation, and micro-computed tomography (CT) analysis after excision at 6 weeks. Histological sections of randomly selected spines were subjected to semiquantitative histopathological scoring for bone formation.

Results

By manual palpation, posterolateral fusion was detected in 40% (6/15) of spines implanted with syngeneic bone, whereas spines implanted with Trinity Evolution and Trinity ELITE allografts yielded 71% (10/14) and 77% (10/13) fusion, respectively. Only 7% (1/14) of spines implanted with Osteocel Plus allografts were judged fused by manual palpation (statistically significantly less than ELITE, P < .0007, and Evolution, P < .0013). The mineralized cancellous bone component of the allografts confounded radiographic analysis, but Trinity Evolution (0.452 ± 0.064) and Trinity ELITE (0.536 ± 0.109) allografts produced statistically significantly higher bone fusion mass volumes measured by quantitative micro-CT than did syngeneic bone (0.292 ± 0.109, P < .0001 for ELITE and P < .003 for Evolution) and Osteocel Plus (0.258 ± 0.103, P < .0001). Semiquantitative histopathological scores supported these findings because the total bone and bone marrow scores reflected significantly better new bone and marrow formation in the Trinity groups than in the Osteocel Plus group.

Conclusions

The Trinity Evolution and Trinity ELITE cellular bone allografts were more effective at creating posterolateral fusion than either the Osteocel Plus allografts or syngeneic bone in this animal model.

Clinical Relevance

The superior fusion rate of Trinity cellular bone allografts may lead to better clinical outcome of spinal fusion surgeries.

Stem Cells and Spinal Fusion

There are a number of bone regeneration therapeutics available to aid spinal fusion; however, many are associated with pseudarthrosis, inflammation, and other complications. Mesenchymal stem cells for fusion has been promoted to mitigate these risks and achieve successful bony fusion. This article reviews the clinical studies available with use in spinal fusion. Preliminary results demonstrate that stem cells can provide high rates of fusion, comparable to autograft, without associated morbidity. Autologous and allogeneic stem cell sources showed similar rates of fusion in this review. Further research is required to evaluate which clinical situations are the optimum for stem cell use.

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

Background

Insufficient data exist on bone graft substitute materials efficacy; two thirds lack any clinical data.1,2 This prospective animal study identified efficacy differences among commercially available materials of several classes.

Methods

Historically validated muscle pouch osteoinduction study (OIS) and posterolateral fusion (PLF) were performed in an athymic rat model. Grafting material products implanted were demineralized bone matrix (DBM)-based allografts (Accell EVO3, DBX Mix, DBX Strip, Grafton Crunch, Grafton Flex, Grafton Matrix, Grafton Putty, Magnifuse, and Progenix Plus), allografts (OsteoSponge, MinerOss), cellular allograft (Osteocel Plus), ceramics (Mozaik Strip), or activated ceramics (Actifuse ABX Putty, Vitoss BA). After 4 weeks, OIS specimens were evaluated ex vivo by histologic osteoinductivity. After 8 weeks, PLF ex vivo specimens were evaluated for fusion by manual palpation (F_MP), radiography (F_XR), and histology (F_HISTO).

Results

OIS: No materials exhibited a rejection reaction on histology. All DBM-based materials exhibited osteoinductive potential as new bone formation at > 88% of implanted sites. One plain allograft (OsteoSponge) formed bone at 25% of sites. No bone formed for one ceramic (Mozaik Strip), three activated ceramics (Actifuse ABX Putty), or one cellular allograft, regardless of human bone marrow aspirate (hBMA) when added. PLF: Among the 10 DBMs, 6 had F_MP of 100% (Accell EVO3, DBX Mix, DBX Strip, Grafton Flex, Grafton Putty, Magnifuse), 2 had F_MP of 94% (Grafton Crunch, Grafton Matrix), and 2 conditions had F_MP of 0% (Progenix Plus, Progenix Plus + athymic rat iliac crest bone graft [arICBG]). Ceramics (Mozaik Strip), activated ceramics (Actifuse ABX Putty, Vitoss BA), plain allograft (OsteoSponge, MinerOss (PLF study), and cellular allograft (Osteocel Plus) demonstrated 0% F_MP. ArICBG demonstrated 13% F_MP.

Conclusions

Eight DBM-based materials (Accell EVO3, DBX Mix, DBX Strip, Grafton Crunch, Grafton Flex, Grafton Matrix, Grafton Putty, Magnifuse) demonstrated excellent (> 90% F_MP) efficacy in promoting fusion via bone healing. Two DBM conditions (Progenix Plus, Progenix Plus + arICBG) showed no manual palpation fusion (F_MP). Systematically, over the 2 studies (OIS and PLF), cellular (Osteocel Plus), plain allografts (OsteoSponge, MinerOss; PLF study), ceramic (Mozaik Strip), and activated ceramics (Actifuse ABX Putty, Vitoss BA) demonstrated poor F_MP efficacy (< 10%).

Clinical Relevance

When selecting DBMs, clinicians must be cognizant of variability in DBM efficacy by product and lot. While theoretically osteoinductive, cellular allograft and activated ceramics yielded poor in vivo efficacy. Whole allograft and ceramics may provide osteoconductive scaffolding for mixed-material grafting; however, surgeons should be cautious in using them alone. Direct clinical data are needed to establish efficacy for any bone graft substitute.

Substantial Overview on Mesenchymal Stem Cell Biological and Physical Properties as an Opportunity in Translational Medicine

Mesenchymal stem cells (MSC) have piqued worldwide interest for their extensive potential to treat a large array of clinical indications, their unique and controversial immunogenic and immune modulatory properties allowing ample discussions and debates for their possible applications. Emerging data demonstrating that the interaction of biomaterials and physical cues with MSC can guide their differentiation into specific cell lineages also provide new interesting insights for further MSC manipulation in different clinical applications. Moreover, recent discoveries of some regulatory molecules and signaling pathways in MSC niche that may regulate cell fate to distinct lineage herald breakthroughs in regenerative medicine. Although the advancement and success in the MSC field had led to an enormous increase in the amount of ongoing clinical trials, we still lack defined clinical therapeutic protocols. This review will explore the exciting opportunities offered by human and animal MSC, describing relevant biological properties of these cells in the light of the novel emerging evidence mentioned above while addressing the limitations and challenges MSC are still facing.

Allogenic Stem Cells in Spinal Fusion: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVES

To review, critically appraise, and synthesize evidence on the use of allogenic stem cell products for spine fusion compared with other bone graft materials.

METHODS

Systematic searches of PubMed/MEDLINE, through October 31, 2018 and of EMBASE and ClinicalTrials.gov through April 13, 2018 were conducted for literature comparing allogenic stem cell sources for fusion in the lumbar or cervical spine with other fusion methods. In the absence of comparative studies, case series of ≥10 patients were considered.

RESULTS

From 382 potentially relevant citations identified, 6 publications on lumbar fusion and 5 on cervical fusion met the inclusion criteria. For lumbar arthrodesis, mean Oswestry Disability Index (ODI), visual analogue scale (VAS) pain score, and fusion rates were similar for anterior lumbar interbody fusion (ALIF) using allogenic multipotent adult progenitor cells (Map3) versus recombinant human bone morphogenetic protein-2 (rhBMP-2) in the one comparative lumbar study (90% vs 92%). Across case series of allogenic stem cell products, function and pain were improved relative to baseline and fusion occurred in ≥90% of patients at ≥12 months. For cervical arthrodesis across case series, stem cell products improved function and pain compared with baseline at various time frames. In a retrospective cohort study fusion rates were not statistically different for Osteocel compared with Vertigraft allograft (88% vs 95%). Fusion rates varied across time frames and intervention products in case series.

CONCLUSIONS

The overall quality (strength) of evidence of effectiveness and safety of allogenic stem cells products for lumbar and cervical arthrodesis was very low, meaning that we have very little confidence that the effects seen are reflective of the true effects.

Predictive Factors and Rates of Fusion in Minimally Invasive Transforaminal Lumbar Interbody Fusion Utilizing rhBMP-2 or Mesenchymal Stem Cells

Background

Several fusion adjuncts exist to enhance fusion rates during minimally invasive transforaminal lumbar interbody fusion (MI-TLIF). The objective of this study was to compare fusion rates in patients undergoing MI-TLIF with either rhBMP-2 or cellularized bone matrix (CBM).

Methods

We conducted a single surgeon retrospective cohort study of patients who underwent MI-TLIF with either rhBMP-2 or CBM placed in an interbody cage. Single and multilevel procedures were included. Fusion was assessed on computed tomography scans at 12-month follow-up by an independent, blinded, board-certified neuroradiologist. Fusion rates and rate of revision surgery were compared with a Fisher exact test between the 2 groups. A multivariate regression analysis was performed to identify patient factors that were predictive of radiographic nonunion after MI-TLIF.

Results

A total of 93 fusion levels in 78 patients were reviewed. Thirty-nine patients received CBM, and 39 patients received rhBMP-2. The patients receiving rhBMP-2 were older on average (61.4 vs 55.6, P = .03). The overall fusion rate was 68% in the CBM group (32/47 levels) and 78% in the rhBMP-2 group (36/46) (P = .35). Only preoperative hypertension was predictive of radiographic nonunion (odds ratio = 3.5, P = .05). There were 3 smokers in the CBM group and 4 smokers in the BMP group, and 1 in each group experienced radiographic pseudarthrosis. A total of 4 patients, 3 in the CBM group and 1 in the BMP group (P = .61), required revision for symptomatic pseudarthrosis. All of these patients had a single-level index procedure.

Conclusions

There were no differences in radiographic fusion and rate of revision surgery in patients who underwent MI-TLIF with either rhBMP-2 or CBM as fusion adjuncts.

Level of Evidence

3.

Clinical Relevance

Both rhBMP-2 and CBMs can be used as effective fusion adjuncts without any clear advantage of one over the other.

Stem Cell and Advanced Nano Bioceramic Interactions

Bioceramics are type of biomaterials generally used for orthopaedic applications due to their similar structure with bone. Especially regarding to their osteoinductivity and osteoconductivity, they are used as biodegradable scaffolds for bone regeneration along with mesenchymal stem cells. Since chemical properties of bioceramics are important for regeneration of tissue, physical properties are also important for cell proliferation. In this respect, several different manufacturing methods are used for manufacturing nano scale bioceramics. These nano scale bioceramics are used for regeneration of bone and cartilage both alone or with other types of biomaterials. They can also act as carrier for the delivery of drugs in musculoskeletal infections without causing any systemic toxicity.

Commercial Products for Osteochondral Tissue Repair and Regeneration

The osteochondral tissue represents a complex structure composed of four interconnected structures, namely hyaline cartilage, a thin layer of calcified cartilage, subchondral bone, and cancellous bone. Due to the several difficulties associated with its repair and regeneration, researchers have developed several studies aiming to restore the native tissue, some of which had led to tissue-engineered commercial products. In this sense, this chapter discusses the good manufacturing practices, regulatory medical conditions and challenges on clinical translations that should be fulfilled regarding the safety and efficacy of the new commercialized products. Furthermore, we review the current osteochondral products that are currently being marketed and applied in the clinical setting, emphasizing the advantages and difficulties of each one.

Stem Cells in Spinal Fusion

STUDY DESIGN

Review of literature.

OBJECTIVES

This review of literature investigates the application of mesenchymal stem cells (MSCs) in spinal fusion, highlights potential uses in the development of bone grafts, and discusses limitations based on both preclinical and clinical models.

METHODS

A review of literature was conducted looking at current studies using stem cells for augmentation of spinal fusion in both animal and human models.

RESULTS

Eleven preclinical studies were found that used various animal models. Average fusion rates across studies were 59.8% for autograft and 73.7% for stem cell-based grafts. Outcomes included manual palpation and stressing of the fusion, radiography, micro-computed tomography (μCT), and histological analysis. Fifteen clinical studies, 7 prospective and 8 retrospective, were found. Fusion rates ranged from 60% to 100%, averaging 87.1% in experimental groups and 87.2% in autograft control groups.

CONCLUSIONS

It appears that there is minimal clinical difference between commercially available stem cells and bone marrow aspirates indicating that MSCs may be a good choice in a patient with poor marrow quality. Overcoming morbidity and limitations of autograft for spinal fusion, remains a significant problem for spinal surgeons and further studies are needed to determine the efficacy of stem cells in augmenting spinal fusion.

A comparison of radiographic and clinical outcomes of anterior lumbar interbody fusion performed with either a cellular bone allograft containing multipotent adult progenitor cells or recombinant human bone morphogenetic protein-2

Background

Both the map3 Cellular Allogeneic Bone Graft® and recombinant human bone morphogenetic protein 2 (rhBMP-2, Infuse®) were developed to provide an alternative to iliac crest autograft, thus eliminating the morbidity associated with its harvest. The recent literature concerning adverse events associated with the use of rhBMP-2, however, highlights the need for a safe and effective alternative. The multipotent adult progenitor cells (MAPC) found in map3 allograft may provide this alternative. The purpose of this study is to report 1-year outcomes of patients treated via anterior lumbar interbody fusion (ALIF) using either map3 Cellular Allogeneic Bone Graft or rhBMP-2 for bony fusion.

Methods

This was a retrospective evaluation of 41 patients treated via ALIF with either map3 or rhBMP-2 in a polyetheretherketone cage with posterior stabilization at 1, 2, or 3 consecutive levels (L3-S1). Patients were equally divided between treatment groups. The Oswestry Disability Index (ODI) and visual analog scores (VAS) for pain were documented as part of the standard of care. An independent radiologist assessed bridging of bone, disc height, and lordosis. Primary outcome measures included radiographic analysis of fusion by plain film and CTs. Secondary clinical outcomes included visual analogue scale for neck and arm pain and low back disability index scores.

Results

The overall fusion rate was 91%, with no significant difference between groups. Improvements in ODI and VAS were observed among all patients (p < 0.001), with no significant difference between groups for ODI (p = 0.966) or VAS (p = 0.251). There was no significant difference in terms of changes to disc height and lordosis between groups (p < 0.05). The rhBMP-2 group had increased post-operative complications when compared to the map3 group, but the low numbers precluded statistical analysis.

Conclusion

Improvements in radiographic and clinical findings were observed in both treatment groups one-year postoperatively. Map3 allograft demonstrated equivalent fusion rates to rhBMP-2. A review of surgical supply costs at the treatment facility favored map3 allograft for the treatment of patients with DDD undergoing an ALIF in 1–3 levels compared to rhBMP-2. Further studies to evaluate long-term outcomes and post-operative complications are required.

Use of Allogenic Mesenchymal Cellular Bone Matrix in Anterior and Posterior Cervical Spinal Fusion: A Case Series of 21 Patients

Study Design

Retrospective case series.

Purpose

To report our early experience using allogenic mesenchymal cellular bone matrix (CBM) products in cervical spine fusion.

Overview of Literature

Multi-level cervical fusions have historically yielded lower fusion rates than single level fusions, especially in patients with high risk medical comorbidities. At this time, significant literature in cervical fusion outcomes with this cellular allograft technology is lacking.

Methods

Twenty-one patients underwent either multilevel (3 or 4 level) anterior cervical discectomy and fusion, anterior cervical corpectomy and fusion, or posterior cervical fusion. ViviGen (DePuy Synthes Spine, Raynham, MA, USA), an allogenic bone matrix product, was used in addition to standard instrumentation. Radiographic evaluation was performed at 2 weeks, 12 weeks, 24 weeks and 1 year postoperative. Visual analog scale (VAS) and neck disability index (NDI) scores along with return to work and leisure activity were recorded.

Results

At 6 months postoperative, all patients had radiographic evidence of bone fusion regardless of age or medical comorbidities. All patients reported subjective improvement with a mean decrease in VAS from 8.3 to 1.5 and a mean decrease in NDI from 40.3% to 6.0% at 1 year. All patients also returned to work and/or regular leisure activity within 3 months.

Conclusions

Twenty-one patients undergoing high-risk anterior and posterior cervical spine fusion, with the use of a commercially available mesenchymal CBM product, went on to radiographic fusion and all had improvement in subjective outcomes. While further effort and research is needed to validate its widespread use, this study shows favorable use of CBM in cervical fusion for high-risk cases.

An allograft generated from adult stem cells and their secreted products efficiently fuses vertebrae in immunocompromised athymic rats and inhibits local immune responses

BACKGROUND CONTEXT

Spine pain and the disability associated with it are epidemic in the United States. According to the National Center for Health Statistics, more than 650,000 spinal fusion surgeries are performed annually in the United States, and yet there is a failure rate of 15%-40% when standard methods employing current commercial bone substitutes are used. Autologous bone graft is the gold standard in terms of fusion success, but the morbidity associated with the procedure and the limitations in the availability of sufficient material have limited its use in the majority of cases. A freely available and immunologically compatible bone mimetic with the properties of live tissue is likely to substantially improve the outcome of spine fusion procedures without the disadvantages of autologous bone graft.

PURPOSE

This study aimed to compare a live human bone tissue analog with autologous bone grafting in an immunocompromised rat model of posterolateral fusion.

DESIGN/SETTING

This is an in vitro and in vivo preclinical study of a novel human stem cell-derived construct for efficacy in posterolateral lumbar spine fusion.

METHODS

Osteogenically enhanced human mesenchymal stem cells (OEhMSCs) were generated by exposure to conditions that activate the early stages of osteogenesis. Immunologic characteristics of OEhMSCs were evaluated in vitro. The secreted extracellular matrix from OEhMSCs was deposited on a clinical-grade gelatin sponge, resulting in bioconditioned gelatin sponge (BGS). Bioconditioned gelatin sponge was used alone, with live OEhMSCs (BGS+OEhMSCs), or with whole human bone marrow (BGS+hBM). Efficacy for spine fusion was determined by an institutionally approved animal model using 53 nude rats.

RESULTS

Bioconditioned gelatin sponge with live OEhMSCs did not cause cytotoxicity when incubated with immunologically mismatched lymphocytes, and OEhMSCs inhibited lymphocyte expansion in mixed lymphocyte assays. Bioconditioned gelatin sponge with live OEhMSC and BGS+hBM constructs induced profound bone growth at fusion sites in vivo, with a comparable rate of fusion with syngeneic bone graft (negative [0 of 10], BGS alone [0 of 10], bone graft [7 of 10], BGS+OEhMSC [10 of 15], and BGS+hBM [8 of 8]).

CONCLUSIONS

Collectively, these studies demonstrate that BGS+OEhMSC constructs possess low immunogenicity and drive vertebral fusion with efficiency matching syngeneic bone graft in rodents. We also demonstrate that BGS serves as a promising scaffold for spine fusion when combined with hBM.

Stem and progenitor cells: advancing bone tissue engineering

Unlike many other postnatal tissues, bone can regenerate and repair itself; nevertheless, this capacity can be overcome. Traditionally, surgical reconstructive strategies have implemented autologous, allogeneic, and prosthetic materials. Autologous bone--the best option--is limited in supply and also mandates an additional surgical procedure. In regenerative tissue engineering, there are myriad issues to consider in the creation of a functional, implantable replacement tissue. Importantly, there must exist an easily accessible, abundant cell source with the capacity to express the phenotype of the desired tissue, and a biocompatible scaffold to deliver the cells to the damaged region. A literature review was performed using PubMed; peer-reviewed publications were screened for relevance in order to identify key advances in stem and progenitor cell contribution to the field of bone tissue engineering. In this review, we briefly introduce various adult stem cells implemented in bone tissue engineering such as mesenchymal stem cells (including bone marrow- and adipose-derived stem cells), endothelial progenitor cells, and induced pluripotent stem cells. We then discuss numerous advances associated with their application and subsequently focus on technological advances in the field, before addressing key regenerative strategies currently used in clinical practice. Stem and progenitor cell implementation in bone tissue engineering strategies have the ability to make a major impact on regenerative medicine and reduce patient morbidity. As the field of regenerative medicine endeavors to harness the body's own cells for treatment, scientific innovation has led to great advances in stem cell-based therapies in the past decade.

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

STUDY DESIGN

A narrative review of literature.

OBJECTIVE

This 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 DATA

Ever 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.

METHODS

A 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.

RESULTS

A 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.

CONCLUSIONS

There 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.

Variables Affecting Fusion Rates in the Rat Posterolateral Spinal Fusion Model with Autogenic/Allogenic Bone Grafts: A Meta-analysis

The rat posterolateral spinal fusion model with autogenic/allogenic bone graft (rat PFABG) has been increasingly utilized as an experimental model to assess the efficacy of novel fusion treatments. The objective of this study was to investigate the reliability of the rat PFABG model and examine the effects of different variables on spinal fusion. A web-based literature search from January, 1970 to September, 2015, yielded 26 studies, which included 40 rat PFABG control groups and 449 rats. Data regarding age, weight, sex, and strain of rats, graft volume, graft type, decorticated levels, surgical approach, institution, the number of control rats, fusion rate, methods of fusion assessment, and timing of fusion assessment were collected and analyzed. The primary outcome variable of interest was fusion rate, as evaluated by manual palpation. Fusion rates varied widely, from 0 to 96%. The calculated overall fusion rate was 46.1% with an I ² value of 62.4, which indicated moderate heterogeneity. Weight >300 g, age >14 weeks, male rat, Sprague-Dawley strain, and autogenic coccyx grafts increased fusion rates with statistical significance. Additionally, an assessment time-point ≥8 weeks had a trend towards statistical significance (p = 0.070). Multi-regression analysis demonstrated that timing of assessment and age as continuous variables, as well as sex as a categorical variable, can predict the fusion rate with R ² = 0.82. In an inter-institution reliability analysis, the pooled overall fusion rate was 50.0% [44.8, 55.3%], with statistically significant differences among fusion outcomes at different institutions (p < 0.001 and I ² of 72.2). Due to the heterogeneity of fusion outcomes, the reliability of the rat PFABG model was relatively limited. However, selection of adequate variables can optimize its use as a control group in studies evaluating the efficacy of novel fusion therapies.

Preliminary Results of Bioactive Amniotic Suspension with Allograft for Achieving One and Two-Level Lumbar Interbody Fusion

BACKGROUND

Bone graft material for lumbar fusion was historically autologous bone graft (ABG). In recent years alternatives such as allograft, demineralized bone matrix (DBM), ceramics, and bone morphogenetic protein (BMP) have gained favor, although the complications of these are not fully understood. Bioactive amniotic suspension (BAS) with allograft is a new class of material derived from human amniotic tissue.

METHODS

Eligible patients receiving a one or two level lumbar interbody fusion with Nucel, a BAS with allograft, were contacted and scheduled for a mininmim 12 month follow-up visit. Patients were evaluated for fusion using CT's and plain radiographs. Clincal outcomes, including ODI, VAS back and leg were collected, as well as comorbidities including BMI, smoking status, diabetes and previous lumbar surgery.

RESULTS

One-level patients (N=38) were 71.1% female with mean age of 58.4 ± 12.7 and mean BMI of 30.6 ± 6.08. Two-level patients (N=34) were 58.8% female with mean age of 49.3 ±10.9 and mean BMI of 30.1 ± 5.82. Kinematic fusion was achieved in 97.4% of one-level patients and 100% of two-level patients. Baseline comorbidities were present in 89.5% of one-level patients and 88.2% of two-level patients. No adverse events related to BAS were reported in this study.

CONCLUSION

Fusion status is evaluated with many different biologics and varying methods in the literature. BAS with allograft in this study demonstrated high fusion rates with no complications within a largely comorbid population. Although a small population, BAS with allograft results were encouraging for one and two-level lumbar interbody fusion in this study. Further prospective studies should be conducted to investigate safety and efficacy in a larger population.

Tissue engineering advances in spine surgery

Autograft, while currently the gold standard for bone grafting, has several significant disadvantages including limited supply, donor site pain, hematoma formation, nerve and vascular injury, and fracture. Bone allografts have their own disadvantages including reduced osteoinductive capability, lack of osteoprogenitor cells, immunogenicity and risk of disease transmission. Thus demand exists for tissue-engineered constructs that can produce viable bone while avoiding the complications associated with human tissue grafts. This review will focus on recent advancements in tissue-engineered bone graft substitutes utilizing nanoscale technology in spine surgery applications. An evaluation will be performed of bone graft substitutes, biomimetic 3D scaffolds, bone morphogenetic protein, mesenchymal stem cells and intervertebral disc regeneration strategies.

Comparison of clinical and radiographic results between isobar posterior dynamic stabilization and posterior lumbar inter-body fusion for lumbar degenerative disease: A four-year retrospective study

PURPOSE

A retrospective study was conducted to compare clinical outcome with radiographic data and clinical complications between isobar posterior dynamic stabilization (IPDS, Scient'x, France) and posterior lumbar inter-body fusion (PLIF) for lumbar degenerative disease.

METHODS

113 consecutive patients (IPDS group, N=62; PLIF group, N=51) with lumbar degenerative disease were operated on between March 2009 and November 2011. Patient charts, radiographic films and medical records were reviewed. Clinical outcomes including the visual analog scale (VAS), Oswestry disability index (ODI) scores, and radiographic outcomes, including disk height index (DHI) and range of motion (ROM) were retrospectively analyzed.

RESULTS

The ODI and VAS leg and back pain scores in two groups were significantly improved at 6 and, 24 months and at the final follow-up (all, P<0.05). The degree of improvements in the ODI and VAS back pain scores, the incidence of complications and the rate of adjacent segment degeneration were similar in both groups (P>0.05). However, operation times and blood loss were significantly reduced in the IPDS group (P<0.05).

CONCLUSION

In summary, with similar symptoms improvement and complication rates, the results of this study demonstrate that IPDS is an effective and safe treatment for lumbar degenerative disease. There is currently insufficient evidence to indicate that the IPDS can avoid adjacent segment degeneration therefore, it is essential to conduct prospective, randomized, controlled multicenter studies with larger sample size and longer follow-up.

Mesenchymal stem cells in regenerative medicine for musculoskeletal diseases: bench, bedside, and industry

Human bone marrow-derived mesenchymal stem cells (MSCs) can self-renew and differentiate into osteoblasts, chondrocytes, and adipocytes. MSCs have effectively emerged as a promising tool for clinical applications, specifically in musculoskeletal diseases. This article reviews the status of preclinical animal studies, clinical trials, and the efforts of the industry in using MSCs to treat musculoskeletal diseases such as bone fractures, bone defects, focal chondral lesions, osteoarthritis, spinal diseases, and tendon injuries. We also discuss the current problems encountered and potential of using MSCs in future clinical studies.

Cellular bone matrices: viable stem cell-containing bone graft substitutes

BACKGROUND CONTEXT

Advances in the field of stem cell technology have stimulated the development and increased use of allogenic bone grafts containing live mesenchymal stem cells (MSCs), also known as cellular bone matrices (CBMs). It is estimated that CBMs comprise greater than 17% of all bone grafts and bone graft substitutes used.

PURPOSE

To critically evaluate CBMs, specifically their technical specifications, existing published data supporting their use, US Food and Drug Administration (FDA) regulation, cost, potential pitfalls, and other aspects pertaining to their use.

STUDY DESIGN

Areview of literature.

METHODS

A series of Ovid, Medline, and Pubmed-National Library of Medicine/National Institutes of Health (www.ncbi.nlm.nih.gov) searches were performed. Only articles in English journals or published with English language translations were included. Level of evidence of the selected articles was assessed. Specific technical information on each CBM was obtained by direct communication from the companies marketing the individual products.

RESULTS

Five different CBMs are currently available for use in spinal fusion surgery. There is a wide variation between the products with regard to the average donor age at harvest, total cellular concentration, percentage of MSCs, shelf life, and cell viability after defrosting. Three retrospective studies evaluating CBMs and fusion have shown fusion rates ranging from 90.2% to 92.3%, and multiple industry-sponsored trials are underway. No independent studies evaluating spinal fusion rates with the use of CBMs exist. All the commercially available CBMs claim to meet the FDA criteria under Section 361, 21 CFR Part 1271, and are not undergoing FDA premarket review. The CBMs claim to provide viable MSCs and are offered at a premium cost. Numerous challenges exist in regard to MSCs' survival, function, osteoblastic potential, and cytokine production once implanted into the intended host.

CONCLUSIONS

Cellular bone matrices may be a promising bone augmentation technology in spinal fusion surgery. Although CBMs appear to be safe for use as bone graft substitutes, their efficacy in spinal fusion surgery remains highly inconclusive. Large, nonindustry sponsored studies evaluating the efficacy of CBMs are required. Without results from such studies, surgeons must be made aware of the potential pitfalls of CBMs in spinal fusion surgery. With the currently available data, there is insufficient evidence to support the use of CBMs as bone graft substitutes in spinal fusion surgery.

Osteocel Plus cellular allograft in anterior cervical discectomy and fusion: evaluation of clinical and radiographic outcomes from a prospective multicenter study

STUDY DESIGN

Prospective, multicenter, nonrandomized, institutional review board-approved clinical and radiographic study.

OBJECTIVE

To evaluate and summarize the 2-year outcomes of patients treated with Osteocel Plus cellular allograft as part of an anterior cervical discectomy and fusion procedure.

SUMMARY OF BACKGROUND DATA

Osteocel Plus is an allograft cellular bone matrix containing native mesenchymal stem cells and osteoprogenitor cells that is intended to mimic the performance of iliac crest autograft without the morbidity associated with its harvest.

METHODS

A total of 182 patients were treated with anterior cervical discectomy and fusion using Osteocel Plus in a polyetheretherketone cage and anterior plating at 1 or 2 consecutive levels. Clinical outcomes included visual analogue scale for neck and arm pain, neck disability index, and SF-12 physical and mental component scores. Computed tomography and plain film radiographic measures included assessment of bridging bone, disc height, disc angle, and segmental range of motion.

RESULTS

A total of 249 levels were treated in 182 patients. Mean procedure time was 100 minutes, blood loss was less than 50 mL in 93% of patients, and hospital stay was 1 day or less in 84% of patients. Significant (P<0.05) average improvements in clinical outcomes from preoperatively to 24 months included the following: neck disability index: 21.5%; visual analogue scale neck: 34 mm; visual analogue scale arm: 35 mm; SF-12 physical component score: 11.2; SF-12 mental component score: 6.8. At 24 months, 93% of patients were satisfied with their outcome. In patients treated at a single level with a minimum of 24-month follow-up, 92% (79/86) of levels achieved solid bridging and 95% of levels demonstrated range of motion of less than 3°. In combined single- and 2-level procedures, 87% (157/180) of levels achieved solid bridging and 92% (148/161) had range of motion of less than 3° at 24 months. No patient required revision for pseudarthrosis.

CONCLUSION

Improvements in clinical results at 2 years, high patient satisfaction, and high radiographic and clinical fusion rates provide confidence in Osteocel Plus as an effective alternative to structural allograft or autograft in anterior cervical discectomy and fusion procedures.

LEVEL OF EVIDENCE

4.

Multipotential stromal cell abundance in cellular bone allograft: comparison with fresh age-matched iliac crest bone and bone marrow aspirate

AIM

To enumerate and characterize multipotential stromal cells (MSCs) in a cellular bone allograft and compare with fresh age-matched iliac crest bone and bone marrow (BM) aspirate.

MATERIALS & METHODS

MSC characterization used functional assays, confocal/scanning electron microscopy and whole-genome microarrays. Resident MSCs were enumerated by flow cytometry following enzymatic extraction.

RESULTS

Allograft material contained live osteocytes and proliferative bone-lining cells defined as MSCs by phenotypic and functional capacities. Without cultivation/expansion, the allograft displayed an 'osteoinductive' molecular signature and the presence of CD45(-)CD271(+)CD73(+)CD90(+)CD105(+) MSCs; with a purity over 100-fold that of iliac crest bone. In comparison with BM, MSC numbers enzymatically released from 1 g of cellular allograft were equivalent to approximately 45 ml of BM aspirate.

CONCLUSION

Cellular allograft bone represents a unique nonimmune material rich in MSCs and osteocytes. This osteoinductive graft represents an attractive alternative to autograft bone or composite/synthetic grafts in orthopedics and broader regenerative medicine settings.

Mesenchymal stem cells derived from vertebrae (vMSCs) show best biological properties

PURPOSE

Due to their properties and characteristics human mesenchymal stem cells (MSCs) appear to have great therapeutic potential. Many different populations of MSCs have been described and to understand whether they have equivalent biological properties is a critical issue for their therapeutic application.

METHODS

We proposed to analyze the in vitro growth kinetics of MSCs derived from different body sites (iliac crest bone marrow, vertebrae bone marrow, colon mucosa, dental pulp).

RESULTS

Mesenchymal stem cells derived from vertebrae can be maintained in culture for a greater number of steps and they also generate mature cells of all mesenchymal lineages with greater efficiency, when induced into osteogenic, adipogenic and chondrogenic differentiation.

CONCLUSIONS

The ability of vertebrae-derived MSCs in terms of expansion and differentiation is very interesting at the light of a clinical application for bone fusion in spine surgery.