Healos and bone marrow aspirate used for lumbar spine fusion: a case controlled study comparing healos with autograft

The Role of Bioceramics for Bone Regeneration: History, Mechanisms, and Future Perspectives

Osteoporosis is a skeletal disorder marked by compromised bone integrity, predisposing individuals, particularly older adults and postmenopausal women, to fractures. The advent of bioceramics for bone regeneration has opened up auspicious pathways for addressing osteoporosis. Research indicates that bioceramics can help bones grow back by activating bone morphogenetic protein (BMP), mitogen-activated protein kinase (MAPK), and wingless/integrated (Wnt)/β-catenin pathways in the body when combined with stem cells, drugs, and other supports. Still, bioceramics have some problems, such as not being flexible enough and prone to breaking, as well as difficulties in growing stem cells and discovering suitable supports for different bone types. While there have been improvements in making bioceramics better for healing bones, it is important to keep looking for new ideas from different areas of medicine to make them even better. By conducting a thorough scrutiny of the pivotal role bioceramics play in facilitating bone regeneration, this review aspires to propel forward the rapidly burgeoning domain of scientific exploration. In the end, this appreciation will contribute to the development of novel bioceramics that enhance bone regrowth and offer patients with bone disorders alternative treatments.

Iliac crest bone graft versus cell-based grafts to augment spinal fusion: a systematic review and meta-analysis

INTRODUCTION

Despite successful fusion rates with iliac crest bone graft (ICBG), donor-site morbidity and increased operating time remain a considerable limitation and drive the search for alternatives. In this systematic review, grafts with additional cellular supplementation were compared with ICBG for spinal arthrodesis. We compared safety, efficacy and long-term outcomes, thus providing the current and relevant evidence for orthopaedic surgeons to make informed choices regarding this rapidly developing field.

METHODS

An electronic literature search was conducted according to the PRISMA guidelines by two independent reviewers for articles published up to 1st March 2023 using PubMed, EMBASE and the Cochrane Central Register of Controlled Trial. Cellular allografts were not included. The following data were extracted: Number of patients, type of graft, fusion assessment method, follow-up duration, fusion rates, clinical outcomes and complications. The methodological quality of evidence (MQOE) was assessed using the Risk of Bias 2 (RoB-2) tool and Risk of Bias In Non-Randomised Studies (ROBINS) tool developed by Cochrane for evaluating bias in randomised and non-randomised studies.

RESULTS

Ten studies fulfiled the inclusion criteria, including 465 patients. The mean number of patients per study was 43.8 (std dev. 28.81, range 12-100). Two studies demonstrated cell-based therapy to be significantly more successful in terms of fusion rates compared to ICBG. However, the remaining eight demonstrated equivocal results. No study found that cell-based therapy was inferior. No difference was seen between the two groups in three studies who focused on degenerative cohorts. No difference in functional outcome scores was seen between the groups. A number of different preparation techniques for cell-based grafts were used throughout the studies.

CONCLUSION

Cell-based therapy offers a promising alternative to ICBG in spinal fusion surgery, which could help reduce the associated morbidity to patients. This review found that cell-based therapy is non-inferior to iliac crest bone graft and may offer patients an alternative treatment option with fewer complications and reduced post-operative pain. However, the literature to date is limited by heterogeneity of the cell preparation and grafting process. Future research with a unified approach to the cell preparation process is required to fully delineate the potential advantages of this technology.

Using a developed co-culture device to evaluate the proliferation of bone marrow stem cells by stimulation with platelet-rich plasma and electromagnetic field

BACKGROUNDS

Bone marrow stem cell can differentiate to osteoblast by growth factors, pulsed low-intensity ultrasound and electric magnetic field. In the research, bone marrow stem cells were cultured; bone marrow stem cells in culture can be stimulated by platelet-rich plasma and electric field.

METHODS

The culture well of the co-cultivation device has a radius of 7.5 mm and a depth of 7 mm. It is divided into two sub-chambers separated by a 3 mm high and 1 mm wide barrier. The bone marrow stem cells were seeded at a density of 2 × 104 cells and the medium volume was 120μl. Platelet-rich plasma (PRP) or platelet-poor plasma (PPP) was added to the other sub-chamber at a volume of 10μl. The bone marrow stem cells were subjected to different electric fields (0 ~ 1 V/cm) at a frequency of 70 kHz for 60 min.

RESULTS

The highest osteogenic capacity of bone marrow stem cells was achieved by addition of PRP to electric field stimulation (0.25 V/cm) resulted in a proliferation rate of 599.78%. In electric field stimulation (0.75 V/cm) with PPP, the proliferation rate was only 10.46%.

CONCLUSIONS

Bone marrow stem cell with PRP in the co-culture device combined with electric field at 0.25 V/cm strength significantly promoted the growth of bone marrow stem cells.

Application of nano-hydroxyapatite matrix graft in inter-vertebral fusion therapy: a meta-analysis

OBJECTIVE

Nano-hydroxyapatite and its composites(nHA) have been widely used as grafts in inter-vertebral fusion. However, the safety and efficacy of the graft in inter-vertebral fusion is controversial. This meta-analysis aimed at evaluating the safety and efficacy of nHA and non-hydroxyapatite grafts (noHA) (autologous bone, etc.) in inter-body fusion.

MATERIALS AND METHODS

A comprehensive search was performed in electronic database as follows: PubMed, EMBASE, the Cochrane Library, Web of Science, and China National Knowledge Internet (CNKI) from inception until October 2022. Clinical studies on the effect of nHA and noHA in spinal fusion were collected. Analysis of outcome indicators using RevMan 5.4 statistical software.

RESULTS

The meta-analysis showed that the operation time of patients who underwent inter-body fusion with nHA grafts was less than that of patients who underwent noHA (p < 0.05). Compared with the noHA group, the nHA group can achieve similar clinical effects in the fusion rate(OR = 1.29,95%CI: 0.88 to 1.88,p = 0.19),Subsidence rate(OR = 1.2,95%CI:0.44 to 3.28,p = 0.72), inter-vertebral space height(SMD = 0.04,95%CI:-0.08 to 0.15,p = 0.54),Cobb angle(SMD = 0.21,95%CI: 0.18 to 0.6,p = 0.21),Blood loss(SMD = -36.58,95%CI: -81.45 to 8.29,p = 0.11),operative time in 12 months(SMD = -5.82,95%CI: -9.98 to -1.67,p = 0.006) and in the final follow-up(SMD = -0.38,95%CI: -0.51 to -0.26,p < 0.00001),ODI(SMD = 0.68,95%CI: -0.84 to 2.19,p = 0.38), VAS(SMD = 0.17,95%CI: -0.13 to 0.48,p = 0.27) and adverse events(OR = 0.98,95%CI: 0.66 to 1.45,p = 0.92), and the differences are not statistically significant.

CONCLUSION

This meta-analysis suggests that nHA matrix grafts are similar to noHA grafts in the safety and efficacy of spinal reconstruction, and are an ideal material for inter-vertebral bone grafting.

Comparison of proliferation and osteogenic differentiation potential of bovine adipose tissue and bone marrow derived stem cells

Bone marrow derived stem cells (BMSC) are the most utilized cell type in the field of bone regeneration. Although BMSC are both safe and efficacious, the search for alternative sources for stem cells continues. We investigated bovine BMSC and adipose tissue derived mesenchymal stem cells (ATSC) using immunofluorescence and PCR. We further compared the osteogenic differentiation potentials of both sources of stem cells. We assessed alkaline phosphatase (ALP) enzyme levels and calcium deposition in differentiating cells at days 7, 14 and 21 to compare the osteogenic differentiation capability of both cell types. We found that ATSC expressed significantly higher ALP levels compared to BMSC throughout osteogenic differentiation. Calcium deposition was greater in ATSC than BMSC at days 7 and 14. By the end of day 21, BMSC produced greater calcium deposition. We found that ATSC undergo osteogenic differentiation more rapidly than BMSC, but BMSC provide greater mineralization over longer periods.

Scaffold Guided Bone Regeneration for the Treatment of Large Segmental Defects in Long Bones

Bone generally displays a high intrinsic capacity to regenerate. Nonetheless, large osseous defects sometimes fail to heal. The treatment of such large segmental defects still represents a considerable clinical challenge. The regeneration of large bone defects often proves difficult, since it relies on the formation of large amounts of bone within an environment impedimental to osteogenesis, characterized by soft tissue damage and hampered vascularization. Consequently, research efforts have concentrated on tissue engineering and regenerative medical strategies to resolve this multifaceted challenge. In this review, we summarize, critically evaluate, and discuss present approaches in light of their clinical relevance; we also present future advanced techniques for bone tissue engineering, outlining the steps to realize for their translation from bench to bedside. The discussion includes the physiology of bone healing, requirements and properties of natural and synthetic biomaterials for bone reconstruction, their use in conjunction with cellular components and suitable growth factors, and strategies to improve vascularization and the translation of these regenerative concepts to in vivo applications. We conclude that the ideal all-purpose material for scaffold-guided bone regeneration is currently not available. It seems that a variety of different solutions will be employed, according to the clinical treatment necessary.

Comparison of Fusion Rate and Functional Outcome Between Local Cancellous Bone Plus Demineralized Bone Matrix and Local Bone in 1-Level Posterior Lumbar Interbody Fusion

STUDY DESIGN

Retrospective study with prospectively collected data.

OBJECTIVE

The purpose of this study is to investigate the difference in fusion rate and clinical outcome of patients with local bone as filler for the graft and demineralized bone matrix (DBM) plus only the cancellous bone from local bone as a filler for cage in 1-level posterior lumbar interbody fusion (PLIF) with cage.

SUMMARY OF BACKGROUND DATA

Cancellous bone is more advantageous than cortical bone in the local bone for improving bone formation in spine fusion surgery. There are little studies on the difference in fusion rate and reduction of fusion time using only these cancellous bones.

METHODS

Of the 40 patients who underwent 1-level PLIF using cage, 20 patients in group A used local bone and 20 patients in group B used mixture of cancellous bone extracted separately from local bone and commercially available DBM as filler for cage. Changes in fusion rate and intervertebral spacing were measured using lateral radiography, and fusion was determined as nonunion using the Brantigan-Steffee classification. The clinical outcome was evaluated.

RESULTS

There was no difference in height change over time between the two groups. Regarding union grade, group B showed better union grade than group A. However, no difference in union grade change over time was observed between the 2 groups. In group B, Oswestry Disability Index (ODI), Rolland-Morris Disability Questionnaire (RMDQ), and SF-36 mental component score (MCS) significantly decreased, but there was no difference in change over time.

CONCLUSIONS

In 1-level PLIF for degenerative lumbar disease, better fusion rate was observed in the group that used only cancellous bone from local bone plus DBM than that in the group that used local bone; however, there was no difference in fusion grade change over time in the 2 groups.

Comparing the efficacy of adipose-derived and bone marrow-derived cells in a rat model of posterolateral lumbar fusion

Although bone marrow-derived mesenchymal stem cells (BMCs) have been widely used in spinal fusion procedures, adipose-derived stem cells (ASCs) offer a number of advantages as an alternative clinical cell source. This study directly compares the efficacy of ASCs and BMCs from the same donor animals to achieve successful fusion when combined with a clinical-grade bone graft substitute in a rat lumbar fusion model. ASCs and BMCs were isolated from the same Lewis donor rats and grown to passage 2 (P2). Single-level bilateral posterolateral intertransverse process lumbar fusion surgery was performed on syngeneic rats divided into three experimental groups: clinical-grade bone graft substitute alone (CBGS); CBGS+ rat ASCs (rASC); and, CBGS+ rat BMCs (rBMC). Eight weeks postoperatively, fusion was evaluated via micro-CT, manual palpation and histology. In vitro analysis of the osteogenic capacity of rBMCs and rASCs was also performed. Results indicated that the average fusion volume in the rASC group was the largest and was significantly larger than the CBGS group. Although the rASC group displayed the highest fusion rates via micro-CT and manual palpation, this difference was not statistically significant. Cell-seeded grafts showed more histological bone formation than cell-free grafts. P2 rASCs and rBMCs displayed similar in vitro osteogenic differentiation capacities. Overall, this study showed that, when combined with a clinical-grade bone graft substitute in a rat model, rASCs cells yielded the largest fusion masses and comparable fusion results to rBMCs. These results add to growing evidence that ASCs provide an attractive alternative to BMCs for spinal fusion procedures.

Hydroxyapatite/collagen composite graft for posterior lumbar interbody fusion: a comparison with local bone graft

Background

Autologous bone has been used for posterior lumbar intervertebral fusion (PLIF). However, harvesting autologous bone graft is associated with donor site complications. We previously developed a hydroxyapatite/collagen (HAp/Col) composite as an osteoconductive artificial bone, characterized by having a highly porous structure with sponge‐like elasticity. This study aims to investigate the effectiveness of HAp/Col composite with bone marrow aspirate (BMA) as a graft substitute in PLIF for the treatment of lumbar spinal diseases.

Methods

This study prospectively investigated patients who received one-level PLIF. For the interbody fusion, two titanium cages were inserted. On the one side of interbody space, HAp/Col composite incorporated with BMA filling the titanium cage was grafted. On the other side, local bone graft (LBG) harvested during decompressive laminotomy was grafted and then one-level instrumentation using pedicle screws was performed. The target levels were at L2/3 in 2 cases, L3/4 in 3 cases, L4/5 in 36 cases, and L5/S in 5 cases. We evaluated clinical symptoms and radiological outcomes of 46 patients and compared the fusion status of HAp/Col composite with that of LBG.

Results

The 1-year postoperative CT evaluation demonstrated that, in the HAp/Col, a complete fusion was observed in 38 patients (82.6%), whereas in the LBG, a complete fusion was observed in 35 patients (76.1%). There were no statistical differences between the HAp/Col and LBG. In the HAp/Col, incomplete fusion was observed in five patients (10.9%) and non-fusion in two patients (4.3%), and in the LBG, incomplete fusion was observed in nine patients (19.6%) and non-fusion in two patients (4.3%). At 2 years after the surgery, complete fusion increased to 44 patients (95.7%) in the HAp/Col and 41 patients (89.1%) in the LBG. There were no significant differences in the clinical scores for lumbar spine between patients with fusion and non-fusion.

Conclusions

The HAp/Col composite with BMA in the titanium cage can be effectively used as an alternative to conventional autologous LBG for intervertebral spinal fusion.

Trial registration University hospital Medical Information Network, UMIN000045010, July 30th, 2021, Retrospectively registered, https://www.umin.ac.jp/english/.

Use of Autologous Stem Cells in Lumbar Spinal Fusion: A Systematic Review of Current Clinical Evidence

STUDY DESIGN

Systematic review.

OBJECTIVES

To systematically review, critically appraise and synthesize evidence on use of autologous stem cells sources for fusion in the lumbar spine.

METHODS

A systematic search of PubMed/MEDLINE, EMBASE and ClinicalTrials.gov through February 20, 2020 was conducted comparing autologous cell grafts to other biologics for lumbar spine fusion. The focus was on studies comparing distinct patient groups.

RESULTS

From 343 potentially relevant citations, 15 studies met the inclusion criteria set a priori. Seven studies compared distinct patient groups, with BMA being used in combination with allograft or autograft not as a standalone material. No economic evaluations were identified. Most observational studies were at moderately high risk of bias. When used for primary lumbar fusion, no statistical differences in outcomes or complications were seen between BMA+autograft/or +allograft compared to autograft/allograft alone. Compared with allograft, data from a RCT suggested statistically better fusion and lower complication rates with concentrated BMA+allograft. When used in revisions, no differences in outcomes were seen between BMA+allograft and either autograft or rh-BMP-2 but fusion rates were lower with BMA+allograft, leading to additional revision surgery.

CONCLUSIONS

There was substantial heterogeneity across studies in patient populations, sample size, biologic combinations, and surgical characteristics making direct comparisons difficult. The overall quality of evidence for fusion rates and the safety of BMA in lumbar fusion procedures was considered very low, with studies being at moderately high or high risk of bias.

The Effect of Mesenchymal Stem Cell-Enriched Scaffolds on MMP-8 and TGF-β Levels of Vertebrae Postlaminoplasty in Rabbit Model

INTRODUCTION

Some laminoplasty procedures still have restenosis because of bony-bridging failure of the laminar hinge. The present study aimed to determine the effect of mesenchymal stem cell (MSC)-enriched scaffolds on vertebral regeneration after laminoplasty on the basis of the number of osteoblasts, matrix metalloproteinase-8 (MMP-8), and transforming growth factor-beta (TGF-β) levels.

METHODS

Laminoplasty procedure using the Hirabayashi technique was conducted at the lumbar level in 32 rabbits that were divided into four and three groups of the control (C) and treatment groups, respectively, with different types of laminoplasty spacer (T1, autograft; T2, scaffold; and T3, scaffold with MSCs). Histopathological studies were conducted to calculate the number of osteoblasts and enzyme-linked immunosorbent assay tests to detect MMP-8 and TGF-β 4 weeks after the surgery.

RESULTS

The results showed a significant decrease in MMP-8 level in the T3 group compared with that in the control group (p < 0.05). A significant difference exists between the average number of newly formed osteoblasts in the control group compared with that in the T3 group (p < 0.05) with a higher mean blood TGF-β level of all experimental groups compared with that of the control group (p = 0.58).

CONCLUSION

The significant decrease in MMP-8 levels, increase in TGF-β levels, and increased number of osteoblasts on MSC-seeded polylactic acid scaffolds could be useful to support the laminoplasty procedure to prevent restenosis because it was biocompatible and promoted the bone healing process.

Comparison of Freshly Isolated Adipose Tissue-derived Stromal Vascular Fraction and Bone Marrow Cells in a Posterolateral Lumbar Spinal Fusion Model

STUDY DESIGN

Rat posterolateral lumbar fusion model.

OBJECTIVE

The aim of this study was to compare the efficacy of freshly isolated adipose tissue-derived stromal vascular fraction (A-SVF) and bone marrow cells (BMCs) cells in achieving spinal fusion in a rat model.

SUMMARY OF BACKGROUND DATA

Adipose tissue-derived stromal cells (ASCs) offer advantages as a clinical cell source compared to bone marrow-derived stromal cells (BMSCs), including larger available tissue volumes and reduced donor site morbidity. While pre-clinical studies have shown that ex vivo expanded ASCs can be successfully used in spinal fusion, the use of A-SVF cells better allows for clinical translation.

METHODS

A-SVF cells were isolated from the inguinal fat pads, whereas BMCs were isolated from the long bones of syngeneic 6- to 8-week-old Lewis rats and combined with Vitoss (Stryker) bone graft substitute for subsequent transplantation. Posterolateral spinal fusion surgery at L4-L5 was performed on 36 female Lewis rats divided into three experimental groups: Vitoss bone graft substitute only (VO group); Vitoss + 2.5 × 106 A-SVF cells/side; and, Vitoss + 2.5 × 106 BMCs/side. Fusion was assessed 8 weeks post-surgery via manual palpation, micro-computed tomography (μCT) imaging, and histology.

RESULTS

μCT imaging analyses revealed that fusion volumes and μCT fusion scores in the A-SVF group were significantly higher than in the VO group; however, they were not significantly different between the A-SVF group and the BMC group. The average manual palpation score was highest in the A-SVF group compared with the BMC and VO groups. Fusion masses arising from cell-seeded implants yielded better bone quality than nonseeded bone graft substitute.

CONCLUSION

In a rat model, A-SVF cells yielded a comparable fusion mass volume and radiographic rate of fusion to BMCs when combined with a clinical-grade bone graft substitute. These results suggest the feasibility of using freshly isolated A-SVF cells in spinal fusion procedures.Level of Evidence: N/A.

Synthetic Bone Graft Materials in Spine Fusion: Current Evidence and Future Trends

Historically, iliac crest bone autograft has been considered the gold standard bone graft substitute for spinal fusion. However, the significant morbidity associated with harvesting procedures has influenced decision-making and practice patterns. To minimize these side effects, many clinicians have pursued the use of bone graft extenders to minimize the amount of autograft required for fusion in certain applications. Synthetic materials, including a variety of ceramic compounds, are a class that has been studied extensively as bone graft extenders. These have been used in combination with a wide array of other biomaterials and investigated in a variety of different spine fusion procedures. This review will summarize the current evidence of different synthetic materials in various spinal fusion procedures and discuss the future of novel synthetics.

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.

In vitro characterization of xeno-free clinically relevant human collagen and its applicability in cell-laden 3D bioprinting

Collagen type I, commonly derived from xenogenic sources, is extensively used as a biomaterial for tissue engineering applications. However, the use of xenogenic collagen is typically associated with species specific variation in mechanical, structural, and biological properties that are known to influence cellular response and remodeling. In addition, immunological complications and risks of disease transmission are also major concerns. The goal of this study is to characterize a new xeno-free human skin-derived collagen and assess its applicability as a bioink for cell-laden 3 D bioprinting. Four different concentrations of human collagen (i.e., 0.5 mg/mL, 1 mg/mL, 3 mg/mL and 6 mg/mL) were employed for the synthesis of collagen hydrogels. In addition, bovine collagen was used as a xenogenic control. Results from SDS-PAGE analysis showed the presence of α1, α2, and β chains, confirming that the integrity of type I human collagen is maintained post isolation. Polymerization rate and compressive modulus increased significantly with increase in the concentration of human collagen. When comparing two different sources of collagen, the polymerization rate of xenogenic collagen was significantly faster (p < 0.05) than human collagen while the compressive modulus was comparable. Raman spectroscopy showed a large peak in the Amide I band around 1600 cm^-1, indicating a dense and supraorganized fibrillar structure in human collagen hydrogels. Conversely, Amide I band intensity for xenogenic collagen was comparable to that of Amide II and Amide III bands. Further, the use of 6 mg/mL human collagen as a bioink yielded 3 D printed constructs with high shape fidelity and cell viability. On the other hand, xenogenic collagen failed to yield stable 3 D printed constructs. Together, the results from this study provides an impetus for using human-derived collagen as a viable alternative to xenogenic sources for 3 D bioprinting of clinically relevant scaffolds for tissue engineering applications.

The Few Who Made It: Commercially and Clinically Successful Innovative Bone Grafts

Bone reconstruction techniques are mainly based on the use of tissue grafts and artificial scaffolds. The former presents well-known limitations, such as restricted graft availability and donor site morbidity, while the latter commonly results in poor graft integration and fixation in the bone, which leads to the unbalanced distribution of loads, impaired bone formation, increased pain perception, and risk of fracture, ultimately leading to recurrent surgeries. In the past decade, research efforts have been focused on the development of innovative bone substitutes that not only provide immediate mechanical support, but also ensure appropriate graft anchoring by, for example, promoting de novo bone tissue formation. From the countless studies that aimed in this direction, only few have made the big jump from the benchtop to the bedside, whilst most have perished along the challenging path of clinical translation. Herein, we describe some clinically successful cases of bone device development, including biological glues, stem cell-seeded scaffolds, and gene-functionalized bone substitutes. We also discuss the ventures that these technologies went through, the hindrances they faced and the common grounds among them, which might have been key for their success. The ultimate objective of this perspective article is to highlight the important aspects of the clinical translation of an innovative idea in the field of bone grafting, with the aim of commercially and clinically informing new research approaches in the sector.

Fusion rates support wired allograft combined with instrumented craniocervical fixation in the paediatric population

Background

Occipitocervical and atlantoaxial instability in the pediatric population is a rare and challenging condition to treat. Variable surgical techniques have been employed to achieve fusion. The study aimed to assess bony fusion with rigid craniocervical fixation using an allograft bone block to serve as scaffold for bony fusion.

Methods

This is a single center case series from a tertiary referral neurosurgical center. The series includes 12 consecutive pediatric patients with rigid craniocervical fusion between 2006 and 2014. The primary outcome was bony fusion as assessed by computed tomography and flexion-extension radiographs. The authors did not receive external funding for this study.

Results

Twelve patients (age 1–15 years) were operated with a median imaging follow-up time of 22 months (range 6–69 m). A modified Gallie fusion technique with a tightly wired allograft bone block was used in 10 of 13 procedures. One patient underwent re-fixation due to screw breakage. Eleven out of 13 procedures resulted in a stable construct with bony fusion. All 10 patients operated with the modified Gallie fusion technique with sublaminar wiring of allograft bone block had bony fusion. No post-operative complications of the posterior fixation procedure were noted.

Conclusions

The modified Gallie fusion technique with allograft bone block without post-operative immobilization achieved excellent fusion. We conclude there is no need to use autograft or BMPs in craniocervical fusion in the pediatric population, which avoids related donor-site morbidity.

Level of evidence

Level IV—case series; therapeutic.

Effect of strontium substituted ß-TCP associated to mesenchymal stem cells from bone marrow and adipose tissue on spinal fusion in healthy and ovariectomized rat

Despite alternatives to autogenous bone graft for spinal fusion have been investigated, it has been shown that osteoconductive materials alone do not give a rate of fusion comparable with autogenous bone. This study analyzed a strontium substituted ß-tricalcium phosphate (Sr-ßTCP) associated with syngeneic, unexpanded, and undifferentiated mesenchymal stem cells from bone marrow (BMSC) or adipose tissue (ADSC) as a new tissue engineering approach for spinal fusion procedures. A posterolateral fusion was performed in 15 ovariectomized (OVX) and 15 sham-operated (SHAM) Inbred rats. Both SHAM and OVX animals were divided into three groups: Sr-ßTCP, Sr-ßTCP + BMCSs, and Sr-ßTCP + ADSCs. Animals were euthanized 8 weeks after surgery and the spines evaluated by manual palpation, micro-CT, and histology. For both SHAM and OVX animals, the fusion tissue in the Sr-ßTCP + BMSCs group was more solid. This effect was significantly higher in OVX animals by comparing the Sr-ßTCP + BMCSs group with Sr-ßTCP + ADSCs. Radiographical score, based on micro-CT 2D image, highlighted that the Sr-ßTCP + BMCSs group presented a similar fusion to Sr-ßTCP and higher than Sr-ßTCP + ADSCs in both SHAM and OVX animals. Micro-CT 3D parameters did not show significant differences among groups. Histological score showed significantly higher fusion in Sr-ßTCP + BMSCs group than Sr-ßTCP and Sr-ßTCP + ADSCs, for both SHAM and OVX animals. In conclusion, our results suggest that addition of BMSCs to a Sr-ßTCP improve bone formation and fusion, both in osteoporotic and nonosteoporotic animal, whereas spinal fusion is not enhanced in rats treated with Sr-ßTCP + ADSCs. Thus, for conducting cells therapy in spinal surgery BMSCs still seems to be a better choice compared with ADSCs.

Autologous bone marrow clot as an alternative to autograft for bone defect healing

Objectives

Long bone defects often require surgical intervention for functional restoration. The ‘gold standard’ treatment is autologous bone graft (ABG), usually from the patient’s iliac crest. However, autograft is plagued by complications including limited supply, donor site morbidity, and the need for an additional surgery. Thus, alternative therapies are being actively investigated. Autologous bone marrow (BM) is considered as a candidate due to the presence of both endogenous reparative cells and growth factors. We aimed to compare the therapeutic potentials of autologous bone marrow aspirate (BMA) and ABG, which has not previously been done.

Methods

We compared the efficacy of coagulated autologous BMA and ABG for the repair of ulnar defects in New Zealand White rabbits. Segmental defects (14 mm) were filled with autologous clotted BM or morcellized autograft, and healing was assessed four and 12 weeks postoperatively. Harvested ulnas were subjected to radiological, micro-CT, histological, and mechanical analyses.

Results

Comparable results were obtained with autologous BMA clot and ABG, except for the quantification of new bone by micro-CT. Significantly more bone was found in the ABG-treated ulnar defects than in those treated with autologous BMA clot. This is possibly due to the remnants of necrotic autograft fragments that persisted within the healing defects at week 12 post-surgery.

Conclusion

As similar treatment outcomes were achieved by the two strategies, the preferred treatment would be one that is associated with a lower risk of complications. Hence, these results demonstrate that coagulated BMA can be considered as an alternative autogenous therapy for long bone healing.

Cite this article: Z. X. H. Lim, B. Rai, T. C. Tan, A. K. Ramruttun, J. H. Hui, V. Nurcombe, S. H. Teoh, S. M. Cool. Autologous bone marrow clot as an alternative to autograft for bone defect healing. Bone Joint Res 2019;8:107–117. DOI: 10.1302/2046-3758.83.BJR-2018-0096.R1.

Radiographic and CT Evaluation of Recombinant Human Bone Morphogenetic Protein-2-assisted Cervical Spinal Interbody Fusion

STUDY DESIGN

This was a retrospective study.

OBJECTIVE

To radiographically demonstrate the distinct fusion pattern of recombinant human bone morphogenetic protein-2 (rhBMP-2) in the setting of anterior cervical discectomy and fusion.

SUMMARY OF BACKGROUND DATA

Studies investigating spinal fusion assisted with rhBMP-2 have yielded promising results, suggesting rhBMP-2 is an efficacious alternative to iliac crest autografts. rhBMP-2-assisted spinal fusion both hastens healing and eliminates patient morbidity from iliac crest autograft. Unique to rhBMP-assisted spinal fusion is its distinct radiographic fusion pattern as fusion is achieved. Despite promising results and increased clinical use of rhBMP-2, there remains a paucity of literature documenting this radiographic process.

MATERIALS AND METHODS

This study included 26 patients who underwent single-level anterior cervical discectomy and fusion using rhBMP-2. All data used for this study was collected from a prior FDA Investigational Device Exemption study.

RESULTS

A polyetheretherketone cage was used as an interbody disk spacer in all 26 patients. Patients were evaluated between 2 and 6 weeks after surgery and subsequently at 3, 6, 12, and 24 months postoperative. All patients underwent plain radiography at every follow-up visit, and computed tomograhy evaluation was performed at 3, 6, 12, and 24 months as part of the study protocol. Earliest fusion was observed at 3 months in 38% of patients. Likely fusion was observed in all patients by 12 months postoperative.

CONCLUSIONS

rhBMP-2 leads to both successful interbody fusion and an enhanced fusion rate with unique imaging characteristics. Additional characteristics of BMP observed in 100% of patients included prevertebral soft-tissue swelling and early endplate resorption. Other common features included polyetheretherketone cage migration, heterotopic bone formation and cage subsidence.

Positive effect on spinal fusion by the combination of platelet-rich plasma and collagen-mineral scaffold using lumbar posterolateral fusion model in rats

Background

Platelet-rich plasma (PRP) is autologous in origin and contains a high concentration of platelets which is a source of various growth factors. Previous studies have suggested that PRP has a positive effect in accelerating fusion by an autologous bone graft in a lumbar fusion. The role of PRP on artificial bone grafts in spinal fusion remains controversial. In this study, positive effect on spinal fusion by PRP was hypothesized; in vitro and in vivo studies were designed to test this hypothesis.

Methods

PRP was produced from peripheral blood of Sprague-Dawley (SD) rats. A lumbar posterolateral arthrodesis model was used to test the efficacy of PRP on spinal fusion. Thirty SD rats were divided into three groups by different implants: the PRP group, PRP plus collagen-mineral carrier; the platelet-poor plasma (PPP) group, PPP plus collagen-mineral carrier; and the control group, collagen-mineral only. Spinal fusion was examined using plain radiographs, micro-computed tomography (micro-CT), manual palpation, and histological analysis. The fusion rate by micro-CT and that by manual palpation in groups were compared.

Results

In the micro-CT results, 16 fused segments were observed in the PRP group (80%, 16/20), 2 in the PPP group (10%, 2/20), and 2 in the control group (10%, 2/20). The fusion rate, determined by manual palpation, was 60% (6/10) in the PRP group, 0% (0/10) in the PPP group, and 0% (0/10) in the control group. Histology showed that the PRP group had more new bone and matured marrow formation.

Conclusions

The results of this study demonstrated that PRP on an artificial bone carrier had positive effects on lumbar spinal fusion in rats. In the future, this composite could be potentially used as a bone graft in humans.

An inception cohort study of patients in a military clinic treated for lower back pain with lumbar fusion and SIGNAFUSE® with a systematic review of the literature

Background: Use of synthetic bone graft substitutes for spinal fusion has increased sharply over the past 20 years. SIGNAFUSE® is one such synthetic graft material that provides an osteostimulatory effect for spinal fusion. Because clinical trials are not required for commercialization of synthetic bone graft substitutes in the United States, fusion rates attained using SIGNAFUSE for lumbar fusion are not well documented. The goal of the current study is to determine the rate of spinal fusion in a military clinic following lumbar fusion surgery augmented with SIGNAFUSE. Methods: We report a retrospective chart review of 8 patients who received lumbar spinal fusion surgery augmented with SIGNAFUSE. All patients were assessed by computed tomographic (CT) imaging at least 1-year post-surgery to determine whether bony fusion had occurred. We also systematically reviewed literature sources that report fusion rate following spinal fusion surgery, for broader context. Results: An average of 1.6 spinal levels were treated with SIGNAFUSE-loaded interbody cages. All patients had stabilization hardware via pedicle screws or integrated cage fixation. Seven of 8 patients successfully fused, for an overall fusion rate of 87.5% (95% confidence interval: 47.4% to 99.7%). Systematic review of 26 recent publications that included 1,126 patients treated with synthetic bone graft showed that the overall fusion rate in the literature is 84.4%. Conclusions: Fusion was achieved in 87.5% of patients treated with SIGNAFUSE. This is comparable to the fusion rate in a systematic review of 1,126 patients treated with synthetic bone graft materials.

A mouse model for the study of transplanted bone marrow mesenchymal stem cell survival and proliferation in lumbar spinal fusion

PURPOSE

Bone marrow aspirate has been successfully used alongside a variety of grafting materials to clinically augment spinal fusion. However, little is known about the fate of these transplanted cells. Herein, we develop a novel murine model for the in vivo monitoring of implanted bone marrow cells (BMCs) following spinal fusion.

METHODS

A clinical-grade scaffold was implanted into immune-intact mice undergoing spinal fusion with or without freshly isolated BMCs from either transgenic mice which constitutively express the firefly luciferase gene or syngeneic controls. The in vivo survival, distribution and proliferation of these luciferase-expressing cells was monitored via bioluminescence imaging over a period of 8 weeks and confirmed via immunohistochemistry. MicroCT imaging was performed 8 weeks to assess fusion.

RESULTS

Bioluminescence imaging indicated transplanted cell survival and proliferation over the first 2 weeks, followed by a decrease in cell numbers, with transplanted cell survival still evident at the end of the study. New bone formation and increased fusion mass volume were observed in mice implanted with cell-seeded scaffolds.

CONCLUSIONS

By enabling the tracking of transplanted bone marrow-derived cells during spinal fusion in vivo, this mouse model will be integral to developing a deeper understanding of the biological processes underlying spinal fusion in future studies. These slides can be retrieved under Electronic Supplementary Material.

Autologous cell-based therapy for treatment of large bone defects: from bench to bedside

OBJECTIVES

Reconstruction of long segmental bone defects is demanding for patients and surgeons, and associated with long-term treatment periods and substantial complication rates in addition to high costs. While defects up to 4-5 cm length might be filled up with autologous bone graft, heterologous bone from cadavers, or artificial bone graft substitutes, current options to reconstruct bone defects greater than 5 cm consist of either vascularized free bone transfers, the Masquelet technique or the Ilizarov distraction osteogenesis. Alternatively, autologous cell transplantation is an encouraging treatment option for large bone defects as it eliminates problems such as limited autologous bone availability, allogenic bone immunogenicity, and donor-site morbidity, and might be used for stabilizing loose alloplastic implants.

METHODS

The authors show different cell therapies without expansion in culture, with ex vivo expansion and cell therapy in local bone defects, bone healing and osteonecrosis. Different kinds of cells and scaffolds investigated in our group as well as in vivo transfer studies and BMC used in clinical phase I and IIa clinical trials of our group are shown.

RESULTS

Our research history demonstrated the great potential of various stem cell species to support bone defect healing. It was clearly shown that the combination of different cell types is superior to approaches using single cell types. We further demonstrate that it is feasible to translate preclinically developed protocols from in vitro to in vivo experiments and follow positive convincing results into a clinical setting to use autologous stem cells to support bone healing.

How stem cell composition in bone marrow aspirate relates to clinical outcomes when used for cervical spine fusion

Anterior cervical discectomy and fusion (ACDF) is performed to relieve pain caused by degenerative disk disease and nerve obstruction. As an alternative to bone graft, autologous concentrated bone marrow aspirate (CBMA) is used to achieve vertebral fusion with a satisfactory success rate. This has been attributed in part to bone marrow-resident mesenchymal stromal cells (MSCs) with the capacity to differentiate into osteoblasts and generate bone tissue. To date, there has been no study comparing cellular yields, MSC frequencies and their osteogenic potential with ACDF outcome. Patients (n = 24) received ACDF with CBMA and allograft bone matrix. Colony forming unit fibroblast (CFU-F) and CFU-osteoblasts (CFU-O) assays were performed on CBMA samples to enumerate MSCs (CFU-F) and osteogenic MSCs (CFU-O). CFUs were normalized to CBMA volume to define yield and also to mononuclear cells (MNC) to define frequency. After 1-year, fusion rates were good (86.7%) with pain and disability improved. There was a negative relationship between MNC and CFU-F measurements with age of patient and CFU-Os negatively correlated with age in females but not males. Tobacco use did not affect CBMA but was associated with poorer clinical outcome. Surprisingly, we found that while high-grade fusion was not associated with CFU-O, it correlated strongly (p<0.0067) with CBMA containing the lowest frequencies of CFU-F (3.0x10^-6–5.83x10^-5 CFU-F/MNC). MNC levels alone were not responsible for the results. These observations suggest that osteogenesis by human bone marrow is controlled by homeostatic ratio of MSCs to other cellular bone marrow components rather than absolute level of osteogenic MSCs, and that a lower ratio of MSCs to other cellular components in marrow tends to predict effective osteogenesis during ACDF. The results presented herein challenge the current dogma surrounding the proposed mechanism of MSCs in bone healing.

Mesenchymal Stem Cell Therapy for Bone Regeneration

Mesenchymal stem cells (MSCs) have been used in clinic for approximately 20 years. During this period, various new populations of MSCs have been found or manipulated. However, their characters and relative strength for bone regeneration have not been well known. For a comprehensive understanding of MSCs, we reviewed the literature on the multipotent cells ranging from the definition to the current research progress for bone regeneration. Based on our literature review, bone marrow MSCs have been most widely studied and utilized in clinical settings. Among other populations of MSCs, adipose-derived MSCs and perivascular MSCs might be potential candidates for bone regeneration, whose efficacy and safety still require further investigation.

Does Age Influence the Efficacy of Demineralized Bone Matrix Enriched with Concentrated Bone Marrow Aspirate in Lumbar Fusions?

STUDY DESIGN

Retrospective study.

OBJECTIVE

Evaluate the effect of age on the efficacy of allograft/demineralized bone matrix (DBM) enriched with concentrated bone marrow aspirate (BMA) in posterolateral lumbar fusions (PLFs).

SUMMARY OF BACKGROUND DATA

Cell-based therapies such as concentrated BMA have been developed as a potential alternative to iliac crest bone graft (ICBG). BMA contains mesenchymal stem cells (MSCs) and growth factors that can confer osteogenic and osteoinductive potential to osteoconductive scaffolds such as DBM/allograft. To date, no studies have examined the role of age on fusion outcomes when BMA is utilized despite the well-established deleterious effects of advanced age on bone marrow and MSC potential.

MATERIALS AND METHODS

Fifty-one patients that underwent PLF were divided into 3 groups. Group A (n=14) composed of patients age 65 years and older who received BMA with DBM. Group B (n=17) consisted of patients younger than 65 years of age who received BMA with DBM. Group C (n=20) composed of patients age 65 years and older who received ICBG. Fusion rates and clinical outcomes were assessed.

RESULTS

Fusion was significantly lower in group A (35.7%) compared with both groups B (76.4%) and C (80%) (A vs. B, P=0.03; A vs. C, P=0.01). There were no differences in clinical outcomes among all groups except for pseudarthrosis which occurred in 28.6% of patients in group A compared with none and 5% of patients in groups B and C, respectively (A vs. B, P=0.03; A vs. C, P=0.13).

CONCLUSIONS

Elderly patients undergoing PLF using DBM enriched with BMA achieved lower radiographic fusion success compared with their nonelderly counterparts and compared with elderly patients that had fusion with ICBG. This may be partly due to the effect of advanced age on MSC potential.

A self-organising biomimetic collagen/nano-hydroxyapatite-glycosaminoglycan scaffold for spinal fusion

The use of spinal fusion surgery as a treatment for degenerative spinal conditions and chronic back pain is increasing. However, this technique requires use of a bone grafting material to fuse the vertebrae, traditionally autologous bone, which consists of an optimal combination of osteogenic cell precursors, extracellular matrix proteins and mineral components. To date, this remains the 'gold standard' material but its supply is limited and is associated with a number of clinical and ethical difficulties; consequently, various combinations of cells with biological scaffold materials have been tested but have failed to achieve fusion rates even comparable to autologous bone. We successfully fabricated a novel collagen-based scaffold using self-organising atelocollagen combined with nano-hydroxyapatite and chondroitin sulphate, cross-linked by microbial transglutaminase. The scaffold was characterised using a range of imaging, chemical composition and thermal analysis techniques. It was found to exhibit appropriate stiffness and suitable pore size for the adhesion, growth and differentiation of MSCs. The low toxicity makes it suitable for clinical application, and its slow degradation profile would enable the scaffold to promote bone growth over an extended period. This material therefore shows promise for clinical use in spinal fusion and other procedures requiring the use of bone grafts.

Retrospective Study of Anterior Interbody Fusion Rates and Patient Outcomes of Using Mineralized Collagen and Bone Marrow Aspirate in Multilevel Adult Spinal Deformity Surgery

DESIGN

Retrospective, single-center analysis of multilevel anterior fusion rates and health-related quality-of-life outcomes of mineralized collagen and bone marrow aspirate (BMA) in anterior interbody fusion cages for spine fusion surgery.

OBJECTIVE

To determine the ability and effectiveness of mineralized collagen and BMA to achieve multilevel anterior spinal fusion in adult spinal deformity patients when placed in carbon fiber reinforced polymer cages.

SUMMARY OF BACKGROUND DATA

High rates of postoperative pain and nonunion can result from spine fusion procedures. Factors that affect the success of fusion include patient comorbidities, position of implant, and mechanical and biological deficiencies, as well as the choice of bone graft replacement.

METHODS

Analysis of radiographic images and health-related quality-of-life outcomes was performed for a consecutive series of 22 prospectively enrolled adult spinal deformity patients with 104 total anterior fusion levels. Fusions were graded by 3 blinded surgeons not involved in the operative procedure; each fusion was graded on a 1-4 scale based on fusion mass appearance. Levels with an average fusion grade of 1-2.4 were classified as fused; levels with an average grade >2.5 were classified as not fused.

RESULTS

The mean patient age was 51.5 years (range, 38-61) with 21 females. A total of 95% of anterior operative levels were graded as fused based on flexion/extension and full-length biplane radiographs at 1 year. Computed tomography grading showed a reduced fusion rate at 87% overall. There was a statistically significant improvement in the Oswestry Disability Index and Scoliosis Research Society 22-item questionnaire scores at 1 and 2 years after index surgery.

CONCLUSIONS

Fusion rates in multilevel anterior spinal fusion using mineralized collagen and BMA are relatively low compared with fusion rates of 95% or more reported in the existing literature on long fusions with bone morphogenetic protein.

Efficacy of i-Factor Bone Graft versus Autograft in Anterior Cervical Discectomy and Fusion: Results of the Prospective, Randomized, Single-blinded Food and Drug Administration Investigational Device Exemption Study

STUDY DESIGN

A prospective, randomized, controlled, parallel, single-blinded noninferiority multicenter pivotal FDA IDE trial.

OBJECTIVE

The objective of this study was to investigate efficacy and safety of i-Factor Bone Graft (i-Factor) compared with local autograft in single-level anterior cervical discectomy and fusion (ACDF) for cervical radiculopathy.

SUMMARY OF BACKGROUND DATA

i-Factor is a composite bone substitute material consisting of the P-15 synthetic collagen fragment adsorbed onto anorganic bone mineral and suspended in an inert biocompatible hydrogel carrier. P-15 has demonstrated bone healing efficacy in dental, orthopedic, and nonhuman applications.

METHODS

Patients randomly received either autograft (N = 154) or i-Factor (N = 165) in a cortical ring allograft. Study success was defined as noninferiority in fusion, Neck Disability Index (NDI), and Neurological Success endpoints, and similar adverse events profile at 12 months.

RESULTS

At 12 months (follow-up rate 87%), both i-Factor and autograft subjects demonstrated a high fusion rate (88.97% and 85.82%, respectively, noninferiority P = 0.0004), significant improvements in NDI (28.75 and 27.40, respectively, noninferiority P < 0.0001), and high Neurological Success rate (93.71% and 93.01%, respectively, noninferiority P < 0.0001). There was no difference in the rate of adverse events (83.64% and 82.47% in the i-Factor and autograft groups, respectively, P = 0.8814). Overall success rate consisting of fusion, NDI, Neurological Success and Safety Success was higher in i-Factor subjects than in autograft subjects (68.75% and 56.94%, respectively, P = 0.0382). Improvements in VAS pain and SF-36v2 scores were clinically relevant and similar between the groups. A high proportion of patients reported good or excellent Odom outcomes (81.4% in both groups).

CONCLUSION

i-Factor has met all four FDA mandated noninferiority success criteria and has demonstrated safety and efficacy in single-level ACDF for cervical radiculopathy. i-Factor and autograft groups demonstrated significant postsurgical improvement and high fusion rates.

LEVEL OF EVIDENCE

1.

Synthetic bone graft versus autograft or allograft for spinal fusion: a systematic review

The purpose of this review was to compare the efficacy and safety of synthetic bone graft substitutes versus autograft or allograft for the treatment of lumbar and cervical spinal degenerative diseases. Multiple major medical reference databases were searched for studies that evaluated spinal fusion using synthetic bone graft substitutes (either alone or with an autograft or allograft) compared with autograft and allograft. Randomized controlled trials (RCT) and cohort studies with more than 10 patients were included. Radiographic fusion, patient-reported outcomes, and functional outcomes were the primary outcomes of interest. The search yielded 214 citations with 27 studies that met the inclusion criteria. For the patients with lumbar spinal degenerative disease, data from 19 comparative studies were included: 3 RCTs, 12 prospective, and 4 retrospective studies. Hydroxyapatite (HA), HA+collagen, β-tricalcium phosphate (β-TCP), calcium sulfate, or polymethylmethacrylate (PMMA) were used. Overall, there were no differences between the treatment groups in terms of fusion, functional outcomes, or complications, except in 1 study that found higher rates of HA graft absorption. For the patients with cervical degenerative conditions, data from 8 comparative studies were included: 4 RCTs and 4 cohort studies (1 prospective and 3 retrospective studies). Synthetic grafts included HA, β-TCP/HA, PMMA, and biocompatible osteoconductive polymer (BOP). The PMMA and BOP grafts led to lower fusion rates, and PMMA, HA, and BOP had greater risks of graft fragmentation, settling, and instrumentation problems compared with iliac crest bone graft. The overall quality of evidence evaluating the potential use and superiority of the synthetic biological materials for lumbar and cervical fusion in this systematic review was low or insufficient, largely due to the high potential for bias and small sample sizes. Thus, definitive conclusions or recommendations regarding the use of these synthetic materials should be made cautiously and within the context of the limitations of the evidence.

Promoting spinal fusions by biomineralized silk fibroin films seeded with bone marrow stromal cells: An in vivo animal study

OBJECTIVES

To prepare a biomineralized nano silk fibroin film seeded with bone marrow stromal cells (BMSCs), and to evaluate its performance in spinal fusion.

METHODS

The silk fibroin film was mineralized in a modified, simulated body fluid, seeded with BMSCs, and evaluated in a rat model of posterolateral lumbar fusion, compared with pure silk fibroin, silk fibroin/bone marrow stromal cells, mineralized silk fibroin, mineralized silk fibroin/bone marrow stromal cells, iliac crest bone, and no graft. After 12 weeks, all rats were sacrificed and underwent manual palpation, micro-CT scanning, biomechanical testing, and histology.

RESULTS

The infrared spectrum, X-ray diffraction, and scanning electron microscopy demonstrated deposition of mineral layers on the silk fibroin film surface. The fusion rate, bone volume, relative strength and stiffness, and histological score of the mineralized silk fibroin/bone marrow stromal cells were slightly lower than the autograft, but without any significant difference (p > 0.05). In addition, the mineralized silk fibroin was significantly greater in most parameters than the silk fibroin/bone marrow stromal cells (p < 0.05).

CONCLUSION

The mineralized silk fibroin resembles natural bone structurally, and the cellular and mineral layers of silk fibroin are both critical to bone regeneration. The ability to promote spinal fusion is enhanced when the mineralized silk fibroin is seeded with bone marrow stromal cells.

The Current Role of Stem Cells in Orthopaedic Surgery

Basic science and experimental research on stem cells has increased exponentially in the last decade. Our present knowledge about stem cell biology is better than ever before. This new paradigm shift in research has been reflected in the field of orthopaedic surgery. Various experimental models have suggested a potential application of stem cells for different orthopaedic conditions, and early clinical results of stem cell use have been encouraging. These cells can be easily isolated, processed and made available for clinical use. From healing of bone defects caused by trauma, tumor or infection to cartilage defects, nerve, tendon and ligament healing, stem cell use has the potential to revolutionize orthopaedic practice. The purpose of this article is to orient a general orthopaedic surgeon towards the current use and clinical applications of stem cell based therapy in orthopaedics and to provide a complete overview of the clinical advances in this field.

Mineralized Collagen: Rationale, Current Status, and Clinical Applications

This paper presents a review of the rationale for the in vitro mineralization process, preparation methods, and clinical applications of mineralized collagen. The rationale for natural mineralized collagen and the related mineralization process has been investigated for decades. Based on the understanding of natural mineralized collagen and its formation process, many attempts have been made to prepare biomimetic materials that resemble natural mineralized collagen in both composition and structure. To date, a number of bone substitute materials have been developed based on the principles of mineralized collagen, and some of them have been commercialized and approved by regulatory agencies. The clinical outcomes of mineralized collagen are of significance to advance the evaluation and improvement of related medical device products. Some representative clinical cases have been reported, and there are more clinical applications and long-term follow-ups that currently being performed by many research groups.

Biomaterials for Bone Regenerative Engineering

Strategies for bone tissue regeneration have been continuously evolving for the last 25 years since the introduction of the "tissue engineering" concept. The convergence of the life, physical, and engineering sciences has brought in several advanced technologies available to tissue engineers and scientists. This resulted in the creation of a new multidisciplinary field termed as "regenerative engineering". In this article, the role of biomaterials in bone regenerative engineering is systematically reviewed to elucidate the new design criteria for the next generation of biomaterials for bone regenerative engineering. The exemplary design of biomaterials harnessing various materials characteristics towards successful bone defect repair and regeneration is highlighted. Particular attention is given to the attempts of incorporating advanced materials science, stem cell technologies, and developmental biology into biomaterials design to engineer and develop the next generation bone grafts.

Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 16: bone graft extenders and substitutes as an adjunct for lumbar fusion

In an attempt to enhance the potential to achieve a solid arthrodesis and avoid the morbidity of harvesting autologous iliac crest bone (AICB) for a lumbar fusion, numerous alternatives have been investigated. The use of these fusion adjuncts has become routine despite a lack of convincing evidence demonstrating a benefit to justify added costs or potential harm. Potential alternatives to AICB include locally harvested autograft, calcium-phosphate salts, demineralized bone matrix (DBM), and the family of bone morphogenetic proteins (BMPs). In particular, no option has created greater controversy than the BMPs. A significant increase in the number of publications, particularly with respect to the BMPs, has taken place since the release of the original guidelines. Both DBM and the calciumphosphate salts have demonstrated efficacy as a graft extender or as a substitute for AICB when combined with local autograft. The use of recombinant human BMP-2 (rhBMP-2) as a substitute for AICB, when performing an interbody lumbar fusion, is considered an option since similar outcomes have been observed; however, the potential for heterotopic bone formation is a concern. The use of rhBMP-2, when combined with calcium phosphates, as a substitute for AICB, or as an extender, when used with local autograft or AICB, is also considered an option as similar fusion rates and clinical outcomes have been observed. Surgeons electing to use BMPs should be aware of a growing body of literature demonstrating unique complications associated with the use of BMPs.

Ceramic-based bone grafts as a bone grafts extender for lumbar spine arthrodesis: a systematic review

Study Design Systematic review. Objective Ceramic-based bone grafts have been widely utilized to reduce the need for iliac crest bone grafting given the complications associated with the harvest of iliac crest autograft. As a family, ceramics vary widely based on differences in composition, manufacturing, porosity, and structure, which may ultimately affect their efficacy. This article reviews the current data of ceramics used in different environments in the lumbar spine to achieve arthrodesis. Methods Medline, EMBASE, and Cochrane Central Register of Controlled Trials were searched for publications from 1980 to 2013 involving ceramic-based bone grafts in the lumbar spine. Variables such as age of patients, volume of ceramic, procedure, time to evaluation, method of evaluation, specific composition of ceramic, adjuncts used with ceramic products, type of fusion, and fusion rate were compared using a multivariate logistic regression model. Results Thirty studies with 1,332 patients met the final inclusion criteria. The overall fusion rate for all ceramic products as a bone graft extender in the lumbar spine was 86.4%. Age, gender, method of evaluation (plain radiographs, computed tomography, or combination), or specific ceramic product did not significantly affect fusion rate. Ceramics used in combination with local autograft resulted in significantly higher fusion rates compared with all other adjuncts, and bone marrow aspirate and platelet concentrates resulted in significantly lower fusion rates. Conclusions Ceramic-based bone grafts represent a promising bone graft extender in lumbar spine fusion when an osteoinductive stimulus, such as local bone graft is available.

Posterior lumbar fusion: choice of approach and adjunct techniques

The choice among the many options of approach and adjunct techniques in planning a posterior lumbar fusion can be problematic. Debates remain as to whether solid fusion has an advantage over pseudarthrosis regarding long-term symptom deterioration and whether an instrumented or a noninstrumented approach will best serve clinically and/or cost effectively, particularly in elderly patients. Increased motion resulting in higher rates of nonunion and the use of nonsteroidal anti-inflammatory drugs have been studied in animal models and are presumed risk factors, despite the lack of clinical investigation. Smoking is a proven risk factor for pseudarthrosis in both animal models and level III clinical studies. Recent long-term studies and image/clinical assessment of lumbar fusions and pseudarthrosis show that, although imaging remains a key area of difficulty in assessment, including an instrumented approach and a well-selected biologic adjunct, as well as achieving a solid fusion, all carry important long-term clinical advantages in avoiding revision surgery for nonunion.

Hydroxyapatite-Based Biomaterials Versus Autologous Bone Graft in Spinal Fusion: An In Vivo Animal Study

STUDY DESIGN

An in vivo study was designed to compare the efficacy of biomimetic magnesium-hydroxyapatite (MgHA) and of human demineralized bone matrix (HDBM), both dispersed in a mixture of biomimetic MgHA nanoparticles, with that of an autologous bone graft.

OBJECTIVE

The objective of this study was to evaluate 2 new bone substitutes as alternatives to a bone autograft for spinal fusion, determining their osteoinductive and osteoconductive properties, and their capacity of remodeling, using a large animal model.

SUMMARY OF BACKGROUND DATA

Spinal fusion is a common surgical procedure and it is performed for different conditions. A successful fusion requires potentially osteogenic, osteoinductive, and osteoconductive biomaterials.

METHODS

A posterolateral spinal fusion model involved 18 sheep, bilaterally implanting test materials between the vertebral transverse processes. The animals were divided into 2 groups: 1 fusion level was treated with MgHA (group 1) or with HDBM-MgHA (group 2). The other fusion level received bone autografts in both groups.

RESULTS

Radiographical, histological, and microtomographic results indicated good osteointegration between the spinous process and the vertebral foramen for both materials. Histomorphometry revealed no significant differences between MgHA and autologous bone for all the parameters examined, whereas significantly lower values of bone volume were observed between HDBM-MgHA and autologous bone. Moreover, the normalization of the histomorphometric data with autologous bone revealed that MgHA showed a significantly higher value of bone volume and a lower value of trabecular number, more similar to autologous bone than HDBM-MgHA.

CONCLUSION

The study showed that the use of MgHA in an ovine model of spinal fusion led to the deposition of new bone tissue without qualitative and quantitative differences with respect to new bone formed with autologous bone, whereas the HDBM-MgHA led to a reduced deposition of newly formed bone tissue.

LEVEL OF EVIDENCE

N/A.

Clinical applications of mesenchymal stem cells in chronic diseases

Extraordinary progress in understanding several key features of stem cells has been made in the last ten years, including definition of the niche, and identification of signals regulating mobilization and homing as well as partial understanding of the mechanisms controlling self-renewal, commitment, and differentiation. This progress produced invaluable tools for the development of rational cell therapy protocols that have yielded positive results in preclinical models of genetic and acquired diseases and, in several cases, have entered clinical experimentation with positive outcome. Adult mesenchymal stem cells (MSCs) are nonhematopoietic cells with multilineage potential to differentiate into various tissues of mesodermal origin. They can be isolated from bone marrow and other tissues and have the capacity to extensively proliferate in vitro. Moreover, MSCs have also been shown to produce anti-inflammatory molecules which can modulate humoral and cellular immune responses. Considering their regenerative potential and immunoregulatory effect, MSC therapy is a promising tool in the treatment of degenerative, inflammatory, and autoimmune diseases. It is obvious that much work remains to be done to increase our knowledge of the mechanisms regulating development, homeostasis, and tissue repair and thus to provide new tools to implement the efficacy of cell therapy trials.

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.

Developmental-like bone regeneration by human embryonic stem cell-derived mesenchymal cells

The in vivo osteogenesis potential of mesenchymal-like cells derived from human embryonic stem cells (hESC-MCs) was evaluated in vivo by implantation on collagen/hydroxyapatite scaffolds into calvarial defects in immunodeficient mice. This study is novel because no osteogenic or chondrogenic differentiation protocols were applied to the cells prior to implantation. After 6 weeks, X-ray, microCT, and histological analysis showed that the hESC-MCs had consistently formed a highly vascularized new bone that bridged the bone defect and seamlessly integrated with host bone. The implanted hESC-MCs differentiated in situ to functional hypertrophic chondrocytes, osteoblasts, and osteocytes forming new bone tissue via an endochondral ossification pathway. Evidence for the direct participation of the human cells in bone morphogenesis was verified by two separate assays: with Alu and by human mitochondrial antigen positive staining in conjunction with co-localized expression of human bone sialoprotein in histologically verified regions of new bone. The large volume of new bone in a calvarial defect and the direct participation of the hESC-MCs far exceeds that of previous studies and that of the control adult hMSCs. This study represents a key step forward for bone tissue engineering because of the large volume, vascularity, and reproducibility of new bone formation and the discovery that it is advantageous to not over-commit these progenitor cells to a particular lineage prior to implantation. The hESC-MCs were able to recapitulate the mesenchymal developmental pathway and were able to repair the bone defect semi-autonomously without preimplantation differentiation to osteo- or chondroprogenitors.

Cell based therapies as compared to autologous bone grafts for spinal arthrodesis

STUDY DESIGN

Systematic review.

OBJECTIVE

To compare the clinical outcome of cell based grafts combined with bone extenders to autologous bone grafts.

SUMMARY OF BACKGROUND DATA

Alternative graft options that combine mesenchymal stem cells (MSCs) and bone marrow aspirate (BMA) with synthetic or allograft scaffolds have been recently used in several animal and clinical studies.

METHODS

This systematic review of the literature addresses the following key questions (KQs): (1) Does the use of MSCs or BMA combined with synthetic or allograft extenders contribute to thoracolumbar fusion rates that are comparable with the rates achieved by the use of iliac crest graft? (2) Are these fusion rates comparable with those of local bone graft (LBG)? (3) Does the addition of MSCs or BMA to iliac crest bone graft or LBG contribute to better throracolumbar fusion rates? (4) Are the cervical spine fusion outcomes achieved by the use of SCM or BMA with synthetic or allograft scaffolds comparable with the iliac crest bone graft or LBG outcomes? (5) Was there any difference in terms of fusion rates, when MSCs were compared with BMA?

RESULTS

For KQ1, 4 level II, III studies used iliac crest bone graft as control. The results of these studies were inconsistent, and the overall body of evidence was found insufficient. Three, level II, III studies were identified for KQ2. Comparable fusion rates were demonstrated between LBG and BMA combined with calcium phosphate or collagen carrier. The overall body of evidence was found weak. For KQ3, one level III study was found. No significant difference was found in the fusion rates. No studies met the criteria for KQ4, 5.

CONCLUSION

The currently available evidence is insufficient to support the use of MSCs or BMA combined with synthetic or allograft materials as a substitute or supplementary graft to autologous bone graft.

LEVEL OF EVIDENCE

2.

Optimal aspiration volume of vertebral bone marrow for use in spinal fusion

BACKGROUND CONTEXT

Bone marrow aspirate (BMA) has shown promise as a bone graft option in spinal fusion. The vertebral body is a convenient source for marrow aspirate as it is accessed in routine course of pedicle screw instrumentation. Studies have relied on data from the iliac crest to determine optimal aspiration volume from the vertebral body.

PURPOSE

This study is designed to determine the optimal aspiration volume for BMA taken from the vertebral body.

STUDY DESIGN

Prospective clinical study.

PATIENT SAMPLE

Data are drawn from 18 pedicles and 180 aspirations. The average age of the subjects was 50.3 years, and the subject pool comprised five men and seven women.

OUTCOME MEASURES

Nucleated cell count and alkaline phosphatase staining colony forming units.

METHODS

Ten 1 mL aliquots of BMA were incrementally aspirated through a cannulated pedicle tap for each instrumented vertebral body. The numbers of nucleated cells per mL of BMA were analyzed with a hemocytometer, and the percentage of osteoprogenitor cells per mL aspirate were estimated by an alk phos production assay. The study was funded through departmental funds, and none of the authors have any conflicts of interest to report related to the study.

RESULTS

Nucleated cell count decreased with increasing aspirate number (p<.001). The average cell count for the first mL was 45.8 million cells. Cell counts did not differ by age or sex (p=.943 and p=.685, respectively). Likewise, osteoprogenitor cell percentage decreased with increasing aspirate number (p<.001).

CONCLUSIONS

The 2 mL aspirate volume has been defined as ideal for the iliac crest, but there has been no analogous assessment of the effect of aspiration volume for other sources such as the vertebral body. This information is important for the clinical implementation of vertebral body aspirations if volume, cells, and presumably performance, of this potential bone graft option are to be optimized for spine cases. Our data show a direct relationship between increasing aspiration number and decreasing osteoprogenitor cellular concentration, with a drop to 50% of the original aspirate cell count by the 4th mL aspirate. The vertebral body is a potentially exciting source of osteoprogenitor cells that can be implemented for a variety of spinal uses.