Osteoinductivity of commercially available demineralized bone matrix. Preparations in a spine fusion model

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.

From Basic Science to Clinical Practice: A Review of Current Periodontal/Mucogingival Regenerative Biomaterials

Periodontitis is a dysbiosis-driven inflammatory disease affecting the tooth-supporting tissues, characterized by their progressive resorption, which can ultimately lead to tooth loss. A step-wise therapeutic approach is employed for periodontitis. After an initial behavioral and non-surgical phase, intra-bony or furcation defects may be amenable to regenerative procedures. This review discusses the regenerative technologies employed for periodontal regeneration, highlighting the current limitations and future research areas. The search, performed on the MEDLINE database, has identified the available biomaterials, including biologicals (autologous platelet concentrates, hydrogels), bone grafts (pure or putty), and membranes. Biologicals and bone grafts have been critically analyzed in terms of composition, mechanism of action, and clinical applications. Although a certain degree of periodontal regeneration is predictable in intra-bony and class II furcation defects, complete defect closure is hardly achieved. Moreover, treating class III furcation defects remains challenging. The key properties required for functional regeneration are discussed, and none of the commercially available biomaterials possess all the ideal characteristics. Therefore, research is needed to promote the advancement of more effective and targeted regenerative therapies for periodontitis. Lastly, improving the design and reporting of clinical studies is suggested by strictly adhering to the Consolidated Standards of Reporting Trials (CONSORT) 2010 statement.

Self-Assembled Nanocomposite Hydrogels as Carriers for Demineralized Bone Matrix Particles and Enhanced Bone Repair

Demineralized bone matrix (DBM) has been widely used as an allogeneic alternative to autologous bone graft for bone repair. However, more extensive use of DBM is limited due to its particulate nature after demineralization and rapid particle dispersion following irrigation, resulting in unpredictable osteoinductivity. Here, a new design of injectable hydrogel carriers for DBM that combine self-healing ability and osteogenic properties based on the self-assembly of guanidinylated hyaluronic acid and silica-rich nanoclays is reported. The nanoclays serve as reversible linkages to form a dynamic hydrogel network with the guanidine moieties on the polymer chains. Gelation kinetics and mechanical properties can be controlled by altering nanoclay content in the hydrogel. The resulting hydrogel exerts self-healing ability due to its dynamic crosslinks and well retains its overall performance with high DBM loading. The hydrogel exhibits great cytocompatibility and osteogenic effects mediated by the nanoclays. In vivo delivery of DBM using the nanocomposite hydrogel further demonstrates robust bone regeneration in a mouse calvarial defect model in comparison to DBM delivered with aqueous HA. This work suggests a promising hydrogel platform for many applications including therapeutic delivery and tissue engineering.

Comparison of demineralized bone matrix with different cycling crushing times in posterolateral fusion model of athymic rats

Decalcified bone matrix (DBM) is a widely used alternative material for bone transplantation. In the DBM production process, an effective particle size and the highest utilization rate of raw materials can be achieved only through multiple high-speed circulating comminution. The rat posterolateral lumbar fusion model (PLF) is the most mature small animal model for the initial evaluation of the efficacy of graft materials for bone regeneration and spinal fusion. To evaluate the differences in the in vivo osteogenic effects of DBM pulverization through 1, 5, 9, and 14 high-speed cycles, sixty athymic rats were divided into six groups: single cycling crushing (CC1), 5 cycles of crushing (CC5), 9 cycles of crushing (CC9), 13 cycles of crushing (CC13), autogenous bone graft (ABG) and negative control (NC). Posterolateral lumbar fusion was performed. Six weeks after surgery, the bilateral lumbar fusion of athymic rats was evaluated through manual palpation, X-ray, micro-CT and histological sections. Rank data were tested by the rank-sum test, and nonparametric data were tested by the Kruskal‒Wallis H test. The manual palpation and X-ray results showed that the fusion rate did not significantly differ between the CC1, CC5, CC9, CC13 and ABG groups. However, cavities appeared in CC9 and CC13 on the micro-CT image. The bone mass (BV/TV) of CC1, CC5, CC9 and CC13 was better than that of the ABG group, while almost no osteogenesis was observed in the NC group. Histologically, there was no obvious difference between the four groups except that the CC9 group and CC13 group had more fibrous tissues in the new bone. In conclusion, DMB with different cycling crushing times has no obvious difference in fusion rate of PLF, but it is slightly better than the ABG group.

Inducing Angiogenesis in the Nucleus Pulposus

Bone morphogenetic protein (BMP) gene delivery to Lewis rat lumbar intervertebral discs (IVDs) drives bone formation anterior and external to the IVD, suggesting the IVD is inhospitable to osteogenesis. This study was designed to determine if IVD destruction with a proteoglycanase, and/or generating an IVD blood supply by gene delivery of an angiogenic growth factor, could render the IVD permissive to intra-discal BMP-driven osteogenesis and fusion. Surgical intra-discal delivery of naïve or gene-programmed cells (BMP2/BMP7 co-expressing or VEGF165 expressing) +/- purified chondroitinase-ABC (chABC) in all permutations was performed between lumbar 4/5 and L5/6 vertebrae, and radiographic, histology, and biomechanics endpoints were collected. Follow-up anti-sFlt Western blotting was performed. BMP and VEGF/BMP treatments had the highest stiffness, bone production and fusion. Bone was induced anterior to the IVD, and was not intra-discal from any treatment. chABC impaired BMP-driven osteogenesis, decreased histological staining for IVD proteoglycans, and made the IVD permissive to angiogenesis. A soluble fragment of VEGF Receptor-1 (sFlt) was liberated from the IVD matrix by incubation with chABC, suggesting dysregulation of the sFlt matrix attachment is a possible mechanism for the chABC-mediated IVD angiogenesis we observed. Based on these results, the IVD can be manipulated to foster vascular invasion, and by extension, possibly osteogenesis.

Current concepts of bone grafting in trauma surgery

Bone graft in trauma surgery is commonly used in managing bone defects, non-union, fracture related infections, arthrodesis or to provide structural support in fractures. A variety of bone grafts are made available to the treating physician, which includes autograft, allograft and bone graft substitutes. The future of bone grafting in trauma surgery is exciting with the incorporation of technological advancement such as gene therapy, 3D-printing and tissue engineering. Regardless, there are still limitations to what we understand regarding current bone grafting techniques with conflicting literature on their clinical utility and indication. The aim of this review article therefore is to take a step back and critically evaluate the current concepts of bone grafting in trauma surgery, with special emphasis made on reviewing the types of bone graft, biology of bone graft incorporation and indication for its use in various clinical scenarios.

The Clinical Use of Osteobiologic and Metallic Biomaterials in Orthopedic Surgery: The Present and the Future

As the area and range of surgical treatments in the orthopedic field have expanded, the development of biomaterials used for these treatments has also advanced. Biomaterials have osteobiologic properties, including osteogenicity, osteoconduction, and osteoinduction. Natural polymers, synthetic polymers, ceramics, and allograft-based substitutes can all be classified as biomaterials. Metallic implants are first-generation biomaterials that continue to be used and are constantly evolving. Metallic implants can be made from pure metals, such as cobalt, nickel, iron, or titanium, or from alloys, such as stainless steel, cobalt-based alloys, or titanium-based alloys. This review describes the fundamental characteristics of metals and biomaterials used in the orthopedic field and new developments in nanotechnology and 3D-printing technology. This overview discusses the biomaterials that clinicians commonly use. A complementary relationship between doctors and biomaterial scientists is likely to be necessary in the future.

Advances Focusing on the Application of Decellularized Extracellular Matrix in Periodontal Regeneration

The decellularized extracellular matrix (dECM) is capable of promoting stem cell proliferation, migration, adhesion, and differentiation. It is a promising biomaterial for application and clinical translation in the field of periodontal tissue engineering as it most effectively preserves the complex array of ECM components as they are in native tissue, providing ideal cues for regeneration and repair of damaged periodontal tissue. dECMs of different origins have different advantages and characteristics in promoting the regeneration of periodontal tissue. dECM can be used directly or dissolved in liquid for better flowability. Multiple ways were developed to improve the mechanical strength of dECM, such as functionalized scaffolds with cells that harvest scaffold-supported dECM through decellularization or crosslinked soluble dECM that can form injectable hydrogels for periodontal tissue repair. dECM has found recent success in many periodontal regeneration and repair therapies. This review focuses on the repairing effect of dECM in periodontal tissue engineering, with variations in cell/tissue sources, and specifically discusses the future trend of periodontal regeneration and the future role of soluble dECM in entire periodontal tissue regeneration.

Murine models of posterolateral spinal fusion: A systematic review

BACKGROUND

Rodent models are commonly used experimentally to assess treatment effectiveness in spinal fusion. Certain factors are associated with better fusion rates. The objectives of the present study were to report the protocols most frequently used, to evaluate factors known to positively influence fusion rate, and to identify new factors.

METHOD

A systematic literature search of PubMed and Web of Science found 139 experimental studies of posterolateral lumbar spinal fusion in rodent models. Data for level and location of fusion, animal strain, sex, weight and age, graft, decortication, fusion assessment and fusion and mortality rates were collected and analyzed.

RESULTS

The standard murine model for spinal fusion was male Sprague Dawley rats of 295g weight and 13 weeks' age, using decortication, with L4-L5 as fusion level. The last two criteria were associated with significantly better fusion rates. On manual palpation, the overall mean fusion rate in rats was 58% and the autograft mean fusion rate was 61%. Most studies evaluated fusion as a binary on manual palpation, and only a few used CT and histology. Average mortality was 3.03% in rats and 1.56% in mice.

CONCLUSIONS

These results suggest using a rat model, younger than 10 weeks and weighing more than 300 grams on the day of surgery, to optimize fusion rates, with decortication before grafting and fusing the L4-L5 level.

Use of biphasic calcium phosphate versus demineralized bone matrix: retrospective clinical and CT analysis of posterolateral fusion results

PURPOSE

Bone graft extenders have been developed to prevent donor site morbidity associated with iliac crest bone graft, but few studies compared the efficacy of various substitutes. Our purpose was to determine fusion rate and clinical outcome in patients undergoing lumbar arthrodesis using demineralized bone matrix (DBM) and biphasic calcium phosphate (BCP).

METHODS

Patients with degenerative spondylolisthesis undergoing one-level or two-level arthrodesis of lumbar spine were retrospectively reviewed. Two treatment groups placed either BCP or DBM, in addition to local autograft in lumbar posterolateral space. Three-dimensional CT exam and dynamic flexion-extension radiographs at postoperative 2-year were assessed for posterolateral fusion status and pain scale and Oswestry Disability Index (ODI) for clinical outcome.

RESULTS

Of the 148 patients reviewed (including 23 in one- and 58 patients in two-level in BCP group, and 47 in one- and 20 patients in two-level in DBM group), no significant differences were found in terms of age, sex, BMI, smoking, diabetes, steroids, number of level fused, non-union rate or revision surgery between BCP and DBM groups. Significantly improved pain scale of back and leg and ODI were found in both groups postoperatively without group difference. We found a comparable fusion rate in one-level surgery (100% versus 93.6%) and a superior fusion rate of BCP group in two-level surgery (98.3% versus 80.0%, p = 0.01).

CONCLUSION

Being a bone graft extender without osteoinductive property, with local autograft, BCP is comparable to DBM for one- and superior for two-level fusion. No significant difference was found in clinical outcomes.

Decellularized ECM hydrogels: prior use considerations, applications, and opportunities in tissue engineering and biofabrication

Tissue development, wound healing, pathogenesis, regeneration, and homeostasis rely upon coordinated and dynamic spatial and temporal remodeling of extracellular matrix (ECM) molecules. ECM reorganization and normal physiological tissue function, require the establishment and maintenance of biological, chemical, and mechanical feedback mechanisms directed by cell-matrix interactions. To replicate the physical and biological environment provided by the ECM in vivo, methods have been developed to decellularize and solubilize tissues which yield organ and tissue-specific bioactive hydrogels. While these biomaterials retain several important traits of the native ECM, the decellularizing process, and subsequent sterilization, and solubilization result in fragmented, cleaved, or partially denatured macromolecules. The final product has decreased viscosity, moduli, and yield strength, when compared to the source tissue, limiting the compatibility of isolated decellularized ECM (dECM) hydrogels with fabrication methods such as extrusion bioprinting. This review describes the physical and bioactive characteristics of dECM hydrogels and their role as biomaterials for biofabrication. In this work, critical variables when selecting the appropriate tissue source and extraction methods are identified. Common manual and automated fabrication techniques compatible with dECM hydrogels are described and compared. Fabrication and post-manufacturing challenges presented by the dECM hydrogels decreased mechanical and structural stability are discussed as well as circumvention strategies. We further highlight and provide examples of the use of dECM hydrogels in tissue engineering and their role in fabricating complex in vitro 3D microenvironments.

Use of graft materials and biologics in spine deformity surgery: a state-of-the-art review

PURPOSE

The aim of the current review is to summarize the current evidence on graft materials used in fusion procedures for spinal deformity corrections.

METHODS

PubMed, Embase, and Cochrane Library were searched for relevant published observational studies and clinical trials using osteobiologics and biomaterials in spinal deformity surgery.

RESULTS

The use of autograft in deformity correction surgeries has been reported in a limited number of studies, with the harvest sites including iliac crest, ribs, and local bone. Various allografts and biologics have been used in the treatment of spinal deformities including idiopathic and degenerative scoliosis, either as stand alone or in combination with autograft. Limited number of studies reported no differences in fusion rates or outcomes. Use of rh-BMP2 in anterior, posterior or front/back approaches showed higher fusion rates than other graft materials in patients with spinal deformities. Due to the limited number of quality studies included in the review, as well as alternative factors, such as costs, availability, and surgeon expertise/preference, no definitive conclusion or recommendations can be made as to the ideal graft choice in spinal deformity surgery.

CONCLUSIONS

Most commonly used grafts included autograft, allograft and rh-BMP2, with new biologics and biomaterials constantly emerging in the market. Limited number of high-quality comparative studies and heterogeneity in study design prevented direct comparisons that can lead to meaningful recommendations. Further studies are needed to prove superiority of any single graft material and/or biologic that is also cost-effective and safe.

FDA-approved bone grafts and bone graft substitute devices in bone regeneration

To induce bone regeneration there is a complex cascade of growth factors. Growth factors such as recombinant BMP-2, BMP-7, and PDGF are FDA-approved therapies in bone regeneration. Although, BMP shows promising results as being an alternative to autograft, it also has its own downfalls. BMP-2 has many adverse effects such as inflammatory complications such as massive soft-tissue swelling that can compromise a patient's airway, ectopic bone formation, and tumor formation. BMP-2 may also be advantageous for patients not willing to give up smoking as it shows bone regeneration success with smokers. BMP-7 is no longer an option for bone regeneration as it has withdrawn off the market. PDGF-BB grafts in studies have shown PDGF had similar fusion rates to autologous grafts and fewer adverse effects. There is also an FDA-approved bioactive molecule for bone regeneration, a peptide P-15. P-15 was found to be effective, safe, and have similar outcomes to autograft at 2 years post-op for cervical radiculopathy due to cervical degenerative disc disease. Growth factors and bioactive molecules show some promising results in bone regeneration, although more research is needed to avoid their adverse effects and learn about the long-term effects of these therapies. There is a need of a bone regeneration method of similar quality of an autograft that is osteoconductive, osteoinductive, and osteogenic. This review covers all FDA-approved bone regeneration therapies such as the "gold standard" autografts, allografts, synthetic bone grafts, and the newer growth factors/bioactive molecules. It also covers international bone grafts not yet approved in the United States and upcoming technologies in bone grafts.

Efficacy, Cost, and Complications of Demineralized Bone Matrix in Instrumented Lumbar Fusion: Comparison With rhBMP-2

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To evaluate demineralized bone matrix as an adjunct for instrumented lumbar spine fusion compared with recombinant human bone morphogenetic protein-2 (rhBMP-2).

METHODS

Clinical and radiographic review was performed of 43 patients with degenerative spine disease treated with posterolateral spinal fusion with or without posterior or transforaminal lumbar interbody fusion. Final analysis included sixteen patients treated with demineralized bone matrix (DBM; Accell Evo3, SeaSpine) compared with a retrospective matched group of 21 patients treated with rhBMP-2 (rhBMP-2, Infuse, Medtronic). All patients were followed for 24 months. Fusion was evaluated by computed tomography and/or x-ray. Clinical outcomes included visual analogue scale (VAS), Oswestry Disability Index (ODI), and Short Form 12 (SF-12).

RESULTS

Overall fusion rate, including posterolateral and/or interbody fusion, was 100% for both groups, though the fusion rates in the posterolateral space alone were 93.5% and 100% for the DBM and rhBMP-2 groups, respectively. Clinical outcomes were similar between groups, with the DBM group showing greater improvement in ODI. The rhBMP-2 group showed higher rates of radiographic complications with 7 of 21 patients (33.3%) demonstrating either adjacent level fusion or ectopic bone formation, compared with zero in the DBM group. Average biologic cost per level was $1522 for DBM and $3505 for rhBMP-2.

CONCLUSIONS

DBM and rhBMP-2 demonstrated similar radiographic and clinical outcomes in instrumented lumbar fusions. rhBMP-2 was associated with higher rates of radiographic complications and significantly higher costs.

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.

Understanding the Future Prospects of Synergizing Minimally Invasive Transforaminal Lumbar Interbody Fusion Surgery with Ceramics and Regenerative Cellular Therapies

Transforaminal lumber interbody fusion (TLIF) is the last resort to address the lumber degenerative disorders such as spondylolisthesis, causing lower back pain. The current surgical intervention for these abnormalities includes open TLIF. However, in recent years, minimally invasive TLIF (MIS-TLIF) has gained a high momentum, as it could minimize the risk of infection, blood loss, and post-operative complications pertaining to fusion surgery. Further advancement in visualizing and guiding techniques along with grafting cage and materials are continuously improving the safety and efficacy of MIS-TLIF. These assistive techniques are also playing a crucial role to increase and improve the learning curve of surgeons. However, achieving an appropriate output through TLIF still remains a challenge, which might be synergized through 3D-printing and tissue engineering-based regenerative therapy. Owing to their differentiation potential, biomaterials such as stem/progenitor cells may contribute to restructuring lost or damaged tissues during MIS-TLIF, and this therapeutic efficacy could be further supplemented by platelet-derived biomaterials, leading to improved clinical outcomes. Thus, based on the above-mentioned strategies, we have comprehensively summarized recent developments in MIS-TLIF and its possible combinatorial regenerative therapies for rapid and long-term relief.

Partially Digested Osteoblast Cell Line-Derived Extracellular Matrix Induces Rapid Mineralization and Osteogenesis

An extracellular matrix (ECM) utilized as a biomaterial can be obtained from organs of living organisms. Therefore, it has some limitations in its supply because of insufficient organs. Furthermore, therapeutic efficacy of ECMs varies depending on factors such as donor's health condition and age. For this reason, ECMs obtained from a cell line could be a good alternative because they can be produced under a controlled environment with uniform quality. Thus, the purpose of this study was to investigate the potential of the MC3T3-E1 cell line-derived ECM as bone graft. The optimized decellularization process was developed to separate the ECM from MC3T3-E1, osteoblast cell line, using Trypsin-EDTA and Triton X-100. The decellularized ECM was partially digested using pepsin. Also, human bone marrow-derived mesenchymal stem cells induced faster osteogenesis on the ECM-coated surface than on the collagen-coated surface. Partially digested ECM fragments were embedded on the polyethylene glycol scaffold without additional chemical modification or crosslinking. Micro-computed tomography and histological analysis results showed that the ECM in the scaffold promoted actual bone regeneration after in vivo implantation to a mouse calvarial defect model. This study suggests that the bone-specific ECM derived from the cell line can replace the ECM from organs for application in tissue engineering and regenerative medicine.

Surgical outcomes of two kinds of demineralized bone matrix putties/local autograft composites in instrumented posterolateral lumbar fusion

Background

This study aimed to assess the surgical outcomes of two kinds of demineralized bone matrix (DBM) putties/local autograft composites in instrumented posterolateral lumbar fusion (PLF).

Methods

Twenty-seven fusion segments of 19 patients, who underwent decompression and instrumented PLF for lumbar spinal stenosis or degenerative spondylolisthesis less than grade 1, were included in this study. The PLF mass consisted of different two kinds of DBMs (Grafton® and DBX®) and local autograft. Next, 7.5 cc of Grafton® DBM/local autograft composite was implanted on the left side, and the same amount of DBX® DBM/local autograft composite was implanted on the right side in the same patient. The PLF masses of 54 total sides (27 Grafton® sides and 27 DBX® sides) were assessed for fusion based on both flexion/extension lateral radiographs and computed tomography images at 12 and 24 months postoperatively. Clinical symptoms were also evaluated.

Results

At 12 months postoperatively, the fusion rates for the Grafton® and DBX® sides were 59.5 and 51.9%, respectively; the difference was not statistically significant (P = 0.425). At 24 months postoperatively, the fusion rates for the Grafton® and DBX® sides increased to 70.4 and 66.7%, respectively, but the difference was still not statistically significant (P = 0.574). Diabetes mellitus, smoking, and obesity (body mass index ≥25) negatively affected the fusion rate of both the Grafton® and DBX® sides. Visual analog scores for lower back pain and leg pain and Oswestry Disability Index were significantly improved after surgery (both, P < 0.01). No deep or superficial infections occurred postoperatively. No patients underwent revision surgery due to nonunion during follow-up.

Conclusions

Our results suggest that two kinds of DBMs/local autograft composites might be considered as useful bone graft substitute in instrumented posterolateral fusion for lumbar spinal stenosis or degenerative spondylolisthesis less than grade 1.

Cortical strut allografts in salvage revision arthroplasty: Surgical technique and clinical outcomes

BACKGROUND

The aim of this study was to present our clinical outcomes and surgical technique in strut allografts preparation using staggered holes to enhance osteointegration and demineralised bone matrix (DBM) as an adjunct to cortical strut allografts in salvage revision arthroplasty patients.

METHODS

Retrospective consecutive series of patients who required strut allograft femoral reconstructions with minimum 2 years follow up between 2012 and 2018. Frozen washed irradiated, cortical struts were used and prepared adding 2 mm staggered drill holes along the length of the strut and applying DBM paste on the graft-host interface. Outcome measures included radiographic strut union, graft resorption, infection and complications.

RESULTS

15 patients included; 3 males and 12 females with median age 72 years (range 60-93). All had significant bony defects (Paprosky III/IV in 12 cases including 3 cases of periprosthetic hip fractures and further 3 cases of periprosthetic knee fractures around revision hinged implants). At final follow up, median 3.8 years (range 2.7-7.2), 14/15 (93.3%) struts had united at a median 6 months (range 5-8), complete incorporation with cortical round-off was seen at median 12 months (range 8-48) in 12/15 (80%) struts, 2/15 (13.3%) show radiographic evidence of proximal minimal graft resorptions although the remainder of the strut had integrated and were asymptomatic. There were no cases of infection.

CONCLUSIONS

Use of strut allografts helps to reconstruct bone defects, restore bone stock, and provide stable fixation for complex patterns of periprosthetic fractures around hip/knee implants and salvage revision cases with 93.3% union rate at median 6 months.

Use of cement combined grafting in upper and lower extremity benign bone tumors

Objectives

This study aims to investigate the effectivity of cement combined demineralized bone matrix (DBM) treatment on new bone formation in the cortical window as well as to evaluate the effect of new bone formation on functional outcomes.

Patients and methods

Thirty-two benign bone tumor patients (15 males, 17 females; median age 38 years; range, 12 to 68 years), who were treated with cement combined DBM between February 2010 and December 2014, were evaluated retrospectively. Patient characteristics were recorded as age, gender, tumor localization, histological diagnosis, Enneking stage, tumor size, size of the cortical window, usage of prophylactic fixation, time to return to work, Musculoskeletal Tumor Society (MSTS) functional score, tumor relapse, and new bone formation on the cortical window in the computed tomography scans after one year of surgery.

Results

Median tumor volume was 17.2 cm3 (range, 2.8 to 139.6 cm3), median area of the cortical window was 8.3 cm2 (range, 1.6 to 28.4 cm2), and median postoperative one-year MSTS score was 84.5 (range, 66 to 97). MSTS scores were significantly worse with the usage of prophylactic fixation (p<0.001). There was a statistically significant difference between the usage of prophylactic fixation and cortical window size (p=0.013). There was a low-level negative correlation in terms of age and bone formation on the cortical window (p=0.046, r= -0.356) and mid-level negative correlation between cortical window size and functional scores (p=0.001, r= -0.577).

Conclusion

Application of cement combined with DBM procedure is an effective, alternative, and biological treatment in bone tumors that provides immediate stability and stimulates new bone formation on the cortical window.

Scientific, Clinical, Regulatory, and Economic Aspects of Choosing Bone Graft/Biological Options in Spine Surgery

Spinal arthrodesis is a major element of the spinal surgeon's practice. To attain successful fusion rates, attention must be paid to spinal segment immobilization and proper selection of bone graft. Autogenous bone graft (ie, ICBG), the "gold standard," with or without graft extenders and enhancers provides the foundation for most spinal fusions. ABG is the only graft option containing all 3 factors of new bone growth: osteoconductivity, osteoinductivity, and osteogenicity. While many bone graft alternatives function well as bone graft extenders, only growth factors proteins (ie, rhBMP-2 or OP-2) function as bone graft enhancers and substitutes. The search for optimal hybrid interbody cages, bone graft substitutes, autogenous or allogenic stem cells, and nanostructure scaffolds for release of growth factors continues.

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

Introduction: Demineralized bone matrix (DBM) is a widely used bone graft in spinal fusion. Most commercial DBMs are composed of demineralized bone particles (~125–800 microns) suspended in a carrier that provides improved handling but dilutes the osteoinductive component. DBM fibers (DBF) provide improved osteoconductivity and do not require a carrier. It has been suggested that 100% DBF may offer improved performance over particulate-based DBMs with carrier.

Study Design: Seven commercially available DBM products were tested in an athymic rat posterolateral fusion model. There were four 100% DBFs, two DBFs containing a carrier, and one particulate-based DBM containing carrier.

Objective: The study objectives were to evaluate the in vivo performance: (1) compare fusion rate and fusion maturity of six commercially available DBFs and one particulate-based DBM, and (2) assess the effect of carrier on fusion outcomes for DBFs in a posterolateral fusion model.

Methods: The DBF/DBM products evaluated were: Strand^TM Family, Propel® DBM Fibers, Vesuvius® Demineralized Fibers, Optium® DBM Putty, Grafton® DBF, Grafton Flex, and DBX® Putty. Single-level posterolateral fusion was performed in 69 athymic rats. Fusion was assessed bilaterally after 4 weeks by manual palpation, radiograph and CT for bridging bone. Fusion mass maturity was assessed with a CT maturity grading scale and by histology. Statistical analysis was performed using Fishers Exact Test for categorical data and Kruskal-Wallis Test for non-parametric data.

Results: Strand Family achieved 100% fusion (18/18) by manual palpation, radiographic and CT evaluation, significantly higher than Propel Fibers, Vesuvius Fibers, Optium Putty, and DBX Putty, and not statistically higher than Grafton DBF and Grafton Flex. Strand Family provided the highest fusion maturity, with CT maturity grade of 2.3/3.0 and 89% mature fusion rate. Fusion results suggest a detrimental effect of carrier on fusion performance.

Conclusions: There were large variations in fusion performance for seven commercially available DBM products in an established preclinical fusion model. There were even significant differences between different 100% DBF products, suggesting that composition alone does not guarantee in vivo performance. In the absence of definitive clinical evidence, surgeons should carefully consider available data in valid animal models when selecting demineralized allograft options.

Applications of decellularized materials in tissue engineering: advantages, drawbacks and current improvements, and future perspectives

Decellularized materials (DMs) are attracting more and more attention in tissue engineering because of their many unique advantages, and they could be further improved in some aspects through various means.

Investigating the Effects of Tissue-Specific Extracellular Matrix on the Adipogenic and Osteogenic Differentiation of Human Adipose-Derived Stromal Cells Within Composite Hydrogel Scaffolds

While it has been postulated that tissue-specific bioscaffolds derived from the extracellular matrix (ECM) can direct stem cell differentiation, systematic comparisons of multiple ECM sources are needed to more fully assess the benefits of incorporating tissue-specific ECM in stem cell culture and delivery platforms. To probe the effects of ECM sourced from decellularized adipose tissue (DAT) or decellularized trabecular bone (DTB) on the adipogenic and osteogenic differentiation of human adipose-derived stem/stromal cells (ASCs), a novel detergent-free decellularization protocol was developed for bovine trabecular bone that complemented our established detergent-free decellularization protocol for human adipose tissue and did not require specialized equipment or prolonged incubation times. Immunohistochemical and biochemical characterization revealed enhanced sulphated glycosaminoglycan content in the DTB, while the DAT contained higher levels of collagen IV, collagen VI and laminin. To generate platforms with similar structural and biomechanical properties to enable assessment of the compositional effects of the ECM on ASC differentiation, micronized DAT and DTB were encapsulated with human ASCs within methacrylated chondroitin sulfate (MCS) hydrogels through UV-initiated crosslinking. High ASC viability (>90%) was observed over 14 days in culture. Adipogenic differentiation was enhanced in the MCS+DAT composites relative to the MCS+DTB composites and MCS controls after 14 days of culture in adipogenic medium. Osteogenic differentiation studies revealed a peak in alkaline phosphatase (ALP) enzyme activity at 7 days in the MCS+DTB group cultured in osteogenic medium, suggesting that the DTB had bioactive effects on osteogenic protein expression. Overall, the current study suggests that tissue-specific ECM sourced from DAT or DTB can act synergistically with soluble differentiation factors to enhance the lineage-specific differentiation of human ASCs within 3-D hydrogel systems.

The use of demineralised bone fibres (DBF) in conjunction with supercritical carbon dioxide (SCCO2) treated allograft in anterior lumbar interbody fusion (ALIF)

Spinal fusion is a common procedure for the treatment of various spinal pathologies. Since the early days, spinal fusion has been carried out with the use of bone grafts as interbody spacers. With the development of synthetic interbody implants, bone grafts were used to facilitate fusion. Although autograft provides the best outcomes for fusion, allografts have been sought after due to donor site morbidity and other shortcomings. Currently, a vast variety of demineralised bone matrix (DBM) products are available with their methods of processing and preparation impacting their properties and clinical outcomes. Demineralised bone fibres (DBF), a form a DBM can be easily packed into implants when mixed with other substances such as allograft bone and patient's blood providing a scaffold for the mixture. We report two cases of anterior lumbar interbody fusion (ALIF) utilising a titanium-polyetheretherketone (PEEK) interbody cage filled with DBF, allograft and patient's blood with a maximum of 12 months follow-up outcome.

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.

Augmenting endogenous repair of soft tissues with nanofibre scaffolds

As our ability to engineer nanoscale materials has developed we can now influence endogenous cellular processes with increasing precision. Consequently, the use of biomaterials to induce and guide the repair and regeneration of tissues is a rapidly developing area. This review focuses on soft tissue engineering, it will discuss the types of biomaterial scaffolds available before exploring physical, chemical and biological modifications to synthetic scaffolds. We will consider how these properties, in combination, can provide a precise design process, with the potential to meet the requirements of the injured and diseased soft tissue niche. Finally, we frame our discussions within clinical trial design and the regulatory framework, the consideration of which is fundamental to the successful translation of new biomaterials.

Clinical Trial Assessment Principles of National Class III Medical Devices in China

Class III medical devices are defined as those which are implanted inside the human body and applied to maintain normal life and retain original tissue or organic functions. Because these devices are associated with high risk, their effectiveness and safety should be strictly monitored and clinically investigated. The aim of clinical investigation of these medical devices is to ensure the acceptability of their effectiveness and safety levels. On designing the clinical trial, the investigator should determine the indices to assess the effectiveness and safety of medical devices, select reasonable data‐analyzing methods, and pay attention to several other issues. Although some guidelines on specific class III medical devices have illustrated those aspects in detail, there is still no comprehensive report that details all those principles and methodologies. This article aims to summarize the common features among the instruction principles and provide technological support for the clinical study of class III medical devices.

An evaluation of biomaterials and osteobiologics for arthrodesis achievement in spine surgery

An increasing variety of orthobiologic materials, including autologous and allogeneic bone graft, bone marrow aspirate, demineralized bone matrix, ceramics, and growth factors are available to the spine surgeon. Although autologous bone graft remains the gold standard material, concerns for failure in achieving fusion have prompted evaluation of current and new biologic materials. As such, this review attempts to summarize the available biologic materials with their pertinent characteristics, advantages, disadvantages, and primary uses.

Interbody options in lumbar fusion

Interbody devices have revolutionized lumbar fusion surgery by enhancing mechanical stability, optimizing sagittal parameters, and maximizing fusion potential. There are several lumbar interbody fusion approaches available for varying pathologic etiologies, surgical index levels, or due to surgeon preference. With the advancement of spinal instrumentation and interbody devices, a variety of cage materials and dimensions have been engineered to accommodate various lumbar fusion approaches. The efficacy of a fusion is dependent on the shape, size, and material makeup of that interbody device. Since there are numerous cages available in today's market, it is important to find the optimal cage to best accommodate specific lumbar fusion cases. This review will explain the properties and future advancements of various interbody devices available for lumbar fusions.

Autograft, Allograft, and Bone Graft Substitutes: Clinical Evidence and Indications for Use in the Setting of Orthopaedic Trauma Surgery

Bone grafts are the second most common tissue transplanted in the United States, and they are an essential treatment tool in the field of acute and reconstructive traumatic orthopaedic surgery. Available in cancellous, cortical, or bone marrow aspirate form, autogenous bone graft is regarded as the gold standard in the treatment of posttraumatic conditions such as fracture, delayed union, and nonunion. However, drawbacks including donor-site morbidity and limited quantity of graft available for harvest make autograft a less-than-ideal option for certain patient populations. Advancements in allograft and bone graft substitutes in the past decade have created viable alternatives that circumvent some of the weak points of autografts. Allograft is a favorable alternative for its convenience, abundance, and lack of procurement-related patient morbidity. Options include structural, particulate, and demineralized bone matrix form. Commonly used bone graft substitutes include calcium phosphate and calcium sulfate synthetics-these grafts provide their own benefits in structural support and availability. In addition, different growth factors including bone morphogenic proteins can augment the healing process of bony defects treated with grafts. Autograft, allograft, and bone graft substitutes all possess their own varying degrees of osteogenic, osteoconductive, and osteoinductive properties that make them better suited for different procedures. It is the purpose of this review to characterize these properties and present clinical evidence supporting their indications for use in the hopes of better elucidating treatment options for patients requiring bone grafting in an orthopaedic trauma setting.

Current Updates on Bone Grafting Biomaterials and Recombinant Human Growth Factors Implanted Biotherapy for Spinal Fusion: A Review of Human Clinical Studies

BACKGROUND

Owing to their great promise in the spinal surgeries, bone graft substitutes have been widely investigated for their safety and clinical potential. By the current advances in the spinal surgery, an understanding of the precise biological mechanism of each bone graft substitute is mandatory for upholding the induction of solid spinal fusion.

OBJECTIVE

The aim of the present review is to critically discuss various surgical implications and level of evidence of most commonly employed bone graft substitutes for spinal fusion.

METHOD

Data was collected via electronic search using "PubMed", "SciFinder", "ScienceDirect", "Google Scholar", "Web of Science" and a library search for articles published in peer-reviewed journals, conferences, and e-books.

RESULTS

Despite having exceptional inherent osteogenic, osteoinductive, and osteoconductive features, clinical acceptability of autografts (patient's own bone) is limited due to several perioperative and postoperative complications i.e., donor-site morbidities and limited graft supply. Alternatively, allografts (bone harvested from cadaver) have shown great promise in achieving acceptable bone fusion rate while alleviating the donor-site morbidities associated with implantation of autografts. As an adjuvant to allograft, demineralized bone matrix (DBM) has shown remarkable efficacy of bone fusion, when employed as graft extender or graft enhancer. Recent advances in recombinant technologies have made it possible to implant growth and differentiation factors (bone morphogenetic proteins) for spinal fusion.

CONCLUSION

Selection of a particular bone grafting biotherapy can be rationalized based on the level of spine fusion, clinical experience and preference of orthopaedic surgeon, and prevalence of donor-site morbidities.

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.

The effect of embryonic origin on the osteoinductive potential of bone allografts

STATEMENT OF PROBLEM

Allografts with osteoinduction potential are widely used to augment bone in surgical and prosthetic rehabilitations. However, osteoinduction potential varies among commercially available allografts. Donor bones are derived from different embryonic origins, either the neural crest or mesoderm. Whether the origin of the bones affects the osteoinductivity of allograftsis is unclear.

PURPOSE

The purpose of this ex vivo study was to investigate the osteoinduction potential of allografts derived from bones with distinct embryonic origins.

MATERIAL AND METHODS

Allografts were obtained from human frontal and parietal bones at 2 different ages (fetal and adult). The specimens were divided into 4 groups: adult frontal (n=5), adult parietal (n=5), fetal frontal (n=10), and fetal parietal (n=10). Two investigations were conducted to assess the osteoinductive potential of these allografts. First, the osteogenesis of human osteoblasts exposed to these allografts were evaluated by analyzing the expression of runt-related transcription factor 2 (RUNX2), collagen type 1 alpha 2 chain (COL1A2), and bone gamma-carboxyglutamate protein (BGLAP) genes using quantitative real-time polymerase chain reaction (qRT-PCR). Second, the protein content of the adult frontal and parietal bone matrices was analyzed using liquid chromatography tandem mass spectrometry (LC-MS/MS). One-way ANOVA and the t test were used for statistical analyses of the gene and protein expression of the groups (α=.05).

RESULTS

No difference was found in the gene expression of the cells exposed to frontal or parietal bones. However, all 3 genes were significantly overexpressed in cells treated with fetal bones compared with adult bones. No difference was found in protein expression between adult frontal and adult parietal bones.

CONCLUSIONS

No difference was found in the osteoinductive capacity of frontal and parietal bones used as allografts. However, the osteoinductivity of fetal bones can be higher than that of adult bones. Further microanalyses are needed to determine the protein content of fetal bones.

In vitro and in vivo evaluation of xenogeneic bone putty with the carrier of hydrogel derived from demineralized bone matrix

The demineralized bone matrix (DBM) putty is a traditional bone graft utilized to facilitate the repair and reconstruction of bone. Recent studies indicated the DBM putties with the various carriers were different in bone repairing ability. In order to prepare a kind of DBM putty with a good biocompatibility and bioactivity, the DBM gel was processed from the DBM and the feasibility as a carrier for the DBM putty was evaluated. After the bovine DBM gel was prepared, the BMPs content as well as the ability to promote osteogenic differentiation of MC3T3-E1 cells in vitro were investigated. Then the DBM putty was prepared and filled into the rat calvarial defect model to evaluate the bone repairing ability by micro-CT and histology. The result showed there was 2.953 ± 0.054 ng BMP contained in per gram of the DBM gel. And the ALP production of MC3T3-E1 cells in the DBM gels group increased with prolonged culturing, the mineralized nodules formed in MC3T3-E1 cells on 14th day after co-culture. The putty prepared by DBM gel was easy to handle without loss of DBM particles at room temperature. In the rat calvarial bone defect experiment, histological observation showed more mature bone formed in the DBM putty group than that in the type I collagen group at 12 weeks, which indicated the bone putty prepared by DBM gel exhibited a better bone repair capability.

Extracellular matrix hydrogel therapies: In vivo applications and development

Decellularized extracellular matrix (ECM) has been widely used for tissue engineering applications and is becoming increasingly versatile as it can take many forms, including patches, powders, and hydrogels. Following additional processing, decellularized ECM can form an inducible hydrogel that can be injected, providing for new minimally-invasive procedure opportunities. ECM hydrogels have been derived from numerous tissue sources and applied to treat many disease models, such as ischemic injuries and organ regeneration or replacement. This review will focus on in vivo applications of ECM hydrogels and functional outcomes in disease models, as well as discuss considerations for clinical translation.

STATEMENT OF SIGNIFICANCE

Extracellular matrix (ECM) hydrogel therapies are being developed to treat diseased or damaged tissues and organs throughout the body. Many ECM hydrogels are progressing from in vitro models to in vivo biocompatibility studies and functional models. There is significant potential for clinical translation of these therapies since one ECM hydrogel therapy is already in a Phase 1 clinical trial.

Biomimetic matrix fabricated by LMP-1 gene-transduced MC3T3-E1 cells for bone regeneration

Bone healing is regulated by multiple microenvironmental signals provided by the extracellular matrix (ECM). This study aimed to mimic the native osteoinductive microenvironment by developing an ECM using gene-transduced cells. The LIM mineralization protein-1 (LMP-1) gene was transferred to murine pre-osteoblast cells (MC3T3-E1) using lentiviral vectors. Western blotting assay indicated that the MC3T3-E1 cells expressed an increased level of bone morphologic protein-2, -4 and -7 (BMP-2, -4 and -7) after LMP-1 gene transduction. The transduced cells were then seeded into calcined bovine bone scaffolds and cultured for 7, 14, and 21 days to construct ECMs on the scaffolds. The ECM-scaffold composites were then decellularized using the freeze-drying method. Scaffolds without ECM deposition were used as controls. The composites and controls were implanted into critical-sized bone defects created in the distal femurs of New Zealand rabbits. Twelve weeks after the surgery, both microcomputed tomography and histologic results indicated that the 7-day-cell-modified ECM-scaffold composites induced bone regeneration with significantly larger volume, trabecular thickness and connectivity than the controls. However, the 14- and 21-day-cell-modified ECM-scaffold composites triggered sustained inflammation response even at 12 weeks after the surgery and showed less bone ingrowth and integration than their 7-day-cell-modified counterparts. In conclusion, these results highlight the viable gene transfer techniques for manipulating cells in a constructed microenvironment of ECM for bone regeneration. However, the unresolved inflammation relating to the duration of ECM modification needs to be considered.

Biological Facet of Segmental Bone Loss Reconstruction

The management of long bone defects continues to be associated with significant challenges for optimum and timely bone repair. When bone grafting is needed, essential parameters to be addressed include adequate volume, optimum density, and structural capacity as well as potent biological properties. Although the autologous iliac crest bone graft remains the gold standard, its reduced availability and donor site morbidity have made the clinicians to seek for other alternative options. Reamer irrigator aspirator graft with materials used as graft expanders along with inductive molecules and cellular augmentation constitute the current trend for optimum bone regeneration. This article presents the contemporary thinking of the biological facet of segmental bone loss reconstruction.

Efficacy comparison of Accell Evo3 and Grafton demineralized bone matrix putties against autologous bone in a rat posterolateral spine fusion model

BACKGROUND CONTEXT

Spinal fusion procedures are intended to stabilize the spinal column for a multitude of disorders including abnormal curvature, traumatic instability, degenerative instability, and damage from infections or tumors. As an aid in the bone healing response, bone graft materials are used to bridge joints for arthrodesis and promote unions in pseudoarthrosis. Currently, the gold standard for stabilizing fusion masses in spinal procedures involves using the osteogenic, osteoinductive, and osteoconductive properties of autologous iliac crest corticocancellous bone. However, considerable morbidity is associated with harvesting the autologous graft. Donor site complications including infection, large hematomas, and pain have been reported at rates as high as 50% (Boden and Jeffrey, 1995). Biologically, the rate of bone repair dictates the rate at which the fusion mass will unite under autologous graft conditions.

PURPOSE

The purpose of this study is to compare the quality and rate of fusion between Accell Evo3 and Grafton demineralized bone matrix (DBM), with the gold standard iliac crest bone graft (ICBG) as the control, in athymic rat posterolateral fusion.

STUDY DESIGN

This study was a randomized, controlled study in a laboratory setting at the Hospital for Special Surgery in New York City. Blinded observations were made, which created an assessment of outcomes for successful fusions between each method.

PATIENT SAMPLE

Forty-eight (48) athymic rats were used in this study and underwent posterolateral lumbar fusion. They were assessed at either 3 weeks or 9 weeks to see the rate and efficacy of fusion.

OUTCOME MEASURES

Outcome measures will be the efficacy of the different bone grafts and their success rates of fusion in the rats.

METHODS

A comparison of the quality and rate of fusion between Accell Evo3® (DBM A) and Grafton (DBM B), with the gold standard iliac crest bone graft (ICBG) as the control, was performed using the established posterolateral intertransverse process on an athymic rat model. Materials were evaluated for fusion by several criteria, including manual palpation, standard and high-resolution radiographic imaging, micro-computed topography, and histologic analysis. Forty-eight (48) athymic rats received a bilateral intertransverse process fusion, using either bone from the iliac crest (control group), Accell Evo3, or Grafton. Twelve (12) rats (four from each group) were sacrificed at 3 weeks postoperatively, whereas the remaining thirty-six (36) were sacrificed at 9 weeks postoperatively. Three blinded observers examined the spines after the rats were euthanized, and they blindly assessed each rat for fusion success.

RESULTS

Manual palpation of the three different groups at 3 weeks postoperatively found successful fusion in 1 of 4 (25%) of the autologous bone graft (ABG) group and 4 of 4 (100%) of both DBM A and B groups. Manual palpation of the remaining animals that were sacrificed at 9 weeks postoperatively showed successful fusion in 4 of 12 (33%) of the ABG group, 8 of 12 (66%) of the DBM A group, and 12 of 12 (100%) of the DBM B group. Radiography found that 9 of 16 (56%) of the ABG group and 16 of 16 (100%) of both DBM Putty A and B groups had fused. Histologic analysis of the ABG group demonstrated less mature and less organized osteoid at both 3 and 9 weeks than the DBM Putty A and B groups. Nondestructive mechanical testing demonstrated increased stiffness in 4-point bending of both DBM A and B compared with ABG.

CONCLUSIONS

Both DBM-treated groups achieved a significantly higher rate of fusion than the ABG-treated group at 9 weeks in this model. Successful fusion was also demonstrated in the DBM-treated groups at 3 weeks.

Bone extracellular matrix hydrogel enhances osteogenic differentiation of C2C12 myoblasts and mouse primary calvarial cells

Hydrogel scaffolds derived from the extracellular matrix (ECM) of mammalian tissues have been successfully used to promote tissue repair in vitro and in vivo. The objective of this study was to evaluate the osteogenic potential of ECM hydrogels prepared from demineralized and decellularized bovine bone in the presence and absence of osteogenic medium. Culture of C2C12 and mouse primary calvarial cells (mPCs) on decellularized bone ECM (bECM) and demineralized bone matrix (DBM) gels resulted in increased expression of osteogenic gene markers, including a 3.6- and 13.4-fold increase in osteopontin and 15.7- and 27.1-fold increase in osteocalcin when mPCs were cultured upon bECM with basal and osteogenic media, respectively. bECM hydrogels stimulated the osteogenic differentiation of C2C12 and mPCs even in the absence of osteogenic medium. These results suggest that bECM hydrogel scaffolds may have great utility in future clinical applications for bone tissue engineering. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 900-908, 2018.

Laser Sintered Porous Ti-6Al-4V Implants Stimulate Vertical Bone Growth

The objective of this study was to examine the ability of 3D implants with trabecular-bone-inspired porosity and micro-/nano-rough surfaces to enhance vertical bone ingrowth. Porous Ti-6Al-4V constructs were fabricated via laser-sintering and processed to obtain micro-/nano-rough surfaces. Male and female human osteoblasts were seeded on constructs to analyze cell morphology and response. Implants were then placed on rat calvaria for 10 weeks to assess vertical bone ingrowth, mechanical stability and osseointegration. All osteoblasts showed higher levels of osteocalcin, osteoprotegerin, vascular endothelial growth factor and bone morphogenetic protein 2 on porous constructs compared to solid laser-sintered controls. Porous implants placed in vivo resulted in an average of 3.1 ± 0.6 mm³ vertical bone growth and osseointegration within implant pores and had significantly higher pull-out strength values than solid implants. New bone formation and pull-out strength was not improved with the addition of demineralized bone matrix putty. Scanning electron images and histological results corroborated vertical bone growth. This study indicates that Ti-6Al-4V implants fabricated by additive manufacturing to have porosity based on trabecular bone and post-build processing to have micro-/nano-surface roughness can support vertical bone growth in vivo, and suggests that these implants may be used clinically to increase osseointegration in challenging patient cases.

The Influences of Different Ratios of Biphasic Calcium Phosphate and Collagen Augmentation on Posterior Lumbar Spinal Fusion in Rat Model

PURPOSE

To determine the influence of different ratios of hydroxyapatite (HA)/beta tricalcium phosphate (β-TCP) and collagen augmentation for posterior lumbar fusion in a rat model.

MATERIALS AND METHODS

We generated a posterior lumbar fusion model in 50 rats and divided it into five groups of equal number as follows; 1) autologous bone graft as group A, 2) 70% HA+30% β-TCP as group B, 3) 70% HA+30% β-TCP+collagen as group C, 4) 30% HA+70% β-TCP as group D, and 5) 30% HA+70% β-TCP+collagen as group E. Rats were euthanized at 12 weeks after surgery and fusion was assessed by manual palpation, quantitative analysis using microCT and histology.

RESULTS

The score of manual palpation was significantly higher in group C than group E (3.1±1.1 vs. 1.8±0.8, p=0.033). However, in terms of microCT analysis, group D showed significantly higher scores than group B (5.5±0.8 vs. 3.1±1.1, p=0.021). According to quantitative volumetric analysis, 30% HA+70% β-TCP groups (group D and E) showed significantly reduced fusion mass at 12 weeks after surgery (123±14.2, 117±46.3 vs. 151±27.3, p=0.008, 0.003, respectively). Collagen augmentation groups revealed superior results in terms of both microCT score and histologic grade.

CONCLUSION

A 7:3 HA/β-TCP ratio with collagen augmentation rather than a 3:7 HA/β-TCP ratio could be a more favorable graft substitute for lumbar spinal fusion. There was positive role of collagen as an adjunct for spinal bone fusion process.

Biological enhancement of graft-tunnel healing in anterior cruciate ligament reconstruction

The sites where graft healing occurs within the bone tunnel and where the intra-articular ligamentization process takes place are the two most important sites of biological incorporation after anterior cruciate ligament (ACL) reconstruction, since they help to determine the mechanical behavior of the femur-ACL graft-tibia complex. Graft-tunnel healing is a complex process influenced by several factors, such as type of graft, preservation of remnants, bone quality, tunnel length and placement, fixation techniques and mechanical stress. In recent years, numerous experimental and clinical studies have been carried out to evaluate potential strategies designed to enhance and optimize the biological environment of the graft-tunnel interface. Modulation of inflammation, tissue engineering and gene transfer techniques have been applied in order to obtain a direct-type fibrocartilaginous insertion of the ACL graft, similar to that of native ligament, and to accelerate the healing process of tendon grafts within the bone tunnel. Although animal studies have given encouraging results, clinical studies are lacking and their results do not really support the use of the various strategies in clinical practice. Further investigations are therefore needed to optimize delivery techniques, therapeutic concentrations, maintenance of therapeutic effects over time, and to reduce the risk of undesirable effects in clinical practice.