Rapid quantitative bioassay of osteoinduction

Formulation and Characterization of a New Injectable Bone Substitute Composed PVA/Borax/CaCO3 and Demineralized Bone Matrix

The occurrence of bone-related disorders and diseases has dramatically increased in recent years around the world. Demineralized bone matrix (DBM) has been widely used as a bone implant due to its osteoinduction and bioactivity. However, the use of DBM is limited because it is a particulate material, which makes it difficult to manipulate and implant with precision. In addition, these particles are susceptible to migration to other sites. To address this situation, DBM is commonly incorporated into a variety of carriers. An injectable scaffold has advantages over bone grafts or preformed scaffolds, such as the ability to flow and fill a bone defect. The aim of this research was to develop a DBM carrier with such viscoelastic properties in order to obtain an injectable bone substitute (IBS). The developed DBM carrier consisted of a PVA/glycerol network cross-linked with borax and reinforced with CaCO3 as a pH neutralizer, porosity generator, and source of Ca. The physicochemical properties were determined by an injectability test, FTIR, SEM, and TGA. Porosity, degradation, bioactivity, possible cytotoxic effect, and proliferation in osteoblasts were also determined. The results showed that the developed material has great potential to be used in bone tissue regeneration.

Human decellularized bone scaffolds from aged donors show improved osteoinductive capacity compared to young donor bone

To improve the safe use of allograft bone, decellularization techniques may be utilized to produce acellular scaffolds. Such scaffolds should retain their innate biological and biomechanical capacity and support mesenchymal stem cell (MSC) osteogenic differentiation. However, as allograft bone is derived from a wide age-range, this study aimed to determine whether donor age impacts on the ability an osteoinductive, acellular scaffold produced from human bone to promote the osteogenic differentiation of bone marrow MSCs (BM-MSC). BM-MSCs from young and old donors were seeded on acellular bone cubes from young and old donors undergoing osteoarthritis related hip surgery. All combinations resulted in increased osteogenic gene expression, and alkaline phosphatase (ALP) enzyme activity, however BM-MSCs cultured on old donor bone displayed the largest increases. BM-MSCs cultured in old donor bone conditioned media also displayed higher osteogenic gene expression and ALP activity than those exposed to young donor bone conditioned media. ELISA and Luminex analysis of conditioned media demonstrated similar levels of bioactive factors between age groups; however, IGF binding protein 1 (IGFBP1) concentration was significantly higher in young donor samples. Additionally, structural analysis of old donor bone indicated an increased porosity compared to young donor bone. These results demonstrate the ability of a decellularized scaffold produced from young and old donors to support osteogenic differentiation of cells from young and old donors. Significantly, the older donor bone produced greater osteogenic differentiation which may be related to reduced IGFBP1 bioavailability and increased porosity, potentially explaining the excellent clinical results seen with the use of allograft from aged donors.

Conditioned medium of demineralized freeze-dried bone activates gene expression in periodontal fibroblasts in vitro

BACKGROUND

Demineralized bone matrix (DBM) is used for the treatment of osseous defects. Conditioned medium from native bone chips can activate transforming growth factor (TGF)-β signaling in mesenchymal cells. The aim of this study is to determine whether processing of native bone into DBM affects the activity of the conditioned medium.

METHODS

Porcine cortical bone blocks were subjected to defatting, different concentrations of hydrochloric acid, and various temperatures. DBM was lyophilized, ground, and placed into culture medium. Human gingiva and periodontal fibroblasts were exposed to the respective conditioned medium obtained from DBM (DBCM). Changes in the expression of TGF-β target genes were determined.

RESULTS

DBCM altered the expression of TGF-β target genes (e.g., adrenomedullin, pentraxin 3, KN motif and ankyrin repeat domains 4, interleukin 11, NADPH oxidase 4, and BTB [POZ] domain containing 11) by at least five-fold. The response was observed in fibroblasts from both sources. Defatting lowered the activity of DBCM. The TGF-β receptor type I kinase inhibitor SB431542 [4-(4-(benzo[d][1,3]dioxol-5-yl)-5-(pyridin-2-yl)-1H-imidazol-2-yl)benzamide] but not the inhibitor of bone morphogenetic protein receptor dorsomorphin, blocked the effects of DBCM on gene expression. Moreover, conditioned medium obtained from commercial human DBM modulated the expression of TGF-β target genes.

CONCLUSION

The findings suggest that the DBCM can activate TGF-β signaling in oral fibroblasts.

Guided bone regeneration using demineralized allogenic bone matrix with calcium sulfate: case series

PURPOSE

The purpose of this case series was to evaluate the effect of guided bone regeneration using demineralized allogenic bone matrix with calcium sulfate.

MATERIALS AND METHODS

Guided bone regeneration using Demineralized Allogenic Bone Matrix with Calcium Sulfate (AlloMatrix™, Wright. USA) was performed at the time of implant placement from February 2010 to April 2010. At the time of the second surgery, clinical evaluation of bone healing and histologic evaluation were performed. The study included 10 patients, and 23 implants were placed. The extent of bony defects around implants was determined by measuring the horizontal and vertical bone defects using a periodontal probe from the mesial, distal, buccal, and lingual sides and calculating the mean and standard deviation of these measurements. Wedge-shaped tissue samples were obtained from 3 patients and histologic examination was performed.

RESULTS

In clinical evaluation, it was observed that horizontal bone defects were completely healed with new bones, and in the vertical bone defect area, 15.1% of the original defect area remained. In 3 patients, histological tests were performed, and 16.7-41.7% new bone formation was confirmed. Bone graft materials slowly underwent resorption over time.

CONCLUSION

AlloMatrix™ is an allograft material that can be readily manipulated. It does not require the use of barrier membranes, and good bone regeneration can be achieved with time.

The deep-sea natural products, biogenic polyphosphate (Bio-PolyP) and biogenic silica (Bio-Silica), as biomimetic scaffolds for bone tissue engineering: fabrication of a morphogenetically-active polymer

Bone defects in human, caused by fractures/nonunions or trauma, gain increasing impact and have become a medical challenge in the present-day aging population. Frequently, those fractures require surgical intervention which ideally relies on autografts or suboptimally on allografts. Therefore, it is pressing and likewise challenging to develop bone substitution materials to heal bone defects. During the differentiation of osteoblasts from their mesenchymal progenitor/stem cells and of osteoclasts from their hemopoietic precursor cells, a lineage-specific release of growth factors and a trans-lineage homeostatic cross-talk via signaling molecules take place. Hence, the major hurdle is to fabricate a template that is functioning in a way mimicking the morphogenetic, inductive role(s) of the native extracellular matrix. In the last few years, two naturally occurring polymers that are produced by deep-sea sponges, the biogenic polyphosphate (bio-polyP) and biogenic silica (bio-silica) have also been identified as promoting morphogenetic on both osteoblasts and osteoclasts. These polymers elicit cytokines that affect bone mineralization (hydroxyapatite formation). In this manner, bio-silica and bio-polyP cause an increased release of BMP-2, the key mediator activating the anabolic arm of the hydroxyapatite forming cells, and of RANKL. In addition, bio-polyP inhibits the progression of the pre-osteoclasts to functionally active osteoclasts. Based on these findings, new bioinspired strategies for the fabrication of bone biomimetic templates have been developed applying 3D-printing techniques. Finally, a strategy is outlined by which these two morphogenetically active polymers might be used to develop a novel functionally active polymer.

Demineralized bone matrix in bone repair: history and use

Demineralized bone matrix (DBM) is an osteoconductive and osteoinductive commercial biomaterial and approved medical device used in bone defects with a long track record of clinical use in diverse forms. True to its name and as an acid-extracted organic matrix from human bone sources, DBM retains much of the proteinaceous components native to bone, with small amounts of calcium-based solids, inorganic phosphates and some trace cell debris. Many of DBM's proteinaceous components (e.g., growth factors) are known to be potent osteogenic agents. Commercially sourced as putty, paste, sheets and flexible pieces, DBM provides a degradable matrix facilitating endogenous release of these compounds to the bone wound sites where it is surgically placed to fill bone defects, inducing new bone formation and accelerating healing. Given DBM's long clinical track record and commercial accessibility in standard forms and sources, opportunities to further develop and validate DBM as a versatile bone biomaterial in orthopedic repair and regenerative medicine contexts are attractive.

Bone products in surgery: a blueprint for standardization

Surgical facilities often stock many types of bone and bone products to meet the needs of multiple surgeons. In this era of cost containment, product standardization is necessary for the financial well-being of health care facilities. By familiarizing themselves with bone and bone product harvesting and processing and the US Food and Drug Administration requirements for approval of these products, perioperative nurses and managers can more easily standardize the bone and tissue products stocked and reduce costs. Steps toward standardization include establishing a multidisciplinary surgical product use committee to evaluate products used in the OR, limiting the number of tissue vendors for the facility to as few as possible, completing a product inventory to identify what is currently available, and constructing charts to share with surgeons that provide the rationales for standardizing products.

Dual effect of inorganic polymeric phosphate/polyphosphate on osteoblasts and osteoclasts in vitro

Inorganic polymeric phosphate/polyphosphate (polyP) is a natural polymer existing in both pro- and eukaryotic systems. In the present study the effect of polyP as well as of polyP supplied in a stoichiometric ratio of 2 m polyP:1 m CaCl2 [polyP (Ca(2+) complex)] on the osteoblast-like SaOS-2 cells and the osteoclast-like RAW 264.7 cells was determined. Both polymers are non-toxic for these cells up to a concentration of 100 µm. In contrast to polyP, polyP (Ca(2+) complex) significantly induced hydroxyapatite formation at a concentration > 10 µm, as documented by alizarin red S staining and scanning electron microscopic (SEM) inspection. Furthermore, polyP (Ca(2+) complex) triggered in SaOS-2 cells transcription of BMP2 (bone morphogenetic protein 2), a cytokine involved in maturation of hydroxyapatite-forming cells. An additional activity of polyP (Ca(2+) complex) is described by showing that this polymer impairs osteoclastogenesis. At concentrations > 10 µm polyP (Ca(2+) complex) slows down the progression of RAW 264.7 cells to functional osteoclasts, as measured by the expression of TRAP (tartrate-resistant acid phosphatase). Finally, it is shown that 10-100 µm polyP (Ca(2+) complex) inhibited phosphorylation of IκBα by the respective kinase in RAW 264.7 cells. We concluded that polyP (Ca(2+) complex) displays a dual effect on bone metabolizing cells. It promotes hydroxyapatite formation in SaOS-2 cells (osteoblasts) and impairs maturation of the osteoclast-related RAW 264.7 cells.

Delivery of demineralized bone matrix powder using a thermogelling chitosan carrier

Demineralized bone matrix (DBM) powder is widely used for bone regeneration due to its osteoinductivity and osteoconductivity. However, difficulties with handling, its tendency to migrate from graft sites, and lack of stability after surgery can sometimes limit the clinical utility of this material. In this work, the possibility of using a thermogelling chitosan carrier to deliver DBM powder was assessed. The DBM-thermogelling putty improved handling and formed a gel-like composite in situ at body temperature within a clinically relevant time period. The properties of the formed composite, including morphology, porosity, mechanical properties, equilibrium swelling as well as degradability, are significantly influenced by the ratio of DBM to thermogelling chitosan. The in vitro study showed that the alkaline phosphatase activity of C2C12 cells encapsulated in the composite was steadily increased with culture time. The in vivo study showed that increased DBM content in the DBM-thermogelling chitosan induced ectopic bone formation in a nude rat model. The diffusion of growth factor from the DBM-thermogelling chitosan as well as the host-implant interactions are discussed.

Biosilica-based strategies for treatment of osteoporosis and other bone diseases

Osteoporosis is a common disease in later life, which has become a growing public health problem. This degenerative bone disease primarily affects postmenopausal women, but also men may suffer from reduced bone mineral density. The development of prophylactic treatments and medications of osteoporosis has become an urgent issue due to the increasing proportion of the elderly in the population. Apart from medical/hormonal treatments, current strategies for prophylaxis of osteoporosis are primarily based on calcium supplementation as a main constituent of bone hydroxyapatite mineral. Despite previous reports suggesting an essential role in skeletal growth and development, the significance of the trace element silicon in human bone formation has attracted major scientific interest only rather recently. The interest in silicon has been further increased by the latest discoveries in the field of biosilicification, the formation of the inorganic silica skeleton of the oldest still extant animals on Earth, the sponges, which revealed new insights in the biological function of this element. Sponges make use of silicon to build up their inorganic skeleton which consists of biogenously formed polymeric silica (biosilica). The formation of biosilica is mediated by specific enzymes, silicateins, which have been isolated, characterized, and expressed in a recombinant way. Epidemiological studies revealed that dietary silicon reduces the risk of osteoporosis and other bone diseases. Recent results allowed for the first time to understand the molecular mechanism underlying the protective effect of silicic acid/biosilica against osteoporosis. Biosilica was shown to modulate the ratio of expression of two cytokines involved in bone formation-RANKL and osteoprotegerin. Hence, biosilica has been proposed to have a potential in prophylaxis and therapy of osteoporosis and related bone diseases.

Osteogenic potential of biosilica on human osteoblast-like (SaOS-2) cells

Biosilica is a natural polymer, synthesized by the poriferan enzyme silicatein from monomeric silicate substrates. Biosilica stimulates mineralizing activity and gene expression of SaOS-2 cells. To study its effect on the formation of hydroxyapatite (HA), SaOS-2 cells were grown on different silicatein/biosilica-modified substrates (bone slices, Ca-P-coated coverslips, glass coverslips). Growth on these substrates induced the formation of HA nodules, organized in longitudinal arrays or spherical spots. Nodules of sizes above 1 μm were composed of irregularly arranged HA prism-like nanorods, formed by aggregates of three to eight SaOS-2 cells. Moreover, growth on silicatein/biosilica-modified substrates elicited increased [(3)H]dT incorporation into DNA, indicative of enhanced cell proliferation. Consequently, an in vitro-based bioassay was established to determine the ratio between [(3)H]dT incorporation and HA formation. This ratio was significantly higher for cells that grew on silicatein/biosilica-modified substrates than for cells on Ca-P-coated coverslips or plain glass slips. Hence, we propose that this ratio of in vitro-determined parameters reflects the osteogenic effect of different substrates on bone-forming cells. Finally, qRT-PCR analyses demonstrated that growth of SaOS-2 cells on a silicatein/biosilica matrix upregulated BMP2 (bone morphogenetic protein 2, inducer of bone formation) expression. In contrast, TRAP (tartrate-resistant acid phosphatase, modulator of bone resorption) expression remained unaffected. We conclude that biosilica shows pronounced osteogenicity in vitro, qualifying this material for studies of bone replacement also in vivo.

Demineralized bone matrix for fracture healing: fact or fiction?

Demineralized bone matrix (DBM) has been touted as an excellent grafting material; however, there are no Level I studies that use DBM alone in humans to back up this claim. DBM functions best in a healthy tissue bed but should be expected to have little impact in an anoxic or avascular tissue bed, a situation often encountered in traumatic orthopaedic pathologies. Moreover, there is some evidence of differential potencies of DBM preparations based on donor variability and the manufacturing process. DBM efficacy may also be related to its formulation and the various carriers used. The fact that DBM is an allogeneic material opens up the potential for disease transmission. In addition, DBM activity may be altered by the hormonal status or nicotine use of a patient. In summary, although DBM has proven effective for bone induction in lower form animals, the translation to human clinical use for fracture healing, and the burden of proof, remains.

Irradiated human chondrocytes expressing bone morphogenetic protein 2 promote healing of osteoporotic bone fracture in rats

Bone morphogenetic protein 2 (BMP2) was selected as a transgene to regenerate osteoporotic bone defects after several BMPs were tested using a bone formation study in nude mice. Human chondrocytes were transduced with a BMP2-containing retroviral vector, and single clones were selected. The cells were characterized over numerous passages for growth and BMP2 expression. The single clones were irradiated and tested for viability. BMP2 expression lasted for 3 weeks before dying off completely after approximately 1 month. Irradiated and non-irradiated transduced chondrocytes successfully healed fractures in osteoporotic rats induced by ovariectomy. The osteoinducing effect of irradiated cells was better than that of their non-irradiated counterparts or a chondrocytes-only control. This study showed that delivering BMP2 from the transduced and irradiated chondrocytes could be an effective and safe method of repairing osteoporotic bone fractures.

Biomechanical and Radiographic Comparison of Demineralized Bone Matrix, and a Coralline Hydroxyapatite in a Rabbit Spinal Fusion Model

The use of bone grafts is an essential component in spinal fusion. Autologous bone has been shown to result in long-term stable arthrodesis between spinal motion segments. However, autograft can be associated with significant morbidity and a limited supply. Alternatives, such as allogeneic demineralized bone matrix (DBM), are a potential source and supplement to autograft bone. The current study compares the ability of a DBM product (BioSet® RT) and a coralline hydroxyapatite (Pro Osteon® 500R), for inducing spinal fusion in a rabbit model. BioSet® RT, alone or in combination with autograft, and Pro Osteon® 500R were implanted in the posterior lateral inter-transverse process region of the rabbit spine. The spines were evaluated at 18 weeks for fusion of the L4—L5 transverse processes using a total of 33 skeletally mature male rabbits; 4 naïve animals were also included in the study. Samples were evaluated radiographically, histologically, by palpation, and through mechanical strength testing. Radiographical, histological, and palpation measurements demonstrated the ability of BioSet® RT to induce new bone formation and bridging fusion comparable to autograft. This material performed well alone or in combination with autograft material. Despite significantly higher biomechanical testing results, minimal bone formation and fusion was recorded for the Pro Osteon® 500R-treated group. This in vivo study demonstrates the ability of BioSet®RT to induce new bone formation, and there was a clear relationship between bridging bone and mechanical strength.

Histological and radiographic evaluations of demineralized bone matrix and coralline hydroxyapatite in the rabbit tibia

Complex fractures resulting in bone loss or impaired fracture healing remain problematic in trauma and orthopedic surgeries. Many bone graft substitutes have been developed and are commercially available. These products differ in their osteoconductive and osteoinductive properties. Differential enhancement of these properties may optimize the performance of these products for various orthopedic and craniofacial applications. The use of bone graft substitutes offers the ability to lessen the possible morbidity of the harvest site in autografts. The objective of the present study was to compare the ability of two bone graft substitutes, BioSet RT, an allograft demineralized bone matrix formulation, and ProOsteon 500R, a coralline hydroxyapatite, in a rabbit critical tibial defect model. BioSet RT and ProOsteon 500R were implanted into a unicortical proximal metaphyseal tibial defect and evaluated for new bone formation. Samples were analyzed radiographically and histologically at 1 day, 6 weeks, 12 weeks, and 24 weeks post surgery. Both materials were biocompatible and demonstrated significant bone growth and remodeling. At 12 weeks, the BioSet RT implanted sites demonstrated significantly more defect closure and bone remodeling as determined by radiographic analyses with 10 out of 14 defects being completely healed versus 1 out of 14 being completely healed in the ProOsteon 500R implanted sites. At 24 weeks, both materials demonstrated complete closure of the defect as determined histologically. There were no statistical differences in radiographic scores between the two implanted materials. However, there was an observable trend that the BioSet RT material generated higher histological and radiographic scores, although not statistically significant. This study provides evidence that both BioSet RT and ProOsteon 500R are biocompatible and able to induce new bone formation as measured in this rabbit model. In addition, this in vivo study demonstrates the ability of BioSet RT to induce new bone formation in a shorter timeframe than ProOsteon 500R.

Quantification of various growth factors in different demineralized bone matrix preparations

Besides autografts, allografts, and synthetic materials, demineralized bone matrix (DBM) is used for bone defect filling and treatment of non-unions. Different DBM formulations are introduced in clinic since years. However, little is known about the presents and quantities of growth factors in DBM. Aim of the present study was the quantification of eight growth factors important for bone healing in three different "off the shelf" DBM formulations, which are already in human use: DBX putty, Grafton DBM putty, and AlloMatrix putty. All three DBM formulations are produced from human donor tissue but they differ in the substitutes added. From each of the three products 10 different lots were analyzed. Protein was extracted from the samples with Guanidine HCL/EDTA method and human ELISA kits were used for growth factor quantification. Differences between the three different products were seen in total protein contend and the absolute growth factor values but also a large variability between the different lots was found. The order of the growth factors, however, is almost comparable between the materials. In the three investigated materials FGF basic and BMP-4 were not detectable in any analyzed sample. BMP-2 revealed the highest concentration extractable from the samples with approximately 3.6 microg/g tissue without a significant difference between the three DBM formulations. In DBX putty significantly more TGF-beta1 and FGFa were measurable compared to the two other DBMs. IGF-I revealed the significantly highest value in the AlloMatrix and PDGF in Grafton. No differences were accessed for VEGF. Due to the differences in the growth factor concentration between the individual samples, independently from the product formulation, further analyzes are required to optimize the clinical outcome of the used demineralized bone matrix.

Safety and efficacy of use of demineralised bone matrix in orthopaedic and trauma surgery

Demineralised bone matrix (DBM) acts as an osteoconductive, and possibly as an osteoinductive, material. It is widely used in orthopaedic, neurosurgical, plastic and dental areas. More than 500,000 bone grafting procedures with DBM are performed annually in the US. It does not offer structural support, but it is well suited for filling bone defects and cavities. The osteoinductive nature of DBM is presumably attributed to the presence of matrix-associated bone morphogenetic proteins (BMPs) and growth factors, which are made available to the host environment by the demineralisation process. Clinical results have not been uniformly favourable; however, a variable clinical response is attributed partly to nonuniform processing methods found among numerous bone banks and commercial suppliers. DBMs remain reasonably safe and effective products. The ultimate safe bone-graft substitute, one that is osteoconductive, osteoinductive, osteogenic and mechanically strong, remains elusive.

Intervariability and intravariability of bone morphogenetic proteins in commercially available demineralized bone matrix products

STUDY DESIGN

Enzyme-linked immunosorbent assay was used to detect bone morphogenetic proteins (BMPs) 2, 4, and 7 in 9 commercially available ("off the shelf") demineralized bone matrix (DBM) product formulations using 3 different manufacturer's production lots of each DBM formulation.

OBJECTIVES

To evaluate and compare the quantity of BMPs among several different DBM formulations (inter-product variability), as well as examine the variability of these proteins in different production lots within the same DBM formulation (intra-product variability).

SUMMARY OF BACKGROUND DATA

DBMs are commonly used to augment available bone graft in spinal fusion procedures. Surgeons are presented with an ever-increasing variety of commercially available human DBMs from which to choose. Yet, there is limited information on a specific DBM product's osteoinductive efficacy, potency, and constancy.

METHODS

There were protein extracts from each DBM sample separately dialyzed 4 times against distilled water at 4 degrees C for 48 hours. The amount of BMP-2, BMP-4, and BMP-7 was determined using enzyme-linked immunosorbent assay. RESULTS.: The concentrations of detected BMP-2 and BMP-7 were low for all DBM formulations, only nanograms of BMP were extracted from each gram of DBM (20.2-120.6 ng BMP-2/g DBM product; 54.2-226.8 ng BMP-7/g DBM). The variability of BMP concentrations among different lots of the same DBM formulation, intra-product variability, was higher than the variability of concentrations among different DBM formulations, inter-product variability (coefficient of variation range BMP-2 [16.34% to 76.01%], P < 0.01; BMP-7 [3.71% to 82.08%], P < 0.001). BMP-4 was undetectable.

CONCLUSIONS

The relative quantities of BMPs in DBMs are low, in the order of 1 x 10(-9) g of BMP/g of DBM. There is higher variability in concentration of BMPs among 3 different lots of the same DBM formulation than among different DBM formulations. This variability questions DBM products' reliability and, possibly, efficacy in providing consistent osteoinduction.

Allograft and alloplastic bone substitutes: a review of science and technology for the craniomaxillofacial surgeon

Bone healing is a complex and multifactorial process. As such, there are numerous steps in the process to which intervention can be directed. This has given rise to many bone graft technologies that have been used to regenerate bone, creating, perhaps, a bewildering array of options. The options that surgeons have the most familiarity with are the ones that have been available the longest (i.e., autograft and allograft). Although useful for the widest spectrum of clinical applications, limitations of these grafts has prompted the development of new materials. Demineralized bone matrix formulations and synthetic ceramic materials are now being used with greater frequency. These biomaterials have demonstrated their usefulness in facial plastic and reconstructive surgery with their ability to augment and replace portions of the craniofacial skeleton. The purpose of this article is to describe and discuss the allograft and alloplastic bone grafting technologies so that the reader can consider each in the context of the others and gain a better appreciation for how each fits into the universe of existing and emerging treatments for bone regeneration.

Assay of Bone Morphogenetic Protein-2, -4, and -7 in Human Demineralized Bone Matrix

Demineralized bone matrix (DBM) is a widely used bone graft material that derives its osteoinductive potential from matrix-associated bone morphogenetic proteins (BMPs). Prior investigations have shown that the osteoinductive potential can vary widely, with influence from both donor and processing sources. Although it is plausible that donor variance in the BMP profile can be an important consideration, the few published studies available have given inconsistent and incomplete information about this. The goal was to (1) characterize the variance of BMP-2, BMP-4, and BMP-7 in fully demineralized DBM derived from 20 appropriately screened (Food and Drug Administration and the American Association of Tissue Banks criteria) donors (male and female, 17-65 years) and (2) using literature review, infer the potential for this to be an important source of variability in graft function. BMPs were extracted with 4 M guanidine hydrochloride, and levels of BMP-2, BMP-4, and BMP-7 were measured using enzyme-linked immunosorbent assay. Measured levels were as follows: BMP-2 = 21.4 +/- 12.0 ng/g DBM, BMP-4 = 5.45 +/- 2.04 ng/g DBM, and BMP-7 = 84.1 +/- 34.4 ng/g DBM, which were significantly different (P < 0.05). There was a positive linear correlation between BMP-2 and BMP-7 (P = 0.0227). DBM derived from female donors had significantly greater concentrations of BMP-2 and BMP-7 than did that derived from male donors (P = 0.0257 and 0.0245, respectively). There was no significant correlation between donor age and the levels of any of the measured BMPs. The magnitude of variance of BMP profile appears to reasonably well correspond to the variance in osteoinductive potential cited by others, suggesting the possibility of using this as a method of donor screening.

Demineralized bone matrix graft: a scientific and clinical case study assessment

Osteoinductive demineralized bone matrix results from bone demineralization and is attributed to matrix-associated bone morphogenetic proteins. The osteoinductive potential can vary with donor. Many bioassay methods are available to screen donors, each with its own interpretation, so performance of more than one may be of value. Furthermore, little is known about the relationship between bioassay results and clinical outcomes. A study designed to meaningfully explore these issues would require assay of a large number of donors as well as clinical utilization in a large patient population. A preliminary study was undertaken to gain initial perspective. Using demineralized bone matrix derived from one 33-year-old female donor, 2 methods of bioassay and a clinical case study were performed. The levels of bone morphogenetic proteins 2, 4, and 7 in lyophilized demineralized bone matrix powder were measured (19.65 +/- 0.30 ng/g, 2.49 +/- 0.19 ng/g, and 82.03 +/- 6.89 ng/g, respectively). Also, putty (Osteostim DBM Putty), prepared from powder, was intramuscularly implanted in athymic rats and de novo bone formation quantified (6.7% +/- 3.5% new bone formation with 49% +/- 17% of the implant area associated with new bone formation). The putty, in conjunction with internal fixation, was used in the revision of a medial malleolar nonunion of an obese, 76-year-old woman. Radiographic union with excellent graft incorporation was achieved by 12 weeks postoperatively, with maintenance of an acceptable clinical result during the 14-month follow-up period. These results are interpreted in the broader context of demineralized bone grafting, in general, and an outline for further study is presented.

A review of osteoinductive testing methods and sterilization processes for demineralized bone

Allogeneic demineralized bone has been used extensively as a clinical graft material because it has osteoinductive and osteoconductive properties. Concerns over processing and terminal sterilization procedures that may reduce performance have led clinicians to call for assurances of product potency. There is extensive experience on effects of demineralized bone in animal and cell culture models with the possibility for future evidence-based standards for release of products. Evaluation of the current state of knowledge leads to the fact that we cannot conclude that performance of different lots of demineralized bone allografts in in vivo or in vitro test systems can be used as a measure of clinical performance. It may be possible to adopt an osteoinductivity standard for release-to-market, but it should be followed by clinical monitoring and further research.

Treatment of benign bone lesions with an injectable calcium sulfate-based bone graft substitute

The treatment of benign bone lesions can be challenging due to the limited quantity of autogenous graft available for harvest and grafting of the defect. The use of an injectable calcium bone graft substitute, Minimally-Invasive Injectable Graft (MIIG) (Wright Medical Technology, Inc, Arlington, Tenn), material for treatment of these bone lesions is advantageous. Calcium sulfate has a long-standing history in the treatment of bone voids secondary to trauma, infection, or neoplastic processes. Minimally-Invasive Injectable Graft injectable calcium sulfate graft may be injected into surgically created osseous defects or bone defects secondary to traumatic injury. After hardening, the paste acts as a temporary intraosseous support through which internal fixation may be placed. Fifteen patients with benign space-occupying lesions were treated with curettage and grafting with an injectable, surgical-grade, calcium sulfate bone graft substitute. Bone healing was assessed postoperatively and defined as resorption of the bone graft substitute material and replacement with new bone formation. The grafted defects in 14 of the 15 patients showed complete incorporation of the graft material at an average of 8 weeks. One patient required incision and drainage for a deep infection 5 weeks postoperatively. The average follow-up was 6 months (range: 3-15 months), and Musculoskeletal Tumor Society functional outcome scores averaged 83%. This injectable, minimally invasive graft material is easy to use, provides a temporary structural support when grafting bone defects, and results in predictable rapid bone healing.

Use of cancellous bone chips and demineralized bone matrix in the treatment of acetabular osteolysis: preliminary 2-year follow-up

Twenty patients (20 hips) who had cementless acetabular revision arthroplasty and were treated with cancellous bone chips mixed with demineralized bone matrix to fill the cavitary defects were studied. At 2-years' follow-up, the grafts were fully incorporated in 18 patients. In addition, the mean Harris Hip Score increased to 89 points from a mean preoperative score of 29 points for the surviving hips. These preliminary findings suggest that the prepackaged demineralized bone matrix and cancellous chips can provide acceptable radiographic and clinical results as an adjunct in the treatment of contained osteolytic acetabular defects.

Quantitative and sensitive in vitro assay for osteoinductive activity of demineralized bone matrix

A sensitive, rapid, reliable and quantitative method to check the bone forming potential of demineralized bone matrix (DBM) has been developed. The osteoinductivity of the bone morphogenetic proteins (BMPs), present in DBM, can be measured in vitro using a pluripotent myoblast C2C12 cell line. Alkaline phosphatase activity induced by co-incubation of DBM with C2C12 cells was dose-responsive and corresponds to the amount of active BMPs in DBM. Bone forming potential was simultaneously tested in vivo by implanting DBM intra-muscularly in nude rats. ALP activity induced in C2C12 cells, correlated with bone formation in vivo (r=0.88), determined by alkaline phosphatase activity, mineralization density and histomorphology of the DBM explants. Results from DBM batches, originating from five established Bone Banks, showed good consistency between in vitro and in vivo assays. However, DBM activity varied widely from bank to bank as well as from batch to batch within the same bank.

The effect of allomatrix injectable putty on the outcome of long bone applications

Long bone defects due to nonunion or surgical excision of benign bone tumors result in areas that require rapid regeneration of local bone. This clinical and radiographic article details the results of a commercially prepared allograft demineralized bone matrix in patients with long bone voids or gaps. Of the 76 patients included for study, 41 (54%) patients were undergoing surgical intervention for removal of benign tumors or space-occupying lesions and 35 (46%) patients had long bone nonunions. AlloMatrix Injectable Putty (Wright Medical Technology, Inc, Arlington, Tenn) was used alone in 74 (97%) patients and in combination with bone marrow aspirate in two (3%) patients with tibial nonunion. Adjunctive strut allografts were used in three patients with humeral nonunion. The average time to follow-up for the combined population was 7 months (nonunion group 6 months; benign tumor group 7 months). At the most recent follow-up, radiographic evidence of the average percent of bone healing was 85.1% for the nonunion patient group and 93% for the benign tumor patient group. From this study, AlloMatrix Injectable Putty used as a bone void filler in long bone nonunions and benign tumors shows results equal to those historically reported for autograft and other materials.

Comparative evaluation of the osteoinductivity of two formulations of human demineralized bone matrix

In the United States, demineralized bone matrix (DBM) is considered a transplantable tissue and therefore is regulated primarily by the American Association of Tissue Banks. Even though DBM is not subjected to the same regulations relative to performance claims as medical devices are, one would expect different processing methods might yield DBM preparations of different osteoinductive potential. The purpose of this study was to use an established athymic rat model to compare the osteoinductive properties of two commercially available human DBMs prepared using different methods but having essentially identical product claims. Sixteen female athymic rats were used to test equivalent volumes of two lots each of Grafton Putty (Osteotech, Inc., Eatontown, NJ), Osteofil (Regeneration Technologies, Inc., Alachua, FL), and rat DBM. At 28 days after implantation, qualitative and semiquantitative microscopy showed no significant differences in bone formation between the two lots from each source, but rat DBM produced significantly more bone than Grafton, which produced significantly more bone than Osteofil. Our results suggest that methods of graft processing may represent a greater source of variability than do differences among individual donors. Whether these differences relate to methods of demineralization, carrier, dose of DBM per volume, or to some other factor remains to be determined.

Demineralized bone matrix and native bone morphogenetic protein in orthopaedic surgery

The recognition that demineralized bone matrix could induce bone formation when placed in mammalian skeletal muscle led to preclinical studies of crude native insoluble bone morphogenetic protein and noncollagenous protein, followed by the clinical application of demineralized bone matrix, chemosterilized autolyzed antigen-extracted allogenic bone, and autolyzed antigen-extracted allogenic bone matrix gelatin. Cultural norms and regulatory agencies influence the availability of different demineralized bone matrix preparations in different parts of the world, but there is continued interest in the biologic structure of native insoluble bone morphogenetic protein and noncollagenous protein aggregates and the applied science of osteoinduction and osteoconduction in reconstructive orthopaedic surgery. Demineralized bone matrix is not widely available in Asia, but tissue processing facilities in the United States distribute demineralized bone matrix materials with different carriers, handling properties, and possibly osteoinductive potential. The purpose of the current study was to review the development and use of various preparations of demineralized bone matrix materials.