ABSTRACT

Clinicians await the availability of synthetic bioimplants that will replace the need for autogeneic bone grafts in bone reconstructive surgery. For more than a decade, researchers have evaluated delivery vehicles for the tissue morphogen bone morphogenetic protein. The object of this investigation was to measure induced bone development when bone morphogenetic protein was delivered by human tendon collagen, human demineralized bone matrix, hydroxyapatite, a composite of human tendon collagen and human demineralized bone matrix (tendon collagen + demineralized bone matrix), Poloxamer 407, and a composite of human demineralized bone matrix and Poloxamer 407. Sixty-three adult male Swiss Webster mice (Harlan Sprague–Dawley, Indianapolis, IN) received 126 implants. The animals were divided into seven groups of nine animals, depending on carrier (six carriers plus the positive control group) used. Each animal received a bone morphogenetic protein-enhanced carrier in one hindquarter muscle mass, with the contralateral leg being implanted with the carrier alone. Implants were evaluated by quantitative radiomorphometry validated by histologic methods. Radiographically, no significant differences were identified among any of the implants evaluated (p> 0.05). Histomorphometric analysis demonstrated that Poloxamer 407 was significantly (p< 0.05) better at delivering bone morphogenetic protein than the other carriers involved in this investigation. The new bone developed in a tubular or spherical shape. Interaction of endogenous and exogenous delivery systems seems to be essential for optimal transmission of bone morphogenetic protein. The importance of the excipient to deliver bone morphogenetic protein and develop a bone morphogenetic protein concentration gradient has been emphasized by other investigators and confirmed by our research on poloxamer. With further research on the physicochemical mechanisms of localization and transmission of bone morphogenetic protein, it may be possible to avoid hazardous operations with autogeneic bone.

ABSTRACT

Collagen and poloxamer are effective carriers for the delivery and retention of DBM and other bone regenerating factors at the surgical site. Collagen sponge, both by retention of the DBM or growth factor and by acting as an osteoconductive scaffold, facilitates the inward migration, proliferation and differentiation of mesenchymal and osteoprogenitor cells into bone-forming tissue. When dissolved in water, the poloxamer demonstrates reverse thermal behavior since, at low ambient temperatures it is a fluid liquid (sol) but at higher body temperatures it forms a viscous liquid (gel). The poloxamer is non-toxic, readily administered, and can facilitate the action of DBM or growth factors by retention and slow release of bioactive material at the surgical site. DynaGraft® Matrix is a collagen sponge containing DBM; both tissues are derived from the same human donor. DynaGraft Gel and Putty contain human DBM dispersed in aqueous poloxamer. Poloxamer, collagen, DBM and hydroxyapatite have been tested for their ability to carry and release BMP, TGFβ1, and OSA peptide in experimental bone defect sites. Poloxamer appears to be a superior vehicle for the delivery of osteogenic proteins. This may be due to retention and slow release of the bioactive protein at the wound site. Each lot of tissue bank derived DBM used in DynaGraft is tested for osteoinductive potential using an in vitro myoblast differentiation assay. DBM osteoinductivity varied markedly with tissue bank source such that the percentage of lots rejected per tissue bank varied from 2% to more than 30%. The in vitro osteoinductivity assay responds to a BMP positive control in a dose-responsive fashion. The C2C12 cells do not differentiate in the presence of TGFβ1 or deactivated DBM. The in vitro assay also permits rapid and large-scale screening for the osteoinductive potential of novel biomaterials. Implants of commercial DynaGraft Granules (DBM only), Matrix, Gel and Putty products demonstrate in vivo osteoinductive potential when tested in a xenogeneic mouse heterotopic model. This corroborates the in vitro osteoinductivity of human DBM tested in a mouse C2C12 skeletal muscle cell line and further validates the in vitro assay.

ABSTRACT

To solve some of the problems inherent in bone regeneration, various types of graft materials, matrix, putty, and gel delivery systems have been developed. These deliver demineralized bone matrix (DBM) to a graft site and maintain it in an appropriate position to achieve favorable results. This prospective study reviewed 10 cases of extraction immediate grafting with a putty—DBM delivery system. Five patients were male and 5 female. At intervals ranging from 4 to 21 months postextraction grafting, bone cores were harvested at the time of surgical insertion of Replace endosteal two–stage implants. All patients were restored with single-tooth self–standing prostheses. Bone quality and quantity in each of the bone cores were evaluated. All 10 cases were completed with favorable outcomes.

ABSTRACT

Samples of demineralized bone matrix (DBM) were exposed to graduated doses of radiation (1—15 Megarad) (Mrad) utilizing a linear accelerator and then implanted into the thoracic region of Long-Evans rats. Subcutaneous implantation of DBM into allogenic rats induces endochondral bone. In response to matrix implantation, a cascade of events ensues; mesenchymal cell proliferation on day 3 postimplantation, chondrogenesis on day 7, calcification of the cartilagenous matrix and chondrolysis on day 9, and osteogenesis on day 11 resulting in formation of an ossicle containing active hemopoietic tissue. Bone formation was assessed by measuring alkaline phosphatase activity, the rate of mineralization was determined by measuring ⁴⁵Ca incorporation to bone mineral, and ⁴⁰Ca content measured the extent of mineralization; acid phosphatase activity was used as a parameter for bone resorption. The dose of radiation (2.5 Mrad) currently used by bone banks for sterilization of bone tissue did not destroy the bone induction properties of DBM. Furthermore, radiation of 3—5 Mrad even enhanced bone induction, insofar as it produced more bone at the same interval of time than was obtained from unirradiated control samples. Nonc of the radiation doses used in these experiments abolished bone induction, although the response induced by matrix irradiated with doses higher than 5 Mrad was delayed.

ABSTRACT

The efficacies of two different allografts, Grafton (demineralized bone matrix [DBM] in a glycerol carrier) and OrthoBlast (DBM in a reverse thermal poloxamer carrier) were examined from cases involving periarticular fractures. Demographic, perioperative, and outcome data for patients with periarticular fractures who underwent a prospectively designed protocol for bone grafting were compiled, with 15 cases using OrthoBlast and 13 using Grafton. A successful graft was defined as healing on the first graft attempt without complications. Healing was determined by radiographic studies and clinical evaluation. The successful graft rates of OrthoBlast and Grafton were 15/15 and 9/13 respectively.

ABSTRACT

Sixty-three patients who underwent complex ankle or hindfoot fusion had demineralized bone matrix placed in their fusion site to stimulate fusion. Thirty-seven patients had Grafton putty, a demineralized bone matrix product, and 26 patients had OrthoBlast, a demineralized bone matrix mixed with crushed cancellous allograft bone placed to stimulate their fusion site. All patients were followed clinically and radiographically to fusion or nonunion. Of the 37 patients who had Grafton putty placed to stimulate ankle or hindfoot fusion, five (14%) developed a nonunion. Of the 26 patients who had OrthoBlast placed to stimulate fusion, two (8%) developed a nonunion. These differences were not statistically significant. Nonunion rates of approximately 10% continue to be reported for ankle and hindfoot fusion procedures. In an attempt to minimize this complication, various bone graft substitutes have been used. We found no difference in efficacy of the two demineralized bone matrix compounds, and were not able to demonstrate a superior union rate compared to historical controls.

ABSTRACT

Smoking impairs bone healing and increases the risk for complications associated with nonunions. The efficacies of 2 different allografts, Grafton (demineralized bone matrix [DBM] in a gel-like glycerol carrier) and OrthoBlast (DBM with a reverse thermal poloxamer carrier) were examined with respect to nonunions in patients who reported heavy tobacco use. The Grafton allograft was used in 25 patients, and the OrthoBlast allograft was used in 13 patients. All patients smoked more than half a pack of cigarettes a day and did not use electric stimulators. A successful graft was defined as healing on the first graft attempt without complications or later regraft. The Grafton and OrthoBlast success rates were 52% and 85%, respectively (P = .077). The unique thermal properties of the OrthoBlast reverse poloxamer, which may enhance DBM osteoinduction, may account for the difference in success rates. Although results failed to reach statistical significance, the large difference and high likelihood ratio (4.2) between the 2 groups suggest that perhaps not all commercially available allografts may necessarily perform with the same efficacy with respect to heavy smokers.

ABSTRACT

Closure of bone defects that do not heal spontaneously require some form of bone inducing agent in order to ensure complete repair. Autogenous bone is the clinical gold standard for the management of these types of defects. Literature supports the concept that demineralized bone matrix (DBM) is osteoinductive. It was the purpose of this investigation to determine whether DBM delivered in a putty format (delivered by Poloxamer 407) would heal critically sized calvarial defects in skeletally mature New Zealand White rabbits. Twenty rabbits were divided into two groups each having bilateral oval 15mm defects created in their parietal bones. The first group of animals had untreated defects compared to those filled with Plaster of Paris whereas the second group compared DBM Putty to the excipient (Poloxamer 407) used to deliver DBM as a putty. Animals were sacrificed at 6 and 12 weeks and evaluated both histomorphometrically and radiographically using previously published methods. Significant differences in bone fill were found (p<0.001, ANOVA) at both time points between defects reconstructed with DBM putty and all other groups that were evaluated. These results provide evidence that DBM putty is osteoinductive and may be clinically useful for the management of critically sized cranial vault defects.

ABSTRACT

Demineralized allogenic bone matrices (DABM) and demineralized freeze-dried bone allograft (DFDBA) have been successfully used as bone-graft materials in the treatment of acquired and congenital cranio-maxillofacial defects and in some orthopedic surgery. However, these bone–graft “powders” have many shortcomings. For example, placement of particulate graft material in a hemorrhaging site can result in inadequacies or inaccurate attachment as well as loss of the graft materials. To minimize the inadequacies of powderlike graft materials, xenogenic collagen isolated from human tendon, skin, or bone was added to the bone-graft particles to form a composite spongelike implant. This material is commercially available and consists of 60% collagen and 40% DFDBA (DynaGraft^TM, GenSci Co., Irvine, CA). The goal of this study was to evaluate the characteristics of composite graft implants in the mineralization process in an animal model in comparison with DFDBA powder and pure collagen. Seventy-two Swiss Webster mice were divided into three groups: an experimental group implanted with DynaGraft, two comparison groups implanted with either DFDBA or collagen only. All the graft materials were surgically implanted and inserted into the left thigh muscle. Mice were humanely killed at 1, 2, 3, 4, 6, 8, and 12 weeks. Then the muscle tissues in the vicinity of the implants were excised and processed for histology. Paraffin sections were stained with hematoxylin and eosin (H&E), the Von Kossa method, and Masson’s trichrome. Some selected specimens were processed for transmission electron microscopic observation. After 1 week of Implantation, the DynaGraft™ group showed calcium deposition on the collagen material and on the periphery of the DFDBA particles. Increased calcification and bone-forming cells were observed at 4–6 weeks. After 8 weeks, the implant formed a calcified nodule and only heavily mineralized connective tissue was observed at the implanted site. The group implanted with DFDBA powder showed calcification around the particulates. The collagen–sponge control group revealed no calcification or bone formation during the period of implantation. The light microscopic findings were confirmed by electron microscopy. Quantitative radiographic density DynaGraft and DFDBA graft followed sequentially over a period 120 days. It was concluded that a higher rate of calcification and bone formation was produced in the composite graft implant compared to the DFDBA implant. The composite graft material (DynaGraft) which contains both collagen and DFDBA, proved to be more effective for bone formation than particle components alone.