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PubMed1999

alpha-BSM: a biomimetic bone substitute and drug delivery vehicle.

alpha-BSM is a biomimetic endothermically setting apatitic calcium phosphate bone substitute material. Its injectability and ability to harden at body temperature in the presence of physiologic saline, and other buffering agents, makes it an attractive clinical bone substitute and delivery vehicle for therapeutic agents in orthopaedic and dental applications. In osseous tissue, alpha-BSM alone remodels into bone and promotes bone healing. alpha-BSM treatment has been shown in several animal models to be effective in promoting healing of surgically created critical size defects and restoring bone biomechanical strength to values equal to or greater than values achieved with autograft controls. In vitro studies with alpha-BSM containing gentamicin show that antibiotics can be incorporated stably into alpha-BSM and that the release kinetics can be controlled with the appropriate formulation and preparative procedures. Growth factors and enzymes also are compatible with the alpha-BSM setting reaction. The incorporation of recombinant human bone morphogenetic protein-2 with alpha-BSM was shown to be effective in stimulating bone formation and accelerating restoration of the differentiated phenotype in an osteotomy model. Clinical trial investigators in Europe currently are using alpha-BSM implantations for treatment of fractures and other indications.

Animals↗
PubMed2004

Evaluation of a resorbable, in situ setting bone substitute in a sheep model.

The gold standard for bone substitution is the autologous bone graft, but because of its limited supply and the associated morbidity, the search for synthetic alternatives is necessary. A new in situ setting tricalcium phosphate cement was implanted in a trepanation defect (9.4 mm diameter, 10 mm depth) in the distal femoral epiphysis of sheep. Empty cavities and autologous bone graft were used as controls. Histologic and histomorphometric examinations were carried out after 12 weeks. Nearly 90% of the implanted cement was resorbed and replaced by ingrown bone with close contact between surrounding bone, new bone, and remaining cement particles. The amount of bone in the defect area was significantly higher in defects filled with cement relative to defects filled with autologous bone graft (mean 27 vs. 21%, 95% confidence intervals 23 to 31 and 18 to 23, p = 0.026). In conclusion, this new in situ setting cement is bioactive, resorbable, and osteoconductive. It will be useful as an alternative to autologous bone graft to fill stable defects.

Animals↗
PubMed2004

[Fractures of the distal radius treated by osteosynthesis and injectable bone substitute: a prospective study of 39 patients].

PURPOSE OF THE STUDY: Comminution is often neglected in patients presenting fractures of the distal radius. Use of injectable bone substitutes can fill the gap left by comminution, avoiding radial shortening and loss of prono-supination. MATERIAL AND METHODS: Forty-eight patients with a distal fracture of the radius were treated by osteosynthesis and injectable cement between 1998 and 2001. These patients were reviewed at mean follow-up of 46 months (36-56). Dorsal displacement was present in all cases and the AO classification was A (n=26), B (n=15), C (n=7). Fixation was achieved with pins (n=32), posterior plate (n=14), and external fixator (n=2) before injection of the bone substitute. Outcome was evaluated with the Herzberg score, the Gartland and Werley score and DASH by an independent operator. RESULTS: Four patients were lost to follow-up and five who developed a deformed callus after the initial osteosynthesis were excluded from the analysis. The Herzberg functional score reached 84 (range 54-100) and the Gartland and Werley radioclinical score was 4.6 (0-11) with 89% excellent and good outcomes. DASH was 23.6 (5.8-62.7). Ulnar variance was unchanged or changed less than 2 mm between the immediate postoperative period and last follow-up in 88% of patients. There was one carpal tunnel syndrome related to anterior cement leakage. Three biopsies were performed and revealed a "humid sand" aspect six months after injection as well as presence of osteoblasts within the bone substitute. There was no or very little resorption. DISCUSSION: Several authors have demonstrated the biomechanical and functional effects of filling the comminution gap to avoid radial shortening. The first reported cases, then later prospective series, favored the use of injectable cements for patients with comminution. Cement used in our patients allowed preservation enables preservation of normal ulnar variance in addition to filling the gap. Like any bone substitute, it is an attractive alternative to other filling methods (ceramic graft) offering two advantages: adaptation to the bone defect and primary stability. This easy-to-use cement is resorbed slowly. Because of high cost, it may be reserved for patients with important functional needs.

Adult↗
PubMed2000

[Bone substitutes].

The application of autogenous bone transplants is still the gold standard for all reconstructive surgery. The wish of surgeons for alternatives to autogenous bone grafts is reflected in the development of a variety of bone graft substitutes of synthetic or biological origin. The following review article is meant to provide the reader with a critical overview of all the alternative materials. In addition, we want to point to the tremendous progress made on this subject, made possible by the joint effort of surgeons and basic researchers. The results of this collaboration show that in the near future a new gold standard for successful reconstructive surgery will emerge and replace the use of autogenous bone transplants.

Animals↗
PubMed1994

Sintered porous DP-bioactive glass and hydroxyapatite as bone substitute.

There is extensive experimental and surgical experience with the use of bone tissue to fill defects in the skeleton, to bridge non-union sites, and to pack defects in bone created from cyst curettage. DP-bioactive glass with a chemical composition of Na2O 8.4%, SiO2 39.6%, P2O5 12% and CaO 40% has been reported as an alternative bone substitute of high mechanical strength, good biocompatibility. and which has a tight bond with living tissue. The bonding layer between DP-bioactive glass and bone tissue was considered to be formed by dissolution of calcium and phosphate ions from the DP-bioactive glass into the surrounding body fluids. The biological hydroxyapatite was suspected to deposit directly onto the bonding layer. In order to confirm the interaction between the DP-bioactive glass and bone tissue, the developed bioactive glass was implanted into rabbit femur condyle for 2-32 weeks. The histological evaluation of DP-bioactive glass as a bone substitute was also investigated in the study. Porous hydroxyapatite bioceramic was used in the control group and the results were compared with those of DP-bioactive glass. The interface between the DP-bioactive glass and bone tissue examined with SEM-EPMA showed that the bioactive glass formed a reaction layer on the surface within 2 weeks after operation and formed a direct bond with natural bone. The elements contained in the bioactive glass apparently interdiffuse with the living bone and biological hydroxyapatite deposited onto the diffusion area, which was proved by EPMA and TEM. After implantation for over 8 weeks, the DP-bioactive glass was gradually biodegraded and absorbed by the living bone. Histological examination using the optical microscope showed that osteocytes grow into the inside of the DP-bioactive glass and the bioactive glass would be expected to be a part of bone.

Animals↗
PubMed2002

Crystallization at the polymer/calcium-phosphate interface in a sterilized injectable bone substitute IBS.

Calcium phosphate (CaP) ceramics are the main raw materials used to elaborate blocks or granules for bone substitutes. In this study, injectable bone substitutes (IBS) were developed for applications in orthopedic or dental surgery. Sterile, ready-to-use composite containing CaP granules (biphasic calcium phosphate, BCP) and polymer (hydroxypropylmethylcellulose, HPMC) was prepared. Steam sterilization produced new phenomena at the CaP/polymer interface, resulting in crystal growth. These phenomena may constitute a model for the biomineralization study. Scanning electron microscopy showed that the formed crystallites organize themselves into a three-dimensional structure. Currently, the mechanisms of crystal growth are unknown and have been observed with only one combination of polymer/BCP ceramics after steam sterilization.

Biocompatible Materials↗
PubMed2004

[The effect of platelet-rich plasma on new bone formation by augmentation with osseoconductive bone substitute material in beagle dogs].

Animal experiments were carried out with osseoconductive bone substitute beta-tricalcium phosphate (beta-TCP), with the aim of assessing the effect of the growth factors synthesized by platelets on the speed of beta-TCP incorporation and on the quality of newly formed bone. The question arises whether the results attained with this synthetic material approach are comparable to those attained with autologous bone. Defects in the mandibles of beagle dogs were filled with beta-TCP or with the mixture of beta-TCP and platelet rich plasma (PRP) obtained from autologous blood. The quality of the newly formed bone and the effect of PRP were studied by histologic and histomorphometric methods. On the 6th week, bone formation seemed to be more effective when PRP was applied in comparison with beta-TCP alone, but the difference was not significant. On the 12th week bone formation was significantly greater. The results demonstrate that the use of PRP accelerates the remodelling of the synthetic bone-substitute material beta-TCP.

Animals↗
PubMed2006

Multidetector-CT evaluation of bone substitutes remodeling after revision hip surgery.

UNLABELLED: We evaluated remodeling of grafted bone substitutes after revision hip arthroplasty using serial examinations of multidetector-row computed tomography imaging. Ten patients (12 hips) had cementless revision surgery with grafting of beta-tricalcium phosphate granules and pastelike calcium phosphate cement in bone defects around the femoral component. At 3 weeks and 1 year postoperatively, the patients were evaluated using multidetector-row computed tomography imaging with a metal artifact minimizing protocol. New bone formation and changes in volume of beta-tricalcium phosphate and calcium phosphate cement were measured. At 1 year postoperatively, beta-tricalcium phosphate had decreased more than calcium phosphate cement. The residual volumes of calcium phosphate cement and beta-tricalcium phosphate were 78% (range, 37%-96%) and 30% (range, 10%-62%) of the initial grafted volume, respectively. The volume of the new bone that formed after absorption of beta- tricalcium phosphate was 34% (range, 11%-76%) of the initial beta-tricalcium phosphate volume. Use of cement in prior operations was an unfavorable factor in graft remodeling after revision surgery. Multidetector-row computed tomography is a promising tool for evaluating bone stock restoration of patients and influential factors of bone remodeling, and for clarifying remodeling patterns of various bone substitutes. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Aged↗
PubMed1999

Kinetic study of bone ingrowth and ceramic resorption associated with the implantation of different injectable calcium-phosphate bone substitutes.

This study investigated the in vivo performance of two composite injectable bone substitutes (IBS), each with different calcium-phosphate particles granulometries [40-80 (IBS 40-80) and 200-500 microm (IBS 200-500)]. These biomaterials were obtained by associating a biphasic calcium-phosphate (BCP) ceramic mineral phase with a 3% aqueous solution of a cellulosic polymer (hydroxy-propyl-methyl-cellulose). Both materials were injected for periods of 2, 3, 8, or 12 weeks into bone defects at the distal end of rabbit femurs. Quantitative results on new bone formation, BCP resorption, and staining for tartrate-resistant acid phosphatase (TRAP) activity were studied for statistical purposes. Measurements with scanning electron microscopy and image analysis showed that the final rates of newly formed bone were similar for both tested IBS after 12 weeks of implantation. Bone colonization occurred more extensively during early implantation times for IBS 40-80 than for IBS 200-500. For the latter, BCP degradation occurred regularly throughout the implantation period, whereas it was very intensive during the first 2 weeks for IBS 40-80. Positive TRAP-stained degradation cells were significantly more numerous for IBS 40-80 than for IBS 200-500 regardless of implantation time. With the granulometry of either mineral phase, both tested IBS supported extensive bone colonization, which was greater than that previously reported for an equivalent block of macroporous BCP. The resorption-bone substitution process seemed to occur earlier and faster for IBS 40-80 than for IBS 200-500. Both tested IBS expressed similar biological efficiency, with conserved in vivo bioactivity and bone-filling ability.

Animals↗
PubMed2006

Biodegradable and semi-biodegradable composite hydrogels as bone substitutes: morphology and mechanical characterization.

Biodegradable and semi-biodegradable composite hydrogels are proposed as bone substitutes. They consist of an hydrophilic biodegradable polymer (HYAFF 11) as matrix and two ceramic powders (alpha-TCP and HA) as reinforcement. Both components of these composites have been of great interest in biomedical applications due to their excellent biocompatibility and tissue interactions, however they have never been investigated as bone substitute composites. Morphological and mechanical analysis have shown that the two fillers behave in a very different way. In the HYAFF 11/alpha-TCP composite, alpha-TCP is able to hydrolyze in contact with water while in the HYAFF 11 matrix. As a result, the composite sets and hardens, and entangled CDHA crystals are formed in the hydrogel phase and increases in the mechanical properties are obtained. In the HYAFF11/HA composite the ceramic reinforcement acts as inert phase leading to lower mechanical properties. Both mechanical properties and microstructure analysis have demonstrated the possibility to design hydrophilic biodegradable composite structures for bone tissue substitution applications.

Biocompatible Materials↗
PubMed1999

Current use of bone substitutes in maxillofacial surgery.

The use of bone substitutes in the field of facial plastic and reconstructive surgery is well established. Because of the complexity of the anatomy in the head and neck region, reconstruction and augmentation of this area pose a challenge to the surgeon. In addition, the shortcomings of autogenous bone, such as resorption and donor site morbidity, have led to the need for alloplastic implants in the field of facial plastic surgery. Multiple alloplastic implants are currently in use today; however, those compounds that contain calcium, silicon, and carbon have been examined more closely in this article. This is because of their ability to osseointegrate and osseoconduct with surrounding fibro-osseous tissue, as well as demonstrate a higher immunogenic tolerance by the human body. The discussion of each compound includes a description of its composition and structure, the advantages and shortcomings of the material, and its current uses in the field of facial plastic and reconstructive surgery. With a better understanding of the available alloplastic implants, the surgeon can make a more informed decision as to which implant would be most suitable in a particular patient.

Bone Morphogenetic Protein 3↗
PubMed2003

Bone substitutes in 2003: an overview.

The authors review the various bone substitutes which are currently available on the market place in Belgium. After describing the requirements for clinical use of such materials, they compare the biological and mechanical values of bone autografts, bone allografts, demineralised bone, xenografts, coral and synthetic materials such as calcium sulfate, calcium phosphate, ionic cement and bioactive glass. They stress the current paucity of data pertaining to the biological value of these materials and call for in vivo validation tests. They also review biomolecules such as BMP-2 or OP-1, whose osteoinductive properties are currently under investigation. Finally, they present the emergent field of cell therapy, in which osteoprogenitor cells are isolated from the patient's bone marrow and reinjected after in vitro cultivation. They stress the therapeutic and medicolegal problems raised by the combination of medical devices, grafts, medicinal products and cells, all of which have a different status within the complex European legal framework.

Animals↗
PubMed2005

Small-animal models for testing macroporous ceramic bone substitutes.

The aim of this study was to compare the bone colonization of a macroporous biphasic calcium phosphate (MBCP) ceramic in different sites (femur, tibia, and calvaria) in two animal species (rats and rabbits). A critical size defect model was used in all cases with implantation for 21 days. Bone colonization in the empty and MBCP-filled defects was measured with the use of backscattered electron microscopy (BSEM). In the empty cavities, bone healing remained on the edges, and did not bridge the critical size defects. Bone growth was observed in all the implantation sites in rats (approximately 13.6-36.6% of the total defect area, with ceramic ranging from 46.1 to 51.9%). The bone colonization appeared statistically higher in the femur of rabbits (48.5%) than in the tibia (12.6%) and calvaria (22.9%) sites. This slightly higher degree of bone healing was related to differences in the bone architecture of the implantation sites. Concerning the comparison between animal species, bone colonization appeared greater in rabbits than in rats for the femoral site (48.5% vs. 29.6%). For the other two sites (the tibia and calvaria), there was no statistically significant difference. The increased bone ingrowth observed in rabbit femurs might be due to the large bone surface area in contact with the MBCP ceramics. The femoral epiphysis of rabbits is therefore a favorable model for testing the bone-bonding capacity of materials, but a comparison with other implantation sites is subject to bias. This study shows that well-conducted and fully validated models with the use of small animals are essential in the development of new bone substitutes.

Animals↗
PubMed1998

Human growth hormone locally released in bone sites by calcium-phosphate biomaterial stimulates ceramic bone substitution without systemic effects: a rabbit study.

Calcium-phosphate bone replacement biomaterial has been used as a drug carrier for therapeutic agents. This study investigated the efficacy of local administration of human growth hormone (hGH) by macroporous biphasic calcium phosphate (MBCP) implants in improving the bone substitution qualities of ceramics. hGH release from MBCP implants loaded with 1 microg of hGH was rapid during the first 48 h and then sustained for a total of 9 days. Immunolocalization of hGH in vitro and in vivo by transmission electron microscopy showed its presence inside the material, indicating that it was able to penetrate within the porosity of the ceramic during the adsorption process. MBCP cylinders (6 x 6 mm) were loaded with 0.1, 1, and 10 microg of hGH and implanted into rabbit femurs (n = 40). The effects of locally released hGH on bone ingrowth and ceramic resorption were evaluated by scanning electron microscopy and image analysis. The results indicated that hGH increased bone ingrowth (+65%) and ceramic resorption (+140%) significantly in comparison with control implants and that the increase was dose dependent. Biochemical parameters monitored in rabbit plasma and urine, as well as the absence of any significant difference between contralateral implants and the control, indicated that hGH did not produce detectable systemic effects. Thus, the use of MBCP appears to be effective for local delivery of hGH, resulting in improved bone substitution.

Animals↗
PubMed2006

Injectable bone substitute to preserve alveolar ridge resorption after tooth extraction: a study in dog.

The aim of the present study was to assess the efficacy of a ready-to-use injectable bone substitute on the prevention of alveolar ridge resorption after tooth extraction. Maxillary and mandibular premolars were extracted from 3 Beagle dogs with preservation of alveolar bone. Thereafter, distal sockets were filled with an injectable bone substitute (IBS), obtained by combining a polymer solution and granules of a biphasic calcium phosphate (BCP) ceramic. As a control, the mesial sockets were left unfilled. After a 3 months healing period, specimens were removed and prepared for histomorphometric evaluation with image analysis. Histomorphometric study allowed to measure the mean and the maximal heights of alveolar crest modifications. Results always showed an alveolar bone resorption in unfilled sockets. Resorption in filled maxillary sites was significantly lower than in control sites. Interestingly, an alveolar ridge augmentation was measured in mandibular filled sockets including 30% of newly-formed bone. It was concluded that an injectable bone substitute composed of a polymeric carrier and calcium phosphate can significantly increase alveolar ridge preservation after tooth extraction.

Alveolar Process↗
PubMedDate not supplied

Use of a new malleable implant as a bone substitute in maxillofacial surgery.

Biocompatible osteoconductive polymer (BOP) has been used since 1979 as a substitute for bone in orthopedic surgery and neurosurgery. To date, in maxillofacial surgery, loss of bone volume as a result of either trauma or osteoporosis has been compensated for by autologous bone onlay graft or subperiosteal apposition grafts of synthetic materials. Neither of these solutions is entirely satisfactory. Autologous bone is subject to reabsorption, requiring initial overcorrection and multiple reoperations to achieve an acceptable result. Preshaped implants of Proplast, Vicryl, Gore-Tex, or silicone do not offer much flexibility, and coral granules and hydroxyapatite are difficult to handle. Finally, all foreign materials can elicit problems with tolerability. In its SP (solution/powder) form, BOP is a paste that can be molded precisely to the required shape, making it ideal for maxillofacial surgery. This study examined the long-term tolerability and facial alterations after implants of BOP in 11 patients who underwent post-trauma and cosmetic surgery.

Adult↗
PubMedDate not supplied

Assessment of stiffness and strength of 4 different implants available for equine fracture treatment: a study on a 20 degrees oblique long-bone fracture model using a bone substitute.

OBJECTIVE: To compare the mechanical properties of 4 stabilization methods for equine long-bone fractures: dynamic compression plate (DCP), limited contact-DCPlate (LC-DCP), locking compression plate (LCP), and the clamp-rod internal fixator (CRIF--formerly VetFix). STUDY DESIGN: In vitro mechanical study. SAMPLE POPULATION: Bone substitute material (24 tubes) was cut at 20 degrees to the long axis of the tube to simulate an oblique mid-shaft fracture. METHODS: Tubes were divided into 4 groups (n=6) and double plated in an orthogonal configuration, with 1 screw of 1 implant being inserted in lag fashion through the "fracture". Thus, the groups were: (1) 2 DCP implants (4.5, broad, 10 holes); (2) 2 LC-DCP implants (5.5, broad, 10 holes); (3) 2 LCP implants (4.5/5.0, broad, 10 holes) and 4 head locking screws/plate; and (4) 2 CRIF (4.5/5.0) and 10 clamps in alternating position left and right of the rod. All constructs were tested in 4-point bending with a quasi-static load until failure. The implant with the interfragmentary screw was always positioned on the tension side of the construct. Force, displacement, and angular displacement at the "fracture" line were determined. Construct stiffness under low and high loads, yield strength, ultimate strength, and maximum angular displacement were determined. RESULTS: None of the implants failed; the strength of the bone substitute was the limiting factor. At low loads, no differences in stiffness were found among groups, but LCP constructs were stiffer than other constructs under high loads (P=.004). Ultimate strength was lowest in the LCP group (P=.01), whereas yield strength was highest for LCP constructs (409 N m, P=.004). CRIF had the lowest yield strength (117 N m, P=.004); no differences in yield strength (250 N m) were found between DCP and LC-DCP constructs. Differences were found for maximum angular displacement at the "fracture" line, between groups: LPC<DCP<LC-DCP<CRIF (P< or =.037). CONCLUSIONS: DCP, LC-DCP, and LCP constructs provided sufficient biomechanical stability to withstand single-cycle loads that might be experienced postoperatively. LCP constructs showed the best performance because of the highest yield strength, above which irreversible deformation occurred. Inadequate biomechanical properties, excessive motion, and shape of the device create concern about the use of CRIF in these large sizes. CLINICAL RELEVANCE: CRIF does not meet the demands for equine long-bone fracture treatment. With respect to biomechanical properties, DCP, LC-DCP, and LCP constructs did not show critical differences so other factors may direct clinical selection of these implants. We prefer the LCP implants because of the high yield strength, high stiffness under high-load application, and the least movement at the fracture line.

Animals↗