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PubMed2001

Open wedge tibial osteotomy with acrylic bone cement as bone substitute.

We studied the results of 245 valgus producing high tibial osteotomies performed with the use of an opening wedge technique and rigid internal fixation followed by early passive and active motion of the knee. Previous studies have used iliac bone grafts or hemicollastasis held by an external fixator for opening the osteotomy. In our series the opening was obtained by a block of cement interposed in the postero-medial part of the osteotomy. This series confirms that the opening wedge osteotomy allows good accuracy for the correction. Ninety-three percent of the knees had a correction adjusted between 180 and 187 degrees for the hip-knee-ankle angle. Survivorship analysis showed an expected rate of survival, with conversion to a total knee on the end point, of 94% at 5 years, 85% at 10 years and 68% at 15 years. Conversion to a total knee arthroplasty was accomplished without difficulty in the patients who had this procedure done. We recommend opening wedge tibial osteotomy with acrylic cement bone cement as bone substitute, rigid internal fixation, and early motion for patients who undergo high tibial osteotomy.

Adult↗
PubMed2000

Crystal polymer interaction with new injectable bone substitute; SEM and Hr TEM study.

A composite constituted of calcium phosphate (CaP) granules and a hydrophilic polymer as a carrier (hydroxy-propyl-methyl cellulose, HPMC) was developed to be an injectable bone substitute (IBS, CNRS patent). IBS is a composite and not an ionic cement. The composite obtained is ready to use and sterile. Chemical interactions between organic and inorganic components appeared during the association of the two. The interactions of the CaP and the polymer have been studied using scanning electron microscopy (SEM), electron microprobe (EDX), and high-resolution transmission electron microscopy (HrTEM) SEM revealed a degradation of the granules into smaller particles while EDX was unable to show significant changes in the Ca/P ratio during aging of the composite. With Hr TEM, however, we observed hydrolysis (process of dissolution and precipitation) from the surface to about 13 nm into the HA crystals and occasional dissolution with precipitation of beta-TCP crystals. In HA, the first zone of interaction consisted of a single layer of small globular crystals of 2 to 3 nm in diameter. Numerous lattice patterns in all three axes could be observed. Under the globular crystals zone, the inter-reticular distances of the single crystals appeared enlarged by 1.2% (from 0.817 to 0.827 nm). The enlargement seems to correspond to diffusion of HPO(4) into the crystal lattice. In beta-TCP crystals, dissolution was observed to be several nanometers deep, but globular surface precipitation rarely was observed. With time or after steam sterilization, no changes were observed. These data demonstrate the strong interactions of the hydrophylic polymer with calcium phosphate, but only in the first several nanometers of thickness.

Bone Substitutes↗
PubMed2005

In vivo evaluation of a porous hydroxyapatite/poly-DL-lactide composite for use as a bone substitute.

We investigated the biocompatibility, osteoconductivity, and biodegradability of a porous composite of hydroxyapatite (HA) and poly-DL-lactide (PDLLA) implanted into rabbit femoral condyles and compared it with porous HA. Six weeks after implantation, the HA/PDLLA was covered with bone and contacted the bone directly. The amount of newly formed bone in the pores was similar in both materials during the examined period. The newly formed bone in the HA/PDLLA tended to increase over 26 weeks, but that in the HA did not show a significant increase after 12 weeks. By 26 weeks, remodeling of the newly formed bone in the pores was seen and bone marrow tissue was found in the pores of the HA/PDLLA. The porous HA/PDLLA was resorbed much faster than the porous HA. Porous HA/PDLLA was resorbed continuously through bone formation and remodeling. Conversely, porous HA was scarcely resorbed throughout the period. HA/PDLLA is thought to be degraded almost completely after about 1 year, and in this study, porous HA/PDLLA showed excellent osteoconductivity and faster resorption than HA. Therefore, HA/PDLLA might be a desirable material for bone substitutes.

Animals↗
PubMed2005

Dorsal plating of unstable distal radius fractures using a bio-absorbable plating system and bone substitute.

This study reports the results of open reduction and internal fixation of 26 unstable, intraarticular, dorsally displaced fractures of the distal radius using a bio-absorbable dorsal distal radius (Reunite) plate and calcium phosphate (Biobon) bone substitute. The bio-absorbable plate has the advantage of being low profile, easily contourable and angularly stable. In the majority of cases, this plate produces functional results comparable with metal plates. The Gartland and Werley score was excellent or good in 21 patients. The theoretical advantage over metal plates is in eliminating the need to remove the plate and hence the need for a second operation if implant-related extensor tenosynovitis occurs. Inflammatory tissue reaction to the degradation products of the plate is a potential concern, although the co-polymer ratio used in this plate appears to have reduced the severity of this reaction, which was seen in two patients in this series. The reduction was lost in five patients with severe dorsal comminution. Following this experience, we do not recommend this plating system for fractures with a metaphyseal gap of greater than 7 mm following reduction.

Absorbable Implants↗
PubMed1995

Anterior cranial base reconstruction using a hydroxyapatite-tricalciumphosphate composite (Ceratite) as a bone substitute.

The craniofacial approach to cranial base tumors has widened the operability of tumors with intracranial invasion. However, the resulting skull base defect must be reconstructed adequately to prevent postoperative morbidity and mortality. We use hydroxyapatite-tricalciumphosphate ceramic (Ceratite) as a bone substitute material to reconstruct the skull base defect in combination with the pericranial flap, ensuring separation between the sinonasal cavity and epidural cavity. Although the nasal surface of the Ceratite block is left exposed directly to the sinonasal cavity, it was shown to be epithelialized within 6 months postoperatively. Our method is less invasive than any other conventional method and may offer more chance of curative resection of tumors with anterior skull base invasion.

Adenocarcinoma↗
PubMed2001

A model to evaluate bone substitutes for immediate implant placement.

A calcified alloplast was evaluated as a gap-filling material around implants placed immediately into fresh extraction sockets. Periodontal measurements and computed tomography scans were obtained to evaluate the clinical effectiveness of the alloplast when compared with demineralized freeze-dried bone. To determine whether this alloplast would be a suitable grafting material, 14 patients were selected to evaluate the extraction socket as a model for routine histologic confirmation of the efficacy and biocompatibility of bone substitutes. The results of this study showed the following: (1) human extraction sockets can be models for the study of bone/implant interaction; (2) the alloplast was well tolerated and demonstrated no inflammation through histologic evaluation of core biopsies; (3) the alloplast was a suitable material when used as a gap-filling graft in sockets around immediately placed implants; and (4) dental computed tomography scans and periodontal measurements around grafted implants 6 months after the procedure provide valuable clinical information about graft healing and osteointegration.

Alveolar Bone Loss↗
PubMed1998

Coating of hydroxyapatite on highly porous Al2O3 substrate for bone substitutes.

A thin film of hydroxyapatite (HA) was successfully coated onto a highly porous substrate of alumina by using a novel solution technique. The coated HA bonded strongly to the substrate through a glass sintering aid with an intermediate thermal expansion coefficient. The coating was also found to be microstructurally and chemically uniform on the surfaces of the interconnected pores in the matrix of the substrate. Mechanical property testing results showed that the strength of the HA-coated composite was significantly improved, indicating a high potential for structural bone substitutes in hard tissue prosthetics.

Aluminum Oxide↗
PubMed1980

A convenient animal model for testing bone substitute materials.

There is consijerable interest in developing substitute materials for bone to perform the functions of autogenous bone grafts. However, a persistent problem is finding a suitable animal model in which to test the biodegradable implants. This paper reviews the requirements of an ideal animal model for this purpose and discusses the shortcomings of existing procedures. A technique is described that uses the cranial vault of the rabbit and allows accurate radiologic and histologic assessment of implant resorption and ingrowth of new bone.

Animals↗
PubMed1995

The effects of ultrasonic stimulation on DP-bioglass bone substitute.

In previous studies, DP-bioglass showed good biocompatibility and can form a chemical bond with natural bone. After implementation in the rabbit femur condyle for 32 weeks, DP-bioglass gradually biodegraded and osteocytes grew into the material. In this study, an attempt has been made to utilize low intensity pulsed ultrasound to speed up the bone regeneration rate and DP-bioglass absorption rate when the DP-bioglass is implanted into the rabbit femur condyle as a bone substitute. The fundamental parameters of the ultrasound used were 1.5 MHz frequency, 0.5 W cm-2 intensity, on-off ratio 1:1 and 2 ms for the on-off time interval. The stimulation, in all cases, was started 24 h after the operations by applying the transducer to the skin using DIR ultrasound jelly as a coupling medium. The evaluation of the progress of bone regeneration and the material's biodegradable rate were conducted by histological examination and by measurements of the areas of regenerated bone, pores and DP-bioglass made with a planimeter. It was found that low intensity pulsed ultrasound had a profound effect on the rate both of bone regeneration and DP-bioglass bioabsorption in this rabbit model and that its mechanism of the action may be via an electromechanical kinetic effect on the cell membrane interfaces.

Animals↗
PubMed2004

Surface porous fibre-reinforced composite bulk bone substitute.

The aim of this study was to describe and evaluate the significance of a porous surface with bioactive glass granules (S53P4) covering an artificial bulk material based on polymethylmetacrylate (PMMA) and fibre-reinforced composite (FRC) technology. Effort was focused particularly on characters of the porous surface and biomechanical properties of the material in vitro , and test in vivo the implant in reconstruction in an experimental long bone segment defect model. The defect, 10 mm in length, created in the shaft of rabbit tibia, was reconstructed by the implant and fixed by intramedullary K-wires. The implant was incorporated within 4 weeks by new bone growth from the host bone covering particularly its posterior surface and cortex/implant junctions with bridging trabecular bone. Later, at 8 weeks, new bone was found also at the cortex/implant interface and in the medullary canal of the implant. Histometric measurements revealed direct bone/implant surface contact in 34% at the interface. Bioactive glass granules in the porous surface evoked the most direct contact with bone. The implants manufactured from PMMA only served as a control group, and showed significantly lower osteoconductive properties. Biomechanical measurements in vitro of fibre-reinforced PMMA specimens revealed values for bending strength and the flexural modulus to match them to human bone. This artificial bulk bone material based on PMMA/FRC technology seems to have proposing properties to be used as a bone substitute on load-bearing conditions.

Bone Substitutes↗
PubMed2004

Hydroxyapatite-chitin materials as potential tissue engineered bone substitutes.

Hydroxyapatite (HA) in 25%, 50% and 75% w/w fractions was incorporated into chitin solutions and processed into air- and freeze-dried materials. These HA-chitin materials were exposed to cell cultures and implanted into the intramusculature of a rat model. The HA-chitin materials were found to be non-cytotoxic and degraded in vivo. The presence of the HA filler enhanced calcification as well as accelerated degradation of the chitin matrix. The freeze-dried HA-chitin matrixes were selected for further cell seeding experiments because of their porous nature. Mesenchymal stem cells harvested from NZW rabbits were induced into osteoblasts in vitro using dexamethasone. These osteoblasts were cultured for 1 week, statically loaded onto the porous HA-chitin matrixes and implanted into bone defects of the rabbit femur for 2 months. Histology of explants showed bone regeneration with biodegradation of the HA-chitin matrix. Similarly, green fluorescence protein (GFP) transfected MSC-induced osteoblasts were also loaded onto porous HA-chitin matrixes and implanted into the rabbit femur. The results from GFP-transfected MSCs showed that loaded MSCs-induced osteoblasts did not only proliferate but also recruited surrounding tissue to grow in. This study demonstrates the potential of HA-chitin matrixes as a good substrate candidate for tissue engineered bone substitute.

Animals↗
PubMed2004

Bacterial biosynthesis of a calcium phosphate bone-substitute material.

A species of Serratia bacteria produces nano-crystalline hydroxyapatite (HA) crystals by use of a cell-bound phosphatase enzyme, located both periplasmically and within extracellular polymeric materials. The enzyme functions in resting cells by cleaving glycerol-2-phosphate (G-2-P) to liberate free phosphate ions which combine with calcium in solution to produce a cell-bound calcium phosphate material. Bacteria grown as a biofilm on polyurethane reticulated foam cubes were challenged with calcium and G-2-P in a bioreactor to produce a 3-D porous bone-substitute material. The scaffold has 1 mm macropores and 1 microm micropores. XRD showed the crystallites to be 25-28 nm in size, resembling HA before sintering and beta-tricalcium phosphate (beta-TCP, whitlockite) after. When biofilm was grown on titanium discs and challenged with calcium and G-2-P, a calcium phosphate layer formed on the discs. Biomineralisation is therefore a potential route to production of precursor nanophase HA, which has the potential to improve strength. The scaffold material produced by this method could be used as a bone-filler or as an alternative method for coating implants with a layer of HA.

Bone Substitutes↗
PubMed1994

Charcoal bamboo as a bone substitute: an animal study.

UNLABELLED: Charcoal bamboo (Bambusae glaucescens) was placed in the resected tibial diaphysis of sixteen New Zealand White rabbits. At two, four and six weeks and again at six months after the operations, four rabbits in each period were killed and all specimens were examined under a light microscope and a scanning electron microscope. The six-week specimens showed that there was neobone invasion into the pores of the charcoal bamboo. There was no evidence of fibroencapsulation or inflammatory response. Due to its structure as a uniform porous material with interconnecting pores and carbon composition, the charcoal bamboo has been proved to be an osteotropic material. CLINICAL RELEVANCE: Charcoal bamboo should be an alternative bone substitute which may be used in humans in the near future. This material is available and easy to produce and prepare in developing countries.

Animals↗
PubMed2001

Biologically and chemically optimized composites of carbonated apatite and polyglycolide as bone substitution materials.

We report on the development and characterization of a new composite material consisting of amorphous carbonated apatite, Ca(5)(PO(4), CO(3))(3)(OH), and microstructured poly(hydroxyacetic acid), polyglycolide (PGA). This material is able to keep the pH of a surrounding solution within the physiological range (7.2-7.6). This was achieved by chemical fine-tuning of the counterplay between the acidic degradation of the polyester and the basic dissolution of calcium phosphate. Microporous samples with pore sizes of <1 microm and compact samples were prepared. The biological behavior was assayed in vitro by long-term osteoblast culture. Morphological and biochemical analyses of cell differentiation revealed excellent biocompatibility, leading to cell attachment, collagen and osteocalcin expression, and mineral deposition. This material could be of use as a biodegradable bone substitution material and as a scaffold for tissue engineering.

Animals↗
PubMed2002

Development of calcium phosphate cement using chitosan and citric acid for bone substitute materials.

We developed a calcium phosphate cement that could be molded into any desired shape due to its chewing-gum-like consistency after mixing. The powder component of the cement consists of alpha-tricalcium phosphate and tetracalcium phosphate, which were made by decomposition of hydroxyapatite ceramic blocks. The liquid component consists of citric acid, chitosan and glucose solution. In this study, we used 20% citric acid (group 20) and 45% citric acid (group 45). The mechanical properties and biocompatibility of this new cement were investigated. The setting times of cements were 5.5 min, in group 20 and 6.4 min, in group 45. When incubated in physiological saline, the cements were transformed to hydroxyapatite at 3, and 6 weeks, the compressive strengths were 15.6 and 20.7 MPa, in group 45 and group 20, respectively. The inflammatory response around the cement implanted on the bone and in the subcutaneous tissue in rats was more prominent in group 45 than in group 20 at 1 week after surgery. After 4 weeks, the inflammation disappeared and the cement had bound to bone in both groups. These results indicate that this new calcium phosphate cement is a suitable bone substitute material and that the concentration of citric acid in the liquid component affects its mechanical properties and biocompatibility.

Animals↗
PubMed2001

Porous calcium polyphosphate scaffolds for bone substitute applications -- in vitro characterization.

Porous structures were formed by gravity sintering calcium polyphosphate (CPP) particles of either 106-150 or 150-250 microm size to form samples with 30-45 vol% porosity with pore sizes in the range of 100 microm (40-140 microm). Tensile strength of the samples assessed by diametral compression testing indicated relatively high values for porous ceramics with a maximum strength of 24.1 MPa for samples made using the finer particles (106-150 microm). X-ray diffraction studies of the sintered samples indicated the formation of beta-CPP from the starting amorphous powders. In vitro aging in 0.1 M tris-buffered solution (pH 7.4) or 0.05 M potassium hydrogen phthalate buffered solution (pH 4.0) at 37 degreesC for periods up to 30d indicated an initial rapid loss of strength and P elution by 1 d followed by a more gradual continuing strength and P loss resulting in strengths at 30d equal to about one-third the initial value. The observed structures, strengths and in vitro degradation characteristics of the porous CPP samples suggested their potential usefulness as bone substitute materials pending subsequent in vivo behaviour assessment.

Bone Substitutes↗