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PubMed1992

Calcium hydroxyapatite ceramic used as a delivery system for antibiotics.

Porous blocks of calcium hydroxyapatite ceramic were evaluated as delivery systems for the sustained release of antibiotics. We tested gentamicin sulphate, cefoperazone sodium, and flomoxef sodium in powder form placed in a cylindrical cavity in calcium hydroxyapatite blocks, using in vitro studies of elution and in vivo studies in rats. Gentamicin sulphate gave a maximum concentration within the first week, which gradually decreased but was still effective at 12 weeks, when 70% of the antibiotic had been released. Even at this stage the antibiotic concentration from a 75 mg dose was five times the minimum inhibitory concentration for staphylococci. In the in vivo studies the release of gentamicin sulphate into the normal bone of rats was at similar rates and levels. The bacteriocidal activity of the drugs was not affected by packing into calcium hydroxyapatite ceramic and the blocks were completely biocompatible on histology. This new system overcomes the disadvantages of other drug delivery systems, avoiding thermal damage to the antibiotics and a second operation for the removal of the carrier. Some mechanical strength is provided by the ceramic and healing may be accelerated by bone ingrowth into its micropores.

Animals↗
PubMed2002

Nuclear magnetic resonance spin-spin relaxation of the crystals of bone, dental enamel, and synthetic hydroxyapatites.

Studies of the apatitic crystals of bone and enamel by a variety of spectroscopic techniques have established clearly that their chemical composition, short-range order, and physical chemical reactivity are distinctly different from those of pure hydroxyapatite. Moreover, these characteristics change with aging and maturation of the bone and enamel crystals. Phosphorus-31 solid state nuclear magnetic resonance (NMR) spin-spin relaxation studies were carried out on bovine bone and dental enamel crystals of different ages and the data were compared with those obtained from pure and carbonated hydroxyapatites. By measuring the 31P Hahn spin echo amplitude as a function of echo time, Van Vleck second moments (expansion coefficients describing the homonuclear dipolar line shape) were obtained and analyzed in terms of the number density of phosphorus nuclei. 31P magnetization prepared by a 90 degree pulse or by proton-phosphorus cross-polarization (CP) yielded different second moments and experienced different degrees of proton spin-spin coupling, suggesting that these two preparation methods sample different regions, possibly the interior and the surface, respectively, of bone mineral crystals. Distinct differences were found between the biological apatites and the synthetic hydroxyapatites and as a function of the age and maturity of the biological apatites. The data provide evidence that a significant fraction of the protonated phosphates (HPO4(-2)) are located on the surfaces of the biological crystals, and the concentration of unprotonated phosphates (PO4(-3)) within the apatitic lattice is elevated with respect to the surface. The total concentration of the surface HPO4(-2) groups is higher in the younger, less mature biological crystals.

Aging↗
PubMed2002

Short-term evaluation of non-absorbable microgranular hydroxyapatite infiltration in the guinea pig subepidermal abdominal region.

Non-absorbable microgranular hydroxyapatite was infiltrated into the subepidermal abdominal region of guinea pigs in order to assess the possibility of using this material to correct deficiencies in orbital volume. Microgranular hydroxyapatite (2.0 ml) was subepidermally infiltrated into the abdominal region of 20 guinea pigs. The animals were divided into four experimental groups of 5 animals each, which were killed 7 (G1), 15 (G2), 30 (G3) and 60 (G4) days after infiltration. The area and the largest and smallest diameters of the nodules formed by infiltration were evaluated at the site of infiltration and histological examination was performed. The mean granuloma area was similar in all groups. Histopathological examination showed that the material remained isolated from surrounding tissues by a pseudocapsule that became denser throughout the experiment. A host reaction started with young fibroblastic tissue that evolved to dense tissue until cartilaginous tissue was formed in G4, progressively advancing towards the center of the granuloma from G1 to G4. Non-absorbable microgranular hydroxyapatite is an inert material that was well tolerated by the animals studied, with maintenance of the infiltrated volume, and may perhaps be useful to fill anophthalmic cavities.

Abdominal Muscles↗
PubMed1994

Micromotion of femoral stems in total hip arthroplasty. A randomized study of cemented, hydroxyapatite-coated, and porous-coated stems with roentgen stereophotogrammetric analysis.

The fixation of the femoral stem in a total hip arthroplasty was studied in sixty patients (sixty-four hips) with use of roentgen stereophotogrammetric analysis. The hips were randomly stratified on the basis of the age, sex, and weight of the patient; the roentgenographic quality of the bone; and the reason for the operation (primary or secondary osteoarthrosis). The hips were then randomly assigned to one of three types of fixation of the femoral component: insertion with cement, hydroxyapatite coating, or porous coating. Examinations with roentgen stereophotogrammetry were done as long as two years after the operation. Micromotion of the prostheses was evaluated in terms of subsidence or proximal migration and rotations and translations of the proximal-lateral (shoulder) and distal (tip) parts of the prostheses. The clinical results at the two-year follow-up evaluation did not differ significantly between the groups with regard to the Harris hip score or the pain score (p > 0.05 for both; Wilcoxon rank-sum test). There were small or no differences in rotations and micromotions of the shoulder and the tip of the prostheses. Increased subsidence of 0.1 to 0.2 millimeter was recorded for the cemented and the porous-coated prostheses (p = 0.002 and p = 0.02, respectively; Wilcoxon rank-sum test). Thus, proximal hydroxyapatite coating seems to enhance the early fixation of the stem. Conventional roentgenography revealed an increased number of radiodense lines surrounding the porous-coated prostheses. Distal hypertrophy of the femoral cortex was found mainly around the hydroxyapatite-coated prostheses. Proximal resorption of bone and heterotopic ossification occurred to approximately the same extent regardless of the type of fixation used.

Adult↗
PubMed1996

Remodeling of bone around hydroxyapatite-coated femoral stems.

Two hundred and twenty-four total hip arthroplasties were performed in 201 patients with use of a femoral component with hydroxyapatite coating of the proximal portion of the stem. The mean duration of follow-up was seventy-one months (range, fifty-eight to eighty-seven months). Of the 224 arthroplasties, 208 (93 per cent; 190 patients) yielded a good or excellent clinical result. Four patients (2 per cent) reported mild-to-moderate activity-related pain in the thigh, and two (1 per cent) had aseptic loosening. The radiographic findings of progressive new-bone formation (cancellous condensation and cortical hypertrophy) throughout the zones adjacent to the middle and distal portions of the stem were evidence of early, extensive proximal fixation of the implant, with distal stress transfer through the implant, which is stiffer than the surrounding bone. Remodeling of the femur began early, was predictable, and progressed throughout the follow-up period. Cortical hypertrophy about the middle and distal portions of the stem occurred predominantly in the mediolateral plane (in 105 hips [47 per cent], compared with thirteen hips [6 per cent] in the anteroposterior plane), and it was more common in patients who had had poorer bone quality preoperatively. Intramedullary osteolysis was present in one femur (0.4 per cent) at five years; the osteolytic area was less than five millimeters in its greatest dimension and had not progressed at the time of the six-year follow-up evaluation. This low rate of osteolysis suggests that a circumferential coating of hydroxyapatite may effectively minimize migration of wear debris along the femoral stem. The progressive remodeling of the femur about the middle and distal portions of the stem, as evidenced by cancellous condensation and cortical hypertrophy, has not, to our knowledge, been described previously to this magnitude in association with proximally coated (porous or hydroxyapatite-coated) femoral implants.

Adolescent↗
PubMed1980

Solubilization of hydroxyapatite at neutral pH by an anionic ionic exchange resin.

Sucrose, induced dental plaque has been shown to contain high amounts of lipoteichoic acids, a bacterial anionic polymer with chemical properties similar to ionic exchange resins. The present study describes an in vitro experiment where a commercial resin Amberlite IR 120 was shown to dissolve hydroxyapatite at neutral pH. The resin binds calcium and the dissociation of the hydroxyapatite Ca5(PO4)3OH leads to 5Ca++ +3 PO4(-3) + OH- is driven to the right as long as the resin takes up calcium. The dissociation of the hydroxyapatite was monitored by electrical conductivity and pH of the aqueous phase. It is suggested that this mechanism may be of some significance in vivo.

Anion Exchange Resins↗
PubMed1996

Clinical outcome after one year following samarium-153 particulate hydroxyapatite radiation synovectomy.

The clinical outcome and tolerability following treatment with samarium-153 particulate hydroxyapatite was evaluated in patients with persistent rheumatoid knee synovitis. The clinical review of 18 patients treated with intra-articular samarium-153 particulate hydroxyapatite combined with triamcinolone hexacetonide who had failed to obtain more than 4 weeks symptom relief from a prior intra-articular glucocorticoid injection was undertaken. No unwanted effects from the treatment were observed. Symptom relief was maintained in 56% patients at 6 months and in 44% of patients at 12 months following treatment. Median duration of symptom relief was 9 months. There was a significantly higher mean baseline Ritchie Articular Index in patients relapsing within 3 months and a trend towards earlier relapse in patients with higher indices of disease activity at the time of treatment. There was a trend towards earlier relapse in patients with a poor range of knee flexion at baseline and with worse indices of intra-articular radiopharmaceutical distribution. Samarium-153 particulate hydroxyapatite knee synovectomy is well tolerated and may be an effective treatment for carefully selected patients with persistent rheumatoid knee synovitis.

Adult↗
PubMed1992

Hydroxyapatite coating modifies implant membrane formation. Controlled micromotion studied in dogs.

We studied the influence of controlled micromovements between bone and porous titanium alloy implants with and without hydroxyapatite coating. A dynamically loaded unstable device producing approximately 150-microns axial translation of knee implants during each gait cycle was developed. Stable implants served as controls. Matched stable and unstable implants with either porous titanium (Ti) or hydroxyapatite (HA) coating surrounded by a gap of 0.75 mm were inserted into the weight-bearing regions of the medial femoral condyles in 14 mature dogs. Histologic analysis after 4 weeks showed a fibrous membrane surrounding both types of implants subjected to micromovements, whereas various amounts of bone ingrowth was obtained in the stable implants. The membrane around unstable HA implants was thinner than that around unstable Ti implants. Islands of fibrocartilaginous tissue characterized the membrane around unstable HA implants, whereas fibrous connective tissue surrounded unstable Ti implants. The collagen concentration of the fibrous membranes was higher around unstable HA implants compared with Ti implants. Instability reduced the shear strength of the implants. However, the shear strength of unstable HA implants exceeded that of the Ti implants, both unstable and stable. The greatest shear strength was obtained by stable HA implants, i.e., tenfold greater than that of stable Ti implants. The gap-healing capacity around stable HA implants increased toward the HA surface, and was greater than that around Ti implants. Our study demonstrates that micromovements between bone and implant inhibit bone ingrowth and lead to the development of a fibrous membrane. The superior fixation of unstable HA implants compared with unstable Ti implants may be ascribed to the presence of fibrocartilage, a higher collagen concentration, and radiating orientation of collagen fibers in the membrane. The strongest mechanical anchorage and the greatest amount of bone ingrowth was obtained by stable implants coated with hydroxyapatite.

Alloys↗
PubMed1994

Bone formation in coralline hydroxyapatite. Effects of pore size studied in rabbits.

We analyzed osseous reactions in the rabbit femoral condyle to coralline hydroxyapatite bone substitutes of various pore sizes by radiology and histology. The results were compared to bone repair of empty cavities and to integration of allografts. Spontaneous bone repair of the empty cavities took approximately 12 weeks, while integration of the cryopreserved allografts occurred after 9 weeks. However, no signs of new bone formation were found with the 200 microns pore size hydroxyapatite. In contrast, there was substantial production of bone within the 500 microns pore size implants at 12 and 26 weeks. Our results indicate that the pore size of the coralline hydroxyapatite influenced the development of bone in the implants in the cancellous bone bed of the rabbit femoral condyle. The results also show that spontaneous bone repair should be taken into consideration when the integration of implants is evaluated.

Animals↗
PubMed1994

Two-year outcome of hydroxyapatite-coated prostheses. Two femoral prostheses retrieved at autopsy.

We performed a histological study of the bone-implant interface on 2 human femurs implanted with a hydroxyapatite-coated self-locking stem for 2 years. Extensive bone formation with no intervening fibrous tissue was noted around the entire circumference of the 2 prostheses. The newly-formed bone had 2 morphotypes: an alveolar disposition with a continuous contact between bone and hydroxyapatite, and a digitiform one where distinct bony trabeculae were in contact with the ceramic coating or with the bone marrow. Partial or even total resorption of the hydroxyapatite coating was clearly identified, these areas showing bone in contact with the metal.

Aged↗
PubMed1990

[Observation on implants of porous hydroxyapatite granules in periodontal osseous defects].

UNLABELLED: The purpose of this study was to observe the regeneration of the periodontal tissue using porous hydroxyapatite granules in experimental periodontal lesions. The upper lateral incisors of three Macaca fuscatae were extracted. After a 12-week recovery period, three wall infrabony defects were surgically prepared on the distal surface of the central incisors. In order to accumulate the plaque and cause inflammation, a wire with dental floss was placed inside the defects for a period of four weeks and then removed. Flap operations were performed and porous hydroxyapatite granules were placed into the defects. Twelve weeks after surgery, the samples were taken out and fixed in glutaraldehyde solution. They were embedded in polyester resin and undecalcified sections were prepared. The specimens were stained with toluidine blue and observed under light microscope. RESULTS: 1) The implanted area was divided into three distinctive zones. The first zone was located distally and occupied two-thirds of the total area. A large quantity of osseous tissue was detected. The second zone was situated near the root and presented only a small quantity of osseous tissue; Fibrous connective tissue predominated in the third zone adjacent to the root. 2) Bone apposition and resorption caused by physiologic mobility and movement of the teeth were observed. These results suggest that the elimination of the functional forces is advisable during the healing period whenever hydroxyapatite granules are placed into the periodontal defect.

Animals↗
PubMed2001

[Initiative report of the hydroxyapatite orbital implant drilling procedure].

OBJECTIVE: To evaluate the clinical effect of drilling procedure following the hydroxyapatite orbital implantation. METHODS: From February 1996 to April 2000, 146 consecutive patients who received hydroxyapatite orbital implant were drilled and inserted a motility peg 6 to 16 months after hydroxyapatite implantation. Among them, there were 97 males and 49 females, aged from 18 to 60 years old, of the 146 motility pegs, 36 were sleeved pegs and 110 were nonsleeved. Goldman visual field analyzer was applied to measure the degree of artificial eye's movement before and after drilling. RESULTS: Followed up for 1 to 40 months, no secondary infection occurred. The mobility of the prosthesis increased from (18.7 +/- 3.8) degrees preoperatively to (42.3 +/- 3.7) degrees postoperatively. CONCLUSION: The delayed drilling procedure and motility peg insertion improve the range of movement and the sensitivity of the artificial eye with a low rate of complications.

Adolescent↗
PubMed2001

[Current evolution of plasma sprayed hydroxyapatite coating].

The present attempt is to briefly review the processing and properties of plasma sprayed hydroxyapatite coatings in terms of characteristics of hydroxyapatite ceramics, plasma spraying technology, titanium-ceramic interfacial cracking and component designing of hydroxyapatite coating based composite. The coating is a weak part in implant system. The main purpose of research on plasma spraying technology and component designing is to improve coating integrality and coating-matrix adhesion strength. Functionally gradient materials can provide a new route to solve the above two problems.

Biomechanical Phenomena↗
PubMed2001

[A study of the effects of basic fibroblast growth factor on fibrovascular ingrowth into hydroxyapatite orbital implants].

OBJECTIVE: To investigate the effects of different doses of basic fibroblast growth factor (bFGF) on the fibrovascular ingrowth into hydroxyapatite orbital implants. METHODS: Thirty-six New Zealand albino rabbits were divided into 4 groups, and hydroxyapatite orbital spheres were implanted into their orbits. The implants were pretreated with 0.5, 1.5 and 5.0 g/L bFGF solution respectively in 3 groups, the untreated implants were used in the control group. At the postoperative 2, 4 and 6 weeks the implants were harvested. Observers classified the extent of the fibrovascular ingrowth in a blind manner under light microscopy. RESULTS: Histologic studies demonstrated that postoperatively, the rate of vascularization of the implants pretreated with 1.5 and 5.0 g/L bFGF solution was significantly increased at week 2 in comparison with that of the control group. No difference was noted between the group with the implants pretreated with 0.5 g/L bFGF solution and the control group. CONCLUSION: The bFGF 1.5 and 5.0 g/L in concentration may promote the fibrovascular ingrowth into hydroxyapatite orbital implants at week 2 after the implantation.

Animals↗
PubMed1999

Hydroxyapatite cement in craniofacial trauma surgery: indications and early experience.

BACKGROUND AND OBJECTIVES: Reconstruction of the nonstress-bearing portions of the craniofacial skeleton has recently utilized several alloplastic compounds. One such recent compound is hydroxyapatite cement (HAC)--a calcium-phosphate-based product. Its chemical structure consists primarily of calcium phosphate, as does human bone, and this similarity in the mineral structure renders it biocompatible. METHODS AND MATERIALS: Based on clinical indications for HAC, the authors have classified acquired craniofacial defects into four types. This article presents 5 clinical cases with craniofacial fractures, sustained in various accidents, in which hydroxyapatite cement was used to prevent cranial deformities or to reinstate contour. RESULTS AND/OR CONCLUSIONS: Complications were encountered in some of these cases, but all patients healed without any secondary complications. While the short-term experience using hydroxyapatite cement in craniofacial trauma surgery has been favorable, long-term studies in humans are required to validate the safety and efficacy of this product.

Adolescent↗
PubMed1992

Early clinical experience with hydroxyapatite-coated femoral implants.

As part of a multi-center study, 238 titanium stems that were proximally coated with hydroxyapatite were implanted in 220 patients between January 1988 and December 1989. Ninety-two of these stems in eighty-three patients had a minimum of two years of follow-up, including analysis of the clinical and radiographic data. Clinically, the patients were essentially pain-free before six months and had a low (4 per cent) prevalence of pain in the thigh and a very high composite Harris hip-score (mean, 95 points) at two years. Radiographically, subsidence was detected in 8 per cent of the implants; no implant had more than three millimeters of subsidence. Radiolucencies were characteristically seen around the uncoated distal part of the stem, in 70 per cent of the implants. Contrastingly, radiolucencies were rare in the hydroxyapatite-coated proximal zones and were most often found anteriorly, in only 5 per cent of the implants. Areas of increased formation of cancellous bone were seen beneath femoral cortical bone at the interface between the hydroxyapatite-coated and uncoated parts of the stem, in 67 per cent of the implants. Calcar resorption was found in 49 per cent of the implants. Cortical thickening was present in 17 per cent of the implants at the uncoated distal part of the stem. Two of the 238 femoral implants were revised: one because of infection and one because of aseptic loosening associated with non-union of a subtrochanteric osteotomy.

Adult↗
PubMed2004

Synthesis of nanosized hydroxyapatite powders.

Hydroxyapatite powder was mechanochemically synthesized from calcium pyrophosphate (Ca2P2O7) and calcium carbonate (CaCO3) using a solid-state reaction. The two powders were mixed in distilled water, milled for 8 hours, dried and calcined at 1100 degrees C for 1 hour. The phase(s) formed was analyzed by x-ray diffraction (XRD). It was found that hydroxyapatite was not the only one formed. This result will be used as the starting point to produce a single-phase hydroxyapatite in terms of excess hydroxyl group in a mechanochemical reaction.

Biocompatible Materials↗
PubMed1992

Hydroxyapatite implants--a new trend in enucleation and orbital reconstructive surgery.

As treatment modalities evolve in ophthalmology one must assess and re-evaluate current methods of therapy in the care and treatment of the patient facing the loss of an eye. With the advent of Hydroxyapatite Orbital Implants, new challenges face the ophthalmic nurse in caring for the patient undergoing enucleation and reconstructive surgery. Integrated orbital implants are used to replace the volume of the orbit when the eye is removed due to enucleation, evisceration, or as secondary orbital implants. Various materials have been used in the past to replace orbital volume, with the most common being silicone or polymethylmethacrylate. Hydroxyapatite is a new orbital implant material which has unique interconnected porous matrix derived from marine corals with a mineral composition similar to bone. This orbital implant undergoes fibrovascular ingrowth by the patient's own tissue, becoming truly integrated and less likely to reject, migrate or extrude. The hydroxyapatite implant may be inserted with a variety of surgical techniques, all of which are more complex than standard enucleation implant techniques and have special considerations for the ophthalmic registered nurse.

Eye Enucleation↗