Cancellous Bone (cancellous + bone)

Distribution by Scientific Domains


Selected Abstracts


Quantitative Ultrasound Does Not Reflect Mechanically Induced Damage in Human Cancellous Bone

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2000
P. H. F. Nicholson
Abstract This study investigated the ability of quantitative ultrasound (QUS) to detect reductions in the elastic modulus of cancellous bone caused by mechanical damage. Ultrasonic velocity and attenuation were measured using an in-house parametric imaging system in 46 cancellous bone cores from the human calcaneus. Each core was subjected to a mechanical testing regime to (a) determine the predamage elastic modulus, (b) induce damage by applying specified strains in excess of the yield strain, and (c) measure the postdamage elastic modulus. The specimens were divided into four groups: a control group subjected to a nominally nondestructive 0.7% maximum strain (,m) and three damage groups subjected to increasing strain levels (,m = 1.5, 3.0, and 4.5%). QUS measurements before and after the mechanical testing showed no significant differences between the control group and damage groups, despite highly significant (p < 0.001) reductions in the elastic modulus of up to 72%. These results indicate that current QUS techniques do not intrinsically reflect the elastic properties of cancellous bone. This is consistent with ultrasonic properties being determined by other factors (apparent density and/or architecture), which normally are associated strongly with elastic properties, but only when bone is mechanically intact. Clinically, this implies that ultrasound cannot be expected to detect bone fragility in the absence of major changes in bone density and/or trabecular architecture. [source]


Donor site morbidity after harvesting of proximal tibia bone

HEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 6 2006
Yuan-Chien Chen DDS
Abstract Background. Bone-grafting procedures are common in head and neck surgery. Donor site morbidity is an important factor in deciding the site for harvest of cancellous bone. The tibia has been recommended as a harvest site. Use of the proximal tibia as a donor site is associated with few complications. Our present study used proximal tibia bone grafts to reconstruct maxillofacial defects and augment bone volume for implantation. Methods. A retrospective study was undertaken to analyze 40 proximal tibia bone grafts in maxillofacial reconstruction. Minimal follow-up was 6 months. Results. There were no major complications during the follow-up period. Early minor complications (15%) included temporary sensory loss and ecchymosis. Late minor complication (2.5%) was gait disturbance for 2 months. Long-term minor complication (2.5%) was an unsightly scar. Conclusion. The procedure for proximal tibia bone graft is easy, has less operative risk, and results in a lower postoperative morbidity rate. Based on our findings, we believe the proximal tibia offers a reliable site for harvest of sufficient quantities of good-quality cancellous bone. © 2006 Wiley Periodicals, Inc. Head Neck 28:496,500, 2006 [source]


Bone-like Resorbable Silk-based Scaffolds for Load-bearing Osteoregenerative Applications,

ADVANCED MATERIALS, Issue 1 2009
Andrew M. Collins
Hydroxyapatite/silk biocompatible composites with unprecedented mechanical strength and toughness areproduced in a new process with theintegrated mineralization of macroporous silk fibroin scaffolds. Thebiomimetic bone-like composites areabsorbable and load-bearing with compressive strength, modulus, andtoughness comparable to the mechanical tolerances of cancellous bone. [source]


Regional variability in secondary remodeling within long bone cortices of catarrhine primates: the influence of bone growth history

JOURNAL OF ANATOMY, Issue 3 2008
Shannon C. McFarlin
Abstract Secondary intracortical remodeling of bone varies considerably among and within vertebrate skeletons. Although prior research has shed important light on its biomechanical significance, factors accounting for this variability remain poorly understood. We examined regional patterning of secondary osteonal bone in an ontogenetic series of wild-collected primates, at the midshaft femur and humerus of Chlorocebus (Cercopithecus) aethiops (n = 32) and Hylobates lar (n = 28), and the midshaft femur of Pan troglodytes (n = 12). Our major objectives were: 1) to determine whether secondary osteonal bone exhibits significant regional patterning across inner, mid-cortical and outer circumferential cortical rings within cross-sections; and if so, 2) to consider the manner in which this regional patterning may reflect the influence of relative tissue age and other circumstances of bone growth. Using same field-of-view images of 100-µm-thick cross-sections acquired in brightfield and circularly polarized light microscopy, we quantified the percent area of secondary osteonal bone (%HAV) for whole cross-sections and across the three circumferential rings within cross-sections. We expected bone areas with inner and middle rings to exhibit higher %HAV than the outer cortical ring within cross-sections, the latter comprising tissues of more recent depositional history. Observations of primary bone microstructural development provided an additional context in which to evaluate regional patterning of intracortical remodeling. Results demonstrated significant regional variability in %HAV within all skeletal sites. As predicted,%HAV was usually lowest in the outer cortical ring within cross-sections. However, regional patterning across inner vs. mid-cortical rings showed a more variable pattern across taxa, age classes, and skeletal sites examined. Observations of primary bone microstructure revealed that the distribution of endosteally deposited bone had an important influence on the patterning of secondary osteonal bone across rings. Further, when present, endosteal compacted coarse cancellous bone always exhibited some evidence of intracortical remodeling, even in those skeletal sites exhibiting comparatively low %HAV overall. These results suggest that future studies should consider the local developmental origin of bone regions undergoing secondary remodeling later in life, for an improved understanding of the manner in which developmental and mechanical factors may interact to produce the taxonomic and intraskeletal patterning of secondary bone remodelling in adults. [source]


The salmon vertebral body develops through mineralization of two preformed tissues that are encompassed by two layers of bone

JOURNAL OF ANATOMY, Issue 2 2005
Kari Nordvik
Abstract The teleost backbone consists of amphicoelous vertebrae and intervertebral ligaments, both of which include notochord-derived structures. On the basis of a sequential developmental study of the vertebral column of Atlantic salmon (Salmo salar L.) from the egg stage up to early fry stage (300,2500 day-degrees) we show that the vertebral body consists of four layers or compartments, two of which are formed through mineralization of preformed collagenous tissue (the notochordal sheath and the intervertebral ligament) and two of which are formed through ossification. The three inner layers have ordered lamellar collagen matrixes, which alternate perpendicularly from layer to layer, whereas the outer layer consists of cancellous bone with a woven matrix. The bone layers also differ in osteocyte content. In this study we describe the structural details of the layers, and their modes of formation. The results are compared with previous descriptions, and possible phylogenetic implications are discussed. [source]


Evidence of a hypermineralised calcified fibrocartilage on the human femoral neck and lesser trochanter

JOURNAL OF ANATOMY, Issue 2 2001
J. E. SHEA
Femoral neck fractures are a major cause of morbidity and mortality in elderly humans. In addition to the age-related loss of cancellous bone, changes to the microstructure and morphology of the metaphyseal cortex may be a contributing factor in osteoporotic hip fractures. Recent investigations have identified a hypermineralised tissue on the neck of the femur and trochanteric region that increases in fractional area with advancing age in both males (Boyce & Bloebaum, 1993) and females (Vajda & Bloebaum, 1999). The aim of this study was to determine if the hypermineralised tissue previously observed on the proximal femur is calcified fibrocartilage. Regional variations in the fractional area of hypermineralised tissue, cortical bone, and porosity of the cortical bone along the neck of the femur and lesser trochanter were also quantified. Comparison of back scattered electron and light microscope images of the same area show that regions of hypermineralised tissue correlate with the regions of calcified fibrocartilage from tendon and capsular insertions. The hypermineralised tissue and calcified fibrocartilage had similar morphological features such as the interdigitations of the calcified fibrocartilage into the bone, lacunar spaces, and distinctly shaped pores adjacent to the 2 tissues. Regions of the neck that did not contain insertions were covered with periosteum. There were no regional differences (P > 0.05) on the superior and inferior femoral neck in terms of the percentage area of hypermineralised calcified fibrocartilage, cortical bone, or cortical bone porosity. The lesser trochanter exhibited regional differences in the fractional area of hypermineralised calcified fibrocartilage (P = 0.007) and cortical bone (P = 0.007) but not porosity of the cortical bone (P > 0.05). The effects of calcified fibrocartilage on femoral neck periosteal expansion, repair, and mechanics are unknown, but may play a role in osteoporotic fractures and intracapsular fracture healing. [source]


Fourier analysis methodology of trabecular orientation measurement in the human tibial epiphysis

JOURNAL OF ANATOMY, Issue 2 2001
M. HERRERA
Methods to quantify trabecular orientation are crucial in order to assess the exact trajectory of trabeculae in anatomical and histological sections. Specific methods for evaluating trabecular orientation include the ,point counting' technique (Whitehouse, 1974), manual tracing of trabecular outlines on a digitising board (Whitehouse, 1980), textural analysis (Veenland et al. 1998), graphic representation of vectors (Shimizu et al. 1993; Kamibayashi et al. 1995) and both mathematical (Geraets, 1998) and fractal analysis (Millard et al. 1998). Optical and computer-assisted methods to detect trabecular orientation of bone using the Fourier transform were introduced by Oxnard (1982) later refined by Kuo & Carter (1991) (see also Oxnard, 1993, for a review), in the analysis of planar sections of vertebral bodies as well as in planar radiographs of cancellous bone in the distal radius (Wigderowitz et al. 1997). At present no studies have applied this technique to 2-D images or to the study of dried bones. We report a universal computer-automated technique for assessing the preferential orientation of the tibial subarticular trabeculae based on Fourier analysis, emphasis being placed on the search for improvements in accuracy over previous methods and applied to large stereoscopic (2-D) fields of anatomical sections of dried human tibiae. Previous studies on the trajectorial architecture of the tibial epiphysis (Takechi, 1977; Maquet, 1984) and research data about trabecular orientation (Kamibayashi et al. 1995) have not employed Fourier analysis. [source]


Comments on Neutron diffraction studies of collagen in human cancellous bone by Skakle & Aspden (2002)

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2004
Sidney Lees
Comments are made on a paper by Skakle & Aspden [J. Appl. Cryst. (2002), 35, 506508] regarding the lateral spacing of collagen in human bone. [source]


Microarchitecture Influences Microdamage Accumulation in Human Vertebral Trabecular Bone,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 10 2008
Monique E Arlot
Abstract It has been suggested that accumulation of microdamage with age contributes to skeletal fragility. However, data on the age-related increase in microdamage and the association between microdamage and trabecular microarchitecture in human vertebral cancellous bone are limited. We quantified microdamage in cancellous bone from human lumbar (L2) vertebral bodies obtained from 23 donors 54,93 yr of age (8 men and 15 women). Damage was measured using histologic techniques of sequential labeling with chelating agents and was related to 3D microarchitecture, as assessed by high-resolution ,CT. There were no significant differences between sexes, although women tended to have a higher microcrack density (Cr.Dn) than men. Cr.Dn increased exponentially with age (r = 0.65, p < 0.001) and was correlated with bone volume fraction (BV/TV; r = ,0.55; p < 0.01), trabecular number (Tb.N; r = ,0.56 p = 0.008), structure model index (SMI; r = 0.59; p = 0.005), and trabecular separation (Tb.Sp; r = 0.59; p < 0.009). All architecture parameters were strongly correlated with each other and with BV/TV. Stepwise regression showed that SMI was the best predictor of microdamage, explaining 35% of the variance in Cr.Dn and 20% of the variance in diffuse damage accumulation. In addition, microcrack length was significantly greater in the highest versus lowest tertiles of SMI. In conclusion, in human vertebral cancellous bone, microdamage increases with age and is associated with low BV/TV and a rod-like trabecular architecture. [source]


Mapping Quantitative Trait Loci for Vertebral Trabecular Bone Volume Fraction and Microarchitecture in Mice,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2004
Mary L Bouxsein
Abstract BMD, which reflects both cortical and cancellous bone, has been shown to be highly heritable; however, little is known about the specific genetic factors regulating trabecular bone. Genome-wide linkage analysis of vertebral trabecular bone traits in 914 adult female mice from the F2 intercross of C57BL/6J and C3H/HeJ inbred strains revealed a pattern of genetic regulation derived from 13 autosomes, with 5,13 QTLs associated with each of the traits. Ultimately, identification of genes that regulate trabecular bone traits may yield important information regarding mechanisms that regulate mechanical integrity of the skeleton. Introduction: Both cortical and cancellous bone influence the mechanical integrity of the skeleton, with the relative contribution of each varying with skeletal site. Whereas areal BMD, which reflects both cortical and cancellous bone, has been shown to be highly heritable, little is known about the genetic determinants of trabecular bone density and architecture. Materials and Methods: To identify heritable determinants of vertebral trabecular bone traits, we evaluated the fifth lumbar vertebra from 914 adult female mice from the F2 intercross of C57BL/6J (B6) and C3H/HeJ (C3H) progenitor strains. High-resolution ,CT was used to assess total volume (TV), bone volume (BV), bone volume fraction (BV/TV), trabecular thickness (Tb.Th), separation (Tb.Sp), and number (Tb.N) of the trabecular bone in the vertebral body in the progenitors (n = 8/strain) and female B6C3H-F2 progeny (n = 914). Genomic DNA from F2 progeny was screened for 118 PCR-based markers discriminating B6 and C3H alleles on all 19 autosomes. Results and Conclusions: Despite having a slightly larger trabecular bone compartment, C3H progenitors had dramatically lower vertebral trabecular BV/TV (,53%) and Tb.N (,40%) and higher Tb.Sp (71%) compared with B6 progenitors (p < 0.001 for all). Genome-wide quantitative trait analysis revealed a pattern of genetic regulation derived from 13 autosomes, with 5,13 quantitative trait loci (QTLs) associated with each of the vertebral trabecular bone traits, exhibiting adjusted LOD scores ranging from 3.1 to 14.4. The variance explained in the F2 population by each of the individual QTL after adjusting for contributions from other QTLs ranged from 0.8% to 5.9%. Taken together, the QTLs explained 22,33% of the variance of the vertebral traits in the F2 population. In conclusion, we observed a complex pattern of genetic regulation for vertebral trabecular bone volume fraction and microarchitecture using the F2 intercross of the C57BL/6J and C3H/HeJ inbred mouse strains and identified a number of QTLs, some of which are distinct from those that were previously identified for total femoral and vertebral BMD. Identification of genes that regulate trabecular bone traits may ultimately yield important information regarding the mechanisms that regulate the acquisition and maintenance of mechanical integrity of the skeleton. [source]


Prevention of Postmenopausal Bone Loss by a Low-Magnitude, High-Frequency Mechanical Stimuli: A Clinical Trial Assessing Compliance, Efficacy, and Safety,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 3 2004
Clinton Rubin
Abstract A 1-year prospective, randomized, double-blind, and placebo-controlled trial of 70 postmenopausal women demonstrated that brief periods (<20 minutes) of a low-level (0.2g, 30 Hz) vibration applied during quiet standing can effectively inhibit bone loss in the spine and femur, with efficacy increasing significantly with greater compliance, particularly in those subjects with lower body mass. Introduction: Indicative of the anabolic potential of mechanical stimuli, animal models have demonstrated that short periods (<30 minutes) of low-magnitude vibration (<0.3g), applied at a relatively high frequency (20,90 Hz), will increase the number and width of trabeculae, as well as enhance stiffness and strength of cancellous bone. Here, a 1-year prospective, randomized, double-blind, and placebo-controlled clinical trial in 70 women, 3,8 years past the menopause, examined the ability of such high-frequency, low-magnitude mechanical signals to inhibit bone loss in the human. Materials and Methods: Each day, one-half of the subjects were exposed to short-duration (two 10-minute treatments/day), low-magnitude (2.0 m/s2 peak to peak), 30-Hz vertical accelerations (vibration), whereas the other half stood for the same duration on placebo devices. DXA was used to measure BMD at the spine, hip, and distal radius at baseline, and 3, 6, and 12 months. Fifty-six women completed the 1-year treatment. Results and Conclusions: The detection threshold of the study design failed to show any changes in bone density using an intention-to-treat analysis for either the placebo or treatment group. Regression analysis on the a priori study group demonstrated a significant effect of compliance on efficacy of the intervention, particularly at the lumbar spine (p = 0.004). Posthoc testing was used to assist in identifying various subgroups that may have benefited from this treatment modality. Evaluating those in the highest quartile of compliance (86% compliant), placebo subjects lost 2.13% in the femoral neck over 1 year, whereas treatment was associated with a gain of 0.04%, reflecting a 2.17% relative benefit of treatment (p = 0.06). In the spine, the 1.6% decrease observed over 1 year in the placebo group was reduced to a 0.10% loss in the active group, indicating a 1.5% relative benefit of treatment (p = 0.09). Considering the interdependence of weight, the spine of lighter women (<65 kg), who were in the highest quartile of compliance, exhibited a relative benefit of active treatment of 3.35% greater BMD over 1 year (p = 0.009); for the mean compliance group, a 2.73% relative benefit in BMD was found (p = 0.02). These preliminary results indicate the potential for a noninvasive, mechanically mediated intervention for osteoporosis. This non-pharmacologic approach represents a physiologically based means of inhibiting the decline in BMD that follows menopause, perhaps most effectively in the spine of lighter women who are in the greatest need of intervention. [source]


Irreversible Perforations in Vertebral Trabeculae?,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 7 2003
X Banse
In human cancellous bone, osteoclastic perforations resulting from normal remodeling were generally considered irreversible. In human vertebral samples, examined by backscatter electron microscopy, there was clear evidence of bridging of perforation defects by new bone formation. Hence trabecular perforations may not be irreversible. Introduction: Preservation of the trabecular bone microarchitecture is essential to maintain its load-bearing capacity and prevent fractures. However, during bone remodeling, the osteoclasts may perforate the platelike trabeculae and disconnect the structure. Large perforations (>100 ,m) are generally considered irreversible because there is no surface on which new bone can be laid down. In this work, we investigated the outcome of these perforations on human vertebral cancellous bone. Materials and Methods: Using backscatter electron microscopy, we analyzed 264 vertebral bone samples from the thoracic and lumbar spine of nine subjects (44,88 years old). Nine fields (2 × 1.5 mm) were observed on each block. Several bone structural units (BSUs) were visible on a single trabecula, illustrating a dynamic, historical aspect of bone remodeling. A bridge was defined as a single and recent BSU connecting two segments of trabeculae previously separated by osteoclastic resorption. They were counted and measured (length and breadth, ,m). Results and Conclusion: We observed 396 bridges over 2376 images. By comparison, we found only 15 microcalluses on the same material. The median length of the bridge was 165 ,m (range, 29,869 ,m); 86% being longer than 100 ,m and 35% longer than 200 ,m. Their breadth was 56 ,m (range, 6,255 ,m), but the thinnest were still in construction. Bridges were found in all nine subjects included in the study, suggesting that it is a common feature of normal vertebral bone remodeling. These observations support the hypothesis that perforation could be repaired by new bone formation. and hence, might not be systematically irreversible. [source]


Lasofoxifene (CP-336,156) Protects Against the Age-Related Changes in Bone Mass, Bone Strength, and Total Serum Cholesterol in Intact Aged Male Rats

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2001
Hua Zhu Ke
Abstract The purpose of this study was to evaluate if long-term (6 months) treatment with lasofoxifene (LAS), a new selective estrogen receptor modulator (SERM), can protect against age-related changes in bone mass and bone strength in intact aged male rats. Sprague-Dawley male rats at 15 months of age were treated (daily oral gavage) with either vehicle (n = 12) or LAS at 0.01 mg/kg per day (n = 12) or 0.1 mg/kg per day (n = 11) for 6 months. A group of 15 rats was necropsied at 15 months of age and served as basal controls. No significant change was found in body weight between basal and vehicle controls. However, an age-related increase in fat body mass (+42%) and decrease in lean body mass (,8.5%) was observed in controls. Compared with vehicle controls, LAS at both doses significantly decreased body weight and fat body mass but did not affect lean body mass. No significant difference was found in prostate wet weight among all groups. Total serum cholesterol was significantly decreased in all LAS-treated rats compared with both the basal and the vehicle controls. Both doses of LAS treatment completely prevented the age-related increase in serum osteocalcin. Peripheral quantitative computerized tomography (pQCT) analysis at the distal femoral metaphysis indicated that the age-related decrease in total density, trabecular density, and cortical thickness was completely prevented by treatment with LAS at 0.01 mg/kg per day or 0.1 mg/kg per day. Histomorphometric analysis of proximal tibial cancellous bone showed an age-related decrease in trabecular bone volume (TBV; ,46%), trabecular number (Tb.N), wall thickness (W.Th), mineral apposition rate, and bone formation rate-tissue area referent. Moreover, an age-related increase in trabecular separation (Tb.Sp) and eroded surface was observed. LAS at 0.01 mg/kg per day or 0.1 mg/kg per day completely prevented these age-related changes in bone mass, bone structure, and bone turnover. Similarly, the age-related decrease in TBV and trabecular thickness (Tb.Th) and the age-related increase in osteoclast number (Oc.N) and osteoclast surface (Oc.S) in the third lumbar vertebral cancellous bone were completely prevented by treatment with LAS at both doses. Further, LAS at both doses completely prevented the age-related decrease in ultimate strength (,47%) and stiffness (,37%) of the fifth lumbar vertebral body. These results show that treatment with LAS for 6 months in male rats completely prevents the age-related decreases in bone mass and bone strength by inhibiting the increased bone resorption and bone turnover associated with aging. Further, LAS reduced total serum cholesterol and did not affect the prostate weight in these rats. Our data support the potential use of a SERM for protecting against the age-related changes in bone and serum cholesterol in elderly men. [source]


Moderate Alcohol Consumption Suppresses Bone Turnover in Adult Female Rats

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 3 2001
R. T. Turner
Abstract Chronic alcohol abuse is a major risk factor for osteoporosis but the effects of moderate drinking on bone metabolism are largely uninvestigated. Here, we studied the long-term dose-response (0, 3, 6, 13, and 35% caloric intake) effects of alcohol on cancellous bone in the proximal tibia of 8-month-old female rats. After 4 months of treatment, all alcohol-consuming groups of rats had decreased bone turnover. The inhibitory effects of alcohol on bone formation were dose dependent. A reduction in osteoclast number occurred at the lowest level of consumption but there were no further reductions with higher levels of consumption. An imbalance between bone formation and bone resorption at higher levels of consumption of alcohol resulted in trabecular thinning. Our observations in rats raise the concern that moderate consumption of alcoholic beverages in humans may reduce bone turnover and potentially have detrimental effects on the skeleton. [source]


Effects of a New Selective Estrogen Receptor Modulator (MDL 103,323) on Cancellous and Cortical Bone in Ovariectomized Ewes: A Biochemical, Histomorphometric, and Densitometric Study

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 1 2001
Pascale Chavassieux
Abstract The aims of this study performed in ewes were: (1) to confirm in this animal model the effects on bone of ovariectomy (OVX) alone or associated with Lentaron (L), a potent peripheral aromatase inhibitor, used to amplify the effects of OVX and (2) to evaluate the effects of a new selective estrogen receptor modulator (SERM; MDL 103,323) on bone remodeling. Thirty-nine old ewes were divided into five groups: sham (n = 7); OVX (n = 8); OVX + L (n = 8); OVX + L + MDL; 0.1 mg/kg per day (n = 8); and OVX + L + MDL 1 mg/kg per day (n = 8). The animals were treated for 6 months. Biochemical markers of bone turnover (urinary excretion of type 1 collagen C-telopeptide [CTX], serum osteocalcin [OC], and bone alkaline phosphatase [BAP]) were measured each month. Bone biopsy specimens were taken at the beginning and after death at the end of the experiment. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) on the lumbar spine and femur. OVX induced a significant increase in biochemical markers. This effect was the highest after 3 months for CTX (+156% vs. sham) and after 4 months for OC and BAP (+74% and +53% vs. sham, respectively). L tended to amplify the effect of OVX on OC and BAP. OVX induced significant increases in the porosity, eroded, and osteoid surfaces in cortical bone but no effect was observed in cancellous bone. MDL treatment reduced the bone turnover as assessed by bone markers, which returned to sham levels as well as histomorphometry both in cortical and in cancellous bone. Cancellous osteoid thickness decreased by 27% (p < 0.05), mineralizing perimeter by 81% (p < 0.05), and activation frequency by 84% (p < 0.02) versus OVX + L. Femoral and spinal BMD were increased by MDL and tended to return to the sham values. The effects of OVX on bone turnover were different on cortical and cancellous bone. These effects on cortical bone were reflected by changes in biochemical markers. MDL markedly reduces bone turnover and increases BMD suggesting that this new agent may prevent postmenopausal bone loss. [source]


Quantitative Ultrasound Does Not Reflect Mechanically Induced Damage in Human Cancellous Bone

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 12 2000
P. H. F. Nicholson
Abstract This study investigated the ability of quantitative ultrasound (QUS) to detect reductions in the elastic modulus of cancellous bone caused by mechanical damage. Ultrasonic velocity and attenuation were measured using an in-house parametric imaging system in 46 cancellous bone cores from the human calcaneus. Each core was subjected to a mechanical testing regime to (a) determine the predamage elastic modulus, (b) induce damage by applying specified strains in excess of the yield strain, and (c) measure the postdamage elastic modulus. The specimens were divided into four groups: a control group subjected to a nominally nondestructive 0.7% maximum strain (,m) and three damage groups subjected to increasing strain levels (,m = 1.5, 3.0, and 4.5%). QUS measurements before and after the mechanical testing showed no significant differences between the control group and damage groups, despite highly significant (p < 0.001) reductions in the elastic modulus of up to 72%. These results indicate that current QUS techniques do not intrinsically reflect the elastic properties of cancellous bone. This is consistent with ultrasonic properties being determined by other factors (apparent density and/or architecture), which normally are associated strongly with elastic properties, but only when bone is mechanically intact. Clinically, this implies that ultrasound cannot be expected to detect bone fragility in the absence of major changes in bone density and/or trabecular architecture. [source]


Type V Osteogenesis Imperfecta: A New Form of Brittle Bone Disease,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2000
Francis H. Glorieux
Abstract Osteogenesis imperfecta (OI) is commonly subdivided into four clinical types. Among these, OI type IV clearly represents a heterogeneous group of disorders. Here we describe 7 OI patients (3 girls), who would typically be classified as having OI type IV but who can be distinguished from other type IV patients. We propose to call this disease entity OI type V. These children had a history of moderate to severe increased fragility of long bones and vertebral bodies. Four patients had experienced at least one episode of hyperplastic callus formation. The family history was positive for OI in 3 patients, with an autosomal dominant pattern of inheritance. All type V patients had limitations in the range of pronation/supination in one or both forearms, associated with a radiologically apparent calcification of the interosseous membrane. Three patients had anterior dislocation of the radial head. A radiodense metaphyseal band immediately adjacent to the growth plate was a constant feature in growing patients. Lumbar spine bone mineral density was low and similar to age-matched patients with OI type IV. None of the type V patients presented blue sclerae or dentinogenesis imperfecta, but ligamentous laxity was similar to that in patients with OI type IV. Levels of biochemical markers of bone metabolism generally were within the reference range, but serum alkaline phosphatase and urinary collagen type I N-telopeptide excretion increased markedly during periods of active hyperplastic callus formation. Qualitative histology of iliac biopsy specimens showed that lamellae were arranged in an irregular fashion or had a meshlike appearance. Quantitative histomorphometry revealed decreased amounts of cortical and cancellous bone, like in OI type IV. However, in contrast to OI type IV, parameters that reflect remodeling activation on cancellous bone were mostly normal in OI type V, while parameters reflecting bone formation processes in individual remodeling sites were clearly decreased. Mutation screening of the coding regions and exon/intron boundaries of both collagen type I genes did not reveal any mutations affecting glycine codons or splice sites. In conclusion, OI type V is a new form of autosomal dominant OI, which does not appear to be associated with collagen type I mutations. The genetic defect underlying this disease remains to be elucidated. [source]


Evaluation of processed bovine cancellous bone matrix seeded with syngenic osteoblasts in a critical size calvarial defect rat model

JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 3 2006
U. Kneser
Abstract Introduction: Biologic bone substitutes may offer alternatives to bone grafting procedures. The aim of this study was to evaluate a preformed bone substitute based on processed bovine cancellous bone (PBCB) with or without osteogenic cells in a critical size calvarial defect rat model. Methods: Discs of PBCB (Tutobone®) were seeded with second passage fibrin gel-immobilized syngenic osteoblasts (group A, n = 40). Cell-free matrices (group B, n = 28) and untreated defects (group C; n=28) served as controls. Specimens were explanted between day 0 and 4 months after implantation and were subjected to histological and morphometric evaluation. Results: At 1 month, bone formation was limited to small peripheral areas. At 2 and 4 months, significant bone formation, matrix resorption as well as integration of the implants was evident in groups A and B. In group C no significant regeneration of the defects was observed. Morphometric analysis did not disclose differences in bone formation in matrices from groups A and B. Carboxyfluorescine-Diacetate-Succinimidylester (CFDA) labeling demonstrated low survival rates of transplanted cells. Discussion: Osteoblasts seeded into PBCB matrix display a differentiated phenotype following a 14 days cell culture period. Lack of initial vascularization may explain the absence of added osteogenicity in constructs from group A in comparison to group B. PBCB is well integrated and represents even without osteogenic cells a promising biomaterial for reconstruction of critical size calvarial bone defects. [source]


Rodents as Taphonomic Agents: Bone Gnawing by Brown Rats and Gray Squirrels,

JOURNAL OF FORENSIC SCIENCES, Issue 4 2007
Walter E. Klippel Ph.D.
Abstract:, Passive infrared technology was used to film diurnal and nocturnal scavenging behavior of brown rats and gray squirrels at the University of Tennessee's Anthropological Research Facility. This direct documentation demonstrated that brown rats modified fat-laden cancellous bone while gray squirrels generally gnawed the thicker bone cortices only after fats had leached away. A case study placed in a shaded portion of the Facility indicated the postmortem interval for initial gnawing by gray squirrels was slightly over 30 months. An examination of 53 human skeletons in the William M. Bass Forensic Skeletal Collection revealed that 10 cases had gnaw marks consistent with those made by gray squirrels. One of the 10 cases had been gnawed within 16 months of time-since-death, while the remaining nine had postmortem intervals >30 months. Additional observed modifications made to nonhuman bone by gray squirrels indicate that squirrel gnaw marks on bone can serve as a minimal estimate of time-since-death in a temperate environment similar to that of East Tennessee. [source]


Primary hyperparathyroidism: new concepts in clinical, densitometric and biochemical features

JOURNAL OF INTERNAL MEDICINE, Issue 1 2005
J. P. BILEZIKIAN
Abstract. Primary hyperparathyroidism (PHPT) is characterized most commonly now as an asymptomatic disorder with hypercalcaemia and elevated levels of parathyroid hormone (PTH). The elevation in PTH is detected by both the standard immunoradiometric assays (IRMA) and a more recent IRMA that detects only the 1,84 full-length PTH molecule. The serum calcium concentration is usually <1 mg dL,1 above normal. Recently, another variant of PHPT (normocalcaemic PHPT) has been described in which the serum calcium is normal but the serum PTH is elevated, in the absence of any secondary cause for PTH elevation. Although usually sporadic, PHPT also occurs in inherited syndromes. Skeletal manifestations are appreciated by densitometry showing a typical pattern in which cancellous bone of the lumbar spine is reasonably well preserved whilst the cortical bone of the distal third of the radius is preferentially reduced. Although reduced in incidence, renal stones remain the most common overt complication of PHPT. Other organs are theoretical targets of PHPT such as the neurobehavioural axis and the cardiovascular system. Vitamin D looms as an important determinant of the activity of the PHPT state. The 2002 NIH Workshop on asymptomatic PHPT has led to revised guidelines to help doctors determine who is best advised to have parathyroid surgery and who can be safely followed without surgery. New information about the natural history of PHPT in those who did not undergo surgery has helped to define more precisely who is at-risk for complications. At the NIH workshop, a number of items were highlighted for further investigation such as pharmacological approaches to controlling hypercalcaemia, elevated PTH levels and maintaining bone density. [source]


Models of tibial fracture healing in normal and Nf1-deficient mice

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 8 2008
Aaron Schindeler
Abstract Delayed union and nonunion are common complications associated with tibial fractures, particularly in the distal tibia. Existing mouse tibial fracture models are typically closed and middiaphyseal, and thus poorly recapitulate the prevailing conditions following surgery on a human open distal tibial fracture. This report describes our development of two open tibial fracture models in the mouse, where the bone is broken either in the tibial midshaft (mid-diaphysis) or in the distal tibia. Fractures in the distal tibial model showed delayed repair compared to fractures in the tibial midshaft. These tibial fracture models were applied to both wild-type and Nf1-deficient (Nf1+/,) mice. Bone repair has been reported to be exceptionally problematic in human NF1 patients, and these patients can also spontaneously develop tibial nonunions (known as congenital pseudarthrosis of the tibia), which are recalcitrant to even vigorous intervention. pQCT analysis confirmed no fundamental differences in cortical or cancellous bone in Nf1 -deficient mouse tibiae compared to wild-type mice. Although no difference in bone healing was seen in the tibial midshaft fracture model, the healing of distal tibial fractures was found to be impaired in Nf1+/, mice. The histological features associated with nonunited Nf1+/, fractures were variable, but included delayed cartilage removal, disproportionate fibrous invasion, insufficient new bone anabolism, and excessive catabolism. These findings imply that the pathology of tibial pseudarthrosis in human NF1 is complex and likely to be multifactorial. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1053,1060, 2008 [source]


Repair of porcine articular cartilage defect with a biphasic osteochondral composite,

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 10 2007
Ching-Chuan Jiang
Abstract Autologous chondrocyte implantation (ACI) has been recently used to treat cartilage defects. Partly because of the success of mosaicplasty, a procedure that involves the implantation of native osteochondral plugs, it is of potential significance to consider the application of ACI in the form of biphasic osteochondral composites. To test the clinical applicability of such composite construct, we repaired osteochondral defect with ACI at low cell-seeding density on a biphasic scaffold, and combined graft harvest and implantation in a single surgery. We fabricated a biphasic cylindrical porous plug of DL-poly-lactide-co-glycolide, with its lower body impregnated with ,-tricalcium phosphate as the osseous phase. Osteochondral defects were surgically created at the weight-bearing surface of femoral condyles of Lee-Sung mini-pigs. Autologous chondrocytes isolated from the cartilage were seeded into the upper, chondral phase of the plug, which was inserted by press-fitting to fill the defect. Defects treated with cell-free plugs served as control. Outcome of repair was examined 6 months after surgery. In the osseous phase, the biomaterial retained in the center and cancellous bone formed in the periphery, integrating well with native subchondral bone with extensive remodeling, as depicted on X-ray roentgenography by higher radiolucency. In the chondral phase, collagen type II immunohistochemistry and Safranin O histological staining showed hyaline cartilage regeneration in the experimental group, whereas only fibrous tissue formed in the control group. On the International Cartilage Repair Society Scale, the experimental group had higher mean scores in surface, matrix, cell distribution, and cell viability than control, but was comparable with the control group in subchondral bone and mineralization. Tensile stress,relaxation behavior determined by uni-axial indentation test revealed similar creep property between the surface of the experimental specimen and native cartilage, but not the control specimen. Implanted autologous chondrocytes could survive and could yield hyaline-like cartilage in vivo in the biphasic biomaterial construct. Pre-seeding of osteogenic cells did not appear to be necessary to regenerate subchondral bone. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:1277,1290, 2007 [source]


Tissue response to polyglycolide, polydioxanone, polylevolactide, and metallic pins in cancellous bone: An experimental study on rabbits

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 8 2006
Harri Pihlajamäki
Abstract The purpose of this study was to investigate, qualitatively and histoquantitatively, the tissue response of rabbit femur cancellous bone to polyglycolide (PGA), polydioxanone (PDS), polylevolactide (PLLA), and stainless steel pins under identical conditions. Eighty knees in 50 rabbits were operated on by inserting bioabsorbable pins (PGA, PDS, or PLLA) together with metallic Kirschner wire in 60, and two metallic Kirschner wires alone in 20 knees, while 20 knees served as intact controls. Follow-up times were 3, 6, 12, 24, and 52 weeks. Cancellous bone tissue response to implants was studied using histological, histomorphometrical, microradiographical, and oxytetracycline fluorescence methods. Residual fragments of PGA and PDS were seen at 24 weeks. Complete degradation of these polymers had taken place before 52 weeks. No signs of degradation of the PLLA pins were observed within the entire follow-up period. The osteoid formation surfaces at tissue implant-interface were statistically larger in all test groups as compared to intact controls. The number of macrophages at tissue implant-interfaces increased in all bioabsorbable implant specimens until 6 weeks, and with PGA until 12 weeks. No differences in the osseous response emerged when comparing groups of bioabsorbable implants with each other or with stainless steel group. Bioabsorbable pins and metallic Kirschner wires evoked an osteoconductive response in the cancellous bone surrounding implant, but the response intensity between implants displayed no differences. This suggests a simple, nonspecific walling-off new-bone front type of response. Consequently, the polymers possessed no specific osteostimulatory or osteoinhibitory properties. Within the follow-up, no significant differences in biocompatibility between the implants appeared, and no frank inflammatory foreign-body reactions occurred. The small-volume pins obviously did not exceed the local tissue tolerance and clearing capacity of the bone. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1597,1606, 2006 [source]


Mechanical characteristics of the bone,graft,cement interface after impaction allografting

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 1 2005
Hanspeter Frei
Impaction allografting is an attractive procedure for the treatment of failed total hip replacements. The graft,cement,host bone interface after impaction allografting has not been characterized, although it is a potential site of subsidence for this type of revision total hip reconstruction. In six human cadaveric femurs, the cancellous bone was removed proximally and local diaphyseal lytic defects were simulated. After the impaction grafting procedure, the specimens were sectioned in 6 mm transverse sections and pushout tests were performed. From the adjacent sections the percentage cement contact of the PMMA cement with the endosteal bone surface was determined. The host bone interface mechanical properties varied significantly along the femur largely due to different interface morphologies. The apparent host bone interface shear strength was highest around the lesser trochanter and lowest around the tip of the stem. A significant positive correlation was found between the percentage cement contact and the apparent host bone interface shear strength (r2 = 0.52). The sections failed in 69% of the cases through a pure host bone interface failure without cement or allograft failure, 19% failed with local cement failure, and 12% with a local allograft failure. The apparent host bone interface strength was on average 89% lower than values reported for primary total hip replacements and were similar to cemented revisions proximally and lower distally. This study showed that cement penetration to the endosteal surface enhanced the host bone,graft interface. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source]


A histomorphological study of tendon reconstruction to a hydroxyapatite-coated implant: Regeneration of a neo-enthesis in vivo

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2004
C. J. Pendegrass
The attachment of tendons and ligaments to massive endoprostheses remains a clinical challenge due to the difficulty in achieving a soft tissue implant interface with a mechanical strength sufficient to transmit the forces necessary for locomotion. We have used an in vivo animal model to study patellar tendon attachment to an implant surface. The interface generated when the patellar tendon was attached to a hydroxyapatite (HA) coated implant was examined using light microscopy and a quantitative histomorphological analysis was performed. In the Autograft Group, the interface was augmented with autogenous cancellous bone and marrow graft, and at six weeks an indirect-like insertion was observed. At twelve weeks, the interface was observed to be a layered neo-enthesis, whose morphology was similar to a normal direct tendon insertion. In the HA Group, the tendon,implant interface was not augmented, and the implant was enveloped by a dense collagenous fibrous tissue. This study shows that a tendon,implant neo,enthesis can develop in situ by employing a suitable implant surface in association with biological augmentation. © 2004 Orthopaedic Research Society. Published y Elsevier Ltd. All rights reserved. [source]


Effect of freeze-drying and gamma irradiation on the mechanical properties of human cancellous bone

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2000
O. Cornu
Freeze-drying and gamma irradiation are commonly used for preservation and sterilization in bone banking. The cumulative effects of preparation and sterilization of cancellous graft material have not been adequately studied, despite the clinical importance of graft material in orthopaedic surgery. Taking benefit from the symmetry of the left and right femoral heads, the influence of lipid extraction followed by freeze-drying of a femoral head and a final 25-kGy gamma irradiation was determined, with the nonirradiated, nonprocessed counterpart as the control. Five hundred and fifty-six compression tests were performed (137 pairs for the first treatment and 141 pairs for the second). Mechanical tests were performed after 30 minutes of rehydration in saline solution. Freeze-dried femoral heads that had undergone lipid extraction experienced reductions of 18.9 and 20.2% in ultimate strength and stiffness, respectively. Unexpectedly, the work to failure did not decrease after this treatment. The addition of gamma irradiation resulted in a mean drop of 42.5% in ultimate strength. Stiffness of the processed bone was not modified by the final irradiation, with an insignificant drop of 24%, whereas work to failure was reduced by a mean of 71.8%. Freeze-dried bone was a bit less strong and stiff than its frozen control. Its work to failure was not reduced, due to more deformation in the nonlinear domain, and it was not brittle after 30 minutes of rehydration. Final irradiation of the freeze-dried bone weakened its mechanical resistance, namely by the loss of its capacity to absorb the energy (in a plastic way) and a subsequent greater brittleness. [source]


Evaluation and donor site morbidity of tibial bone graft in sinus lift operation

ORAL SURGERY, Issue 3 2008
S.L. Miranda
Abstract Aim:, The use of autologous bone is a good option for bone grafts in implantology. The purpose of this study was to present advantages in harvesting the proximal tibial cancellous bone as an alternative in the sinus floor lifting procedure, seeking future installation of osseointegraded implants. Materials and methods:, Between 2002 and 2006, 19 patients were attended, with age between 41 and 77, being 9 males and 10 females, in order to lift the maxillary sinus floor. The approach to the donor site was medial, because of the fact that this method brings minor risk of injury to anatomical structures. Results:, All cases allowed the installation of osseointegraded implants. Only minor complications occurred, such as local ecchymosis and ecchymosis extending to foot. In all cases, ambulation was immediate. Conclusions:, A good amount of bone could be harvested; scarce pain symptomatology was detected, and risk of complications could be considered very low in the donor site. [source]


A new high-resolution computed tomography (CT) segmentation method for trabecular bone architectural analysis

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2009
Heike Scherf
Abstract In the last decade, high-resolution computed tomography (CT) and microcomputed tomography (micro-CT) have been increasingly used in anthropological studies and as a complement to traditional histological techniques. This is due in large part to the ability of CT techniques to nondestructively extract three-dimensional representations of bone structures. Despite prior studies employing CT techniques, no completely reliable method of bone segmentation has been established. Accurate preprocessing of digital data is crucial for measurement accuracy, especially when subtle structures such as trabecular bone are investigated. The research presented here is a new, reproducible, accurate, and fully automated computerized segmentation method for high-resolution CT datasets of fossil and recent cancellous bone: the Ray Casting Algorithm (RCA). We compare this technique with commonly used methods of image thresholding (i.e., the half-maximum height protocol and the automatic, adaptive iterative thresholding procedure). While the quality of the input images is crucial for conventional image segmentation, the RCA method is robust regarding the signal to noise ratio, beam hardening, ring artifacts, and blurriness. Tests with data of extant and fossil material demonstrate the superior quality of RCA compared with conventional thresholding procedures, and emphasize the need for careful consideration of optimal CT scanning parameters. Am J Phys Anthropol 2009. © 2009 Wiley-Liss, Inc. [source]


A radiologic and histologic study of the os peroneum: Prevalence, morphology, and relationship to degenerative joint disease of the foot and ankle in a cadaveric sample

CLINICAL ANATOMY, Issue 6 2009
C. Muehleman
Abstract The present study investigated the prevalence of an os peroneum (OP, a sesamoid bone) in a cadaveric sample and its relationship to the shape of the cuboid tuberosity, and cartilage degeneration at the cuboid tuberosity and in regional joints within the foot (first metatarsophalangeal and calcaneocuboid) and ankle. The fibularis longus tendon of 33 embalmed human cadavers (mean age 81 years) were obtained from the anatomy laboratory. Nineteen of 64 tendons (30%) displayed an OP both radiographically and histologically. The os peronei ranged in size from small spicules to prominent masses: mean area 2.48 mm2 (left) and 2.70 mm2 (right). Histologically, the os peronei were cancellous bone, the largest occupying most of the tendon at the point of contact with the cuboid tuberosity. Fibrocartilage was present at their borders, merging with dense regular fibrous tissue and peritenon. The talocrural, calcaneocuboid, and first metatarsophalangeal joints were examined for cartilage integrity and osteophytes based on an earlier suggestion that there may be an association between degenerative joint disease and endochondral bone formation. There was no statistical correlation between presence of an OP with any of the following parameters: age, gender, body size, cartilage degeneration, or osteophytes within any of the joints examined. Therefore, the presence of an OP does not appear to be associated with increased endochondral ossification or degenerative joint disease. This study does not preclude the possibility that sesamoid bone formation may be associated with biomechanical functions within the foot; thus, future studies may be warranted. Clin. Anat. 22:747,754, 2009. © 2009 Wiley-Liss, Inc. [source]


The effect of three different calcium phosphate implant coatings on bone deposition and coating resorption: a long-term histological study in sheep

CLINICAL ORAL IMPLANTS RESEARCH, Issue 3 2005
Christian Schopper
Abstract: The present study investigated the hypothesis that hydroxyapatite (HA), tricalcium phosphate (TCP), and a HA-gel coated on endosseous titanium (Ti) implants by spark discharging (SD) and dip coating would achieve predictable osseointegration without evident bioresorption of the coatings on the long term. A costal sheep model was used for the implantation of the HA/SD, HA/TCP/SD, and HA-gel/SD specimens, which were retrieved 6 and 12 months following implantation. HA and Ti coatings on implants obtained by conventional plasma spraying (HA/PS, Ti/PS) were used as controls. Microscopy showed that osseointegration was achieved from all types of implants. No evidence for bioresorption of the HA/SD, HA/TCP/SD, and HA-gel/SD coatings was present but cohesive failure with disruption of the coating/implant interface was seen. A statistical analysis of the histomorphometrical data showed no time-dependent effect, however. HA/PS coatings achieved significantly higher bone,implant contact (BIC) percentages of the total implant surface (toBIC) than the other types of coatings (P=0.01). If the BIC percentages were traced separately for implant portions placed into cortical and cancellous bone (coBIC and caBIC, respectively), detailed analysis showed that the caBIC values of HA-gel/SD and HA/PS coatings were significantly higher than that of the other types of coatings (P=0.01). CaBIC values were highly correlated with toBIC values (P<0.001). The present study showed that the preparation techniques used produced thin, dense, and unresorbable coatings that achieved osseointegration. Compared with the control coatings, however, only HA-gel/SD coating can be recommended from the investigated preparation techniques for a future clinical use if a better coating cohesion is achieved. Résumé L'étude présente a étudié l'hypothèse que le recouvrement par de l'hydroxyapatite, du phosphate tricalcique et un gel d'hydroxyapatite sur les implants en titane par décharges spark et recouvrement par trempage pourrait apporter une ostéïntégration prévisible sans biorésorption importante des recouvrements à long terme. Un modèle de mouton a été utilisé pour l'implantation de spécimens HA/SD, HA/TCP/SD et gel-HA/SD qui ont été enlevés six et douze mois après leur insertion. Les implants recouverts d'hydroxyapatite et de titane obtenus par plasma-spray conventionnel (HA/PS et Ti/PS) ont été utilisés comme contrôles. La microscopie a montré que l'ostéoïntégration a été réalisée pour tous les types d'implants. Aucune évidence pour la biorésorption de HA/SD, HATCP/SD, et gel-HA/SD n'était présente mais un échec de cohésion avec destruction de l'interface implant/recouvrement a été mis en évidence. Une analyse statistique des données histomorphométriques ne montrait cependant aucun effet dépendant du temps. Les recouvrements HA/PS montraient des pourcentages de contact os/implant significativement plus importants de la surface implantaire totale (BIC) que les autres types de recouvrement (p=0,01). Lorsque les pourcentages de contact os-implant étaient lus séparément pour les portions implantaires placées dans l'os cortical ou l'os spongieux (respectivement coBIC et caBIC), l'analyse détaillée montrait que les valeurs caBIC du gel- HA/SD et des recouvrements HA/PS étaient significativement plus importants que dans les autres types de recouvrement (p<0,01). Les valeurs CaBIC étaient en relation étroite avec les valeurs toBIC (p<0,001). L'étude présente a montré que les techniques de préparation utilisées produisaient des recouvrements non-résorbables denses et fins qui permettaient l'ostéoïntégration. Cependant, comparé aux recouvrements contrôles, seul le recouvrement gel-HA/SD pouvait être recommandé avec les techniques de préparation étudiées pour une utilisation clinique future si une cohésion de recouvrement meilleure est assurée. Zusammenfassung Die vorliegende Studie untersuchte die Hypothese, dass Hydroxyapatit, Trikalziumphoshat und ein Hydroxyapatit-Gel als Beschichtung auf enossalen Ti-Implantaten zur voraussagbaren Osseointegration über einen langen Zeitraum ohne Bioresorption der Beschichtung führen. Die Beschichtungen wurden durch Funkenentladung und Tauchbeschichtung aufgetragen. Für die Implantation der HA/SD, HA/TCP/SD und HA-Gel/SD wurde ein Schafmodell verwendet. Die Proben wurden 6 und 12 Monate nach Implantation entnommen. Als Kontrolle dienten Hydroxyapatit- und Titanbeschichtungen (HA/PS und Ti/PS), welche mittels Plasmaspray aufgetragen worden waren. Die mikroskopische Untersuchung zeigte, das bei allen Implantattypen eine Osseointegration erreicht wurde. Bei den HA/SD, HA/TCP und HA-Gel/SD Beschichtungen waren keine Anzeichen von Bioresorption vorhanden, aber es konnten kohäsive Misserfolge mit Abrissen im Bereich der Implantat/Beschichtung-Berührungsfläche gesehen werden. Eine statistische Analyse der histomorphometrischen Daten zeigte jedoch keinen zeitabhängigen Effekt. Die HA/PS Beschichtungen erreichten signifikant höhere Knochen-Implantat-Kontakt Prozentwerte der gesamten Implantatoberfläche (toBIC) als die anderen Beschichtungen (P=0.01). Wenn die Knochen-Implantat-Kontakt Prozentwerte für Implantatbereiche, welche im kortikalen und spongiösen Knochen (coBIC und caBIC) lagen, separat ausgemessen wurden, so zeigte die detaillierte Analyse, dass die caBIC Werte von HA-Gel/SD und HA/PS Beschichtungen signifikant höher waren als bei allen anderen Typen von Beschichtungen (P=0.01). Die caBIC Werte zeigten eine starke Korrelation mit den toBIC Werten (P<0.001). Die Studie zeigte, dass das verwendete Herstellungsverfahren dünne, dichte und nicht resorbierbare Beschichtungen ergab, welche eine Osseointegration erreichten. Im Vergleich mit den Kontrollbeschichtungen können jedoch nur die HA-Gel/SD Beschichtungen der untersuchten Herstellungsverfahren für den weiteren klinischen Gebrauch empfohlen werden, falls eine bessere Kohäsion der Beschichtung erreicht werden kann. Resumen El presente estudio investigó la hipótesis de que la hidroxiapatita, el fosfato tricálcico y un gel de hidroxiapatita cubriendo implantes endoóseos de Ti por medio de chisporroteo e inmersión pueden lograr una osteointegración predecible sin una biorreabsorción evidente de las cubiertas a largo plazo. Se usó un modelo costal de oveja para la implantación de especímenes HA/SD, HA/TCP/SD, y gel-HA/SD que se retiraron a los 6 y a los 12 meses de la implantación. Como control se usaron cubiertas de hidroxiapatita y titanio en implantes obtenidos por medio de pulverización de plasma convencional (HA/SD, Ti/PS). La microscopía demostró que la osteointegración se logró en todos los tipos de implantes. No existió evidencia de biorreabsorción de las cubiertas HA/SD, HA/TCP/SD, y gel-HA/SD pero se observó fallos en la cohesión con disrupción de la interfase cubierta/implante. Un análisis estadístico de los datos histomorfométricos no mostró, sin embargo efectos dependientes del tiempo. Las cubiertas HA/PS lograron unos porcentajes de contacto hueso-implante significativamente mayores del total de la superficie del implante (toBIC) que los otros tipos de cubiertas (P=0.01). Si se ubicaran los porcentajes de contacto hueso-implante separadamente para porciones situadas dentro de hueso cortical o esponjoso (coBIC y caBIC respectivamente), un análisis detallado mostró que los valores caBIC de las cubiertas de HA-gel/SD y HA/PS fueron significativamente mayores que aquellos de los otros tipos de cubiertas (P<0.001). El presente estudio mostró que las técnicas de preparación usadas produjeron cubiertas finas, densas y no reabsorbibles que alcanzaron la osteointegración. De todos modos, comparadas con las cubiertas de control, solo la cubierta HA-gel/SD pude ser recomendada desde las técnicas de preparación investigadas para un futuro uso clínico si se lograse una mejor cohesión de cubierta. [source]