Cancellous Region Research Articles

Verifying Workflows with Cancellation Regions and OR-joins: An Approach Based on Relaxed Soundness and Invariants

YAWL (Yet Another Workflow Language) workflow language supports the most frequent control-flow patterns found in the current workflow practice. As a result, most workflow languages can be mapped onto YAWL without the loss of control-flow details, even languages allowing for advanced constructs such as cancellation regions and OR-joins. Hence, a verification approach for YAWL is desirable, because such an approach could be used for any workflow language that can be mapped onto YAWL. Unfortunately, cancellation regions and OR-joins are ‘non-local’ properties, and in general we cannot even decide whether the desired final state is reachable if both patterns are present. This paper proposes a verification approach based on (i) an abstraction of the OR-join semantics; (ii) the relaxed soundness property; and (iii) transition invariants. This approach is correct (errors reported are really errors), but not necessarily complete (not every error might get reported). This incompleteness can be explained because, on the one hand, the approach abstracts from the OR-join semantics and on the other hand, it may use only transition invariants, which are structural properties. Nevertheless, our approach can be used to successfully detect errors in YAWL models. Moreover, the approach can be easily transferred to other workflow languages allowing for advanced constructs such as cancellations and OR-joins.

Selective Cyclooxygenase‐2 Inhibitor May Impair Bone Healing Around Titanium Implants in Rats

The aim of this study was to investigate the effect of a selective cyclooxygenase-2 inhibitor, meloxicam, on bone healing around titanium implants in rats. Thirty-one adult male Wistar rats were included in this study, and one screw-shaped titanium implant was inserted in the tibiae of each rat. The animals were randomly assigned to one of the following groups for daily subcutaneous injections: control (N = 14): saline solution; and test (N = 17): 3 mg/kg of meloxicam, each administered daily for 60 days. After the treatment, animals were sacrificed, and undecalcified sections were obtained. Bone-to-implant contact (BIC) and bone area (BA) within the limits of implant threads and bone density (BD) in a 500 mum-wide zone lateral to the implants were obtained and arranged for cortical (zone A) and cancellous (zone B) bone regions. Intergroup comparisons demonstrated that meloxicam significantly reduced bone healing around implants. For zone A, significant differences were observed regarding BIC (47.01 +/- 10.48 A; 35.93 +/- 12.25 B), BA (86.42 +/- 3.66 A; 61.58 +/- 12.09 B), and BD (96.86 +/- 0.96 A; 91.06 +/- 3.05 B) for control and test groups, respectively (P <0.05). For zone B, data analysis also showed significant differences among groups for BIC (30.76 +/- 13.80 A; 16.86 +/- 11.48 B), BA (34.83 +/- 8.18 A; 25.66 +/- 9.16 B), and BD (15.76 +/- 7.05 A; 7.73 +/- 4.61 B) for control and test groups, respectively (P <0.05). Meloxicam may negatively influence bone healing in the cortical and cancellous bone around titanium implants inserted in rats after continuous administration.

Radiographic assessment of bone density around integrated titanium implants after ovariectomy in rats

This study evaluated the influence of ovariectomy 8 weeks after implant placement on bone integrated to titanium implants. Thirty-eight female rats were submitted to a titanium implant at the tibiae proximal methaphysis. After a healing period of 8 weeks the animals were randomly divided into three groups: control (CTL-10 animals), sham-operated (SHAM-14 animals) and ovariectomy (OVX-14 animals). The CTL group was then sacrificed in order to confirm integration of the implant. The SHAM group was submitted to fictitious surgery and the OVX group was submitted to bilateral ovariectomy. After 12 weeks post-implant placement, the SHAM and OVX groups were sacrificed. In order to confirm the systemic osteopenia in rats, a dual-energy X-ray absorptiometry (DXA) was performed. For the evaluation of bone density, digital radiographs were taken. The grey level of the bone adjacent to implant was measured using image software and the bone density was calculated at six points on both sides of the implant. Densitometry measurements of the femur confirmed systemic bone mass loss in the OVX group. Individualized bone analyses of different regions surrounding the implant showed a significantly lower radiographic bone density (P < 0.05) in the cancellous region of the OVX group (77.48 +/- 23.39 grey levels) when compared with the CTL and SHAM groups (91.61 +/- 32.10 and 102.57 +/- 32.50 grey levels, respectively). The present study showed a decrease of the radiographic bone density in the cancellous region of bone around titanium implants placed 8 weeks before ovariectomy in rats.

Age‐Related and Surgically Induced Estrogen Deficiencies May Differently Affect Bone Around Titanium Implants in Rats

Valuable information has been obtained using the ovariectomy model; however, clinical studies have indicated that such a model may not be appropriate to parallel with the postmenopausal condition and titanium implants. Thus, this study aimed to comparatively evaluate, by histometric analysis, the influence of age-related (ARED) and surgically induced (OVX) estrogen deficiencies on bone around titanium implants inserted in rats. Single screw-shaped titanium implants were placed in rat tibiae and animals were then assigned to one of the following groups: SHAM (N = 15): bilateral sham ovariectomies in 90-day-old rats, 21 days before implant placement; OVX (N = 15): bilateral ovariectomies in 90-day-old rats, 21 days before implant placement; and ARED (N = 15): implant placement in reproductive aged rats (22 months old). After 60 days, the animals were sacrificed and undecalcified sections obtained. Bone-to-implant contact (BIC) and bone area (BA) within the limits of implant threads and bone density (BD) in a 500 microm-wide zone lateral to the implant were obtained and arranged for cortical (zone A) and cancellous (zone B) bone regions. For zone A, intergroup analysis showed no significant differences regarding BIC and BA (P >0.05). In contrast, ARED negatively influenced BD around the implants (P <0.05). In zone B, OVX negatively affected BIC and BA (P <0.05), and both ARED and OVX groups demonstrated lower BD than the SHAM group (P <0.05). Within the limits of this study, it can be concluded that ARED mainly affects preexisting bone while OVX more significantly affects both newly formed and preexisting bone.

1209 転倒時の衝撃吸収を目的としたセル状ヒップパッドの開発(OS12 バイオメカニクカルデザインIII)

Recently, hip pads have been developed to prevent the femur fracture by falling for aged persons. It is necessary for hip pads that the material and the structure select and design to realize the higher performance of impact absorption. In this work, an experimental system was made to test the impact absorbing properties of hip pad with cellular cushion and commercial hip pad. Using an artificial femur with composite materials that consist of cortical and cancellous region, impact load was applied to greater trochanter of the femoral model. Impact absorbing performance was evaluated by the impulsive force, collision time and impact strain. As a result, significant differences were not showed about absorbing performance in hip pad with cellular cushion except 12mm thickness.

Alendronate Therapy May Be Effective in the Prevention of Bone Loss Around Titanium Implants Inserted in Estrogen‐Deficient Rats

This study evaluated whether alendronate (ALD) influences bone healing around titanium implants inserted in ovariectomized rats and whether it provides a residual effect after its withdrawal. Bilateral ovariectomies were performed in 87 Wistar rats and one screw-shaped titanium implant was placed in the tibiae. The animals were divided into the following groups: group SHAM (N = 15): sham surgeries; group OVX (N = 15): ovariectomy; group AT (N = 15): OVX plus alendronate administration for 80 days; group AW (N = 14): OVX plus alendronate administration for 40 days; group ET (N = 14): OVX plus 17beta estradiol administration for 80 days; or group EW (N = 14): OVX plus 17beta estradiol administration for 40 days. Bone-to-implant contact (BIC), bone area (BA) within the limits of implant threads, and bone density in a 500 microm-wide zone lateral to the implant (BD) were obtained and measured for the cortical (zone A) and cancellous (zone B) regions. In zone A, data analysis showed no significant differences among the groups regarding BIC and BD (P >0.05), and a slight beneficial effect of estradiol on BA when compared with the OVX, EW, and AW groups (P <0.05). In zone B, OVX negatively impacted bone healing around the implants, resulting in reduced BA and BD (P<0.05). ALD (continuous/interrupted) and estradiol (only continuous) positively affected BIC, BA, and BD, resulting in values at the same level as the control group (SHAM). ALD may prevent the negative influence of estrogen deficiency on bone healing around titanium implants inserted in OVX rats. This positive effect, in contrast to estradiol, is sustained following its withdrawal.

1224 海綿骨再形成過程における微視組織構造の観察(G02-3 骨梁構造とリモデリング,G02 バイオエンジニアリング)

Regeneration and remodeling processes of trabecular bone structure in cancellous bone defects are affected by various factors. Basic understanding of the bone regeneration mechanism will help us to design artificial joints, implants and scaffold microstructure for bone tissue regeneration. In this study, artificial defect was created in cancellous bone region of a rat distal femur, and a formation mechanism of trabecular structure in the defect was evaluated using X-ray μCT and microscopy. As a result, it was revealed that the directionality of defect did not directly influence on the formation of bone structure, while the defect shape have remarkable influence on the bone matrix formation.

Vascular perfusion of the long dorsal arm versus chevron osteotomy: A cadaveric injection study

Iatrogenic disruption of the first metatarsal head’s blood supply after a distal osteotomy may lead to adverse events such as delayed union or avascular necrosis of the capital fragment. In this cadaveric study, 2 types of distal first metatarsal osteotomies were performed on 7 fresh-frozen specimens (long dorsal arm osteotomy, N = 4; chevron osteotomy, N = 3). For each specimen, the respective osteotomy was created. The dorsalis pedis artery was cannulated at the midfoot level and infiltrated with methylene blue dye until resistance was felt. The nutrient artery to the first metatarsal shaft was then exposed and the capital fragment was dissected free from the remaining soft tissues and visually inspected for the presence and distribution of dye. One of the chevron specimens was excluded because of technical error during the injection portion of the study. In all 4 of the long dorsal arm specimens, dye was observed in the entire dorsal cortical-cancellous wing and the cancellous metatarsal head region. In contrast, dye was completely absent in the capital fragment of the 2 chevron specimens. This cadaveric study showed that the vascular supply to the long dorsal arm osteotomy includes the nutrient artery, whereas the chevron osteotomy does not. This suggests that the long dorsal arm osteotomy may present a less risk of vascular compromise to the capital fragment.

Estrogen deficiency affects bone healing around titanium implants: a histometric study in rats.

The purpose of this study was to evaluate the influence of an estrogen-deficient state on bone around titanium implants placed in rats. Thirty female Wistar rats were divided into 2 groups: test (n = 15), ovariectomized rats (OVX); and control (n = 15), sham-operated rats. Screw-type titanium implants were placed bilaterally in rats 21 days after ovariectomy or sham surgery. After 60 days, the animals were killed and undecalcified sections obtained. Blood samples were collected to obtain serum levels of alkaline phosphatase at the time of killing. Bone-to-implant contact (BIC), bone area (BA) around the implants, and bone density (BD) in a 500 microns-wide zone lateral to the implant were obtained and arranged separately for the cortical (zone A) and cancellous (zone B) regions. In zone A, there was no significant difference between test and control groups regarding BIC and BD (P > 0.05). A lower BA was observed in the estrogen-deficient animals (P < 0.05). In zone B, data analysis showed that estrogen deficiency could result in a lower percentage of BIC, BA, and BD (P < 0.05). In addition, a higher concentration of alkaline phosphatase was observed for the test group. An estrogen-deficient state could affect bone healing and bone density around titanium implants placed in rats, especially in the cancellous bone area.

A rat resistance exercise regimen attenuates losses of musculoskeletal mass during hindlimb suspension.

Exposure to microgravity and/or spaceflight causes dramatic losses in both muscle and bone mass. In normal gravity, resistance exercise has been effectively used to increase muscle and bone mass. We tested a novel form of resistance exercise training using flywheel technology as a countermeasure to offset the loss of musculoskeletal mass during 4 weeks of adult rat hindlimb suspension (HS), an unloading model of microgravity. Male, Sprague-Dawley rats (6-month old) were operantly conditioned to perform resistance exercise, and then randomly assigned to groups of sedentary control (CON), HS, and HS with resistance exercise training (HSRT; 2 sets of approximately 21 repetitions, 3 days week(-1) for 4 weeks during suspension). In soleus, HS resulted in lower (P < 0.05) muscle mass to body mass ratio (approximately 50% of controls) and rates of protein synthesis. HSRT significantly attenuated the loss of muscle mass in soleus muscle, and rates of protein synthesis for soleus were similar for HSRT and controls. There were no differences among groups for mass or rates of protein synthesis in extensor digitorum longus. In cancellous regions of the distal femur, HS resulted in significant reductions of bone mineral density (BMD), but this was restored to control levels with HSRT. Cortical regions of the femur were not different among HS, HSRT or control groups. Together, these data suggest that resistance training using flywheel technology may be a promising tool to attenuate losses of the musculoskeletal system during periods of hindlimb unloading.

Skeletal dosimetry via NMR microscopy: investigations of sample reproducibility and signal source.

Nuclear magnetic resonance microscopy has been used for several years as a means of quantifying the 3D microarchitecture of the cancellous regions of the skeleton. These studies were originally undertaken for the purpose of developing non-invasive techniques for the early detection of osteoporosis and other bone structural changes. Recently, nuclear magnetic resonance microscopy has also been used to acquire this same 3D data for the purpose of both (1) generating chord length data across bone trabeculae and marrow cavities and (2) generating 3D images for direct coupling to Monte Carlo radiation transport codes. In both cases, one is interested in the reproducibility of the dosimetric data obtained from nuclear magnetic resonance microscopy. In the first of two studies, a trabecular bone sample from the femoral head of a 51-y-old male cadaver was subjected to repeated image acquisition, image processing, image coupling, and radiation transport simulations. The resulting absorbed fractions at high electron energies (4 MeV) were shown to vary less than 4% among four different imaging sessions of the same sample. In a separate study, two femoral head samples were imaged under differing conditions of the NMR signal source. In the first case, the samples were imaged with intact marrow. These samples were then subjected to marrow digestion and immersed in Gd-doped water, which then filled the marrow cavities. Energy-dependent absorbed fraction profiles for both the marrow-intact and marrow-free samples showed essentially equivalent results. These studies thus provide encouragement that skeletal dosimetry models of improved patient specificity can be achieved via NMR microscopy in vivo.

Pediatric Reference Data for Dual X-Ray Absorptiometric Measures of Normal Bone Density in the Distal Femur

Many children at risk for osteoporosis have substantial hip and knee contractures that prevent assessment of bone mineral density in the "usual" region, the proximal femur. As an alternative, bone density may be measured in the distal femur projected in the lateral plane. The purpose of this study was to provide normative reference data useful for interpretation of bone density measures in the distal femur of children and adolescents. The study was a cross-sectional, single-observational assessment of 256 healthy children and adolescents between the ages of 3 years and 18 years 6 months (mean, 10 years 5 months). Bone mineral density was measured in the nondominant proximal femur, lumbar spine, and both distal femurs using dual X-ray absorptiometry. We found that bone mineral density increases with age in the cortical, cancellous, and mixed regions of the distal femur, similar to the findings with other regional analyses of bone density. Bone density in the distal femur correlates very highly with bone density in the proximal femur and slightly less well with bone density in the lumbar spine. In pediatric patients who have deformities, have experienced trauma, or have undergone surgical procedures that prevent reliable measures of bone density in the proximal femur, bone mineral density may be measured in the distal femur and interpreted relative to the bone mineral density findings in healthy age- and sex-matched controls.

Slepton flavor nonuniversality, the muon electric dipole moment, and its proposed sensitive search at Brookhaven

We analyze the electric dipole moment of the electron ${(d}_{e}),$ of the neutron ${(d}_{n}),$ and of the muon ${(d}_{\ensuremath{\mu}}),$ using the cancellation mechanism in the presence of nonuniversalities of the soft breaking parameters. It is shown that the nonuniversalities in the slepton sector produce a strong violation of the scaling relation ${d}_{\ensuremath{\mu}}{/d}_{e}\ensuremath{\simeq}{m}_{\ensuremath{\mu}}{/m}_{e}$ in the cancellation region. An analysis of ${d}_{e},$ ${d}_{n},$ and ${d}_{\ensuremath{\mu}}$ under the constraints of the current experimental limits on ${d}_{e}$ and ${d}_{n},$ and under the constraints of the recent Brookhaven result on ${g}_{\ensuremath{\mu}}\ensuremath{-}2,$ shows that in the nonscaling region, ${d}_{\ensuremath{\mu}}$ can be as large as ${(10}^{\ensuremath{-}24}\ensuremath{-}{10}^{\ensuremath{-}23})e\mathrm{cm}$ and thus within reach of the recently proposed Brookhaven experiment for a sensitive search for ${d}_{\ensuremath{\mu}}$ at the level of ${10}^{\ensuremath{-}24}e\mathrm{cm}.$

Linear correlation between axial and lateral bone mineral density of lumbar vertebrae.

The placement of most spinal interbody devices is above the cancellous region of the vertebral bodies. Dual X-ray absorptiometry (DXA) scans of patients are usually taken from the anterior-posterior or the lateral projection. DXA scans taken in vitro from the axial direction would most closely indicate the bone mineral density (BMD) of the bone at this region. So far, in vitro studies have not been conducted to determine the correlation between axial and lateral scans. Because lateral DXA BMD scans are noninvasive and have low radiation dosage, they could be used as a predictive tool to determine the quality of cancellous bone at the centrum of the vertebral bodies, where spinal interbody devices are commonly placed.

Complementary information on bone ultrastructure from scanning small angle X-ray scattering and Fourier-transform infrared microspectroscopy

Scanning small angle X-ray scattering (scanning SAXS) and Fourier-transform infrared microspectroscopy (FT-IRM) have previously been utilized independently to characterize the structural properties of bone in an anatomical position-resolved fashion. Whereas SAXS provides a direct measure of the physical characteristics of apatitic crystals, FT-IRM assesses structure of both mineral and organic matrix at the molecular level. In the present study both methods were applied to examine the same developing bone tissue from the L-4 vertebra of a 14-month-old (accidental death). A 200-μm-thick section was processed for examination by scanning electron microscopy and SAXS. Spectra were collected at 200 μm spatial resolution at specific locations in cortical and cancellous bone. Parameters determined included total SAXS intensity, crystal thickness ( T), and degree and direction of predominant crystal orientation. For FT-IRM analysis, a section 4 μm thick was cut longitudinally from the top of the sample. Spectra of regions 100 × 100 μm 2 were acquired from the same locations as the SAXS spectra. Integrated areas of the phosphate ν 1,3 collagen amide I, and carbonate ν 2 absorbances, were calculated to obtain mineral:matrix and carbonate:mineral ratios. The relative quantities of types A, B, and labile carbonate (substituted for apatite hydroxyl, phosphate, and surface positions, respectively) were also evaluated. Polarized FT-IRM data were collected to determine molecular orientation of the apatite and collagen components. The results of this study show that the information obtained from the two techniques is complementary. Both SAXS and FT-IRM data revealed that the crystals were significantly larger in the cancellous region compared with the cortical region, that mineralization was greater in the cortex, and that the crystals were oriented to a larger degree in the cancellous compared with the cortical bone. The scanning SAXS measure of crystal thickness was significantly correlated to the FT-IRM measures of crystallinity, type A carbonate substitution, and crystal orientation. In conclusion, it was found that the combined use of SAXS and FT-IRM provides valuable, unique information on structural changes in bone at both the microstructural and ultrastructural level. Although each method can be used individually, the combination of techniques provides additional insights into the mechanism of bone crystal maturation.

Glenoid bone architecture

This article describes regional variations in trabecular bone architecture in terms of density and orientation within six glenoid specimens. The mean donor age was 56 years and ranged from 31 to 72 years. An automated imaging technique based on 3-dimensional serial sectioning was used for the direct examination of the glenoid cancellous bone structures. Subchondral plate thickness was on average 1.9 mm and ranged from 1.2 mm to 2.9 mm. The volume fraction of trabecular bone varied from 11% to 45% with peak values at the posterior glenoid vault. On graphic 3-dimensional reconstructions, the glenoid appeared as platelike trabeculae, radially oriented perpendicular to the subchondral plate and interconnected by thin rods. These views also displayed regional variations throughout the glenoid, reflecting differences in the macroscopic appearance. Quantitative structural analysis revealed different degrees of anisotropy at the glenoid cancellous region, predominantly transverse isotropy. Resemblance to direct weight-bearing cancellous bone such as the proximal tibia was evident.

Maintenance of bone mineral density of femoral cortex in ovariectomized rats after withdrawal of concurrent administration of human parathyroid hormone (1–34) and incardronate disodium (YM175)

The aim of this study was to evaluate the potential use of a combination of human parathyroid hormone (1–34) [hPTH(1–34)] and bisphosphonate (incadronate disodium cycloheptylaminomethylenedisphosphonate monohydrate, YM175) as a therapy for osteoporosis. We examined the effects of concurrent administration of PTH and YM175 or single administration and the persistence of their therapeutic effect after withdrawal on bone mineral density (BMD) of the femur in ovariectomized rats with established osteopenia. One hundred and two 11-week-old Sprague-Dawley rats were divided into sham operation and ovariectomy (OVX) groups. OVX rats were untreated for the first 4 weeks post ovariectomy to allow for the development of moderate ovariectomy to allow for the development of moderate osteopenia. These animals were then subjected to various treatment regimens with either PTH, YM175, or both for 4 weeks. The animals were then killed at 4 or 12 weeks, after withdrawal of the treatment and the bone mineral density (BMD) of distal, middle, proximal part, and total area of the femur were determined by dual-energy X-ray absorptiometry (DXA). In the distal femur (cancellous bone-rich region), treatment with YM failed to restore BMD in OVX rats, while treatment with PTH alone (P<.01) or PTH + YM175 (P<.01) reversed BMD in OVX rats after 4 weeks of treatments. The restored distal BMD by PTH or PTH + YM175 treatments could be maintained thereafter until 12 weeks withdrawal. In midshaft of the femur (cortical bone-rich region), treatment with PTH (P<.05), YM175 (P<.05), and PTH + YM175 (P<.01) all could increase BMD after 4 weeks of treatments in the OVX rats, but only concurrent treatment with PTH + YM175 maintained the BMD of femoral midshaft for 12 weeks after withdrawal of the treatment. These results suggest that (1) concurrent treatment with PTH and YM175 could result in a bone gain not only in cancellous bone but also in cortical bone of the femur, and (2) the restored BMD could be maintained for 12 weeks after cessation of the treatment in cortical bone only by concurrent use of PTH + YM175 in immature ovariectomized rats

Predictive value of proximal femoral bone densitometry in determining local orthogonal material properties

Models which are based on non-invasive bone measurements may in the future be able to successfully identify individual subjects at an increased risk for hip fracture; thus, we designed a study to determine the usefulness of dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) in predicting the local material properties of human proximal femoral cancellous bone. There has been some disagreement in the scientific literature regarding appropriate predictive models for local material properties of cancellous bone. We sought to confirm that density-mechanical property relationships were consistent from subject to subject, and that three-dimensional QCT measurements were stronger predictors of mechanical properties than two-dimensional DXA results. Linear and power fit relationships between these densitometric measures and material properties were also examined to determine which were more appropriate. Bone cubes from specific regions of highly oriented trabeculae were analyzed separately to determine if cube orientation had an effect on mechanical properties independent of bone density. Ten pairs of ex vivo femurs (five male, five female; age 30–93, mean age 62) were prepared such that specific anatomic planes were visible radiographically. Both QCT and DXA measurements were made on all 20 femurs. Cancellous bone cubes were obtained proceeding along two distinct directions from the proximal end of each femur pair. Unexpectedly, the density-modulus relationships among these ten donors were found to be significantly different at p < 0.01 (83% of the tests were different at p < 0.0001). Density-strength regressions were also significantly different at p < 0.01, but this effect was not as consistent nor as statistically significant. In general, the QCT method did not produce predictions of local cancellous bone material properties superior to the DXA method. The linear and power fit models appeared to produce consistent results, with neither being obviously more advantageous. These density measurements explained at best 30–40% of the variance in modulus and 50–60% of the variance in ultimate stress. The orientation of cancellous cubes in the principal compressive trabeculae region was a significant contributor to mechanical properties ( p = 0.0001) independent of bone density. This finding was not as dramatic in the femoral neck cancellous bone region.

Effects of tiludronate on bone loss in the cancellous and cortical regions of Tibia in rats fed with a low calcium diet

CANCELLOUS AND CORTICAL REGIONS OF TIBIA IN RATS FED WITH A LOW CALCR]M DLET K. Aoki. t I-L Sere, t l'L Murakami, 2 M. Abe, 2 A. Barbier, 3 K. Ohya. t 'Department of Dental Pharmacology, Tokyo Medical and Dental University, Tokyo, Japan. ~Pharmaceutieal Research Center Mciji Selka Kaisya Ltd., Yokohama, J'apan. SDepartment o f General Pharmacology, Sanofl Recherche, Montpdlier, France. Pj, trp_ osr of the study~ To evaluate how bisphosphonstes influenCe the process of bone resorption. In one experimental model for bone resorption induced by a low calcium diet in rats, bone resorption develops rapidly wi'hout affecting the growth rate. We examined the effects of disodium (4chlorophenyhhio) methylene bispbosphonate (tihidronate) in this model. Twenty 6-wnek old, male Wistar rats were assigned to 4 groups: group 1 was fed a control diet (0.5% calcium) and groups 2 to 4 were fed a low calcium diet (0.05% calcium). Phosphate content was 0.35% in both diets. All r~,ts were given subcutaneous injections for 6 days: groups 1 and 2 received vehicle alone, group 3 received 5 mgCkg/day tiludronate and group 4 had 10 mg/kg/day tiludronat=, Result: Serum levds of total and ionized calcium were normocalcemic in groups 1 and 2, but were hypocalcaemic in groups 3 and 4. Bone mineral density (BMD) in the tibia, measured by dual energy X-ray absorptiometry, decreased significandy is group 2 compared with group 1. Tiludronatr inhibited the decrease in BMD in the cancellous regions in groups 3 and 4, but did not appear to inhibit the decrease in the BMD of cortical regions. Conclusions: The regional variations in the decrease in BMD after treatment with tiludtonate might be caused by the differences in bone turnover o f cortical bone and o f trabocular bone. It seemed that the experimental period in this study was too short to observe the efficacy oftiludronate on cortical bone. Investigation should consider the regional differences in the response of bone to tiludronate during examination of the pharmacological actions of this drug.

Cancellous bone Young's modulus variation within the vertebral body of a ligamentous lumbar spine--application of bone adaptive remodeling concepts.

Bone remodeling theory based on strain energy density (SED) as the feedback control variable was used in conjunction with the finite element method to analyze the shape of the vertebral bodies within the ligamentous motion segment. The remodeling theory was once again applied to the altered two motion segments model to predict the Young's modulus distribution of the cancellous bone within the vertebral bodies. A three-dimensional finite element model of the two motion segments ligamentous lumbar spine (L3-5) was developed. Bone remodeling response (external as well as internal) of the motion segments to a uniaxial compressive load of 424.7 N was studied. The external shape of the converged model matched the normal shape of a vertebral body. The internal remodeling resulted in regional cancellous bone Young's moduli (or bone density) distributions similar to those reported in the literature; posterocentral regions of the vertebrae were predicted to have greater values of the elastic modulus than that of the outer regions. The results of the present study suggest that vertebral body assumes an adequate/optimum structure in terms of both its shape and its elastic moduli distribution within the cancellous region in response to the applied load. Extensions of the present model and its clinically relevant applications are discussed.