Cortical Bone Width Research Articles

Cortical Bone Width in Juvenile Race Horses Treated with Exogenous Somatotropin

In this study, effects of exogenous somatotropin (eST) on cortical bone width were evaluated in a group of juvenile horses in race training. Radiographs of the third metacarpal from 31 juvenile race horses were obtained from a previous study (19). The horses had been paired by age and sex and randomly assigned to treatment with daily injections of eST (n = 16) or saline (n = 15). Radiographs were measured for total bone diameter and cortical bone width at three sites using a digital micrometer. Average total bone diameter in the dorsal-palmar plane on d 0 was 30.701mm at Site A, 31.331mm at Site B, and 31.071mm at Site C. There was no significant change in bone diameter on d 64 of the treatment period. By d 128, there was an increase (P < 0.05) in bone diameter in the dorsal-palmar plane at all three sites and in the lateral-medial plane at Sites B and C. The eST-treated horses had a significantly greater increase in dorsal-palmar bone diameter at all three sites on d 128 than the control horses (P < 0.05), but treatment did not affect lateral-medial bone diameter. There was a decrease (P < 0.0001) in medullary cavity width in the dorsal-palmar plane but no change in the lateral-medial direction. At d 64, there was a greater decrease in medullary cavity width (dorsal-palmar) at Site B (P < 0.02) in the eST-treated group than in the control group. By d 128, the eST-treated horses had a greater decrease in medullary cavity width (dorsal-palmar) at both Site B (P < 0.01) and Site C (P < 0.02) than the control horses. By d 128, eST-treated horses had a greater increase (P < 0.01) in dorsal cortical bone width of the third metacarpal than the control horses, but treatment did not significantly affect medial, lateral, or palmar cortical bone width.

Can metacarpal cortical area predict the occurrence of hip fracture in women and men over 3 decades of follow-up? Results from the Framingham Osteoporosis Study.

The purpose of this study was to determine if a single measurement of metacarpal cortical area could predict the subsequent risk of hip fracture over a long-term follow-up period. Thirteen hundred eighty-six women and 1014 men (mean age [+/- SD] 61 +/- 8 years) underwent posteroanterior hand radiography between 1966 and 1970 as part of the Framingham Study. Measurements of cortical bone width (external width and medullary width) were made at the midpoint of the second metacarpal with a digital caliper to the nearest 0.1 mm. Hip fracture occurrence was ascertained on all survivors through December 1995. Surprisingly, in women, there was no significant increase in hip fracture according to metacarpal cortical area measurements (per SD decrease) in either age-adjusted (hazard ratio [HR] = 1.13; 95% CI, 0.94-1.35) or multivariate-adjusted models (HR = 1.06; 95% CI, 0.88-1.27). The same results were seen when considering only those women who were > or = 65 years of age at the time of their X-ray or when considering only the first 10 years of follow-up. When the type of hip fracture was considered in women, after adjustment for other risk factors, there appeared to be an association between metacarpal cortical area and intertrochanteric fracture risk (HR = 1.24; 95% CI, 0.91-1.71) but not femoral neck fracture risk (HR = 0.93; 95% CI, 0.71-1.22). In men, the age-adjusted risk of hip fracture was increased modestly per SD decrease in metacarpal cortical area (HR = 1.38; 95% CI, 1.02-1.87), and this remained true after adjustment for potential confounders. In this prospective cohort study with up to 30 years of follow-up, metacarpal cortical area in men predicted hip fracture risk. In women, the only association between metacarpal cortical area and fracture risk was observed for intertrochanteric fractures and was not significant when adjusting for multiple potential confounders. We conclude that this peripheral measure of bone status is not a potent predictor of hip fracture over a long period of follow-up.

A histomorphological investigation of the effect of cyclosporin on trabecular bone of the rat mandibular condyle

The effect of cyclosporin A (CSA) on the condylar trabecular bone was evaluated by microscopy. Twenty, 5-week-old male Sprague–Dawley rats were divided into a treated and a control group. Animals in the treated group received CSA, 15 mg/kg body weight, by gastric feeding daily for 4 weeks; controls received the vehicle only. Five animals from each group were killed at the end of weeks 2 and 4. After histological processing, 10 tissue sections from the mid-part of the mandibular condyle were examined. Generally, a histopathological osteopenia was observed around the condyle after CSA treatment, especially at the end of week 4. In the control animals, the trabecular bone volume steadily increased from weeks 2 to 4 (from 0.46±0.07 to 0.61±0.07 mm 3/mm 3). However, the bone volume was significantly less in the CSA group than in the control group at both times (0.33±0.02 vs 0.46±0.07 and 0.26±0.07 vs 0.61±0.07 mm 3/mm 3 for CSA vs control group at the end of weeks 2 and 4, respectively). Conversely, an increased marrow volume was observed in the CSA group at both these times (0.60±0.02 vs 0.42±0.08 and 0.71±0.06 vs 0.31±0.06 mm 3/mm 3 for CSA vs control group at the end of weeks 2 and 4, respectively). Decreases were also observed in trabecular thickness, osteoid seam width, osteoid volume and cortical bone width. Because trabecular bone mass, osteoid mass and cortical bone thickness all showed a decrease after CSA at both times, an inhibitory effect of CSA on trabecular bone formation in the mandibular condyle is proposed.

Evaluation of long-term sequential changes in bone mass and strength following withdrawal of incadronate disodium (YM175) in ovariectomized rats

We evaluated the long-term effects of withdrawal of a newer third-generation bisphosphonate, incadronate disodium (YM175), on both cancellous and cortical bone mass and strength in ovariectomized (OVX) rats. One hundred and sixty female SD rats at 13 weeks of age were randomized into four groups: sham-operated, OVX, and low- and high- YM (0.01 or 0.1mg/kgs.c., three times a week after OVX). After 4 weeks of treatment with vehicle or incadronate disodium, rats from each group (n = 8) were killed at 0 (baseline), 3, 6, 9, and 12 months after the withdrawal of YM175. Histomorphometric studies of the proximal tibia revealed a dose-dependent decrease in OVX-induced bone turnover; cancellous bone volume was significantly higher in the YM groups compared with the OVX control group up to 6 months after withdrawal at low dose and up to 12 months after withdrawal at high dose. The low-dose group showed little effect on tibial diaphyseal cortical bone volume and width, while the high-dose group preserved both cortical parameters 12 months after withdrawal. Mechanical testing of femurs revealed that both metaphyseal and diaphyseal strengths were significantly higher at high dose compared with the OVX group until 12 months after withdrawal. These observations demonstrated that highdose incadronate disodium preserved both cancellous and cortical bone mass and strength in OVX rats for 12 months after withdrawal of the agent.

Effect of combined treatment with vitamin K2 and 1 alpha-(OH)-vitamin D3 on bone loss in ovariectomized rats

Different types of therapeutic agents for osteoporosis are often simultaneously prescribed for the same patient, but limited experimental findings indicate the significance of combined treatment. In the present study, the inhibitory effect of combined vitamin K2(K2) and 1 alpha-(OH)-vitamin D3(D3) treatment on bone loss was compared to that of K2 or D3 alone in ovariectomized rats. Female rats (20-week-old) were ovariectomized and divided into 4 groups as follows: they were treated for 8 weeks with vehicle, K2 (30 mg/kg), D3 (0.3 microgram/kg) and K2 and D3 (K2 + D3) at the respective doses. K2 was given as a dietary supplement and D3 was orally administered 3 times a week. Bone density of the femurs was measured by peripheral quantitative computed tomography. Ovariectomy resulted in decreased bone density in proximal metaphysis, especially in the trabecular region, and treatment with K2, D3 or K2 + D3 inhibited this decrease. Moreover, in the K2 + D3 group, bone density and mineral content in the trabecular region in proximal metaphysis and cortical bone width in diaphysis were significantly higher than those in the D3 group. Consistent with these observations, bone strength in the femoral midshaft tended to increase only in the K2 + D3 group compared to that in the vehicle group. These findings indicate that combined K2 and D3 treatment is more effective for bone loss than that with K2 or D3 alone.

Age-related changes in cortical bone in men: metacarpal bone mass measurement study

Metacarpal cortical bone mass was measured in 507 healthy Japanese men aged 40–95 years, using a microdensitometer to determine age-related changes in cortical bone in these middle-aged and elderly men. Total bone mass showed a significant negative correlation with age (r = −0.281; P < 0.0001). While bone width showed no significant correlation with age, bone marrow width showed a significant positive correlation (r = 0.210; P < 0.0001), and cortical bone width and cortical bone density showed a significant negative correlation with age (r = −0.265; P < 0.0001; r = −0.268; P < 0.0001, respectively). On the other hand, cortical bone width and cortical bone density showed a significant positive correlation with total bone mass (r = 0.814; P < 0.0001; r = 0.474, P < 0.0001, respectively). These findings suggest that cortical bone mass decreases significantly with aging in middle-aged and elderly men, perhaps as a result of two factors — decreased cortical bone width, ie, cortical bone thinning due to bone loss at the endosteal side of the cortex, and decreased cortical bone density due to progression of intracortical porosity. Cortical bone thinning may influence age-related cortical bone loss more than decreasing cortical bone density.

Factors influencing the speed of sound through the proximal phalanges.

The amplitude-dependent speed of sound (AD-SOS) in the proximal phalanges is reported to be sensitive to osteoporotic changes. We investigated the influence of bone thickness and cortical thickness on AD-SOS. Phantoms made of Perspex were designed to simulate different bone width (11-16 mm) and cortical thickness (3-7.5 mm). The phantoms were designed with two opposing flat and cylindrical surfaces. The effect of cortical thickness was examined by drilling holes (simulating the medullary canal) of different diameters (1-7 mm) in the middle of the Perspex cylinders. The effect of sample thickness was investigated on solid Perspex phantoms of varied lengths. The standardized precision errors of AD-SOS measurement in vivo and in vitro on volunteers and phantoms were 2.8 and 0.9%, respectively. AD-SOS was influenced by the bone width, cortical thickness, and location along the phalanx. A decrease in either cortical width or cortical thickness resulted in a decrease in AD-SOS. The effect is dependent on whether the contact surface is curved or flat. It is possible that a curved surface has a focusing effect on the wave through the porous core, whereas for a flat surface, the path of the waves might not pass through the center. When cortical thickness and bone width were expressed as a ratio, there was a linear relationship between this ratio and AD-SOS through the phantoms. AD-SOS was independent of thickness for samples greater than 11 mm.

Bone modeling and cell-material interface responses induced by nickel-titanium shape memory alloy after periosteal implantation.

The purpose of this study was to evaluate the new bone formation, modeling and cell-material interface responses induced by nickel-titanium shape memory alloy after periosteal implantation. We used a regional acceleratory phenomenon (RAP) model, in which a periosteal contact stimulus provokes an adaptive modelling response. NiTi has thermal shape memory and superelasticity properties uncommon in other implant alloys. So far, there are insufficient data concerning the biocompatibility of NiTi as a bone implant. NiTi was compared to stainless steel (stst) and Ti-6Al-4V. The test implant was placed in contact with the intact femur periosteum, but it was not fixed inside the bone. Histomorphometry with digital image analysis was used to determine the bone formation and resorption parameters. The ultrastructural features of cell-material adhesion were analysed with scanning electron microscopy (FESEM). A typical peri-implant bone wall modelation was seen due to the normal RAP. The maximum new woven bone formation started earlier (2 weeks) in the Ti-6Al-4V group than in the NiTi (P < 0.01) group, but also decreased earlier, and at 8 weeks the NiTi (P < 0.05) and stst (P < 0.005) groups had greater cortical bone width. At 12 and 26 weeks no statistical differences were seen in the histomorphometric values. The histological response of the soft tissues around the NiTi implant was also clearly non-toxic and non-irritating. Cell adhesion and focal contacts were similar between the materials studied by FESEM. We conclude that NiTi had no negative effect on total new bone formation or normal RAP after periosteal implantation during a 26-week follow-up.

Age-related changes in insulin-like growth factor I and II in human femoral cortical bone: lack of correlation with bone mass

The concentration of insulin-like growth factor-I (IGF-I) in human cortical bone declines with age, but the relevance of this decline for cortical bone turnover and bone mass is unknown. In the present study, we simultaneously assessed the concentration of IGF-I and -II in cortical bone matrix and histomorphometric parameters of bone mass and bone turnover in 125 samples from the proximal human femur shaft. Bone width decreased by 27% and porosity increased by 100% in female cortical bone between the fourth and the ninth decade. Similar, but weaker, changes tended to occur in male cortical bone. The concentrations of both IGF species were correlated with the percentage of osteons undergoing bone remodeling. However, despite age-related decreases in both IGF species in men and in IGF-I in women, neither of the IGFs accounted for age-related or age-independent variability in cortical porosity or bone width. In conclusion, these data suggest that the local concentrations of IGF-I and -II are related to cortical bone turnover. In contrast, our study provides no evidence for a major role of bone matrix IGF-I and -II as determinants of cortical bone mass in elderly individuals. Whether other components of the IGF system may be stronger determinants of cortical bone loss remains to be determined.

Regional variations in the progression of bone loss in two different mouse osteopenia models.

Differences in trabecular and cortical bone loss have been demonstrated clinically, but differences in bone loss at different skeletal sites remain unclear. We examined regional variations in bone loss histomorphometrically in two strains of mice in which osteopenia progresses spontaneously: tiptoe-walking Yoshimura (twy) mice (from 4 to 37 weeks of age) and senescent ICR mice (from 4 to 88 weeks of age). Morphometrical measurements were obtained to investigate the changes with age in trabecular bone area and anterior cortical bone width in the lumbar vertebral body, trabecular bone area in the tibia, bone area in the parietal bone, and the cortical index in the humerus. Results showed that, in twy mice, trabecular turnover was higher than in ICR mice, and bone loss progressed in the following order: tibial trabecular bone, lumbar trabecular bone, parietal bone, lumbar anterior cortical bone, and the humerus. In ICR mice, bone formation declined after 60 weeks. Bone loss progressed in tibial trabecular bone and the parietal bone at 60 weeks of age, followed by lumbar trabecular bone, lumbar anterior cortical bone, and the humerus at 88 weeks of age. Bone loss varied at each site and between the two mouse strains, with different bone turnover rates. The findings of the present study indicate that special attention should be paid to regional variations in the progression of bone loss associated with differences in pathologic features.

Age-related changes in cortical bone in women: Metacarpal bone mass measurement study

The mechanism of age-related cortical bone loss was investigated in 229 Japanese women, 41–94 years of age, by metacarpal bone mass measurement. While no significant correlation was found between bone width and age, a significant increase in bone marrow width, and significant decreases in cortical bone density and total bone mass were observed in association with aging (P < 0.0001). There was a significant negative correlation between total bone mass and bone marrow width (r = −0.239; P < 0.0005), and significant positive correlations between both total bone mass and cortical bone density (r = 0.539; P < 0.0001) and cortical bone width (r = 0.839; P < 0.0001). The findings suggested that age-related cortical bone loss in middle-aged and elderly women resulted from two different factors; a decrease in cortical bone density caused by progression of intracortical porosity, and a decrease in cortical bone width as a result of bone loss on the endosteal surface. The latter had a greater influence on an age-related cortical bone loss than the former.

Supraphysiologic levels of testosterone affect cancellous and cortical bone in the young female cynomolgus monkey.

The goal of this study was to evaluate the effects of chronically-elevated male levels of the potent androgen testosterone on the quality and quantity of both cancellous and cortical bone in a young (mean age 8.0 years), nonhuman female primate model (M. fascicularis). Thirteen intact female monkeys received continuous testosterone supplementation via subcutaneous implants over a 24-month period. A group of 16 untreated, intact, age-matched female monkeys served as controls. At sacrifice, the lumbar vertebrae and femora were recovered in order to analyze the bone mineral quality and quantity of cancellous and cortical bone, respectively, and compared to the control group. Mineralization profiles of the vertebrae and femora were obtained using the density fractionation technique. Chemical analysis of the three largest fractions retrieved by density fractionation was performed to evaluate differences in %Ca, %P, Ca/P ratio, and mineral content (%Ca + %PO4) between the control and experimental groups. In addition, unfractionated bone powder was examined by X-ray diffraction to identify any changes in crystal size. Coronal sections of vertebrae were analyzed for structural parameters using histomorphometry and image analysis. Cross sections taken at the midshaft diaphyseal femora were analyzed for structural macroscopic and intracortical parameters. A nonsignificant shift in the mineralization profile of the vertebrae was observed whereas there was a significant shift in the mineralization profile towards more dense bone in the treated femora as compared with controls (P < 0.05). There was no difference in terms of size/strain of the cortical or cancellous bone crystal as detected by X-ray diffraction. There was a trend towards an increase in cancellous bone area (B.Ar.) in the testosterone-treated vertebrae (P = 0.08) as compared with controls. The architecture of the cancellous bone remained nonsignificantly different between the treatment and control groups as evaluated by image analysis. There was a decrease in osteoid perimeter (P = 0.05) in the experimental group as compared with controls. There was a significant decrease in eroded perimeter measurements in the experimental group as compared with controls (P < 0.03). Although there was a trend towards an increase in cancellous bone area, mineralization was not significantly different in the vertebrae of testosterone-treated female monkeys, indicating that the newly-formed bone tissue became relatively normally mineralized over the two-year period. An increase in bone area, with indices of an overall decreased remodelling pattern as compared with controls, suggests that cancellous bone in the young, nonhuman female primate had been receptive to supraphysiologic levels of testosterone supplementation over the two-year period. There was a trend for an increase in cortical bone area and width with an increased periosteal perimeter in the testosterone-treated group as compare with controls. There was an increase in intracortical remodelling activity with a significant increase in percent porosity (P < 0.05), osteonal bone (P < 0.05), and mean wall width (P < 0.05) in the testosterone-treated group. In conclusion, the cancellous bone from female monkeys appeared to respond to the antiresorptive stimulus of male levels of testosterone with significantly diminished turnover parameters in this compartment. In contrast, the cortical bone compartment responded by displaying significant intracortical remodelling over a two-year period.

Time course of femoral neck osteopenia in ovariectomized rats

To characterize osteopenic changes in the femoral neck of ovariectomized (ovx) rats, female Sprague-Dawley rats were ovx or sham operated upon at 3 months of age and killed at various times from 0 to 360 days postsurgery. Quantitative bone histomorphometry was performed on undecalcified longitudinal sections of the proximal femur from each rat. This skeletal site was found to be slowly growing, as its rate of longitudinal bone growth in 3-month-old baseline control rats (5 μm/day) was nearly a factor of 10 less than that of a more commonly used sample site, the proximal tibia. In control rats, cancellous bone volume and cortical bone width of the femoral neck remained relatively constant, but cancellous mineral apposition rate declined with age during the course of the study. In contrast, cancellous bone volume in ovx rats was significantly decreased to 75%–82% of control level at 30–90 days and further decreased to 50%–56% of control level at later times postovariectomy. Indices of cancellous bone turnover such as osteoclast and osteoblast surfaces and bone formation rate were markedly increased in ovx rats at 30 days, declined toward control levels by 90 days, then increased moderately at 180–360 days. In comparison to control rats, a slight decrease in cortical width of the femoral neck was observed in ovx rats at 180 days and reached statistical significance at 360 days postovariectomy. Endocortical bone formation rate was increased significantly in ovx rats compared with control rats at most time points. The results indicate that both cancellous and cortical osteopenia associated with high bone turnover occur in the femoral neck of ovx rats. Cancellous bone loss at this skeletal site is statistically significant as early as 30 days postovariectomy, but remains relatively moderate for the first 90 days before becoming more pronounced at later times after ovariectomy. In contrast, cortical osteopenia was not observed in the femoral neck of ovx rats until 1 year postovariectomy. This histomorphometric characterization of osteopenic changes in the femoral neck of ovx rats may serve as a basis for use of this slowly growing sample site in preclinical studies of the prevention and treatment of bone loss in the estrogen-depleted skeleton.

Cortical and cancellous bone in the human femoral neck: Evaluation of an interactive image analysis system

An interactive image analysis package was developed to examine whole cross-sections from the femoral neck. The package quantifies cortical width (Ct.Wi), cortical porosity (Ct.Po), and proportions of cortical, cancellous bone as a percentage of bone plus marrow area. Segmental analysis was used to quantify circumferential variations in bone distribution within the femoral cross-section. To evaluate reproducibility of data four independent operators analyzed previously prepared femoral neck sections from a 2000 bc population. Differences in total and circumferential distributions of cortical and cancellous bone with respect to gender and age of samples were demonstrated. Reproducibility was assessed using coefficients of variation (CV). Analysis of sections using a variable magnification, giving largest possible image size, rather than a set magnification reduced variation between operators for all measurements. Use of a calculated threshold significantly decreased variation between operators for the proportions of cortical and cancellous bone ( p ≤ 0.026). Dividing the image into 8 rather than 16 segments also improved reproducibility. There was little agreement between operators in the determination of cortical porosity. The mean CV for the other quantitative indices such as cortical width and proportions of cortical and cancellous bone ranged from 4.87% to 13.52%. The genders showed similar patterns in circumferential distribution of bone. Cortical width was significantly greater in the inferior region compared to the other areas, whereas percent cortical bone was lowest at the superior region. The center of mass (COM) for the younger age group was located anteriorly, whereas in the older samples the COM was located posteriorly of the center of area ( p = 0.041). Basic data relating to cortical and cancellous bone of acceptable reproducibility in comparison with current standards in iliac histomorphometry can now be provided at modest cost in operator time and resources.

Quantitative radiographic changes in the mandible, femur and vertebra in lactating rats fed a low-calcium diet.

To determine whether similar changes occur in the mandible, femur and vertebral body in generalized osteopenia. Osteopenia was induced in the bred animal group using a low calcium diet from parturition onwards. Control groups were virgin and bred rats fed a normal diet. Rats in each group were weighed weekly, and subgroups of 12 rats in each treatment group were killed at ages 18, 24, 36 and 48 weeks. A separate reference group of 12 rats was killed at age 12 weeks, i.e. day 0 of the comparative study. The mandibles, both femurs and the first lumbar vertebrae of all rats were removed post-mortem and radiographs made for each individual bone; measurements of cortical thickness and bone widths were made from these radiographs using a computer-based video image analysis system. Significant differences among treatment groups were detected for each bone type; changes were sustained over the 48-week study period for the femur and vertebrae but were transient, except for alveolar bone height, in the mandible. Significant differences were found for cortical thicknesses and bone widths in the mandible, femur and vertebrae, based on the duration of the low-calcium diet. Although significant differences in the thickness of some cortices were found in the mandible, dimensional changes were small. Mandibular cortical width is an unreliable indicator of osteopenia in this rat model.

Response of cortical bone to antiresorptive agents and parathyroid hormone in aged ovariectomized rats

The purpose of this study was to determine whether PTH has anabolic effects on cortical bone in aged ovariectomized (OVX) rats treated during the late stages of estrogen depletion. Groups of OVX rats were untreated for 1 year postovariectomy followed by treatment for 10 weeks with vehicle, estrogen, the bisphosphonate risedronate (NE-58095), calcitonin (CT), PTH, PTH + estrogen, PTH + NE-58095 or PTH+CT. A group of sham-operated control rats was treated with vehicle alone. Cross-sections of the tibial diaphysis immediately proximal to the tibiofibular junction were subjected to quantitative bone histomorphometry. In comparison to vehicle-treated control rats, the following structural changes were detected in cortical bone of vehicle-treated OVX rats: increased cortical bone tissue area, increased bone marrow area and a significant decrease in cortical width. Indices of endocortical bone formation were also significantly increased in vehicle-treated OVX rats relative to vehicle-treated control rats. Treatment with the antiresorptive agents estrogen, NE-58095 or CT prevented the decrease in cortical width in OVX rats, but failed to increase cortical bone area. In comparison to vehicle treatment of OVX rats, estrogen and CT decreased both periosteal and endocortical bone formation, whereas NE-58095 decreased endocortical, but not periosteal, bone formation. In contrast, treatment of OVX rats with PTH alone increased cortical bone area and width as well as decreased bone marrow area compared to vehicle treatment of OVX rats. The PTH-induced increase in cortical bone mass was associated with a marked increase in periosteal and endocortical bone formation. Concurrent treatment of OVX rats with PTH+estrogen, PTH + NE-58095 or PTH + CT did not have a greater anabolic effect on cortical bone than treatment with PTH alone. The results indicate that PTH, in contrast to estrogen, NE-58095 and CT, stimulates cortical bone formation and augments cortical bone mass in the tibial diaphysis of aged OVX rats. Therefore, cortical bone of aged OVX rats retains its ability to respond anabolically to PTH even during the late stages of estrogen depletion.

Radiographic geometric variation of equine long bones

Summary As more sophisticated research is performed to refine fracture fixation techniques for horses, it is important that normal values for the geometric properties of the bones of the appendicular skeleton be determined and that suitable controls be available. We evaluated the geometric properties of total bone width, cortical bone width, and medullary canal/trabecular bone width measured from 2 radiographic projections of equine long bones (humerus, radius, third metacarpal bone, femur, tibia, and third metatarsal bone) obtained from a general population of horses. Measurements were performed on slices separated by intervals equal to 5% of the bone's length. Slices were then grouped into 5 regions: proximal epiphysis, proximal part of the metaphysis, diaphysis, distal part of the metaphysis, and distal epiphysis. Results validated use of the contralateral bone as a control for assessing experimental models or clinical cases. Of 858 homotypic slice comparisons between left and right bones, significant (P ≤ 0.05) differences were detected in 31 (3.6%) of the comparisons. Of 168 homotypic region comparisons, significant differences were observed in 3 (1.8%) of the comparisons. The greatest variation between left and right bones was observed in metaphyseal regions, areas with bony protuberances, and regions with prominent bone superimposition. At a power of 0.8 for the statistical tests performed in this study, the mean homotypic variation of bones in each region is &lt; 5.8% for the proximal epiphysis, 11.3% for the proximal part of the metaphysis, 6.8% for the diaphysis, 12.2% for the distal part of the metaphysis, and 5.2% for the distal epiphysis.

Hyperthyroidism, thyroid hormone therapy, and bone.

Clinically symptomatic osteoporosis and fractures from thyrotoxicosis have been rare since the availability of antithyroid drugs and radioiodine for the treatment of hyperthyroidism. However, the widespread use of bone density measurements and sensitive TSH assays in the past decade has demonstrated that women taking levothyroxine with subclinical hyperthyroidism have reduced bone density. Cortical bone is affected more than trabecular bone, and postmenopausal women are at a greater risk than premenopausal women. However, it is uncertain whether subclinical hyperthyroidism is associated with an increased risk of fracture. Hypothyroidism is associated with an increase in cortical bone width. The initiation of levothyroxine treatment in hypothyroid women results in a reduction in cortical bone width to levels seen in euthyroid controls after 6-12 months. There is no reduction in bone density when women with subclinical hypothyroidism are treated with levothyroxine for a year. A single study showing reduced bone density in patients receiving chronic levothyroxine replacement therapy requires confirmation and raises an important question: Does levothyroxine replacement therapy, which results in higher serum thyroxine concentrations than those seen in euthyroid controls, accurately mimic physiology?

Anabolic effects of parathyroid hormone on cortical bone in ovariectomized rats

The purpose of this study was to determine whether PTH has anabolic effects on cortical bone in ovariectomized (OVX) rats similar to those previously observed in cancellous bone. Groups of OVX rats were untreated for the first 4 weeks postovariectomy followed by treatment for 5-, 10-, or 15-week periods with vehicle, estrogen, the bisphosphonate risedronate (NE-58095), PTH, PTH + estrogen or PTH + NE-58095. A group of sham-operated control rats was treated with vehicle alone. Cross sections of the tibial diaphysis immediately proximal to the tibiofibular junction were subjected to quantitative bone histomorphometry. In comparison to vehicle-treated control rats, the following structural changes were detected in cortical bone of OVX rats after 15 weeks of vehicle treatment: increased cortical bone tissue area, increased cortical bone area, and a trend for increased bone marrow area. Indices of periosteal bone formation were increased in vehicle-treated OVX rats at 5 weeks, but declined to control levels at the later time points. In addition, vehicle-treated OVX rats exhibited a nonsignificant trend for increased endocortical bone formation relative to vehicle-treated control rats throughout most of the study. Estrogen, but not NE-58095, prevented most of the changes in cortical bone structure associated with ovariectomy. In comparison to vehicle treatment of OVX rats, estrogen decreased both periosteal and endocortical bone formation whereas NE-58095 decreased endocortical, but not periosteal, bone formation. Treatment of OVX rats with PTH alone increased cortical bone area and width as well as decreased bone marrow area compared to vehicle-treated OVX rats. The PTH-induced increase in cortical bone mass was associated with a marked increase in periosteal and endocortical bone formation at 5 weeks of treatment. Afterwards, cortical bone formation in PTH-treated OVX rats declined toward the levels of vehicle-treated control and OVX rats. Concurrent treatment of OVX rats with PTH + estrogen or PTH + NE-58095 blunted somewhat the stimulatory effect of PTH on cortical bone formation, but presumably inhibited endocortical bone resorption as well. As a result, the increase in cortical bone area induced by the concurrent treatments was nearly identical to that of PTH alone. The data indicate that PTH, in contrast to estrogen and NE-58095, stimulates cortical bone formation and augments cortical bone mass in the tibial diaphysis of OVX rats. In this animal model, our findings do not support the contention that PTH augments cancellous bone at the expense of cortical bone in the estrogen-deplete skeleton.

Holding Power of Orthopaedic Screws in Femora of Young Calves

SummaryThe holding power and holding power per mm bone width of 4.5 mm and 5.5 mm cortical and 6.5 mm cancellous orthopaedic screws were obtained by load-to-failure studies in excised femora of young female Holstein calves. Mean ( ± SD) holding power (HP), holding power per mm bone width (HPBW), and holding power per cortical bone width (HPCW) of 4.5 mm (179.67 ± 59.74 kg), 5.5 mm (171.46 ± 76.52 kg), and 6.5 mm orthopaedic screws (191.10 ± 56.67 kg) were not significantly different. The HP, HPBW, HPCW, bone width (BW), and cortical width (CW) were not different between left and right femora. The greatest HP was obtained in the proximal femoral diaphysis, while the smallest HP was observed in the proximal and distal metaphysis. The increase in HP was related to the increase in CW, but was not related to the BW. The CW at the insertion sites of orthopaedic screws in femora was significantly less than in metacarpi and metatarsi. The limiting factor of holding power in all tests was the shear strength of the bone.This study compares the holding power, holding power per mm bone width, and holding power per mm cortical width of 4.5 mm and 5.5 mm cortical and 6.5 mm cancellous orthopaedic screws in excised femora of young female Holstein calves. The holding power, holding power per mm bone width, and holding power per mm cortical width of different screws were not significantly different.