Comparison of mineral quality and quantity in iliac crest biopsies from high- and low-turnover osteoporosis: an FT-IR microspectroscopic investigation

Early growth response gene 1 regulates bone properties in mice

Transcriptional regulation of the postnatal skeleton is incompletely understood. Here, we determined the consequence of loss of early growth response gene 1 (EGR-1) on bone properties. Analyses were performed on both the microscopic and molecular levels utilizing micro-computed tomography (micro-CT) and Fourier transform infrared imaging (FTIRI), respectively. Mice deficient in EGR-1 (Egr-1 (-/-)) were studied and compared to sex- and age-matched wild-type (wt) control animals. Femoral trabecular bone in male Egr-1 (-/-) mice demonstrated osteopenic characteristics marked by reductions in both bone volume fraction (BV/TV) and bone mineral density (BMD). Morphological analysis revealed fewer trabeculae in these animals. In contrast, female Egr-1 (-/-) animals had thinner trabeculae, but BV/TV and BMD were not significantly reduced. Analysis of femoral cortical bone at the mid-diaphysis did not show significant osteopenic characteristics but detected changes in cross-sectional geometry in both male and female Egr-1 (-/-) animals. Functionally, this resulted in decreased resistance to three-point bending as indicated by a reduction in maximum load, failure load, and stiffness. Assessment of compositional bone properties, including mineral-to-matrix ratio, carbonate-to-phosphate ratio, crystallinity, and cross-linking, in femurs by FTIRI did not show any significant differences or an appreciable trend between Egr-1 (-/-) and wt mice of either sex. Unexpectedly, rib bone from Egr-1 (-/-) animals displayed distinct osteopenic traits that were particularly pronounced in female mice. This study provides genetic evidence that both sex and skeletal site are critical determinants of EGR-1 activity in vivo and that its site-specific action may contribute to the mechanical properties of bone.

Comparison between infrared and Raman spectroscopic analysis of maturing rabbit cortical bone

The molecular composition of the organic and inorganic matrices of bone undergoes alterations during maturation. The aim of this study was to compare Fourier transform infrared (FT-IR) and near-infrared (NIR) Raman microspectroscopy techniques for characterization of the composition of growing and developing bone from young to skeletally mature rabbits. Moreover, the specificity and differences of the techniques for determining bone composition were clarified. The humeri of female New Zealand White rabbits, with age range from young to skeletally mature animals (four age groups, n = 7 per group), were studied. Spectral peak areas, intensities, and ratios related to organic and inorganic matrices of bone were analyzed and compared between the age groups and between FT-IR and Raman microspectroscopic techniques. Specifically, the degree of mineralization, type-B carbonate substitution, crystallinity of hydroxyapatite (HA), mineral content, and collagen maturity were examined. Significant changes during maturation were observed in various compositional parameters with one or both techniques. Overall, the compositional parameters calculated from the Raman spectra correlated with analogous parameters calculated from the IR spectra. Collagen cross-linking (XLR), as determined through peak fitting and directly from the IR spectra, were highly correlated. The mineral/matrix ratio in the Raman spectra was evaluated with multiple different peaks representing the organic matrix. The results showed high correlation with each other. After comparison with the bone mineral density (BMD) values from micro-computed tomography (micro-CT) imaging measurements and crystal size from XRD measurements, it is suggested that Raman microspectroscopy is more sensitive than FT-IR microspectroscopy for the inorganic matrix of the bone. In the literature, similar spectroscopic parameters obtained with FT-IR and NIR Raman microspectroscopic techniques are often compared. According to the present results, however, caution is required when performing this kind of comparison.

Bone material properties in actively bone-forming trabeculae in postmenopausal women with osteoporosis after three years of treatment with once-yearly Zoledronic acid

Zoledronic acid (ZOL), a third-generation aminobisphosphonate, showed pronounced antifracture efficacy in a phase III clinical trial [Health Outcomes and Reduced Incidence with Zoledronic Acid Once Yearly-Pivotal Fracture Trial (HORIZON-PFT)] when administered yearly (5-mg infusions of ZOL), producing significant reductions in morphometric vertebral, clinical vertebral, hip, and nonvertebral fractures by 70%, 77%, 41%, and 25%, respectively, over a 3-year period. The purpose of this study was to analyze the biopsies obtained during the HORIZON clinical trial (152 patients, 82 ZOL and 70 placebo) by means of Raman microspectroscopy (a vibrational spectroscopic technique capable of analyzing undecalcified bone tissue with a spatial resolution of approximately 0.6 µm) to determine the effect of ZOL therapy on bone material properties (in particular mineral/matrix ratio, lamellar organization, carbonate and proteoglycan (based on spectral identification of glycosaminoglycan) content, and mineral maturity/crystallinity) at similar tissue age (based on the presence of tetracycline double labels). The results indicated that while ZOL administration increased the mineral/matrix ratio compared with placebo, it also resulted in mineral crystallites with a quality profile (based on carbonate content and maturity/crystallinity characteristics) of younger (with respect to tissue age) bone. Since the comparisons between ZOL- and placebo-treated patients were performed at similar tissue age at actively forming bone surfaces, these results suggest that ZOL may be exerting an effect on bone matrix formation in addition to its well-established antiresorptive effect, thereby contributing to its antifracture efficacy.

Effects of different swimming exercise intensities on bone tissue composition in mice: a Raman spectroscopy study

OBJECTIVE

Raman spectroscopy was employed to evaluate the effect of different swimming intensities on femoral bone composition in an animal model.

BACKGROUND DATA

Intense swimming exercise may affect bone mineralization, and Raman technique has been shown to be effective in evaluating tissue composition (phosphate minerals and carbonate apatites - bands at 960 and 1170 cm(-1), as well as collagen matrix - amide I band at 1660 cm(-1)).

MATERIALS AND METHODS

Eighteen female Swiss Webster mice were separated into three groups (n = 6 per group) of sedentary (SED), and swimming with an intensity of 40% (PT-40) and 80% (PT-80) of the maximum load, with 6 weeks of training. Near-infrared Raman spectra (830 nm wavelength and 80 mW laser power) were obtained with a dispersive Raman spectrometer using a CCD camera and imaging spectrograph with 30-s integration time. Spectra were collected in the medial and lateral diaphysis of the femur and principal components analysis (PCA) was employed to extract features of the Raman bands of bone and to perform quantitative analysis.

RESULTS

PC1 vector resembles Raman spectra and carries information about apatite minerals and some contribution from organic matrix. A statistically significant difference was found in the PC1 scores (ANOVA, p < 0.05), indicating lower mineral concentrations in the femur in both the PT-40 and PT-80 groups compared to the SED group. These results corroborated with the radiographic assessment of bone density.

CONCLUSION

Raman technique associated with PCA statistics showed that intense swimming exercise may affect bone mineralization and remodeling in a mouse model of training.

Autologous bone graft: when shall we add growth factors?

Although the unquestionable value of autologous bone grafting and the analogous value of the reaming by-products in nonunion treatment have been mentioned extensively in the literature, there is ongoing vivid discussion for the treatment of those case scenarios where the fracture nonunion is complicated by other local environment adverse circumstances. The graft expansion with growth factors as the bone morphogenetic proteins (BMPs) offers the possibility to reduce the number of operative procedures, complications, length of hospital stay, and time to union. In this article, we consider the potential clinical scenarios for graft expansion with BMPs.

Aging and bone

Bones provide mechanical and protective function, while also serving as housing for marrow and a site for regulation of calcium ion homeostasis. The properties of bones do not remain constant with age; rather, they change throughout life, in some cases improving in function, but in others, function deteriorates. Here we review the modifications in the mechanical function and shape of bones, the bone cells, the matrix they produce, and the mineral that is deposited on this matrix, while presenting recent theories about the factors leading to these changes.

New method for Raman investigation of the orientation of collagen fibrils and crystallites in the Haversian system of bone

Knowledge of the organization of the components of bone is of primary importance in understanding how this tissue responds to stresses and provides a starting point for the design and development of biomaterials. Bone structure has been the subject of numerous studies. The mineralized fiber arrangement in cortical bone is either a twisted or orthogonal plywood structure. Both mineral models coexist in compact bone. Raman polarized spectroscopy offers definite advantages in the study of biological samples, enabling the simultaneous analysis of mineral and organic components and the determination of molecular orientation through the polarization properties of the Raman scattering. In this study, we used the Raman polarization approach to simultaneously investigate the orientation of collagen fibrils and apatite crystals in human cortical bone. Raman bands ratios were monitored as a function of sample orientation. Specific ratios were chosen--such as nu(3) PO(4)/nu(1) PO(4), amide III (1271 cm(-1))/amide III (1243 cm(-1)), and amide I/amide III (1243 cm(-1))--due to their sensitivity to apatite-crystal and collagen-fibril orientation. Based on this original approach, spatial changes were monitored as a function of distance from the Haversian canal. The results revealed simultaneous tilting in intra-lamellar collagen-fibril and mineral crystal orientations. These results are consistent with a twisted plywood organization in the Haversian bone structure at the lamellar level. But at molecular level, the co-alignment of the collagen fibrils and the apatite crystal is observed in the innermost lamellae and becomes gradually less ordered as the distance from the Haversian canal increases. This work highlights the interest of Raman spectroscopy for the multiscale investigation of bone structure.

Mineral maturity and crystallinity index are distinct characteristics of bone mineral

The purpose of this study was to test the hypothesis that mineral maturity and crystallinity index are two different characteristics of bone mineral. To this end, Fourier transform infrared microspectroscopy (FTIRM) was used. To test our hypothesis, synthetic apatites and human bone samples were used for the validation of the two parameters using FTIRM. Iliac crest samples from seven human controls and two with skeletal fluorosis were analyzed at the bone structural unit (BSU) level by FTIRM on sections 2-4 mum thick. Mineral maturity and crystallinity index were highly correlated in synthetic apatites but poorly correlated in normal human bone. In skeletal fluorosis, crystallinity index was increased and maturity decreased, supporting the fact of separate measurement of these two parameters. Moreover, results obtained in fluorosis suggested that mineral characteristics can be modified independently of bone remodeling. In conclusion, mineral maturity and crystallinity index are two different parameters measured separately by FTIRM and offering new perspectives to assess bone mineral traits in osteoporosis.

Infrared spectroscopy indicates altered bone turnover and remodeling activity in renal osteodystrophy

Renal osteodystrophy alters metabolic activity and remodeling rate of bone and also may lead to different bone composition. The objective of this study was to characterize the composition of bone in high-turnover renal osteodystrophy patients by means of Fourier transform infrared spectroscopic imaging (FTIRI). Iliac crest biopsies from healthy bone (n = 11) and patients with renal osteodystrophy (ROD, n = 11) were used in this study. The ROD samples were from patients with hyperparathyroid disease. By using FTIRI, phosphate-to-amide I ratio (mineral-to-matrix ratio), carbonate-to-phosphate ratio, and carbonate-to-amide I ratio (turnover rate/remodeling activity), as well as the collagen cross-link ratio (collagen maturity), were quantified. Histomorphometric analyses were conducted for comparison. The ROD samples showed significantly lower carbonate-to-phosphate (p < .01) and carbonate-to-amide I (p < .001) ratios. The spatial variation across the trabeculae highlighted a significantly lower degree of mineralization (p < .05) at the edges of the trabeculae in the ROD samples than in normal bone. Statistically significant linear correlations were found between histomorphometric parameters related to bone-remodeling activity and number of bone cells and FTIRI-calculated parameters based on carbonate-to-phosphate and carbonate-to-amide I ratios. Hence the results suggested that FTIRI parameters related to carbonate may be indicative of turnover and remodeling rate of bone.

Pro416Arg cherubism mutation in Sh3bp2 knock-in mice affects osteoblasts and alters bone mineral and matrix properties

Cherubism is an autosomal dominant disorder in children characterized by unwarranted symmetrical bone resorption of the jaws with fibrous tissue deposition. Mutations causing cherubism have been identified in the adaptor protein SH3BP2. Knock-in mice with a Pro416Arg mutation in Sh3bp2 exhibit a generalized osteoporotic bone phenotype. In this study, we examined the effects of this "cherubism" mutation on spectroscopic indices of "bone quality" and on osteoblast differentiation. Fourier-transform infrared imaging (FTIRI) analysis of femurs from wild-type and Sh3bp2 knock-in mice showed decreased mineral content, decreased mineral crystallinity/crystal size, and increased collagen maturity in homozygous mutants. To assess osteoblast maturation in vivo, knock-in mice were crossed with transgenic mice over-expressing GFP driven by 3.6-kb or 2.3-kb Col1a1 promoter fragments. Reduced numbers of mature osteoblasts were observed in homozygous mice. Neonatal calvarial cultures, which were enriched for osteoblasts by depletion of hematopoietic cells (negative selection for Ter119- and CD45-positive cells) were investigated for osteoblast-specific gene expression and differentiation, which demonstrated that differentiation and mineralization in homozygous osteoblast cultures was impaired. Co-cultures with calvarial osteoblasts and bone marrow macrophages showed that mutant osteoblasts appear to increase osteoclastogenesis resulting in increased bone resorption on bone chips. In summary, the Sh3bp2 mutation in cherubism mice alters bone quality, reduces osteoblast function, and may contribute to excessive bone resorption by osteoclasts. Our data, together with previous osteoclast studies, demonstrate a critical role of Sh3bp2 in bone remodeling and osteoblast differentiation.

The assessment of fracture risk

Bone mineral density is considered to be the standard measure for the diagnosis of osteoporosis and the assessment of fracture risk. The majority of fragility fractures occur in patients with bone mineral density in the osteopenic range. The Fracture Risk Assessment Tool (FRAX) can be used as an assessment modality for the prediction of fractures on the basis of clinical risk factors, with or without the use of femoral neck bone mineral density. Treatment of osteoporosis should be considered for patients with low bone mineral density (a T-score of between -1.0 and -2.5) as well as a ten-year risk of hip fracture of > or = 3% or a ten-year risk of a major osteoporosis-related fracture of > or = 20% as assessed with the FRAX. Biochemical bone markers are useful for monitoring the efficacy of antiresorptive or anabolic therapy and may aid in identifying patients who have a high risk of fracture. An approach combining the assessment of bone mineral density, clinical risk factors for fracture with use of the FRAX, and bone turnover markers will improve the prediction of fracture risk and enhance the evaluation of patients with osteoporosis.

Collagen cross-links as a determinant of bone quality: a possible explanation for bone fragility in aging, osteoporosis, and diabetes mellitus

Collagen cross-linking, a major post-translational modification of collagen, plays important roles in the biological and biomechanical features of bone. Collagen cross-links can be divided into lysyl hydroxylase and lysyloxidase-mediated enzymatic immature divalent cross-links,mature trivalent pyridinoline and pyrrole cross-links, and glycation- or oxidation-induced non-enzymatic cross-links(advanced glycation end products) such as glucosepane and pentosidine. These types of cross-links differ in the mechanism of formation and in function. Material properties of newly synthesized collagen matrix may differ in tissue maturity and senescence from older matrix in terms of crosslink formation. Additionally, newly synthesized matrix in osteoporotic patients or diabetic patients may not necessarily be as well-made as age-matched healthy subjects. Data have accumulated that collagen cross-link formation affects not only the mineralization process but also microdamage formation. Consequently, collagen cross-linking is thought to affect the mechanical properties of bone. Furthermore,recent basic and clinical investigations of collagen cross-links seem to face a new era. For instance, serum or urine pentosidine levels are now being used to estimate future fracture risk in osteoporosis and diabetes. In this review, we describe age-related changes in collagen cross-links in bone and abnormalities of cross-links in osteoporosis and diabetes that have been reported in the literature.

Autologous bone graft: when shall we add growth factors?

Although the unquestionable value of autologous bone grafting and the analogous value of the reaming by-products in nonunion treatment have been mentioned extensively in the literature, there is ongoing vivid discussion for the treatment of those case scenarios where the fracture nonunion is complicated by other local environment adverse circumstances. The graft expansion with growth factors as the bone morphogenetic proteins (BMPs) offers the possibility to reduce the number of operative procedures, complications, length of hospital stay, and time to union. In this article, we consider the potential clinical scenarios for graft expansion with BMPs.

Application of bone morphogenetic proteins to femoral non-unions: a 4-year multicentre experience

Fracture non-unions often complicate orthopaedic trauma. BMPs (bone morphogenetic proteins) are currently considered the most appealing osteoinductive agents. Applications of BMP-7 since January 2004 were prospectively recorded in a multicentre registry of aseptic femoral non-unions. The study included 30 patients who had undergone a median of 1 revision operation before BMP-7 application and who were followed up for a median 24 months. In 23/30 cases the application of BMP-7 was combined with revision of the fixation, and in 12 it was combined also with autograft. Non-union healing was verified in 26/30 cases in a median period of 6 months. No adverse events were associated with BMP-7 application. Our case series supports the safety and efficacy of BMP-7 in femoral non-unions. Multicentre networks and systematic, long-term follow-up of patients may improve understanding of this promising osteoinductive bone substitute.

Trabecular packet-level lamellar density patterns differ by fracture status and bone formation rate in white females

Spatial patterns of mineralization for human iliac crest cancellous bone were measured from images obtained by quantitative backscattered electron microscopy. Biopsies collected from vertebral fracture patients and healthy individuals with high or low bone formation rate (BFR(s)) were examined (fracture/low BFR(s): N=12, fracture/high BFR(s): N=10, normal/low BFR(s): N=12, normal/high BFR(s): N=15). 20 by 20 pixel square areas or smaller were sampled from superficial and deep remodeling packets. Mean (Z(mean)) and standard deviation (SD) of mineralization were measured, and coefficients of variation (CV=SD/Z(mean)) were calculated. Fast Fourier transform analysis was used to quantify the distribution of the mineral in the packets. "FFT_ratio" was defined as the ratio magnitude of the principal spatial frequency to the average atomic number density. A higher FFT_ratio occurred in specimens with more pronounced alternating layers of light and dark as visible in the backscattered electron image, which was defined as lamellar patterning. Two-way ANOVA revealed that the coefficients of variation of mineralization for both superficial and deep packets were significantly lower in fracture patients than in normal individuals. However, the interaction between turnover rate and group (fracture/non-fracture) indicated that the difference in packet CV occurred among the low turnover individuals and not among those with high turnover. Mean mineralization levels and CV between deep and superficial packets were highly correlated. Regressions of packet CV of mineralization and FFT_ratio were highly significant (p<0.001) for all packets pooled and for packets divided by group (fracture/normal). However, analyses of packet CV and FFT_ratio by individual were variable (R(2) from 0.00338 to 0.700). Packet-level mineralization variability may be associated with fracture toughness, and fracture patients had less variable packet-level mineralization. The result that the packet CV varied significantly between fracture and non-fracture individuals with low turnover suggests that for low turnover subjects without fracture, high variability in mineralization may have a protective effect. In high turnover patients, the accelerated turnover may prevent the lamellar variability from developing over time. Strong correlations between CV and Z(mean) for both superficial and deep packets imply that newly formed bone is created similarly to older bone within an individual. Fourier transform results show that the mineralization variability found within packets is associated with lamellar patterning. Lamellar structure has been hypothesized to guide microcrack propagation in order to optimize bone strength and toughness. Osteoporotics with fracture had less pronounced lamellation than healthy normals and may be more prone to fracture.

Synergistic role of hydroxyapatite nanoparticles and pulsed electromagnetic field therapy to prevent bone loss in rats following exposure to simulated microgravity

The purpose of the present study was to use capacitive coupling of pulsed electromagnetic field (CC-PEMF) and hydroxyapatite nanoparticles (HAp) as a countermeasure to prevent osteoporosis induced by simulated microgravity. We used the hind-limb suspension (HLS) rat model to simulate microgravity-induced bone losses for 45 days. In order to compare the resulting changes, mineralogical (bone mineral density [BMD], calcium [Ca], and phosphorus [P]), biochemical (osteocalcin, alkaline phosphatase [ALP], and type I collagen), and histological (scanning electron microscopy) parameters were adopted. As a countermeasure to the above, the effect of PEMF and HAp application were examined. Three-month-old female Wistar rats were randomly divided into control (n = 8), HLS (n = 8), HLS with PEMF (n = 8), HLS with HAp nanoparticles (n = 8), and HLS with HAp and PEMF (n = 8). We observed: 1) significant decrease (p < 0.01) in BMD, Ca, P, type I collagen, and ALP activity in femur and tibia in hind-limb bone and serum osteocalcin in HLS rats as compared with the ground control. 2) Nonsignificant increase in BMD (p < 0.1), Ca (p < 0.1), P (p < 0.5), type I collagen (p < 0.1), and ALP activity (p < 0.5) in femur and tibia in hind-limb bone and serum osteocalcin (p < 0.5) in HLS + PEMF rats compared with HLS rats. 3) Significant increase in BMD (p < 0.02), Ca (p < 0.05), P (p < 0.05), type I collagen (p < 0.02), and ALP activity (p > 0.02) in femur and tibia in hind-limb bone with a nonsignificant increase in serum osteocalcin (p > 0.1) in HLS + HAp rats compared to HLS rats. 4) Significant increase in BMD (p > 0.01). Ca (p > 0.01). P (p > 0.01). type I collagen (p > 0.01). and ALP activity (p > 0.01) in femur and tibia in hind-limb bone and serum osteocalcin (p > 0.02) were also observed. Results suggest that a combination of low level PEMF and Hap nanoparticles has potential to control bone loss induced by simulated microgravity.

Use of FTIR spectroscopic imaging to identify parameters associated with fragility fracture

BMD does not entirely explain an individual's risk of fracture. The purpose of this study was to assess whether specific differences in spatially resolved bone composition also contribute to fracture risk. These differences were assessed using Fourier transform infrared spectroscopic imaging (FTIRI) and analyzed through multiple logistic regression. Models were constructed to determine whether FTIRI measured parameters describing mineral content, mineral crystal size and perfection, and collagen maturity were associated with fracture. Cortical and cancellous bone were independently evaluated in iliac crest biopsies from 54 women (32 with fractures, 22 without) who had significantly different spine but not hip BMDs and ranged in age from 30 to 83 yr. The parameters that were significantly associated with fracture in the model were cortical and cancellous collagen maturity (increased with increased fracture risk), cortical mineral/matrix ratio (higher with increased fracture risk), and cancellous crystallinity (increased with increased fracture risk). As expected, because of its correlation with cortical but not cancellous bone density, hip BMD was significantly associated with fracture risk in the cortical but not the cancellous model. This research suggests that additional parameters associated with fracture risk should be targeted for therapies for osteoporosis.

Spatial variation in osteonal bone properties relative to tissue and animal age

Little is known about osteonal bone mineral and matrix properties, although these properties are of major importance for the understanding of bone alterations related to age and bone diseases such as osteoporosis. During aging, bone undergoes modifications that compromise their structural integrity as shown clinically by the increase of fracture incidence with age. Based on Fourier transform infrared (FTIR) analysis from baboons between 0 and 32 yr of age, consistent systematic variations in bone properties as a function of tissue age are reported within osteons. The patterns observed were independent of animal age and positively correlated with bone tissue elastic behavior measured by nano-indentation. As long as tissue age is expressed as a percentage of the entire osteon radius, osteonal analyses can be used to characterize disease changes independent of the size of the osteon. These mineral and matrix analyses can be used to explain bone fragility. The mineral content (mineral-to-matrix ratio) was correlated with the animal age in both old (interstitial) and newly formed bone tissue, showing for the first time that age-related changes in BMC can be explain by an alteration in the mineralization process itself and not only by an imbalance in the remodeling process.

Spectroscopic markers of bone quality in alendronate-treated postmenopausal women

Comparison of infrared spectroscopic images of sections from biopsies of placebo-treated post-menopausal women and women treated for 3 years with 10 mg/day alendronate demonstrated significant increases in cortical bone mineral content, no alterations in other spectroscopic markers of "bone quality," but a decrease in tissue heterogeneity.

METHODS

The material properties of thick sections from iliac crest biopsies of seven alendronate-treated women were compared to those from ten comparably aged post-menopausal women without bone disease, using infrared spectroscopic imaging at approximately 7 microm spatial resolution. Parameters evaluated were mineral/matrix ratio, crystallinity, carbonate/amide I ratio, and collagen maturity. The line widths at half maximum of the pixel histograms for each parameter were used as measures of heterogeneity.

RESULTS

The mineral content (mineral/matrix ratio) in the cortical bone of the treated women's biopsies was higher than that in the untreated control women. Crystallinity, carbonate/protein, and collagen maturity indices were not significantly altered; however, the pixel distribution was significantly narrowed for all cortical and trabecular parameters with the exception of collagen maturity in the alendronate treatment group.

CONCLUSIONS

The increases in mineral density and decreased fracture risk associated with bisphosphonate treatment may be counterbalanced by a decrease in tissue heterogeneity, which could impair tissue mechanical properties. These consistent data suggest that alendronate treatment, while increasing the bone mass, decreases the tissue heterogeneity.

Divergent effects of glucocorticoids on cortical and trabecular compartment BMD in childhood nephrotic syndrome

Glucocorticoid (GC) effects on skeletal development have not been established. The objective of this pQCT study was to assess volumetric BMD (vBMD) and cortical dimensions in childhood steroid-sensitive nephrotic syndrome (SSNS), a disorder with minimal independent deleterious skeletal effects. Tibia pQCT was used to assess trabecular and cortical vBMD, cortical dimensions, and muscle area in 55 SSNS (age, 5-19 yr) and >650 control participants. Race-, sex-, and age-, or tibia length-specific Z-scores were generated for pQCT outcomes. Bone biomarkers included bone-specific alkaline phosphatase and urinary deoxypyridinoline. SSNS participants had lower height Z-scores (p < 0.0001) compared with controls. In SSNS, Z-scores for cortical area were greater (+0.37; 95% CI = 0.09, 0.66; p = 0.01), for cortical vBMD were greater (+1.17; 95% CI = 0.89, 1.45; p < 0.0001), and for trabecular vBMD were lower (-0.60; 95% CI, = -0.89, -0.31; p < 0.0001) compared with controls. Muscle area (+0.34; 95% CI = 0.08, 0.61; p = 0.01) and fat area (+0.56; 95% CI = 0.27, 0.84; p < 0.001) Z-scores were greater in SSNS, and adjustment for muscle area eliminated the greater cortical area in SSNS. Bone formation and resorption biomarkers were significantly and inversely associated with cortical vBMD in SSNS and controls and were significantly lower in the 34 SSNS participants taking GCs at the time of the study compared with controls. In conclusion, GCs in SSNS were associated with significantly greater cortical vBMD and cortical area and lower trabecular vBMD, with evidence of low bone turnover. Lower bone biomarkers were associated with greater cortical vBMD. Studies are needed to determine the fracture implications of these varied effects.

Prolonged treatments with antiresorptive agents and PTH have different effects on bone strength and the degree of mineralization in old estrogen-deficient osteoporotic rats

Current approved medical treatments for osteoporosis reduce fracture risk to a greater degree than predicted from change in BMD in women with postmenopausal osteoporosis. We hypothesize that bone active agents improve bone strength in osteoporotic bone by altering different material properties of the bone. Eighteen-month-old female Fischer rats were ovariectomized (OVX) or sham-operated and left untreated for 60 days to induce osteopenia before they were treated with single doses of either risedronate (500 microg/kg, IV), zoledronic acid (100 microg/kg, IV), raloxifene (2 mg/kg, PO, three times per week), hPTH(1-34) (25 microg/kg, SC, three times per week), or vehicle (NS; 1 ml/kg, three times per week). Groups of animals were killed after days 60 and 180 of treatment, and either the proximal tibial metaphysis or lumbar vertebral body were studied. Bone volume and architecture were assessed by muCT and histomorphometry. Measurements of bone quality included the degree of bone mineralization (DBM), localized elastic modulus, bone turnover by histomorphometry, compression testing of the LVB, and three-point bending testing of the femur. The trabecular bone volume, DBM, elastic modulus, and compressive bone strength were all significantly lower at day 60 post-OVX (pretreatment, day 0 study) than at baseline. After 60 days of all of the bone active treatments, bone mass and material measurements agent were restored. However, after 180 days of treatment, the OVX + PTH group further increased BV/TV (+30% from day 60, p < 0.05 within group and between groups). In addition, after 180 days of treatment, there was more highly mineralized cortical and trabecular bone and increased cortical bone size and whole bone strength in OVX + PTH compared with other OVX + antiresorptives. Treatment of estrogen-deficient aged rats with either antiresorptive agents or PTH rapidly improved many aspects of bone quality including microarchitecture, bone mineralization, turnover, and bone strength. However, prolonged treatment for 180 days with PTH resulted in additional gains in bone quality and bone strength, suggesting that the maximal gains in bone strength in cortical and trabecular bone sites may require a longer treatment period with PTH.

Disease recognition by infrared and Raman spectroscopy

Infrared (IR) and Raman spectroscopy are emerging biophotonic tools to recognize various diseases. The current review gives an overview of the experimental techniques, data-classification algorithms and applications to assess soft tissues, hard tissues and body fluids. The methodology section presents the principles to combine vibrational spectroscopy with microscopy, lateral information and fiber-optic probes. A crucial step is the classification of spectral data by a variety of algorithms. We discuss unsupervised algorithms such as cluster analysis or principal component analysis and supervised algorithms such as linear discriminant analysis, soft independent modeling of class analogies, artificial neural networks support vector machines, Bayesian classification, partial least-squares regression and ensemble methods. The selected topics include tumors of epithelial tissue, brain tumors, prion diseases, bone diseases, atherosclerosis, kidney stones and gallstones, skin tumors, diabetes and osteoarthritis.

DSPP effects on in vivo bone mineralization

Dentin sialophosphoprotein has been implicated in the mineralization process based on the defective dentin formation in Dspp null mice (Dspp-/-). Dspp is expressed at low levels in bone and Dspp-/- femurs assessed by quantitative micro-computed tomography (micro-CT) and Fourier transform infrared spectroscopic imaging (FTIRI) exhibit some mineral and matrix property differences from wildtype femurs in both developing and mature mice. Compared to wildtype, Dspp-/- mice initially (5 weeks) and at 7 months had significantly higher trabecular bone volume fractions and lower trabecular separation, while at 9 months, bone volume fraction and trabecular number were lower. Cortical bone mineral density, area, and moments of inertia in Dspp-/- were reduced at 9 months. By FTIRI, Dspp-/- animals initially (5 months) contained more stoichiometric bone apatite with higher crystallinity (crystal size/perfection) and lower carbonate substitution. This difference progressively reversed with age (significantly decreased crystallinity and increased acid phosphate content in Dspp-/- cortical bone by 9 months of age). Mineral density as determined in 3D micro-CT and mineral-to-matrix ratios as determined by 2D FTIRI in individual cortical and trabecular bones were correlated (r(2)=0.6, p<0.04). From the matrix analysis, the collagen maturity of both cortical and trabecular bones was greater in Dspp-/- than controls at 5 weeks; by 9 months this difference in cross-linking pattern did not exist. Variations in mineral and matrix properties observed at different ages are attributable, in part, to the ability of the Dspp gene products to regulate both initial mineralization and remodeling, implying an effect of Dspp on bone turnover.

Glucocorticoid-induced bone loss in mice can be reversed by the actions of parathyroid hormone and risedronate on different pathways for bone formation and mineralization

OBJECTIVE

Glucocorticoid excess decreases bone mineralization and microarchitecture and leads to reduced bone strength. Both anabolic (parathyroid hormone [PTH]) and antiresorptive agents are used to prevent and treat glucocorticoid-induced bone loss, yet these bone-active agents alter bone turnover by very different mechanisms. This study was undertaken to determine how PTH and risedronate alter bone quality following glucocorticoid excess.

METHODS

Five-month-old male Swiss-Webster mice were treated with the glucocorticoid prednisolone (5 mg/kg in a 60-day slow-release pellet) or placebo. From day 28 to day 56, 2 groups of glucocorticoid-treated animals received either PTH (5 microg/kg) or risedronate (5 microg/kg) 5 times per week. Bone quality and quantity were measured using x-ray tomography for the degree of bone mineralization, microfocal computed tomography for bone microarchitecture, compression testing for trabecular bone strength, and biochemistry and histomorphometry for bone turnover. In addition, real-time polymerase chain reaction (PCR) and immunohistochemistry were performed to monitor the expression of several key genes regulating Wnt signaling (bone formation) and mineralization.

RESULTS

Compared with placebo, glucocorticoid treatment decreased trabecular bone volume (bone volume/total volume [BV/TV]) and serum osteocalcin, but increased serum CTX and osteoclast surface, with a peak at day 28. Glucocorticoids plus PTH increased BV/TV, and glucocorticoids plus risedronate restored BV/TV to placebo levels after 28 days. The average degree of bone mineralization was decreased after glucocorticoid treatment (-27%), but was restored to placebo levels after treatment with glucocorticoids plus risedronate or glucocorticoids plus PTH. On day 56, RT-PCR revealed that expression of genes that inhibit bone mineralization (Dmp1 and Phex) was increased by continuous exposure to glucocorticoids and glucocorticoids plus PTH and decreased by glucocorticoids plus risedronate, compared with placebo. Wnt signaling antagonists Dkk-1, Sost, and Wif1 were up-regulated by glucocorticoid treatment but down-regulated after glucocorticoid plus PTH treatment. Immunohistochemistry of bone sections showed that glucocorticoids increased N-terminal Dmp-1 staining while PTH treatment increased both N- and C-terminal Dmp-1 staining around osteocytes.

CONCLUSION

Our findings indicate that both PTH and risedronate improve bone mass, degree of bone mineralization, and bone strength in glucocorticoid-treated mice, and that PTH increases bone formation while risedronate reverses the deterioration of bone mineralization.

The effect of the microscopic and nanoscale structure on bone fragility

Bone mineral density is the gold-standard for assessing bone quantity and diagnosing osteoporosis. Although bone mineral density measurements assess the quantity of bone, the quality of the tissue is an important predictor of fragility. Understanding the macro- and nanoscale properties of bone is critical to understanding bone fragility in osteoporosis. Osteoporosis is a disease that affects more than 75 million people worldwide. The gold standard for osteoporosis prognosis, bone mineral density, primarily measures the quantity of bone in the skeleton, overlooking more subtle aspects of bone's properties. Bone quality, a measure of bone's architecture, geometry and material properties, is evaluated via mechanical, structural and chemical testing. Although decreased BMD indicates tissue fragility at the clinical level, changes in the substructure of bone can help indicate how bone quality is altered in osteoporosis. Additionally, mechanical properties which can quantify fragility, or bone's inability to resist fracture, can be changed due to alterations in bone architecture and composition. Recent studies have focused on examination of bone on the nanoscale, suggesting the importance of understanding the interactions of the mineral crystals and collagen fibrils and how they can alter bone quality. It is therefore important to understand alterations in bone that occur at the macro-, micro- and nanoscopic levels to determine what parameters contribute to decreased bone quality in diseased tissue.

Application of BMP-7 to tibial non-unions: a 3-year multicenter experience

The effective treatment of the often debilitating, longlasting and large-asset-consuming complication of fracture non-unions has been in the centre of scientific interest the last decades. The use of alternative bone substitutes to the gold standard of autologous graft includes the osteoinductive molecules named bone morphogenetic proteins (BMPs). A multicenter registry and database (bmpusergroup.co.uk) focused on the application of BMP-7/OP-1 was created in December 2005. We present the preliminary results, using the prospective case-series of aseptic tibial non-unions as an example. Sixty-eight patients fulfilled the inclusion criteria for this observational study, with a minimum follow-up of 12 months. The median duration of tibial non-union prior to BMP-7 application was 23 months (range 9-317 mo). Patients had undergone a median of 2 (range 0-11) revision procedures prior to the administration of BMP-7. In 41% the application of BMP-7 was combined with revision of the fixation at the non-union site. Non-union healing was verified in 61 (89.7%) in a median period of 6.5 months (range 3-15 mo). No adverse events or complications were associated with BMP-7 application. The safety and efficacy of BMP-7 was verified in our case series, and was comparable to the existing evidence. The establishment of multicenter networks and the systematic and long-term follow- up of these patients are expected to provide further information and significantly improve our understanding of this promising osteoinductive bone substitute.

A comparison of the physical and chemical differences between cancellous and cortical bovine bone mineral at two ages

To assess possible differences between the mineral phases of cortical and cancellous bone, the structure and composition of isolated bovine mineral crystals from young (1-3 months) and old (4-5 years) postnatal bovine animals were analyzed by a variety of complementary techniques: chemical analyses, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and (31)P solid-state magic angle spinning nuclear magnetic resonance spectroscopy (NMR). This combination of methods represents the most complete physicochemical characterization of cancellous and cortical bone mineral completed thus far. Spectra obtained from XRD, FTIR, and (31)P NMR all confirmed that the mineral was calcium phosphate in the form of carbonated apatite; however, a crystal maturation process was evident between the young and old and between cancellous and cortical mineral crystals. Two-way analyses of variance showed larger increases of crystal size and Ca/P ratio for the cortical vs. cancellous bone of 1-3 month than the 4-5 year animals. The Ca/(P + CO(3)) remained nearly constant within a given bone type and in both bone types at 4-5 years. The carbonate and phosphate FTIR band ratios revealed a decrease of labile ions with age and in cortical, relative to cancellous, bone. Overall, the same aging or maturation trends were observed for young vs. old and cancellous vs. cortical. Based on the larger proportion of newly formed bone in cancellous bone relative to cortical bone, the major differences between the cancellous and cortical mineral crystals must be ascribed to differences in average age of the crystals.

The associations between mineral crystallinity and the mechanical properties of human cortical bone

It is well known that the amount of mineralization renders bone its stiffness. However, besides the mere amount of the mineral phase, size and shape of carbonated apatite crystals are postulated to affect the mechanical properties of bone tissue as predicted by composite mechanics models. Despite this predictive evidence, there is little experimental insight on the relation between the characteristics of mineral crystals and hard tissue mechanics. In this study, Raman spectroscopy was used to provide information on the crystallinity of bone's mineral phase, a parameter which is an overall indicator of mineral crystal size and stoichiometric perfection. Raman scans and mechanical tests (monotonic and fatigue; n=64 each) were performed on the anterior, medial, lateral and posterior quadrant sections of 16 human cadaveric femurs (52 y.o.-85 y.o.). The reported coefficient of determination values (R(2)) were adjusted for the effects of age to bring out the unbiased contribution of crystallinity. Crystallinity was able to explain 6.7% to 48.3% of the variation in monotonic mechanical properties. Results indicated that the tissue-level strength and stiffness increased with increasing crystallinity while the ductility reduced. Crystallinity explained 11.3% to 63.5% of the variation in fatigue properties. Moduli of specimens with greater crystallinity degraded at a slower rate and, also, they had longer fatigue lives. However, not every anatomical quadrant displayed these relationships. In conclusion, these results acknowledge crystal properties as an important bone quality factor and raise the possibility that aberrations in these properties may contribute to senile osteoporotic fractures.

Influence of microarchitecture alterations on ultrasonic backscattering in an experimental simulation of bovine cancellous bone aging

An experimental model which can simulate physical changes that occur during aging was developed in order to evaluate the effects of change of mineral content and microstructure on ultrasonic properties of bovine cancellous bone. Timed immersion in hydrochloric acid was used to selectively alter the mineral content. Scanning electron microscopy and histological staining of the acid-treated trabeculae demonstrated a heterogeneous structure consisting of a mineralized core and a demineralized layer. The presence of organic matrix contributed very little to normalized broadband ultrasound attenuation (nBUA) and speed of sound. All three ultrasonic parameters, speed of sound, nBUA and backscatter coefficient, were sensitive to changes in apparent density of bovine cancellous bone. A two-component model utilizing a combination of two autocorrelation functions (a densely populated model and a spherical distribution) was used to approximate the backscatter coefficient. The predicted attenuation due to scattering constituted a significant part of the measured total attenuation (due to both scattering and absorption mechanisms) for bovine cancellous bone. Linear regression, performed between trabecular thickness values and estimated from the model correlation lengths, showed significant linear correlation, with R(2)=0.81 before and R(2)=0.80 after demineralization. The accuracy of estimation was found to increase with trabecular thickness.

Bone biopsy in patients with osteoporosis

Although rarely used to diagnose and manage patients with osteoporosis, bone biopsies are performed to establish bone quality, including degree of mineralization and microarchitecture; to assess bone turnover and bone loss mechanisms; and to analyze treatment effects on bone structure and bone turnover. Bone biopsies are also the only method to diagnose mineralization defect or frank osteomalacia. Due to the availability of antiresorptive agents and anabolic drugs, determining bone turnover and bone-loss mechanisms is critical to appropriate treatment regimen selection. Bone biopsies establish the safety and efficacy of new therapeutic modalities. Further, new techniques such as molecular morphometry (in situ hybridization and immunohistochemistry) and analysis of bone content and crystal perfection have been applied to undecalcified bone and elucidated pathogenetic mechanisms or abnormalities in bone microstructure.

The degree of bone mineralization is maintained with single intravenous bisphosphonates in aged estrogen-deficient rats and is a strong predictor of bone strength

The treatment of osteoporotic women with bisphosphonates significantly reduces the incidence of bone fractures to a degree greater than can be explained by an increase in bone mineral density. In this study, 18-month Fischer 344 rats were ovariectomized and treated with a single dose of risedronate (intravenous, iv, 500 microg), zoledronic acid (iv, 100 microg) or continuous raloxifene (2 mg/kg, po, 3x/week). High resolution microCT was used to measure lumbar vertebral bone microarchitecture, the degree of bone mineralization (DBM) and the distribution of mineral. Small angle X-ray scattering was used to investigate mineral crystallinity. We found prolonged estrogen deficiency, reduced trabecular bone volume, and increased micro architecture bone compression strength lowered the degree of mineralization. Treatment with resorptive agents (bisphosphonates>raloxifene) prevented the loss of mineralization, trabecular bone volume and bone compression strength. Crystal size was not changed with OVX or with anti-resorptive treatments. In conclusion, in the aged estrogen-deficient rat model, single intravenous doses of two bisphosphonates were effective in maintaining the compressive bone strength for 180 days by reducing bone turnover, and maintaining the DBM to a greater degree than with raloxifene.

Development of a planar array infrared reflection spectrograph for reflection-absorption spectroscopy of thin films at metal and water surfaces

Planar array infrared (PA-IR) spectroscopy offers several advantages over Fourier transform infrared (FT-IR) methods, including ultrafast speed (<100 micros temporal resolution) and excellent sensitivity. However, obtaining spectra in the range of 1800 to 1000 cm(-1) of films at the air-water interface remains difficult due to the poor IR reflectivity of water, the extremely low concentration of the thin film on the water subphase, and the interference of water bands. In this study, we report a new planar array infrared reflection spectrograph (PA-IRRS), which has several advantages over conventional approaches. This instrument can record sample and reference spectra simultaneously with an instrumental setup that is the same as that of a single-beam instrument by splitting the incident infrared beam into two sections on a plane mirror (H) or a water trough. With this design, the instrument can accommodate large infrared accessories, such as a water trough, without a loss of infrared beam intensity. Water bands can be subtracted to obtain a high-quality spectrum for poly(L-lactic acid) Langmuir film on the water subphase with a resolution of about 6 cm(-1) in 10.8 s. Hence, this PA-IRRS system has great potential for investigating the time-resolved dynamics of a broad range of Langmuir films, such as cellular membranes or biopolymers, on the water subphase.

FT-IR imaging of native and tissue-engineered bone and cartilage

Fourier transform infrared (FT-IR) imaging and microspectroscopy have been extensively applied to the analyses of tissues in health and disease. Spatially resolved mid-IR data has provided insights into molecular changes that occur in diseases of connective or collagen-based tissues, including, osteoporosis, osteogenesis imperfecta, osteopetrosis and pathologic calcifications. These techniques have also been used to probe chemical changes associated with load, disuse, and micro-damage in bone, and with degradation and repair in cartilage. This review summarizes the applications of FT-IR microscopy and imaging for analyses of bone and cartilage in healthy and diseased tissues, and illustrates the application of these techniques for the characterization of tissue-engineered bone and cartilage.

Biological enhancement of tibial diaphyseal aseptic non-unions: the efficacy of autologous bone grafting, BMPs and reaming by-products

The mandatory stimulus that can optimise the healing pathway can be electrical, mechanical, biological, or a combination of all these parameters. A variety of means has been utilised for biological enhancement, including extracorporeal shock wave, electrical, ultrasound stimulation, the reaming technique of IM nailing, bone graft substitutes, osteogenic cells and bioactive molecules produced by tissue engineering techniques. The aim of this study is to present a review of the existing evidence for the efficacy of reaming, autologous bone grafting and the commercially available growth factors (BMP-2 and BMP-7) for the treatment of aseptic tibial non-unions. The gold standard method of enhancing bone healing in cases of tibial non-union remains the autologous bone graft. Autogenous bone grafts possess osteoconductive, osteoinductive properties and also osteoprogenitor cells. However, their harvesting is associated with high morbidity and many complications reaching percentages of 30%. Intramedullary reamed nailing, either used as an alternative fixation method or as an exchange to a wider implant, offers the unique biomechanical advantages of an intramedullary device, together with the osteoinductive stimulus of the by-products of reaming, and the aptitude for early weight-bearing and active rehabilitation. The safety of administration of the commercial distributed growth factors (BMP-2 and BMP-7), combined with the lack of the morbidity and the quantity restrictions that characterise autologous bone grafts, have given to this family of molecules a principal role between the other bone graft substitutes. On average the union rates reported in the 20 manuscripts that have been evaluated range from 58.3% to 100%, and the average time to union from 12.5 weeks to 48.4 weeks, indicating the significant discrepancies in the reported evidence and the multiplicity of different treatment strategies.

Insights into material and structural basis of bone fragility from diseases associated with fractures: how determinants of the biomechanical properties of bone are compromised by disease

Minimal trauma fractures in bone diseases are the result of bone fragility. Rather than considering bone fragility as being the result of a reduced amount of bone, we recognize that bone fragility is the result of changes in the material and structural properties of bone. A better understanding of the contribution of each component of the material composition and structure and how these interact to maintain whole bone strength is obtained by the study of metabolic bone diseases. Disorders of collagen (osteogenesis imperfecta and Paget's disease of bone), mineral content, composition and distribution (fluorosis and osteomalacia); diseases of high remodeling (postmenopausal osteoporosis, hyperparathyroidism, and hyperthyroidism) and low remodeling (osteopetrosis, pycnodysostosis); and other diseases (idiopathic male osteoporosis, corticosteroid-induced osteoporosis) produce abnormalities in the material composition and structure that lead to bone fragility. Observations in patients and in animal models provide insights on the biomechanical consequences of these illnesses and the nature of the qualities of bone that determine its strength.

Fracture healing in osteoporotic fractures: is it really different? A basic science perspective

Osteoporosis is a major health problem characterized by compromised bone strength that predisposes patients to an increased risk of fracture. Osteoporotic patients differ from normal subjects in bone mineral composition, bone mineral content, and crystallinity. Poor bone quality in patients with osteoporosis presents the surgeon with difficult treatment decisions. Much effort has been expended on improving therapies that are expected to preserve bone mass and thus decrease fracture risk. Manipulation of both the local fracture environment in terms of application of growth factors, scaffolds and mesenchymal cells, and systemic administration of agents promoting bone formation and bone strength has been considered as a treatment option from which promising results have recently been reported. Surprisingly, less importance has been given to investigating fracture healing in osteoporosis. Fracture healing is a complex process of bone regeneration, involving a well-orchestrated series of biological events that follow a definable temporal and spatial sequence that may be affected by both biological factors, such as age and osteoporosis, and mechanical factors such as stability of the osteosynthesis. Current studies mainly focus on preventing osteoporotic fractures. In recent years, the literature has provided evidence of altered fracture healing in osteoporotic bone, which may have important implications in evaluating the effects of new osteoporosis treatments on fracture healing. However, the mechanics of this influence of osteoporosis on fracture healing have not yet been clarified and clinical evidence is still lacking.

Bone tissue compositional differences in women with and without osteoporotic fracture

It is generally accepted that the hallmark of osteoporosis is a reduction in bone mass. There is significant overlap, however, in bone mineral density between osteoporotic and normal individuals. This study examined the chemical composition of bone tissue obtained from women who had sustained a fracture and women without fracture to determine if there are differences between the two groups. Nineteen fractured and eleven non-fractured proximal femurs were obtained, matched for age and bone volume fraction obtained from micro-computed tomography. Trabecular bone specimens were examined by Raman spectroscopy to determine measures of chemical composition. A subset of the specimens was utilized to compare locations at the fracture and regions at least 2 mm away from apparent tissue damage using Raman spectroscopy. In addition, fifteen iliac crest biopsies each were obtained from women who had sustained a fracture and from normal controls. Raman spectroscopy was used to determine measures of chemical composition of trabecular and cortical bone. The results demonstrated that femoral bone tissue in the region of visible damage had a trend towards differences compared to regions at least 2 mm from visible damage. Femoral trabecular bone in fractured women had a higher carbonate/amide I area ratio than in unfractured women. Iliac crest biopsies revealed a higher carbonate/phosphate ratio in cortical bone from women who had sustained a fracture. Results suggest that the chemical composition of bone tissue may be an additional risk factor for osteoporotic fracture.

Assessment of bone mineral and matrix using backscatter electron imaging and FTIR imaging

The resistance of bone to fracture is determined by its geometric and material properties. The geometry and density can be determined by radiographic methods, but material properties such as collagen structure, mineral composition, and crystal structure currently require analysis by invasive techniques. Backscatter electron imaging provides quantitative information on the distribution of the mineral within tissue sections, and infrared and other vibrational spectroscopic methods can supplement these data, providing site-specific information on mineral content as well as information on collagen maturity and distributions of crystal size and composition. This information contributes to the knowledge of "bone quality."

Mineral changes in osteoporosis: a review

Bone mineral composition, crystallinity, and bone mineral content of osteoporotic patients are different from those of normal subjects. We review the evidence that these mineralization parameters contribute to the strength (fracture resistance) of bone and the methods that have been used to examine them. A specific example is provided from analysis of biopsies from the Multiple Outcomes in Raloxifene Evaluation trial. For the analyses, randomly selected biopsies from placebo, low-dose, and high-dose groups (n = 5 per group) obtained at time zero and 2 years after treatment were examined by infrared imaging spectroscopy. In all cases, comparable increases in mineral content were found, but there were no significant variations in mineral crystallinity.