Thermal stability and structure of cancellous bone mineral from the femoral head of patients with osteoarthritis or osteoporosis

Investigation of the inverse problem for the Arrhenius equation using the example of thermal degradation of spongin-based scaffolds

A mathematical description of the thermal degradation of spongin-based scaffolds is given. The Arrhenius integral was evaluated using the inverse problem approach, in which the unknown values were the activation energy E_A, the pre-exponential factor A, and the model function f(α) characterizing the physical process. The form of f(α) was determined and the values of the parameters E_A, A and T_S were evaluated in detail. Moreover, the function f(α) assessed in this study was compared with classical solid-state model functions. Finally, the mean square minimization approach was used to solve the inverse problem with unknown function f(α) and pre-exponential constant A. Likewise, the approximation of f(α) with 6th- and 7th-degree polynomials was used to obtain numerical values of E_A and A. This study evaluated the inverse problem approach for the Arrhenius equation. These investigations provide new insight into the description of the thermal degradation of spongin-based scaffolds.

Bone hydration: How we can evaluate it, what can it tell us, and is it an effective therapeutic target?

Water constitutes roughly a quarter of the cortical bone by volume yet can greatly influence mechanical properties and tissue quality. There is a growing appreciation for how water can dynamically change due to age, disease, and treatment. A key emerging area related to bone mechanical and tissue properties lies in differentiating the role of water in its four different compartments, including free/pore water, water loosely bound at the collagen/mineral interfaces, water tightly bound within collagen triple helices, and structural water within the mineral. This review summarizes our current knowledge of bone water across the four functional compartments and discusses how alterations in each compartment relate to mechanical changes. It provides an overview on the advent of- and improvements to- imaging and spectroscopic techniques able to probe nano-and molecular scales of bone water. These technical advances have led to an emerging understanding of how bone water changes in various conditions, of which aging, chronic kidney disease, diabetes, osteoporosis, and osteogenesis imperfecta are reviewed. Finally, it summarizes work focused on therapeutically targeting water to improve mechanical properties.

Investigation of Mechanical, Material, and Compositional Determinants of Human Trabecular Bone Quality in Type 2 Diabetes

CONTEXT

Increased bone fragility and reduced energy absorption to fracture associated with type 2 diabetes (T2D) cannot be explained by bone mineral density alone. This study, for the first time, reports on alterations in bone tissue's material properties obtained from individuals with diabetes and known fragility fracture status.

OBJECTIVE

To investigate the role of T2D in altering biomechanical, microstructural, and compositional properties of bone in individuals with fragility fracture.

METHODS

Femoral head bone tissue specimens were collected from patients who underwent replacement surgery for fragility hip fracture. Trabecular bone quality parameters were compared in samples of 2 groups, nondiabetic (n = 40) and diabetic (n = 30), with a mean duration of disease 7.5 ± 2.8 years.

RESULTS

No significant difference was observed in aBMD between the groups. Bone volume fraction (BV/TV) was lower in the diabetic group due to fewer and thinner trabeculae. The apparent-level toughness and postyield energy were lower in those with diabetes. Tissue-level (nanoindentation) modulus and hardness were lower in this group. Compositional differences in the diabetic group included lower mineral:matrix, wider mineral crystals, and bone collagen modifications-higher total fluorescent advanced glycation end-products (fAGEs), higher nonenzymatic cross-link ratio (NE-xLR), and altered secondary structure (amide bands). There was a strong inverse correlation between NE-xLR and postyield strain, fAGEs and postyield energy, and fAGEs and toughness.

CONCLUSION

The current study is novel in examining bone tissue in T2D following first hip fragility fracture. Our findings provide evidence of hyperglycemia's detrimental effects on trabecular bone quality at multiple scales leading to lower energy absorption and toughness indicative of increased propensity to bone fragility.

Mechanical Properties of Bone Ex Vivo

The primary functions of bone are to provide support and protection-mechanical functions. The aim of this chapter is to set out some of the methods that can be used to measure these properties in cortical and cancelleous bone from large (e.g., human or bovine) and small (e.g., mouse) animals. The difference between the properties of the sample (extrinsic properties) and the properties of the material (intrinsic properties) is introduced and techniques for measuring them suggested. The addition of other tests to give a complete characterization of a bone sample is presented.

Comparison of Decellularized Cow and Human Bone for Engineering Bone Grafts with Human Induced Pluripotent Stem Cells

IMPACT STATEMENT

Decellularized tissue matrices are popular as scaffolding materials for tissue engineering application. However, it is unclear whether interspecies differences in tissue parameters influence the quality of tissue grafts that are engineered using human stem cells. In this study, decellularized cow and human bone scaffolds were compared for engineering bone grafts using human induced pluripotent stem cell-derived mesodermal progenitor cells and despite minor differences in architecture and mass composition, both scaffolds equally support cell viability and tissue mineralization. Decellularized cow bone scaffolds therefore represent a suitable and more affordable alternative for engineering human bone grafts for basic and applied research.

Interleukin-6 from subchondral bone mesenchymal stem cells contributes to the pathological phenotypes of experimental osteoarthritis

As a main cause of morbidity in the aged population, osteoarthritis (OA) is characterized by cartilage destruction, synovium inflammation, osteophytes, and subchondral bone sclerosis. To date its etiology remains elusive. Recent data highlight an important role of subchondral bone in the onset and progression of OA. Therefore, elucidating the mechanisms underlying abnormal subchondral bone could be of importance in the treatment of OA. Interleukin-6 is a proinflammatory cytokine involved in many physiological and pathological processes. Although in vitro and in vivo studies have indicated that IL-6 is an important cytokine in the physiopathogenesis of OA, its effects on subchondral bone have not been studied in OA animal models. In this study, we aimed to i) investigate the role of IL-6 in the pathological phenotypes of OA subchondral bone MSCs including increase in cell numbers, mineralization disorder and abnormal type I collagen production; ii) explore whether the systemic blockade of IL-6 signaling could alleviate the pathological phenotypes of experimental OA. We found that IL-6 was over-secreted by OA subchondral bone MSCs compared with normal MSCs and IL-6/STAT3 signaling was over-activated in subchondral bone MSCs, which contributed to the pathological phenotypes of OA subchondral bone MSCs. More importantly, systemic inhibition of IL-6/STAT3 signaling with IL-6 antibody or STAT3 inhibitor AG490 decreased the severity of pathological phenotypes of OA subchondral bone MSCs and cartilage lesions in OA. Our findings provide strong evidence for a pivotal role for IL-6 signaling in OA and open up new therapeutic perspectives.

Towards new material biomarkers for fracture risk

Osteoporosis is a prevalent bone condition, characterised by low bone mass and increased fracture risk. Currently, the gold standard for identifying osteoporosis and increased fracture risk is through quantification of bone mineral density (BMD) using dual energy X-ray absorption (DEXA). However, the risk of osteoporotic fracture is determined collectively by bone mass, architecture and physicochemistry of the mineral composite building blocks. Thus DEXA scans alone inevitably fail to fully discriminate individuals who will suffer a fragility fracture. This study examines trabecular bone at both ultrastructure and microarchitectural levels to provide a detailed material view of bone, and therefore provides a more comprehensive explanation of osteoporotic fracture risk. Physicochemical characterisation obtained through X-ray diffraction and infrared analysis indicated significant differences in apatite crystal chemistry and nanostructure between fracture and non-fracture groups. Further, this study, through considering the potential correlations between the chemical biomarkers and microarchitectural properties of trabecular bone, has investigated the relationship between bone mechanical properties (e.g. fragility) and physicochemical material features.

The Role of Water Compartments in the Material Properties of Cortical Bone

Comprising ~20% of the volume, water is a key determinant of the mechanical behavior of cortical bone. It essentially exists in two general compartments: within pores and bound to the matrix. The amount of pore water-residing in the vascular-lacunar-canalicular space-primarily reflects intracortical porosity (i.e., open spaces within the matrix largely due to Haversian canals and resorption sites) and as such is inversely proportional to most mechanical properties of bone. Movement of water according to pressure gradients generated during dynamic loading likely confers hydraulic stiffening to the bone as well. Nonetheless, bound water is a primary contributor to the mechanical behavior of bone in that it is responsible for giving collagen the ability to confer ductility or plasticity to bone (i.e., allows deformation to continue once permanent damage begins to form in the matrix) and decreases with age along with fracture resistance. Thus, dehydration by air-drying or by solvents with less hydrogen bonding capacity causes bone to become brittle, but interestingly, it also increases stiffness and strength across the hierarchical levels of organization. Despite the importance of matrix hydration to fracture resistance, little is known about why bound water decreases with age in hydrated human bone. Using (1)H nuclear magnetic resonance (NMR), both bound and pore water concentrations in bone can be measured ex vivo because the proton relaxation times differ between the two water compartments, giving rise to two distinct signals. There are also emerging techniques to measure bound and pore water in vivo with magnetic resonance imaging (MRI). The NMR/MRI-derived bound water concentration is positively correlated with both the strength and toughness of hydrated bone and may become a useful clinical marker of fracture risk.

Towards the in vivo prediction of fragility fractures with Raman spectroscopy

Fragility fractures, those fractures which result from low level trauma, have a large and growing socio-economic cost in countries with aging populations. Bone-density-based assessment techniques are vital for identifying populations that are at higher risk of fracture, but do not have high sensitivity when it comes to identifying individuals who will go on to have their first fragility fracture. We are developing Spatially Offset Raman Spectroscopy (SORS) as a tool for retrieving chemical information from bone non-invasively in vivo. Unlike X-ray-based techniques SORS can retrieve chemical information from both the mineral and protein phases of the bone. This may enable better discrimination between those who will or will not go on to have a fragility fracture because both phases contribute to bone's mechanical properties. In this study we analyse excised bone with Raman spectroscopy and multivariate analysis, and then attempt to look for similar Raman signals in vivo using SORS. We show in the excised work that on average, bone fragments from the necks of fractured femora are more mineralised (by 5-10%) than (cadaveric) non-fractured controls, but the mineralisation distributions of the two cohorts are largely overlapped. In our in vivo measurements, we observe similar, but as yet statistically underpowered, differences. After the SORS data (the first SORS measurements reported of healthy and diseased human cohorts), we identify methodological developments which will be used to improve the statistical significance of future experiments and may eventually lead to more sensitive prediction of fragility fractures. © 2015 The Authors. Journal of Raman Spectroscopy Published by John Wiley & Sons, Ltd.

Comparison of microstructural and mechanical properties of trabeculae in femoral head from osteoporosis patients with and without cartilage lesions: a case-control study

Background

Degeneration of cartilage will change load distribution, affecting bone remodeling progress and trabecular structure and strength. However, in human primary osteoporosis, whether cartilage lesions would also affect properties beneath trabecular bone remains unknown. In this study, we explored the differences in local trabecular properties between osteoporosis patients with and without cartilage lesions.

Methods

Eighteen pairs of femoral heads with and without cartilage lesions in a weight-bearing area were collected from senile femoral neck fracture patients. The Mankin score and glycosaminoglycan (GAG) content were used to evaluate the severity of the cartilage lesions. Micro-CT and compression tests were used to obtain structural and mechanical characteristics of each trabecular column. Multivariate linear regression was performed to evaluate the association between mechanical parameters and the degree of cartilage lesion.

Results

In osteoporosis patients with cartilage lesions, the bone volume fraction (BV/TV) and trabecular thickness (Tb.Th) of the trabecular column were significantly higher than that of osteoporotic control patients (all P < 0.05), while the Young’s modulus was lower (P = 0.024). Multivariable linear regression indicated that in both groups, bone mineral density (BMD) significantly correlated with Young’s modulus (all P < 0.05). While in patients with cartilage lesion, GAG content was also correlated with Young’s modulus (standardized coefficient 0.443, P < 0.01).

Conclusions

Osteoporosis patients with cartilage lesions exhibited a weaker mechanical property of trabeculae. The intimate association of cartilage lesions and impairment of trabecular mechanical properties indicate that cartilage and trabeculae belong to an interdependent functional unit. Previously proposed adaptive mechanisms in osteoarthritis might also be applicable to the progression of osteoporosis.

Molecular spectroscopic identification of the water compartments in bone

Matrix bound water is a correlate of bone's fracture resistance and assessment of bound water is emerging as a novel measure of bone's mechanical integrity. Raman spectroscopy is one of the few nondestructive modalities to assess the hydration status in bone; however, it has not been used to study the OH-band in bone. A sequential dehydration protocol was developed to replace unbound (heat drying) and bound (ethanol or deuterium) water in bone. Raman spectra were collected serially to track the OH-band during dehydration. Spectra of synthetic hydroxyapatite, demineralized bone and bulk water were collected to identify mineral and collagen contributions to the OH-band. Band assignments were supported by computational simulations of the molecular vibrations of Gly-Pro-Hyp amino acid sequence. Experimentally and theoretically obtained spectra were interpreted for band-assignments. Water loss was measured gravimetrically and correlated to Raman intensities. Four peaks were identified to be sensitive to dehydration: 3220cm(-1) (water), 3325cm(-1) (NH and water), 3453cm(-1) (hydroxyproline and water), and 3584cm(-1) (mineral and water). These peaks were differentially sensitive to deuterium treatment such that some water peaks were replaced with deuterium oxide faster than the rest. Specifically, the peaks at 3325 and 3584cm(-1) were more tightly bound to the matrix than the remaining bands. Comparison of dehydration in mineralized and demineralized bone revealed a volume of water that may be locked in the matrix by mineral crystals. The OH-range of bone was dominated by collagen and the water since the spectral profile of dehydrated demineralized bone was similar to that of the mineralized bone. Furthermore, water associates to bone mainly by collagen as findings of experimentally and theoretically spectra. The current work is among the first thorough analysis of the Raman OH stretch band in bone and such spectral information may be used to understand the involvement of water in the fragility of aging and in diseased bone.

Partial removal of pore and loosely bound water by low-energy drying decreases cortical bone toughness in young and old donors

With an ability to quantify matrix-bound and pore water in bone, (1)H nuclear magnetic resonance (NMR) relaxometry can potentially be implemented in clinical imaging to assess the fracture resistance of bone in a way that is independent of current X-ray techniques, which assess bone mineral density as a correlate of bone strength. Working towards that goal, we quantified the effect of partial dehydration in air on the mechanical and NMR properties of human cortical bone in order to understand whether NMR is sensitive to water-bone interactions at low energy and whether such interactions contribute to the age-related difference in the toughness of bone. Cadaveric femurs were collected from male and female donors falling into two age groups: 21-60 years of age (young) and 74-99 years of age (old). After extracting two samples from the medial cortex of the mid-shaft, tensile tests were conducted on Wet specimens and paired, Partially Dry (PtlD) specimens (prepared by low-energy drying in air to remove ∼3% of original mass before testing). Prior analysis by micro-computed tomography found that there were no differences in intra-cortical porosity between the Wet and PtlD specimens nor did an age-related difference in porosity exist. PtlD specimens from young and old donors had significantly less toughness than Wet specimens, primarily due to a dehydration-related decrease in post-yield strain. The low-energy drying protocol did not affect the modulus and yield strength of bone. Subsequent dehydration of the PtlD specimens in a vacuum oven at 62°C and then 103°C, with quantification of water loss at each temperature, revealed an age-related shift from more loosely bound water to more tightly bound water. NMR detected a change in both bound and pore water pools with low-energy air-drying, and both pools were effectively removed when bone was oven-dried at 62°C, irrespective of donor age. Although not strictly significant due to variability in the drying and testing conditions, the absolute difference in toughness between Wet and PtlD tended to be greater for the younger donors that had higher bone toughness and more bound water for the wet condition than did the older donors. With sensitivity to low-energy bone-water interactions, NMR, which underpins magnetic resonance imaging, has potential to assess fracture resistance of bone as it relates to bone toughness.

Mechanical properties of bone ex vivo

The primary functions of bone are to do with support and protection - mechanical functions. The aim of this chapter is to set out some of the methods that can be used to measure these properties in cortical and cancelleous bone from large (e.g. human or bovine) and small (e.g. mouse) animals. The difference between properties of the sample (intrinsic properties) and properties of the material (extrinsic properties) is introduced and techniques for measuring them suggested. The addition of other tests to give a complete characterisation of a bone sample is presented.

Altered mineralization of human osteoarthritic osteoblasts is attributable to abnormal type I collagen production

OBJECTIVE

Bone tissue in osteoarthritis (OA) is composed of abundant undermineralized osteoid matrix. The aim of this study was to investigate the mechanisms responsible for this abnormal matrix, using in vitro OA subchondral osteoblasts.

METHODS

Primary normal and OA osteoblasts were prepared from tibial plateaus. Phenotype was determined by alkaline phosphatase activity, and osteocalcin, osteopontin, prostaglandin E2 (PGE2), and transforming growth factor beta1 (TGFbeta1) were assessed by enzyme-linked immunosorbent assay. Expression of COL1A1 and COL1A2 was determined by real-time polymerase chain reaction. The production of type I collagen was determined by the release of its C-terminal propeptide and Western blot analysis. In vitro mineralization was evaluated by alizarin red staining. Inhibition of TGFbeta1 expression was performed using a small interfering RNA technique.

RESULTS

Mineralization of OA osteoblasts was reduced compared with mineralization of normal osteoblasts, even in the presence of bone morphogenetic protein 2 (BMP-2). Alkaline phosphatase and osteocalcin levels were elevated in OA osteoblasts compared with normal osteoblasts, whereas osteopontin levels were similar. The COL1A1-to-COL1A2 messenger RNA ratio was 3-fold higher in OA osteoblasts compared with normal osteoblasts, and the production of collagen by OA osteoblasts was increased. Because TGFbeta1 inhibits BMP-2-dependent mineralization, and because TGFbeta1 levels are approximately 4-fold higher in OA osteoblasts than in normal osteoblasts, inhibiting TGFbeta1 levels in OA osteoblasts corrected the abnormal COL1A1-to-COL1A2 ratio and increased alizarin red staining.

CONCLUSION

Elevated TGFbeta1 levels in OA osteoblasts are responsible, in part, for the abnormal ratio of COL1A1 to COL1A2 and for the abnormal production of mature type I collagen. This abnormal COL1A1-to-COL1A2 ratio generates a matrix that blunts mineralization in OA osteoblasts.

High frequency ultrasound prediction of mechanical properties of cortical bone with varying amount of mineral content

In this study, we evaluate if high frequency ultrasound impedance measurements can predict the mechanical properties of bones where the amount of bone mineral is varied. The motivation stems from the potential utility of ultrasound as a noninvasive technique to evaluate and monitor the mechanical properties of bone during treatment of diseased states where the ratio of mineral content to organic matrix content could change (e.g., metabolic bone diseases, osteoarthritis, osteogenesis imperfecta, fracture healing). Eleven cortical bovine femur samples, which were taken along the long axis of femur, were used in each group. Bone samples with reduced mineral content (estimated to be 21% and 35% less than the control) were obtained by immersing samples into fluoride ion solution for 3 and 12 d. Control and fluoride treated samples were first tested mechanically in tension. Acoustic impedances of the mechanically tested samples were obtained by using scanning acoustic microscopy (SAM). Results from mechanical tests indicate that the tensile elastic modulus of the samples was highly correlated to the yield strength (r(2) = 0.94, p < 0.01) and to the ultimate strength (r(2) = 0.75, p < 0.01). SAM results indicate that the acoustic impedances were significantly correlated to the elastic modulus (r(2) = 0.85, p < 0.01), yield strength (r(2) = 0.86, p < 0.01) and ultimate strength (r(2) = 0.70, p < 0.01). These results show that ultrasonic techniques could potentially be used to predict the in vivo ultimate strength of bone tissue caused by changes in mineral content.

Uniform partial dissolution of bone mineral by using fluoride and phosphate ions combination

Mineral content is one of the main predictors of the mechanical properties of bone tissue. The contribution of the bone mineral phase to the mechanical properties of bone has been investigated by reducing the mineral content of bone with different in vitro treatment techniques such as hydrochloric acid (HCl), ethylenedinitrilo tetraacetic acid (EDTA), and fluoride ion treatment. In this study, we propose a new treatment technique which combines fluoride and phosphate ions. Bovine femur specimens were used to determine the mechanical properties of cortical bone after different fluoride phosphate ion combination treatments. The treatment solutions, which contain different fluoride and phosphate ion concentrations, dissolved part of the bone mineral in a uniform manner throughout the bone samples. Dissolution by products, which precipitated in the bone tissue, contained calcium fluoride with phosphate ions (CaF(2)/P) and fluorapatite/fluorhydroxyapatite-type material (FAp/FHAp) and acted as filler. Depending on the fluoride and phosphate concentration in a treatment solution, the precipitated material's ratio of FAp/FHAp to total fluoride containing phase (FAp/FHAp + CaF(2)/P) in bone tissue also changed. High fluoride ion content in treatment solutions generated more CaF(2)/P type of precipitate, and low fluoride ion concentration generated more FAp/FHAp type precipitates as compared to high fluoride concentration treatments. These experiments show that phosphate ions are another important parameter of a treatment solution, in addition to ionic strength, pH, and the duration of treatment. In vitro, phosphate fluoride combinations partially dissolve bone mineral content in a wider range than fluoride treatment alone in a uniform manner. With this new technique one can control more precisely the partial dissolution of the bone mineral and mineral phase's contribution to mechanical properties of bone tissue.

Abnormal insulin-like growth factor 1 signaling in human osteoarthritic subchondral bone osteoblasts

Insulin-like growth factor (IGF)-1 is a key factor in bone homeostasis and could be involved in bone tissue sclerosis as observed in osteoarthritis (OA). Here, we compare the key signaling pathways triggered in response to IGF-1 stimulation between normal and OA osteoblasts (Obs). Primary Obs were prepared from the subchondral bone of tibial plateaus of OA patients undergoing knee replacement or from normal individuals at autopsy. Phenotypic characterization of Obs was evaluated with alkaline phosphatase and osteocalcin release. The effect of IGF-1 on cell proliferation, alkaline phosphatase and collagen synthesis was evaluated in the presence or not of 50 ng/ml IGF-1, whereas signaling was studied with proteins separated by SDS-PAGE before western blot analysis. We also used immunoprecipitation followed by western blot analysis to detect interactions between key IGF-1 signaling elements. IGF-1 receptor (IGF-1R), Shc, Grb2, insulin receptor substrate (IRS)-1, and p42/44 mitogen-activated protein kinase (MAPK) levels were similar in normal and OA Obs in the presence or absence of IGF-1. After IGF-1 stimulation, the phosphorylation of IGF-1R in normal and OA Obs was similar; however, the phosphorylation of IRS-1 was reduced in OA Ob. In addition, the PI3K pathway was activated similarly in normal and OA Obs while that for p42/44 MAPK was higher in OA Obs compared to normal. p42/44 MAPK can be triggered via an IRS-1/Syp or Grb2/Shc interaction. Interestingly, Syp was poorly phosphorylated under basal conditions in normal Obs and was rapidly phosphorylated upon IGF-1 stimulation, yet Syp showed a poor interaction with IRS-1. In contrast, Syp was highly phosphorylated in OA Obs and its interaction with IRS-1 was very strong initially, yet rapidly dropped with IGF-1 treatments. The interaction of Grb2 with IRS-1 progressively increased in response to IGF-1 in OA Obs whereas this was absent in normal Ob. IGF-1 stimulation altered alkaline phosphatase in Ob, an effect reduced in the presence of PD98059, an inhibitor of p42/44 MAPK signaling, whereas neither IGF-1 nor PD98059 had any significant effect on collagen synthesis. In contrast, cell proliferation was higher in OA Obs compared to normal under basal conditions, and IGF-1 stimulated more cell proliferation in OA Obs than in normal Ob, an effect totally dependent on p42/44 MAPK activiy. The altered response of OA Obs to IGF-1 may be due to abnormal IGF-1 signaling in these cells. This is mostly linked with abnormal IRS-1/Syp and IRS-1/Grb2 interaction in these cells.

Weakly and strongly associated nonfreezable water bound in bones

Water bound in bone of rat tail vertebrae was investigated by 1H NMR spectroscopy at 210-300 K and by the thermally stimulated depolarization current (TSDC) method at 190-265 K. The 1H NMR spectra of water clusters were calculated by the GIAO method with the B3LYP/6-31G(d,p) basis set, and the solvent effects were analyzed by the HF/SM5.45/6-31G(d) method. The 1H NMR spectra of water in bone tissue include two signals that can be assigned to typical water (chemical shift of proton resonance deltaH=4-5 ppm) and unusual water (deltaH=1.2-1.7 ppm). According to the quantum chemical calculations, the latter can be attributed to water molecules without the hydrogen bonds through the hydrogen atoms, e.g., interacting with hydrophobic environment. An increase in the amount of water in bone leads to an increase in the amount of typical water, which is characterized by higher associativity (i.e., a larger average number of hydrogen bonds per molecule) and fills larger pores, cavities and pockets in bone tissue.

The relationships between bone mineral density in the spine, hip, distal femur and proximal tibia and medial minimum joint space width in the knees of healthy females

OBJECTIVE

To investigate the relationships between bone mineral density (BMD) in the hip, spine, distal femur and proximal tibia and minimum joint space width (mJSW) in the knees of healthy women.

METHODS

Women 22-68 years old without a history of knee pain, bone or joint disease or injury underwent a single, fixed-flexion knee X-ray. Radiographs were graded according to the Kellgren-Lawrence scale and analyzed for mJSW using a computer algorithm. Dual X-ray absorptiometry scans of the spine, hip, distal femur and proximal tibia were also acquired for each participant. Femur and tibia scans were acquired and analyzed using a modified version of the lumbar spine software.

RESULTS

Forty-five females, mean [standard deviation (SD)] age and body mass index (BMI) of 40.1 (13.9) years and 24.6 (4.5)kg/m(2), respectively, participated. The mean (SD) mJSW was 4.64 (0.68)mm. Linear regression analyses controlling for age and BMI revealed that BMD in the femoral trochanter and the central two regions of the tibia (T2 and T3) was significantly related to mJSW in the knee. A backwards regression analysis performed to determine which region of interest is most significantly related to mJSW revealed that femoral trochanter BMD (beta-value=0.416) is the most significant.

CONCLUSIONS

In contrast to the suggestion that BMD is negatively correlated with mJSW in the knees of osteoarthritic individuals, these results suggest that increasing BMD in the femoral trochanter and tibia is significantly associated with increasing mJSW in healthy females. Further investigation of this relationship is warranted.