Grape seed extract supplement increases bone callus formation and mechanical strength: an animal study.

BACKGROUND: The positive effects of grape seed proanthocyanidin extract (GSPE) on bone health, which is a potent antioxidant, are known but its effects on fracture healing are not sufficiently covered in the literature. This study aims to investigate the effects of GSPE on fracture healing and biomechanics of healing bone. MATERIALS AND METHODS: Sixty-four adult Wistar-Albino male rats were divided into 8 groups of 8 animals in each group. Osteotomy was performed to the right femurs of all groups except the negative control (G1) and positive control (G2) groups, and intramedullary Kirchner wire was used for fixation. GSPE was given to half of the rats (G2-G4-G6-G8) 100 mg/kg/day by oral gavage. The rats were sacrificed on the tenth (G3-G4), twentieth (G5-G6), and thirtieth (G1-G2-G7-G8) days, respectively, and histopathological, radiological, and biomechanical examinations were performed. RESULTS: Histopathological examination of the specimens from the callus tissues revealed that bone healing was more prominent in the groups supplemented with GSPE (G4, G6, G8). There was a statistically significant improvement in radiological recovery scores and callus volumes in groups with GSPE. When biomechanical strengths were evaluated, it was found that GSPE increased bone strength not only in fracture groups but also in the positive control group (G2). CONCLUSIONS: As a result, this study showed that GSPE, a potent anti-oxidant, had a positive effect on bone healing and improved mechanical strength of the healing bone.

Female Human Spines with Simulated Osteolytic Defects: CT-based Structural Analysis of Vertebral Body Strength.

Purpose To evaluate a CT structural analysis protocol (SAP) for estimating the strength of human female cadaveric spines with lytic lesions. Materials and Methods Osteolytic foci was created in the middle vertebra of 44 thoracic and lumbar three-level segments from 11 female cadavers (age range, 50-70 years). The segments underwent CT by using standard clinical protocol and their failure strength was assessed at CT SAP. The spines were mechanically tested to failure in pure axial compression or in compression with torsion. The relationships of defect size, bone mineral density, and predicted failure load (at CT SAP) with measured vertebral strength were assessed with linear regression. Analysis of variance and Tukey test were used to evaluate the effect of region and mechanical test on spine strength. Results With axial compression, CT SAP predictions of vertebral strength correlated with the thoracic (r = 0.84; P < .001) and lumbar (r = 0.85; P < .001) segment-measured strength. Bone mineral density correlated with the lumbar (r = 0.64; P = .003) and thoracic (r, 0.51; P = .050) strength. At compression with torsion, CT SAP predictions of strength were moderately correlated with vertebral strength (r = 0.66; P = .018). At compression with torsion, bone mineral density was not correlated with spinal strength (thoracic and lumbar: r = 0.31 and r = 0.26, respectively; P = .539 and .610, respectively). The lytic focus size (range, 28%-41%) was not associated with vertebral strength. Conclusion CT SAP assessment of strength in vertebrae with lytic lesions correlated with the measured strength of female vertebral bodies. © RSNA, 2018 Online supplemental material is available for this article.

Random Electromyostimulation Promotes Osteogenesis and the Mechanical Properties of Rat Bones.

Exercise is often recommended as a promising non-pharmacologic countermeasure to prevent osteoporosis. However, elderly osteoporotic patients generally have physical fitness difficulties preventing them from performing effective and sustainable exercise. Electromyostimulation should be one effective modality for non-pharmacological prevention of osteoporosis without any voluntary physical movements. However, successful stimulation patterns remain controversial. As suggested by our previous in vitro studies, randomized timing of stimulation could be a candidate to maximize the osteogenic effect of electromyostimulation. In this study, the effects of random stimulation to the quadriceps on osteogenesis in the femurs were investigated using rats, in comparison with a periodic stimulation pattern. In histomorphometric assessments, both stimulation patterns demonstrated increases in bone formation rate either in cortical bone at the midshaft or in trabecular bone at the femoral neck on the stimulated side. However, maximum load and strain energy to failure were enhanced only by the random stimulation, on either the stimulated or non-stimulated side. It is concluded that randomized muscle stimulation has effective osteogenic capability at the stimulation site, similar to periodic stimulation; however, its effectiveness on mechanical properties is expandable to other non-stimulated sites.

The role of organic proteins on the crack growth resistance of human enamel.

With only 1% protein by weight, tooth enamel is the most highly mineralized tissue in mammals. The focus of this study was to evaluate contributions of the proteins on the fracture resistance of this unique structural material. Sections of enamel were obtained from the cusps of human molars and the crack growth resistance was quantified using a conventional fracture mechanics approach with complementary finite element analysis. In selected specimens the proteins were extracted using a potassium hydroxide treatment. Removal of the proteins resulted in approximately 40% decrease in the fracture toughness with respect to the fully proteinized control. The loss of organic content was most detrimental to the extrinsic toughening mechanisms, causing over 80% reduction in their contribution to the total energy to fracture. This degradation occurred by embrittlement of the unbroken bridging ligaments and consequent reduction in the crack closure stress. Although the organic content of tooth enamel is very small, it is essential to crack growth toughening by facilitating the formation of unbroken ligaments and in fortifying their potency. Replicating functions of the organic content will be critical to the successful development of bio-inspired materials that are designed for fracture resistance.

Physical activity as determinant of femoral neck strength relative to load in adult women: findings from the hip strength across the menopause transition study.

UNLABELLED: Our objective was to examine associations of physical activity in different life domains with peak femoral neck strength relative to load in adult women. Greater physical activity in each of the domains of sport, active living, home, and work was associated with higher peak femoral neck strength relative to load. INTRODUCTION: Our objective was to examine the associations of physical activity in different life domains with peak femoral neck strength relative to load in adult women. Composite indices of femoral neck strength integrate body size with femoral neck size and bone mineral density to gauge bone strength relative to load during a fall, and are inversely associated with incident fracture risk. METHODS: Participants were 1,919 pre- and early perimenopausal women from the Study of Women's Health Across the Nation. Composite indices of femoral neck strength relative to load in three failure modes (compression, bending, and impact) were created from hip dual-energy X-ray absorption scans and body size. Usual physical activity within the past year was assessed with the Kaiser Physical Activity Survey in four domains: sport, home, active living, and work. We used multiple linear regression to examine the associations. RESULTS: Greater physical activity in each of the four domains was independently associated with higher composite indices, adjusted for age, menopausal transition stage, race/ethnicity, Study of Women's Health Across the Nation study site, smoking status, smoking pack-years, alcohol consumption level, current use of supplementary calcium, current use of supplementary vitamin D, current use of bone-adverse medications, prior use of any sex steroid hormone pills or patch, prior use of depo-provera injections, history of hyperthyroidism, history of previous adult fracture, and employment status: standardized effect sizes ranged from 0.04 (p < 0.05) to 0.20 (p < 0.0001). CONCLUSIONS: Physical activity in each domain examined was associated with higher peak femoral neck strength relative to load in pre- and early perimenopausal women.

Physiological responses to spinal manipulation therapy: investigation of the relationship between electromyographic responses and peak force.

OBJECTIVE: It is believed that systematic modulation of spinal manipulative therapy (SMT) parameters should yield varying levels of physiological responses and eventually a range of clinical responses. However, investigation of SMT dose-physiological response relationship is recent and has mostly been conducted using animal or cadaveric models. The main objective of the present study is to investigate SMT dose-physiological response relation in humans by determining how different levels of force can modify electromyographic (EMG) responses to spinal manipulation. METHODS: Twenty-six participants were subjected to 2 trials of 4 different SMT force-time profiles using a servo-controlled linear actuator motor. Normalized EMG activity of paraspinal muscles (left and right muscles at level T6 and T8) was recorded during and after SMT, and EMG values were compared across the varying levels of force. RESULTS: Increasing the level of force yielded an increase in paraspinal muscle EMG activity during the thrust phase of SMT but also in the two 250-millisecond time windows after the spinal manipulation impulse. These muscle activations quickly attenuated (500 milliseconds after spinal manipulation impulse). CONCLUSION: The study confirmed the presence of a local paraspinal EMG response after SMT and highlighted the linear relationship between the SMT peak force and paraspinal muscle activation.

Supplementation with platelet-rich plasma improves the in vitro formation of tissue-engineered cartilage with enhanced mechanical properties.

PURPOSE: This study aimed to determine the effects of platelet-rich plasma (PRP) on the histologic, biochemical, and biomechanical properties of tissue-engineered cartilage. METHODS: Chondrocytes isolated from bovine metacarpal-phalangeal articular cartilage were seeded on top of a porous ceramic substrate (calcium polyphosphate [CPP]). Cultures were supplemented with fetal bovine serum (FBS), PRP, or platelet-poor plasma (PPP) at 5%. On day 5, the concentration was increased to 20%. PRP and PPP were obtained through centrifugation of whole blood withdrawn from a mature cow. After 2 weeks, samples (n = 8) were analyzed histologically, biochemically, and biomechanically. Data were analyzed using the Wilcoxon test (significance, P < .05). RESULTS: Chondrocytes cultured in 20% PRP formed thicker cartilage tissue (1.6 ± 0.2 mm) than did cells grown in 20% FBS (0.7 ± 0.008 mm; P = .002) and 20% PPP (0.8 ± 0.2 mm; P = .03). Cartilage tissue generated in the presence of 20% PRP had a greater equilibrium modulus of 38.1 ± 3.6 kPa versus 15.6 ± 1.5 kPa (P = .0002) for 20% PPP and 20.4 ± 3.5 kPa (P = .007) for 20% FBS. Glycosaminoglycan (GAG) content was increased in tissues formed in 20% PRP (176 ± 18.8 µg GAG/mg) compared with those grown in 20% FBS (112 ± 10.6 µg GAG/mg; P = .01) or 20% PPP (131.5 ± 14.8 µg GAG/mg; P = .11). Hydroxyproline content was similar whether the media was supplemented with 20% PRP (8.7 ± 0.9 µg/mg), 20% FBS (7.6 ± 0.9 µg/mg; P = .37), or 20% PPP (6.4 ± 1 µg/mg; P = .28). DNA content was similar in all tissues whether formed in 20% PRP (11.9 ± 3.5 µg/mg), 20% FBS (9.3 ± 2.5 µg/mg; P = .99), or 20% PPP (7.2 ± 1.3 µg/mg; P = .78). Immunostained samples showed prevalence of type II collagen in tissues formed in the presence of 20% PRP. CONCLUSIONS: The presence of PRP in the culture media enhances the in vitro formation of cartilage, with increased GAG content and greater compressive mechanical properties, while maintaining characteristics of hyaline phenotype. CLINICAL RELEVANCE: Understanding the in vitro effects of PRP on tissue-engineered cartilage may lead to the creation of engineered cartilage tissue with enhanced properties suitable for cartilage repair.

The combination of structural parameters and areal bone mineral density improves relation to proximal femur strength: an in vitro study with high-resolution peripheral quantitative computed tomography.

The aim of this study was to assess structural indices from high-resolution peripheral quantitative computed tomography (HR-pQCT) images of the human proximal femur along with areal bone mineral density (aBMD) and compare the relationship of these parameters to bone strength in vitro. Thirty-one human proximal femur specimens (8 men and 23 women, median age 74 years, range 50-89) were examined with HR-pQCT at four regions of interest (femoral head, neck, major and minor trochanter) with 82 µm and in a subgroup (n = 17) with 41 µm resolution. Separate analyses of cortical and trabecular geometry, volumetric BMD (vBMD), and microarchitectural parameters were obtained. In addition, aBMD by dual-energy X-ray absorptiometry (DXA) was performed at conventional hip regions and maximal compressive strength (MCS) was determined in a side-impact biomechanical test. Twelve cervical and 19 trochanteric fractures were confirmed. Geometry, vBMD, microarchitecture, and aBMD correlated significantly with MCS, with Spearman's correlation coefficients up to 0.77, 0.89, 0.90, and 0.85 (P < 0.001), respectively. No differences in these correlations were found using 41 µm compared to 82 µm resolution. In multiple regression analysis of MCS, a combined model (age- and sex-adjusted) with aBMD and structural parameters significantly increased R (2) values (up to 0.90) compared to a model holding aBMD alone (R (2) up to 0.78) (P < 0.05). Structural parameters and aBMD are equally related to MCS, and both cortical and trabecular structural parameters obtained from HR-pQCT images hold information on bone strength complementary to that of aBMD.

Simple techniques to increase the production yield and enhance the quality of organic rice bran oils.

This study develops simple techniques for increasing production yield and refining of crude RBO (CRBO). It was found that pre-heating of rice bran by hot air oven to reach 60°C before being extracted by screw press machine increased the yield from 4.8 to 8.3%w/w. This paper suggested three simple steps for refining of organic CRBO: (1) filtering using filter papers (2) sedimentation by adding 4%w/v fuller's earth and (3) bleaching by running through a packed column of activated carbon. These steps significantly enhanced the qualities of RBO when compared to CRBO before treatment. It was found that the lightness of oil as indicated by color value (L*) increased from 22.8 to 28.7, gum and wax decreased from 3.6 to 1.3%w/w. However, the simple refining method had no effect on peroxide value and free fatty acid content. Moreover, it slightly induced the loss of oryzanol content from 2.8 to 2.2%w/w.

Increased microstructural variability is associated with decreased structural strength but with increased measures of structural ductility in human vertebrae.

The lack of accuracy in the prediction of vertebral fracture risk from average density measurements, all external factors being equal, may not just be because bone mineral density (BMD) is less than a perfect surrogate for bone strength but also because strength alone may not be sufficient to fully characterize the structural failure of a vertebra. Apart from bone quantity, the regional variation of cancellous architecture would have a role in governing the mechanical properties of vertebrae. In this study, we estimated various microstructural parameters of the vertebral cancellous centrum based on stereological analysis. An earlier study indicated that within-vertebra variability, measured as the coefficient of variation (COV) of bone volume fraction (BV/TV) or as COV of finite element-estimated apparent modulus (E(FE)) correlated well with vertebral strength. Therefore, as an extension to our earlier study, we investigated (i) whether the relationships of vertebral strength found with COV of BV/TV and COV of E(FE) could be extended to the COV of other microstructural parameters and microcomputed tomography-estimated BMD and (ii) whether COV of microstructural parameters were associated with structural ductility measures. COV-based measures were more strongly associated with vertebral strength and ductility measures than average microstructural measures. Moreover, our results support a hypothesis that decreased microstructural variability, while associated with increased strength, may result in decreased structural toughness and ductility. The current findings suggest that variability-based measures could provide an improvement, as a supplement to clinical BMD, in screening for fracture risk through an improved prediction of bone strength and ductility. Further understanding of the biological mechanisms underlying microstructural variability may help develop new treatment strategies for improved structural ductility.

A comparison of the torsional stiffness of the lumbar spine in flexion and extension.

OBJECTIVE: The main mechanism of injury to the spine is torsion especially when coupled with compression. In this study, the in vitro torsional stiffness of the lumbar spine segments is compared in flexion and extension positions by cyclic and failure testing. METHODS: Fifteen lumbar spines were sectioned from fresh cadavers into 15 L2/3 and 15 L45 motion segments. Each vertebral segment was then potted superiorly and inferiorly in polymethylmethacrylate, effectively creating a bone-disk-bone construct. The potted spinal segments were mounted in a mechanical testing system, preloaded in compression to 300 N, and axially rotated to 3 degrees in both directions at a load rate of 1 degrees /s. This was done over 3 cycles for each motion segment in the flexion and extension positions. Each specimen was then tested to torsional failure in either flexion or extension. Stiffness, torque, and energy were determined from cyclic and failure testing. RESULTS: The results showed that in all cases of cyclic testing, the higher segment extension resulted in higher torsional stiffness. In relative extension, the lumbar specimens were stiffer, generated higher torque values, and generally absorbed more energy than the relative flexion condition. There were no differences found in loading direction or failure testing. CONCLUSIONS: Increasing the effective torsional stiffness of the lumbar spine in extension could provide a protective mechanism against interverbral disk injury. Restoration of segmental extension through increasing the lumbar lordosis may decrease the strain and reinjury of the joints, which can help reduce the extent of pain in the lumbar spine.

Assessment and classification of mechanical strength components of human femur trabecular bone using texture analysis and neural network.

In this work the mechanical strength components of human femur trabecular bone are analyzed and classified using planar radiographic images and neural network. The mechanical strength regions such as Primary Compressive, Primary Tensile, Secondary Tensile and Ward Triangle in femur trabecular bone images (N = 100) are delineated by semi-automatic image processing procedure. First and higher order texture parameters and parameters such as apparent mineralization and total area associated with the strength regions are derived for normal and abnormal images. The statistically derived significant parameters corresponding to the primary strength regions are fed to the neural network for training and validation. The classifications are carried out using feed forward network that is trained with standard back propagation algorithm. Results demonstrate that the apparent mineralization of normal samples is always high as (71%) compared to abnormal samples (64%). Entropy shows a high value (7.3) for normal samples and variation between the mean intensity and apparent mineralization for the primary strength zone is statistically significant (p < 0.0005). The classified outputs are validated by sensitivity and specificity measurements and are found to be 66.66% and 80% respectively. Further it appears that it is possible to differentiate normal and abnormal samples from the conventional radiographic images. As trabecular architecture in the human femur is an important factor contributing to bone strength, the procedure adopted here could be a useful supplement to the clinical observations for bone loss and fracture risk.

Extrusion of pea starch containing lysozyme and determination of antimicrobial activity.

Pea starch, which has inherently good gel strength, was used as the source material for manufacturing a biodegradable and bioactive packaging material. Extrudates containing 99% pea starch and 1% lysozyme were produced under various extrusion conditions (high and low shear screw configurations, 30% to 40% moisture contents, 70 to 150 degrees C die temperatures). The physical and mechanical properties of the extrudates were determined through various expansion indices, piece and cell wall solid density, compression, and 3-point bending tests. The expansion of extrudates increased with an increase in die temperature, whereas increasing moisture content had the opposite effect. Extrudate densities decreased as extrusion temperature increased, whereas lower moisture content in the extrudate dough decreased extrudate densities. The elastic modulus and fracture strengths were highly correlated in a power-law fashion to relative density, showing that the mechanical properties of extrudates were dependent on solid density and foam structure. Up to 48% of the initial lysozyme activity was recovered from the extruded pea starch matrix. The lysozyme released from extrudates showed an inhibition zone against Brochotrix thermosphacta B2. Extruded pea starch matrix containing lysozyme has potential application as an edible and biodegradable packaging material with antimicrobial activity.

Treatment of cavernous sinus dural arteriovenous fistulae by external manual carotid compression.

OBJECTIVE: External manual carotid compression is a noninvasive method to treat cavernous sinus (CS) dural arteriovenous fistulae (DAVF). We studied a group of patients with CS-DAVF to identify what factors made complete resolution of their clinical symptoms and closure of the DAVF on magnetic resonance angiography (MRA) by compression therapy possible. METHODS: We treated 23 patients with CS-DAVF without cortical venous drainage or a recent decline in visual acuity by compression therapy. All were followed up by magnetic resonance angiography at 1, 3, 6, and 12 months after treatment and the characteristics of the imaging findings, their neurological symptoms, and the patterns of symptom improvement were examined. RESULTS: In Group A (n = 8), complete resolution was achieved by manual carotid compression. In the other 15 patients (Group B), complete resolution was not obtained. Group B manifested significantly higher ocular pressure and a significantly longer interval between symptom onset and compression treatment. In Group A, venous drainage was via the superior orbital vein with or without involvement of the inferior petrosal sinus. Closure of the CS-DAVF occurred within 4.1 months after the start of treatment. In three patients, symptom improvement progressed steadily and gradually. The other five patients with complete resolution experienced transient worsening of their symptoms at 2 to 4 months after the start of treatment and symptom resolution occurred within 4 to 7 months. CONCLUSION: We identified lower ocular pressure, a shorter interval between symptom onset and compression treatment, and venous drainage solely via the superior orbital vein without involvement of the inferior petrosal sinus as the factors in our CS-DAVF patients that made complete resolution by manual carotid compression possible.

Electrically induced muscle contractions influence bone density decline after spinal cord injury.

STUDY DESIGN: Longitudinal repeated-measures; within-subject control. OBJECTIVE: We examined the extent to which an isometric plantar flexion training protocol attenuates bone loss longitudinally after SCI. SUMMARY OF BACKGROUND DATA: After spinal cord injury (SCI), bone mineral density (BMD) of paralyzed extremities rapidly declines, likely because of loss of mechanical loading of bone via muscle contractions. METHODS: Six individuals with complete paralysis began a 3-year unilateral plantar flexor muscle activation program within 4.5 months after SCI. The opposite limb served as a control. Compliance with recommended dose was > 80%. Tibia compressive force was > 140% of body weight. RESULTS: Bilateral hip and untrained tibia BMD declined significantly over the course of the training. Lumbar spine BMD showed minimal change. Percent decline in BMD (from the baseline condition) for the trained tibia (approximately 10%) was significantly less than the untrained tibia (approximately 25%) (P < 0.05). Trained limb percent decline in BMD remained steady over the first 1.5 years of the study (P < 0.05). CONCLUSIONS: Compressive loads of approximately 1 to 2 times body weight, induced by muscle contractions, partially prevent the loss of BMD after SCI. Future studies should establish dose-response curves for attenuation of bone loss after SCI.

Interrelationship of trabecular mechanical and microstructural properties in sheep trabecular bone.

The ability to evaluate fracture risk at an early time point is essential for improved prognostics as well as enhanced treatment in cases of bone loss such as from osteoporosis. Improving the diagnostic ability is inherent upon both high-resolution non-invasive imaging, and a thorough understanding of how the derived indices of structure and density relate to its true mechanical behavior. Using sheep femoral trabecular bone with a range of strength, the interrelationship of mechanical and microstructural parameters was analyzed using multi-directional mechanical testing and micro-computed tomography. Forty-five cubic trabecular bone samples were harvested from 23 adult female sheep, some of whom had received hind-limb vibratory stimuli over the course of 2 years with consequently enhanced mechanical properties. These samples were pooled into a low, medium, or high strength group for further analysis. The findings show that microCT indices that are structural in nature, e.g., structural model index (SMI) (r2=0.85, p<0.0001) is as good as more density oriented indices like bone volume/total volume (BV/TV) (r2=0.81, p<0.0001) in predicting the ultimate strength of a region of trabecular bone. Additionally, those indices more related to global changes in trabecular structure such as connectivity density (ConnD) or degree of anisotropy (DA) are less able to predict the mechanical properties of bone. Interrelationships of trabecular indices such as trabecular number (TbN), thickness (TbTh), and spacing (TbSp) provide clues as to how the trabecular bone will remodel to ultimately achieve differences in the apparent mechanical properties. For instance, the analysis showed that a loss of bone primarily affects the connectedness and overall number of trabeculae, while increased strength results in an increase of the overall thickness of trabeculae while not improving the connectedness. Certainly, the microCT indices studied are able to predict the bulk mechanical properties of a trabecular ROI well, leaving unaccounted only about 15-20% of its inherent variability. Diagnostically, this implies that future work on the early prediction of fracture risk should continue to explore the role of bone quality as the key factors or as an adjuvant to bone quantity (e.g., apparent density).

Mechanical properties of desiccated ragweed pollen grains determined by micromanipulation and theoretical modelling.

The mechanical properties of desiccated ragweed pollen grains were determined using a micromanipulation technique and a theoretical model. Single pollen grains with a diameter of approximately 20 microm were compressed and held, compressed and released, and compressed to rupture at different speeds between two parallel surfaces. Simultaneously, the force being imposed on the pollen grains was measured. It has been found that the rupture force of pollen grains increased linearly with their displacement at rupture on average, but was independent of their diameter. The mean rupture force was 1.20 +/- 0.03 mN, and mean deformation (the ratio between the displacement and diameter) at rupture was 22 +/- 0.6%. Single pollen grains were modeled as a capsule with a core full of air and a non permeable wall. A constitutive equation based on Hookean law was used to determine the mechanical property parameters Eh (product of the Young's modulus and wall thickness), and the mean value of Eh of desiccated pollen gains was estimated to be 1653 +/- 36 N/m.

Comparison of biomechanical and biochemical properties of cartilage from human knee and ankle pairs.

Cartilage was obtained from eight matched knee (tibiofemoral and femoropatellar) and ankle (talocrural) joints of five different donors (both left and right from donors 14, 22, and 38 years of age, and left only from donors 31 and 45 years of age) within 24 hours of death. All cartilage was graded as normal by the macroscopic visual Collins' scale and the histological Mankin scale. Cylindrical disks of cartilage were harvested from 10 sites within the tibiofemoral and femoropatellar joint surfaces and four sites within the talocrural joint, and uniaxial confined compression measurements were performed to quantify a spectrum of physical properties including the equilibrium modulus, hydraulic permeability, dynamic stiffness, streaming potential, electrokinetic coupling coefficient, and electrical conductivity. Matched specimens from the same 14 sites were used for complementary measurements of biochemical composition and molecular interaction, including water content, hypotonic swelling behavior, and sulfated glycosaminoglycan and collagen contents. In comparison of the top 1-mm slices of talar cartilage with the top 1-mm of tibiofemoral cartilage, the talar cartilage appeared denser with a higher sulfated glycosaminoglycan content, lower water content, higher equilibrium modulus and dynamic stiffness, and lower hydraulic permeability. The equilibrium modulus increased with increasing sulfated glycosaminoglycans per wet weight and decreased with increasing water content for all joint surfaces. Multiple linear regression showed that greater than 80% of the variation in the equilibrium modulus could be accounted for by variations in the biochemical parameters (water content, sulfated glycosaminoglycans/wet weight, and hydroxyproline content/wet weight) for each joint surface. Nonhomogeneous depth-dependent changes in the physical properties and biochemical composition of full-thickness distal femoral cartilage were consistent with previous reports. Since the compressive deformation of cartilage during cyclic loading is confined to the more superficial regions, the differences in properties of the upper regions of the talar compared with tibiofemoral or femoropatellar cartilage may be important in the etiology of osteoarthritis.