Characterization of biological materials with their elasto-mechanical properties is considered essential for understanding their nature. In addition, elasto-mechanical studies at the macroscale are frequently used to determine these characteristics by a resistance measurement such as the Magness-Taylor penetration test or compression test using an Instron Universal Mechanical Testing Machine. In this regard, the atomic force microscopy (AFM) was presented as a new method for identifying the alterations of elasto-mechanical properties at a nanoscale. Therefore, the present study estimated the elastic modulus and stiffness of the cell walls which were isolated from the banana mesocarp with AFM-based nanoindentation. Then, the elastic modulus of a cell and stiffness were determined by analyzing the force-separation curves using the theory of Hertz and the mechanics of Sneddon. Using two tips of the distinct radius of the curvature (10 and 10,000 nm), it was revealed that the tip geometry significantly affected the measured elasto-mechanical properties. Further, the elastic modulus was around 95 ± 45 and 18.5 ± 12.5 kPa for the sharper tip (R = 10 nm) and a bead (R = 10,000 nm) tips, respectively. Furthermore, a large variability was considered regarding the elasto-mechanical property (>100%) among the cells which were sampled from the same region in the fruit. Therefore, the AFM can be highly suitable for evaluating the structure-related properties of biological materials at the cellular and subcellular scales by combining nano elasto-mechanical properties with topography imaging.

Natural biopolymer-based hydrogels especially agarose and collagen gels, considering their biocompatibility with cells and their capacity to mimic biological tissues, have widely been used for in-vitro experiments and tissue engineering applications in recent years; nevertheless their mechanical properties are not always optimal for these purposes. Regarding the importance of the mechanical properties of hydrogels, many mechanical characterization studies have been carried out for such biopolymers. In this work, we have focused on understanding the mechanical role of agarose and collagen concentration on the hydrogel strength and elastic behavior. In this direction, Amirkabir Magnetic Bead Rheometry (AMBR) characterization device equipped with an optimized electromagnet, was designed and constructed for the measurement of hydrogel mechanical properties. The operation of AMBR set-up is based on applying a magnetic field to actuate magnetic beads in contact with the gel surface in order to actuate the gel itself. In simple terms the magnetic beads leads give rise to mechanical shear stress on the gel surface when under magnetic influence and together with the associated bead-gel displacement it is possible to calculate the hydrogel shear modulus. Agarose and Collagen gels with respectively 0.2-0.6 wt % and 0.2-0.5 wt % percent concentrations were prepared for mechanical characterization in terms of their shear modulus. The shear modulus values for the different percent concentrations of the agarose gel were obtained in the range 250-650 Pa, indicating the shear modulus increases by increasing in the agar gel concentration. In addition to this, the values of shear modulus for the collagen gel increase as function of concentration in the range 240-520 Pa in accordance with an approximately linear relationship between collagen concentration and gel strength.

Aim of the study: To evaluate changes in the elasticity of the coracohumeral ligament in patients with adhesive capsulitis of the shoulder treated with ultrasound-guided rotator interval injections. Methods: Shear wave elastography was used to evaluate elasticity of the coracohumeral ligament in symptomatic and asymptomatic shoulders in the shoulder-neutral position and 30° external rotation. A total of 24 shoulders were assessed. Symptomatic shoulders were treated with targeted steroid injection via the rotator interval and manipulation under local anaesthetic block. Follow-up assessment of the elasticity of the coracohumeral ligament was obtained at 10 weeks post-injection. Results: In all subjects, the coracohumeral ligament elastic modulus was larger at 30° external rotation than in the neutral position. In patients with adhesive capsulitis, the coracohumeral ligament thickness and elastic modulus was significantly greater in the symptomatic shoulder in the neutral position and 30° ER. Treated patients had an excellent response with improved Oxford Shoulder Score and reduced visual analogue scale pain scores. Median Oxford Shoulder Score was 13.5 pre-injection and 34 at 10 weeks post-injection. Median visual analogue scale pain scores measured 8.5 pre-injection, 3.5 at 1 day, 2 at 1 week, and 2.5 at 10 weeks. Improved Oxford Shoulder Score and visual analogue scale pain score was associated with a trend to normalisation of the elastic modus of the coracohumeral ligament. Conclusion: In patients with adhesive capsulitis of the shoulder, shear wave elastography demonstrated the coracohumeral ligament is stiffer in the symptomatic shoulder than in the unaffected shoulder. Treatment with the ultrasound-guided rotator interval injection is associated with improved Oxford Shoulder Score, reduced visual analogue scale pain scores, and reduced stiffness in the coracohumeral ligament.

Recognizing that breast cancers present as firm, stiff lesions, the foundation of breast magnetic resonance elastography (MRE) is to combine tissue stiffness parameters with sensitive breast MR contrast-enhanced imaging. Breast MRE is a non-ionizing, cross-sectional MR imaging technique that provides for quantitative viscoelastic properties, including tissue stiffness, elasticity, and viscosity, of breast tissues. Currently, the technique continues to evolve as research surrounding the use of MRE in breast tissue is still developing. In the setting of a newly diagnosed cancer, associated desmoplasia, stiffening of the surrounding stroma, and necrosis are known to be prognostic factors that can add diagnostic information to patient treatment algorithms. In fact, mechanical properties of the tissue might also influence breast cancer risk. For these reasons, exploration of breast MRE has great clinical value. In this review, we will: (1) address the evolution of the various MRE techniques; (2) provide a brief overview of the current clinical studies in breast MRE with interspersed case examples; and (3) suggest directions for future research.

Structural and chemical deterioration and its impact on cell wall mechanics were investigated for visually intact cell walls (VICWs) in waterlogged archaeological wood (WAW). Cell wall mechanical properties were examined by nanoindentation without prior embedding. WAW showed more than 25% decrease of both hardness and elastic modulus. Changes of cell wall composition, cellulose crystallite structure and porosity were investigated by ATR-FTIR imaging, Raman imaging, wet chemistry, 13C-solid state NMR, pyrolysis-GC/MS, wide angle X-ray scattering, and N2 nitrogen adsorption. VICWs in WAW possessed a cleavage of carboxyl in side chains of xylan, a serious loss of polysaccharides, and a partial breakage of β-O-4 interlinks in lignin. This was accompanied by a higher amount of mesopores in cell walls. Even VICWs in WAW were severely deteriorated at the nanoscale with impact on mechanics, which has strong implications for the conservation of archaeological shipwrecks.

BACKGROUND: Interest around carbon/PEEK plates and nails has been raising. The elastic modulus close to the bone, the high load-carrying capacity and radiolucency make CFR/PEEK materials a potential breakthrough. In the literature, there are abundant data about CFR/PEEK plates in the treatment of proximal humerus, distal radius and distal fibula fractures. In patients affected by bone metastasis, CFR/PEEK nails were proved effective and safe with 12 months of follow-up. Very little is known about performances of CFR/PEEK nails in patients affected by other pathologies.
OBJECTIVE: The aim of the study was to evaluate safety and efficacy of CFR/PEEK nails in the treatment of various pathological conditions. It was also investigated whatever radiolucency of this nails could lead to a more objective evaluation of bone callus or disease site.
METHODS: In the study group were included 20 patients (22 bone segments) who underwent CFR/PEEK nail implantation (eight humerus, one tibia, nine femur and four knee arthrodesis). They were affected by pathological fractures, and in four cases, they required an arthrodesis of the knee. They were retrospectively evaluated considering nail failures and bone callus or disease progression (RUSH scores). Mean follow-up time was 11 months (min 6.8-max 20.3). In the control group were included patients treated with titanium nails in the same institution for the same pathologies. An interclass correlation coefficient (ICC) analysis was performed in both groups considering RUSH scores by two expert surgeon from two institution to assess whether radiolucency could lead to a more objective evaluation of disease or bone callus site.
RESULTS: The ICC of mean values between RUSH scores was 0.882 (IC 95%: 0.702-0.953) in the CFR/PEEK group, while it was 0.778 (IC 95%: 0.41-0.91) in the titanium group. Observers\' evaluation showed a significantly higher obscuration by titanium nails than by CFR/PEEK nails. No osteosynthesis failures were reported in both groups.
CONCLUSIONS: Our results confirm the safety of CFR/PEEK nails in the short-medium term. The radiolucency of these materials led our observers to perform more objective evaluations of bone callus formation or disease progression compared to the titanium group given the higher ICC.
METHODS: III Case-control therapeutic study.

The aim of the study was to evaluate the spatial variations in the biomechanical properties of the bone around the implants retrieved from human subjects due to fixture head fracture after almost 20 years of loading. The implant-in-bone specimens were prepared for the histomorphometry and nanoindentation test to measure the bone-to-implant contact ratio (BIC ratio) and elastic modulus (E) of peri-implant bone. The indentations were performed in the up, center, down, and away regions of the bone tissues within all the thread spaces. The BIC ratios were 91.0% for Patient #1 and 95.8% for Patient #2. The E values assessed from the up region within the thread spaces were significantly higher than those measured from the center region. The elastic properties assessed from center and down regions within the thread spaces were similar to those assessed from the away region. The representative E values showed no significant thread-dependent linear trend. Within the limitation of this study, the peri-implant bone tissue showed spatial variation of its elastic modulus after long-term functioning.

OBJECTIVE: We investigated how heterogeneity in material stiffness affects structural stiffness in the cercopithecid mandibular cortical bone. We assessed (1) whether this effect changes the interpretation of interspecific structural stiffness variation across four primate species, (2) whether the heterogeneity is random, and (3) whether heterogeneity mitigates bending stress in the jaw associated with food processing.
METHODS: The sample consisted of Taï Forest, Cote d\'Ivoire, monkeys: Cercocebus atys, Piliocolobus badius, Colobus polykomos, and Cercopithecus diana. Vickers indentation hardness samples estimated elastic moduli throughout the cortical bone area of each coronal section of postcanine corpus. For each section, we calculated maximum area moment of inertia, Imax (structural mechanical property), under three models of material heterogeneity, as well as spatial autocorrelation statistics (Moran\'s I, IMORAN ).
RESULTS: When the model considered material stiffness variation and spatial patterning, Imax decreased and individual ranks based on structural stiffness changed. Rank changes were not significant across models. All specimens showed positive (nonrandom) spatial autocorrelation. Differences in IMORAN were not significant among species, and there were no discernable patterns of autocorrelation within species. Across species, significant local IMORAN was often attributed to proximity of low moduli in the alveolar process and high moduli in the basal process.
CONCLUSIONS: While our sample did not demonstrate species differences in the degree of spatial autocorrelation of elastic moduli, there may be mechanical effects of heterogeneity (relative strength and rigidity) that do distinguish at the species or subfamilial level (i.e., colobines vs. cercopithecines). The potential connections of heterogeneity to diet and/or taxonomy remain to be discovered.

Impaired neck muscle function leads to disability in individuals with chronic whiplash-associated disorder (WAD), but diagnostic tools are lacking. In this study, deformations and deformation rates were investigated in five dorsal neck muscles during 10 arm elevations by ultrasonography with speckle tracking analyses. Forty individuals with chronic WAD (28 women and 12 men, mean age = 37 y) and 40 healthy controls matched for age and sex were included. The WAD group had higher deformation rates in the multifidus muscle during the first (p < 0.04) and 10th (only women, p < 0.01) arm elevations compared with the control group. Linear relationships between the neck muscles for deformation rate (controls: R(2) = 0.24-0.82, WAD: R(2) = 0.05-0.74) and deformation of the deepest muscles (controls: R(2) = 0.61-0.32, WAD: R(2) = 0.15-0.01) were stronger for women in the control group versus women with WAD, indicating there is altered interplay between dorsal neck muscles in chronic WAD.

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.