Animation of in vitro biomechanical tests.

Interdisciplinary communication of three-dimensional kinematic data arising from in vitro biomechanical tests is challenging. Complex kinematic representations such as the helical axes of motion (HAM) add to the challenge. The difficulty increases further when other quantities (i.e. load or tissue strain data) are combined with the kinematic data. The objectives of this study were to develop a method to graphically replay and animate in vitro biomechanical tests including HAM data. This will allow intuitive interpretation of kinematic and other data independent of the viewer's area of expertise. The value of this method was verified with a biomechanical test investigating load-sharing of the cervical spine. Three 3.0 mm aluminium spheres were glued to each of the two vertebrae from a C2-3 segment of a human cervical spine. Before the biomechanical tests, CT scans were made of the specimen (slice thickness=1.0 mm and slice spacing=1.5 mm). The specimens were subjected to right axial torsion moments (2.0 Nm). Strain rosettes mounted to the anterior surface of the C3 vertebral body and bilaterally beneath the facet joints on C3 were used to estimate the force flow through the specimen. The locations of the aluminium spheres were digitised using a space pointer and the motion analysis system. Kinematics were measured using an optoelectronic motion analysis system. HAMs were calculated to describe the specimen kinematics. The digitised aluminium sphere locations were used to match the CT and biomechanical test data (RMS errors between the CT and experimental points were less than 1.0 mm). The biomechanical tests were "replayed" by animating reconstructed CT models in accordance with the recorded experimental kinematics, using custom software. The animated test replays allowed intuitive analysis of the kinematic data in relation to the strain data. This technique improves the ability of experts from disparate backgrounds to interpret and discuss this type of biomechanical data.     

Biomechanical Characteristics of Hand Coordination in Grasping Activities of Daily Living

Hand coordination can allow humans to have dexterous control with many degrees of freedom to perform various tasks in daily living. An important contributing factor to this important ability is the complex biomechanical architecture of the human hand. However, drawing a clear functional link between biomechanical architecture and hand coordination is challenging. It is not understood which biomechanical characteristics are responsible for hand coordination and what specific effect each biomechanical characteristic has. To explore this link, we first inspected the characteristics of hand coordination during daily tasks through a statistical analysis of the kinematic data, which were collected from thirty right-handed subjects during a multitude of grasping tasks. Then, the functional link between biomechanical architecture and hand coordination was drawn by establishing the clear corresponding causality between the tendinous connective characteristics of the human hand and the coordinated characteristics during daily grasping activities. The explicit functional link indicates that the biomechanical characteristic of tendinous connective architecture between muscles and articulations is the proper design by the Creator to perform a multitude of daily tasks in a comfortable way. The clear link between the structure and the function of the human hand also suggests that the design of a multifunctional robotic hand should be able to better imitate such basic architecture.     

Verification of a virtual fields method to extract the mechanical properties of human optic nerve head tissues in vivo

We aimed to verify a custom virtual fields method (VFM) to estimate the patient-specific biomechanical properties of human optic nerve head (ONH) tissues, given their full-field deformations induced by intraocular pressure (IOP). To verify the accuracy of VFM, we first generated ‘artificial’ ONH displacements from predetermined (known) ONH tissue biomechanical properties using finite element analysis. Using such deformations, if we are able to match back the known biomechanical properties, it would indicate that our VFM technique is accurate. The peripapillary sclera was assumed anisotropic hyperelastic, while all other ONH tissues were considered isotropic. The simulated ONH displacements were fed into the VFM algorithm to extract back the biomechanical properties. The robustness of VFM was also tested against rigid body motions and noise added to the simulated displacements. Then, the computational speed of VFM was compared to that of a gold-standard stiffness measurement method (inverse finite element method or IFEM). Finally, as proof of principle, VFM was applied to IOP-induced ONH deformation data (obtained from one subject’s eye imaged with OCT), and the biomechanical properties of the prelamina and lamina cribrosa (LC) were extracted. From given ONH displacements, VFM successfully matched back the biomechanical properties of ONH tissues with high accuracy and efficiency. For all parameters, the percentage errors were less than 0.05%. Our method was insensitive to rigid body motions and was also able to recover the material parameters in the presence of noise. VFM was also found 125 times faster than the gold-standard IFEM. Finally, the estimated shear modulus for the prelamina and the LC of the studied subject’s eye were 33.7 and 63.5 kPa, respectively. VFM may be capable of measuring the biomechanical properties of ONH tissues with high speed and accuracy. It has potential in identifying patient-specific ONH biomechanical properties in the clinic if combined with optical coherence tomography.     

动力加压髋螺钉对股骨上段生物力学特征性的影响

目的：探讨股骨上端骨折,以动力加压髋螺钉进行骨固定治疗,骨折愈合后,取出动力加压髋螺钉以后的股骨上段与完整的股骨上段的生物力学特性相比较,为临床内固定取出术后功能锻炼的强度提供量化依据。方法：收集8具新鲜尸体股骨标本进行实验应力分析,分别测定完整股骨上段和动力加压髋螺钉取出后股骨上段的力学特性改变。结果：动力加压髋螺钉取出术后股骨上段的力学特性与完整股骨上段的力学特性相比有显著的差异（P＜0．01）。结论：股骨上端骨折如果以动力加压髋螺钉为治疗手段,在骨折愈合取出内固定后,功能锻炼只能控制在慢速步行水平,不能进行奔跑、跳跃等活动,以防止再骨折等并发症的发生。     

The effect of chemical cleansing procedures combined with peracetic acid-ethanol sterilization on biomechanical properties of cortical bone.

Peracetic acid-ethanol sterilization (PES) with a preceding delipidation step is an effective sterilization method for allograft bone, but its influence on biomechanical properties of bone has not been studied. The aim of this study was to evaluate the effects of different incubation times of water, hydrogen peroxide and alcohol cleansing procedures combined with PES on biomechanical properties of freeze-dried cortical bone. These effects were studied by performing three-point bending tests on cortical samples. The lyophilized cortical samples were rehydrated prior to mechanical testing. The bending strength and the absorbed energy of the processed cortical samples were increased slightly but the Young's modulus was decreased compared to unprocessed samples. However, when the residual moisture content of the processed cortical samples was reduced from <5% to 0% all the biomechanical properties studied were significantly decreased. Hexane elution was used to determine the residual fat content of the processed cortical bone. Reducing the incubation time in cleansing had no effect on the residual fat content of the bone samples. Our in vitro study indicates that the cleansing procedure proposed combined with PES affects the biomechanical properties of cortical bone only on a limited scale.     

Numerical analysis of the influence of nucleus pulposus removal on the biomechanical behavior of a lumbar motion segment

Nucleus replacement was deemed to have therapeutic potential for patients with intervertebral disc herniation. However, whether a patient would benefit from nucleus replacement is technically unclear. This study aimed to investigate the influence of nucleus pulposus (NP) removal on the biomechanical behavior of a lumbar motion segment and to further explore a computational method of biomechanical characteristics of NP removal, which can evaluate the mechanical stability of pulposus replacement. We, respectively, reconstructed three types of models for a mildly herniated disc and three types of models for a severely herniated disc based on a L4–L5 segment finite element model with computed tomography image data from a healthy adult. First, the NP was removed from the herniated disc models, and the biomechanical behavior of NP removal was simulated. Second, the NP cavities were filled with an experimental material (Poisson's ratio = 0.3; elastic modulus = 3 MPa), and the biomechanical behavior of pulposus replacement was simulated. The simulations were carried out under the five loadings of axial compression, flexion, lateral bending, extension, and axial rotation. The changes of the four biomechanical characteristics, i.e. the rotation degree, the maximum stress in the annulus fibrosus (AF), joint facet contact forces, and the maximum disc deformation, were computed for all models. Experimental results showed that the rotation range, the maximum AF stress, and joint facet contact forces increased, and the maximum disc deformation decreased after NP removal, while they changed in the opposite way after the nucleus cavities were filled with the experimental material.     

Computational biomechanical analysis of postoperative inferior tibiofibular syndesmosis: a modified modeling method

To analyze the biomechanical effect of syndesmotic screw through three and four cortices, a total of 12 finite element models simulating healthy ankles, tibiofibular syndesmosis injured ankles, and post-operative ankles by screw fixations through three or four cortices were built. A set of biomechanical data were obtained to find that screw fixation methods for inferior tibiofibular syndesmosis can help recover most of the biomechanical relations of the ankle especially the tricortical fixation, while the screw of quadricortical fixation bear more stress than the tricortical fixation. The modeling method for finite element models was also modified for saving more time and realizing personalized modeling for clinical application.     

镉染毒对雄性大鼠骨生物力学性能的影响

目的探讨镉（Cd）对大鼠股骨和腰椎生物力学性能的影响。方法 24只8周龄雄性SD大鼠随机分成4组：对照组,皮下注射0.5 mL生理盐水;实验组,染毒剂量分别为0.1 mg Cd/（kg.bw）（低剂量组）,0.5 mgCd/（kg.bw）（中剂量组）和1.5 mg Cd/（kg.bw）（高剂量组）,每周根据体重调整注射量。染毒后第12周,收集全血、腰椎及股骨,分别用于血镉测定、骨镉测定、骨密度测定及生物力学测定。结果染毒组大鼠体内血镉及骨镉水平明显高于对照组,差异有统计学意义（P〈0.05）;中、高剂量染毒组大鼠骨密度较对照组显著下降（P〈0.05）;染毒组大鼠股骨和腰椎生物力学性能较对照组有不同程度的的降低,其中高剂量染毒组大鼠股骨生物力学性能的下降和对照组相比差异有显著性（P〈0.01）;中、高剂量组大鼠腰椎生物力学性能和对照组相比有显著下降,差异有统计学意义（P〈0.01）。结论镉影响大鼠股骨和腰椎的生物力学性能,并且腰椎较股骨更为敏感。     

Manual pressure distension of the human saphenous vein changes its biomechanical properties-implication for coronary artery bypass grafting

Patency rates of saphenous vein grafts following coronary artery bypass grafting (CABG) depend on multiple factors. Information regarding the impact of biomechanical properties of vein grafts on patency rates is not available. The objective of the present study was to evaluate whether uncontrolled manual pressure distension during routine preparation of the saphenous vein in CABG-induced changes in the biomechanical properties of the vein. The morphometric and stress-strain properties were studied in isolated segments of the saphenous vein from 12 patients undergoing elective CABG. Six segments were manually distended without pressure control and six were not distended. The mechanical test was performed as a ramp inflation using syringe pump. The vein dimensions were obtained from digitised images at different pressures as well as at the no-load and zero-stress states. The circumferences, the wall and lumen area, the wall thickness, and the outer diameter as function of the applied pressure were largest in the segments with uncontrolled manual distension compared to those without distension (P<0.05). The opening angle and the absolute value of the residual strains were lower (P<0.01) and the circumferential stress-strain curve shifted to the left, indicating the wall became stiffer with uncontrolled manual distension compared to those without distension (P<0.05). In conclusion, manual pressure distension changed the morphometric and biomechanical properties of the saphenous vein. The perspective is that studies on biomechanical properties on the saphenous vein may guide surgeons how to handle graft material without causing major changes of the biomechanical properties during harvesting and preparation.     

Prediction of distal radius fracture in children, using a biomechanical impact model and case-control data on playground free falls

OBJECTIVES: To assess the ability of a biomechanical impact model to predict the likelihood of distal radius fracture in children using data gathered for a previous epidemiological case-control study of falls from playground equipment. METHODOLOGY: Factor of Risk (FR) values were generated for each of selected subjects from the case-control study using a biomechanical model. Logistic regression curves were fitted to examine the relationship between the FR values and the probability of radius fracture. RESULTS: Forty-five cases and thirty-one controls were selected. The logistic regression analyses showed a significant association between the probability of fracture and FR. CONCLUSIONS: The biomechanical model distinguished between children who fractured their distal radius and those who did not. The model can be used to test how risk factors, such as fall height and ground surface type, affect physical stresses transmitted through the arm and their relation to the fracture tolerance of the distal radius.     

Biomechanics of cross-sectional size and shape in the hominoid mandibular corpus

Mandibular cross sections of Pan, Pongo, Gorilla, Homo, and two fossil specimens of Paranthropus were examined by computed tomography (CT) to determine the biomechanical properties of the hominoid mandibular corpus. Images obtained by CT reveal that while the fossil hominids do not differ significantly from extant hominoids in the relative contribution of compact bone to total subperiosteal area, the shape of the Paranthropus corpora indicates that the mechanical design of the robust australopithecine mandible is fundamentally distinct from that of modern hominoids in terms of its ability to resist transverse bending and torsion. It is also apparent that, among the modern hominoids, interspecific and sexual differences in corpus shape are not significant from a biomechanical perspective. While ellipse models have been used previously to describe the size, shape, and subsequent biomechanical properties of the corpus, the present study shows that such models do not predict the biomechanical properties of corpus cross-sectional geometry in an accurate or reliable manner. The traditional "robusticity" index of the mandibular corpus is of limited utility for biomechanical interpretations. The relationship of compact bone distribution in the corpus to dimensions such as mandibular length and arch width may provide a more functionally meaningful definition of mandibular robusticity.     

Effect of freeze-drying and gamma irradiation on biomechanical properties of bovine pericardium

Freeze-drying and gamma irradiation are the techniques widely use in tissue banking for preservation and sterilization of tissue grafts respectively. However, the effect of these techniques on biomechanical properties of bovine pericardium is poorly known. A total of 300 strips of bovine pericardium each measured 4 cm × 1 cm were used in this study to evaluate the effect of freeze-drying on biomechanical properties of fresh bovine pericardium and the effect of gamma irradiation on biomechanical properties of freeze-dried bovine pericardium. The strips were divided into three equal groups, which consist of 100 strips each group. The three groups were fresh bovine pericardium, freeze-dried bovine pericardium and irradiated freeze-dried bovine pericardium. The biomechanical properties of the pericardial strips were measured by a computer controlled instron tensiometer while the strips thickness was measured by Mitutoyo thickness gauge. The results of the study revealed that freeze-drying has no significant (p > 0.05) effect on the tensile strength, Youngs modulus (stiffness) and elongation rate of fresh bovine pericardium. Irradiation with 25 kGy gamma rays caused significant decreased in the tensile strength, Youngs modulus and elongation rate of the freeze-dried pericardium. However, gamma irradiation has no significant effect on the thickness of freeze-dried bovine pericardium, while freeze-drying caused significant decreased in the thickness of the fresh bovine pericardium. The outcome of this study demonstrated that freeze-drying has no significant effect on the biomechanical properties of fresh bovine pericardium, and gamma irradiation caused significant effect on the biomechanical properties of freeze-dried bovine pericardium.     

Beneficial effect of zinc supplementation on biomechanical properties of femoral distal end and femoral diaphysis of male rats chronically exposed to cadmium

The present study was aimed at estimate, based on the rat model of human moderate and relatively high chronic exposure to cadmium (Cd), whether zinc (Zn) supplementation may prevent Cd-induced weakening in the bone biomechanical properties. For this purpose, male Wistar rats were administered Cd (5 or 50 mg/l) or/and Zn (30 or 60 mg/l) in drinking water for 6 and 12 months. Bone mineral density (BMD) and biomechanical properties (yield load, ultimate load, post-yield load, displacement at yield and at ultimate, stiffness, work to fracture, yield stress, ultimate stress and Young modulus of elasticity) of the femoral distal end and femoral diaphysis were examined. Biomechanical properties of the distal femur were estimated in a compression test, whereas those of the femoral diaphysis -- in a three-point bending test. Exposure to Cd, in a dose and duration dependent manner, decreased the BMD and weakened the biomechanical properties of the femur at its distal end and diaphysis. Zn supplementation during Cd exposure partly, but importantly, prevented the weakening in the bone biomechanical properties. The favorable Zn influence seemed to result from an independent action of this bioelement and its interaction with Cd. However, Zn supply at the exposure to Cd had no statistically significant influence on the BMD at the distal end and diaphysis of the femur. The results of the present paper suggest that Zn supplementation during exposure to Cd may have a protective influence on the bone tissue biomechanical properties, and in this way it can, at least partly, decrease the risk of bone fractures. The findings seem to indicate that enhanced dietary Zn intake may be beneficial for the skeleton in subjects chronically exposed to Cd.     

The relationships between physical capacity and biomechanical plasticity in old adults during level and incline walking

Old compared to young adults exhibit increased hip and decreased ankle mechanical output during walking – a phenomenon known as biomechanical plasticity. Previous comparison studies suggest that low compared to high capacity old adults exhibit larger magnitudes of this plasticity, however the precise relationship between capacity and plasticity magnitude remains unclear. The purpose of this study was to quantify the relationships between physical capacity and biomechanical plasticity magnitude during level and incline walking. Data were collected for 32 old adults walking over level and inclined (+10°) surfaces at self-selected, comfortable speeds. Physical capacity was measured using the Short-Form Health Survey Physical Component (SF-36 PC) and biomechanical plasticity was quantified by ratios of hip extensor to ankle plantarfexor peak torques, angular impulses, peak positive powers, and positive work (larger ratios indicate larger magnitudes of plasticity). SF-36 PC scores correlated positively with all four biomechanical plasticity ratios during level walking and three of the four ratios during incline walking. Some of the biomechanical plasticity ratios correlated positively with comfortable walking speeds and stride frequencies, indicating better walking performance with larger magnitudes of plasticity. Additionally, all four biomechanical plasticity ratios were larger during incline compared to level walking, suggesting the need for larger magnitudes of plasticity during the more difficult task. These results indicate that larger magnitudes of biomechanical plasticity afford functional benefits such as increased level and incline walking performance for old adults. Increased walking performance has the potential to increase quality of life in the growing population of old adults.     

Biaxial biomechanical properties of the nonpregnant murine cervix and uterus

From a biomechanical perspective, female reproductive health is an understudied area of research. There is an incomplete understanding of the complex function and interaction between the cervix and uterus. This, in part, is due to the limited research into multiaxial biomechanical functions and geometry of these organs. Knowledge of the biomechanical function and interaction between these organs may elucidate etiologies of conditions such as preterm birth. Therefore, the objective of this study was to quantify the multiaxial biomechanical properties of the murine cervix and uterus using a biaxial testing set-up. To accomplish this, an inflation-extension testing protocol (n = 15) was leveraged to quantify biaxial biomechanical properties while preserving native matrix interactions and geometry. Ultrasound imaging and histology (n = 10) were performed to evaluate regional geometry and microstructure, respectively. Histological analysis identified a statistically significant greater collagen content and significantly smaller smooth muscle content in the cervix as compared to the uterus. No statistically significant differences in elastic fibers were identified. Analysis of bilinear fits revealed a significantly stiffer response from the circumferentially orientated ECM fibers compared to axially orientated fibers in both organs. Bilinear fits and a two-fiber family constitutive model showed that the cervix was significantly less distensible than the uterus. We submit that the regional biaxial information reported in this study aids in establishing an appropriate reference configuration for mathematical models of the uterine-cervical complex. Thus, may aid future work to elucidate the biomechanical mechanisms leading to cervical or uterine conditions.     

Masses, centers-of-gravity, and moments-of-inertia of the body segments of the rhesus monkey (Macaca mulatta).

Segmental parameters (mass, center-of-gravity, and moment-of-inertia) are necessary for biomechanical analyses of a species' locomotor behavior. Seven male and eight female adult rhesus monkey cadavers were dismembered in order to determine segmental parameters. Mean values for the segment masses and moments-of-inertia are presented for males and females, separately and together. Statistical tests revealed significant differences between the sexes for these parameters. Regression equations for predicting segment masses and moments-on-inertia were developed for the sexes separately and pooled. For most segments the male and female equations did not differ significantly in slope or y-intercept. The center-of-gravity for each segment is presented as a mean percentage of the distance between the proximal and distal joint centers. The regression equations and center-of-gravity locations presented here permit biomechanical investigations of rhesus monkey locomotion without the necessity of subsequent sacrifice. The segmental parameter values determined for the rhesus monkey are compared with available data for other primate and mammalian species and the biomechanical and adaptive implications of such comparisons are discussed.     

Ineffectiveness of acute scalp expansion.

The aim of this study was to test the ex vivo biomechanical properties of acutely expanded scalp flaps to quantitatively assess the efficacy of acute scalp expansion. A total of 14 fresh male cadavers were used for the study. In each cadaver, a rectangular (4 x 10 cm), laterally based flap was designed on each side of the scalp, starting from the superior margin of the external auditory canal. One randomly selected flap per scalp underwent acute intermittent expansion (a 3-minute expansion/3-minute rest cycle was performed three times with the maximum expansion achievable); the contralateral flap served as a control. After the expansion process, the acutely expanded flaps were measured to assess whether applied biomechanical stress caused any changes in flap dimensions. The biomechanical properties (stress/strain ratio, mean stiffness) of both expanded and control flaps were then assessed by means of a dynamometer and a force transducer. The obtained data showed that the biomechanical benefits provided by acute scalp expansion were not statistically different (p < 0.05) from those obtained by simple subgaleal undermining. No change of length nor gain in compliance was observed in the acutely expanded flaps as compared with control scalp flaps. In the authors' opinion, a possible explanation (to be further validated) for the lack of effect of acute scalp expansion might be that the inelastic galea aponeurotica did not allow mechanical creep to exploit the inherent elastic properties of the overlying scalp skin.     

Effects of the production of perceived exertion during cycle ergometry

Physiological and biomechanical effects of aerobic exercise varying in intensity were studied on the basis of the subjects’ perceived exertion. It was demonstrated that exercise regulated with the use of a 50–100 rating scale was characterized by reliably stable heart-rate and respiratory reactions and biomechanical responses. The relative working heart rate (HR) expressed in percent of the individual HRmax was found to be closely correlated with the values on the 50–100 scale within a wide range during exercise with constant or increasing perceived exertion.     

Biomechanical Response of the Root System in Tomato Seedlings under Wind Disturbance

Wind disturbance as a green method can effectively prevent the overgrowth of tomato seedlings, and its mechanism may be related to root system mechanics. This study characterized the biophysical mechanical properties of taproot and lateral roots of tomato seedlings at five seedling ages and seedling substrates with three different moisture content. The corresponding root system-substrate finite element (FE) model was then developed and validated. The study showed that seedling age significantly affected the biomechanical properties of the taproot and lateral roots of the seedlings and that moisture content significantly affected the biomechanical properties of the seedling substrate (p < 0.05). The established FE model was sensitive to wind speed, substrate moisture content, strong seedling index, and seedling age and was robust. The multiple linear regression equations obtained could predict the maximum stress and strain of the root system of tomato seedlings in the wind field. The strong seedling index had the greatest impact on the biomechanical response of the seedling root system during wind disturbance, followed by wind speed. In contrast, seedling age had no significant effect on the biomechanical response of the root system during wind disturbance. In the simulation, no mechanical damage was observed on the tissue of the seedling root system, but there were some strain behaviors. Based on the plant stress resistance, wind disturbance may affect the growth and development of the root system in the later growth stage. In this study, finite element and statistical analysis methods were combined to provide an effective approach for in-depth analysis of the biomechanical mechanisms of wind disturbances that inhibit tomato seedlings’ growth from the root system’s perspective.     

A Comprehensive Specimen-Specific Multiscale Data Set for Anatomical and Mechanical Characterization of the Tibiofemoral Joint

Understanding of tibiofemoral joint mechanics at multiple spatial scales is essential for developing effective preventive measures and treatments for both pathology and injury management. Currently, there is a distinct lack of specimen-specific biomechanical data at multiple spatial scales, e.g., joint, tissue, and cell scales. Comprehensive multiscale data may improve the understanding of the relationship between biomechanical and anatomical markers across various scales. Furthermore, specimen-specific multiscale data for the tibiofemoral joint may assist development and validation of specimen-specific computational models that may be useful for more thorough analyses of the biomechanical behavior of the joint. This study describes an aggregation of procedures for acquisition of multiscale anatomical and biomechanical data for the tibiofemoral joint. Magnetic resonance imaging was used to acquire anatomical morphology at the joint scale. A robotic testing system was used to quantify joint level biomechanical response under various loading scenarios. Tissue level material properties were obtained from the same specimen for the femoral and tibial articular cartilage, medial and lateral menisci, anterior and posterior cruciate ligaments, and medial and lateral collateral ligaments. Histology data were also obtained for all tissue types to measure specimen-specific cell scale information, e.g., cellular distribution. This study is the first of its kind to establish a comprehensive multiscale data set for a musculoskeletal joint and the presented data collection approach can be used as a general template to guide acquisition of specimen-specific comprehensive multiscale data for musculoskeletal joints.