Biomechanical Changes Research Articles

Effects of Different Load Carriage on Spatiotemporal Gait Parameters in Elite Intervention Police Officers

Carrying heavy loads may present certain biomechanical changes in special populations. However, most of the existing research on whether or not different external loads impact gait biomechanics has been conducted in military personnel, while the same changes have been relatively unknown in other populations, such as police officers. In order to maximize the importance of load ergonomics and design, it is necessary to establish both spatial and temporal gait changes under different load conditions in a variety of high-risk jobs, in order to detect which parameters are the most important for special interventions and policies. Therefore, the purpose of this study was to examine changes in spatial and temporal gait parameters under different loading conditions. Ninety-six intervention police officers were recruited and evaluated. Zebris FDM pedobarographic platform was used to assess spatial and temporal gait changes gradual increases in load carriage significantly increased cadence (p = 0.024, η2 = 0.029), stance-phase for left (p = 0.046, η2 = 0.024) and right foot (p = 0.019, η2 = 0.030), and load response for left (p = 0.044, η2 = 0.025) and right foot (p = 0.033, η2 = 0.027), while decreases in step time for left foot (p = 0.024, η2 = 0.029), and swing phase for left (p = 0.047, η2 = 0.024) and right foot (p = 0.047, η2 = 0.024) were observed. No significant changes in spatial gait parameters occurred when carrying heavier loads. In conclusion, increases in external loads lead to larger changes in temporal, but not in spatial foot characteristics during gait. Thus, temporal gait parameters may be more prone to changes when carrying heavy loads.

Comparative Effects of Active Release Technique and Positional Release Therapy in Female Students with Tightened Calf Muscles

Background: Prior research has established that regular use of high-heeled shoes significantly alters the gait pattern, impacts ankle joint motion, increases joint forces and moments in the lower extremities, modifies foot pressure distribution, and affects posture and balance. These biomechanical changes can lead to tightened calf muscles and associated discomfort in frequent high heel wearers. Objective: The main objective of this study is to compare the effect of Active Release Technique and Positional Release Therapy in female students with tightened calf muscles. Methods: A randomized clinical trial including 26 subjects by using convenient sampling technique, with subject age ranging from 20-30 years wearing high heels with minimum duration (5 hours a day, 5 times a week and for more than 1 year) with heel height minimum of 2''. The outcome measures were ankle dorsiflexion plantar flexion range of motion measured by goniometer, and pain measured by Numerical Pain Rating Scale. Data was collected for 4 months (Feb-May 2023) from The University of Faisalabad and Government College University Faisalabad. Over four weeks & 3 times per week both groups received ultrasound and traditional Physiotherapy of conventional calf muscle stretching as baseline treatment. Group 1 received Positional Release Therapy, while Group 2 received Active Release Technique. Results: Friedman test showed within-group improvements in NPRS, Dorsiflexion, Plantar flexion, and Cadence (p<0.05) for both groups. Mann Whitney U test revealed significant improvements in NPRS, Dorsiflexion, Plantar flexion, and Cadence at post-treatment (p<0.05) for Positional Release Therapy group more than Active Release Therapy.. Conclusion: Positional Release Therapy (PRT) has more significant effects for calf muscle tightness, exhibiting increased cadence, ankle dorsiflexion, and plantar flexion range of motion, along with significant pain reduction than Active Release Therapy (ART)

Dynamic biomechanical changes of clear aligners during extraction space closure: Finite element analysis

Clear aligners (CAs) have recently become popular and widely used orthodontic appliances. Research on CA biomechanics has become a focal point in orthodontics to improve the efficiency of CA treatment and address challenging issues, such as extraction. The biomechanical characteristics of CAs in space closure have been reported. However, previous studies have mainly focused on static biomechanical analysis that cannot demonstrate the dynamic biomechanical changes in CAs during space-closing. Given that these biomechanical changes can be significant and have considerable clinical value, this study aimed to investigate these characteristics. Sequential extraction space-closing models were derived from included patient data and refined using modeling and CA design software. A finite element analysis was performed to obtain biomechanical raw data. This study introduced a dual coordinate system and space geometry analysis to demonstrate the biomechanical properties accurately. As space closure progressed, the instantaneous tooth displacements increased, indicating an enhanced space closure force because of the increased strain in the CA extraction area. Meanwhile, the central axis of rotation of the anterior teeth continuously moved toward the labial-apical direction, showing a gradually enhanced vertical and torque control effect. During space closure, CAs undergo specific biomechanical changes, including increased contraction and control forces on both sides of the gap. These biomechanical effects are beneficial to alleviate the roller coaster effect gradually. Meanwhile, more reasonable staging design strategies can be proposed on the basis of this biomechanical mechanism.

Association of low back pain with the use of high heel in ladies: a systematic review

Background & Objective: High heels of shoes are preferred for attractiveness, but are detrimental to health regarding their biomechanics. High heel changes the joint mechanics during walking which may result in abnormal stress and pressure at certain points and thus lead to painful knee, foot, hip or low back pain. The objective of this systematic review was to evaluate the literature addressing the association between the high heeled shoes and low back pain among females. Methodology: It was a systemic review conducted during 2014-2020 on databases including Cochrane Library, PubMed, Medline, PEDro and Scopus, with key words ‘Low back pain’ OR ‘Back pain OR Lumbago’, ‘Low back pain in females OR Back pain in females OR Lumbago in females’, ‘High heeled shoes OR High heels’, ‘Association OR relationship’. Available full-length papers in English language were explored, after the screening and quality assessment using Axis critical appraisal tool for the studies. Results: We found 32 articles, but the inclusion criteria were met only by 11 studies in quality score of 16. 27/20. The eligible studies enrolled a total of 1334 female participants with an average age of 18-32 y. Nine studies explained that low back pain was associated with high heeled shoes but none specified height of the heel, and only a range of 2.5-11 cm was suspected to be associated with changes in lumber biomechanics or lordosis, that can exert extra pressure for postural adjustments and lead to low back pain. Conclusion: Out of 11 studies, nine studies favored that low back pain was associated with high heeled shoes, there was no specific height mentioned; but only a range of 2.5-11 cm was found to be associated with biomechanical changes due to postural adjustments, being a possible cause of low back pain among females. Key words: Association; Females; High Heel; Low Back Pain; Shoes Citation: Younas AS, Tanveer F, Sharif F, Waseem I, Mahmood W, Ahmad A. Association of low back pain with the use of high heel in ladies: a systematic review. Anaesth. pain intensive care 2023;27(6):681−688. DOI: 10.35975/apic.v27i6.2339 Received: June 20, 2022; Revised: July 07, 2023; Accepted: November 08, 2023

Biomechanical changes in adolescent idiopathic scoliosis during walking: A protocol for systematic review and meta-analysis.

To clarify the differences in biomechanical characteristics present in adolescent idiopathic scoliosis (AIS) patients during walking. Cross-sectional studies related to the biomechanical characteristics of AIS were included by searching 7 major databases and analyzed using RevMan 5.4 software. There were a total of 15 trials involving 377 AIS patients. The results showed that during walking, AIS had increased pelvic coronal tilt (effect size [ES] = -1.34, 95% confidence intervals [CI] = -2.41 to -0.27, P = .01), knee and ankle sagittal mobility were reduced (ES = -5.22, 95% CI = -7.51 to -2.94, P < .001; ES = -3.58, 95% CI = -5.93 to -1.22, P = .003). The duration of electromyogram activity was prolonged in the gluteus medius (ES = 7.65, 95% CI = 5.33-9.96, P < .001), lumbar square (ES = 10.73, 95% CI = 6.97-14.49, P < .001), and erector spinae (ES = 14.35, 95% CI = 6.94-21.76, P < .001) muscles. The results of subgroup analysis showed that the step length of the concave side of the spine was reduced (ES = -0.36, 95% CI = -0.71 to -0.01, P = .04). AIS has characteristic biomechanical changes in spatiotemporal, phase kinematics, motor mechanics, and electromyographic signatures. Further comprehensive studies are required in the future to analyze the biomechanical and electromyographic differences among different degrees and types of scoliosis, as well as the differences between the concave and convex sides of scoliosis during walking.

A Corneal Biomechanical Study Measured with a Scheimpflug Dynamic Analyser in Soft Contact Lens Wearers.

The aim of this study was to evaluate the biomechanical changes in the cornea after wearing soft contact lenses (CLs) in healthy myopic patients measured with a Corvis ST® (CST, Oculus Optikgeräte GmbH, Wetzlar, Germany) analyser. This prospective, cross-sectional, single-centre study was performed on twenty-two Caucasian patients aged between 19 and 24 years (20.64 ± 1.21 years) range. Five device-specific biomechanical parameters, the central corneal thickness (CCT), and biomechanically corrected intraocular pressure (bIOP) were measured prior to fitting and one month after CL wear. Differences between the means of the deflection amplitude ratio (DA Ratio) and the standard deviation of the DA Ratio (SD DA Ratio) pre- and post-CL wear were found to be significant (p value = 0.002 in both cases). Significant differences were found between pre- and post-CL wear values in CCT (p value = 0.013). For all other biomechanical measures, no significant differences were observed before and after treatment. A significant association was found between changes in bIOP and classification according to changes in Int. Radius (p value = 0.047) and SSI (p value = 0.026) standard deviations. The corneal biomechanical indices provided by CST demonstrate that the fitting of soft CLs is a safe optical compensation method for the stability of corneal stiffness. No significant differences were found pre- and post-CL wear in the assessment of bIOP.

Neck pain, disability and mobile phone usage among physiotherapy students - a cross-sectional study.

Modern mobile devices have become tools used for educational, research, business or recreational purposes. Incorrect position during excessive use of a smartphone can lead to biomechanical changes, the most visible of which is the position of the head in protraction, characterized by the protrusion of the head and neck forward in relation to the shoulder girdle and trunk. The aim of the study was to analyze the relationship between disability, neck pain (NP), use of phones before bedtime, and hours of using smartphones. The study involved 146 physiotherapy students aged 18-26. Students were asked to complete pain surveys (VAS pain scale), and Neck Disability Index (NDI). Participants were also asked if their pain lasted longer than 3 months, how long they used their smartphone during the day, and whether they used it before bedtime. Statistically significant differences were found between groups with and without neck pain regarding NDI score (p<0.001). Participants who suffered from neck pain longer than 3 months had greater NDI scores (p=0.03), greater intensity of symptoms (p=0.04), greater problems with reading (p<0.01) and driving (p=0.04) than participants who experienced pain for less than 3 months. Using phones before bedtime was related to problems with focusing (p<0.01). There were statistically significant correlations between the time of phone use and disability in terms of reading (p=0.04), focusing (p<0.001), work (p<0.001) and sleeping (p=0.02). Dysfunctions associated with pain in the cervical section may affect the learning abilities of students and thus the acquisition of professional competencies. Not using a smartphone before bedtime is recommended, as it causes poorer concentration. The longer the time spent using the phone, the more significant the disability.

Cationic tantalum oxide nanoparticle contrast agent for micro computed tomography reveals articular cartilage proteoglycan distribution and collagen architecture alterations

ObjectiveCationic tantalum oxide nanoparticles (Ta2O5-cNPs), as a newly introduced contrast agent for computed tomography (CT) of cartilage, offer quantitative evaluation of proteoglycan content and biomechanical properties. However, knowledge on the depth-wise impact of cartilage constituents on NP diffusion, particularly the influence of the collagen network, is lacking. In this study, we aim to establish the depth-dependent relationship between Ta2O5-cNP diffusion and cartilage constituents (proteoglycan content, collagen content and network architecture). MethodsOsteochondral samples (n = 30) were harvested from healthy equine stifle joints (N = 15) and the diffusion of 2.55 nm diameter cationic Ta2O5-cNPs into the cartilage was followed with µCT imaging for up to 96 hours. The diffusion-related parameters, Ta2O5-cNP maximum partition (Pmax) and diffusion time constant, were compared against biomechanical and depth-wise structural properties. Biomechanics were assessed using a stress-relaxation and sinusoidal loading protocols, whereas proteoglycan content, collagen content and collagen network architecture were determined using digital densitometry, Fourier-transform infrared spectroscopy and polarized light microscopy, respectively. ResultsThe Pmax correlates with the depth-wise distribution of proteoglycans (bulk Spearman’s ρ = 0.87, p < 0.001). More open collagen network architecture at the superficial zone enhances intake of Ta2O5-cNPs, but collagen content overall decreases the intake. The Pmax values correlate with the equilibrium modulus (ρ = 0.80, p < 0.001) of articular cartilage. ConclusionThis study establishes the feasibility of Ta2O5-cNPs for the precise and comprehensive identification of biomechanical and structural changes in articular cartilage via contrast-enhanced µCT.

The Effects of Differential Learning on the Standing Broad Jump.

In this investigation, we examined the influence of two approaches of motor skill learning (differential learning and repetition-based) for an explosive motor skill. Twenty-seven individuals completed four training sessions of a standing broad jump task, presented with either differential training or a repetition-based approach. We collected pre-and post-training assessments that included maximal jump distances used to index performance and the recording of ground reaction forces to determine potential biomechanical changes (normalized vertical ground reaction force - GRFvert, rate of force development - RFD, and horizontal take-off velocity - Vhor). Results showed that differential training exhibited greater jump distances than repetition-based training (p < .001) but no training effect was found for jump distances between pre- and post-assessments for either training approach (p = .15). However, a significant increase occurred for Vhor with greater velocities achieved following training (p = .03). Overall, differential training failed to show the expected performance enhancements for a discrete, explosive motor task; this may be related to limited exposure and task specific demands of the movement. Further research is needed to better understand the task factors influencing skill acquisition from differential training.

Effects of age and noise on tympanal displacement in the Desert Locust

Insect cuticle is an evolutionary-malleable exoskeleton that has specialised for various functions. Insects that detect the pressure component of sound bear specialised sound-capturing tympani evolved from cuticular thinning. Whilst the outer layer of insect cuticle is composed of non-living chitin, its mechanical properties change during development and aging. Here, we measured the displacements of the tympanum of the desert Locust, Schistocerca gregaria, to understand biomechanical changes as a function of age and noise-exposure. We found that the stiffness of the tympanum decreases within 12 h of noise-exposure and increases as a function of age, independent of noise-exposure. Noise-induced changes were dynamic with an increased tympanum displacement to sound within 12 h post noise-exposure. Within 24 h, however, the tone-evoked displacement of the tympanum decreased below that of control Locusts. After 48 h, the tone-evoked displacement of the tympanum was not significantly different to Locusts not exposed to noise. Tympanal displacements reduced predictably with age and repeatably noise-exposed Locusts (every three days) did not differ from their non-noise-exposed counterparts. Changes in the biomechanics of the tympanum may explain an age-dependent decrease in auditory detection in tympanal insects.

MTORC1 Mediates Biphasic Mechano-Response to Orchestrate Adhesion-Dependent Cell Growth and Anoikis Resistance.

Cells constantly sense and respond to not only biochemical but also biomechanical changes in their microenvironment, demanding for dynamic metabolic adaptation. ECM stiffening is a hallmark of cancer aggressiveness, while survival under substrate detachment also associates with poor prognosis. Mechanisms underlying this, non-linear mechano-response of tumor cells may reveal potential double-hit targets for cancers. Here, an integrin-GSK3β-FTO-mTOR axis is reported, that can integrate stiffness sensing to ensure both the growth advantage endowed by rigid substrate and cell death resistance under matrix detachment. It is demonstrated that substrate stiffening can activate mTORC1 and elevate mTOR level through integrins and GSK3β-FTO mediated mRNA m6 A modification, promoting anabolic metabolism. Inhibition of this axis upon ECM detachment enhances autophagy, which in turn conveys resilience of tumor cells to anoikis, as it is demonstrated in human breast ductal carcinoma in situ (DCIS) and mice malignant ascites. Collectively, these results highlight the biphasic mechano-regulation of cellular metabolism, with implications in tumor growth under stiffened conditions such as fibrosis, as well as in anoikis-resistance during cancer metastasis.

Modeling and evaluation of biomechanics and hemodynamic based on patient-specific small intracranial aneurysm using fluid-structure interaction

Background and ObjectiveRupture of small intracranial aneurysm (IA) often leads to the development of highly fatal clinical syndromes such as subarachnoid hemorrhage. Due to the patient specificity of small IA, there are many difficulties in evaluating the rupture risk of small IA such as multiple influencing factors, high clinical experience requirements and poor reusability. MethodsIn this study, clinical methods such as transcranial doppler (TCD) and magnetic resonance imaging (MRI) are used to obtain patient-specific parameters, and the fluid-structure interaction method (FSI) is used to model and evaluate the biomechanics and hemodynamics of patient-specific small IA. ResultsThe results show that a spiral vortex stably exists in the patient-specific small IA. Due to the small size of the patient-specific small IA, the blood flow velocity still maintains a high value with maximum reaching 3 m/s. The inertial impact of blood flow and vortex convection have certain influence on hemodynamic and biomechanics parameters. They cause three high value areas of WSSM on the patient-specific small IA with maximum of 180 Pa, 130 Pa and 110 Pa, respectively. They also cause two types of WSS concentration points, positive normal stress peak value areas and negative normal stress peak value areas to appear. ConclusionThis paper found that the factors affecting hemodynamic parameters and biomechanical parameters are different. Unlike hemodynamic parameters, biomechanical parameters are also affected by blood pressure in addition to blood flow velocity. This study reveals the relationship between the flow field distribution and changes of patient-specific small IA, biomechanics and hemodynamics.

Esophageal biomechanics assessed by impedance planimetry (EndoFLIPTM) in healthy subjects and in patients with eosinophilic esophagitis. Normality values.

active eosinophilic esophagitis is associated with esophageal caliber, distensibility and motility changes that may be reversed with treatment. to study esophageal diameter, distensibility and contractility in healthy subjects compared to patients with eosinophilic esophagitis, both before and after treatment. a quasi-experimental study, EndoFLIP™, was used to analyze the esophageal body and esophago-gastric junction (EGJ) in all three groups, and a program was designed to obtain esophageal diameter, distensibility and contractility values. ten healthy volunteers (24-61 years, six men) and nine patients with eosinophilic esophagitis (21-52 years, seven men) were included. The esophagogastric junction distensibility index was 5.07 mm2/Hg in the control subjects, 2.40 mm2/Hg in the subjects with eosinophilic esophagitis before treatment and 2.46 mm2/Hg after treatment. The distensibility plateau was 20.02 mm, 15.43 mm and 17.41 mm, respectively, and the diameter was 21.90 mm, 17.73 mm and 18.30 mm, showing significant differences (p < 0.05), except between control subjects and patients after treatment (p = 0.079). Repetitive antegrade contractions developed in 90 % of control subjects, 66.7 % of eosinophilic esophagitis patients before treatment and 88.9 % of the latter after treatment (p > 0.05). esophago-gastric junction distensibility index, distensibility plateau and diameter values were higher in controls than in patients, although six weeks of treatment seems a short period to observe significant changes in esophageal biomechanics. Repetitive antegrade contractions are the predominant pattern in healthy subjects and eosinophilic esophagitis. We provide normality values for esophageal biomechanics, measured by impedance planimetry in our setting.

Sex differences in the biomechanical and biochemical responses of caudal rat intervertebral discs to injury.

Intervertebral disc degeneration (IDD) is a major cause of low back pain (LBP) worldwide. Sexual dimorphism, or sex-based differences, appear to exist in the severity of LBP. However, it is unknown if there are sex-based differences in the inflammatory, biomechanical, biochemical, and histological responses of intervertebral discs (IVDs). Caudal (Coccygeal/Co) bone-disc-bone motion segments were isolated from multiple spinal levels (Co8 to Co14) of male and female Sprague-Dawley rats. Changes in motion segment biomechanics and extracellular matrix (ECM) biochemistry (glycosaminoglycan [GAG], collagen [COL], water, and DNA content) were evaluated at baseline and in response to chemical insult (lipopolysaccharide [LPS]) or puncture injury ex vivo. We also investigated the contributions of Toll-like receptor (TLR4) signaling on responses to LPS or puncture injury ex vivo, using a small molecule TLR4 inhibitor, TAK-242. Findings indicate that IVD motion segments from female donors had greater nitric oxide (NO) release in LPS groups compared to male donors. HMGB1 release was increased in punctured discs, but not LPS injured discs, with no sex effect. Although both male and female discs exhibited reductions in dynamic moduli in response to LPS and puncture injuries, dynamic moduli from female donors were higher than male donors across all groups. In uninjured (baseline) samples, a significant sex effect was observed in nucleus pulposus (NP) DNA and water content. Female annulus fibrosus (AF) also had higher DNA, GAG, and COL content (normalized bydry weight), but lower water content than male AF. Additional injury- and sex-dependent effects were observed in AF GAG/DNA and COL/DNA content. Finally, TAK-242 improved the dynamic modulus of female but not male punctured discs. Our findings demonstrate that there are differences in rat IVD motion segments based on sex, and that the response to injury in inflammatory, biomechanical, biochemical, and histological outcomes also exhibit sex differences. TLR4 inhibition protected against loss of mechanical integrity of puncture-injured IVD motion segments, with differences responses based on donor sex.

Running-Specific Prosthesis

Sports help children “develop physical skills that contribute to a lifetime of physical involvement; … learn social and emotional skills; develop moral values; and acquire a better sense of self through increased perceived competence, self-esteem, and self-confidence” (Ewing, Gano-Overway, Branta, &amp; Seefeldt, 2002). Lower-leg amputations jeopardize children’s ability to continue participating in sports, as it removes a part of the body that is essential for running and sports participation. Running-specific prostheses (RSPs), a type of lower-limb prosthesis, provide a solution to this issue. Compared to daily-use prosthetics, running-specific prosthetics have a higher energy-storage capacity, are more flexible, and are more springy, allowing them to mimic the nature of running biological legs better than daily-use prosthetics. RSPs also have customizations that are specific to the physical traits and activity of an amputee, allowing an amputee to play a plethora of sports. Although children must overcome challenges regarding the change in biomechanics while running with an RSP and accounting for the rapid growth of children, RSPs can provide amputees the opportunity to return to the sports environment.

Distal aortic biomechanics after transcatheter versus surgical aortic valve replacement: a hypothesis generating study

BackgroundBiomechanical effects of transcatheter (TAVR) versus surgical (SAVR) aortic valve interventions on the distal aorta have not been studied. This study utilized global circumferential strain (GCS) to assess post-procedural biomechanics changes in the descending aorta after TAVR versus SAVR.MethodsPatients undergoing TAVR or SAVR for aortic stenosis were included. Transesophageal (TEE) and transthoracic (TTE) echocardiography short-axis images of the aorta were used to image the descending aorta immediately before and after interventions. Image analysis was performed with two-dimensional speckle tracking echocardiography and dedicated software. Delta GCS was calculated as: post-procedural GCS—pre-procedural GCS. Percentage delta GCS was calculated as: (delta GCS/pre-procedural GCS) × 100.ResultsEighty patients, 40 TAVR (median age 81 y/o, 40% female) and 40 SAVR (median 72 y/o, 30% female) were included. The post-procedure GCS was significantly higher than the pre-procedural GCS in the TAVR (median 10.7 [interquartile range IQR 4.5, 14.6] vs. 17.0 [IQR 6.1, 20.9], p = 0.009) but not in the SAVR group (4.4 [IQR 3.3, 5.3] vs. 4.7 [IQR 3.9, 5.6], p = 0.3). The delta GCS and the percentage delta GCS were both significantly higher in the TAVR versus SAVR group (2.8% [IQR 1.4, 6] vs. 0.15% [IQR − 0.6, 1.5], p < 0.001; and 28.8% [IQR 14.6%, 64.6%] vs. 4.4% [IQR − 10.6%, 5.6%], p = 0.006). Results were consistent after multivariable adjustment for key clinical and hemodynamic characteristics.ConclusionsAfter TAVR, there was a significantly larger increase in GCS in the distal aorta compared to SAVR. This may impact descending aortic remodeling and long-term risk of aortic events.

Reducing the number of hip dislocations after total hip arthroplasty based on the study of the mechanisms of their development

Total hip arthroplasty is one of the most effective surgical interventions that improves quality of life, increases a range of motion, and reduces pain in patients with degenerative hip joint disease. Total hip arthroplasty allows patients to return to daily social and professional activities. Thus, it is currently the best approach to the treatment of several chronic conditions affecting the hip joint, including osteoarthritis, avascular necrosis of the femoral head, and traumatic injuries to the femoral head and neck. The purpose of this study was to show the mechanisms of hip dislocation in the presence of a hip endoprosthesis, associated risk factors and factors that reduce the risk of dislocation, as well as its consequences and methods for minimization. Hip dislocation is a common complication following total hip arthroplasty. It is the cause of 2 to 3 % of failures of primary replacements, increasing even to 10 % in extreme cases in patients highly predisposed to this condition. In general, technical errors during implant placement are the cause of dislocation. The measures taken to prevent complications include activities aimed to the correct implant insertion and selection of the most appropriate type of implant for the patient, depending on individual needs. This work summarized the current knowledge about hip dislocation to help surgeons understand the changes in the hip biomechanics after its replacement and the impact of each element involved. This knowledge may help a surgeon to choose the most favorable surgical method and the most appropriate implant to reduce the risk of its dislocation.

Environmental enrichment in finishing pigs: does it promote any changes in bone biomechanics?

The resistance of pigs' bone structure was evaluated for the first time, reared with and without environmental enrichment (EE) in the finishing phase using techniques in bone biomechanics; 432 swine from the Hampshire breed, being males and females, with initial body weight between 22 and 27kg and final body weight between 110 and 125kg were evaluated for 112days. The experimental design was in randomized blocks, with 6 treatments, distributed in a 2 × 3 factorial scheme (sex × conditions in creation), with 12 repetitions/treatment, totaling 72 pens. The treatments were as follows: branched chain for males (T1), sisal branched string for males (T2), males without EE (T3), branched chain for females (T4), sisal branched string for females (T5), and females without EE (T6). At the end of the experimental period, all animals were slaughtered in an industrial slaughterhouse, having their femur bones collected for bone biomechanics analysis. There was no effect (P > 0.05) of the interaction (enrichment × sex) and individual factors for bone weight. There was a tendency (P = 0.08) of the interaction for flexion force, being higher in males enriched with branched ropes and chains. For breaking stress, there was an interaction effect (P = 0.04), being the females without EE the ones showing the lowest breaking stress, favoring bone fragility. The use of branched ropes and chains strengthens the bone structure in swine in the termination phase (110-125kg BW - 183-190days in age), being an important strategy used to meet the animal welfare requirements.

Changes in corneal biomechanics and posterior corneal surface elevation after FS-LASIK.

To investigate the changes in corneal biomechanics and posterior corneal surface elevation after femtosecond laser-assisted in situ keratomileusis (FS-LASIK). Totally 197 eyes of 100 patients who underwent the FS-LASIK from April 2022 to November 2022 were included. They were divided into three groups according to the ratio of residual corneal stroma thickness/corneal thickness (RCST/CT): Group I (50%≤RCST/CT<55%, 63 eyes of 32 patients), Group II (55%≤RCST/CT<60%, 67 eyes of 34 patients), and Group III (RCST/CT≥60%, 67 eyes of 34 patients). The intraocular pressure (IOP), corneal compensated IOP (IOPcc), corneal hysteresis (CH) and corneal resistance factor (CRF) were measured immediately, 1, and 3mo postoperatively by ocular response analyzer (ORA) and the posterior elevation difference (PED) was measured by Pentacam. After operation, IOP, CH, CRF, and PED were statistically different among the three groups (F=12.99, 31.148, 23.998, all P<0.0001). There was no statistically significant difference in IOPcc among the three groups (F=0.603, P>0.05). The IOP, IOPcc, CH, and CRF were statistical changed after surgery (F=699.635, 104.125, 308.474, 640.145, all P<0.0001). The PED of Group I was significantly higher than that of Group II (P<0.05), and Group II was significantly higher than that of Group III (P<0.05). The PED value of 3mo after surgery decreased in each group compared with 1mo after surgery, but there was no statistical difference (Group I: t=0.82, P=0.41; Group II: t=0.17, P=0.87; Group III: t=1.35, P=0.18). The correlation analysis of corneal biomechanical parameter changes with PED at 1mo and 3mo after surgery showed that ΔIOP, ΔIOPcc, ΔCH, and ΔCRF were not correlated with PED value in three groups (P>0.05). The smaller the RCST/CT, the greater effect on corneal biomechanics and posterior surface elevation. There is no correlation between changes in corneal biomechanics and posterior corneal surface elevation in the range of RCST/CT≥50%.

Mechanical wall stress and wall shear stress are associated with atherosclerosis development in non-calcified coronary segments

Background and aimsAtherosclerotic plaque onset and progression are known to be affected by local biomechanical factors. Whereas the role of wall shear stress (WSS) has been studied, the impact of another biomechanical factor, namely mechanical wall stress (MWS), remains poorly understood. In this study, we investigated the association of MWS, independently and combined with WSS, towards atherosclerosis in coronary arteries. MethodsThirty-four human coronary arteries were analyzed using near-infrared spectroscopy intravascular ultrasound (NIRS-IVUS) and optical coherence tomography (OCT) at baseline and after 12 months. Baseline WSS and MWS were calculated using computational models, and wall thickness (ΔWT) and lipid-rich necrotic core size (ΔLRNC) change were measured in non-calcified coronary segments. The arteries were further divided into 1.5 mm/45° sectors and categorized as plaque-free or plaque sectors. For each category, associations between the biomechanical factors (WSS & MWS) and changes in the coronary wall (ΔWT & ΔLRNC) were studied using linear mixed models. ResultsIn plaque-free sectors, higher MWS (p < 0.001) was associated with greater vessel wall growth. Plaque sectors demonstrated wall thickness reduction over time, likely due to the medical therapy, where higher levels of WSS and WMS, individually and combined, (p < 0.05) were associated with a greater reduction. Sectors with low MWS combined with high WSS demonstrated the highest LRNC increase (p < 0.01). ConclusionsIn this study, we investigated the association of the (largely-overlooked) biomechanical factor, MWS with coronary atherosclerosis, individually and combined with WSS. Our results demonstrated that both MWS and WSS significantly correlate with atherosclerotic plaque initiation and development.