Papers by Keyword: Biomechanics

Abstract: Understanding the complex biomechanical behaviour of the injured and meniscectomised knee joints is of utmost significance in various clinical circumstances. The objective of this study is to investigate the effects of bucket handle tears in the medial meniscus and subtotal medial meniscectomies on the biomechanical response of the knee joints belonging to multiple subjects. The three-dimensional (3D) finite element models of human knee joints including bones, cartilages, menisci, ligaments and tendons are developed from magnetic resonance images (MRI) of multiple healthy subjects. The knee joints are subjected to an axial compressive force, which corresponds to the force of the gait cycle for the full extension position of the knee joint. Three different conditions are compared: intact knee joints, knee joints with bucket handle tears in the medial meniscus and knee joints after subtotal meniscectomies. The bucket handle tear causes a considerable rise in the maximum principal stress at its tip compared to that at the same location in the intact meniscus. This would cause the total rupture of the meniscus resulting in cartilage damage. Subtotal meniscectomy causes a considerable reduction in the contact area along with a substantial increase in the contact pressure and maximum compressive stress in the cartilages in comparison with that in the intact knee. This could give rise to severe degenerative changes in the cartilage. The results of this study could help surgeons in making clinical decisions when managing patients with meniscal injuries.

Abstract: High-intensity intermittent training (HIIT) has been successfully applied in various sports activities, as HIIT was considered as one of the most efficient training methods of exercise for improving physical performance and reducing the weight of overweight individuals. However, its acute effects of HIIT on gait and balance performance were not addressed. Thus, in this study we examined the acute effects of HIIT on dynamic postural control compared with steady-state training (SST) by analyzing plantar pressure parameters. In this study, sixteen healthy male adults were examined in 3 days. After exhaustive ramp-like cycle ergometer testing, the maximal heart rate (HR_max) of each participant was determined on the first day, then either a 20 minutes HIIT at 80–90% of HR_max or a 20 minutes SST at 60% of HR_max was randomly performed on the second and third day, respectively. Plantar pressure parameters were collected at comfortable walking velocity immediately after HIIT and SST respectively, and compared with the baseline data of plantar pressure gathered before maximal ramp test on the first day. The results showed significant differences in the plantar pressure in these three conditions of gait. Compared to pre-intervention and pre-SST, peak pressure and maximum force in the middle and lateral metatarsal increased significantly in post-HIIT. Meanwhile, the foot balance data indicate that post-HIIT exhibits more foot pronation than baseline. The center of pressure (COP) trajectory was medially shifted during the stance phase in post-SST, and noticeably in post-HIIT. The displacement and velocity of medial-lateral COP in the initial contact phase were greater in post-HIIT; while during the forefoot contact phase, post-HIIT showed fewer time percentages and greater velocity of medial-lateral COP. In conclusion, a single high-intensity intermittent training session adversely affected the acute dynamic postural control than steady-state training in healthy male adults.

Abstract: Many scientific data have proven that regular wearing of high-heeled shoes adversely affects human health. Recent evidence suggested that bionic heels imitated hoofed animals have attracted widespread attention. However, few biomechanical studies have investigated the effects of bionic high-heeled footwear on the lower limbs. Accordingly, this study aimed to examine the impact of bionic high-heeled shoes (HHS) on the biomechanical characteristics of lower limbs by comparing kinematics and kinetics of walking in HHS and bionic flat-bottomed shoes (FBS). they find that when the subjects wore HHS, the loading is concentrated in the forefoot region for a much longer time. Couple with HHS lacks the cushioning effect of the complete sole, the sole has to rely only on plantar flexion and dorsiflexion of the ankle joint to cushion the impact force, which will undoubtedly increase the fatigue damage of the ankle joint. The unique split-toe structure balances the loading between the toes could reduce the risk of toes injury during walking. However, there are still risks of injury to the lower limbs of HHS, especially the ankle and knee joints.

Abstract: This research was conducted to provide a feasible method for reconstructing the 3D model of mandibular bone to undergo finite element analysis to investigate von Mises stress, deformation and shear stress located at the cortical bone, cancellous one and neck implant of the proposed dental implant design. Dental implant has become a significant remedial approach but although the success rate is high, the fixture failure may happen when there are insufficient host tissues to initiate and sustain the osseointegration. Computerised Tomography scan was conducted to generate head images for bone reconstruction process. MIMICS software and 3-matic software were used to develop the 3D mandibular model. The reconstructed mandibular model was then assembled with five different 3D models of dental implants. Feasible boundary conditions and material properties were assigned to the developed muscle areas and joints. The highest performance design with the best responses was the design B with the value for the von Mises stress for the neck implant, cortical and cancellous bone were 7.53 MPa, 16.91 MPa and 1.34 MPa respectively. The values for the maximum of micromotion for the neck implant, cortical and cancellous bone of design B were 20.60 μm, 21.17 μm and 5.83 μm respectively. Shear stress for neck implant, cortical and cancellous bone for this design were 0.15 MPa, 4.74 MPa and 1.54 MPa respectively. The design with a cone shaped hole which is design B was the proper design when compared with other designs in terms of von Misses stress, deformations and shear stress.

Abstract: The great potentials of wood species have not yet been fully tapped in Ecuador in order to propose feasible and eco-friendly alternatives that allow reducing/replacing conventional building materials. This investigation aims to determine the physical-mechanical properties of lightweight bidirectional sandwich-like composite wall panels made of bamboo (Dendrocalamus asper), melina (Gmelina arborea) and balsa (Ochroma pyramidale). To fulfil this purpose, 80 samples from four prototype biopanels were tested in accordance to the current American Society for Testing and Materials (ASTM) standards. The experimental results were validated and compensated by performing a total of 79 finite element analyses (FEA) that in turn allowed evaluating and analyzing both the mechanical efficiency and the biomechanical performance of the proposed biopanels. The results in this investigation showed sandwich-like composite wall biopanels with an enhanced mechanical efficiency that is up to nine times higher than steel, concrete, aluminum, wood and bricks. Results from the biomechanical analyses confirm the practical utilization of the proposed biopanels in low-rise and mid-rise buildings (i.e. between two and ten stories) located in high-risk seismic and windy regions. Thus, its implementation in the actual construction system will definitely implicate important upgrades in terms of structural optimization and sustainable practices. Indeed, the proposed wall biopanels are meant to be used in the rebuilding process of the dramatically affected areas during the 2016 Ecuador earthquake.

Abstract: Generally, implants fixations in orthopedic surgery are insured by bone cement; which is generated mainly from polymer polymethylmethacrylate (PMMA). Since, the cement is identified as the weakest part among bone-cement-prosthesis assembly. Hence, the characterization of mechanical behaviour is of a crucial requirement for orthopaedic surgeon’s success. In this study, we investigates the failure behaviour of bone cement, under combined shear and compression loading, for the aim to determine the strengths of bone cement for different mode loading conditions. Therefore, experimental cylindrical specimens has been tested to assess different shear-compression stresses. Based on the mechanical tests, a finite elements model of cylindrical specimens was developed to evaluate stresses distribution in the bone cement under compression, shear and combined shear-compression loading. Results show that, the load which leading to the failure of the cement decreased with increasing of the specimen angle inclination with respect of loading direction.

Abstract: Gait in children with cerebral palsy (CP) is often affected by motor impairments which limit the patient's ability to walk. To improve gait and reduce walking limitations, children with CP need to use ankle foot orthoses. An orthosis is an externally applied device that is designed and fitted to the body to achieve one or more of the following goals: a) Control biomechanical alignment. b) Correct or accommodate deformity, and 3) Protect and support an injury. This systematic review aims to describe research evidence supporting the use of ankle-foot orthoses to improve gait biomechanical outcomes among individuals with CP. Literature search was pursued from PubMed database. Studies were included if (1) they evaluated an outcome measure related with gait using ankle-foot orthotic (AFO) in children (2) considered children with a diagnosis of CP and have a (3) GMFCS classification of I, II or III. Papers were excluded if they evaluated (1) other population besides CP, (2) the use of orthoses other than AFOs and (3) gait analysis procedure was not presented. All the included studies have analyzed spatiotemporal parameters, the step length (m), stride length (m) and cadence (steps/minute) were the most frequently reported. Our findings showed that several studies have investigated the effects of AFOs, all of which have reported positive influences on at least one gait parameter, as well as positive changes in joint kinematics and kinetic in children with CP.

Abstract: In recent years, sheep have been reported as the ideal animal model to study osteoporosis, hence it is important to identify instruments, tools and ideal parameters needed to assess the effects of different treatments. In previous studies conducted in other animal models with osteoporosis, the most common parameters used for evaluation concerned primarily bone properties, such as the dual X-ray absorptiometry. However, biomechanical gait analysis as an integrative functional parameter and a non-invasive method, will be an important tool in research and clinical applications. This research review was performed using the PubMed database and included studies related to sheep with outcome measures concerning functional performance assessed during gait in vivo; and excluded studies related with cardiovascular disease and sperm properties, which include other animal species, with outcomes not related with functional locomotor evaluation. Only studies related with bone properties were analyzed. The most frequent and relevant included parameters were the following: mean peak vertical ground force reaction, gait cycle and stance/swing phase duration, percentage of stance/swing phase in a gait cycle, stride length and the stifle joint angles during a gait cycle. Gait biomechanical parameters have been established for the assessment of some clinical orthopedic condition using sheep models but not currently for osteoporosis.

Abstract: The purpose of this study was to examine the acute effects of different stretching techniques on performance and lower limb kinematics, kinetics and muscle activities during vertical jump in female aerobics athletes. 10 female college aerobics athletes participated in this study. Three-dimensional kinematic and kinetic data, as well as electromyography of rectus femoris, biceps femoris and gastrocnemius medialis were collected using Vicon motion analysis system, Kistler force plate and Wireless surface electromyographic system respectively during the test. No significant differences in jump height had been determined among these 3 warm-up methods. Hip peak flexion and internal rotation angles decreased significantly after BSM and peak adduction angle decreased significantly after SSM and BSM during landing. Knee peak flexion and internal rotation angles increased significantly after SSM and BSM during take-off. Also, BSM showed significantly greater peak flexion compared with SSM. Ankle peak plantarflexion angle increased significantly after BSM. In addition, BSM showed significantly greater improvement in the variation range than SSM except for the ankle int-external rotation. Existence of no significant differences in the peak value of vertical ground reaction force during take-off and landing phase had been determined among these 3 warm-up methods, and muscle activities of rectus femoris, biceps femoris and gastrocnemius medialis were likewise not significantly different. The results of this study suggest that it would be suitable for female aerobics athletes to perform ballistic stretching in warm-up in order to improve flexibility without decreasing the following vertical jumping event and may also reduce the risk of ankle sprain injury.

Abstract: The design of modern footwear seems to have an excessive protective effect on the function of the foot. The purpose of this study was to examine how bionic shoes designed would influence the biomechanical index of gait patterns. There were 10 male subjects underwent gait analysis. Normal sports shoes (NS) with flat-soles were selected as control shoes. The experimental shoes comprising of two elasticity levels were defined as soft-sole bionic shoes (SS) and hard-sole bionic shoes (HS). We examined ground reaction forces, plantar pressures and angles of the ankle, knee and hip during walking and jogging conditions. In comparison with standard shoes, wearing bionic shoes reduced the range of motion in some joints during movement and changed the peak angle in the sagittal, frontal and horizontal planes. Moreover, the vertical average loading rates were significantly larger than that of the standard shoes during jogging. The experimental groups showed larger PP or PTI in the foot regions examined except in the lateral forefoot. Also, increases the in the contact area of the midfoot with decreases in the contact area in heel were also observed. In some regions of the foot, the hard sole of the bionic shoes had a lower pressure than that of the soft sole. These findings indicate that the design of the bionic sole in this study can be used to increase toe scratching ability, increase neuromuscular strength and enhance stability and proprioceptive ability. However, the higher plantar pressures in some regions may increase the risk of overuse injuries. The findings from the study indicate preference for the hard bionic shoes during exercise compared to the soft sole.