ORCID Profile
0000-0002-6027-4594
Current Organisations
Hong Kong Polytechnic University
,
Hong Kong Polytechnic University Shenzhen Research Institute
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Publisher: Journal of Rehabilitation Research & Development
Date: 2004
DOI: 10.1682/JRRD.2004.01.0003
Abstract: Monolimb refers to a kind of transtibial prostheses having the socket and shank molded into one piece of thermoplastic material. One of its characteristics is that the shank is made of a material that can deform during walking, which can simulate ankle joint motion to some extent. Changes in shank geometry can alter the stress distribution within the monolimb and at the residual limb-socket interface and, respectively, affect the deformability and structural integrity of the prosthesis and comfort perceived by utees. This paper describes the development of a finite-element model for the study of the structural behavior of monolimbs with different shank designs and the interaction between the limb and socket during walking. The von Mises stress distributions in monolimbs with different shank designs at different walking phases are reported. With the use of distortion energy theory, possible failure was predicted. The effect of the stiffness of the monolimb shanks on the stress distribution at the limb-socket interface was studied. The results show a trend--the peak stress applied to the limb was lowered as the shank stiffness decreased. This information is useful for future monolimb optimization.
Publisher: Elsevier BV
Date: 04-2005
DOI: 10.1016/J.APMR.2004.08.005
Abstract: To compare the pain threshold (the minimum pressure inducing pain) and pain tolerance (the maximum tolerable pressure) of different regions of the residual limbs of utees by the indentation method and to evaluate the interface pressure distribution and distortion of the skin surface on indentation by finite element (FE) analysis. Crossover trial. Rehabilitation engineering center. Eight transtibial utees for indentation test and 1 for FE analysis. The load applied to the residual limbs using a Pelite or polypropylene indenter attached to a force transducer was increased until subjects could no longer tolerate the load. An FE model was built to simulate the indentation process with the experimentally recorded pain threshold used to load the indenters against the soft tissues. Pain threshold and tolerance and interface pressure and distortion of soft tissues. The patellar tendon and distal end of the fibula were the best and the worst load-tolerant regions, respectively. Some regions with a thicker layer of soft tissue had lower pain thresholds and tolerance than those with a thinner tissue layer. There was a trend for pain threshold and tolerance to decrease with age. The FE model showed that the peak pressure at the skin surface was very close when both indenters were loaded against the soft tissue at pain threshold limit. Contrary to common beliefs, regions with a thicker layer of soft tissue did not have a higher load-tolerant ability than thin-skinned regions. Pain threshold and tolerance could be age dependent. The FE model suggests that pain is triggered when peak pressure is applied to the residual limb exceeding a certain limit.
Publisher: Springer Science and Business Media LLC
Date: 12-2011
Publisher: Elsevier BV
Date: 07-2016
DOI: 10.1016/J.APMR.2015.12.016
Abstract: To evaluate a newly developed biofeedback device enabling lower-limb utees to identify various floor conditions. Self-control with repeated measures (with and without the biofeedback device) within the utee group, and group control comparing between utee and non utee groups. University locomotion laboratory. Five lower-limb utees and 8 non utees (N=13). A wearable biofeedback device, which identified different floor conditions by analyzing the force patterns under the prosthetic feet and provided vibration cues in response to different floor conditions, was provided to the utees. The subjects stepped on a foam platform concealing a small object or no object at 1 of the 4 locations of the foot sole. Subjects were asked whether there was a small object under their feet and the location of the object if it existed. The test was repeated with 4 different object types and 4 object locations. The success rate of floor identification was evaluated. Without the biofeedback device, non utee subjects (76.56%) identified floor conditions better than utees (22.5%) significantly (P<.001). On using the biofeedback device, the utees significantly improved (P<.01) their success rate showing no significant difference (P=.746) compared with the non utees. No significant differences were found among object types (P=.689). Amputees performed significantly worse than non utees in recognizing the different floor conditions used in this experiment. With the biofeedback device, utees significantly improved their abilities in identifying different floor conditions. Future attempts could configure the device to allow it to provide warning signals in response to fall-inducing conditions.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2006
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 04-2006
DOI: 10.1080/03093640500468074
Abstract: This paper reports findings of experiments aiming to (1) compare the load tolerant ability over different regions of stumps of lower limb utees, (2) study the effect of walking on the load tolerant ability, and (3) examine the distal-end weight-bearing ability supported by different interface materials. The method was to apply increasing load to the stump up to the pain level through a force transducer or a digital scale, considering the effect of regional difference, walking, and interface materials. The results show that the patellar tendon and the distal end of the fibula were the best and worst load-tolerant region, respectively. Walking with prostheses tended to increase the load-tolerant ability, which is thought to be due to the massage-like effect of the socket. Different interface materials did not significantly alter the distal-end weight-bearing ability. However, there was a great difference in the distal-end weight-bearing ability among different subjects.
Publisher: SAGE Publications
Date: 25-10-2011
Abstract: Well-designed compression sportswear can be used for the enhancement of athletic performance and reduction of injury. The material and geometric properties of fabric for compression sportswear are vital in achieving compression effects. This study evaluated and optimized the performance of fabric using the design of experiment (DOE) methods, the response surface method (RSM) and the finite element (FE) model. The evaluation and optimization procedure consisted of three phases. The first phase involved developing the FE model of a fabric tube and cylinder, and validated it by compression experiments involving different fabrics. The second phase evaluated the FE prediction using a five-factor experimental design, namely, hyperelastic properties, thickness, density, friction, and tensile strain. The third and final phase was an optimization process using RSM based on the evaluation results. Findings show that the FE predictions approach closely the results of validation experiments. The nonlinear elastic material properties (hyperelastic properties) and shape dimensions (thickness and tensile strain) of fabric tube were found to be important design factors in influencing contact pressure, while the density of fabric and interface friction coefficient played less important roles. The optimal FE model was determined using RSM analysis. The statistically based FE model was found to be an effective approach for evaluating and optimizing the design parameters of fabric for compression sportswear. The results can be applied to make sportswear that has different compression effects at selected anatomical locations to enhance performance and reduce injuries.
Publisher: Informa UK Limited
Date: 20-09-2012
DOI: 10.3109/09638288.2012.712197
Abstract: Many trans-tibial utees could not tolerate long-distance walking. Lack of walking could explain for the increased cardiovascular diseases mortality rate. This study investigated the effects of long-distance walking (LDW) on socket-limb interface pressure, tactile sensitivity of the residual limb, and subjective feedbacks, which potentially identified the difficulties in LDW. Five male unilateral trans-tibial utees walked on a level treadmill for a total of one hour at comfortable speed. Tactile sensitivity of the residual limb and socket-limb interface pressure during over-ground walking were measured before and after the treadmill walking. Modified Prosthesis Evaluation Questionnaires were also administered. After the treadmill walking, the socket-limb interface pressure and the tactile sensitivity at the popliteal depression area were significantly reduced. This corresponds well with the questionnaire results showing that the level of discomfort and pain of the residual limb did not increase. The questionnaire revealed that there were significant increases in fatigue level at the sound-side plantar flexors, which could lead to impaired dynamic stability. Fatigue of sound-side plantar-flexor was the main difficulty faced by the five subjects when walking long-distances. This finding might imply the importance of refining prosthetic components and rehabilitation protocols in reducing the muscle fatigue. • After long-distance walking (LDW) of the trans-tibal utee subjects, there were significant increases in fatigue level at the plantar flexors. These might explain the reduced walking stability as perceived by the subjects. • LDW did not produce any problems in residual-limb comfort and pain feeling. These were in line with the significant reductions of socket-limb interface pressure and the tactile sensitivity at the popliteal depression after LDW. • Refinements of prosthetic components and rehabilitation protocols should be attempted to reduce the fatigue of the plantar flexors and facilitate LDW.
Publisher: Elsevier BV
Date: 09-2004
Publisher: Springer Berlin Heidelberg
Date: 2007
Publisher: Elsevier BV
Date: 02-2012
DOI: 10.1016/J.GAITPOST.2011.10.004
Abstract: Trans-tibial utees are advised to walk as much as able people to achieve healthy and independent life. However, they usually have difficulties in doing so. Previous researches only included data from a few steps when studying the gait of utees. Walking over a long distance was rarely examined. The objective of this study was to investigate the changes in spatial-temporal, kinetic and kinematic gait parameters of trans-tibial utees after long-distance walking. Six male unilateral trans-tibial utees performed two sessions of 30-min walking on a level treadmill at their self-selected comfortable speed. Gait analysis was undertaken over-ground: (1) before walking, (2) after the 1st walking session and (3) after the 2nd walking session. After the long-distance walking, changes in spatial-temporal gait parameters were small and insignificant. However, the sound side ankle rocker progression and push-off were significantly reduced. This was due to the fatigue of the sound side plantar flexors and was compensated by the greater effort in the prosthetic side. The prosthetic side knee joint showed significantly increased flexion and moment during loading response to facilitate the anterior rotation of the prosthetic shank. The prosthetic side hip extensors also provided more power at terminal stance to facilitate propulsion. Endurance training of the sound side plantar flexors, and improvements in the prosthetic design to assist anterior rotation of the prosthetic shank should improve long-distance walking in trans-tibial utees.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-2006
DOI: 10.1080/03093640600864172
Abstract: Monolimb refers to a kind of trans-tibial prostheses with the socket and shank moulded into one piece of thermoplastic material. If properly designed, the shank of a monolimb can deflect which may compensate for the lost ankle plantarflexion and dorsiflexion to some extent. However, provision of shank flexibility is usually accompanied by reduced structural strength of the entire prosthesis. In the recent work using finite element analysis and the Taguchi method, the dimensions of the shank for the monolimb were derived which aimed at giving high shank flexibility and reasonable strength to resist static load. Yet, fatigue testing has not been performed. Fatigue failure may happen when a relatively low level of load is applied repeatedly. This study aimed to document the fatigue life of two flexible-shank monolimbs, by applying cyclic force of 800 N at the forefoot region for 500,000 cycles. Results showed that the design of the foot bolt adaptor played an important role in the structural integrity of the monolimb. One monolimb completed the fatigue test of 500,000 cycles without visual material yield, but with 3.8 degrees change in dorsiflexion angle when the load was removed.
Publisher: Elsevier BV
Date: 10-2004
DOI: 10.1016/J.MEDENGPHY.2004.04.010
Abstract: Finite element method has been identified as a useful tool to understand the load transfer mechanics between a residual limb and its prosthetic socket. This paper proposed a new practical approach in modeling the contact interface with consideration of the friction/slip conditions and pre-stresses applied on the limb within a rectified socket. The residual limb and socket were modeled as two separate structures and their interactions were simulated using automated contact methods. Some regions of the limb penetrated into the socket because of socket modification. In the first step of the simulation, the penetrated limb surface was moved onto the inner surface of the socket and the pre-stresses were predicted. In the subsequent loading step, pre-stresses were kept and loadings were applied at the knee joint to simulate the loading during the stance phase of gait. Comparisons were made between the model using the proposed approach and the model having an assumption that the shape of the limb and the socket were the same which ignored pre-stress. It was found that peak normal and shear stresses over the regions where socket undercuts were made reduced and the stress values over other regions raised in the model having the simplifying assumption.
Publisher: Springer Berlin Heidelberg
Date: 2007
Publisher: Elsevier BV
Date: 10-2007
DOI: 10.1016/J.MEDENGPHY.2006.09.008
Abstract: This study illustrates the use of computational analysis to predict prosthetic socket fit. A simple indentation test is performed by applying force to the residual limb of a trans-tibial utee through an indenter until the subject perceives the onset of pain. Computational finite element (FE) analysis is then applied to evaluate the magnitude of pressure underlying the indenter that initiates pain (pain threshold pressure), and the pressure at the prosthetic socket-residual limb interface. The assessment of socket fit is examined by studying whether or not the socket-limb interface pressure exceeds the pain threshold pressure of the limb. Based on the computer-aided assessment, a new prosthetic socket is then fabricated and fitted to the utee subject. Successful socket fit is achieved at the end of this process. The approach of using computational analysis to aid in assessing socket fit allows a more efficient evaluation and re-design of the socket even before the actual fabrication and fitting of the prosthetic socket. However, more thorough investigations are required before this approach can be widely used. A subsequent part of this paper discusses the limitations and suggests future research directions in this area.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 08-2013
Abstract: Prosthetic alignment is usually unchanged once optimized. However, a previous study indicated that long-distance walking significantly altered gait patterns, suggesting some alignment adjustments after walking are required. This study investigated the effects of alignment changes (by inserting a heel lift) on gait of a transtibial utee before and after treadmill walking. The subject walked, without heel lifts, on a treadmill until perception of fatigue. Gait changes upon heel lifting at the prosthetic side were studied before and after the treadmill walking For this subject before the treadmill walking, heel lifting induced drop-off with increased prosthetic-side knee flexion at mid-stance and pre-swing. The sound limb outreached to stabilize the gait. After the treadmill walking, the same heel lift did not induce drop-off. It reduced the plantar flexor power generation, potentially delaying its fatigue. After walking prosthetic-side heel lifting could be beneficial. Many lower-limb utees have difficulties in long-distance walking due to muscle fatigue. This case study proposes that appropriate alignment changes after some walking potentially relieve fatigue and encourage them to walk longer distances.
Publisher: Elsevier BV
Date: 08-2005
DOI: 10.1016/J.CLINBIOMECH.2005.03.015
Abstract: Monolimb is a transtibial prosthesis having the socket and shank molded into one piece of thermoplastic material. If properly designed, the shank of a monolimb can have a controlled deflection during walking which simulates the ankle joint motions to some extent. However, there is no clear guidance for the design of monolimb considering the dilemma between shank flexibility and structural integrity. Finite element analysis was used to simulate structural tests based on ISO10328 on monolimbs of different configurations. Statistics-based Taguchi method was employed to identify the significance of each design factor in controlling the deformation and stress within monolimbs. The design factors considered were the thickness of the thermoplastics, anteroposterior and medialateral dimensions of the elliptical shank, and depth of the posterior seam line. By progressively fine-tuning the design factors, the monolimb configuration was optimized giving offering appropriate flexibilities of the shank and would not structurally fail in normal uses. Experimental structural test was used to validate the finite element model. Anteroposterior dimension of the shank was shown to be the most important design factor determining the peak von Mises stress values, deformation and dorsiflexion angles of monolimbs. Depth of seam line appears much less important than the other three factors. A monolimb fulfilling the design requirements was suggested. Experimental test results reasonably matched with the finite element results. Finite element analysis and Taguchi method was shown to be an effective method in optimizing the structural design of prostheses. Further prosthetic design can be facilitated based on the degree of importance of the design factors on the structural behavior of the prosthesis. Gait analysis of utees using the suggested monolimb design is needed in the future.
Publisher: Elsevier BV
Date: 03-2006
DOI: 10.1016/J.CLINBIOMECH.2005.10.002
Abstract: Except the plantar pressure and gross joint motion, we know little about the mechanical state of a foot during walking. This study aimed at investigating the effect of wearing socks with different frictional properties on plantar shear, which is a possible mechanical risk factor of foot lesion development. A 3-D finite element model for simulating the foot-sock-insole contact was developed to investigate the biomechanical effects of wearing socks with different combinations of frictional properties on the plantar foot contact. The dynamic plantar pressure and shear stress during the stance phases of gait were studied through finite element computations. Three cases were simulated, a barefoot with a high frictional coefficient against the insole (0.54) and two socks, one with a high frictional coefficient against the skin (0.54) and a low frictional coefficient against the insole (0.04) and another with an opposite frictional properties assignment. Wearing sock of low friction against the insole to allow more relative sliding between the plantar foot and footwear was found to reduce the shear force significantly: at the rearfoot from 3.1 to 0.88 N, and at the forefoot from 10.61 to 1.61 N. The shear force can be further reduced to 0.43 N at the rearfoot, and 1.18 N at the forefoot, when wearing the sock with low friction against the foot skin and high friction set against the insole. Wearing sock with low friction against the foot skin was found to be more effective in reducing plantar shear force on the skin than the sock with low friction against the insole. The risk of barefoot walking in developing plantar shear related blisters and ulcers might be reduced by socks wearing especially those with low friction against the foot skin.
Publisher: Elsevier BV
Date: 04-2006
DOI: 10.1016/J.MEDENGPHY.2005.07.002
Abstract: Monolimb refers to a transtibial prosthesis with the prosthetic socket and the shank being molded into one piece of thermoplastic material. Shank flexibility of a monolimb can improve gait and comfort. However, fatigue failure of monolimbs under cyclic walking load is an important concern. This study is to evaluate the fatigue life of a monolimb designed for a transtibial utee, based on finite element analysis, the statistical Miner's rule and reliability analysis. Stress uncertainty due to modeling error and the scatter in fatigue test data were considered. Results indicated that the accuracy of fatigue life evaluation of monolimb depends significantly on the precision of stress estimation. In addition, relationship between fatigue failure probability and the number of walking steps was suggested providing a reference for clinicians to determine the interval of the inspection for the monolimb.
Publisher: Elsevier BV
Date: 07-2005
DOI: 10.1016/J.CLINBIOMECH.2005.03.001
Abstract: To predict the interface pressure between residual limb and prosthetic socket for trans-tibial utees during walking. A quasi-dynamic finite element model was built based on the actual geometry of residual limb, internal bones and socket liner. To simulate the friction/slip boundary conditions between the skin and liner, automated surface-to-surface contact was used. Besides variable external loads and material inertia, the coupling between the large rigid displacement of knee joint and small elastic deformation of residual limb and prosthetic components were also considered. Interface pressure distribution was found to have the same profile during walking. The high pressures fall over popliteal depression, middle patella tendon, lateral tibia and medial tibia regions. Interface pressure predicted by static or quasi-dynamic analysis had the similar double-peaked waveform shape in stance phase. The consideration of inertial effects and motion of knee joint cause 210% average variation of the area between the pressure curve and the horizontal line of pressure threshold between two cases, even though there is only a small change in the peak pressure. The findings in this paper show that the coupling dynamic effects of inertial loads and knee flexion must be considered to study interface pressure between residual limb and prosthetic socket during walking.
Location: United Kingdom of Great Britain and Northern Ireland
Location: China
No related grants have been discovered for Ming Zhang.