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Plesec V, Humar J, Dobnik-Dubrovski P, Harih G. Numerical Analysis of a Transtibial Prosthesis Socket Using 3D-Printed Bio-Based PLA. MATERIALS (BASEL, SWITZERLAND) 2023; 16:1985. [PMID: 36903100 PMCID: PMC10004398 DOI: 10.3390/ma16051985] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 02/21/2023] [Accepted: 02/24/2023] [Indexed: 06/18/2023]
Abstract
Lower-limb prosthesis design and manufacturing still rely mostly on the workshop process of trial-and-error using expensive unrecyclable composite materials, resulting in time-consuming, material-wasting, and, ultimately, expensive prostheses. Therefore, we investigated the possibility of utilizing Fused Deposition Modeling 3D-printing technology with inexpensive bio-based and bio-degradable Polylactic Acid (PLA) material for prosthesis socket development and manufacturing. The safety and stability of the proposed 3D-printed PLA socket were analyzed using a recently developed generic transtibial numeric model, with boundary conditions of donning and newly developed realistic gait cycle phases of a heel strike and forefoot loading according to ISO 10328. The material properties of the 3D-printed PLA were determined using uniaxial tensile and compression tests on transverse and longitudinal samples. Numerical simulations with all boundary conditions were performed for the 3D-printed PLA and traditional polystyrene check and definitive composite socket. The results showed that the 3D-printed PLA socket withstands the occurring von-Mises stresses of 5.4 MPa and 10.8 MPa under heel strike and push-off gait conditions, respectively. Furthermore, the maximum deformations observed in the 3D-printed PLA socket of 0.74 mm and 2.66 mm were similar to the check socket deformations of 0.67 mm and 2.52 mm during heel strike and push-off, respectively, hence providing the same stability for the amputees. We have shown that an inexpensive, bio-based, and bio-degradable PLA material can be considered for manufacturing the lower-limb prosthesis, resulting in an environmentally friendly and inexpensive solution.
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Affiliation(s)
- Vasja Plesec
- Laboratory for Intelligent CAD Systems, Faculty of Mechanical Engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, Slovenia
| | - Jani Humar
- Laboratory for Intelligent CAD Systems, Faculty of Mechanical Engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, Slovenia
| | - Polona Dobnik-Dubrovski
- Mechanical Engineering Research Institute, Faculty of Mechanical Engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, Slovenia
| | - Gregor Harih
- Laboratory for Intelligent CAD Systems, Faculty of Mechanical Engineering, University of Maribor, Smetanova ulica 17, 2000 Maribor, Slovenia
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Zainuddin NAMN, Razak NAA, Karim MSA, Osman NAA. Surface profile analysis of laminated transfemoral prosthetic socket fabricated with different ratios of epoxy resin and acrylic resin. Sci Rep 2023; 13:2664. [PMID: 36792914 PMCID: PMC9932096 DOI: 10.1038/s41598-022-21990-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Accepted: 10/07/2022] [Indexed: 02/17/2023] Open
Abstract
Acrylic and epoxy are common types of resin used in fabricating sockets. Different types of resin will affect the internal surface of a laminated socket. This paper is to determine the best combination of ratio for epoxy and acrylic resin for a laminated prosthesis socket and to evaluate the surface profile analysis of different combinations of laminated prosthetic sockets for surface roughness. Transfemoral sockets were created using various resin-to-hardener ratios of 2:1, 3:1, 3:2, 2:3, and 1:3 for epoxy resin and 100:1, 100:2, 100:3, 100:4, and 100:5 for acrylic resin. Eight layers of stockinette consisting of four elastic stockinette and four Perlon stockinette were used. A sample with a size of 4 cm × 6 cm was cut out from the socket on the lateral side below the Greater Trochanter area. The Mitutoyo Sj-210 Surface Tester stylus was run through the sample and gave the Average Surface Roughness value (Ra), Root Mean Square Roughness value (Rq), and Ten-Point Mean Roughness value (Rz). Epoxy resin shows a smoother surface compared to acrylic resin with Ra values of is 0.766 µm, 0.9716 µm, 0.9847 µm and 1.5461 µm with 3:2, 3:1, 2:1 and 2:3 ratio respectively. However, for epoxy resin with ratio 1:3, the resin does not cure with the hardener. As for acrylic resin the Ra values are 1.0086 µm, 2.362 µm, 3.372 µm, 4.762 µm and 6.074 µm with 100: 1, 100:2, 100:5, 100:4 and 100:3 ratios, respectively. Epoxy resin is a better choice in fabricating a laminated socket considering the surface produced is smoother.
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Affiliation(s)
- Nik Abdul Muiz Nik Zainuddin
- grid.10347.310000 0001 2308 5949Department of Biomedical Engineering, Faculty of Engineering, Universiti Malaya, Kuala Lumpur, Malaysia
| | - Nasrul Anuar Abd Razak
- Department of Biomedical Engineering, Faculty of Engineering, Universiti Malaya, Kuala Lumpur, Malaysia.
| | - Mohd Sayuti Ab Karim
- grid.10347.310000 0001 2308 5949Department of Mechanical Engineering, Faculty of Engineering, Universiti Malaya, Kuala Lumpur, Malaysia
| | - Noor Azuan Abu Osman
- grid.10347.310000 0001 2308 5949Department of Biomedical Engineering, Faculty of Engineering, Universiti Malaya, Kuala Lumpur, Malaysia
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Neumann EE, Doherty S, Bena J, Erdemir A. Role of multi-layer tissue composition of musculoskeletal extremities for prediction of in vivo surface indentation response and layer deformations. PLoS One 2023; 18:e0284721. [PMID: 37083580 PMCID: PMC10121013 DOI: 10.1371/journal.pone.0284721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 04/05/2023] [Indexed: 04/22/2023] Open
Abstract
Emergent mechanics of musculoskeletal extremities (surface indentation stiffness and tissue deformation characteristics) depend on the underlying composition and mechanics of each soft tissue layer (i.e. skin, fat, and muscle). Limited experimental studies have been performed to explore the layer specific relationships that contribute to the surface indentation response. The goal of this study was to examine through statistical modeling how the soft tissue architecture contributed to the aggregate mechanical surface response across 8 different sites of the upper and lower extremities. A publicly available dataset was used to examine the relationship of soft tissue thickness (fat and muscle) to bulk tissue surface compliance. Models required only initial tissue layer thicknesses, making them usable in the future with only a static ultrasound image. Two physics inspired models (series of linear springs), which allowed reduced statistical representations (combined locations and location specific), were explored to determine the best predictability of surface compliance and later individual layer deformations. When considering the predictability of the experimental surface compliance, the physics inspired combined locations model showed an improvement over the location specific model (percent difference of 25.4 +/- 27.9% and 29.7 +/- 31.8% for the combined locations and location specific models, respectively). While the statistical models presented in this study show that tissue compliance relies on the individual layer thicknesses, it is clear that there are other variables that need to be accounted for to improve the model. In addition, the individual layer deformations of fat and muscle tissues can be predicted reasonably well with the physics inspired models, however additional parameters may improve the robustness of the model outcomes, specifically in regard to capturing subject specificity.
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Affiliation(s)
- Erica E Neumann
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States of America
- Computational Biomodeling (CoBi) Core, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States of America
| | - Sean Doherty
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States of America
- Computational Biomodeling (CoBi) Core, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States of America
| | - James Bena
- Quantitative Health Sciences, Cleveland Clinic, Cleveland, OH, United States of America
| | - Ahmet Erdemir
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States of America
- Computational Biomodeling (CoBi) Core, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States of America
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Amudhan K, Vasanthanathan A, Anish Jafrin Thilak J. An insight into Transfemoral Prostheses: Materials, modelling, simulation, fabrication, testing, clinical evaluation and performance perspectives. Expert Rev Med Devices 2022; 19:123-140. [PMID: 35142577 DOI: 10.1080/17434440.2022.2039624] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
INTRODUCTION A Transfemoral prosthesis restores any limb amputated above the knee. Designing and developing a transfemoral prosthesis that is consistent with human performance is a tough task. While prosthetic components are widely available in the market, ongoing research is being conducted to develop parts that would restore the lost capability, taking into account numerous social, economic and technological considerations. AREAS COVERED The present paper provides a comprehensive review about the mechanical aspects and performance of transfemoral prosthesis in recent years based on the research findings on materials, manufacturing methods and evaluations for suitability of the prostheses. The fundamental terminologies as well as technical advancements are covered in order to impart a better knowledge in the area of Lower Limb prostheses. This review also provides a concise description on the role of computers, advanced software packages, sensors and other hardware components for the design, fabrication and testing of transfemoral prosthetic devices in the current environment. EXPERT OPINION The current state of lower limb prostheses and future research opportunities are summarised to address upcoming challenges. Based on survey of various research works, adapting modern technology may aid in the development of functional and cost-efficient prosthetic components with superior safety, comfort and quality.
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Affiliation(s)
- K Amudhan
- Department of Mechanical Engineering, Mepco Schlenk Engineering College,626005, Tamilnadu, India
| | - A Vasanthanathan
- Department of Mechanical Engineering, Mepco Schlenk Engineering College,626005, Tamilnadu, India
| | - J Anish Jafrin Thilak
- Department of Mechanical Engineering, Mepco Schlenk Engineering College,626005, Tamilnadu, India
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5
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Gariboldi F, Pasquarelli D, Cutti AG. Structural testing of lower-limb prosthetic sockets: A systematic review. Med Eng Phys 2022; 99:103742. [DOI: 10.1016/j.medengphy.2021.103742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 10/29/2021] [Accepted: 12/10/2021] [Indexed: 10/19/2022]
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Nizam MAM, Razak NAA, Osman NAA, Jaladin RAM. Qualitative Study of Prosthetic Liner Materials on Transtibial Amputees’ Satisfaction in Term of Positional Pain and Discomfort. 6TH KUALA LUMPUR INTERNATIONAL CONFERENCE ON BIOMEDICAL ENGINEERING 2021 2022:205-216. [DOI: 10.1007/978-3-030-90724-2_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
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McGeehan MA, Adamczyk PG, Nichols KM, Hahn ME. A simulation-based analysis of the effects of variable prosthesis stiffness on interface dynamics between the prosthetic socket and residual limb. J Rehabil Assist Technol Eng 2022; 9:20556683221111986. [PMID: 35859652 PMCID: PMC9289901 DOI: 10.1177/20556683221111986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 06/21/2022] [Indexed: 11/23/2022] Open
Abstract
Introduction: Loading of a residual limb within a prosthetic socket
can cause tissue damage such as ulceration. Computational simulations may be
useful tools for estimating tissue loading within the socket, and thus provide
insights into how prosthesis designs affect residual limb-socket interface
dynamics. The purpose of this study was to model and simulate residual
limb-socket interface dynamics and evaluate the effects of varied prosthesis
stiffness on interface dynamics during gait. Methods: A spatial contact model of a residual limb-socket interface
was developed and integrated into a gait model with a below-knee amputation.
Gait trials were simulated for four subjects walking with low, medium, and high
prosthesis stiffness settings. The effects of prosthesis stiffness on interface
kinematics, normal pressure, and shear stresses were evaluated. Results: Model-predicted values were similar to those reported
previously in sensor-based experiments; increased stiffness resulted in greater
average normal pressure and shear stress (p < 0.05). Conclusions: These methods may be useful to aid experimental studies
by providing insights into the effects of varied prosthesis design parameters or
gait conditions on residual limb-socket interface dynamics. The current results
suggest that these effects may be subject-specific.
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Affiliation(s)
| | - Peter G Adamczyk
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Kieran M Nichols
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Michael E Hahn
- Department of Human Physiology, University of Oregon, Eugene, OR, USA
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Brown N, Owen MK, Garland A, DesJardins JD, Fadel GM. Design of a Single Layer Metamaterial for Pressure Offloading of Transtibial Amputees. J Biomech Eng 2021; 143:051001. [PMID: 33493283 PMCID: PMC10782866 DOI: 10.1115/1.4049887] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 12/20/2020] [Indexed: 11/08/2022]
Abstract
While using a prosthesis, transtibial amputees can experience pain and discomfort brought on by large pressure gradients at the interface between the residual limb and the prosthetic socket. Current prosthetic interface solutions attempt to alleviate these pressure gradients using soft homogenous liners to reduce and distribute pressures. This research investigates an additively manufactured metamaterial inlay with a tailored mechanical response to reduce peak pressure gradients around the limb. The inlay uses a hyperelastic behaving metamaterial (US10244818) comprised of triangular pattern unit cells, 3D printed with walls of various thicknesses controlled by draft angles. The hyperelastic material properties are modeled using a Yeoh third-order model. The third-order coefficients can be adjusted and optimized, which corresponds to a change in the unit cell wall thickness to create an inlay that can meet the unique offloading needs of an amputee. Finite element analysis simulations evaluated the pressure gradient reduction from (1) a standard homogenous silicone liner, (2) a prosthetist's inlay prescription that utilizes three variations of the metamaterial, and (3) a metamaterial solution with optimized Yeoh third-order coefficients. Compared to a traditional homogenous silicone liner for two unique limb loading scenarios, the prosthetist prescribed inlay and the optimized material inlay can achieve equal or greater pressure gradient reduction capabilities. These preliminary results show the potential feasibility of implementing this metamaterial as a method of personalized medicine for transtibial amputees by creating a customizable interface solution to meet the unique performance needs of an individual patient.
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Affiliation(s)
- Nathan Brown
- Department of Mechanical Engineering, Clemson University, 218 South Palmetto Building, Clemson, SC 29631
| | - Meredith K. Owen
- Department of Bioengineering, Clemson University, 118 Engineering Service Drive, Clemson, SC 29634
| | - Anthony Garland
- Center for Integrated Nanotechnologies, Sandia National Laboratories, 1515 Eubank Building SE, Albuquerque, NM 87123
| | - John D. DesJardins
- Department of Bioengineering, Clemson University, 118 Engineering Service Drive, Clemson, SC 29634
| | - Georges M. Fadel
- Department of Mechanical Engineering, Clemson University, 218 South Palmetto Building, Clemson, SC 29631
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Steer JW, Worsley PR, Browne M, Dickinson A. Key considerations for finite element modelling of the residuum-prosthetic socket interface. Prosthet Orthot Int 2021; 45:138-146. [PMID: 33176573 DOI: 10.1177/0309364620967781] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 09/22/2020] [Indexed: 02/03/2023]
Abstract
BACKGROUND Finite element modelling has long been proposed to support prosthetic socket design. However, there is minimal detail in the literature to inform practice in developing and interpreting these complex, highly nonlinear models. OBJECTIVES To identify best practice recommendations for finite element modelling of lower limb prosthetics, considering key modelling approaches and inputs. STUDY DESIGN Computational modelling. METHODS This study developed a parametric finite element model using magnetic resonance imaging data from a person with transtibial amputation. Comparative analyses were performed considering socket loading methods, socket-residuum interface parameters and soft tissue material models from the literature, to quantify their effect on the residuum's biomechanical response to a range of parameterised socket designs. RESULTS These variables had a marked impact on the finite element model's predictions for limb-socket interface pressure and soft tissue shear distribution. CONCLUSIONS All modelling decisions should be justified biomechanically and clinically. In order to represent the prosthetic loading scenario in silico, researchers should (1) consider the effects of donning and interface friction to capture the generated soft tissue shear stresses, (2) use representative stiffness hyperelastic material models for soft tissues when using strain to predict injury and (3) interrogate models comparatively, against a clinically-used control.
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Affiliation(s)
- Joshua W Steer
- Bioengineering Science Research Group, School of Engineering, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK
| | - Peter R Worsley
- Clinical Academic Facility, School of Health Sciences, Faculty of Environment and Life Sciences, University of Southampton, Southampton, UK
| | - Martin Browne
- Bioengineering Science Research Group, School of Engineering, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK
| | - Alex Dickinson
- Bioengineering Science Research Group, School of Engineering, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK
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Awasthi A, Gautam U, Bhaskar S, Roy S. Biomechanical modelling and computer aided simulation of deep brain retraction in neurosurgery. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2020; 197:105688. [PMID: 32861182 DOI: 10.1016/j.cmpb.2020.105688] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Accepted: 07/29/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND AND OBJECTIVES Surgical simulators are widely used to promote faster and safer surgical training. They not only provide a platform for enhancing surgical skills but also minimize risks to the patient's safety, operation theatre usage, and financial expenditure. Retracting the soft brain tissue is an unavoidable procedure during any surgery to access the lesioned tissue deep within the brain. Excessive retraction often results in damaging the brain tissue, thus requiring advanced skills and prior training using virtual platforms. Such surgical simulation platforms require an anatomically correct computational model that can accurately predict the brain deformation in real-time. METHODS In this study, we present a 3D finite element brain model reconstructed from MRI dataset. The model incorporates precisely the anatomy and geometrical features of the canine brain. The brain model has been used to formulate and solve a quasi-static boundary value problem for brain deformation during brain retraction. The visco-hyperelastic framework within the theory of non-linear elasticity has been used to set up the boundary value problem. Consequently, the derived non-linear field equations have been solved using finite element solver ABAQUS. RESULTS The retraction simulations have been performed for two scenarios: retraction pressure in the brain and forces required to perform the surgery. The brain was retracted by 5 mm and retained at that position for 30 minutes, during which the retraction pressure attenuates to 36% of its peak value. Both the model predictions as well as experimental observations on canine brain indicate that brain retraction up to 30 minutes did not cause any significant risk of induced damage. Also, the peak retraction pressure level indicates that intermittent retraction is a safer procedure as compared to the continuous retraction, for the same extent of retraction. CONCLUSIONS The results of the present study indicate the potential of a visco-hyperelastic framework for simulating deep brain retraction effectively. The simulations were able to capture the dominant characteristics of brain tissue undergoing retraction. The developed platform could serve as a basis for the development of a detailed model in the future that can eventually be used for effective preoperative planning and training purposes.
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Affiliation(s)
- Abhilash Awasthi
- Department of Applied Mechanics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Umesh Gautam
- Department of Applied Mechanics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Suryanarayanan Bhaskar
- Department of Neurosurgery, All India Institute of Medical Science Jodhpur, Rajasthan 342037, India
| | - Sitikantha Roy
- Department of Applied Mechanics, Indian Institute of Technology Delhi, New Delhi 110016, India.
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Analysis of the Relative Motion Between the Socket and Residual Limb in Transtibial Amputees While Wearing a Transverse Rotation Adapter. J Appl Biomech 2020; 37:21-29. [PMID: 33152690 DOI: 10.1123/jab.2019-0362] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 07/10/2020] [Accepted: 08/14/2020] [Indexed: 11/18/2022]
Abstract
The coupling between the residual limb and the lower-limb prosthesis is not rigid. As a result, external loading produces movement between the prosthesis and residual limb that can lead to undesirable soft-tissue shear stresses. As these stresses are difficult to measure, limb loading is commonly used as a surrogate. However, the relationship between limb loading and the displacements responsible for those stresses remains unknown. To better understand the limb motion within the socket, an inverse kinematic analysis was performed to estimate the motion between the socket and tibia for 10 individuals with a transtibial amputation performing walking and turning activities at 3 different speeds. The authors estimated the rotational stiffness of the limb-socket body to quantify the limb properties when coupled with the socket and highlight how this approach could help inform prosthetic prescriptions. Results showed that peak transverse displacement had a significant, linear relationship with peak transverse loading. Stiffness of the limb-socket body varied significantly between individuals, activities (walking and turning), and speeds. These results suggest that transverse limb loading can serve as a surrogate for residual-limb shear stress and that the setup of a prosthesis could be individually tailored using standard motion capture and inverse kinematic analyses.
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12
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Steer JW, Worsley PR, Browne M, Dickinson AS. Predictive prosthetic socket design: part 1-population-based evaluation of transtibial prosthetic sockets by FEA-driven surrogate modelling. Biomech Model Mechanobiol 2020; 19:1331-1346. [PMID: 31256276 PMCID: PMC7423807 DOI: 10.1007/s10237-019-01195-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 06/23/2019] [Indexed: 11/26/2022]
Abstract
It has been proposed that finite element analysis can complement clinical decision making for the appropriate design and manufacture of prosthetic sockets for amputees. However, clinical translation has not been achieved, in part due to lengthy solver times and the complexity involved in model development. In this study, a parametric model was created, informed by variation in (i) population-driven residuum shape morphology, (ii) soft tissue compliance and (iii) prosthetic socket design. A Kriging surrogate model was fitted to the response of the analyses across the design space enabling prediction for new residual limb morphologies and socket designs. It was predicted that morphological variability and prosthetic socket design had a substantial effect on socket-limb interfacial pressure and shear conditions as well as sub-dermal soft tissue strains. These relationships were investigated with a higher resolution of anatomical, surgical and design variability than previously reported, with a reduction in computational expense of six orders of magnitude. This enabled real-time predictions (1.6 ms) with error vs the analytical solutions of < 4 kPa in pressure at residuum tip, and < 3% in soft tissue strain. As such, this framework represents a substantial step towards implementation of finite element analysis in the prosthetics clinic.
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Affiliation(s)
- J. W. Steer
- Bioengineering Science Research Group, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK
| | - P. R. Worsley
- Clinical Academic Facility, Faculty of Health Sciences, University of Southampton, Southampton, UK
| | - M. Browne
- Bioengineering Science Research Group, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK
| | - A. S. Dickinson
- Bioengineering Science Research Group, Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK
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13
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Meng Z, Wong DWC, Zhang M, Leung AKL. Analysis of compression/release stabilized transfemoral prosthetic socket by finite element modelling method. Med Eng Phys 2020; 83:123-129. [PMID: 32527518 DOI: 10.1016/j.medengphy.2020.05.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 05/09/2020] [Accepted: 05/13/2020] [Indexed: 11/26/2022]
Abstract
The aim of this study was to investigate the residual limb stress of a transfemoral amputee's Compression/Release Stabilized (CRS) socket by finite elemental modelling. The model was constructed from magnetic resonance images of the left residual limb of a 48-year-old male transfemoral amputee. Two conditions were simulated. In the donning condition, the prosthetic socket under the residual limb moved proximally until it reached the required donned position. The weight-bearing condition was subsequently simulated by applying body weight (800N) at the femoral head while keeping the distal end of the socket fixed. The maximum contact pressure was concentrated at the proximal anterior-medial regions of the residual limb surfaces in both conditions. In the donning condition, the maximum von Mises stress and the maximum contact pressure were 277.7 kPa and 254 kPa respectively. The respective values were 191.9 kPa and 218.5 kPa when body weight was applied. The stress and contact pressure did not exceed the suggested threshold value of pain. Our findings provide important biomechanical information on the CRS socket that may help future design optimization.
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Affiliation(s)
- Zhaojian Meng
- Rehabilitation Research Institute, Guangdong Provincial Work Injury Rehabilitation Center, Guangzhou, China; Department of Biomedical Engineering, Faculty of Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Duo Wai-Chi Wong
- Department of Biomedical Engineering, Faculty of Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Ming Zhang
- Department of Biomedical Engineering, Faculty of Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Aaron Kam-Lun Leung
- Department of Biomedical Engineering, Faculty of Engineering, The Hong Kong Polytechnic University, Hong Kong, China.
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14
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Henao SC, Orozco C, Ramírez J. Influence of Gait Cycle Loads on Stress Distribution at The Residual Limb/Socket Interface of Transfemoral Amputees: A Finite Element Analysis. Sci Rep 2020; 10:4985. [PMID: 32193432 PMCID: PMC7081319 DOI: 10.1038/s41598-020-61915-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 03/03/2020] [Indexed: 01/30/2023] Open
Abstract
A Finite Element Analysis (FEA) was performed to evaluate the interaction between residual limb and socket when considering the dynamic loads of the gait cycle. Fourteen transfemoral amputees participated in this study, where their residual limbs (i.e., soft tissues and bone), and their sockets were reconstructed. The socket and the femur were defined as elastic materials, while the bulk soft tissues were defined as a hyperelastic material. Each model included the donning, standing, and gait cycle phase, with load and boundary conditions applied accordingly. The influence of adding the dynamic loads related to the gait cycle were compared against the modelling of the static load equivalent to the standing position resulting in changes of 23% ± 19% in the maximum values and in an increase in the size of the regions where they were located. Additionally, the possible correspondence between comfort and the location of peak loadbearing at the residual-limb/socket interface was explored. Consequently, the comfort perceived by the patient could be estimated based on the locations of the maximum stresses (i.e., if they coincide with the pressure tolerant or sensitive regions of the residual limb).
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Affiliation(s)
- Sofía C Henao
- Department of Mechanical Engineering, Universidad Nacional de Colombia, Medellin, Colombia.
| | - Camila Orozco
- Department of Mechanical Engineering, Universidad Nacional de Colombia, Medellin, Colombia
| | - Juan Ramírez
- Department of Mechanical Engineering, Universidad Nacional de Colombia, Medellin, Colombia.
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Mbithi FM, Chipperfield AJ, Steer JW, Dickinson AS. Predictive Control for an Active Prosthetic Socket informed by FEA-based Tissue Damage Risk Estimation. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2019:2073-2076. [PMID: 31946309 DOI: 10.1109/embc.2019.8857155] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
This paper presents an architecture for generalized predictive control for an active prosthetic socket system, based on a cost function performance index measure for minimization of residual limb tissue injury. Finite element analysis of a transtibial residuum model donned with a total surface bearing socket was used to provide controller training data and biomechanical rationale for deep tissue injury risk assessment, by estimating the internal deformation state of the soft tissues and the residuum-socket interface loading under a range of prosthetic loading instances. The results demonstrate the concept of this approach for interface actuation modelled as translational spring and damper systems.
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Thomson S, Lu W, Zreiqat H, Li JJ, Tetsworth K, Al Muderis M. Proximal Bone Remodeling in Lower Limb Amputees Reconstructed With an Osseointegrated Prosthesis. J Orthop Res 2019; 37:2524-2530. [PMID: 31424108 DOI: 10.1002/jor.24445] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 08/02/2019] [Indexed: 02/04/2023]
Abstract
Mobility outcomes and changes in bone mineral density (BMD) of the spine and femoral necks in response to unilateral osseointegrated implants was investigated over a 3-year period. A total of 48 unilateral amputees who received an osseointegrated implant, comprising 33 trans-femoral amputees (TFA) and 15 trans-tibial amputees (TTA), underwent dual-energy X-ray absorptiometry (DXA) scans of the lumbar spine (L2-L4) and femoral necks at baseline, 1-, and 3-years follow-ups. Mobility outcomes, including the Six-Minute-Walk Test (6MWT) and Timed-Up-and-Go (TUG), were measured before surgery, at 1 year, and more than 2 years following the osseointegration procedure. We observed a significant increase (p < 0.05) in Z-score values in the femoral neck of the amputated side in TFA patients without a femoral neck lag screw at the 1- and 3-year follow-ups, as well as in TFA patients with a lag screw present at 3-year follow-up. The BMD at 1-year follow-up was found to be positively correlated with pre-surgery 6MWT values in patients who were mobile using a traditional socket prosthesis before receiving an osseointegrated implant. These results suggest that osseointegrated implants induce a physiological response in the femoral neck of recipients and appear to be evidence of restored biomechanical loading in the proximal femur. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2524-2530, 2019.
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Affiliation(s)
- Seamus Thomson
- Biomaterials and Tissue Engineering Research Unit, School of AMME, The University of Sydney, Sydney, New South Wales, 2006, Australia
| | - William Lu
- Biomaterials and Tissue Engineering Research Unit, School of AMME, The University of Sydney, Sydney, New South Wales, 2006, Australia
| | - Hala Zreiqat
- Biomaterials and Tissue Engineering Research Unit, School of AMME, The University of Sydney, Sydney, New South Wales, 2006, Australia
| | - Jiao Jiao Li
- Biomaterials and Tissue Engineering Research Unit, School of AMME, The University of Sydney, Sydney, New South Wales, 2006, Australia
| | - Kevin Tetsworth
- Royal Brisbane and Women's Hospital, Herston, Queensland, 4029, Australia
| | - Munjed Al Muderis
- The Australian School of Advanced Medicine, Macquarie University, North Ryde, New South Wales, 2109, Australia.,School of Medicine, The University of Notre Dame, Auburn, New South Wales, 2144, Australia.,Norwest Private Hospital, Bella Vista, New South Wales, 2153, Australia
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Cagle JC, Reinhall PG, Allyn KJ, McLean J, Hinrichs P, Hafner BJ, Sanders JE. A finite element model to assess transtibial prosthetic sockets with elastomeric liners. Med Biol Eng Comput 2018; 56:1227-1240. [PMID: 29235055 PMCID: PMC5999538 DOI: 10.1007/s11517-017-1758-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2017] [Accepted: 11/20/2017] [Indexed: 11/24/2022]
Abstract
People with transtibial amputation often experience skin breakdown due to the pressures and shear stresses that occur at the limb-socket interface. The purpose of this research was to create a transtibial finite element model (FEM) of a contemporary prosthesis that included complete socket geometry, two frictional interactions (limb-liner and liner-socket), and an elastomeric liner. Magnetic resonance imaging scans from three people with characteristic transtibial limb shapes (i.e., short-conical, long-conical, and cylindrical) were acquired and used to develop the models. Each model was evaluated with two loading profiles to identify locations of focused stresses during stance phase. The models identified five locations on the participants' residual limbs where peak stresses matched locations of mechanically induced skin issues they experienced in the 9 months prior to being scanned. The peak contact pressure across all simulations was 98 kPa and the maximum resultant shear stress was 50 kPa, showing reasonable agreement with interface stress measurements reported in the literature. Future research could take advantage of the developed FEM to assess the influence of changes in limb volume or liner material properties on interface stress distributions. Graphical abstract Residual limb finite element model. Left: model components. Right: interface pressures during stance phase.
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Affiliation(s)
- John C Cagle
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | - Per G Reinhall
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | - Kate J Allyn
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | - Jake McLean
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | - Paul Hinrichs
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | - Brian J Hafner
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | - Joan E Sanders
- Department of Bioengineering, University of Washington, Seattle, WA, USA.
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Dickinson A, Steer J, Worsley P. Finite element analysis of the amputated lower limb: A systematic review and recommendations. Med Eng Phys 2017; 43:1-18. [DOI: 10.1016/j.medengphy.2017.02.008] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 01/17/2017] [Accepted: 02/10/2017] [Indexed: 01/18/2023]
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Yan F, Jiang WT, Dong RQ, Wang QY, Fan YB, Zhang M. Blood Flow and Oxygen Transport in Descending Branch of Lateral Femoral Circumflex Arteries After Transfemoral Amputation: A Numerical Study. J Med Biol Eng 2017. [DOI: 10.1007/s40846-016-0202-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Ginestra PS, Ceretti E, Fiorentino A. Potential of modeling and simulations of bioengineered devices: Endoprostheses, prostheses and orthoses. Proc Inst Mech Eng H 2016; 230:607-38. [PMID: 27095509 DOI: 10.1177/0954411916643343] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 03/09/2016] [Indexed: 11/16/2022]
Abstract
Modeling and simulation of prosthetic devices are the new tools investigated for the production of total customized prostheses. Computational simulations are used to evaluate the geometrical and material designs of a device while assessing its mechanical behavior. Data acquisition through magnetic resonance imaging, computed tomography or laser scanning is the first step that gives information about the human anatomical structures; a file format has to be elaborated through computer-aided design software. Computer-aided design tools can be used to develop a device that respects the design requirements as, for instance, the human anatomy. Moreover, through finite element analysis software and the knowledge of loads and conditions the prostheses are supposed to face in vivo, it is possible to simulate, analyze and predict the mechanical behavior of the prosthesis and its effects on the surrounding tissues. Moreover, the simulations are useful to eventually improve the design (as geometry, materials, features) before the actual production of the device. This article presents an extensive analysis on the use of finite element modeling for the design, testing and development of prosthesis and orthosis devices.
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Affiliation(s)
- Paola Serena Ginestra
- Department of Mechanical and Industrial Engineering, University of Brescia, Brescia, Italy
| | - Elisabetta Ceretti
- Department of Mechanical and Industrial Engineering, University of Brescia, Brescia, Italy
| | - Antonio Fiorentino
- Department of Mechanical and Industrial Engineering, University of Brescia, Brescia, Italy
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Shen Y, Li X, Fu X, Wang W. A 3D finite element model to investigate prosthetic interface stresses of different posterior tibial slope. Knee Surg Sports Traumatol Arthrosc 2015; 23:3330-6. [PMID: 25073943 DOI: 10.1007/s00167-014-3144-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 06/12/2014] [Indexed: 11/29/2022]
Abstract
PURPOSE Posterior tibial slope that is created during proximal tibial resection in total knee arthroplasty has emerged as an important factor in the mechanics of the knee joint and the surgical outcome. But the ideal degree of posterior tibial slope for recovery of the knee joint function and preventions of complications remains controversial and should vary in different racial groups. The objective of this paper is to investigate the effects of posterior tibial slope on contact stresses in the tibial polyethylene component of total knee prostheses. METHODS Three-dimensional finite element analysis was used to calculate contact stresses in tibial polyethylene component of total knee prostheses subjected to a compressive load. The 3D finite element model of total knee prosthesis was constructed from the images produced by 3D scanning technology. Stresses in tibial polyethylene component were calculated with four different posterior tibial slopes (0°, 3°, 6° and 9°). RESULTS The 3D finite element model of total knee prosthesis we presented was well validated. We found that the stress distribution in the polythene as evaluated by the distributions of the von Mises stress, the maximum principle stress, the minimum principle stress and the Cpress were more uniform with 3° and 6° posterior tibial slopes than with 0° and 9° posterior tibial slopes. Moreover, the peaks of the above stresses and trends of changes with increasing degree of knee flexion were more ideal with 3° and 6° posterior slopes. CONCLUSIONS The results suggested that the tibial component inclination might be favourable to 7°-10° so far as the stress distribution is concerned. The range of the tibial component inclination also can decrease the wear of polyethylene. Chinese posterior tibial slope is bigger than in the West, and the current domestic use of prostheses is imported from the West, so their demands to tilt back bone cutting can lead to shorten the service life of prostheses; this experiment result is of important clinical significance, guiding orthopaedic surgeon after the best angle to cut bone.
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Affiliation(s)
- Yi Shen
- Department of Orthopaedic, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, 1630 DongFang Road, Shanghai, 200127, China
| | - Xiaomiao Li
- Department of Orthopaedic, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, 1630 DongFang Road, Shanghai, 200127, China.
| | - Xiaodong Fu
- Department of Orthopaedic, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, 1630 DongFang Road, Shanghai, 200127, China
| | - Weili Wang
- Department of Orthopaedic, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, 1630 DongFang Road, Shanghai, 200127, China
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DONG RUIQI, JIANG WENTAO, ZHANG MING, LEUNG AARON, WONG MS. REVIEW: HEMODYNAMIC STUDIES FOR LOWER LIMB AMPUTATION AND REHABILITATION. J MECH MED BIOL 2015. [DOI: 10.1142/s0219519415300057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
No matter what the reason and level of amputation are, amputees will face many complex postoperative problems and potential complications. From the perioperative stage to lengthy rehabilitation process, patients need comprehensive and cautious therapies to help them rebuild their physical and mental health. Although there is some scattered information, the achievements of hemodynamic study for lower limb amputation and rehabilitation have not been systematically classified and summarized. The purpose of this review is to introduce and discuss the hemodynamic issues in preoperative diagnosis, surgical techniques and postoperative problems in the past two decades. Whether from clinical or biomechanical perspective, the investigations of the former two stages have been relatively mature and gained some clear outcomes, even if some conclusions are conflicting and controversial. While in terms of the postoperative problems, such as the common pressure ulcers, DTI and muscle atrophy, there is a lack of vascular or blood flow state studies specifically for lower residual limb. Therefore, the future research focus of hemodynamics for lower limb amputation should probably be the detailed investigations on the relationships between various blood flow parameters and certain common complications. Although hemodynamic research has made some achievements at this stage, it is believed that more advanced and reliable techniques are pending for further explorations and developments.
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Affiliation(s)
- RUIQI DONG
- Laboratory of Biomechanical Engineering, Sichuan University, Chengdu 610065, P. R. China
| | - WENTAO JIANG
- Laboratory of Biomechanical Engineering, Sichuan University, Chengdu 610065, P. R. China
| | - MING ZHANG
- Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong 999077, P. R. China
| | - AARON LEUNG
- Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong 999077, P. R. China
| | - M. S. WONG
- Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong 999077, P. R. China
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Zhang L, Zhu M, Shen L, Zheng F. Finite element analysis of the contact interface between trans-femoral stump and prosthetic socket. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2013; 2013:1270-1273. [PMID: 24109926 DOI: 10.1109/embc.2013.6609739] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Transfemoral amputees need prosthetic devices after amputation surgery, and the interface pressure between the residual limb and prosthetic socket has a significant effect on an amputee's satisfaction and comfort. The purpose of this study was to build a nonlinear finite element model to investigate the interface pressure between the above-knee residual limb and its prosthetic socket. The model was three-dimensional (3D) with consideration of nonlinear boundary conditions. Contact analysis was used to simulate the friction conditions between skin and the socket. The normal stresses up to 80.57 kPa at the distal end of the soft tissue. The longitudinal and circumferential shear stress distributions at the limb-socket interface were also simulated. This study explores the influences of load transfer between trans-femoral residual limb and its prosthetic socket.
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Ramírez JF, Vélez JA. Incidence of the boundary condition between bone and soft tissue in a finite element model of a transfemoral amputee. Prosthet Orthot Int 2012; 36:405-14. [PMID: 22354886 DOI: 10.1177/0309364612436409] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND Many finite element investigations have been made in the field of lower limb prosthetics; however, friction between bone and soft tissues as a boundary condition has not been considered. OBJECTIVES To establish whether the change in the contact boundary condition between bone and soft tissues in a transfemoral amputee affects the stress-strain state on the residual limb. STUDY DESIGN Finite element analysis comparison. METHODS Finite element models of four transfemoral amputees were developed. In these models the socket, soft tissues and femur were included and two simulations were made for each model, in one of them the interaction between bone and soft tissues was defined as tied (there is no relative displacement between surfaces) and in the other it was defined as a friction boundary condition. RESULTS The von Mises stress and strain peaks are higher when the friction definition is used than for tied contact definition. The distribution pattern of stresses and strains also change when the contact definition varies from tied to friction. CONCLUSIONS It was concluded that the friction between bone and soft tissues have a significant impact on the results of finite element models of lower limb prosthetic systems, and therefore in its predictive capabilities. Clinical relevance Understanding the bone-soft tissue interaction can lead to more realistic and accurate finite element models used to predict the stress-strain state in the residual limb of prosthetic users and therefore predict the occurrence of deep tissue injuries.
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Yeung LF, Leung AKL, Zhang M, Lee WCC. Effects of long-distance walking on socket-limb interface pressure, tactile sensitivity and subjective perceptions of trans-tibial amputees. Disabil Rehabil 2012; 35:888-93. [PMID: 22992201 DOI: 10.3109/09638288.2012.712197] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE Many trans-tibial amputees 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. METHOD Five male unilateral trans-tibial amputees 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. RESULTS 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. CONCLUSIONS 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. IMPLICATIONS FOR REHABILITATION • After long-distance walking (LDW) of the trans-tibal amputee 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.
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Affiliation(s)
- L F Yeung
- Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
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Safari MR, Rowe P, Buis A. Accuracy verification of magnetic resonance imaging (MRI) technology for lower-limb prosthetic research: utilising animal soft tissue specimen and common socket casting materials. ScientificWorldJournal 2012; 2012:156186. [PMID: 22619599 PMCID: PMC3349102 DOI: 10.1100/2012/156186] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 12/12/2011] [Indexed: 11/17/2022] Open
Abstract
Lower limb prosthetic socket shape and volume consistency can be quantified using MRI technology. Additionally, MRI images of the residual limb could be used as an input data for CAD-CAM technology and finite element studies. However, the accuracy of MRI when socket casting materials are used has to be defined. A number of six, 46 mm thick, cross-sections of an animal leg were used. Three specimens were wrapped with Plaster of Paris (POP) and the other three with commercially available silicone interface liner. Data was obtained by utilising MRI technology and then the segmented images compared to corresponding calliper measurement, photographic imaging, and water suspension techniques. The MRI measurement results were strongly correlated with actual diameter, surface area, and volume measurements. The results show that the selected scanning parameters and the semiautomatic segmentation method are adequate enough, considering the limit of clinical meaningful shape and volume fluctuation, for residual limb volume and the cross-sectional surface area measurements.
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Affiliation(s)
- Mohammad Reza Safari
- Department of Orthotics and Prosthetics, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
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Finite element analysis for the evaluation of the structural behaviour, of a prosthesis for trans-tibial amputees. Med Eng Phys 2012; 34:38-45. [DOI: 10.1016/j.medengphy.2011.06.014] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Revised: 06/21/2011] [Accepted: 06/22/2011] [Indexed: 11/22/2022]
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Ramírez JF, Isaza JA, Mariaka I, Vélez JA. Analysis of bone demineralization due to the use of exoprosthesis by comparing Young's modulus of the femur in unilateral transfemoral amputees. Prosthet Orthot Int 2011; 35:459-66. [PMID: 22005351 DOI: 10.1177/0309364611420478] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND There is a relation between Hounsfield units obtained from computed tomography (CT) scans and bone density. The density of the bones can be used to establish its mechanical properties and therefore to assess the bone mechanical condition using CT images. OBJECTIVES To identify the effect of the transfemoral amputation and the use of external lower limb prosthesis in the bone properties, by comparing Young's modulus. STUDY DESIGN Young's modulus comparison. METHODS Comparison of bone density between the healthy femur and the amputated bone of 20 unilateral transfemoral amputees was done by generating three histograms of the Hounsfield units at different parts of the femur. The histograms were created based on images obtained by CT and the Hounsfield units were translated to Young's modulus to establish the comparison. RESULTS The results show a significant difference (p-value <0.05) between the mean value of Young's modulus of healthy and amputated bone. CONCLUSIONS There is clearly a direct association between the use of external prosthesis and the bone demineralization due the stress shielding phenomenon. The Young's modulus comparison using information from CT images can be a suitable tool to analyze the bone demineralization due to the use of exoprosthesis.
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Mak AF, Yu Y, Kwan LP, Sun L, Tam EW. Deformation and reperfusion damages and their accumulation in subcutaneous tissues during loading and unloading: A theoretical modeling of deep tissue injuries. J Theor Biol 2011; 289:65-73. [DOI: 10.1016/j.jtbi.2011.08.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 07/31/2011] [Accepted: 08/19/2011] [Indexed: 12/20/2022]
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Lacroix D, Ramírez Patiño JF. Finite Element Analysis of Donning Procedure of a Prosthetic Transfemoral Socket. Ann Biomed Eng 2011; 39:2972-83. [DOI: 10.1007/s10439-011-0389-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Accepted: 08/24/2011] [Indexed: 10/17/2022]
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Colombo G, Filippi S, Rizzi C, Rotini F. A new design paradigm for the development of custom-fit soft sockets for lower limb prostheses. COMPUT IND 2010. [DOI: 10.1016/j.compind.2010.03.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Mak AF, Zhang M, Tam EW. Biomechanics of Pressure Ulcer in Body Tissues Interacting with External Forces during Locomotion. Annu Rev Biomed Eng 2010; 12:29-53. [PMID: 20415590 DOI: 10.1146/annurev-bioeng-070909-105223] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Forces acting on the body via various external surfaces during locomotion are needed to support the body under gravity, control posture, and overcome inertia. Examples include the forces acting on the body via the seating surfaces during wheelchair propulsion, the forces acting on the plantar foot tissues via the insole during gait, and the forces acting on the residual-limb tissues via the prosthetic socket during various movement activities. Excessive exposure to unwarranted stresses at the body-support interfaces could lead to tissue breakdowns commonly known as pressure ulcers, often presented as deep-tissue injuries around bony prominences or as surface damage on the skin. In this article, we review the literature that describes how the involved tissues respond to epidermal loading, taking into account both experimental and computational findings from in vivo and in vitro studies. In particular, we discuss related literature about internal tissue deformation and stresses, microcirculatory responses, and histological, cellular, and molecular observations.
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Affiliation(s)
- Arthur F.T. Mak
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
| | | | - Eric W.C. Tam
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
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Facoetti G, Gabbiadini S, Colombo G, Rizzi C. Knowledge-based System for Guided Modeling of Sockets for Lower Limb Prostheses. ACTA ACUST UNITED AC 2010. [DOI: 10.3722/cadaps.2010.723-737] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Wolf SI, Alimusaj M, Fradet L, Siegel J, Braatz F. Pressure characteristics at the stump/socket interface in transtibial amputees using an adaptive prosthetic foot. Clin Biomech (Bristol, Avon) 2009; 24:860-5. [PMID: 19744755 DOI: 10.1016/j.clinbiomech.2009.08.007] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Revised: 08/03/2009] [Accepted: 08/10/2009] [Indexed: 02/07/2023]
Abstract
BACKGROUND The technological advances that have been made in developing highly functional prostheses are promising for very active patients but we do not yet know whether they cause an increase in biomechanical load along with possibly negative consequences for pressure conditions in the socket. Therefore, this study monitored the socket pressure at specific locations of the stump when using a microprocessor-controlled adaptive prosthetic ankle under different walking conditions. METHODS Twelve unilateral transtibial amputees between 43 and 59 years of age were provided with the Proprio-Foot (Ossur) and underwent an instrumented 3D gait analysis in level, stair, and incline walking, including synchronous data capturing of socket pressure. Peak pressures and pressure time integrals (PTI) at three different locations were compared for five walking conditions with and without using the device's ankle adaptation mode. FINDINGS Highest peak pressures of 2.4 k Pa/kg were found for incline ascent at the calf muscle as compared to 2.1 k Pa/kg in level walking with large inter-individual variance. In stair ascent a strong correlation was found between maximum knee moment and socket pressure. The most significant pressure changes relative to level walking were seen in ramp descent anteriorly towards the stump end, with PTI values being almost twice as high as those in level walking. Adapting the angle of the prosthesis on stairs and ramps modified the pressure data such that they were closer to those in level walking. INTERPRETATION Pressure at the stump depends on the knee moments involved in each walking condition. Adapting the prosthetic ankle angle is a valuable means of modifying joint kinetics and thereby the pressure distribution at the stump. However, large inter-individual differences in local pressures underline the importance of individual socket fitting.
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Affiliation(s)
- Sebastian I Wolf
- Department of Orthopaedic Surgery, University of Heidelberg, Germany.
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Portnoy S, Yizhar Z, Shabshin N, Itzchak Y, Kristal A, Dotan-Marom Y, Siev-Ner I, Gefen A. Internal mechanical conditions in the soft tissues of a residual limb of a trans-tibial amputee. J Biomech 2008; 41:1897-909. [PMID: 18495134 DOI: 10.1016/j.jbiomech.2008.03.035] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2007] [Revised: 03/30/2008] [Accepted: 03/31/2008] [Indexed: 10/22/2022]
Abstract
Most trans-tibial amputation (TTA) patients use a prosthesis to retain upright mobility capabilities. Unfortunately, interaction between the residual limb and the prosthetic socket causes elevated internal strains and stresses in the muscle and fat tissues in the residual limb, which may lead to deep tissue injury (DTI) and other complications. Presently, there is paucity of information on the mechanical conditions in the TTA residual limb during load-bearing. Accordingly, our aim was to characterize the mechanical conditions in the muscle flap of the residual limb of a TTA patient after donning the prosthetic socket and during load-bearing. Knowledge of internal mechanical conditions in the muscle flap can be used to identify the risk for DTI and improve the fitting of the prosthesis. We used a patient-specific modelling approach which involved an MRI scan, interface pressure measurements between the residual limb and the socket of the prosthesis and three-dimensional non-linear large-deformation finite-element (FE) modelling to quantify internal soft tissue strains and stresses in a female TTA patient during static load-bearing. Movement of the truncated tibia and fibula during load-bearing was measured by means of MRI and used as displacement boundary conditions for the FE model. Subsequently, we calculated the internal strains, strain energy density (SED) and stresses in the muscle flap under the truncated bones. Internal strains under the tibia peaked at 85%, 129% and 106% for compression, tension and shear strains, respectively. Internal strains under the fibula peaked at substantially lower values, that is, 19%, 22% and 19% for compression, tension and shear strains, respectively. Strain energy density peaked at the tibial end (104kJ/m(3)). The von Mises stresses peaked at 215kPa around the distal end of the tibia. Stresses under the fibula were at least one order of magnitude lower than the stresses under the tibia. We surmise that our present patient-specific modelling method is an important tool in understanding the etiology of DTI in the residual limbs of TTA patients.
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Affiliation(s)
- S Portnoy
- Faculty of Engineering, Department of Biomedical Engineering, Tel Aviv University, Israel
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Lee WCC, Zhang M. Using computational simulation to aid in the prediction of socket fit: A preliminary study. Med Eng Phys 2007; 29:923-9. [PMID: 17056294 DOI: 10.1016/j.medengphy.2006.09.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2006] [Revised: 09/13/2006] [Accepted: 09/19/2006] [Indexed: 10/24/2022]
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 amputee 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 amputee 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.
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Affiliation(s)
- Winson C C Lee
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong, China
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Portnoy S, Yarnitzky G, Yizhar Z, Kristal A, Oppenheim U, Siev-Ner I, Gefen A. Real-time patient-specific finite element analysis of internal stresses in the soft tissues of a residual limb: a new tool for prosthetic fitting. Ann Biomed Eng 2006; 35:120-35. [PMID: 17120139 DOI: 10.1007/s10439-006-9208-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2006] [Accepted: 09/22/2006] [Indexed: 11/24/2022]
Abstract
Fitting of a prosthetic socket is a critical stage in the process of rehabilitation of a trans-tibial amputation (TTA) patient, since a misfit may cause pressure ulcers or a deep tissue injury (DTI: necrosis of the muscle flap under intact skin) in the residual limb. To date, prosthetic fitting typically depends on the subjective skills of the prosthetist, and is not supported by biomedical instrumentation that allows evaluation of the quality of fitting. Specifically, no technology is presently available to provide real-time continuous information on the internal distribution of mechanical stresses in the residual limb during fitting of the prosthesis, or while using it and this severely limits patient evaluations. In this study, a simplified yet clinically oriented patient-specific finite element (FE) model of the residual limb was developed for real-time stress analysis. For this purpose we employed a custom-made FE code that continuously calculates internal stresses in the residual limb, based on boundary conditions acquired in real-time from force sensors, located at the limb-prosthesis interface. Validation of the modeling system was accomplished by means of a synthetic phantom of the residual limb, which allowed simultaneous measurements of interface pressures and internal stresses. Human studies were conducted subsequently in five TTA patients. The dimensions of bones and soft tissues were obtained from X-rays of the residual limb of each patient. An indentation test was performed in order to obtain the effective elastic modulus of the soft tissues of the residual limb. Seven force sensors were placed between the residual limb and the prosthetic liner, and subjects walked on a treadmill during analysis. Generally, stresses under the shinbones were approximately threefold higher than stresses at the soft tissues behind the bones. Usage of a thigh corset decreased the stresses in the residual limb during gait by approximately 80%. Also, the stresses calculated during the trial of a subject who complained about pain and discomfort were the highest, confirming that his socket was not adequately fitted. We conclude that real-time patient-specific FE analysis of internal stresses in deep soft tissues of the residual limb in TTA patients is feasible. This method is promising for improving the fitting of prostheses in the clinical setting and for protecting the residual limb from pressure ulcers and DTI.
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Affiliation(s)
- S Portnoy
- Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel
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Faustini MC, Neptune RR, Crawford RH, Rogers WE, Bosker G. An Experimental and Theoretical Framework for Manufacturing Prosthetic Sockets for Transtibial Amputees. IEEE Trans Neural Syst Rehabil Eng 2006; 14:304-10. [PMID: 17009490 DOI: 10.1109/tnsre.2006.881570] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Selective laser sintering (SLS) is a powerful manufacturing technology that does not require part-specific tooling or significant human intervention and provides the ability to easily generate parts with complex geometric designs. The present work focuses on developing a manufacturing framework using this technology to produce subject-specific transtibial amputee prosthetic sockets made of Duraform PA, which is a nylon-based material. The framework includes establishing an overall socket design (using the patellar-tendon bearing approach), performing a structural analysis using the finite element method (FEM) to ensure structural reliability during patient use, and validating the results by comparing the model output with experimental data. The validation included quantifying the failure conditions for the socket through a series of bending moment and compression tests. In the case study performed, the FEM results were within 3% of the experimental failure loads for the socket and were considered satisfactory.
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Affiliation(s)
- Mario C Faustini
- Department of Mechanical Engineering, The University of Texas, Austin, TX 78712-0292, USA.
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Chen NZ, Lee WCC, Zhang M. A numerical approach to evaluate the fatigue life of monolimb. Med Eng Phys 2006; 28:290-6. [PMID: 16112888 DOI: 10.1016/j.medengphy.2005.07.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2004] [Revised: 04/20/2005] [Accepted: 07/04/2005] [Indexed: 12/01/2022]
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 amputee, 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.
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Affiliation(s)
- Nian-Zhong Chen
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong, China
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Faustini MC, Neptune RR, Crawford RH. The quasi-static response of compliant prosthetic sockets for transtibial amputees using finite element methods. Med Eng Phys 2006. [DOI: 10.1016/j.medengphy.2005.04.019 pmid:15941666] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Faustini MC, Neptune RR, Crawford RH. The quasi-static response of compliant prosthetic sockets for transtibial amputees using finite element methods. Med Eng Phys 2006; 28:114-21. [PMID: 15941666 DOI: 10.1016/j.medengphy.2005.04.019] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Revised: 03/03/2005] [Accepted: 04/19/2005] [Indexed: 10/25/2022]
Abstract
The finite element method (FEM) is a very powerful tool for analyzing the behavior of structures, especially when the geometry and mechanics are too complex to be modeled with analytical methods. This study focuses on the analysis of patellar tendon bearing prosthetic sockets with integrated compliant features designed to relieve contact pressure between the residual limb and socket. We developed a FEM model composed of a socket, liner and residual limb and analyzed it under quasi-static loading conditions derived from experimentally measured ground reaction forces. The geometry of the residual limb, liner and socket were acquired from computed tomography (CT) data of a transtibial amputee. Three different compliant designs were analyzed using FEM to assess the structural integrity of the sockets and their ability to relieve local pressure at the fibula head during normal walking. The compliant features consisted of thin-wall sections and two variations of spiral slots integrated within the socket wall. One version of the spiral slots produced the largest pressure relief, with an average reduction in local interface pressure during single-leg stance (20-80% of the stance phase) from 172 to 66.4 kPa or 65.8% compared to a baseline socket with no compliant features. These results suggest that the integration of local compliant features is an effective method to reduce local contact pressure and improve the functional performance of prosthetic sockets.
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Affiliation(s)
- Mario C Faustini
- Department of Mechanical Engineering, The University of Texas at Austin, 1 University Station C2200, Austin, TX 78712, USA
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Jia X, Zhang M, Li X, Lee WCC. A quasi-dynamic nonlinear finite element model to investigate prosthetic interface stresses during walking for trans-tibial amputees. Clin Biomech (Bristol, Avon) 2005; 20:630-5. [PMID: 15878224 DOI: 10.1016/j.clinbiomech.2005.03.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2004] [Revised: 03/02/2005] [Accepted: 03/04/2005] [Indexed: 02/07/2023]
Abstract
BACKGROUND To predict the interface pressure between residual limb and prosthetic socket for trans-tibial amputees during walking. METHODS 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. RESULTS 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. INTERPRETATION 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.
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Affiliation(s)
- Xiaohong Jia
- Division of Intelligent and Biomechanical System, State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China.
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Lee WC, Zhang M, Mak AF. Regional differences in pain threshold and tolerance of the transtibial residual limb: Including the effects of age and interface material. Arch Phys Med Rehabil 2005; 86:641-9. [PMID: 15827912 DOI: 10.1016/j.apmr.2004.08.005] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVES 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 amputees by the indentation method and to evaluate the interface pressure distribution and distortion of the skin surface on indentation by finite element (FE) analysis. DESIGN Crossover trial. SETTING Rehabilitation engineering center. PARTICIPANTS Eight transtibial amputees for indentation test and 1 for FE analysis. INTERVENTIONS 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. MAIN OUTCOME MEASURES Pain threshold and tolerance and interface pressure and distortion of soft tissues. RESULTS 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. CONCLUSIONS 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.
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Affiliation(s)
- Winson C Lee
- Jockey Club Rehabilitation Engineering Centre, Hong Kong Polytechnic University, Hong Kong, China
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