The Use of Smartphone Photogrammetry to Digitise Transtibial Sockets: Optimisation of Method and Quantitative Evaluation of Suitability

The fit of a lower limb prosthetic socket is critical for user comfort and the quality of life of lower limb amputees. Sockets are conventionally produced using hand-crafted patient-based casting techniques. Modern digital techniques offer a host of advantages to the process and ultimately lead to improving the lives of amputees. However, commercially available scanning equipment required is often expensive and proprietary. Smartphone photogrammetry could offer a low cost alternative, but there is no widely accepted imaging technique for prosthetic socket digitisation. Therefore, this paper aims to determine an optimal imaging technique for whole socket photogrammetry and evaluate the resultant scan measurement accuracy. A 3D printed transtibial socket was produced to create digital and physical twins, as reference models. The printed socket was photographed from 360 positions and simplified genetic algorithms were used to design a series of experiments, whereby a collection of photos were processed using Autodesk ReCap. The most fit technique was used to assess accuracy. The accuracy of the socket wall volume, surface area and height were 61.63%, 99.61% and 99.90%, respectively, when compared to the digital reference model. The scanned model had a wall thickness ranging from 2.075 mm at the top to 7.758 mm towards the base of the socket, compared to a consistent thickness of 2.025 mm in the control model. The technique selected did not show sufficient accuracy for clinical application due to the degradation of accuracy nearer to the base of the socket interior. However, using an internal wall thickness estimation, scans may be of sufficient accuracy for clinical use; assuming a uniform wall thickness.

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Strength testing of low-cost 3D-printed transtibial prosthetic socket

Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine ◽

10.1177/09544119211060092 ◽

2021 ◽

pp. 095441192110600

Author(s):

Merel van der Stelt ◽

Luc Verhamme ◽

Cornelis H Slump ◽

Lars Brouwers ◽

Thomas JJ Maal

Keyword(s):

Tensile Properties ◽

Lower Limb ◽

Low Cost ◽

Test Method ◽

Structural Testing ◽

International Standard ◽

Prosthetic Socket ◽

Computer Aided ◽

3D Printed ◽

Lower Limb Prostheses

Measurement and production of traditional prosthetic sockets are time-consuming, labor-intensive, and highly dependent on the personnel involved. An alternative way to make prostheses is using computer-aided design (CAD) and computer-aided manufacturing (CAM). Fused Filament Fabrication (FFF) may be an alternative to make low-cost prosthetic sockets. This study investigates the tensile properties of potential printing materials suitable for FFF according to ISO527 (Standard Test Method for Tensile Properties of Plastics). To ensure that FFF-printed sockets are safe for patient usage, the structural integrity of the 3D-printed prosthesis will be investigated according to ISO10328 (International Standard Structural Testing of Lower Limb Prostheses). Tough PLA was the most suitable print material according to ISO 527 testing. The Tough PLA printed socket completed 2.27 million cycles and a static test target value of 4025 N. Future research remains necessary to continue testing new potential materials, improve print settings, and improve the socket design for the production of FFF-printed transtibial prosthetic sockets. FFF using Tough PLA can be used to create transtibial prostheses that almost comply with the International Standard for Structural Testing of Lower Limb Prostheses.

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Accuracy Verification of an Anatomical Model Manufactured Using Low-Cost Additive Production

Applied Sciences ◽

10.3390/app11020594 ◽

2021 ◽

Vol 11 (2) ◽

pp. 594

Author(s):

Teodor Tóth ◽

Patrik Varga ◽

Branko Štefanovič ◽

Lucia Bednarčíková ◽

Marek Schnitzer ◽

...

Keyword(s):

Surface Coverage ◽

Reference Model ◽

Low Cost ◽

Cervical Vertebra ◽

3D Printer ◽

3D Scanner ◽

Entire Surface ◽

Additive Production ◽

The Third ◽

And Training

The paper deals with the separation of the third cervical vertebra using the software VGStudio MAX, Mimics, and inVesalius. During the separation, various parameters of the threshold were used to determine the effect. The comparison of models from Mimics and inVesalius to VGStudio MAX showed that the cumulative variance distribution for 95% surface coverage is less than 0.935 mm. When comparing medically oriented software, Mimics and inVesalius, the deviation was less than 0.356 mm. The model was made of polylactic acid (PLA) material on a low-cost 3D printer, Prusa i3 MK2.5 MMU1. The printed model was scanned by four scanners: Artec Eva, 3Shape D700, Steinbichler Comet L3D, and Creaform EXAscan. The outputs from the scanners were compared to the reference model (standard tessellation language (STL) model for 3D printing) as well as to the scanner with the best accuracy (3Shape). Compared to the publications below, the analysis of deviations was evaluated on the entire surface of the model and not on selected dimensions. The cumulative variance distribution for comparing the output from the 3D scanner with the reference model, as well as comparing the scanners, shows that the deviation for 95% of the surface coverage is at the level of 0.300 mm. Since the model of the vertebra is planned for education and training, the used software and technologies are suitable for use in the design and the production process.

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Simplified rat intubation using a new oropharyngeal intubation wedge

Journal of Applied Physiology ◽

10.1152/jappl.2000.89.5.1766 ◽

2000 ◽

Vol 89 (5) ◽

pp. 1766-1770 ◽

Cited By ~ 28

Author(s):

I-Ming Jou ◽

Ya-Ting Tsai ◽

Ching-Lin Tsai ◽

Ming-Ho Wu ◽

Han-Yu Chang ◽

...

Keyword(s):

Low Cost ◽

Vital Signs ◽

Upper Airway ◽

Postmortem Examination ◽

Normal Range ◽

Special Equipment ◽

Vocal Cords ◽

Oropharyngeal Cavity ◽

Series Of Experiments ◽

Proper Setting

Our new oropharyngeal intubation wedge made from a plastic 3-ml syringe has been used successfully for the expansion of the oropharyngeal cavity and visualization of vocal cords for endotracheal intubation in the rat. All the animals we used tolerated the intubation and ventilation procedures in a series of experiments. After the proper setting of the respirator, vital signs were maintained within normal range. The postmortem examination and measurements in the upper airway confirmed that the endotracheal tube was properly sited and also demonstrated the precise size of the device that should be used. The main advantages of this method include low cost, simplicity, and reliability. Furthermore, because no expensive, elaborate, difficult-to-operate, or hard-to-get special equipment is needed, this technique can be used in every laboratory.

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Comparison of bending stiffness of six different colours of copolymer polypropylene

Prosthetics and Orthotics International ◽

10.3109/03093649909071613 ◽

1999 ◽

Vol 23 (1) ◽

pp. 63-71 ◽

Cited By ~ 5

Author(s):

R. S. Ross ◽

R. J. Greig ◽

P. Convery

Keyword(s):

Electron Microscope ◽

Wall Thickness ◽

Modulus Of Elasticity ◽

Microscope Study ◽

Electron Microscope Study ◽

Bending Moment ◽

Bending Stiffness ◽

Ankle Foot Orthosis ◽

Uniform Wall ◽

Foot Orthosis

This paper compares the bending stiffness of 5 different colours of copolymer polypropylene (CCP) with that of natural copolymer polypropylene (NCP). Flesh coloured and natural sheets are supplied thicker than other pigmented sheet. The bending stiffness of a specimen may be defined as EI, i.e. the product of E, Young's modulus of elasticity and I, the 2nd moment of area. Strips of “as supplied” (AS) and “post-draped” (PD) specimen were clamped and subjected to bending to assess the effect of pigmentation on bending characteristics. The gradient of the graph of bending deflection δ versus bending moment enables EI to be estimated. The process of thermoforming polypropylene reduces EI, the bending stiffness. However, the manual draping and vacuum procedure introduces so many variables that it is difficult to quantify the effect of pigmentation. The E of a bent specimen may be estimated from the gradient of the graph of δI versus bending moment. In the case of AS sheet, the effect of pigmentation on E is inconclusive. PD specimens indicate a significant reduction in E due to thermoforming. This was verified by an electron-microscope study of AS and PD specimens. Draping an ankle-foot orthosis (AFO) results in a non-uniform wall thickness. The results of this study with respect to the effects of pigmentation on the bending stiffness of AFOs are inconclusive. More detailed studies require to be completed in order to confirm which factors are responsible for this non-uniformity in wall thickness and consequent variation in bending stiffness.

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The development and internal consistency of the comprehensive lower limb amputee socket survey in active lower limb amputees

Prosthetics and Orthotics International ◽

10.1177/0309364618791620 ◽

2018 ◽

Vol 43 (1) ◽

pp. 80-87 ◽

Cited By ~ 5

Author(s):

Robert Gailey ◽

Anat Kristal ◽

Jennifer Lucarevic ◽

Shane Harris ◽

Brooks Applegate ◽

...

Keyword(s):

Internal Consistency ◽

Lower Limb ◽

Self Report ◽

Cronbach’S Alpha ◽

Convenience Sample ◽

Cronbach's Alpha ◽

Prosthetic Socket ◽

Lower Limb Amputee ◽

Report Measure ◽

Lower Limb Amputees

Background: Prosthetic socket fit is an important element associated with successful ambulation and use of a prosthesis. Prosthetists and rehabilitation clinicians would benefit from an assessment tool that discriminates between and quantifies the multiple determinants that influence the lower limb amputee’s performance and satisfaction of a prosthetic socket. Objectives: To determine the internal consistency of the comprehensive lower limb amputee socket survey, a new self-report measure of prosthetic socket satisfaction that quantifies suspension, stability, comfort, and appearance. Study design: Cross-sectional sample of active amputees. Methods: Interviews were conducted with prosthetists, physical therapists, and lower limb amputees to identify clinical concerns and common activities influencing socket fit. An expert panel of five clinicians reviewed the items and constructed the original version of the comprehensive lower limb amputee socket survey which was then administered to a convenience sample of 47 active lower limb amputees. Item analysis and Cronbach’s alpha were used to determine the final version of the comprehensive lower limb amputee socket survey. Results: Following item raw score-to-total score correlation with Cronbach’s alpha for comprehensive lower limb amputee socket survey determinants, internal consistency improved when nine questions were eliminated. Conclusion: The comprehensive lower limb amputee socket survey is a self-report measure of prosthetic socket satisfaction with very good internal consistency. Clinical relevance When socket problems occur, the ability to determine the specific cause can reduce modification time, enhance socket fit, and promote patient satisfaction. A standardized multi-dimensional assessment measure of socket satisfaction enables prosthetists to quantify the multiple determinants of socket satisfaction, improve patient communication, and demonstrate the value of socket interventions.

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Evaluating the Effect of an Amputee’s Physical Parameters of Pressure on a Lower-Limb Prosthetic Socket Using a Fuzzy-Logic-Based Model

Applied Mechatronics and Mechanics ◽

10.1201/9781003019060-11 ◽

2020 ◽

pp. 167-189

Author(s):

Vimal Kumar Pathak ◽

Chitresh Nayak ◽

Deepak Rajendra Unune

Keyword(s):

Fuzzy Logic ◽

Lower Limb ◽

Physical Parameters ◽

Prosthetic Socket

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Developing a control framework for self-adjusting prosthetic sockets incorporating tissue injury risk estimation and Generalized Predictive Control

10.31224/osf.io/cd6pg ◽

2021 ◽

Author(s):

Florence M Mbithi ◽

Joshua Steer ◽

Andrew J Chipperfield ◽

Alexander Dickinson

Keyword(s):

Predictive Control ◽

Lower Limb ◽

Injury Risk ◽

Tissue Injury ◽

Risk Estimation ◽

Soft Tissue Injury ◽

Estimation Method ◽

Generalized Predictive Control ◽

Prosthetic Socket ◽

Interfacial Pressure

Purpose: To perform activities of daily living (ADL), people with lower limb amputation depend on the prosthetic socket for stability and proprioceptive feedback. Poorly fitting sockets can cause discomfort, pain, limb tissue injuries, limited device usage, and potential rejection. Semi-passively controlled adjustable socket technologies exist, but these depend upon the user’s perception to determine safe interfacial pressure levels. This paper presents a framework for automatic control of an adjustable transtibial prosthetic socket that enables active adaptation of residuum-socket interfacial loading through localized actuators, based on soft tissue injury risk estimation. Method: Using finite element analysis, local interfacial pressure vs. compressive tissue strain relationships were estimated for three anatomical actuator locations, for tissue injury risk assessment within a control structure. Generalized Predictive Control of multiple actuators was implemented to maintain interfacial pressure within estimated safe and functional limits. Results: Controller simulation predicted satisfactory dynamic performance in several scenarios, based on previous related studies. Actuation rates of 0.06 – 1.51kPa/s with 0.67% maximum overshoot, and 0.75 – 1.58kPa/s were estimated for continuous walking, and for a demonstrative loading sequence of ADL, respectively. Conclusion: The developed platform could be useful for extending recent efforts in adjustable lower limb prosthetic socket design, particularly for individuals with residuum sensory impairment.

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Optimization of Superplastic Forming Process of AA7075 Alloy for the Best Wall Thickness Distribution

Advances in Technology Innovation ◽

10.46604/aiti.2021.7835 ◽

2021 ◽

Vol 6 (4) ◽

pp. 251-261

Author(s):

Manh Tien Nguyen ◽

Truong An Nguyen ◽

Duc Hoan Tran ◽

Van Thao Le

Keyword(s):

Wall Thickness ◽

Deformation Temperature ◽

Numerical Optimization ◽

Thickness Distribution ◽

Superplastic Forming ◽

Forming Process ◽

Wall Thickness Distribution ◽

Surface Method ◽

Series Of Experiments ◽

The Relationship

This work aims to optimize the process parameters for improving the wall thickness distribution of the sheet superplastic forming process of AA7075 alloy. The considered factors include forming pressure p (MPa), deformation temperature T (°C), and forming time t (minutes), while the responses are the thinning degree of the wall thickness ε (%) and the relative height of the product h*. First, a series of experiments are conducted in conjunction with response surface method (RSM) to render the relationship between inputs and outputs. Subsequently, an analysis of variance (ANOVA) is conducted to verify the response significance and parameter effects. Finally, a numerical optimization algorithm is used to determine the best forming conditions. The results indicate that the thinning degree of 13.121% is achieved at the forming pressure of 0.7 MPa, the deformation temperature of 500°C, and the forming time of 31 minutes.

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Technical Note: Effect of varying the <i>λ</i> = 185 and 254 nm photon flux ratio on radical generation in oxidation flow reactors

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-13417-2020 ◽

2020 ◽

Vol 20 (21) ◽

pp. 13417-13424

Author(s):

Jake P. Rowe ◽

Andrew T. Lambe ◽

William H. Brune

Keyword(s):

Residence Time ◽

Low Cost ◽

Flux Ratio ◽

Technical Note ◽

Photon Flux ◽

Oh Radicals ◽

Flow Reactors ◽

Series Of Experiments ◽

Radical Generation ◽

Smog Chambers

Abstract. Oxidation flow reactors (OFRs) complement environmental smog chambers as a portable, low-cost technique for exposing atmospheric compounds to oxidants such as ozone (O3), nitrate (NO3) radicals, and hydroxyl (OH) radicals. OH is most commonly generated in OFRs via photolysis of externally added O3 at λ=254 nm (OFR254) or combined photolysis of O2 and H2O at λ=185 nm plus photolysis of O3 at λ=254 nm (OFR185) using low-pressure mercury (Hg) lamps. Whereas OFR254 radical generation is influenced by [O3], [H2O], and photon flux at λ=254 nm (I254), OFR185 radical generation is influenced by [O2], [H2O], I185, and I254. Because the ratio of photon fluxes, I185:I254, is OFR-specific, OFR185 performance varies between different systems even when constant [H2O] and I254 are maintained. Thus, calibrations and models developed for one OFR185 system may not be applicable to another. To investigate these issues, we conducted a series of experiments in which I185:I254 emitted by Hg lamps installed in an OFR was systematically varied by fusing multiple segments of lamp quartz together that either transmitted or blocked λ=185 nm radiation. Integrated OH exposure (OHexp) values achieved for each lamp type were obtained using the tracer decay method as a function of UV intensity, humidity, residence time, and external OH reactivity (OHRext). Following previous related studies, a photochemical box model was used to develop a generalized OHexp estimation equation as a function of [H2O], [O3], and OHRext that is applicable for I185:I254≈0.001 to 0.1.

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