Piotr Laszczak

Development and validation of a 3D-printed interfacial stress sensor for prosthetic applications.

A novel capacitance-based sensor designed for monitoring mechanical stresses at the stump-socket interface of lower-limb amputees is described. It provides practical means of measuring pressure and shear stresses simultaneously. In particular, it comprises of a flexible frame (20 mm × 20 mm), with thickness of 4mm. By employing rapid prototyping technology in its fabrication, it offers a low-cost and versatile solution, with capability of adopting bespoke shapes of lower-limb residua. The sensor was first analysed using finite element analysis (FEA) and then evaluated using lab-based electromechanical tests. The results validate that the sensor is capable of monitoring both pressure and shear at stresses up to 350 kPa and 80 kPa, respectively. A post-signal processing model is developed to induce pressure and shear stresses, respectively. The effective separation of pressure and shear signals can be potentially advantageous for sensor calibration in clinical applications. The sensor also demonstrates high linearity (approx. 5-8%) and high pressure (approx. 1.3 kPa) and shear (approx. 0.6 kPa) stress resolution performance. Accordingly, the sensor offers the potential for exploitation as an assistive tool to both evaluate prosthetic socket fitting in clinical settings and alert amputees in home settings of excessive loading at the stump-socket interface, effectively preventing stump tissue breakdown at an early stage.

Microprocessor knees with ‘standing support’ and articulating, hydraulic ankles improve balance control and inter-limb loading during quiet standing

Introduction Trans-femoral amputees are at risk of musculoskeletal problems that are in part caused by loading asymmetry during activities, such as prolonged standing, particularly on uneven or sloped ground. Methods Four prosthetic conditions were tested; microprocessor knee ‘standing support’ mode activated (ON) and deactivated (OFF), combined with a rigidly attached foot (RA) and with an articulating, hydraulic ankle-foot (HA). Five trans-femoral amputees and five able-bodied controls were measured using a motion capture system and a force plate while standing, facing down a 5° slope. Ground reaction force distributions and centre-of-pressure root-mean-square (COP RMS) were calculated as outcome measures. Results Compensatory kinematic adjustments were observed for RA conditions but not for HA conditions. HA-OFF reduced ground reaction force degree-of-asymmetry for all five amputees, compared to RA-OFF. RA-ON reduced ground reaction force degree-of-asymmetry for four amputees, compared to RA-OFF. In terms of balance, the HA conditions reduced the mean inter-limb COP RMS by 24–25% compared to equivalent RA conditions, while ON conditions reduced it by 9–11%, compared to equivalent OFF conditions. Conclusions It is important to consider both prosthetic knee and ankle technologies when prescribing devices to trans-femoral amputees. The combination of hydraulic ankle and knee standing support technologies produced outcomes closest to normal biomechanics.

The influence of a microprocessor-controlled hydraulic ankle on the kinetic symmetry of trans-tibial amputees during ramp walking: A case series

Introduction Asymmetrical limb loading is believed to cause health problems for lower limb amputees and is exacerbated when walking on slopes. Hydraulically damped ankle-feet improve ground compliance on slopes compared to conventional prosthetic feet. Microprocessor-controlled hydraulic ankle-feet provide further adaptation by dynamically adjusting viscoelastic damping properties. Method Using a case series design, gait analysis was performed with four trans-tibial amputees. There were two walking conditions (ramp ascent and descent) and two prosthetic foot conditions (microprocessor-control on and off – MPF-on and MPF-off). Total support moment integral ( M I sup ) and degree-of-asymmetry were compared across foot conditions. Results During ramp descent, the transition of prosthetic ankle moment from dorsiflexion to plantarflexion occurred earlier in stance phase with MPF-on, slowing the angular velocity of the shank. During ramp ascent, the MPF-on dorsiflexion/plantarflexion moment transition occurred later, meaning less resistance to shank rotation in early stance and increasing walking speed by up to 6%. For both slope conditions, sound limb M I sup was universally decreased with MPF-on (4–13% descent, 3–11% ascent). Discussion Microprocessor-control of hydraulic ankle-feet reduced the total loading of the sound limb joints, for both walking conditions, for all participants. This may have beneficial consequences for long-term joint health and walking efficiency.

Development of a residuum/socket interface simulator for lower limb prosthetics:

Mechanical coupling at the interface between lower limb residua and prosthetic sockets plays an important role in assessing socket fitting and tissue health. However, most research lab–based lower limb prosthetic simulators to-date have implemented a rigid socket coupling. This study describes the fabrication and implementation of a lower limb residuum/socket interface simulator, designed to reproduce the forces and moments present during the key loading phases of amputee walking. An artificial residuum made with model bones encased in silicone was used, mimicking the compliant mechanical loading of a real residuum/socket interface. A 6-degree-of-freedom load cell measured the overall kinetics, having previously been incorporated into an amputee’s prosthesis to collect reference data. The developed simulator was compared to a setup where a rigid pylon replaced the artificial residuum. A maximum uniaxial load of 850 N was applied, comparable to the peak vertical ground reaction force component during amputee walking. Load cell outputs from both pylon and residuum setups were compared. During weight acceptance, when including the artificial residuum, compression decreased by 10%, while during push off, sagittal bending and anterior–posterior shear showed a 25% increase and 34% decrease, respectively. Such notable difference by including a compliant residuum further highlighted the need for such an interface simulator. Subsequently, the simulator was adjusted to produce key load cell outputs briefly aligning with those from amputee walking. Force sensing resistors were deployed at load bearing anatomic locations on the residuum/socket interface to measure pressures and were compared to those cited in the literature for similar locations. The development of such a novel simulator provides an objective adjunct, using commonly available mechanical test machines. It could potentially be used to provide further insight into socket design, fit and the complex load transfer mechanics at the residuum/socket interface, as well as to evaluate the structural performance of prostheses.

Dataset for Development of a residuum/socket interface simulator for lower limb prosthetics

Dataset supporting: Mcgrath, Michael et al. (2016) Development of a residuum/socket interface simulator for lower limb prosthetics. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine.Embargoed until 2020 for commercial reasons.

Dataset for An Interfacial Pressure and Shear Sensor System for Fingertip Contact Applications

Dataset supporting: Valero, Maria et al (2016) An interfacial pressure and shear sensor system for fingertip contact applications. Healthcare Technology Letters.

Assessing trans-femoral residuum/socket interface coupling using 3D motion capture – effect of terrains and walking speeds

The aim of this study was to develop a new means to assess residuum/socket interface couplings at different speeds and walking over different terrains using motion capture methods and a conventional 6 degrees of freedom (6DoF) marker model.This dataset accompanies the following paper: Tang, Jing, Mcgrath, Michael, Hale, Nicholas, Jiang, Liudi, Bader, Dan, Moser, David, Laszczak, Piotr, Bradbury, Richard and Zahhedi, Saeed (2016) Assessing trans-femoral residuum/socket interface coupling using 3D motion capture – effect of terrains and walking speeds. Gait & Posture

A lower-limb stump/socket interface simulator to aid assessment of clinical interventions

This is the dataset linked to: Tang, Jing et al (2015) Use of gait lab 3D motion capture for dynamic assessment of amputee socket interface biomechanics – a preliminary study. Prosthetics and Orthotics International, 39, (1), supplement 2-608, 257. doi:10.1177/0309364615591101).Background: Sierra Leone is a low income country in West Africa that has a history of conflict. Sierra Leone have signed and ratified the Convention of Rights of Persons with Disabilities. Aim: To evaluate persons with disability that use prosthetic and orthotic assistive devices access to human rights. The addressed areas were; right to health, right to a standard of living adequate for health, right to vote, right to marry and found a family, right to education, right to work and. A further aim was to compare groups of participants regarding gender, area of residence, income and type and level of device. Methods: Questionnaires were used to collect self-reported data from 139 prosthetic and orthotic users in Sierra Leone. Results: About half of the patient considered their overall physical health as good or very good. Thirty-seven percent of the participants said their mental health is bad or very bad. The majority said they did not have access to medical care and the most common reason given was that they could not afford doctors fee. The orthotic users reported they required medical care outside home more often than the prosthetic users. About half of the participants could not access afford medication when they needed it. About half of the participants had regularly access to safe drinking water and only 10% had the possibility to eat three times a day. The majority had a reasonably or adequate house to live. Half of the participants were married and 70% had children. Almost all reported that they could vote if they wanted. About half were working but often self-employed with small business. Sixty percent could read and write. Discussion & Conclusion: There was still a need for significant progress in increased access to medical care and medication when needed for persons with lower limb physical disability in Sierra Leone. Increased access to food and clean water to facilitate an acceptable standard of living adequate for health were also necessary in order to strive towards implementing the rights to health for persons with disability.Elevated skin temperature at the body/device interface of lower-limb prostheses is one of the major factors that affect tissue health [1]. The heat dissipation in prosthetic sockets is greatly influenced by the thermal conductive properties of the hard socket and liner material employed. This leads to a hypothesis that if the thermal properties of the socket & liner materials are known then the in-socket skin temperature could be accurately predicted by measuring between the socket and interface liner, rather than at the more technically challenging skin interface.Book 7th Annual International Conference on Business, Law & Economics 4-7 May 2020, Athens, Greece Edited by Gregory T. Papanikos THE ATHENS INSTITUTE FOR EDUCATION AND RESEARCH

Assessment of alignment effects on stump/socket interface and socket reaction moment using a lower-limb prosthetic simulator

This is the dataset linked to: Tang, Jing et al (2015) Use of gait lab 3D motion capture for dynamic assessment of amputee socket interface biomechanics – a preliminary study. Prosthetics and Orthotics International, 39, (1), supplement 2-608, 257. doi:10.1177/0309364615591101).Background: Sierra Leone is a low income country in West Africa that has a history of conflict. Sierra Leone have signed and ratified the Convention of Rights of Persons with Disabilities. Aim: To evaluate persons with disability that use prosthetic and orthotic assistive devices access to human rights. The addressed areas were; right to health, right to a standard of living adequate for health, right to vote, right to marry and found a family, right to education, right to work and. A further aim was to compare groups of participants regarding gender, area of residence, income and type and level of device. Methods: Questionnaires were used to collect self-reported data from 139 prosthetic and orthotic users in Sierra Leone. Results: About half of the patient considered their overall physical health as good or very good. Thirty-seven percent of the participants said their mental health is bad or very bad. The majority said they did not have access to medical care and the most common reason given was that they could not afford doctors fee. The orthotic users reported they required medical care outside home more often than the prosthetic users. About half of the participants could not access afford medication when they needed it. About half of the participants had regularly access to safe drinking water and only 10% had the possibility to eat three times a day. The majority had a reasonably or adequate house to live. Half of the participants were married and 70% had children. Almost all reported that they could vote if they wanted. About half were working but often self-employed with small business. Sixty percent could read and write. Discussion & Conclusion: There was still a need for significant progress in increased access to medical care and medication when needed for persons with lower limb physical disability in Sierra Leone. Increased access to food and clean water to facilitate an acceptable standard of living adequate for health were also necessary in order to strive towards implementing the rights to health for persons with disability.Elevated skin temperature at the body/device interface of lower-limb prostheses is one of the major factors that affect tissue health [1]. The heat dissipation in prosthetic sockets is greatly influenced by the thermal conductive properties of the hard socket and liner material employed. This leads to a hypothesis that if the thermal properties of the socket & liner materials are known then the in-socket skin temperature could be accurately predicted by measuring between the socket and interface liner, rather than at the more technically challenging skin interface.Book 7th Annual International Conference on Business, Law & Economics 4-7 May 2020, Athens, Greece Edited by Gregory T. Papanikos THE ATHENS INSTITUTE FOR EDUCATION AND RESEARCH