Dr Matthew Oldfield

Background: Energy Storage and Return (ESAR) prosthetic feet provide improved walking when compared with previous designs. However, it may not mimic the unimpaired smooth and progressive movement of the foot on the floor (foot rollover). Objective: To characterize the temporal foot rollover of participants with unilateral transtibial amputation using an ESAR prosthetic foot. Study design: Cross-sectional. Methods: Plantar pressure data were collected from 11 participants with unilateral transtibial amputation using ESAR prostheses (2 females, mean age 37 ± 10 years, activity levels K2-K4) and 9 unimpaired participants (3 females, mean age 33 ± 10 years). The Initial Contact, Final Contact, and Total Contact times of 7 areas of the feet (unimpaired, intact, and prosthetic feet) were studied together with the duration of the Heel Rocker, Ankle Rocker, and Forefoot Rocker. Results were compared using a mixed analysis of the variance test. Results: Statistical analysis revealed an interaction (P < 0.05) between foot and areas. The contact times were different (P < 0.05) between unimpaired and prosthetic feet for most foot areas. Furthermore, the prosthetic foot showed the longest duration of Heel Rocker (21.1 ± 8.5% of stance phase vs. 17.7 ± 10.2% for the intact foot and 15.7 ± 8.8% for the unimpaired feet, P < 0.05) and the shortest duration of Ankle Rocker (43.8 ± 18.1% vs. 47.2 ± 16.9% for the intact foot and 50.0 ± 13.4% for the unimpaired feet, P < 0.05). Conclusions: Results suggest that the ESAR foot does not mimic the unimpaired foot rollover, especially in the contact pattern and the heel and ankle rockers. This might have an impact on efficiency and stability of gait.

Several kinematic-based algorithms have shown accuracy for gait event detection in unimpaired and pathological gait. However, their validation in subjects with lower limb amputation while walking on different terrains is still limited. The aim of this study was to evaluate the accuracy of three kinematic-based algorithms: Coordinate-Based Algorithm (CBA), Velocity-Based Algorithm (VBA) and High-Pass Filtered Algorithms (HPA) for detection of gait events in subjects with unilateral transtibial amputation walking on different terrains. Twelve subjects with unilateral transtibial amputation, using a hydraulic ankle prosthesis, walked at self-selected walking speed, on level ground and up and down a slope. Detection of Initial Contact (IC) and Foot Off (FO) by the three algorithms for intact and prosthetic limbs was compared with detection by force platforms using the True Error (TE) (time difference in detection). Mean TE found for over 100 events analysed per condition were smaller than 40 ms for both events in all conditions (approximately 6 % of stance phase). Significant interactions (p 

Subjects with unilateral transtibial amputation exhibit altered minimum toe clearance (MTC) depending on the ankle prosthesis used. It has been suggested that a limited prosthetic ankle angle could be the cause of the change. The aim of this study was to investigate the alterations in kinematics in the joints responsible for the changes in MTC when using an articulating hydraulic ankle (AHA) prosthesis compared to a nonarticulating ankle (NAA) prosthesis. Twelve participants with unilateral transtibial amputation walked at their self-selected speed on a 10 m pathway. They used both the same AHA and NAA prosthetic models and the prosthetic characteristics were unchanged except for the ankle mechanisms and, consequently, its mass. Data from MTC and hip, knee, and ankle angles in the sagittal, frontal, and transversal plane at the time of MTC were statistically analyzed with a paired sample t-test. The AHA prosthesis showed significantly higher MTC mean (AHA=24.7 ± 9.6 mm versus NAA=17.4 ± 5.2 mm, P

Objectives Introduce The ExtRA Capacity Test, a measure for assessing shoulder muscle performance. Assess its reliability, validity and present normative scores in a large sample of asymptomatic adults. Design Cross-sectional observational study with test–retest. Setting Community. Participants Volunteers (n = 344, age 20–90 years). Interventions The ExtRA Capacity Test involves two capacity tests completed to a 30 beats per minute metronome: maximal scapular plane lateral raises to 90° abduction with 2.5 kg of external load, and maximal external rotations in unsupported prone lying with the shoulder at 90° abduction. Reliability was assessed in 30 asymptomatic participants, tested by two raters over two sessions, one week apart, using Bland–Altman analysis to determine mean bias and 95 % limits of agreement (LoA) as measures of error. Criterion validity was evaluated in 20 participants using Pearson correlation to examine the relationship between ExtRA and isokinetic dynamometry measures. A normative dataset was also established from 344 asymptomatic individuals across a range of ages, physical activity levels, and both sexes. Results The intra-rater and inter-rater agreement for the ExtRA Capacity Test was assessed in a sample of 30 participants. The 95 % LoA for abduction and external rotation measurements ranged from 2.9 to 13.1 repetitions. In a sample of 20 participants, the abduction test showed good/moderate correlation with muscle strength measures but not with the external rotation test. Older age, female sex and not achieving the WHO activity guidelines have a negative impact on ExtRA performance. Conclusions Within the caveats discussed in this paper, ExtRA can be considered a reasonably reliable tool for assessing shoulder strength and control in a clinical setting. The normative database will help clinicians set rehabilitation or return-to-play targets based on sex, age, and physical activity level. Contributions of Paper This study introduces the ExtRA Capacity Test as a reliable tool for assessing shoulder muscle performance in both sporting and non-sporting populations. The test demonstrates clinically acceptable intra- and inter-rater reliability, with the abduction component showing a strong correlation with strength measures from Isokinetic Dynamometry. The normative database established in this study facilitates the evaluation of shoulder performance relative to reference values stratified by age, sex, and physical activity level. Given its high reliability, the ExtRA Capacity Test can be used to monitor performance changes over time, providing valuable insights

A multiple thermally assisted piercing process has been developed as a method of making equally spaced holes in thermoplastic composites. The consequences for the mechanical properties of the composite of introducing a limited set of inline holes into cross-ply laminates have been investigated. Open-hole tension and Iosipescu shear testing has been carried out on specimens containing drilled or pierced holes aligned with the direction of loading; microscopy and digital image correlation techniques have also been used to investigate local changes in fiber orientation and strain distributions under load. The strain fields for inline holes in drilled and pierced specimens under tensile loading can be understood in terms of local changes to the modulus as a consequence of the piercing or drilling process; in addition, some features of the strain fields can be predicted with the aid of a shear-lag model developed for modeling matrix cracking in cross-ply laminates. Although significant differences were found between the strain fields of the drilled and pierced specimens, no consistent improvement in strength was observed for the pierced composites compared to drilled composites for different holes spacings. Under shear loading, the pierced composites were found to have a significantly poorer response compared to drilled composites, which is related to the premature collapse of the holes in shear due to (a) localized fractures in regions of low fiber volume fraction and (b) intact fibers being pulled across the holes causing hole collapse.

The Arthritis patients and aging population has challenged society to develop safer, independent living environments. Falls, associated injuries, and delays in fall treatment are major causes of morbidity and death in older adults. Therefore, fall detection systems are fundamental to reducing fall risks and building safer environments. Designing fall detection systems is an emerging field of research. The development of the system relies on a sensing mechanism, processing unit, and communication to alert the emergency facilities. Each module is crucial in providing a cost-effective, accurate, reliable, and robust solution. Technological advancements in fall detection systems, particularly wearable and non-wearable devices, offer promising solutions. Wearable systems are prevalent due to their cost-effectiveness and ease of installation, but they canbe unreliable if not worn consistently. Non-wearable systems, including smart flooring, provide continuous monitoring but are expensive and complex to maintain. This article reviews the development and deployment of fall detection technologies, examining their practical limitations and emphasizing floor-based detection systems as a viable solution for fostering independent living among older adults.

This study harnesses advanced Bayesian optimisation techniques for the intricate design of structures, poised for application as compliant flooring unit cells, as shown to reduce fall injuries in older people[1]. Inspired by the foundational research detailed in studies[2][3], our exploration delves into a design space encompassing eight key variables, contributing to a broad spectrum of geometric variations. In constitutive modelling of unit cells, we adopt the Neo-Hookean model for its effectiveness in mirroring rubber-like materials' intrinsic properties. A key element of our approach involves acknowledging and addressing uncertainty, emanating from variations in material properties and geometric imperfections. The study rigorously explores the behaviour of these structures under 2D loading conditions , examining various ratios of compression and shear forces. Employing the Bayesian optimisation algorithm, the design iteratively progresses towards an optimal configuration, driven by a comprehensive set of objective functions, which are formulated to achieve an balance between structural stiffness, critical buckling load, and the energy absorption. The effectiveness of the obtained designs is validated by mechanical testing of specimens, manufactured utilizing rubber casting and 3D printing. This study highlights the efficacy of Bayesian optimization in design, particularly under diverse loading conditions and in the presence of uncertainty. It provides valuable insights into the method's ability to improve the resilience and adaptability of structures, representing a notable advancement in the field.

Military personnel use protective armour systems that are frequently exposed to low-level damage, such as non-ballistic impact, wear-and-tear from everyday use, and damage during storage of equipment. The extent to which such low-level pre-damage could affect the performance of an armour system is unknown. In this work, low-level pre-damage has been introduced into a Kevlar/phenolic resin-starved composite panel using tensile loading. The tensile stress-strain behaviour of this eight-layer material has been investigated and has been found to have two distinct regions; these have been understood in terms of the microstructure and damage within the composite panels investigated using micro-computed tomography and digital image correlation. Ballistic testing carried out on pristine (control) and pre-damaged panels did not indicate any difference in the V50 ballistic performance. However, an indication of a difference in response to ballistic impact was observed; the area of maximal local out-ofplane deformation for the pre-damaged panels was found to be twice that of the control panels, and the global out-of-plane deformation across the panel was also larger.

Armour which is manufactured and distributed for personnel, vehicle and structural protection, primarily for military or policing applications, undergoes stringent testing to ensure that it can meet the demands of a range of impact scenarios. However, the effects of repetitive low-level damage are not fully understood and, in order to maintain a given level of protection, armour is recalled and replaced periodically, which is costly, and may be unnecessary. This paper reports preliminary studies on the relationship between minor damage and the resulting impact resistance of a woven fabric reinforced composite laminate (E-glass with epoxy resin). Specimens were subjected to displacement-controlled fatigue tests to introduce dispersed damage before being subjected to quasi-static indentation testing. The results showed that during penetration of the specimens, the peak load was reduced by approximately 10% for the pre-fatigued specimens, compared to the non-fatigued specimens, and there was some indication the energy absorption also reduced. It is proposed that the development of fibre fractures during the pre-fatigue of the specimens is the origin of these changes.

Aluminium inserts are frequently embedded within the composite sandwich structures used in modern sports cars. Since the inserts are used for attaching safety-critical components to the structure, the adhesion between the metal and composite needs to be strong and durable. The bond is achieved through an epoxy resin system. However, when the resin includes an internal mould release agent (IMR) to facilitate the demoulding process of the structure, the adhesion between the inserts and the composite structure can be compromised. In addition, inserts can be exposed to high treatment temperatures. As such, to ensure that high adhesion performance can still be achieved, an appropriate surface treatment should be applied on the inserts. In this paper, four commercially available surface treatments for aluminium inserts were assessed using single lap joint (SLJ) and double cantilever beam (DCB) tests. Moreover, to investigate the influence of the IMR and the high-temperature process on the joint properties, four sample manufacturing methods were used to prepare the SLJ samples: without IMR and without high-temperature process (Method 1), with IMR (Method 2), with high-temperature process (Method 3) and with both IMR and high-temperature process (Method 4). The DCB samples were only prepared using Method 4. The locus of failure for the SLJ samples prepared with Method 4 was evaluated by using X-ray photoelectron spectroscopy (XPS) and optical microscopy. It was found that a silane-based primer was sensitive to the use of both the IMR and high temperature (31% drop in the lap joint strength when both applied). A cataphoretic electrocoat was also investigated and only deteriorated when exposed to high temperature (up to 40% decrease in the lap joint strength). An epoxy-based primer did not show a significant sensitivity to the IMR, however, when exposed to high-temperatures, the joint became even stronger (up to 15% increase in the lap joint strength).

The mobility of soft tissue can cause inaccurate needle insertions. Particularly in steering applications that employ thin and flexible needles, large deviations can occur between pre-operative images of the patient, from which a procedure is planned, and the intra-operative scene, where a procedure is executed. Although many approaches for reducing tissue motion focus on external constraining or manipulation, little attention has been paid to the way the needle is inserted and actuated within soft tissue. Using our biologically inspired steerable needle, we present a method of reducing the disruptiveness of insertions by mimicking the burrowing mechanism of ovipositing wasps. Internal displacements and strains in three dimensions within a soft tissue phantom are measured at the needle interface, using a scanning laser-based image correlation technique. Compared to a conventional insertion method with an equally sized needle, overall displacements and strains in the needle vicinity are reduced by 30% and 41%, respectively. The results show that, for a given net speed, needle insertion can be made significantly less disruptive with respect to its surroundings by employing our biologically inspired solution. This will have significant impact on both the safety and targeting accuracy of percutaneous interventions along both straight and curved trajectories.

The rise and advancement of minimally invasive surgery (MIS) has significantly improved patient outcomes, yet its technical challenges-such as tissue manipulation and tissue retraction-are not yet overcome. Robotic surgery offers some compensation for the ergonomic challenges, as retraction typically requires an extra robotic arm, which makes the complete system more costly. Our research aimed to explore the potential of rapidly deployable structures for soft tissue actuation and retraction, developing clinical and technical requirements and putting forward a critically evaluated concept design. With systematic measurements, we aimed to assess the load capacities and force tolerance of different magnetic constructions. Experimental and simulation work was conducted on the magnetic coupling technology to investigate the conditions where the clinically required lifting force of 11.25 N could be achieved for liver retraction. Various structure designs were investigated and tested with N52 neodymium magnets to create stable mechanisms for tissue retraction. The simplified design of a new MIS laparoscopic instrument was developed, including a deployable structure connecting the three internal rod magnets with joints and linkages that could act as an actuator for liver retraction. The deployable structure was designed to anchor strings or bands that could facilitate the lifting or sideways folding of the liver creating sufficient workspace for the target upper abdominal procedures. The critical analysis of the project concluded a notable potential of the developed solution for achieving improved liver retraction with minimal tissue damage and minimal distraction of the surgeon from the main focus of the operation, which could be beneficial, in principle, even at robot-assisted procedures.

Penetration of a flexible and steerable needle into a soft target material is a complex problem to be modelled, involving several mechanical challenges. In the present paper, an adaptive finite element algorithm is developed to simulate the penetration of a steerable needle in brain-like gelatine material, where the penetration path is not predetermined. The geometry of the needle tip induces asymmetric tractions along the tool–substrate frictional interfaces, generating a bending action on the needle in addition to combined normal and shear loading in the region where fracture takes place during penetration. The fracture process is described by a cohesive zone model, and the direction of crack propagation is determined by the distribution of strain energy density in the tissue surrounding the tip. Simulation results of deep needle penetration for a programmable bevel-tip needle design, where steering can be controlled by changing the offset between interlocked needle segments, are mainly discussed in terms of penetration force versus displacement along with a detailed description of the needle tip trajectories. It is shown that such results are strongly dependent on the relative stiffness of needle and tissue and on the tip offset. The simulated relationship between programmable bevel offset and needle curvature is found to be approximately linear, confirming empirical results derived experimentally in a previous work. The proposed model enables a detailed analysis of the tool–tissue interactions during needle penetration, providing a reliable means to optimise the design of surgical catheters and aid pre-operative planning.

Minimally Invasive Surgery (MIS) needs continuous tool design innovation to support and facilitate the complex task executions of surgeons. In this article, an easily deployable magnetic structure design is presented, which is developed to retract the liver during MIS procedures. During the concept designing phase, a most critical research question, the stability of magnetic anchoring was investigated and analyzed through various experiments. The clinically relevant pulling forces have been applied to N52 neodymium magnets in different size, shape and arrangement to derive the maximum force certain retractor designs could withheld. The numeric results confirmed that the distributed load arrangement would be able to perform a stable human liver retraction. Magnetic encoring technology could have a significant future, encouraging other researchers to investigate the potential of magnetic tissue retraction in MIS procedures that could lead to the development of specialized tools for human clinical deployment.

X-ray sources are used for both scientific instrumentation and inspection applications. In X-ray photoelectron spectroscopy (XPS), aluminum Kα X-rays are generated through electron beam irradiation of a copper-based X-ray anode incorporating a thin surface layer of aluminum. The maximum power operation of the X-ray anode is limited by the relatively low melting point of the aluminum. Hence, optimization of the materials and design of the X-ray anode to transfer heat away from the aluminum thin film is key to maximizing performance. Finite element analysis has been employed to model the heat transfer of a water-cooled copper-based X-ray anode with and without the use of a CVD (chemical vapour deposited) diamond heat spreader. The modeling approach was to construct a representative baseline model, and then to vary different parameters systematically, solving for a steady state thermal condition, and observing the effect of on the maximum temperature attained. The model indicates that a CVD diamond heat spreader (with isotropic thermal properties) brazed into the copper body reduces the maximum temperature in the 4 μm aluminum layer from 613 °C to 301 °C. Introducing realistic anisotropy in the TC (thermal conductivity) of the CVD diamond has no significant effect on heat transfer if the aluminum film is on the CVD diamond growth face (with the highest TC). However, if the aluminum layer is on the CVD diamond nucleation face (with the lowest TC), the maximum temperature is 575 °C. Implications for anode design are discussed.

Puncturing blood vessels during percutaneous intervention in minimally invasive brain surgery can be a life threatening complication. Embedding a forward looking sensor in a rigid needle has been proposed to tackle this problem but, when using a rigid needle, the procedure needs to be interrupted and the needle extracted if a vessel is detected. As an alternative, we propose a novel optical method to detect a vessel in front of a steerable needle. The needle itself is based on a biomimetic, multi-segment design featuring four hollow working channels. Initially, a laser Doppler flowmetry probe is characterized in a tissue phantom with optical properties mimicking those of human gray matter. Experiments are performed to show that the probe has a 2.1 mm penetration depth and a 1 mm off-axis detection range for a blood vessel phantom with 5 mm s−1 flow velocity. This outcome demonstrates that the probe fulfills the minimum requirements for it to be used in conjunction with our needle. A pair of Doppler probes is then embedded in two of the four working channels of the needle and vessel reconstruction is performed using successive measurements to determine the depth and the off-axis position of the vessel from each laser Doppler probe. The off-axis position from each Doppler probe is then used to generate a 'detection circle' per probe, and vessel orientation is predicted using tangent lines between the two. The vessel reconstruction has a depth root mean square error (RMSE) of 0.3 mm and an RMSE of 15° in the angular prediction, showing real promise for a future clinical application of this detection system.

During minimally invasive surgical procedures, it is often important to deliver needles to particular tissue volumes. Needles, when interacting with a substrate, cause deformation and target motion. To reduce reliance on compensatory intra-operative imaging, a needle design and novel delivery mechanism is proposed. Three-dimensional finite element simulations of a multi-segment needle inserted into a pre-existing crack are presented. The motion profiles of the needle segments are varied to identify methods that reduce target motion. Experiments are then performed by inserting a needle into a gelatine tissue phantom and measuring the internal target motion using digital image correlation. Simulations indicate that target motion is reduced when needle segments are stroked cyclically and utilise a small amount of retraction instead of being held stationary. Results are confirmed experimentally by statistically significant target motion reductions of more than 8% during cyclic strokes and 29% when also incorporating retraction, with the same net insertion speed. By using a multi-segment needle and taking advantage of frictional interactions on the needle surface, it is demonstrated that target motion ahead of an advancing needle can be substantially reduced.