Cutting Edge Bionics in Highly Impaired Individuals: A Case of Challenges and Opportunities.

Highly impaired individuals stand to benefit greatly from cutting-edge bionic technology, however concurrent functional deficits may complicate the adaptation of such technology. Here, we present a case in which a visually impaired individual with bilateral burn injury amputation was provided with a novel transradial neuromusculoskeletal prosthesis comprising skeletal attachment via osseointegration and implanted electrodes in nerves and muscles for control and sensory feedback. Difficulties maintaining implant hygiene and donning and doffing the prosthesis arose due to his contralateral amputation, ipsilateral eye loss, and contralateral impaired vision necessitating continuous adaptations to the electromechanical interface. Despite these setbacks, the participant still demonstrated improvements in functional outcomes and the ability to control the prosthesis in various limb positions using the implanted electrodes. Our results demonstrate the importance of a multidisciplinary, iterative, and patient-centered approach to making cutting-edge technology accessible to patients with high levels of impairment.

Electromyography-Based Control of Lower Limb Prostheses: A Systematic Review.

Most amputations occur in lower limbs and despite improvements in prosthetic technology, no commercially available prosthetic leg uses electromyography (EMG) information as an input for control. Efforts to integrate EMG signals as part of the control strategy have increased in the last decade. In this systematic review, we summarize the research in the field of lower limb prosthetic control using EMG. Four different online databases were searched until June 2022: Web of Science, Scopus, PubMed, and Science Direct. We included articles that reported systems for controlling a prosthetic leg (with an ankle and/or knee actuator) by decoding gait intent using EMG signals alone or in combination with other sensors. A total of 1,331 papers were initially assessed and 121 were finally included in this systematic review. The literature showed that despite the burgeoning interest in research, controlling a leg prosthesis using EMG signals remains challenging. Specifically, regarding EMG signal quality and stability, electrode placement, prosthetic hardware, and control algorithms, all of which need to be more robust for everyday use. In the studies that were investigated, large variations were found between the control methodologies, type of research participant, recording protocols, assessments, and prosthetic hardware.

The effect of cortical thickness and thread profile dimensions on stress and strain in bone-anchored implants for amputation prostheses.

Skeletal attachment of limb prostheses ensures load transfer between the prosthetic leg and the skeleton. For individuals with lower limb amputation, these loads may be of substantial magnitude. To optimize the design of such systems, knowledge about the structural interplay between implant design features, dimensional changes, and material properties of the implant and the surrounding bone is needed. Here, we present the results from a parametric finite element investigation on a generic bone-anchored implant system of screw design, exposed to external loads corresponding to average and high ambulatory loading. Of the investigated parameters, cortical thickness had the largest effect on the stress and strain in the bone-anchored implant and in the cortical bone. 36%-44% reductions in maximum longitudinal stress in the bone-anchored implant was observed as a result of increased cortical thickness from 2 mm to 5 mm. A change in thread depth from 1.5 mm to 0.75 mm resulted in 20%-22% and 10%-18% reductions in maximum longitudinal stress in the bone-anchored implant at 2 mm and 5 mm cortical thickness respectively. The effect of changes in the thread root radius was less prominent, with 8% reduction in the maximum longitudinal stress in the bone-anchored implant being the largest observed effect, resulting from an increased thread root radius from 0.1 mm to 0.5 mm at a thread depth of 1.5 mm. Autologous transplantation of bone tissue distal to the fixture resulted in reductions in the longitudinal stress in the percutaneous abutment. The observed stress reduction of 10%-31% was dependent on the stiffness of the transplanted bone graft and the cortical thickness of surrounding bone. Results from this investigation may guide structural design optimization for bone-anchored implant systems for attachment of limb prostheses.

Low plasticity burnishing improves fretting fatigue resistance in bone-anchored implants for amputation prostheses.

Fretting fatigue is a common problem for modular orthopedic implants which may lead to mechanical failure of the implant or inflammatory tissue responses due to excessive release of wear debris. Compressive residual stresses at the contacting surfaces may alleviate the problem. Here we investigate the potential of a surface enhancement method known as low plasticity burnishing (LPB) to increase the fretting fatigue resistance of bone-anchored implants for skeletal attachment of limb prostheses. Rotation bending fatigue tests performed on LPB treated and untreated test specimens demonstrate that the LPB treatment leads to statistically significantly increased resistance to fretting fatigue (LPB treated test specimens withstood on average 108,780 load cycles as compared with 37,845 load cycles for untreated test specimens, p = 0.004). LPB treated test specimens exhibited less wear at the modular interface as compared with untreated test specimens. This surface treatment may lead to reduced risk of fretting induced component failure and a reduced need for revision of implant system componentry.

Design of a stepwise safety protocol for lower limb prosthetic risk management in a clinical investigation.

In research on lower limb prostheses, safety during testing and training is paramount. Lower limb prosthesis users risk unintentional loss of balance that can result in injury, fear of falling, and overall decreased confidence in their prosthetic leg. Here, we present a protocol for managing the risks during evaluation of active prosthetic legs with modifiable control systems. We propose graded safety levels, each of which must be achieved before advancing to the next one, from laboratory bench testing to independent ambulation in real-world environments.

Design of an open-source transfemoral, bypass socket.

The development of control algorithms and prosthetic hardware for lower limb prostheses involves an iterative testing process. Here, we present the design and validation of a bypass socket to enable able-bodied researchers to wear a leg prosthesis for evaluation purposes. The bypass socket can be made using a 3D-printer and standard household tools. It has an open-socket design that allows for electromyography recordings. It was designed for people with a height of 160 - 190 cm and extra caution should be observed with users above 80 kg. The use of a safety harness when wearing a prosthesis with the bypass socket is also recommended for additional safety.Clinical Relevance-This makes the development process of transfemoral prosthetic components more time- and cost-efficient.

Load exposure of osseointegrated implants for transfemoral limb prosthesis during running.

Direct skeletal attachment of lower limb prostheses ensures direct load transfer between the prosthetic leg and the skeleton. Knowledge of the load characteristics at the boneimplant interface during high-loading activities is needed to understand the limitations of current implant systems, as well as to inform their future development. The present study estimates the load scenario at the bone-implant interface of a transfemoral amputee while running with kinematic symmetry between the prosthetic and the intact limbs corresponding to that of an ablebodied subject. Kinematic symmetry was used as this represents the ultimate aim of advanced bionic legs. Kinematic data and ground reaction forces from a running trial of an able-bodied subject were matched to a musculoskeletal model of a transfemoral amputee. The joint reaction forces at the boneimplant interface were calculated using inverse dynamics. The normalized peak forces and moments during a single gait cycle were calculated to 153 % BW (body weight) / -14.8 % BWm, 186 % BW / 16.2 % BWm and 56.8 % BW / -18.7 % BWm for the x- (anterior), y- (longitudinal), and z-axis (lateral-medial), respectively. These findings can potentially be used as design input for future implant systems and external safety devices.

Biomechanical Characterisation of Bone-anchored Implant Systems for Amputation Limb Prostheses: A Systematic Review.

Bone-anchored limb prostheses allow for the direct transfer of external loads from the prosthesis to the skeleton, eliminating the need for a socket and the associated problems of poor fit, discomfort, and limited range of movement. A percutaneous implant system for direct skeletal attachment of an external limb must provide a long-term, mechanically stable interface to the bone, along with an infection barrier to the external environment. In addition, the mechanical integrity of the implant system and bone must be preserved despite constant stresses induced by the limb prosthesis. Three different percutaneous implant systems for direct skeletal attachment of external limb prostheses are currently clinically available and a few others are under investigation in human subjects. These systems employ different strategies and have undergone design changes with a view to fulfilling the aforementioned requirements. This review summarises such strategies and design changes, providing an overview of the biomechanical characteristics of current percutaneous implant systems for direct skeletal attachment of amputation limb prostheses.