Practical methods for controlling powered upper-extremity prostheses

Myoelectric pickups (electrodes and processors for detecting the signal that is recorded as an electromyogram) are the most important human-machine interface for controlling powered upper-extremity prostheses. This article presents a simple explanation of myoelectric signal acquisition and then discusses how these signals are used to control the small motors in electric hands, elbows, wrist rotators, and other similar equipment. The less-familiar switch-based and proportional position-sensing controls are also explained. A complete listing of the major suppliers and products available will aid in understanding a discussion of the criteria for using external power instead of, or along with, body power to control and activate prosthetic function.     

Human distal sciatic nerve fascicular anatomy: implications for ankle control using nerve-cuff electrodes

The design of neural prostheses to restore standing balance, prevent foot drop, or provide active propulsion during ambulation requires detailed knowledge of the distal sciatic nerve anatomy. Three complete sciatic nerves and branches were dissected from the piriformis to each muscle entry point to characterize the branching patterns and diameters. Fascicle maps were created from serial sections of each distal terminus below the knee through the anastomosis of the tibial and common fibular nerves above the knee. Similar branching patterns and fascicle maps were observed across specimens. Fascicles innervating primary plantar flexors, dorsiflexors, invertors, and evertors were distinctly separate and functionally organized in the proximal tibial, common fibular, and distal sciatic nerves; however, fascicles from individual muscles were not apparent at these levels. The fascicular organization is conducive to selective stimulation for isolated and/or balanced dorsiflexion, plantar flexion, eversion, and inversion through a single multicontact nerve-cuff electrode. These neuroanatomical data are being used to design nerve-cuff electrodes for selective control of ankle movement and improve current lower-limb neural prostheses.     

Impotence: evaluation and treatment

Impotence is a multifaceted problem. Complex neurologic pathways intermingle to control specific vascular changes in a tightly controlled hormonal milieu. Although great progress has been made in understanding the mechanism of erection, further studies are needed. Careful history and physical examination along with appropriate laboratory tests and noninvasive penile vascular studies are important in differentiating organic from psychogenic impotence. Understanding the etiology of impotence permits a more logical and effective treatment plan. The advent of the semirigid and inflatable penile prostheses has provided a simple and effective treatment for patients with organic impotence for whom there were no treatment options available in the past. The continued improvement in the design of the prostheses and the simplicity with which they can be implanted have revolutionized the treatment of impotence. With newer prosthetic devices being developed, the penile prosthesis will continue to improve the quality of life for impotent patients.     

Neuroprosthetic Applications of Electrical Stimulation

Neural prostheses are a developing technology that use electrical activation of the nervous system to restore function to individuals with neurological impairment. Neural prostheses function by electrical initiation of action potentials in nerve fibers that carry the signal to an endpoint where chemical neurotransmitters are released, either to affect an end organ or another neuron. Thus, in principle, any end organ under neural control is a candidate for neural prosthetic control. Applications have included stimulation in both the sensory and motor systems and range in scope from experimental trials with single individuals to commercially available devices. Outcomes of motor system neural prostheses include restoration of hand grasp and release in quadriplegia, restoration of standing and stepping in paraplegia, restoration of bladder function (continence, micturition) following spinal cord injury, and electrophrenic respiration in high-level quadriplegia. Neural prostheses restore function and provide greater independence to individuals with disability.     

Neuroprosthetic applications of electrical stimulation

Neural prostheses are a developing technology that use electrical activation of the nervous system to restore function to individuals with neurological impairment. Neural prostheses function by electrical initiation of action potentials in nerve fibers that carry the signal to an endpoint where chemical neurotransmitters are released, either to affect an end organ or another neuron. Thus, in principle, any end organ under neural control is a candidate for neural prosthetic control. Applications have included stimulation in both the sensory and motor systems and range in scope from experimental trials with single individuals to commercially available devices. Outcomes of motor system neural prostheses include restoration of hand grasp and release in quadriplegia, restoration of standing and stepping in paraplegia, restoration of bladder function (continence, micturition) following spinal cord injury, and electrophrenic respiration in high-level quadriplegia. Neural prostheses restore function and provide greater independence to individuals with disability.     

Gatekeeper Reflux Repair System: technique,pre-clinical,and clinical experience

The Gatekeeper Reflux Repair System is a new, promising endoscopic anti-reflux therapy. It has now been shown that it is possible to implant hydrogel prosthesis in the submucosa of the esophagus of humans. The pilot study in humans showed that it is a safe technique and no prostheses migrated into the mediastinum. With the help of endoscopic ultrasonography, each prosthesis was followed during the 6-month pilot study. After finishing this pilot study, new multi-center studies have been initiated with implantation of more prostheses to increase efficacy. One of the definite advantages over the other endoscopic treatments currently being developed is its reversibility. Regarding endoscopic anti-reflux therapy in general, it is important to stress that at this time no data are available in the literature about the comparison to medical therapy. At the same time long-term results are also unknown. For these reasons these endoscopic procedures must be considered experimental and they should be performed in a clinical research setting. Within a few years the role of the Gatekeeper Reflux Repair System will be better understood for those PPI-dependent GERD-patients who wish to stop their medication.     

Comparison of electromyography and force as interfaces for prosthetic control

The ease with which persons with upper-limb amputations can control their powered prostheses is largely determined by the efficacy of the user command interface. One needs to understand the abilities of the human operator regarding the different available options. Electromyography (EMG) is widely used to control powered upper-limb prostheses. It is an indirect estimator of muscle force and may be expected to limit the control capabilities of the prosthesis user. This study compared EMG control with force control, an interface that is used in everyday interactions with the environment. We used both methods to perform a position-tracking task. Direct-position control of the wrist provided an upper bound for human-operator capabilities. The results demonstrated that an EMG control interface is as effective as force control for the position-tracking task. We also examined the effects of gain and tracking frequency on EMG control to explore the limits of this control interface. We found that information transmission rates for myoelectric control were best at higher tracking frequencies than at the frequencies previously reported for position control. The results may be useful for the design of prostheses and prosthetic controllers.     

Muscle activation patterns during walking from transtibial amputees recorded within the residual limb-prosthetic interface

Powered lower limb prostheses could be more functional if they had access to feedforward control signals from the user’s nervous system. Myoelectric signals are one potential control source. The purpose of this study was to determine if muscle activation signals could be recorded from residual lower limb muscles within the prosthetic socket-limb interface during walking. We recorded surface electromyography from three lower leg muscles (tibilias anterior, gastrocnemius medial head, gastrocnemius lateral head) and four upper leg muscles (vastus lateralis, rectus femoris, biceps femoris, and gluteus medius) of 12 unilateral transtibial amputee subjects and 12 non-amputee subjects during treadmill walking at 0.7, 1.0, 1.3, and 1.6 m/s. Muscle signals were recorded from the amputated leg of amputee subjects and the right leg of control subjects. For amputee subjects, lower leg muscle signals were recorded from within the limb-socket interface and from muscles above the knee. We quantified differences in the muscle activation profile between amputee and control groups during treadmill walking using cross-correlation analyses. We also assessed the step-to-step inter-subject variability of these profiles by calculating variance-to-signal ratios. We found that amputee subjects demonstrated reliable muscle recruitment signals from residual lower leg muscles recorded within the prosthetic socket during walking, which were locked to particular phases of the gait cycle. However, muscle activation profile variability was higher for amputee subjects than for control subjects. Robotic lower limb prostheses could use myoelectric signals recorded from surface electrodes within the socket-limb interface to derive feedforward commands from the amputee’s nervous system.     

Muscle activation patterns during walking from transtibial amputees recorded within the residual limb-prosthetic interface

ABSTRACT: BACKGROUND: Powered lower limb prostheses could be more functional if they had access to feedforward control signals from the user's nervous system. Myoelectric signals are one potential control source. The purpose of this study was to determine if muscle activation signals could be recorded from residual lower limb muscles within the prosthetic socket-limb interface during walking. METHODS: We recorded surface electromyography from three lower leg muscles (tibilias anterior, gastrocnemius medial head, gastrocnemius lateral head) and four upper leg muscles (vastus lateralis, rectus femoris, biceps femoris, and gluteus medius) of 12 unilateral transtibial amputee subjects and 12 non-amputee subjects during treadmill walking at 0.7, 1.0, 1.3, and 1.6 m/s. Muscle signals were recorded from the amputated leg of amputee subjects and the right leg of control subjects. For amputee subjects, lower leg muscle signals were recorded from within the limb-socket interface and from muscles above the knee. We quantified differences in the muscle activation profile between amputee and control groups during treadmill walking using cross-correlation analyses. We also assessed the step-to-step intersubject variability of these profiles by calculating variance-to-signal ratios. RESULTS: We found that amputee subjects demonstrated reliable muscle recruitment signals from residual lower leg muscles recorded within the prosthetic socket during walking, which were locked to particular phases of the gait cycle. However, muscle activation profile variability was higher for amputee subjects than for control subjects. CONCLUSION: Robotic lower limb prostheses could use myoelectric signals recorded from surface electrodes within the socket-limb interface to derive feedforward commands from the amputee's nervous system.     

Colorimetric analysis of silicone cosmetic prostheses for upper-limb amputees

Every year the Italian National Insurance Institute of Accidents on Work (INAIL) Prosthesis Centre manufactures more than 300 silicone cosmetic upper-limb prostheses that are aesthetically similar to patients' missing limbs; however, the prostheses have the following drawbacks: subjectivity in color choice, high production costs, and long time frames for patient tests and prosthesis production. In an attempt to minimize these factors, we performed a study to test various systems that automatically detect the color of human skin. Such a system would allow us to reproduce a patient's exact skin color for silicone cosmetic prostheses. We analyzed the color identification systems available on the market and assessed the possibility of introducing such a system into the production cycle of the prostheses. We found that because of intrinsic factors of the materials, automatic color detection for prosthesis production is complex. Therefore, any of the systems we tested will require further development for full satisfaction of the needs of prostheses manufacturers.     

Evaluation of sensation evoked by electrocutaneous stimulation on forearm in nondisabled subjects

Few studies are available in the literature on the sensations artificially created by dual-channel electrocutaneous stimulation. This study assessed the effect of a set of selected stimulation parameters on the sensations evoked by single- or dual-channel electrocutaneous stimulation. The investigated parameters included the stimulation site, the number of pulses, the number of stimulating channels (single- vs dual-channel), and the interleaved time between two channels. The modality, quality, location, and magnitude of the sensations were evaluated when the stimulations were applied on the forearm skin in 16 nondisabled subjects. Tactile perception was found to be induced more easily on the median and ulnar aspect than the dorsal and radial aspect of the forearm. Stimulation site significantly affected the magnitude of the sensation (p < 0.01). Dual-channel stimulation significantly increased the sensation magnitude (p < 0.05) only when the two electrodes were positioned closely. Moreover, a higher number of pulses evoked a movement perception more frequently and the interleaved time showed no significant effect on the magnitude of the sensation. The findings are expected to be useful for sensory substitution and augmentation applications. The results may also help improve users' acceptance of hand prostheses.     

Recent progress of conductive 3D-printed electrodes based upon polymers/carbon nanomaterials using a fused deposition modelling (FDM) method as emerging electrochemical sensing devices

3D-printing or additive manufacturing is presently an emerging technology in the fourth industrial revolution that promises to reshape traditional manufacturing processes. The electrochemistry field can undoubtedly take advantage of this technology to fabricate electrodes to create a new generation of electrode sensor devices that could replace conventionally manufactured electrodes; glassy carbon, screen-printed carbon and carbon composite electrodes. In the electrochemistry research area, studies to date show that there is a demand for electrically 3D printable conductive polymer/carbon nanomaterial filaments where these materials can be printed out through an extrusion process based upon the fused deposition modelling (FDM) method. FDM could be used to manufacture novel electrochemical 3D printed electrode sensing devices for electrochemical sensor and biosensor applications. This is due to the FDM method being the most affordable 3D printing technique since conductive and non-conductive thermoplastic filaments are commercially available. Therefore, in this minireview, we focus on only the most outstanding studies that have been published since 2018. We believe this to be a highly-valuable research area to the scientific community, both in academia and industry, to enable novel ideas, materials, designs and methods relating to electroanalytical sensing devices to be generated. This approach has the potential to create a new generation of electrochemical sensing devices based upon additive manufacturing. This minireview also provides insight into how the research community could improve the electrochemical performance of 3D-printed electrodes to significantly increase the sensitivity of the 3D-printed electrodes as electrode sensing devices.

This minireview discusses the current on-demand applications of the conductive 3D-printed electrodes based upon polymer/carbon nanomaterial filaments, printed using the FDM 3D printing method, in developing electrochemical sensors and biosensors.     

The use of a biocompatible orthopaedic polymer in the treatment of loose total hip prostheses

Seventeen cases of loose total hip prostheses were treated with biocompatible orthopaedic polymer, an osteoconductive co-polymer. Biocompatible orthopaedic polymer permits improved stability and secondary bone repair and may also act as a vehicle for adjunctive antibiotic therapy. The available forms of biocompatible orthopaedic polymer and their methods of application are described and the results obtained with their use are compared with the pre-operative clinical observations. Of the 17 patients studied, pain disappeared in 14, unlimited walking became possible in seven, while another eight patients were subsequently able to walk for over 300 m. Mobility became normal in 13 cases; full weight bearing on one leg became possible in 12 cases and became normal in another four. Radiological examination showed the development of a bony interface between the cortex and the prosthesis as the radiolucent biocompatible orthopaedic polymer material was converted into bone. It may, therefore, be concluded that, in this indication, biocompatible orthopaedic polymer appears to be an active interface for stabilizing loose total hip prostheses.     

Biomechanical evaluation of two types of short-stemmed hip prostheses compared to the trust plate prosthesis by three-dimensional measurement of micromotions

Background

Stemless and short-stemmed hip prostheses have been developed to preserve femoral bone stock. While all these prostheses claim a more or less physiological load transfer, clinical long-term results are only available for the stemless thrust plate prosthesis. In this study, the in vitro primary stability of the thrust plate prosthesis was compared to two types of short-stemmed prostheses. In addition to the well-established Mayo prosthesis, the modular Metha prosthesis was tested using cone adapters with 130° and 140° neck-shaft-angles.

Methods

The prostheses were implanted in composite femurs and loaded dynamically (300–1700 N). Three-dimensional micromotions at the bone-prosthesis interface were measured. In addition, the three-dimensional deformations at the surface of the composite femur were measured to gain data on the strain distribution.

Findings

For all tested prostheses, the micromotions did not exceed 150 μm, the critical value for osteointegration. The thrust plate prosthesis revealed similar motions as the short-stemmed prostheses. The short-stemmed prosthesis with the 130° cone tended to have the highest micromotions of all tested short-stemmed prostheses. The thrust plate prosthesis revealed the lowest alteration of bone surface deformation after implantation.

Interpretation

The comparably low micromotions of the thrust plate prosthesis and the short-stemmed prostheses should be conducive to osseous integration. The higher alteration of load transmission after implantation reveals a higher risk of stress shielding for the short-stemmed prostheses.     

Single-walled carbon nanotubes deposited on surface electrodes to improve interface impedance

A suspension of commercially available single-walled carbon nanotubes (SWNTs) is directly deposited onto a platinum multielectrode array surface. This is a novel and easy method to reduce interface impedance values which can be used instead of electromodified electrodes. This paper shows that this deposition method is a useful technique for the modification of patterned electrodes ranging in the micro scale. A thorough comparison between the common and well-known black platinum versus SWNTs, as interface material for different electrode areas, has been carried out. SWNTs-based electrodes smaller than 40 microm ? improve the interface impedance values when compared to black platinum-modified electrodes of the same size. The best results can be found for the 10 microm ?, which improves the electrode resistance by 25% in comparison with the black platinum ones. The lower resistance and higher capacitance calculated for the 40 microm diameter SWNTs-based electrode, in comparison with black platinum, also evidence a clear increment of the effective area, which is directly related to the impedance decrease.     

Intraoperative study of polarization and evoked response signals in different endocardial electrode designs

Some new generation pacemakers use an algorithm based on evoked response (ER) detection to verify beat-to-beat capture and to enable automatic adjustment of output. This is a prospective acute study of polarization signal (PS) and ER in nine currently available electrodes. Intraoperative testing of ventricular bipolar electrodes used the Autocapture (AC) algorithm. The intrinsic R wave, PS, ER, acceptance of AC function, and stimulation thresholds (STs) were obtained. Ventricular electrodes were categorized as follows: titanium nitride (TiN)-coated passive and active fixation, high impedance (HI), passive fixation (VP), iridium oxide-coated titanium (IROX) (VI), and platinum helix (PH) active fixation. Acute testing was performed in 217 patients with an average age of 74.26 years, 59.6% were men with primary pacing indication-SSS (46.3%). There were no significant differences found with respect to R wave and threshold between the various electrodes. PH active-fixation electrodes had significantly higher ER and PS than other groups including the TiN-coated active-fixation electrodes. TiN-coated electrodes (active and passive fixation) had significantly lower PS than other electrodes. As a result, TiN electrodes had a significantly higher functional rate of AC (91.7%), whereas PH had the lowest rate (0%). In conclusion, (1) polarization characteristics are significantly different for commercially available ventricular electrodes, (2) certain physical features at the tissue to electrode interface like TiN coating appears to be more important in determining PS than electrode tip size and fixation method, and (3) the current algorithm for AC requires electrodes that provide low polarization for satisfactory performance.     

Cardiac Electrodes and Electrograms: Some New Observations and Concerns

Electrode studies have been performed with dead animal tissue and a variety of other materials immersed in saline solution and compared with studies in the canine heart (live and arrested) in an attempt to delineate both normal and anomalous signals sensed by pacemaker electrodes or obtained during diagnostic electrogram recording of cardiac activity. The data from these studies could be useful for defining the origin of artifacts and a variety of other phenomenon such as "fractured" QRS complexes, acute ST segment elevations, His bundle oscillatory signatures, and unexplained potentials synchronously associated with cardiac events. The studies verify that artifacts can be generated in an electrolyte medium by rubbing electrodes against insulators or biologic materials and by inducing motion between common pole materials of an active electrode system. The studies suggest that some of the grasping electrodes in current clinical use may be subject to self-generating artifacts associated with cardiac-induced frictional motion between the constituent materials employed in the electrode design.     

Biomechanical analysis of total elbow replacement with unlinked iBP prosthesis: an in vitro and finite element analysis

Background

Numerous models of elbow prostheses are being used and can be divided into two categories: one being a semi-constrained, linked type; and the other being non-constrained, unlinked type. Recent reports of National Elbow Arthroplasty Registers reveal no significant differences in the survival rates between linked and unlinked prosthesis brands, and the main cause appointed for revision for both types is loosening. Some previous biomechanical studies confirm the presence of abnormal bone stresses for the linked type, which can be associated with the risk of loosening. However for the unlinked type, biomechanical studies are not available that corroborate a loosening risk. It seems, that issue has not yet been fully answered and requires further analysis.

Methods

Cortex strains adjacent to the elbow joint were measured with strain gauges in synthetic humeri and ulnae, before and after replacement. To assess cancellous bone strains and cement stresses around the implant finite element models validated relative to measured strains were used.

Findings

Bone strains adjacent to the implant tip increased several times in the humerus and ulna. At the epiphyseal regions a generalised cancellous bone strain reduction was observed for both humerus and ulna relatively to the intact bones.

Interpretation

The unlinked elbow prostheses can be associated with the risk of bone fatigue failure by overload, particularly in the ulna, and bone resorption by stress-shielding at the epiphyseal regions. The identical structural behaviour relative to linked prostheses associated with the same loosening risks corroborates the results of recent arthroplasty published register reports.     

Patient education for women being fitted for breast prostheses

Women who undergo mastectomy or other types of breast surgery often will be fitted for breast prostheses for therapeutic weight replacement as well as cosmetic purposes. Nurses are instrumental in educating women about issues related to breast surgery and in helping to promote psychosocial adjustment to the diagnosis and subsequent treatment. Nurses often are involved in the referral process for breast prostheses. Prostheses and bras that fit properly can be very important in the recovery process and ultimately improve quality of life for cancer survivors. Unlike in the past, many choices are available today for women who opt to use breast prostheses. Prostheses come in different colors, shapes, and weights, and some adhere to the chest wall. Many options also are available for bras, camisoles, and swimsuits, which are helpful adjuncts to the fit of the prosthesis. The purpose of this article is to describe the fitting process and options currently available for breast prostheses. Nurses can use this information to inform women of available breast prostheses options and help prepare them for a fitting.     

Photopolymerized micropatterns with high feature frequencies overcome chemorepulsive borders to direct neurite growth

Developing and regenerating neurites respond to a variety of biophysical and biochemical cues in their micro‐environment to reach target cells and establish appropriate synapses. Defining the hierarchal relationship of both types of cues to direct neurite growth carries broad significance for neural development, regeneration, and, in particular, engineering of neural prostheses that improve tissue integration with native neural networks. In this work, chemorepulsive biochemical borders are established on substrates with a range of surface microfeatures to determine the potential of physical cues to overcome conflicting biochemical cues. Physical micropatterns are fabricated using photomasking techniques to spatially control photoinitiation events of the polymerization. Temporal control of the reaction allows for generation of microfeatures with the same amplitude across a range of feature frequencies or periodicities. The micropatterned substrates are then modified with repulsive chemical borders between laminin and either EphA4‐Fc or tenascin C that compete with the surface microfeatures to direct neurite growth. Behaviour of neurites from spiral ganglion and trigeminal neurons is characterized at biochemical borders as cross, turn, stop, or repel events. Both the chemical borders and physical patterns significantly influence neurite pathfinding. On unpatterned surfaces, most neurites that originate on laminin are deterred by the border with tenascin C or EphA4‐Fc. Importantly, substrates with frequent micropattern features overcome the influence of the chemorepulsive border to dominate neurite trajectory. Designing prosthesis interfaces with appropriate surface features may allow for spatially organized neurite outgrowth in vivo even in the presence of conflicting biochemical cues in native target tissues.