Surface myomechanical responses recorded on a scanner galvanometer

Temporary Protective Shoulder Implants for Revision Surgery with Bone Glenoid Grafting

This article describes the development of a temporary protective glenoid prosthesis placed between the augmentation and humeral head prosthesis during the healing phase of shoulder prosthesis revision with necessary reconstruction of the bony structure of the glenoid. The glenoid protection prosthesis ensures the fixation of the augmentation material and protects the screws from contact with the metallic humeral head prosthesis. Another approach of the development is a reduction of the resorption of the augmentation by targeted mechanical stimulation of the tissue. The aim should be to achieve significantly improved conditions for the implantation of a new glenoid component at the end of the healing phase of the augmentation material in comparison to the current standard method. The development of the protective prosthesis was carried out according to specific needs and includes the collection of requirements and boundary conditions, the design and technical detailing of the implant, the verification of the development results as well as the validation of the design. For the verification, FEM simulations (Finite Element Analysis) were performed to estimate the mechanical stability in advance. Mechanical tests to confirm the stability and abrasion behavior have been carried out and confirm the suitability of the protective implant. The result of the present work is the detailed technical design of two variants of a glenoid protective prosthesis "GlenoProtect" for use in revision procedures on shoulder joints-with large-volume defects on the glenoid-treated by arthroplasty and the necessity of augmenting the glenoid, including a description of the surgical procedure for implantation.

Assessment of muscle activity using electrical stimulation and mechanomyography: a systematic review

This research has proved that mechanomyographic (MMG) signals can be used for evaluating muscle performance. Stimulation of the lost physiological functions of a muscle using an electrical signal has been determined crucial in clinical and experimental settings in which voluntary contraction fails in stimulating specific muscles. Previous studies have already indicated that characterizing contractile properties of muscles using MMG through neuromuscular electrical stimulation (NMES) showed excellent reliability. Thus, this review highlights the use of MMG signals on evaluating skeletal muscles under electrical stimulation. In total, 336 original articles were identified from the Scopus and SpringerLink electronic databases using search keywords for studies published between 2000 and 2020, and their eligibility for inclusion in this review has been screened using various inclusion criteria. After screening, 62 studies remained for analysis, with two additional articles from the bibliography, were categorized into the following: (1) fatigue, (2) torque, (3) force, (4) stiffness, (5) electrode development, (6) reliability of MMG and NMES approaches, and (7) validation of these techniques in clinical monitoring. This review has found that MMG through NMES provides feature factors for muscle activity assessment, highlighting standardized electromyostimulation and MMG parameters from different experimental protocols. Despite the evidence of mathematical computations in quantifying MMG along with NMES, the requirement of the processing speed, and fluctuation of MMG signals influence the technique to be prone to errors. Interestingly, although this review does not focus on machine learning, there are only few studies that have adopted it as an alternative to statistical analysis in the assessment of muscle fatigue, torque, and force. The results confirm the need for further investigation on the use of sophisticated computations of features of MMG signals from electrically stimulated muscles in muscle function assessment and assistive technology such as prosthetics control.

Objective assessment of the fusion frequency in functional electrical stimulation using the fast Fourier transform

In functional electrical stimulation (FES) the dynamics of tetanic muscle contractions is often described by the fusion frequency (FF), as determined by palpation: contractions elicited by stimulation frequencies above the FF appear smooth. To contribute to a more objective assessment of this important FES parameter, we have developed a dedicated signal analysis method based on fast Fourier transformation (FFT). The ripple to peak ratio (R(rpFFT)) - the relation between ripple amplitude and peak force value of a recorded tetanic muscle force in relation to the applied stimulation frequency - was determined automatically by analysing a 0.2-s interval in the steady state of a stimulation burst. The method was tested on simulated data and on force recordings from isolated tibialis anterior muscles of six rabbits. The results were compared to manual estimates. The robustness of the method was tested by adding noise and hum. Simulated noise at 100% of the ripple force increased R(rpFFT) by 4%. Hum at 20 Hz away from the stimulation frequency caused changes of less than 0.5%. The results of the automated analysis of recorded signals matched the manual estimates sufficiently well, especially for stimulation frequencies near or above FF. R(rpFFT) therefore seems suitable for automated, objective and robust assessment of the ripple and the FF of electrically stimulated muscle.

Sonomyography: monitoring morphological changes of forearm muscles in actions with the feasibility for the control of powered prosthesis

Electromyography (EMG) has been widely used for the assessment of musculoskeletal functions and the control of electrical prostheses, which make use of the EMG signal generated by the contraction of the residual muscles. In spite of the successful applications of EMG in different fields, it has some inherent limitations, such as the difficulty to differentiate the actions of neighboring muscles and to collect signals from deep muscles using the surface EMG. The majority of current EMG controlled prostheses can only provide sequential on-off controls using signals from two groups of muscles, so the users are required to put many conscious efforts in monitoring the speed and range of motion of the terminal devices being controlled. Recently, many alternative signals based on the detection of dimensional changes of muscles or tendons during actions have been reported. The objective of this study was to investigate the potential of the dimensional change of muscles detected using sonography for musculoskeletal assessment and control. A portable B-mode ultrasound scanner was used to collect the dynamic ultrasound images of the forearm muscles of six normally limbed young adults and three amputee subjects. A motion analysis system was used to collect the movement of the wrist angle during the experiments for the normal subjects. It was demonstrated that the morphological changes of forearm muscles during actions can be successfully detected by ultrasound and linearly correlated (R(2)=0.876+/-0.042, mean+/-S.D.) with the wrist angle. We named these sonographically detected signals about the architectural change of the muscle as sonomyography (SMG). The mean ratio between the wrist angle and the percentage deformation of the forearm muscle was 7.2+/-3.7 degrees /% for the normal subjects. The intraclass correlation coefficient (ICC) of this ratio among the three repeated tests was 0.868. The SMG signals from the residual forearms were also successfully detected when the three amputee subjects contracted their residual muscles. The results demonstrated that SMG had potentials for the musculoskeletal control and assessment.

Validation of an accelerometer for determination of muscle belly radial displacement

A commercial variable-capacitance micromachined accelerometer was validated for muscle belly radial displacement measurement. The displacement was calculated by the acceleration data being integrated twice and was compared with the results obtained simultaneously by an accurate mechanical displacement sensor based on an optical encoder. The aim of the investigation was to evaluate the accuracy and precision of an accelerometer for tensiomyography, which is a method for the detection of skeletal muscle contractile properties on the basis of muscle belly radial displacement. A hundred measurements at a bandwidth of 2300 Hz were performed. It was shown that the accuracy and precision in determination of the maximum displacement and the time of the maximum displacement from the calculated curve were satisfactory, in spite of the standard deviation of the twice-integrated acceleration growing approximately linearly with time. The results were accurate enough since the elapsed time from the beginning of the integration was small (less than 75 ms). The measured maximum displacement ranges were between 9.2 and 10.2 mm. The mean relative error was less than 1% (SD = 0.02mm) for the maximum displacement and about 1% (SD = 0.6 ms) for the time to maximum displacement. The accuracy of the half-relaxation time determination was more uncertain because of the relatively high relative error of -2.4% (SD = 3 ms). Results showed that a commercial micromachined accelerometer could be suitable for the measurement of muscle belly radial displacement and used for development of a future miniaturised and flexible system for the measurement of similar displacements.

Influence of Contact Forces on Wrist Photo plethysmography – Prestudy for a Wearable Patient Monitor / Einfluß von Kontaktkräften auf die photoplethysmografische Pulsmessung am Handgelenk – Vorstudie zu einem tragbaren Patientenmonitor

The practical setting shows that gentle manual pressure on a photosensor suffices to improve the detectability of arterial pulses, but changes in the pressure applied may also produce signal artefacts. To study these effects, stepwise increasing contact forces (0.5 to 4 N) were applied to a photosensor placed over the radial artery. Additionally, the influence of optical coupling between sensor and skin surface was examined by introducing an elastic distance ring. The AC and DC components from the recorded photoplethysmogram were analysed. The AC component (absorption due to arterial pulsation) increased with the pressure applied; at lower forces (0.5 to 3 N) an introduction of the ring enhanced this effect. The characteristic of the DC component (backscattering from non-pulsating tissues) depends on optical coupling: without the ring the DC component increased stepwise with force (slope 0.035 V/N), but with the ring in place this component decreased (slope -0.075 V/N). Since the sensitivity of the pulse signal to artifacts is related to the slope of the DC component, such artefacts can be minimized by making the slope small. The utilization of these results to improve pulse detection and reduce motion artefacts in a wearable wrist device is discussed.