PubMed · 4667254
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A Staros. 1972. [Plastics and prostheses].. https://pubmed.ncbi.nlm.nih.gov/4667254/
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Monolimb refers to a transtibial prosthesis with the prosthetic socket and the shank being molded into one piece of thermoplastic material. Shank flexibility of a monolimb can improve gait and comfort. However, fatigue failure of monolimbs under cyclic walking load is an important concern. This study is to evaluate the fatigue life of a monolimb designed for a transtibial amputee, based on finite element analysis, the statistical Miner's rule and reliability analysis. Stress uncertainty due to modeling error and the scatter in fatigue test data were considered. Results indicated that the accuracy of fatigue life evaluation of monolimb depends significantly on the precision of stress estimation. In addition, relationship between fatigue failure probability and the number of walking steps was suggested providing a reference for clinicians to determine the interval of the inspection for the monolimb.
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.
Increasing evidence suggests that the visual analysis of other people's actions depends upon the observer's own body representation or schema. This raises the question of how differences in observers' body structure and schema impact their perception of human movement. We investigated the visual experiences of two persons born without arms, one with and the other without phantom sensations. These participants, plus six normally-limbed control observers, viewed depictions of upper limb movement under conditions of apparent motion. Consistent with previous results (Shiffrar M, Freyd JJ (1990) Psychol Sci 1:257), normally-limbed observers perceived rate-dependent paths of apparent human movement. Specifically, biologically impossible motion trajectories were reported at rapid display rates while biologically possible trajectories were reported at slow display rates. The aplasic individual with phantom experiences showed the same perceptual pattern as control participants, while the aplasic individual without phantom sensations did not. These preliminary results suggest that phantom experiences may constrain the visual analysis of the human body. These results further suggest that it may be time to move beyond the question of whether aplasic phantoms exist and instead focus on the question of why some people with limb aplasia experience phantom sensations while others do not. In this light, the current results suggest that somesthetic representations are not sufficient to define body schema. Instead, neural systems matching action observation, action execution and motor imagery likely contribute to the definition of body schema in profound ways. Additional research with aplasic individuals, having and lacking phantom sensations, is needed to resolve this issue.