PubMed · 13363728
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1956. IMPROVED harness material.. https://pubmed.ncbi.nlm.nih.gov/13363728/
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An electromechanical system is described that comprises a cam and two linear displacement transducers for measuring two-degree of freedom. This is aimed at quantifying the extent and pattern of both transverse rotation and longitudinal translation that takes place during amputee gait at what is sometimes termed a "torque-shock absorbing adapter" located between the prosthetic socket and foot. Both types of motion are measured independently by mounting the cam around the adapter and the two transducers orthogonal to one another with their spring loaded plungers moving separately against the cam's perimeter and distal, flat face. The cam geometry should be an arc of a spiral and not a circle for the angular displacement measurement to be linear in response to rotation. Over a range of +/-18 degrees for transverse rotation the maximum deviation of the ideal cam geometry away from an arc of a circle is less than +/-0.5% of the transducers' 10 mm stroke. The transducer's linearity is +/-2% and it could therefore be assumed that this would be the dominant source of error. The theoretical predictions are supported by the calibration results, in which the pattern of errors that are found in the transducers' calibration can also be seen in the calibration of the cam.
Prosthetic manufacturers have developed shock-absorbing pylons to attenuate the transient forces of foot-ground contact in order to supplement the residual capacity of lower limb amputees. The purpose of this study was to measure the elastic and damping properties of two frequently prescribed pylons (the ICON Shock Pylon and the Mercury TT Pyramid Pylon) at frequencies enveloping those observed during gait using pseudo-static compressive and dynamic cyclic testing methods. Results showed that the spring constants were linear functions of deformation (ranging from 74 to 110 N/mm and 91 to 157 N/mm for the ICON and the TT Pylons, respectively) while the damping force was a function of the square root of velocity combined with a coulomb element (1.6x0.5 + 21 and 7.4x0.5 + 102 N for the ICON and the TT Pylon, respectively).
Within the last couple of years, partial restoration of lost motor functions in a larger number of spinal cord injured patients has become possible by the introduction of neuroprostheses into the clinical environment. The Freehand system in particular is the first implantable neuroprosthesis from which a certain group of tetraplegic patients with stable shoulder function, but missing or weak grasp and hold function of the hand do benefit. The system is based on the combination of electrical stimulation and operative tendon transfers and thus represents a multicomponent concept for long-term restoration of the grasp function. The crucial prerequisites for successful use of an implantable neuroprosthesis are the right indication, careful preoperative muscle stimulation, differentiated planning of the surgery and functional training adopted to the individual residual functions. After successful completion of an extensive rehabilitation program, patients are able to use the system for activities of daily living without the need for special additional aids, which enhances their quality of life and independency. In order to extend the group of potential users of neuroprostheses in the future, new technological developments will have to take into account that nowadays the majority of spinal cord injured patients suffer from an incomplete lesion of the spinal cord. For these particular patients who still possess residual functions, modular, "naturally" controllable systems for supporting these functions are needed rather than complex systems to substitute them.