Feedforward control strategies of subjects with transradial amputation in planar reaching.
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The rate of upper-limb amputations is increasing, and the rejection rate of prosthetic devices remains high. People with upper-limb amputation do not fully incorporate prosthetic devices into their activities of daily living. By understanding the reaching behaviors of prosthesis users, researchers can alter prosthetic devices and develop training protocols to improve the acceptance of prosthetic limbs. By observing the reaching characteristics of the nondisabled arms of people with amputation, we can begin to understand how the brain alters its motor commands after amputation. We asked subjects to perform rapid reaching movements to two targets with and without visual feedback. Subjects performed the tasks with both their prosthetic and nondisabled arms. We calculated endpoint error, trajectory error, and variability and compared them with those of nondisabled control subjects. We found no significant abnormalities in the prosthetic limb. However, we found an abnormal leftward trajectory error (in right arms) in the nondisabled arm of prosthetic users in the vision condition. In the no-vision condition, the nondisabled arm displayed abnormal leftward endpoint errors and abnormally higher endpoint variability. In the vision condition, peak velocity was lower and movement duration was longer in both arms of subjects with amputation. These abnormalities may reflect the cortical reorganization associated with limb loss. (+info)
Survival of participating and nonparticipating limb amputees in prospective study: consequences for research.
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This study quantified selection by analyzing the survival rate of the participants and nonparticipants in a 4-year prospective, multicenter cohort study. In addition, the differences between these groups were analyzed. Surgeons of six hospitals in the northern Netherlands referred, in total, 225 patients to the study. Of these patients, 60% (n = 134) participated in the prospective study by filling in questionnaires; the others (nonparticipants) were followed over time through their records. No significant differences were found in sex and level of amputation between participants and nonparticipants; however, of the two groups, nonparticipants were significantly older. Reason for amputation was peripheral vascular disease (PVD) for 67% (n = 90) of the participants and 82% (n = 75) of the nonparticipants. The mean survival time of the participants and nonparticipants was 36.1 and 29.6 months, respectively. Within PVD, the mean survival time of participants and nonparticipants was 34.4 and 27.6 months, respectively.To summarize, our article gives an overview of the survival rates in a prospective study on patients scheduled for a limb amputation. Our study sample was biased by selection and death. Participants were generally healthier than nonparticipants. (+info)
Feasibility of a new concept for measuring actual functional performance in daily life of transfemoral amputees.
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Effects of prosthetic foot forefoot flexibility on oxygen cost and subjective preference rankings of unilateral transtibial prosthesis users.
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The investigators conducted a double-blind randomized crossover study to determine the effects of prosthetic foot forefoot flexibility on oxygen cost and subjective preference rankings of 13 unilateral transtibial prosthesis users. Five experimental feet were fabricated for use in the study: F1, F2, F3, F4, and F5. F1 was most flexible, F5 was least flexible, and F3 was designed to conform to a biomimetic ankle-foot roll-over shape. The experimental feet were modeled after the Shape&Roll prosthetic foot (originally produced by Northwestern University, Chicago, Illinois; now in public domain) but had different numbers of saw cuts within the forefoot members, allowing more or less flexibility during walking. Participants walked at the same comfortable, freely selected speed on the treadmill for 7 min with each foot while energy expenditure was measured. No significant difference was found in oxygen cost (mL O(2)/kg/m) between the different feet (p = 0.17), and the order of use was also not significant (p = 0.94). However, the preference ranking was significantly affected by the flexibility of the feet (p = 0.002), with the most flexible foot (F1) ranking significantly poorer than feet F3 (p = 0.003) and F4 (p = 0.004). Users may prefer prosthetic feet that match the flexibility of an intact ankle-foot system, even though we did not detect an energetic benefit at freely selected speeds. (+info)