22.214.171.124.1 Pinch force
Lateral and palmar grasp force increased in every subject (n = 43). The median lateral pinch force with stimulation was 12 Newtons, with some pinch forces greater than 25 Newtons. Without stimulation, subjects were able to use their tenodesis grasp to achieve a median of 1.6 Newtons. Similarly, subjects achieved a median palmar grip force of 6.4 Newtons with stimulation, but only a median of 0.7 Newtons voluntarily. These are statistically significant increases.
All subjects had a complete absence of voluntary movement of both the fingers and thumb, and all subjects demonstrated movement of all five digits with stimulation (n = 43). Range of motion with stimulation was, however, less than normal in most subjects, with a median total range of motion (sum of the range of all three joints for a single digit) of approximately 80 degrees for each digit including the thumb. Frequently, full normal range of motion cannot be achieved because of the presence of joint contractures, particularly at the proximal interphalangeal (PIP) joint.
The neuroprosthesis provided 98% (42/43) of the subjects with the ability to manipulate at least one more object than they could manipulate without the neuroprosthesis, and 86% could manipulate at least three additional objects or could manipulate all six objects in the test. Typically, subjects could grasp the two lightest objects both with and without the neuroprosthesis. The major difference in performance was exhibited in grasping heavier objects. For example, none of the subjects could manipulate the weight object without their neuroprosthesis, but 93% were successful with their neuroprosthesis. In addition, the number of completions was statistically significantly higher for all objects except the block and peg.
Subjects demonstrated improved independence using the neuroprosthesis in various activities. Subjects use the neuroprosthesis to perform activities such as using a utensil to eat, drinking from a glass, writing, using a phone, shaving, brushing teeth, brushing hair, putting on make-up, and painting. Twenty-five subjects have been tested on at least four different tasks each, and in every case (100%), subjects demonstrate improved performance in at least two tasks, as shown in Figure 2.2. Twenty-four of these subjects required physical assistance or adaptive equipment to accomplish at least one of the tasks tested, and in every case they were more independent using their neuroprosthesis in at least one of those tasks. The tasks in which subjects showed the most consistent improvement were eating with a fork, brushing teeth, and writing.
The neuroprosthesis reduces the subject's need for assistance and enables him or her to use non-adapted objects. For example, without stimulation, subjects generally lack the ability to stab with a fork. In order to accomplish this task, they use a fork with a built-up handle or they place a fork in a cuff strapped to their hand. They may or may not be able to strap the cuff on their hand themselves. They may also need help getting the fork out of the cuff, making it difficult to switch to another utensil. However, with the strong lateral pinch provided by the neuroprosthesis, subjects can often pick up and use an unmodified fork for eating, and they can easily put the fork down and pick up a spoon or knife.
The neuroprosthesis also provides a more secure grasp. Many subjects can pick up a glass without the neuroprosthesis by squeezing the glass between their two palms
and bringing it to their mouth. However, subjects report a much more secure grip on the glass using the palmar grasp in their neuroprosthesis. In addition, subjects prefer being able to pick up a glass with just one hand because it frees their other hand for other tasks (such as balance support), and because it looks more normal. In general, the neuroprosthesis improves subjects' independence in performing a task, improves the quality of the task, and enables subjects to perform tasks more normally.
Twenty-three subjects have been surveyed at least one year after implantation of their neuroprosthesis regarding their satisfaction and utilization of the neuropros-thesis. Ninety-one percent reported overall satisfaction with the neuroprosthesis. Eighty-seven percent said that it was easier to perform activities of daily living using their neuroprosthesis and that they could perform more activities using the neuro-prosthesis. Ninety-five percent said that they would recommend the neuroprosthesis to other individuals. Each subject was asked to identify the number of days per week that they typically donned their neuroprosthesis and used it for functional tasks. Eighty-three percent reported that they used the neuroprosthesis at least three days per week, with more than half of those subjects indicating that they used the neuroprosthesis every day.
In summary, the neuroprosthesis reduces the impairment by providing grasp opening, pinch force, and grasp-release ability to every subject. The neuroprosthesis reduces functional limitation by enabling every subject to perform many activities of daily living more independently. The survey results indicate that disability is reduced for nearly all subjects, and the majority of subjects become regular users of the neuroprosthesis.
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