Preliminary design analysis of linkage feeders.

In 1962 the Committee on Prosthetics Research and Development authorized a survey of current orthotics research and development in a number of selected centers as an initial step in a proposed orthotics evaluation program. A prime purpose of the survey was the identification of orthotic devices and procedures as suitable subject matter for the evaluation program. One of the devices selected as meeting the requirements for inclusion in the evaluation process was the linkage feeder designed at the University of Michigan. However, it was apparent that this device, plus a number of others, was essentially a variant of the ballbearing feeder designed and developed two decades ago by the (ieorgia Warm Spr ing Foundation. Hence, a review of existing feeder designs was undertaken as a prelude to any formal evaluation program. The systems involved were those currently in use at the Georgia Warm Springs Foundation, Rancho Los Amigos Hospital, the University of Michigan, the Texas Rehabilitation Center, and the Texas Institute for Rehabilitation and Research. Two prefabricated units that were available commercially were also reviewed, but these units resemble the Rancho Los Amigos Hospital feeder so closely that separate consideration is not warranted. Ideally, a feeder supports the weight of the arm and permits the patient with severely weakened or paralyzed upper extremities to position the hand with a minimum of muscular effort. The extent of a patient's performance with a feeder and his method of performance are, of course, contingent on the nature and extent of his disability. The feeders considered in this article have numerous structural features and operational principles in common. An aluminum forearm trough and two stainless-steel swivel arms that rotate on ball or needle bearings support the weight of the upper extremity and provide useful motion when activated by a slight residual motor power in the head, neck, trunk, or arms. The joint cylinders may be rotated to bring the feeder assembly into an inclined plane which provides gravity assistance to the horizontal motions of the extremity. The trough pivot may be positioned to give a bias to both vertical motions of the forearm, namely, raising the hand to the head or lowering it to the table top. A number of accessory components may be attached to a feeder to adapt the equipment to individual requirements without modifying the basic design. Among these are metal clips, straps, and foam-rubber liners to prevent slip-