Hook and Ladder: Temporary Upper-Limb Prosthesis
R. F. CASSIDY, Jr., PHDAND MILDRED EY GITTINGER, OTR, FAOTA
Temporary prostheses for lower-limb amputees have been used for many years. We have, on occasion, worked with a prosthetist and made temporary upper-limb prostheses. Training prostheses have been developed at such places as Northwestern and New York Universities, and have been marketed through various catalogues.
The hook and ladder is a simple, inexpensive, temporary device, which can be fabricated easily. The design was developed by a patient to give him a functional device while he was waiting for a permanent prosthesis. It can be worn comfortably for several hours, thus helping the new amputee to remain a two-handed individual during convalescence. It also provides a measure of protection to the trauma site. Although there has not yet been occasion to do so, the hook and ladder can be adapted easily for children.
The device is made from wooden dowels, bolts, and hook and loop fastener, all readily available. Two dowels, 1.6 X 45.7 cm (5/8 X 18 in) are used for the sides, and three bolts, 0.6 x 12.7 cm (1/4 x 5 in) form the cross pieces for a tall adult. Dimensions of the frame members, and distance between the dowels can be adjusted to fit the individual wearer. Bolts are placed 5, 10, and 33 cm (2, 4, and 13 in) from the distal end of the dowels (Fig. 1 ). The proximal ends of the frame members are separated by 11 cm (4 1/4 in). The distal ends are separated by 9.5 cm (31/4 in). The middle bolt, used for additional rigidity, is optional. The separations permit one to wear a coat over the arm. Two fasteners of hook and loop tape hold the device on the forearm and upper arm. The tapes are attached to the frame near the midpoint, and at the proximal end. Figure 2 illustrates placement of a bolt threaded through the distal end of one side, leaving a "hook", which can be used for carrying, or hooking onto objects. The other dowel is slightly shortened. If desired, a screw hook can be added for carrying, pulling, and typing. The protruding end of the cross member can be made useful for hooking, pulling, and carrying by attaching a wide washer and a cap nut.
The frame of the "hook and ladder", combined with the wearer's forearm and upper arm, form a rigid, triangular structure. Flexing the arm against the fasteners tightens the structure and fixes its alignment. The configuration allows the wearer to position the end of the device accurately, so that relatively fine control functions such as typing can be performed routinely.
In addition to good positioning, the hook and ladder transmits a limited variety of motions accurately. Shoulder rotation, flexion, horizontal abduction and adduction, and combined shoulder and elbow flexion and extension can be performed easily. The motions allow the wearer to accomplish many simple tasks. Lifting and carrying objects, particularly those with handles, is easy, either with the hook or with the end of the cross member bolt. Modest pushing and pulling forces also can be transmitted through the device. The horizontal motion and the combined shoulder and elbow motions are useful for positioning many objects. For example, moving an automobile gear shift lever is relatively simple with the hook and ladder. Shoulder rotation is useful for orienting objects that are carried with the device, such as gripping an automobile steering wheel between the distal end of the frame and the middle section of the bolt cross member. The aggressive thread pattern of the bolt affords a remarkably secure grip on a steering wheel.
Hook and ladder has many other uses. It was designed for three tasks, namely: typing; driving, including steering and operating a gear shift lever; and carrying items with handles (Fig. 3 ). Users perform these tasks very well. Complicated and strenuous tasks, such as raking and shovelling, can also be done (Fig. 4 ). The only limit to the activities that can be performed with the hook and ladder is the user's imagination. Even a stationary rowing machine has been operated with it.
The hook and ladder is useful not only to amputees,, but also as a training device for occupational therapists. It can be worn comfortably by people with complete limbs. With it, they can imitate the pushing, pulling, lifting, rotating, and positioning maneuvers used by individuals with upper-limb amputation. With the hook and ladder, therapists can discover how amputees overcome difficulties associated with learning new motions that prostheses require to perform common tasks. The therapist can experience the frustration of having to think about the mechanics of motions during simple tasks that most people perform unconsciously. The hook and ladder lets the therapist appreciate some of the uses and limitations of upper-limb prostheses.
The hook and ladder can thus benefit both the therapist and the amputee.
Sunnyview Hospital and Rehabilitation Center, 1270 Belmont Avenue, Schenectady, NY 12308