Chapter 7B - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles
Partial-Hand Amputations: Prosthetic and Orthotic Management
John W, Michael, M.Ed., C.P.O.
Upper-limb loss can be far more catastrophic to the individual than the more common lower-limb loss. Beas-ley has noted that:
Loss of a hand results in a major restriction of capabilities and the loss of a prime sensory perceptor and imposes a serious disfigurement that can be only incompletely disguised at very best. The loss of both hands creates a handicap that is exceeded only by serious brain or spinal cord injury.
In 1944, Kirk aptly summarized the challenge that partial-hand amputation presents to the prosthetist-or-thotist: "No hand is so badly crippled that, if it is painless, has sensation, and strong prehension, it is [not] far better than any prosthesis. Despite numerous advances in the state of prosthetic art for other levels, treatment for partial-hand amputation has not changed significantly since those words were written. Wedder-burn et al. commented in 1986 that "partial hand amputees are more likely to reject their prostheses than any other upper limb amputee. Rejection stems from lack of tactile sensation, poor appearance, lack of ventilation in the prosthesis, and limited function." As a result, many partial-hand amputees choose to function without a prosthesis.
The dilemma facing physicians and prosthetists is to determine when our admittedly limited prosthetic armamentarium will add a measure of function to diminish the substantial loss faced by the partial-hand amputee. Those who elect to wear a prosthesis do so for specific reasons, and the foundation for successful prosthetic-orthotic design is therefore careful assessment of the amputee's expectations and needs. Although a variety of approaches are possible, the simplest device necessary to meet the identified needs will provide the greatest measure of acceptance and patient satisfaction. Due to the space constraints dictated by the remnant hand, few devices can provide both a cosmetic appearance and strong prehension simultaneously. Thus, it may well be necessary to prescribe more than one device to meet all of the amputee's needs.
One common concern of partial-hand amputees is the disfigurement that an anomalous hand presents. It should be noted that the degree of physical loss is not at all indicative of the degree of emotional loss, which varies according to cultural and personal values. Prescription of a prosthesis to restore the external appearance is common, and such devices are generally well accepted by the amputee. Although it is true that covering the remnant hand with a rubberized glove reduces sensory input and increases perspiration, neither factor is of great consequence for the unilateral amputee. Chapter 7D discusses the aesthetic prosthesis in detail. Such devices are generally provided by highly specialized cosmetic restorationists who sculpt a detailed mirror-image replica of the contralateral hand from which to fabricate the device.
Most prosthetists can also supply a polyvinylchloride (PVC) plastic cosmetic restoration that is fabricated by a specialty company (Realastic) from donor molds of hands that are similar (but not identical to) the patient's hand. Although these latter prostheses are much less expensive than custom-sculpted restorations, they are not as durable nor as well matched in color or contours and are therefore satisfactory only in selected cases (Fig 7B-1.). It should be noted that passive restorations should not be considered to lack function. Most allow a fixed grasp, many provide a source of opposition for mobile hand remnants, and partial-digit extensionsfrequently restore the ability to type, play keyboard instruments, and the like. Prehension is not the only definition of function: persons who hide their disfigured hand in a pocket are as disabled as if the entire arm were ablated.
Another indication for prosthetic use, in addition to restoring a more normal appearance, is to protect hypersensitive or fragile areas. This is frequently necessary during the early postoperative stages while healing is occurring. Preliminary devices are often provided by the occupational therapist and are fabricated from low-temperature plastics that can be easily reshaped as the partial-hand amputation matures (Fig 7B-2.,A). Once recovery is complete and vocational/avocational needs have been established, the patient may be referred to the prosthetist-orthotist for definitive prosthetic fitting (Fig 7B-2.,B).
In some cases, grafted skin or hyperesthesias will require long-term protection by a prosthetic device (Fig 7B-3.). Particularly for the manual laborer, such protective devices may be required to permit a return to gainful employment (Fig 7B-4.).
The final justification for prosthetic-orthotic fitting is to improve prehension. Most congenital deficiencies do not require any assistive devices to augment function because children naturally develop idiosyncratic grasp patterns that maximize the available body function. A mobile, sensate, and prehension-capable limb deficiency will likely be encumbered by a prosthesis that attempts to augment grasp, although some prefer an aesthetic restoration. The one exception is the limb without digits that retains carpal or carpal-metacarpal motion. An orthotic post may improve grasp by providing a platform for the mobile, sensate metacarpal "pad" to oppose. The three-position design developed at the Child Amputee Prosthetics Program (CAPP) is particularly useful (Fig 7B-5.).
Most prosthetic devices used to restore grasp following partial-hand amputation have static configurations. Particularly for use under the rugged conditions of factory work or manual labor, static designs have the advantage of durability. Some are formed from stainless steel, individually shaped to the anomalous hand, and covered with a pink-colored plastic (Plastisol) to increase the friction when gripping objects (Fig 7B-6.). Other devices are made of laminated plastic formed over balsa wood (Fig 7B-7.) or over lightweight aluminum armatures covered with polyurethane foam (Fig 7B-8.). It is also possible to use thermoplastics to form partial-hand devices (Fig 7B-9.). Some amputees choose to retain the simple utensil cuffs provided early in their rehabilitation training because they find this approach adequate for their needs.
The common denominator in all these prostheses is that they must be individualized carefully to perform the specific tasks desired by the amputee. For example, the configuration to permit a landscape worker to handle shovels, rakes, and the like will differ significantly from the contours necessary to permit a chef to use cooking utensils. It is usually helpful to have the amputee bring examples of the objects he wishes to handle with the prosthesis to the initial fitting. This permits the prosthetist to reconfigure the prosthesis to provide as many grasp patterns as possible prior to finishing the device.
Articulated or dynamic devices powered by residual motions at the wrist or palm may also be developed to enhance grasp. Although technically much more difficult to fit than static designs, articulated partial-hand prostheses usually offer a wider range of openings, thereby facilitating grasp of more varied objects (Fig 7B-10.). It is sometimes useful to attach a prosthetic hook mechanism to a hand remnant with no useful residual function (Fig 7B-11.). Body power transmitted from biscapular abduction is generally used to open the device, but wrist motion (Fig 7B-12.) or other body motions may sometimes be used (Fig 7B-13.). It is also possible to utilize a voluntary-closing terminal device (Fig 7B-14.).
It is sometimes possible to combine a wrist-driven orthosis with prosthetic fingers and thumb to result in a somewhat cosmetic hand prosthesis, particularly when covered with a modified cosmetic glove (Fig 7B-15.). This approach has been difficult to replicate due to numerous technical constraints but is worthy of further investigation. Myoelectric control of fingers driven by individual motors is the most advanced technique yet attempted. Researchers at Northwestern University have developed demonstration prototypes (see Chapter 12D), although many barriers must be overcome before such technology can become clinically available.
In summary, partial-hand prostheses are highly individualized devices designed to meet such specific needs as cosmetic appearance, protection of tender areas, and augmentation of active grasp. In traumatic cases, early provision of preparatory devices fabricated from low-temperature plastics by the occupational therapist is believed to maintain two-handed functional patterns and facilitate definitive fitting by the prosthetist. Devices to restore active grasp are best described as "tools" and are most readily accepted for manual tasks or factory occupations. Many amputees prefer one device to provide cosmetic restoration and another for specific tasks where appearance is unimportant. Since every prosthetic device reduces sensory feedback to some degree, many individuals will choose to function without any devices at all.
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Chapter 7B - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles