Chapter 29 - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles
Critical Choices: The Art of Prosthesis Prescription
John H. Bowker, M.D.
The prescription of a prosthesis no longer involves simply matching a particular level of residual limb with a prosthesis designed for that level. There are so many choices, in fact, that prescription becomes as much of an art as a science. This multiplication of options has resulted from a revolution in prosthetic design, manufacture, and fitting due to the introduction of new concepts in socket design as well as a wider array of components and new materials, including heat-mold-able plastics, lightweight metals, and carbon fiber-reinforced plastics.
Before discussing factors involved in prescription, it is useful to review the reasons for not prescribing a prosthesis. If the patient's overall health has irrevocably deteriorated to the point where he is unable to provide the strength or coordination to utilize the prosthesis, it is useless to prescribe one. The mental status of the patient must be such that he can learn its use and limitations. At the highest levels of amputation in both the upper and lower limbs, useful function decreases directly in relation to progressive loss of limb length. In addition, in lower-limb amputation, energy requirements for ambulation increase sharply with each more proximal anatomic level (see Chapter 15).
A large number of factors affect the prescription, not all of which readily come to mind until one examines all the parameters of a given patients life. First and foremost, the prosthesis should meet the needs and desires of the patient, both vocationally and avocationally, insofar as possible. Prosthetic services should be readily available, not only for the provision of the initial prosthesis but also for its maintenance, repair, and replacement at suitable intervals.
Since prostheses vary considerably in their complexity, the limb-fitting team should determine the tolerance of the amputee both for the various levels of prosthetic complexity available and the care with which different types of prostheses must be treated. Geographic remoteness without ready access to a prosthe-tist for maintenance, repair, and replacement of a limb may dictate simplicity of design related to the need for self-repair of the device. Climate can also play an important role. In areas of excessive humidity, metal parts will tend to corrode and wood to rot. In areas of extreme aridity such as the desert regions of the world, fine sand particles will quickly wear out the joints of prostheses because of their close tolerances.
The cost of a given prosthesis, both initial and ongoing, can be a limiting factor in determining the prescription. For example, some insurance companies will provide only one prosthesis for the life of the patient. Fiscal limitations at the local and state levels may mandate only a very simple prosthesis for indigent amputees, similar to those prescribed for amputees in the developing world. Local custom and knowledge are also powerful forces in determining prosthetic prescription in that they tend to limit the prescription options considered.
The prescription of the most suitable prosthesis, taking into account the above factors, is most effectively done by a team. The team should consist of the patient/ family, the amputation surgeon, the prosthetist who will be making the limb, the therapist who will be providing the training in its use, a psychologist and/or social worker who will help the patient through his period of adjustment, and the insurance nurse, especially in workmen's compensation cases. There is a widely held misconception that this sort of team is available only in large medical centers. On the contrary, a very effective miniteam can be assembled in most small to medium-sized cities. It takes only an interested surgeon, the local prosthetist, a therapist, a psychologist/social worker, an insurance nurse, and amputees. If the surgeon expresses an interest in this work, other local surgeons are very likely to refer patients for this purpose. By meeting once or twice a month at the physician's office or other designated location, team members can work far more effectively than by individually seeing the patient in isolation with no cross-fertilization of ideas. This approach also helps to upgrade prescription practices and tends to move the participants into a position of leadership in this field.
While it is obvious that an amputation affects the amputee for the rest of his life, the need for regular lifelong prosthetic preventive maintenance is often forgotten. Even though there may be frequent follow-up visits immediately after the fitting is carried out, the amputee still needs to be seen at 6- to 12-month intervals for the rest of his life. Not only do residual limbs change in volume with muscle atrophy and weight gain or loss, prostheses also require maintenance, repair, and periodic replacement. Replacement may also be indicated as improved designs appear from time to time.
SPECIFIC FACTORS RELATED TO LOWER-LIMB PROSTHETIC PRESCRIPTION
The basic reasons for fitting a lower-limb prosthesis are to enhance ambulation by decreasing the excess energy requirements of crutch walking and improving the patients balance with restoration of bilateral proprioceptive feedback through the residual limb-prosthesis interface. Very importantly, the hands are freed for activities other than handling a walker or crutches. In short, the goal is to restore as much functional capacity to the lower-limb amputee as possible. This will vary widely from returning him to all activities that he had previously engaged in, including active sports, to the minimum acceptable rehabilitation goal of assisted transfer activities that aid the care-giver as much or more than the amputee. The other benefit to any amputee is the cosmetic restoration provided by the prosthesis.
There are also cogent reasons for not fitting lower-limb prostheses. The fitting of bilateral dysvascular transfemoral amputees with articulated prostheses, for example, is rarely successful. These devices, in addition to being expensive and extremely difficult to walk with, are quite uncomfortable to sit in for prolonged periods. These patients find transfers much easier without the impediment of these almost nonfunctional prostheses. If the patient requests some form of cosmetic restoration, however, lightweight cosmetic prostheses can be provided, or a pair of panty hose can be filled with properly sculpted foam to give a pleasing appearance with slacks or skirt and shoes.
If these patients insist on some form of household ambulation and can demonstrate sufficient cardiac reserve clinically, they may be given a trial on stubbies. These are basic nonarticulated transfemoral sockets with rocker bottoms and appropriate suspension (Fig 29-1.). Young traumatic bilateral transfemoral amputees, on the other hand, will almost always demand a trial of ambulation but should also start with stubbies. After a variable period of training, during which they are able to assess the energy costs of such walking and the team evaluates their motivation, they may be given articulated limbs. Eventually, however, most abandon these prostheses for a wheelchair because of its greater efficiency in speed and energy consumption. Even the unilateral dysvascular transfemoral amputee may not be able to muster the cardiopulmonary reserve to manage mere household ambulation and will prefer a wheelchair.
At the hip disarticulation or transpelvic levels, the amputee, typically a younger trauma or tumor patient, often becomes a long-term community ambulator. Some, however, may find that the decreased speed of prosthetic walking is the overriding factor in rejecting prosthesis usage for most occasions. If these high-level amputees require two external aids such as canes for prosthesis use, there is little, if any, functional advantage over crutch walking without a prosthesis.
Patients should not be rejected for fitting of unilateral or bilateral lower-limb prostheses solely on the basis of age. Many very elderly patients can be successfully fitted at the transtibial or Syme ankle disarticulation levels provided that they are physiologically sound and have sufficient mental capacity to comprehend the subtleties of sock adjustment for changes in residual-limb volume (Fig 29-2.). In borderline cases, lower-limb transtibial amputees should be fitted with inexpensive preparatory prostheses to realistically assess their potential for ambulation.
Delaying prosthetic fitting and training of the unilateral dysvascular amputee in order to prevent stress to the remaining foot is not recommended. This approach will result in months of avoidable deconditioning and tend to inure the patient to alternative modes of mobility. If the second foot is then amputated, simultaneous fitting as a bilateral amputee is far less likely to produce useful walking than if the patient had been fitted as promptly as possible after each of the separate operations. The dysvascular amputee who loses one foot should therefore be made ambulatory with a prosthesis as rapidly as possible. If and when the second foot is lost, the patient will then be accomplished as a unilateral prosthesis user and have a better chance of success in learning to use a prosthesis on the second side.
Many younger lower-limb amputees, especially at the transtibial level, will wish to participate again in their previous sports activities. If the amputee is interested in returning to any sport based on running, there is a variety of dynamic-response feet available for him to try since many of them can be easily interchanged at the ankle level. On the other hand, some amputees will benefit from prostheses specifically designed for given sports. These would include prostheses specifically made for skiing and swimming activities (see Chapter 24B). Because of these complexities, effective management is best achieved by a team as described above.
Additional factors that may enter into the fitting of lower-limb amputees, especially in diabetes mellitus, are blindness and hemiplegia. Once properly trained, a blind unilateral or bilateral Syme ankle disarticulate or transtibial amputee should be able to walk about in familiar surroundings but may be safer with a companion for community ambulation. The fitting of blind unilateral or bilateral transfemoral amputees should be approached with caution because of the loss of proprioceptive knee function. Patients with hemiparesis following a cerebrovascular accident can often walk with their transtibial prostheses provided that they have adequate mentation and balance and no disruptive spasticity or severe extensor or flexor patterning.
SPECIFIC FACTORS RELATED TO UPPER-LIMB PROSTHETIC PRESCRIPTION
The key to successful fitting of the upper-limb amputee is largely based on the amputees motivation. It should also be remembered that prosthetic fitting is entirely optional at the discretion of the amputee, although most bilateral upper-limb amputees find that prostheses enhance their function. The motivation of the unilateral amputee for prosthetic fitting is usually highest immediately after amputation, before one-handedness develops. In fact, successful fitting of the unilateral upper-limb amputee is unusual after the amputee has become fully functional with one hand.
It is very useful, therefore, to fit an immediate postoperative prosthesis (IPOP) whenever possible to provide a prehensile tool to assist the intact hand and prevent the development of complete one-handedness (Fig 29-3.). Behaviorists should be enlisted in an early stage to assist the amputee in starting to work through the grieving process.
In approaching the upper-limb amputee, it is important to note that there are significant differences in the impact of hand vs. foot loss. Awareness and use of the hand for grasping occur much earlier in infancy than the use of the lower limb for walking. The hand is of greater significance than the foot, both physically and psychologically. It is also important to realize that function and cosmesis of the upper limb are much less completely replaced by a prosthesis than are foot function and cosmesis by a lower-limb prosthesis. Because of these factors, prosthetic services can best be provided by a specific upper-limb prosthetic team. The team should be both interdisciplinary and interactive, in other words, operating in close conjunction rather than independently. Although the surgeon cannot be expected to carry out the activities of other team members, the amputee expects the surgeon to be fairly knowledgeable in all areas of prosthetic rehabilitation so that he can effectively coordinate the limb-fitting program by synthesizing the findings and recommendations of the team.
The first step in prescription is eliciting the amputee's expectations while realizing that every upper-limb amputee feels that he should receive a prosthesis with a hand and elbow that look real, functions like the hand and elbow that were lost, and is low in cost and easily maintained. It is therefore necessary to give a fairly detailed explanation of what is realistically available. This discussion should include the basic differences between body-powered and myoelectric limbs, as well as the limits of prosthesis function vs. that of the intact upper limb. The complexity of various prostheses must be explained, and the tolerance of the individual amputee for these should be ascertained. Despite the obvious attractions of myoelectric prostheses, the amputee must understand that not only are they very costly initially but they also generally weigh considerably more than the usual body-powered prosthesis designed for that same level. Cosmesis is also of concern, especially to women and to all who must meet the public in their daily work. The older patient who has lost a limb from trauma or tumor at a high level may decide to forego any prosthesis or to use a very light, nonfunctional device so long as it is cosmetically acceptable. The patient should meet as often as is necessary with team members, collectively or individually, to get desired information regarding the prosthesis and use training. The entire team should then meet again with the patient before actually ordering the prosthesis. In high bilateral cases, consideration should be given to modifying the amputee's environment as much as possible for more effective function.
Blindness presents especially difficult problems for the upper-limb amputee since the use of a terminal device is almost entirely dependent on visual control. A blind bilateral upper-limb amputee will have no use for prostheses except perhaps as cosmesis. In this situation, consideration should be given to a Krukenberg procedure on one or both sides (see Chapter 36A). When these modified forearms are not in use, they can be covered with cosmetic prostheses. A blind unilateral upper-limb amputee may find a prosthesis useful for holding a coat or carrying objects in a gross manner.
Questions are often raised, especially by third-party payors, as to what constitutes successful use of a prosthesis for the upper limb. Is it related to a certain number of hours of wear each day? Many amputees will wear a myoelectric or cosmetic device during working hours and remove it at home for reasons of comfort. Nonetheless, it has served an extremely useful purpose at the workplace. Other amputees may wear the more cosmetic device at work and switch to a body-powered prosthesis for working in the garden after hours. Conversely, a manual worker such as a welder may use his body-powered prosthesis at work and switch to a cos-metic/myoelectric prosthesis for social functions. Even part-time use of an upper-limb prosthesis for specific vocational, avocational, or purely social purposes is a sign of acceptance of the prosthesis.
As in the case of lower-limb amputation, many upper-limb amputees will want to return to the sports and recreation activities in which they previously engaged. They have the option of myoelectrically controlled hands or body-powered terminal devices that feature either passive or active prehension. Again, the terminal device for sports and recreational activities should be carefully matched to the patient's needs and desires (see Chapter 12C).
Follow-up with the team, after the initial intensive effort involved in fitting and training has been completed, should be on a lifetime basis, with at least yearly evaluations. Not only do prostheses wear out and sometimes break, but improved designs that might be a real advantage to individual amputees also appear from time to time.
Chapter 29 - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles