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The Use of Preparatory/Evaluation/Training Prostheses in Developing Evidenced-Based Practice in Upper Limb Prosthetics

Brenner, Carl D. CPO; Brenner, Joseph K. CP

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JPO Journal of Prosthetics and Orthotics: July 2008 - Volume 20 - Issue 3 - p 70-82
doi: 10.1097/JPO.0b013e31817c59fb
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As the use of evidence-based medicine and the results of outcome studies become increasingly relied upon in developing utilization guidelines for the provision of healthcare, the field of upper limb prosthetics may find it difficult to meet the demands for objective, comprehensive databases, which can produce statistically relevant information to support the utilization of upper limb prostheses. The most common constraint to such an effort is the limited number of upper limb prostheses that are fitted in comparison with lower limb prostheses. Some of the latest estimates indicate that only one upper limb prosthesis is fitted for every 30 lower limb prostheses.1 With third party payers increasingly turning to peer-reviewed and published outcome results to justify reimbursement, it would be useful to develop an alternate approach to produce objective documentation of clinical outcomes.

The routine use of temporary prostheses, as a method of capturing case-specific clinical data to support a prosthetic treatment plan, has proven to be an effective approach to providing credible rationale to support a prosthetic prescription recommending sophisticated and expensive prosthetic technology. This article will present three categories of temporary/preparatory prostheses and explore various ways these test prostheses can be used to develop credible and effective case-specific evidence to support a recommended course of prosthetic treatment in the absence of broad-based, peer-reviewed clinical studies.


Evidence-based medicine has been defined by Sackett as “the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients.” Whereas, evidence-based practice has been described as integrating individual clinical expertise with the best available external evidence from formal research studies. However, Sackett et al.2 have also pointed out, that even the best evidence derived from organized research efforts may be inapplicable to or inappropriate for an individual patient.

The criteria for developing parameters of medical care has depended on evidence documented in large databases, which can track the outcomes for a variety of medical treatment protocols on a broad scale. According to some observers, the current development of the evidence-based practice initiative was precipitated by the increasing cost of health care, which could be indirectly traced to the prevalence of “preference-based” practice decisions. These are decisions, described as being, largely influenced by the desires of the individual patient and the style of practice to which the clinical healthcare provider had become accustomed, and not based on objective clinical data.3

The criteria to meet the standards established for large demographic studies presents a major challenge to clinical prosthetists, particularly those who specialize in upper limb prosthetics. Although amputations for lower limbs at the Symes and higher levels number over 65,000 per year, the incidence of upper limb amputations through the wrist and more proximal levels total about 2,000 per year, and are reported to be dropping in frequency.4

Because reliable large-scale studies of upper limb prosthetic outcomes are unlikely to be conducted on a consistent basis, it is still possible to develop prosthetic practice methods in keeping with the intent of evidence-base practice goals. This can be achieved through the application of prosthetic procedures designed to provide case-specific evidence, when formal research results are not readily available. A possible solution may be available in the routine use of temporary prostheses and trial fittings, which can effectively contribute to the development of new evidence-based practice protocols in upper limb prosthetics.

The idea of fitting temporary preparatory/training (P/T) prostheses in lower limb cases can be traced back at least 80 years.5,6 However the application of preparatory/evaluation/training (P/E/T) prostheses in upper limb prosthetics is more recent, dating back approximately 30 years.7 The terms preparatory, evaluation, and training highlight the three essential functions that these temporary prostheses can fill. The preparatory element addresses the issues related to the physiological condition of the patient. Whereas the training aspect focuses on the development of the amputee’s skill in using the prosthesis. The third function, which is generating increased interest, pertains to the use of this trial prosthesis as an evaluation tool in developing objective and quantifiable information, which can be documented in the patient’s clinical file and used as the basis for case-specific, evidence-based practice.


Even in the 21st century, the term “conventional” is still used in many clinics to describe body-powered mechanical upper limb prostheses. The conventional era continued up through the 1970s, until a growing number of externally-powered upper limb components offered improved outcomes. In describing the “armamentarium” of components available during the conventional era, Ford and Lewis8 summarized a list of upper limb prosthetic components available, which totaled 18 different types of designs including six hook and hand terminal devices, two wrist units, six below and above elbow joint systems, three harness control systems and a shoulder joint. Also during the conventional era, Springer9 describes the standard treatment process used in upper limb cases. This process included seven “clear cut steps” which included preperscription examination, prescription, preprosthetic therapy, fabrication of the prosthesis, initial checkout, training, and final checkout.

During this period the choices in components, socket designs, control systems, and suspension methods were very limited when compared with the choices that are available today. The use of temporary or preparatory upper limb prostheses focused primarily on preparing and conditioning the residual limb and training the amputee to use a definitive prosthesis. In many cases, the fabrication of these prostheses involved the direct forming of materials, either plaster or low temperature thermoplastics, directly to the patient’s residual limb and were not designed to provide for easy interchangeability of terminal device, wrist, elbow, or harness components.10


When considered at the most elementary operational level, the normal, fully functional human arm provides at least eight degrees of freedom, including 16 voluntary, independent movements, without counting the individual motions of each separate digit. The ultimate goal of prosthetic intervention is to replace each degree of freedom and separate function that is missing because of an acquired limb loss or congenital limb deficiency. Unlike lower limb prosthetics which can benefit from the effects of gravity and ground reaction forces to enhance involuntary prosthetic function, the upper limb amputee must consciously control each separate function of the upper limb prosthesis. During the conventional era, the ability to replace all 16 functions in cases involving a high level transhumeral, shoulder disarticulation or intrascapular-thoracic amputation were limited by the body-powered components and control systems available at the time.

With the introduction of externally-powered prosthetic components and control systems, the possibility of eventually restoring all eight degrees of freedom to the high level upper limb amputee became a reachable goal. It is in this context, that the benefits of including a hybrid P/E/T prosthesis in the prosthetic treatment plan become evident.


By the late 1970s, the external-power era had begun with the increased commercial availability of externally-powered pediatric and adult upper limb components. A pediatric hand from Sweden and a pediatric elbow from Canada were the first children’s electronic components to be offered. Concurrently, adult and pediatric electronic hands from Germany and a proportionally-controlled adult electronic hand from the United States were also made available to the prosthetic community. The 1970s also saw the development of the first adult myoelectric elbow in the United States.

The early externally-powered components were either switch-controlled or myo-electrically-controlled, and not only provided the possibility of enhanced functional capacity for all levels of upper limb prostheses, but also added significantly to the complexity of the decision making process. At this time, the practical value of using a temporary prosthesis became more apparent, not only for preparation of the residual limb and training of the patient, but also as an evaluation tool to sort out the benefits and limitations of both new and old technology.11


The application of either hybrid or all electronic P/E/T prostheses depends on the availability of a wide variety of electronic components. To meet this need, during the external power era, the formation of electronic limb banks was initiated.

A limb bank is a collection of electronic components representing a cross section of commercially available electronic hardware. Limb banks will include an assortment of externally powered terminal devices, wrist units, elbow systems, shoulder components, and a sampling of all electronic control systems with preamplifiers and programmable microprocessors.

Limb banks are generally organized in three different ways. The most common way is for an individual prosthetic laboratory to accumulate, over a period of time, the necessary components to make up a comprehensive electronic limb bank. A second variation is a components bank that is organized and supported through a hospital or charitable organization. The third type of limb bank is one formed by the various manufacturers of upper limb electronic components, who provide components on a free trial basis for short periods of time or for a modest leasing charge for longer periods. As the costs for increasingly sophisticated componentry rises dramatically, manufacturers are finding it necessary to provide components to clinicians on a trial basis, so that they may be evaluated by the patient before making a decision to include them in the definitive prescription specifications.

Choosing of state-of-the-art electronic components involves a major financial commitment on the part of the payer responsible for reimbursement. Limb bank components are generally leased over a period of time for a modest charge, which defrays the cost of maintaining a limb bank. Generally third parties are willing to reimburse for this modest leasing charge, because it represents a very small portion of the purchase cost and validates the medical necessity to include a component in a definitive prescription.


During the conventional era, not only were the treatment processes and choices of components very limited, but also the design of socket for each level of amputation offered minimal variation. As most patients wore a prosthetic sock with their prosthesis, and all body-powered components required a control/suspension harness, there was very little development of harness-free, self-suspended socket.

It was not until the external power era, that interest in self-suspended socket designs grew in response to the availability of new externally powered terminal devices, which for the first time, allowed the amputee to operate the prosthesis without a control harness.

The external power era saw the development of numerous transradial socket designs, and those applied to transhumeral and shoulder disarticulation levels. The transradial designs included supracondylar suspension, anatomically-contoured socket, floating brim suspension12 (Figure 1), roll-on locking liner suspension and external suction sleeve suspension (Figure 2). At the transhumeral level, the roll-on locking liner13 (Figure 3) and anatomically-contoured14 socket offered new options to the transhumeral amputee, as well as the infraclavicular sockets used for humeral neck and shoulder disarticulation amputations.15

Figure 1.
Figure 1.:
A transparent wrist disarticulation test socket with floating brim suspension and temporary electrodes used for myoelectric site selection.
Figure 2.
Figure 2.:
An electronic P/E/T prosthesis with external supracondylar suction suspension sleeve, removable fitting frame, single site/two function myoelectric control system, and electronic prehensor.
Figure 3.
Figure 3.:
An internal roll-on locking liner with distal shuttle-lock pin and integrated snap-on electrodes.

In addition to evaluating components and control systems, P/E/T prostheses play a crucial role in identifying the socket that will provide the most successful outcome in the amputee’s prosthetic rehabilitation.

To provide the patient with the opportunity to try a variety of socket systems, with different load-bearing and suspension characteristics, it is necessary to custom fabricate each separate socket. This obviously involves considerably more time and effort than exchanging the other components that make up a P/E/T prosthesis.

However, it is not necessary to fit a P/E/T prosthesis for each type of socket being initially evaluated. The more practical approach is to build transparent diagnostic test sockets according to the specific design parameters of the sockets chosen to be evaluated. The patient is then fitted with each of the individual designs that are weighted to approximate the number of grams that the completed prosthesis would weigh. After the amputee has tried different weighted test sockets (Figure 4) the selection is usually reduced to one or two. These can be incorporated into a separate P/E/T prosthesis, along with other components that the clinic team and patient may wish to evaluate.

Figure 4.
Figure 4.:
A weighted, transparent wrist disarticulation test socket with external subcondylar suction suspension sleeve to simulate the load-bearing effect of the completed prosthesis.

When considering all the separate elements of a state-of-the-art prosthesis, the general consensus is that the most important element in any prosthesis is the fit of the socket. In addition to providing comfort, stability and suspension, it is the primary platform that serves as a foundation from which all the other components must operate. If the socket does not fit, the prosthesis will fail to meet any of the needs of the patient.


The body-powered P/E/T prosthesis is particularly beneficial to the new amputee, in its preparatory role, because of its effectiveness in controlling edema, protecting the residual limb and reducing the patient’s pain and anxiety, in addition to conditioning the tissues in the residual limb to tolerate the forces exerted by the socket during active use of the prosthesis. Also, the new amputee benefits from the early initiation of occupational therapy training in the activities of daily living (ADL), which promotes independence and an improved psychological outlook. The body-powered mechanical P/E/T prosthesis is ideally fitted to the patient after the sutures have been removed, generally about 14 days after amputation.16

However, experienced amputees, who are being refitted for an upper limb prosthesis, can also benefit from the use of a P/E/T prosthesis. Although seasoned amputees generally do not have to deal with problems of edema or residual limb sensitivity, they can pursue an improved functional outcome by taking advantage of the second function, evaluation, of the P/E/T prosthesis. This allows the patient to try both voluntary opening and voluntary closing hook and hand terminal devices, standard friction wrists along with multifunction, locking and quick disconnect wrist units, and different suspension/control harness systems including the figure-of-nine, figure-of-eight, shoulder saddle, and triple control harness designs.

The third use of the P/E/T prosthesis involves its capacity as a training instrument for both new and old patients. In new patients, it provides the opportunity to commence training as soon as the temporary prosthesis has been fitted. The goals of training new patients are to preserve two-handed function and restore their independence in accomplishing the ADL. An additional benefit of training with the P/E/T prosthesis, for both new and old-time amputees, is to give them the time to become familiar with the unique characteristics of each combination of components. This facilitates the decision-making process, which will determine the final prescription specifications for a definitive prosthesis.


The ability to combine both body-powered and externally-powered components and control systems, affords clinical prosthetists a genuine chance to reproduce each degree of freedom that is in need of replacement. The P/E/T hybrid prosthesis, with its interchangeable modular design, makes it very easy for the clinic team and the patient to try out a large variety of socket designs, suspension systems, combined body-powered/externally-powered control systems, along with an ever-growing assortment of terminal devices, wrist units, elbow systems, and shoulder-locking components.

Although each patient can present unique challenges for both the clinical prosthetist and the technical staff, it is reasonable to assume that each level of amputation involves similar losses in functional movements. For example, the wrist disarticulation level would ordinarily be missing three degrees of freedom: a) open/close of the terminal device, b) flexion/extension of the wrist, and c) ulnar and radial deviation. In cases of transradial amputation, the losses would include a, b, and c, in addition to a fourth degree of freedom, pronation and supination of the forearm. Although pronation and supination can be preserved, to some degree, in an uncomplicated wrist disarticulation amputation, usually only 50% of the full range of forearm rotation is expected to be functionally available. However, if the patient has sustained other injuries in addition to the wrist disarticulation amputation, additional degrees of freedom may have been lost and their prosthetic restoration could depend on multiple P/E/T procedures to achieve the best functional outcome. The following case study provides an example of an atypical wrist disarticulation fitting.


Patient A is a 58-year-old retired man, who was in a motorcycle accident and sustained a brachial plexus injury to his dominant right arm, which left him with a functional shoulder but a nonfunctional elbow, wrist, and hand. Numerous surgeries were performed involving muscle transplants and nerve grafts to provide active elbow flexion. This resulted in the patient’s ability to flex the elbow to 90° (Figure 5), but only having a live lift capacity of 4 pounds and the inability to hold that position for more than a minute. The patient was initially seen for a preoperative consultation/evaluation to explore his prosthetic options, because he was considering having an elective amputation of his insensate and flail right hand. The patient’s primary objective was to restore as much function as possible, so that he could return to his favorite activities; fishing and boating on the Great Lakes.

Figure 5.
Figure 5.:
Patient A demonstrating his elbow flexion capacity after nerve grafting and muscle transplant surgery.

Following wrist disarticulation surgery, he was fitted a P/E/T hybrid prosthesis consisting of a transparent thermoplastic wrist disarticulation socket, interchangeable wrist unit to accommodate both body-powered and externally powered terminal devices, elbow disarticulation-style external elbow joints with a medially placed locking mechanism, a rigid reinforced humeral cuff and a figure-of-eight harness. The figure-of-eight harness was a standard design to provide suspension, elbow lock control and terminal device control, both for a body powered #7 hook and mechanical hand, and an externally powered switch-controlled electronic hand and prehensor. After trying the switch-controlled system for about a month, the patient was given the opportunity to try an electronic linear actuator, which provided proportional control of the electronic hand and prehensor (Figure 6). He found this much easier to control and eventually it became part of the definitive prescription specifications. He also decided that he did not need either a body-powered or an externally powered hand (Figure 7) and requested that the final specifications include only the #7 hook and electronic greifer.

Figure 6.
Figure 6.:
Patient A wearing a wrist disarticulation P/E/T hybrid prosthesis with interchangeable body-powered hook and proportionally-controlled electronic hand and prehensor.
Figure 7.
Figure 7.:
Patient A demonstrating proportionally-controlled electronic hand.

After several weeks of wearing the P/E/T hybrid prosthesis, it was determined, that the elbow lock system on the elbow disarticulation outside joint would not operate consistently, because of the weight of the electronic hand or hook. This required the patient to manually reach over with his sound side arm to lock and unlock the elbow. In addition, he found it difficult to flex the elbow up to more than 90° by using the standard shoulder movements of glenohumeral flexion and scapular abduction, unless the harness was tightened beyond the patient’s comfort level. Eventually he found the easiest and fastest way to position the elbow and operate the elbow lock was by placing the forearm on a tabletop or other fixed structure to preposition the elbow, which left the sound side arm free to operate the elbow lock cable (Figure 8). Based on this, it was decided that placing the outside locking joint on the lateral side and in an inverted position (Figure 9) would allow the elbow lock cable to be positioned distally and allow him to simultaneously position the elbow and also operate the elbow lock. This feature was incorporated into the definitive prosthesis (Figure 10).

Figure 8.
Figure 8.:
Patient A using table top to position the forearm and operating the medially placed elbow lock with his contralateral hand.
Figure 9.
Figure 9.:
The internal socket for a definitive hybrid wrist disarticulation prosthesis with inverted outside joints and laterally-placed locking mechanism.
Figure 10.
Figure 10.:
Patient A demonstrating simultaneous forearm positioning and locking of the elbow joint using his contralateral arm.


As the third variation of the P/E/T prosthesis, the all-electronic P/E/T system is used in those cases where both a body-powered and hybrid system have failed to completely meet the prosthetic needs of the patient. It is also fitted as the second P/E/T system in wrist disarticulation and transradial cases where a hybrid test prosthesis is seldom indicated. The P/E/T electronic prosthesis is best used in those situations where an externally powered elbow would restore function not available with a body-powered system.

It is common practice today, that when fitting a definitive electronic prosthesis, a trial fitting of the socket and components is frequently done to insure that the patient can operate all the various electronic components and is comfortable wearing the prosthesis. This initial step in the definitive fitting process usually provides time for the patient to actually return home with the trial prosthesis to evaluate it.

The trial prosthesis and a P/E/T electronic prosthesis share many similarities. Among these are 1) each one is fitted with the same care as a definitive prosthesis to duplicate the exact experience the patient will go through in the definitive system. 2) With the exception of the socket, the remaining components are fabricated or assembled in a temporary and modular fashion to facilitate changes to any of the elements that make up the prosthesis. The third similarity is that both systems are intended for temporary use and will eventually be replaced by a definitive prosthesis.

However, when considering the intent of a trial fitting compared with the purpose of a P/E/T prosthesis, differences become apparent. The trial prosthesis is not used as an investigative tool in the same way that a P/E/T prosthesis is, because the trial fitting is carried out at the end of the decision-making process, to ensure the likelihood of a successful outcome.

The P/E/T prosthesis is used at the beginning of the decision-making process and proceeds in incremental steps, starting with the most basic approaches to prosthetic care, and with each successive phase, increases the complexity of prosthetic options to be tested by the patient and clinic team, to establish the most appropriate, evidenced-based definitive prescription specifications.


Patient B is a 22-year-old man, who had an industrial accident at a steel fabricating plant, resulting in the reattachment of his left hand. He was initially seen 7 months postinjury for a preoperative consultation/evaluation to consider the prosthetic alternatives and whether he should elect to have transradial amputation surgery. After six reconstruction surgeries, he presented with a painful, nonfunctional left hand and nonunions of both the ulna and radius at the middle third of the forearm.

Following his left transradial amputation, he was fitted with three different types of weighted test sockets; a suction socket with external humeral suspension sleeve, a roll-on locking liner, and a supracondylar solid brim design with an olecranon cutout. He immediately rejected the suction socket because of the confinement of the external suspension sleeve, and selected the roll-on liner with locking socket as his initial choice to be included in the first P/E/T prosthesis.

He wore the first P/E/T prosthesis for 2 months. It included a roll-on locking liner with integrated stainless steel electrodes, and a snap-on wire harness for myoelectric control of the electronic hand and prehensor (Figure 11). After wearing the weighted supracondylar diagnostic socket for periods of up to five continuous hours over several days, he indicated that it felt more comfortable than the locking liner interface of the P/E/T prosthesis, because it did not get as hot and was much easier to don and doff than the roll-on liner with snap-on electrode cables.

Figure 11.
Figure 11.:
Patient B connecting the snap-on electrodes to the roll-on locking liner of his first transradial P/E/T electronic prosthesis.

He was fitted with a second P/E/T prosthesis, 6 months postamputation, which included a supracondylar solid brim socket with an olecranon cutout, and a two site/four function myoelectric control system for the electronic hand, greifer and wrist rotator (Figure 12).

Figure 12.
Figure 12.:
Patient B wearing his second transradial P/E/T electronic prosthesis including supracondylar socket with olecranon cutout, two site/four function myoelectric system for control of the electronic hand, hook, and wrist rotator.

After 1 month of wearing the second P/E/T prosthesis on a full time basis, he developed a bone spur and painful neuroma, which required revision surgery. He had also determined that wearing the supracondylar socket, with the added weight of the electronic wrist rotator and reduced elbow movement, was not as comfortable as the previous locking liner suspension. He returned 6 months later, after having revision surgery, to be fitted with a definitive prosthesis. Based on his experience with the two P/E/T prostheses, his final choice was to eliminate the wrist rotator and four function control and return to the roll-on locking liner interface.


Patient C is a 47-year-old woman with a transhumeral amputation, secondary to Buerger’s Disease. She was first seen 2 years postamputation and presented with a very short transhumeral residual limb, comprised of almost 50% redundant tissue and no defined axilla (Figure 13). Although the humeral segment had full range of motion and good strength, functionally, it was equivalent to a shoulder disarticulation.

Figure 13.
Figure 13.:
Patient C presenting a very short transhumeral residual limb with 50% redundant tissue.

It was anticipated that, her being limited by one-handed function for the past 2 years and never having worn a prosthesis, would generate questions by the medical review panel of her health plan, regarding her motivation and capacity to wear and use a high level prosthesis. However, her favorite pastime was crocheting and knitting for friends and family, which she hoped a prosthesis would allow her to do again. She also generated good electromyographic signals for a two site/two function myoelectric control with the anterior pectoral muscles and upper trapezius sites. Based on this, it was decided to proceed with a P/E/T hybrid prosthesis to identify case-specific, clinical evidence to support or deny the need to fit her with a definitive prosthesis.

Her first P/E/T prosthesis included a shoulder disarticulation socket, body-powered internal locking elbow, forearm lift assist, excursion amplifier, two site/two function myoelectric hand, chest strap suspension, and figure-of-nine control harness (Figure 14). With this initial temporary prosthesis, she demonstrated good control of the myoelectric hand, but could not independently lock/unlock the elbow joint or flex the elbow above 55°, even with the excursion amplifier and figure-of-nine harness (Figure 15).

Figure 14.
Figure 14.:
Patient C wearing a shoulder disarticulation P/E/T hybrid prosthesis including body-powered internal locking elbow, forearm lift assist, excursion amplifier, two site/two function myoelectric hand, chest strap suspension and figure-of-nine control harness.
Figure 15.
Figure 15.:
Patient C demonstrating limited elbow flexion despite excursion amplifier and forearm lift assist.

To remedy this, a P/E/T electronic prosthesis was fitted consisting of shoulder disarticulation socket, locking shoulder joint, electronic switch-controlled elbow and myoelectric hand and greifer. This second prosthesis provided full control of the elbow and excellent simultaneous function with the electronic terminal devices (Figure 16). After 2 weeks, the patient’s occupational therapist reported that patient C had started crocheting during her occupational therapy sessions, and was making good progress overall. Three months after fitting the P/E/T electronic prosthesis, it was determined that the locking shoulder joint was not needed and was replaced with a friction flexion/abduction shoulder joint.

Figure 16.
Figure 16.:
Patient C demonstrates simultaneous control of elbow and hand using her P/E/T electronic prosthesis with locking shoulder joint, electronic switch-controlled elbow and two site/two function myoelectric hand.

The patient continued to wear the P/E/T electronic prosthesis for a total of 8 months, while her health insurance plan reviewed and deliberated over the documentation submitted to them by the patient’s clinic team. The final fitting of her definitive prosthesis occurred 14 months after her initial prosthetic consultation/evaluation. It included the same combination of components as the P/E/T electronic prosthesis, except for the switch-controlled elbow, which was changed to an electronic servo control.


Patient D is a 37-year-old man, who had amputation surgery after a farming accident. He was seen for initial prosthetic consultation/evaluation 3 weeks postamputation. At that time, he presented with a right transhumeral amputation at the distal third level. He demonstrated good strength and range of motion, no pain, a positive attitude and an urgent need to get back to his second job, working on his farm raising feeder cattle. However, his primary occupation, that included working closely with the public as a funeral director, would add to the complexity of meeting his prosthetic needs, which included both functional and cosmetic elements.

At 7 weeks postamputation, he was fitted with a P/E/T body-powered prosthesis, which included an internal locking elbow, forearm lift assist, figure-of-eight harness (Figure 17), 5XA and #7 hook terminal devices, and a voluntary opening hand. During the 5 weeks he wore the P/E/T body-powered system, he experienced three problems. The mechanical voluntary opening hand provided minimal grip force, was difficult to open above 90° of elbow flexion (Figure 18), but opened partially at full elbow extension (Figure 19) and the harness was uncomfortable when tightened enough to optimize terminal device function. The harness was changed to a double-ring configuration (Figure 20) to provide improved terminal device function and comfort. After modifying the harness, the patient demonstrated better terminal device control and reported that the harness was more comfortable, but difficult to don and doff.

Figure 17.
Figure 17.:
The figure-of-eight harness on patient D’s P/E/T body-powered prosthesis.
Figure 18.
Figure 18.:
Patient D demonstrates inability to open voluntary opening body-powered hand at 90° of elbow flexion.
Figure 19.
Figure 19.:
Patient D demonstrates partial opening of body-powered voluntary opening hand with fully extended elbow.
Figure 20.
Figure 20.:
Double ring harness on patient D’s P/E/T body-powered prosthesis.

At 12 weeks postamputation, patient D was fitted with a P/E/T hybrid prosthesis consisting of a suction socket with expulsion valve, internal locking elbow, forearm lift assist, shoulder saddle and chest strap, and a two site/two function myoelectric hand and hook. The patient demonstrated good control of the externally-powered hand and greifer and was pleased with the high grip force, particularly when working on his farm. However, the additional weight of the forearm, with the battery and myoelectric terminal device, made it difficult for him to consistently operate the elbow lock. He reported improved comfort with the chest strap and shoulder saddle, but developed and allergic reaction to the neoprene padding of the shoulder saddle. This subsided when the padding material was changed to expanded polyethylene foam.

A P/E/T electronic prosthesis was fitted to the patient 4 months postamputation. It included the same socket, harness, and myoelectrically-controlled hand and hook used in for the hybrid prosthesis, but the elbow was changed to an electronic switch controlled system. During the 2 months he wore this all electronic P/E/T prosthesis, patient D continued to improve in overall prosthetic function. His only complaint was that the switch elbow was overly sensitive to control and the myoelectric terminal devices operated erratically at times. It was determined that his residual limb was undergoing atrophic changes, and the suction socket was modified accordingly, which allowed him to resume proficient control of the myoelectric terminal device(s).

At 6 months postamputation, the switch-controlled elbow was changed to an electronic servo control for comparison. He reported that this added greatly to improved elbow control and ease of operation. Eleven months after his amputation, patient D was fitted with a definitive transhumeral prosthesis, which included the same combination of components and specifications provided in his last P/E/T electronic prosthesis.


Patient E is a 61-year-old woman, who sustained multiple thoracic injuries, a brachial plexopathy and a transhumeral amputation of her right arm after an automobile accident.

She was initially seen for a prosthetic consultation/evaluation 11 weeks postinjury. She presented with a right transhumeral amputation through the distal one-third of the humerus, which appeared to be longer because of severe subluxation at the shoulder. She admitted to a painful phantom limb with almost constant discomfort. The shoulder was nonfunctional and the posterior and lateral thorax still very painful when palpated.

Her first goal was to be fitted with something lightweight, comfortable and cosmetic, which would allow her to go out in public without attracting unwanted attention. At the same time, she also wanted to have sufficient function to keep up with and care for her grandchildren, including an infant grand daughter who visited on a regular basis, instead of going to daycare.

Following 3 months of physical therapy, the shoulder subluxation had reduced enough to allow the use of an internal locking elbow. Several goals were targeted in fitting the first prosthesis. These were 1) to evaluate the patient’s tolerance to the weigh of a prosthesis, 2) attempt to reduce the shoulder pain caused by the subluxation, 3) determine which components might provide function at a future time, and 4) meet the patient’s cosmetic needs. Her initial P/E/T prosthesis was fitted 5 months postinjury and included a transhumeral socket fitted over a prosthetic sock, shoulder saddle and chest strap harness, internal locking elbow, and passive spring-activated hand. After wearing the prosthesis for 2 weeks, the patient reported that the weight of the prosthesis was not a problem and the shoulder joint felt much better when wearing the prosthesis, which she wore at least 6 hrs a day. She said she also enjoyed walking at the mall without drawing attention.

Having achieved the original goals, the patient was interested in having the prosthesis provide more function. After identifying a good myoelectric signal site over the upper trapezius and knowing that she could tolerate the weight of the first prosthesis, it was decided to proceed with an electronic P/E/T prosthesis. This prosthesis was fitted at 10 months postinjury and included a monolithic transhumeral socket with an integrated shoulder cap to stabilize the shoulder and position the electrodes for myoelectric control (Figure 21), adult size electronic switch-controlled elbow, chest strap with traction switch (Figure 22) and single site/two function myoelectric hand. After 4 months, the patient reported that she was experiencing more pain in her back and on top of her shoulder, and that her contralateral arm hurt when operating the traction switch to position the elbow. It was determined that the rigidity of the monolithic socket was causing additional force to be exerted on the torso, shoulder anatomy, and contralateral axilla. Based on this, a new socket (Figure 23) and custom-molded flexible shoulder saddle with integrated electrodes and wire harness (Figure 24) were fitted. In addition, a rocker switch (Figure 25) was installed to replace the traction switch to control the elbow. These modifications improved the overall comfort of the prosthesis, but the weight of the adult electronic elbow was limiting the patient’s wearing time and eventually the adult elbow was replaced with a lightweight adolescent-size electronic elbow. This significantly improved her comfort and wearing time to the point where, she reported wearing the P/E/T electronic prosthesis as much as her cosmetic prosthesis. Five months after installing the lightweight electronic elbow, patient E was fitted with a definitive prosthesis including the same combination of components and specifications as the her last P/E/T electronic prosthesis, with one exception. Throughout the many months she tried and tested each prosthesis, her thoracic injuries continued to heal, which allowed her resume use of the harness traction switch to control the electronic elbow.

Figure 21.
Figure 21.:
A monolithic transhumeral socket with integrated shoulder cap to position single site/two function electrodes over upper trapezius myoelectric signal site.
Figure 22.
Figure 22.:
Patient E wearing P/E/T electronic prosthesis with monolithic socket and traction switch-controlled adult electronic elbow.
Figure 23.
Figure 23.:
Patient E wearing a transhumeral socket with shoulder saddle suspension.
Figure 24.
Figure 24.:
Custom-molded shoulder saddle with integrated electrodes and wire harness for single site/two function myoelectric control of electronic hand.
Figure 25.
Figure 25.:
Anterior rocker switch to control electronic elbow.


Ordinarily, extending or delaying the time it takes to complete medical care is considered counter productive. In prosthetics, the delivery of a patient’s definitive prosthesis is generally regarded as the completion of prosthetic care, and is often the focus of a treatment plan.

In the practice of upper limb prosthetics, the primary focus is on restoring independent, bimanual function as soon as possible. This centers the issue more on, when the patient can begin prosthetic training, rather than when the definitive prosthesis is delivered.

During the conventional era, prosthetic training could not commence until the patient had received the definitive prosthesis, which in most cases, averaged at least 6 months postamputation.17 Today, current practice recognizes that the application of an immediate or early postoperative prosthesis or P/E/T prosthesis, within the first 30 days postamputation, represents the standard of care.18 This allows a patient to start prosthetic training and pursue independence in ADL within as little as 48 hrs following amputation.

The fitting of one or more P/E/T prostheses will result in adding to the overall amount of time it takes to deliver the definitive prosthesis. However, throughout the entire process of fitting, training and evaluating the patient with up to three variations of the P/E/T prosthesis, it has been observed that many patients undergo a gradual change in their perceptions and expectations.

Immediately after amputation, most patients are focused on the need to restore their body image and so the emphasis is, understandably, on cosmesis. However, they soon realize that the function they have lost is crucial to their daily routine and in most cases supercedes cosmesis as the number one priority. During this time period and throughout this process, the patient also undergoes a change in their expectations. This results from their personal experience with body-powered systems, which provide benefits not duplicated by externally powered components and controls. Body powered systems generally provide more speed and accuracy, and are less sensitive to the environmental conditions where foreign materials and moisture may compromise use and require additional maintenance.

When amputees are fitted with a hybrid P/E/T prosthesis or an all electronic P/E/T system, they are provided with their first opportunity to directly compare the latest externally-powered technology with more basic systems. It is important that the patient be provided with sufficient time to become familiar with the operation and day-to-day experience of using each combination of body-powered and externally-powered components and control systems. As each system is replaced by the next generation or combination, the amputee learns quickly what is most comfortable and “user friendly.” Usually the patient requires at least 1 to 2 weeks with each new configuration to become fully acquainted with the prosthesis and adept in its use. After going through several different types of P/E/T systems, and having tried all the relevant and appropriate componentry, the patient and clinic team are in an excellent position to determine the most appropriate and cost-effective specifications for the definitive prosthetic prescription.

Accordingly, during this entire process every effort should be made to document the progress and setbacks that the amputee undergoes. The information being generated is what constitutes the foundation of case-specific, evidence-based practice. And if possible, the documentation should occur both within the files of the clinical prosthetist and that of the occupational therapist and prescribing physician. The compilation and submission of this information to third party payers, generally ensures that the prescribed course of care being recommended will most likely be regarded as medically necessary and approved for reimbursement.


With improvements in sensor technology, biomaterials using nanotechnology, imbedded chips, artificial intelligent algorithms, and programmable miniature microprocessors ushering in, what could be described, as the biomechatronic era, new methods are needed to discern the most appropriate technology for each individual patient.

The term, biomechatronics has been defined as that which “comprises aspects of biology, mechanics and electronics.”19 With the latest advances in upper limb technology already relying on ideas and methods from the fields of biomechanical engineering, biomedical engineering, electrical engineering, mechanical engineering, computer science, and others, it is reasonable to assume the we are already practicing in a biomechatronic world.

As the close of the first decade of the 21st century approaches, the field of upper limb prosthetics continues to undergo a combination of tremendous changes and challenges. These changes include a diminishing number of upper limb amputations and congenital limb deficiencies, increased resistance on the part of third party payers to underwrite the costs associated with providing state-of-the-art upper limb prosthetic care, and the challenge of keeping up with accelerating advances in technology, which provide more and better choices to improve the rehabilitation of the upper limb amputee.

When considering all the issues needing attention, the effective use of P/E/T prostheses has already proven to be a very practical way to address the various changes and challenges being dealt with today. The concept and application of the P/E/T prosthesis, as used in the three different configurations presented here, may also provide at least some answers to the, yet to be discovered, clinical, technical, administrative, economic, and ethical complexities of the biomechatronic era.


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preparatory evaluation training prosthesis; preparatory prosthesis; temporary prosthesis; trial fitting; test prosthesis; diagnostic prosthesis

© 2008 American Academy of Orthotists & Prosthetists