Most upper limb amputations are of traumatic origin and affect young men.1,2 Amputation decreases their social participation and their quality of life for several years.3–8 Functional prostheses offer a great potential for improving the level of functioning and the social participation among upper limb amputees. In fact, some studies suggest that using a functional prosthesis is linked with better performance in daily activities and with a better potential for returning to work.3,4,9,10 Despite these advantages associated with prostheses, an important rejection rate of active prostheses is found in the literature. A review of the literature assessing prosthesis use since 1980 reported a mean rejection rate of 26% for body-powered prostheses and 23% for myoelectric prostheses in an adult population.11 Factors associated with successful prosthesis use or with rejection are still largely unknown.6
Most amputees experience phantom limb sensation (PLS).8 PLS is defined as “all nonpainful sensations in the amputated part of the arm,”12 including, for example, the perception of the position of the limb, the sensation that something is touching the limb, sensations of warmth or cold, or sensations of movements of the amputated part of the arm.12 Even though PLS sometimes decreases with time, many studies with chronic amputees showed that most of them still feel PLS many years after amputation.8,12–14 In addition to PLS, a large proportion of amputees experience phantom limb pain (PLP), which can be defined as “any of the above-mentioned phantom sensations or any other sensation in the amputated part of the arm which is so intense that it is experienced as painful.”12 In a review, Biddiss and Chau15 combined 13 studies for a total of 729 amputees and obtained a mean prevalence for PLP of 50%.
PLP causes important disabilities to many of those living with it.8 It has been shown that PLP has a negative impact on people's social participation and health-related quality of life.3,5,8,16 Moreover, some studies suggest that pain could be associated with difficulties with the prosthesis and could be a reason for prosthesis abandonment.6,7,17,18 However, the association between prosthesis use and PLP remains unclear because negative,5,19,20 positive,8 or no association4,12–14,21,22 has been found between these two variables in different studies. Moreover, two studies suggest that an intensive use of a functional prosthesis controlled via distal residual limb musculature is associated with lower PLP.19,20 Those studies reported that amputees who use a myoelectric or a Sauerbruch prosthesis experience less PLP and show less cortical reorganization than amputees who do not use this type of prosthesis.19,20 However, some problems have been highlighted with data analysis methods used in Lotze's study which render the strength of this conclusion questionable.12 Furthermore, the design of studies reporting an association between pain and prosthetic use (mainly transversal and correlational) does not allow us to draw conclusions on causal relationships between these variables.
Over the past decade, researchers have proposed innovative prosthesis designs to improve the functionality of their devices. Prosthesis designers try to allow subjects to easily control their prosthesis into complex movements and even to have functional sensations while they use their prosthesis. One frequently used approach consists in integrating the phantom limb into the control of the prosthesis.23–26 A clear knowledge of the interaction existing between prostheses presently used in clinical settings and the user's phantom limb is crucial for the optimization of future prosthesis designs. Moreover, it is essential for clinicians to take into account this knowledge about interaction in prosthetic training.
The main objective of this study is to clarify this interaction, as seen by prosthesis users themselves and by health professionals working with upper limb amputees. Moreover, we also aim to explore the interaction between these factors and the support offered to amputees, which may influence the prosthesis user's success and the patient's coping skills when confronted with PLS and PLP.
METHODS AND PROCEDURES
RESEARCH DESIGN AND SAMPLE CONSTITUTION
Considering the lack of consensus on the interaction existing between prosthesis use and PLSs, an exploratory case study was set up.27 Face-to-face interviews and questionnaires were done with prosthesis users and health professionals working with amputees. The project was approved by the local ethics committee (IRDPQ project no. 2007-111), and all participants gave their written informed consent.
New prosthesis users (within 12 months of prosthesis use) were invited to participate in the project by health professionals working in the rehabilitation center's Amputees and Orthosis-Prosthesis programs. Inclusion criteria were to present an amputation proximal to the wrist and to have received a first body-powered or myoelectric prosthesis in the last 3 months. Recruitment of expert prosthesis users was based on theoretical sampling.28 Participants were selected in order to inform the researcher's developing understanding of the area of investigation. The idea is that the researcher collects data from any individual or any group of people who can provide the appropriate and relevant data for the generation of his or her theory.28 Expert prosthesis users were invited to participate in the project via the rehabilitation center archives by means of a list of patients previously prepared by health professionals working in these two programs. Inclusion criteria for this group were to have an amputation proximal to the wrist and to have been using a prosthesis for 2 to 5 years. Health professionals from the Amputees and Orthosis-Prosthesis programs were also recruited by researchers. Inclusion criteria for health professionals were to be working with upper limb amputees and to have been doing so for the past 3 years.
Prosthesis users participated in a meeting lasting approximately 75 minutes. They completed two questionnaires (PLSs and satisfaction with prosthesis) and participated in a semistructured one-on-one interview. Health professionals also completed a similar interview and a sociodemographic questionnaire during a meeting lasting approximately 60 minutes. More specifically, the following tools were used.
Quebec User Evaluation of Satisfaction With Assistive Technology Questionnaire
The French version of the Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST29) was used to assess the degree to which users were satisfied with their prosthesis. The first part of the QUEST provides information about the participant, as well as about his or her prosthesis and environment, in other words, personal and environmental factors. The second section of the QUEST reveals the importance that the participants attribute to each of the evaluated variables and rates their degree of satisfaction with each of the variables considered. It is also possible to gather sources of information concerning nonsatisfaction.
Groningen Questionnaire Problems After Arm Amputation
Parts of a French version of Groningen questionnaire were used to assess different types of sensations experienced by users since their amputation.12 It includes questions about the frequency of PLS, PLP, and stump pain (SP) and about the treatment received for PLP. In the questionnaire, PLS and PLP are defined as in the introduction of the present article. SP is defined as any painful sensation in the residual limb.
The interviewer guide contained three general questions linked to the project's objectives: How does wearing and using the prosthesis influence PLSs? How do PLSs help or interfere with the use of the prosthesis? and How are PLSs taken into account in rehabilitation and prosthetic fitting processes? All participants were asked to answer these questions to the best of their experience while specifying to them that there were no good or bad answers. The interviews were recorded. They were performed by a research assistant with experience in interviewing people living with disabilities. The interviewer guide was pretested with two health professionals by the research assistant. Two questions were reformulated to improve understanding.
In accordance with the thematic analysis approach of Braun and Clarke,30 the analysis process involved several steps: familiarization with the data, generation of the initial codes, identification of the themes leading to classification of the interview contents, review and definition of the themes, categorization and classification of the interview statements, and production of the report. The 16 interviews were transcribed verbatim, for a total of about 180 pages. The N′Vivo software was used to code the interview contents. All the verbatim transcription of the interview contents was coded under three main themes: “Influence of prosthesis use on PLS/PLP,” “Influence of PLS/PLP on prosthesis use,” and “Rehabilitation process and PLS/PLP.” Afterward, each theme was synthesized, and the slight differences in participant perception were highlighted. Excerpts from the verbatim have been presented to illustrate these differences. We next explained the possible implication of these data using concepts and data found in the literature. For the questionnaires, data were compiled in a database using Microsoft Office Excel software, and descriptive statistics were produced. Percentages were computed for nominal data and mean ± 1 SD for ordinal and continuous data. For the QUEST, main satisfaction of patients with the technical aspects of the prosthesis and with the services received were computed (mean ± 1 SD).
Data obtained from new prosthesis users (n = 3) were similar to data obtained from expert prosthesis users (n = 9); the two groups were therefore treated together. Twelve prosthesis users participated in the study. Their sociodemographic and clinical characteristics are presented in Table 1. All of them sustained a traumatic upper limb amputation. For the majority, amputation involved the dominant hand (67%) and was transradial (92%). The mean time since amputation was 20.0 ± 16.8 years.
All prosthesis users but one reported experiencing PLSs and most of them (75%) expressed being able to voluntarily move their phantom limb. More than half of the users (58%) reported the presence of phantom pain at variable frequencies. One-third of the users said that they were experiencing residual limb pain at the time of the study. One-third of the users stated that they received treatments for PLP and half of them perceived these treatments as effective.
The prosthesis use and the user degree of satisfaction with the prosthesis are summarized in Table 2. All users but one had body-powered prostheses, and one-third of users had myoelectric prostheses (some using both types of prostheses). More than 75% of the users reported wearing their prosthesis for more than 6 h/d, and they were generally satisfied with it. One user reported abandonment of his myoelectric prosthesis because it was too fragile for his needs. However, he continued to use his body-powered prosthesis.
Health professional characteristics are presented in Table 3. Three are prosthetists and one is an occupational therapist. They all work in an amputee program within a rehabilitation center.
How Does Wearing and Using a Prosthesis Influence Phantom Limb Sensations?
Many patients reported that wearing their prosthesis does not influence PLS. However, four patients reported that using the prosthesis to perform daily activities (especially significant activities) alleviates PLP:
“PLP does not change, except that when I wear my prosthesis and I work on machinery, on tractors, I think about what I'm doing and less about it [PLP]. When I sit, in the evening, it is more painful. When I'm not active, it is more painful. So it has to be drowned in something, in work.” [Patient 9–43 years of experience]
In contrast, four users reported that PLP seems to increase when they use their prosthesis many hours in a day as illustrated in the next extract:
“However, since I've been wearing my prosthesis more, since I returned to work|PO because I'm back to work four-five days per week. I wear my prosthesis more and the phantom limb pain came back more. […] Today I brought my prosthesis with me, but I did not wear it. I still have phantom limb pain, but it is less intense than when I wear it.” [Patient 4–9 months of experience]
Some patients also mentioned that the prosthesis can stimulate some areas of the residual limb which increases PLP. One patient using a myoelectric prosthesis reported an increase of his phantom limb awareness since he uses this prosthesis:
“Before with the other [body-powered prosthesis], the one in which the stump is passive, I could clench my [phantom] fist or do things like that unconsciously. However, with this one [myoelectric prosthesis] I couldn't do this because there is an associated movement, an external movement associated with it. But physically I am more aware of my [phantom] hand, of the muscles in my hand that are in the stump because they have to be active during the day, in a concrete manner.” [Patient 1–11 years and 5 months of experience]
He and a body-powered prosthesis user also reported sometimes trying to produce movements with their prosthesis while they were not wearing it. Despite these anecdotes, no patients reported a persistent change in their PLS since the acquisition of their prosthesis.
There were many inconsistencies about the interaction between prosthesis use and PLS in the interviews. On one hand, some sensations are influenced differently by prosthesis use from one subject to another. For instance, three patients said that prosthesis wearing diminishes sensations of cold while one said that it increases them. On the other hand, two of these patients had previously reported that prosthesis wearing does not influence their PLS which illustrates a within-subject discrepancy.
Three health professionals consider that wearing a prosthesis often alleviates PLP because it brings new sensations to the residual limb:
“… in many cases, it looks like prosthesis wearing, the fact of having an object which stimulates other things, has an effect on pain decrease, on phantom limb sensations. Then in the case of phantom limb sensations, they tend to talk less about it.” [Health professional #3]
The other professional reported that the prosthesis allows patients to engage in significant activities that often direct their attention away from their PLP. She also suggested that the prosthesis may have a normalizing effect by allowing patients to use their amputated limb which could contribute to decreasing PLP. However, three health professionals also said that the prosthesis can increase PLP when it is poorly adjusted, when it stimulates a trigger point, or when it is too heavy. Moreover, one of them reported, as did the patients, that after wearing the prosthesis for many hours, PLP seems to increase. Another said that sometimes while patients wear their prosthesis, they consider that the position of their phantom limb “improves,” i.e., that the hand feels “in the right place” when wearing the prosthesis.
How do Phantom Limb Sensations Help or Interfere With Prosthesis Use?
Most of the patients reported that their PLS does not influence the use of their body-powered prosthesis. Most consider that because their body-powered prosthesis is controlled with proximal movements, they cannot see how PLS could be involved, as expressed in the following excerpt:
“To open the body-powered prosthesis, I have to open and close my shoulders. In the beginning, I had to think about doing this, but now I don't have to think about it. It is done by itself. […] It takes a little more time, but I knew that I did not have to open or close my phantom limb.” [Patient 7–6 years and 3 months of experience]
In contrast, all myoelectric prosthesis users reported that their PLS interacts with prosthesis use. Three of them reported that their PLS helped control their myoelectric prosthesis, whereas one reported that it has made control harder to learn. The following excerpts illustrate the view of a user who considers that PLS helps him with prosthesis control and one who considers that PLS makes it harder, respectively:
“When I changed [switched from the body-powered to the myoelectric prosthesis] the first day, it was confusing because it was not the same movement. However, now it is more natural to have the myoelectric prosthesis because it uses my [phantom] hand. I associate it almost directly with my hand.”[ Patient 1–11 years and 5 months of experience]
“I would tell you that on some occasions, they [phantom limb sensations] interfered with the control of my myoelectric prosthesis because I was trying to control the opening and closing of the myoelectric hand as if I was opening and closing my phantom hand. It induced something in my [phantom] hand, it was opening and closing, but I wasn't able to control my myoelectric prosthesis if I tried to control it like my phantom limb. I had to control my [myoelectric] hand as if I was lifting and putting my [phantom] hand back down, without trying to open and close my [phantom] hand.” [Patient 7–6 years and 3 months of experience]
None of the health professionals reported that PLS could help or interfere with the use of a body-powered prosthesis. One health professional suggested that the phantom limb can hardly be confused with the body-powered prosthesis because of its hook design. Therefore, the use of this type of prosthesis cannot really be influenced by PLS. However, half of the health professionals reported that PLS can be used to control the myoelectric prosthesis as illustrated in the following excerpt:
“The fact that they can have the sensation that they can move their [phantom] hand, either opening or closing it, will help a lot with myoelectric prosthesis control because we use the same muscle groups. We use the motor scheme that was already present before the amputation. So, when people are able to really imagine that their hand is opening and closing, it helps a lot with myoelectric control. It is a big advantage when they have such sensations.” [Health professional #3]
However, one of them commented that only nonpainful PLSs (feeling muscles or movements) were useful to control the myoelectric prosthesis, but not PLP.
How Are Phantom Limb Sensations Taken Into Account in Rehabilitation and Prosthetic Fitting?
Most patients reported that they discussed their PLP and PLS with health professionals during their rehabilitation, either spontaneously or after being questioned. However, some of them said that they only discussed it superficially or that they omitted to do so with some of their health professionals because of the absence of significantly disturbing PLP, the presence of more urgent concerns, the perception that the health professional could not help with PLP or PLS, or the fact that they had previously talked about it with other professionals. Some patients reported that their health professionals provided information about PLS and PLP. Moreover, some patients reported that psychosocial support from health professionals or from their associates played an important role in their rehabilitation. However, some patients hesitate to seek support in relation to PLP because they think that people would not be able to understand them. Considering this, some patients illustrated the importance of interacting with other amputees for information and support. Moreover, some patients reported that they simply decided not to complain about their situation.
Many patients reported that their prosthetist adjusted their prosthesis to ascertain that it was functional and comfortable and that it did not cause additional painful sensations. However, only one patient specifically reported that his prosthetist avoided stimulating areas on his residual limb that provoke PLP while he took a cast of his residual limb for his prosthesis. Many patients felt that health professionals could not help them with PLP and considered that they did not change the way they work because of PLP and PLS. In contrast, one patient reported that all health professionals at the rehabilitation center wrongly insisted on the management of PLP while his painful sensations came from a residual limb neuroma which caused him significant frustration. Two patients using myoelectric prostheses reported that health professionals indicated to them that PLS could help them control their myoelectric prosthesis.
All health professionals reported that they discussed PLS and PLP with their patients. However, only the occupational therapist reported about PLS and PLP in the patient's file. Moreover, half of the health professionals reported that patients talk about it more spontaneously when they experience PLP. The following interview excerpt illustrates the view of a prosthetist on reasons why patients do not talk spontaneously about nonpainful PLS:
“I think it is because before they come to see me, often they have seen occupational therapists, etc. So, they know that PLS exists. So when they arrive with the prosthetist, they will not necessarily talk about it spontaneously if it is not painful. Because when there is pain, they have expectations.” [Health professional #3]
The occupational therapist participating in the project reported that she gives information to her clients about PLS and reassures them about the normality of the phenomena.
A prosthetist also reported that even if most of the time PLS was explained by other health professionals earlier in the rehabilitation process, she sometimes reassures patients about the normality of PLS when this has not been done.
One prosthetist reported that while he adjusts the prosthesis, he avoids stimulating areas of the residual limb which amplify pain with the prosthesis as illustrated in the following interview excerpt:
“Sometimes, when it is a painful sensation, there is an area in the stump that when stimulated can amplify this. So sometimes, we will clear this area to try to avoid stimulation which will wake up this pain or sensation.” [Health professional #3]
Another prosthetist reported that he avoids installing heavy terminal devices when patients have PLP because he observed that it causes unpleasant sensations. She also reported that she avoids compressing the residual limb when she fits the prosthesis because it can cause PLP. Conversely, one prosthetist said that he tries to make the prosthesis tight to decrease PLP. Two prosthetists reported that the use of an isolated socket increases the patients' comfort in the prosthesis because it fits the residual limb closely. One prosthetist also reported that he sometimes helps patients when they experience coldness in the phantom limb by providing them with an isolated socket inside of their prosthesis. However, he reported that sometimes patients experience cold PLS even when the residual limb is not cold. In these cases, he feels that he is unable to help them. Despite these interventions, two prosthetists admitted that occasionally they cannot help patients with PLP. They consider these conditions as a general state that is often associated with a weak impairment acceptance level.
Furthermore, the occupational therapist reported that when patients participate in activities during therapies, PLP often decreases. She also suggested that acceptance of the phantom limb could decrease PLP. She reported that she had already tried to bring a patient who was trying to chase his PLS from his mind to accept it by explaining to him that PLS could be useful in controlling a prosthesis. Another prosthetist also reported that they sometimes use PLS to help patients learn how to use a myoelectric prosthesis:
“I remember using the memory of the hand so the person could learn to dissociate muscles that bring stimuli to the two electrodes which are used to make the myoelectric prosthesis work. In that sense, it is certain that the phantom limb can be helpful when the sensation is clear enough.” [Health professional #1]
The aim of this study was to clarify the interaction existing between the use of an upper limb prosthesis and PLSs from the perspective of prosthesis users and health professionals working with upper limb amputees, and how this potential interaction is taken into account during rehabilitation interventions related to prosthesis fitting/prosthetic training. Interaction between prosthesis use and PLSs was considered as potentially bidirectional, and therefore, the effect of the use of the prosthesis on PLSs was considered in addition to the effect of PLS on the ability to use the prosthesis.
None of the participants reported sustained changes in their PLP since they have been using their prosthesis. This result is in contrast with that of some studies suggesting that intensive use of an upper limb prosthesis might reverse cortical reorganization and decrease PLP.5,19,20 However, two of these studies specifically focused on users of prostheses driven by residual limb muscle contractions (Sauerbruch or myoeletric prostheses).19,20 This discrepancy might be explained by the fact that in this study only 4 of 12 patients used a myoelectric prosthesis, whereas the others used a body-powered prosthesis that is controlled by proximal movements. However, several other studies found no association between prosthesis use and PLP.4,13,14,21,22 Even if no sustained change in PLP was observed in relation to prosthesis use, some patients reported transient changes in their PLP while wearing and using their prosthesis. For instance, some consider that their prosthesis allows them to get involved in significant activities and when they do so, their PLP is decreased. This may be associated, at least in part, with distraction from pain caused by the involvement in significant activities. Indeed, some authors found that pain perception and pain-related cerebral activity can be modulated by controlling the level of attention directed at the noxious stimuli.31–35 Yet these protocols used simple tasks designed specially to drag attention away from or toward painful stimuli to influence the perception of brief experimental pain. Considering the multidimensional nature of chronic pain, this difference should be considered because factors that influence experimental pain may not influence chronic pain. Attention-related modulation of pain would be interesting to assess in chronic pain populations such as amputees with PLP. Furthermore, it has been shown that patients who return to work after being involved in a reemployment center show a decrease in the pain they experience.36 This also suggests that involvement in significant activities can improve the pain prognosis.
One health professional also suggested that a transient decrease in PLP while patients use their prosthesis may be associated with the normalization effect of the prosthesis. This may refer to the concept of body image. Considering the presence of body image alterations in amputees as highlighted by some authors,37–39 the interaction between this variable, prosthesis use, and PLP would be interesting to explore. Moreover, other health professionals suggested that when patients wear their prosthesis, it brings new sensations to their residual limb which may decrease pain. Even though no patients reported perceptions concurring with this view, it may be interesting to investigate in relation with the gate control theory.40 According to this theory, the prosthesis stimulates large proprioceptive and tactile fibers, which would indirectly cause an inhibitory effect on the central transmission of pain. However, some patients also reported adverse effects of the prosthesis on PLP. For instance, some reported that their PLP increases when they wear their prosthesis for an extended period of time. This assumption may seem to be in contradiction with the previously discussed decrease of PLP while subjects use their prosthesis. However, it has already been said that chronic pain patients need to take frequent breaks during activities to prevent intense enhancement of their painful stimuli.41 Activity pacing might be important for patients with PLP as well as for those living with other chronic pain syndromes.42 Furthermore, it has also been reported that the prosthesis may stimulate some areas of the residual limb which trigger PLP. These trigger points may be involved in the relation found by some authors between SP and PLP.13 Moreover, this phenomenon may refer to PLP triggered by pressure as assessed by Hunter et al.13
Interestingly, interaction between PLS and prosthesis use seems to be more important for myoelectric prosthesis users than for body-powered prosthesis users. One myoelectric prosthesis user reported that he is more aware of his phantom limb since he has been using his myoelectric prosthesis. In a longitudinal study, Hunter et al.13 found that functional prosthesis users developed better phantom limb awareness than cosmetic prosthesis users. However, within the functional prosthesis group, they did not assess prosthesis type or compare myoelectric prosthesis users with body-powered prosthesis users. This aspect would be interesting to evaluate with a quantitative design. Moreover, all myoelectric prosthesis users reported that their PLS interacts with their ability to control their prosthesis. Most of them reported that their PLS helps them with the control of their myoelectric prosthesis because the movements of the prosthesis fit with their phantom hand movements. However, one reported that his PLS made his prosthesis control harder to learn instead of helping him because the movements of the prosthesis did not fit with the movements of his phantom limb. This reveals the importance of the development of prosthesis design and training protocols which take PLS into account.23–26
Patients and health professionals participating in this study often agreed that health professionals have limited tools to help with PLP. Moreover, health professionals mostly reported sporadic interventions in which they specifically took PLS or PLP into account, but these phenomena are not systematically considered during prosthesis fitting/training. Mortimer et al.43,44 had similar results about health professional interventions for PLP and PLS in their focus groups studies with health professionals and patients. Furthermore, even if all patients using myoelectric prostheses reported that their PLS influenced their control, this type of interaction is not systematically considered by rehabilitation professionals.
The results of this study need to be carefully considered for different reasons. First, by using a qualitative design, the aim of the study was to explore the interaction which may exist between prosthesis use, PLS/PLP, and rehabilitation, as seen by patients and health professionals working with amputees. Further studies using longitudinal quantitative designs with several time measurements must objectively evaluate these relations. Second, our study sample was not representative of the entire population of upper limb amputees. People who do not use a prosthesis were not represented in our study and may have different views about the interaction between PLP/PLS and prosthesis use. In fact, some authors found a link between pain and difficulties with the prosthesis.6,7,17,18 Finally, our sample only allowed us to study the point of view of one occupational therapist and three prosthetists among health professionals.
Overall, data from this study highlighted the clinical importance of bidirectional interaction between PLP/PLS and prosthesis use, especially for myoelectric prostheses. This interaction must be taken into account in rehabilitation to maximize patient comfort and functional abilities with the prosthesis. Further studies are needed to characterize this interaction. Moreover, myoelectric and body-powered prostheses need to be compared in future studies because of the apparent differences in the interaction of PLP/PLS and these two types of prostheses.
The authors thank Isabelle Deaudelin for her help with data collection.
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KEY INDEXING TERMS: phantom limb pain; upper limb amputation; myoelectric prosthesis; body powered prosthesis; occupational therapist; prosthetist; rehabilitation