LIMB AMPUTATION frequently results in alterations in

Transcription

1 1039 Chronic Phantom Sensations, Phantom Pain, Residual Limb Pain, and Other Regional Pain After Lower Limb Amputation Dawn M. Ehde, PhD, Joseph M. Czerniecki, MD, Douglas G. Smith, MD, Kellye M. Campbell, RN, BSN, W. Thomas Edwards, MD, PhD, Mark P. Jensen, PhD, Lawrence R. Robinson, MD ABSTRACT. Ehde DM, Czerniecki JM, Smith DG, Campbell KM, Edwards WT, Jensen MP, Robinson LR. Chronic phantom sensations, phantom pain, residual limb pain, and other regional pain after lower limb amputation. Arch Phys Med Rehabil 2000;81: Objectives: To determine the characteristics of phantom limb sensation, phantom limb pain, and residual limb pain, and to evaluate pain-related disability associated with phantom limb pain. Design: Retrospective, cross-sectional survey. Six or more months after lower limb amputation, participants (n 255) completed an amputation pain questionnaire that included several standardized pain measures. Setting: Community-based survey from clinical databases. Participants: A community-based sample of persons with lower limb amputations. Main Outcome Measures: Frequency, duration, intensity, and quality of phantom limb and residual limb pain, and pain-related disability as measured by the Chronic Pain Grade. Results: Of the respondents, 79% reported phantom limb sensations, 72% reported phantom limb pain, and 74% reported residual limb pain. Many described their phantom limb and residual limb pain as episodic and not particularly bothersome. Most participants with phantom limb pain were classified into the two low pain-related disability categories: grade I, low disability/low pain intensity (47%) or grade II, low disability/ high pain intensity (28%). Many participants reported having pain in other anatomic locations, including the back (52%). Conclusions: Phantom limb and residual limb pain are common after a lower limb amputation. For most, the pain is episodic and not particularly disabling. However, for a notable subset, the pain may be quite disabling. Pain after amputation should be viewed from a broad perspective that considers other anatomic sites as well as the impact of pain on functioning. Key Words: Amputation; Chronic pain; Phantom limb pain; Stump pain; Sensation; Leg; Rehabilitation by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation From the Departments of Rehabilitation Medicine (Ehde, Czerniecki, Campbell, Jensen, Robinson), Orthopaedic Surgery (Smith), and Anesthesiology (Edwards), University of Washington; the VA Puget Sound Health Care System (Czerniecki); Harborview Medical Center (Ehde, Smith, Campbell, Edwards, Robinson); and the VA Center for Amputation, Prosthetics and Limb Loss Prevention (Czerniecki), Seattle, WA. Submitted April 23, Accepted in revised form January 21, Supported by grant PO1 HD/NS33988 ( Management of Chronic Pain in Rehabilitation ) from the National Institute of Child Health and Human Development and the National Institute of Neurological Disorders and Stroke. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to Dawn Ehde, PhD, Department of Rehabilitation Medicine, University of Washington School of Medicine, 325 Ninth Avenue, Box , Seattle, WA /00/ $3.00/0 doi: /apmr LIMB AMPUTATION frequently results in alterations in painful and nonpainful sensory experiences. 1 Most of the amputation literature has focused on two categories of amputation-related pain: phantom limb pain and residual limb pain (also referred to as stump pain ). Phantom limb pain is defined as painful sensations perceived in the missing portion of the amputated limb, while residual limb pain is perceived as originating in the residual portion of the limb (ie, the stump). 2 Phantom limb sensations are nonpainful sensations perceived as emanating from the portion of the amputated limb that is missing. 3 Reports of phantom limb pain s prevalence vary widely in the literature, with rates ranging from 0.5% to 100% of persons with amputations. 2,4-6 This notable variability is largely due to differences in study methods, particularly choice of study population. 5 More recent studies 1,4,5 using improved methods have suggested that most persons who undergo limb amputations, possibly as many as 85%, will experience some form of phantom limb pain. In addition to its prevalence, phantom limb pain has also been characterized in terms of frequency, duration, intensity, and verbal descriptors (for a review, see Sherman 1 ). Studies of these characteristics, however, have used nonstandardized measures, which makes comparison with other types of pain difficult. Phantom limb pain tends to be described as intermittent and of moderate intensity; for example, average pain intensity of 5 on a 0 to 10 numeric rating scale. 1,4 Its effect on patients functional ability has not been well described. The few studies 7,8 that have addressed its effect were focused mostly on vocational functioning. Although universal during the postoperative period, 9 residual limb pain is thought to be less common than phantom limb pain in the months and years after an amputation. 2-4,9 Considerable variability exists in the reported frequency of residual limb pain. For example, in a longitudinal study, the prevalence of individuals with residual limb pain was 22% at 6 months and 21% at 2 years after amputation. 4,10 Others 9,11,12 have estimated the prevalence to be between 10% and 25%. In a recent survey 13 of veterans with amputations, 56% reported chronic residual limb pain. The duration, intensity, sensory descriptors, and affective descriptors of residual limb pain have received minimal attention in the literature. Still less is known about the prevalence of other types of pain after lower limb amputation. However, persons with lower limb amputations often develop gait patterns to accommodate a prosthesis 14 that may put them at risk for other types of pain such as pain in the back, hips, and unaffected leg. For example, one study 15 found back pain to be common in a sample of persons with lower limb amputations. Over half of this sample experienced all 3 types of pain measured in that study phantom limb, residual limb, and back pain. The primary aim of the present study was to broaden our understanding of the experience of pain following lower limb amputation and to examine the effect of phantom limb pain on function by measuring pain-related disability. The specific aims were to: (1) determine the frequency, duration, and intensity of phantom limb sensations, phantom limb pain, and residual limb

2 1040 PAIN AFTER AMPUTATION, Ehde pain in a community-based sample; (2) broaden our understanding of the sensory and affective dimensions of phantom limb pain; (3) examine the effect of phantom limb pain on function, by means of a standardized measure of pain-related disability; and (4) explore the overall pain experience by assessing pain in locations other than the amputated limb and by finding the total number of pain problems. METHODS Participants Participants were recruited from the pool of patients who had undergone a lower limb amputation at two Seattle area hospitals: Harborview Medical Center, a Level 1 trauma center, and the Veterans Administration Puget Sound Health Care System. Inclusion criteria were: (1) 6 or more months since lower limb amputation, (2) at or over the age of 18 years, and (3) ability to read and write English. We mailed questionnaires to 798 individuals randomly selected from the larger pool of potential participants. Of the questionnaires mailed, 189 were returned by the postal service as not being deliverable, 83 were returned as addressee deceased, and 73 were returned by respondents as inappropriate (less than 6 months since amputation, person did not have a lower limb amputation, or person was under the age of 18). Thus, a maximum of 453 surveys theoretically could have been completed. Twenty-three potential subjects indicated they did not want to participate. A total of 255 useable questionnaires were returned, yielding a return rate of 56% (255/453). The study protocol was approved by the University of Washington Human Subjects Committee. Measures The questionnaire we used assessed a number of dimensions of nonpainful phantom limb sensations, phantom limb pain, and residual limb pain. It was divided into sections distinguishing the types of sensations and asked respondents to answer questions on each phenomenon. To facilitate participants understanding of the pain categories, the types of pain and sensation were defined for them in the following ways. Phantom limb was defined as the portion of the limb that was amputated or missing. Nonpainful phantom limb sensations were defined as sensations in the missing (phantom) limb that were not painful (eg, the feeling that the missing foot is wrapped in cotton). Phantom limb pain referred to painful sensations in the phantom limb, while residual limb pain referred to pain in the portion of the amputated limb that was still physically present (ie, the stump ). These definitions were provided at the beginning of each of the respective survey sections to assist respondents in differentiating among the various types of sensations and pain. Demographic and amputation history questionnaire. Participants were asked demographic questions including their gender, age, educational level, employment status, marital status, and ethnicity. They also answered questions specific to their amputation, including the date of their most recent amputation surgery or revision, the medical reason for the amputation, the level of the amputation, and their prosthesis use. Pain intensity. Present, worst, least, and average pain were assessed by means of an 11-point numerical rating pain scale (0 no pain; 10 pain as bad as it could be). The specific questions and end points for current, worst, and average pain were adapted from the pain intensity items of the Chronic Pain Grade (CPG). 16 A 3-month window was used to assess worst, least, and average pain intensity. Sensory and affective qualities of phantom limb pain. Participants were asked to rate the sensory and affective qualities of their phantom limb pain using the Short-Form McGill Pain Questionnaire (SF-MPQ). 17 The SF-MPQ consists of 15 pain descriptors from the sensory (n 11) and affective (n 4) categories of the standard MAQ. 18 Each descriptor is rated by the respondent on an intensity scale ranging from none (0) to severe (3). This measure yields three scales: a sensory scale (range, 0 to 33), an affective scale (range, 0 to 12), and a total scale (range, 0 to 45). Based on previously reported findings 5 on the quality of phantom limb pain, we added 9 exploratory sensory words to the SF-MPQ: stinging, cutting, piercing, radiating, tight, nagging, squeezing, tingling, and shocking. Since they are not part of the standardized SF-MPQ, these additional descriptors were not included in the summary scoring (ie, sensory, affective, and total scales). To minimize subject burden, participants did not complete a SF-MPQ for residual limb pain. However, they were asked to list the words that best described their nonpainful phantom limb sensations and their residual limb pain. Pain-related disability. The CPG 16 was used to assess the severity of disability associated with phantom limb pain. The CPG is a simple, reliable, and valid measure that has been used to hierarchically grade the severity of chronic pain in a variety of pain populations. 16,19 This measure is comprised of 3 pain intensity items described above (present, worst, and average pain intensity), a question on the number of days in the past 3 months that the respondent was kept from his or her usual activities because of pain ( disability days ), and 3 interference items that ask how pain has interfered with daily activities, social activities, and work over the past 3 months. The first interference item asks respondents to rate pain s interference with their daily activities on a scale of 0 to 10 (0 no interference; 10 unable to carry out activities). The second item asks respondents to rate how much pain has changed their ability to take part in recreational, social, and family activities (0 no change; 10 extreme change). The third interference item asks how much pain has changed their ability to work (including housework), using the 0 to 10 scale (0 no change; 10 extreme change). Participants were asked to respond to the CPG items with reference to the 3 months preceding their completion of the questionnaire. The CPG combines the intensity items, disability days, and interference items to classify individuals with pain into 1 of 5 hierarchical categories: grade 0, no pain problem; grade I, low disability, low pain intensity; grade II, low disability, high pain intensity; grade III, high disability that is moderately limiting; and grade IV, high disability that is severely limiting. In this scale, the term disability refers to pain-related disability and not to the disability associated with having an amputation. Persons at grades I and II may differ in pain intensity without differing in the disability caused by the pain. For example, a person in grade II could report an average pain intensity greater than that reported by a person in grade I, yet both could report minimal pain-related disability. For grades III and IV, pain intensity is typically of moderate to high intensity, and thus the differences between these two groups is in the severity of pain-related limitations and disability. 16 Thus, for example, a person with grade III pain may report more pain-related disability days and interference with activities than someone in grade II. A person with grade IV pain may report an even greater number of pain-related disability days and interference with activities than someone with grade III pain severity. Other pain variables. Frequency and duration of nonpainful sensations, phantom limb pain, and residual limb pain

3 PAIN AFTER AMPUTATION, Ehde 1041 were assessed. Participants were also asked to rate the affective quality of their pain by indicating how bothersome their phantom limb pain and residual limb pain were, on average, for a three-month window. An 11-point rating scale similar to that used on the pain intensity items was used (0 not at all bothersome; 10 pain as bothersome as could be). Finally, participants were asked if they had pain in other sites (eg, back, neck) and to rate which of all of the possible pain sites was their worst pain problem. Procedure Names of potential participants were randomly selected from the hospital databases. The mailing of questionnaires was phased over 15 months, with approximately 55 questionnaires mailed each month. Each potential recruit received a packet by mail containing a cover letter, the pain questionnaire, and a stamped envelope for returning the completed questionnaire. The cover letter accompanying the questionnaire instructed respondents to complete the questionnaire even if they did not have pain. To facilitate subject recruitment, follow-up calls and mailings were made to those who had not returned the packet. For those questionnaires that were returned with incomplete or incomprehensible answers, a research assistant contacted the participant by phone to obtain or clarify their answers. RESULTS Description of Participants The majority of participants in the sample were male (81%). They ranged in age from 19 to 86 years (mean 55.1, standard deviation [SD] 14.3). Sixty-one percent were married or living with a partner. Most of the sample (87%) reported an education of 12th grade or more. Participant ethnicity, employment status, and amputation characteristics are listed in table 1. The most common level of amputation was transtibial (below knee, 54%). Trauma accounted for 53% of the amputations. The range of time since the most recent amputation surgery was 6 months to 74 years (mean 14.2, median 7, SD 15.7yrs). Most of the participants (83%) reported wearing a prosthesis. Among those using prostheses, the average use was 13.2 hours daily (SD 4.1). Nonpainful Phantom Limb Sensations More than three-fourths of the sample (n 201, 79%) reported that they experienced nonpainful phantom limb sensations. Table 2 lists the frequency and duration of phantom sensations, phantom limb pain, and residual limb pain for the 4 weeks preceding completion of the survey. As seen in this table, most (71%) of those reporting nonpainful phantom limb sensations described their sensations as intermittent (ie, sensations that come and go ). Fifty-one percent reported 1 sensation episode or less a week. For most of those with nonpainful phantom sensations, the duration of their typical episode was brief a few minutes (56%) or several minutes to an hour (26%). Participants were also asked to describe the quality of their nonpainful sensations. Of the 181 participants who listed verbal descriptors of their nonpainful sensations, the most commonly endorsed words were tingling (n 49, 27%), itching (n 48, 26%), sensations of missing feet or toes (n 33, 18%), and feeling asleep (n 24, 13%). Phantom Limb Pain Nearly three-fourths of the sample reported that they experience phantom limb pain (n 183, 72%). Similar to nonpainful phantom limb sensations, phantom limb pain was described as Table 1: Sample Characteristics Characteristic Distribution (%) Ethnicity White, non-hispanic 86 American Indian/Native American 5 African American 5 Other 4 Employment Status* Employed full-time 22 Employed part-time 9 Attending school/vocational training 3 Retired 45 Unemployed due to pain 3 Unemployed due to disability 29 Unemployed for other reasons 3 Amputation level Transfemoral 30 Knee disarticulation 5 Transtibial 54 Ankle disarticulation (Symes) 3 Other (hip, toes) 8 Reason for Amputation* Trauma (including war injuries) 53 Vascular disease 20 Infection 23 Gangrene 21 Diabetes 13 Congenital problem 2 Tumor 5 Other 19 * Multiple answers allowed and thus percentages add to 100%. episodic by the majority of those with this type of pain (81%; see table 2). Half (50%) of those with phantom limb pain reported 1 phantom limb pain episode a week or less. The duration of the typical phantom pain episode was brief for most respondents with phantom pain a few minutes (52%) to an hour (26%). When asked to rate their average phantom limb pain over the last 3 months, participants with phantom limb pain reported a mean intensity rating of 5.1 (SD 2.6) on a scale of 0 (no pain) to 10 (pain as bad as could be). Of those with phantom limb pain, 30% reported average phantom limb pain of severe intensity (ie, ratings of 7 to 10). To better understand the sensory, affective, and evaluative dimensions of the phantom limb pain experience, we asked participants with phantom limb pain to complete the modified SF-MPQ. For this sample, the SF-MPQ mean scale scores were as follows: sensory scale, mean 11.9 (SD 6.8; range, 0 to 33); affective scale, mean 2.5 (SD 2.9; range, 0 to 12); and total scale, mean 14.5 (SD 8.9; range, 0 to 45). We also conducted frequency analyses of the individual items of the SF-MPQ, including the 9 additional descriptors. For respondents who reported pain, the 6 most commonly endorsed words (with the percentage endorsing each in parentheses) were sharp (78%), tingling (77%), shooting (76%), stabbing (72%), throbbing (67%), and aching (56%). Of note is that only 1 of these 6 words (tingling) was an added descriptor and not part of the original SF-MPQ. The CPG scale was used to categorize participants phantom limb pain into 1 of 5 categories: grade 0, no pain; grade I, low disability, low pain intensity; grade II, low disability, high pain intensity; grade III, high disability, moderately limiting; and grade IV, high disability, severely limiting. In this scale, disability refers to pain-related disability and not disability

4 1042 PAIN AFTER AMPUTATION, Ehde Table 2: Reported Frequency and Duration of Nonpainful Phantom Sensations, Phantom Limb Pain, and Residual Limb Pain for the 4 Weeks Preceding Completion of the Survey Nonpainful Sensations (n 201) Distribution (%) Phantom Limb Pain (n 183) Residual Limb Pain (n 188) Frequency of sensations/pain past 4 weeks None Intermittent Constant, with variation in intensity Constant, with little variation in intensity Frequency of episodes (if intermittent) Once a week or less times a week times a week or more Duration of episodes (if intermittent) Few minutes Several minutes to an hour Several hours A day or longer associated with having an amputated leg. Figure 1 depicts the percentages of the sample falling into these categories. The majority (75%) of persons with phantom limb pain fell into the two low pain-related disability categories (grades I and II). Respondents also rated how bothersome their phantom limb pain and residual limb pain was, on average, over the previous 3 months on a scale of 0 (not bothersome) to 10 (as bothersome as could be). The mean rating for phantom limb pain was 4.6 (SD 3.3). Of those with phantom limb pain, 10% described their pain as not at all bothersome (ie, 0 on the scale), 42% described it as mildly bothersome (ie, 1 to 4 on the scale), 16% described it as moderately bothersome (ie, 5 to 6), and 32% described it as severely bothersome (7 to 10). Residual Limb Pain Seventy-four percent (n 188) of the sample reported that they experience residual limb pain. As depicted in table 2, for those with residual limb pain, most (72%) described it as intermittent. The frequency of residual limb pain episodes was variable and ranged from once a week or less (41%) to more than 4 to 6 times weekly (30%). For a third of the respondents with residual limb pain, the duration of the typical painful episode lasted several hours or longer (34%). Only 32% described the duration of their residual limb pain as brief (ie, a few minutes). Among those with residual limb pain, the mean intensity rating for average residual limb pain was 5.4 on the 0 to 10 scale (SD 2.7). Thirty-eight percent of the respondents reported average residual limb pain of severe intensity (ie, ratings of 7 to 10). Of the 175 participants who listed words to describe the quality of their residual limb pain, the following descriptors were the most commonly reported: aching (n 40, 23%), sharp (n 28, 16%), throbbing (n 25, 14%), hot-burning (n 22, 13%), tingling (n 18, 10%), and shocking (n 16, 9%). The average rating of how bothersome the residual limb pain was for the sample was 5.2 (SD 2.9). Of those with residual limb pain, 4% described their pain as not at all bothersome (ie, 0 on 0 to 10 scale), 36% described it as mildly bothersome (ie, 1 to 4 on the scale), 27% described it as moderately bothersome (ie, 5 to 6), and 33% described it as severely bothersome (7 to 10). Other Pain Sites Since we were interested in knowing if persons with lower extremity amputation have pain in sites other than their amputated limb, we asked participants to indicate whether they had persistent, bothersome pain in seven other pain locations. As shown in table 3, which lists the specific pain sites and corresponding frequencies, many participants reported pain in locations other than the amputated limb. We also asked those participants with any type of pain to endorse which pain site was their worst pain problem. Residual limb pain was ranked by the highest number of respondents as their worst pain problem, followed by phantom limb pain and back pain (table 4). To better understand the overall experience of pain after lower limb amputation, we looked at the total number of pain sites participants endorsed from the following locations: phantom limb pain, residual limb pain, and back pain. These analyses revealed that over a third of the sample (36%) reported pain in all 3 locations. More than one-third (34%) experienced pain in 2 of the 3 locations, and 22% experienced pain in only 1 location. Eight percent of the respondents were pain-free. Table 3: Frequency of Participants Reporting Persistent, Bothersome Pain in Sites Other Than the Amputated Limb Pain Site Distribution (%) Fig 1. Chronic Pain Grade classification for phantom limb pain (n 183). Back 52 Other leg/foot 43 Buttocks/hips 37 Neck/shoulders 31 Arms/hands 24 Abdomen 12 Head 8

5 PAIN AFTER AMPUTATION, Ehde 1043 Table 4: Sites Rated as Worst Pain Problem in Participants With Pain (n 229) Pain Site Percent Rating Site Worst Pain Problem Residual limb 33 Phantom limb 24 Back 17 Neck/shoulders 9 Other leg/foot 7 Buttocks/hips 4 Arms/hands 3 Head 1 Abdomen 1 Other sites 1 Responses to question, Which pain problem is your worst? DISCUSSION The primary aim of our investigation was to quantify and characterize the overall pain experience of persons with lower limb amputations. It is important to consider a broader approach to understanding the potential musculoskeletal and functional consequences of lifelong adaptation to a disabling condition. Therefore, in addition to the typical postamputation pain problems of phantom limb pain and residual limb pain, we measured pain experienced in other anatomic areas. Besides quantifying and characterizing the pain experience, we sought to increase our understanding of the functional impact of pain by examining phantom pain-related disability. Our results indicate that persons with lower limb amputations experience a variety of nonpainful and painful phantom limb sensations. Over 70% of our sample reported experiencing nonpainful phantom limb sensations and phantom limb pain. Most described their phantom limb sensations and phantom limb pain as intermittent; relatively few reported constant sensations (18%) or phantom limb pain (9%). Episodes of sensation and pain were typically brief, lasting only a few minutes to an hour. Thus, while the rate of sensations and pain was high in this sample, the experience of pain was typically a transient phenomenon. The prevalence, frequency, and duration of phantom limb sensations and phantom limb pain found in the present study are consistent with other reports 1,4,10,15 in the literature. The average pain intensity rating for phantom limb pain in our sample (mean 5.1) is remarkably similar to the mean intensity ratings reported by Sherman and Sherman 20 in their samples of civilians (mean 5.0) and military personnel (mean 5.3). To our knowledge, this study was the first to use two standardized pain measures with phantom limb pain: the SF-MPQ and the CPG. The SF-MPQ enables clinicians and researchers to quantify both the sensory (temporal, spatial, pressure, thermal, and other sensory qualities) and affective (emotional arousal and disruption) dimensions of the pain experience. For instance, the words throbbing, cramping, and tender are examples of sensory descriptors. Affective descriptors are sickening, fearful, and punishing-cruel. The SF-MPQ results found in the present sample were similar to a postsurgical pain sample and a musculoskeletal pain sample reported by Melzack, 17 suggesting a similarity in pain experience across these samples. Thus, surprisingly, persons with phantom limb pain tended to describe the sensory and affective qualities of their phantom limb pain in a manner comparable to persons with other types of pain. The words used most frequently to describe phantom limb pain were sharp, tingling, shooting, stabbing, throbbing, and aching, all of which are sensory descriptors. Of the 9 exploratory sensory words added to the original SF-MPQ, only 1 word, tingling, was 1 of the 6 most commonly endorsed descriptors for the entire measure. The CPG enabled us to quantify the disability associated with phantom limb pain. Three-fourths of the persons in our sample who reported phantom limb pain fell into the 2 low pain disability categories on the CPG: the low-disability/lowintensity category (grade I) and the low-disability/highintensity category (grade II). Participants in these 2 categories reported minimal disability from their phantom limb pain. That is, in the 3 months before completing the survey, pain did not interfere much with their daily, social, or work activities or keep them from their usual activities. The percentage of participants reporting grade III (high disability that is moderately limiting; 9%) or grade IV (high disability that is severely limiting; 14%) in this sample was lower than a chronic back pain sample (20% and 17%, respectively) and a chronic headache sample (20% and 10%, respectively) described by Von Korff and coworkers. 16 Thus, although phantom limb pain was common in our sample, it was not perceived as significantly disabling by most participants. However, nearly one-fourth of the sample (23%; grades III and IV) reported high disability and moderate to severe limitations from their phantom limb pain. For these persons, phantom limb pain reportedly caused significant disability, including keeping them from their usual activities as well as causing considerable interference with their daily, social, recreational, and work activities. Our data suggest that residual limb pain is as common as phantom limb pain, and in fact, was rated the worst pain problem by more participants than any other pain site. The rate of residual limb pain in our sample (70.5%) was notably higher than the rate reported in previous studies 2,4,10-12 with the exception of the Smith 15 study, which found a similar rate of residual limb pain. However, the Smith sample, although smaller in size, was obtained using part of the same databases that we used in the present study. Thus, the similarity in results may be because the two samples are from a similar population, although data collection for the two samples was separated by more than 2 years. Alternatively, the discrepancy between our frequency data and others may be related to how residual limb pain is defined and measured. Several authors 9,21 have criticized the amputation pain literature for not always clearly distinguishing residual limb pain from phantom limb pain. Even when assessed as a distinct pain problem, residual limb pain typically receives less attention (ie, fewer questions). Residual limb pain was clearly defined on our questionnaire. Our results suggest that, like phantom limb pain, residual limb pain is typically episodic in nature in addition to being prevalent. Although most respondents did not describe their residual limb pain as particularly bothersome, a third (33%) described their residual limb pain as extremely bothersome. These results clearly indicate that chronic pain following amputation is not necessarily limited to the amputated limb. More than half of our sample (52%) reported that back pain was a persistent, bothersome problem for them. This rate, although lower than the 71% rate of back pain found in our previous work 15 with another sample, is higher than the prevalence of chronic back pain in the general population. 22 Persistent, bothersome pain in the nonamputated limb (43%), the buttocks/ hips (36%), and the neck/shoulders (31%) was also reported by a notable number of participants. Interestingly, nearly half of the participants rated their worst pain problem as being located in an anatomic site other than the amputated limb, including the back, the neck/shoulders region, and the nonamputated limb. Less than 10% of the total sample reported being pain-free, and

6 1044 PAIN AFTER AMPUTATION, Ehde 70% of the participants reported experiencing pain in two or more locations. Although these findings are preliminary and warrant further investigation, they suggest that the experience of chronic pain following lower limb amputation is complex and multidimensional. Clearly, an amputation may put an individual at risk for developing chronic pain in the amputated limb as well as pain in other regions, possibly because of changes necessitated by living with the amputation (eg, musculoskeletal pain from changes in gait). Several limitations of this study should be noted. The results of this study are constricted to persons with lower limb amputations and do not necessarily reflect the experience of persons with upper limb amputations. Relative to the general population of persons with lower limb amputations, this sample included a larger number of participants who were young or whose amputations resulted from traumatic injuries; thus, these results may be limited in their generalizability to the larger population. The possibility also exists that persons with pain were overrepresented in this sample, in that persons without pain may have been less likely to return the questionnaires. If it is assumed that all nonrespondents were pain-free, the conservative estimates of the prevalence rates would be 44% for nonpainful phantom limb sensations, 40% for phantom limb pain, and 42% for residual limb pain. However, the study design attempted to avoid a skewed sample by using random sampling techniques and a community, rather than clinic, sample. The instructions to participants also encouraged participants to return the questionnaire even if they did not have pain. Thus, while it is possible that the pain rates found in this study overrepresent the rate of pain problems in the amputation population, this study showed that pain exists in a substantial number of persons with lower limb amputations. CONCLUSION Nonpainful phantom limb sensations, phantom limb pain, and residual limb pain are common after a lower limb amputation. For the majority of persons, the pain associated with an amputation is episodic and not particularly bothersome or disabling. However, for many, phantom limb pain and/or residual limb pain may be highly disabling or bothersome. Since this group may account for as many as 10% to 25% of persons with lower limb amputations, it warrants empirical attention and clinical intervention. Our understanding of the experience of pain after amputation may be improved if we view it from a broader perspective one that is not limited to the amputated limb but takes into account other anatomic sites that may be affected by the amputation. Future research should turn attention away from studying only the prevalence, frequency, and duration of phantom limb pain and residual limb pain and should focus on the impact such pain has on a person s quality of life and functional ability, including vocational and psychosocial functioning. Research would be strengthened if standardized measures were used, which would allow comparisons with other disability groups. It will also be important for researchers to examine the potential physiologic, biomechanic, and psychosocial factors that may put some persons with amputations at risk for developing significant pain-related disability. Our study did not look at the experience of chronic pain in persons with upper limb amputations; research on pain and its impact in this population is needed. Our results, as well as the results of Smith et al, 15 point to the need to research other potential pain sites, especially the back. Acknowledgments: The authors thank the data collection team of Amy Hoffman (Project Coordinator), Bridget Bjork, Beth Gerrard, Catherine McClellan, Erica Tyler, and Jinbo Chen for their invaluable assistance in data collection, entry, and analysis. They also thank Dee Malchow, RN, MN, for her assistance in the study design and interpretation of the results. References 1. Sherman RA. Phantom pain. New York: Plenum; Davis RW. Phantom sensation, phantom pain, and stump pain. Arch Phys Med Rehabil 1993;74: Melzack R. Phantom limbs. Sci Am 1992;266: Jensen TS, Krebs B, Nielsen J, Rasmussen P. Immediate and long-term phantom limb pain in amputees: incidence, clinical characteristics, and relationship to pre-amputation pain. Pain 1985;21: Sherman RA, Sherman CJ. Prevalence and characteristics of chronic phantom limb pain among American veterans. Am J Phys Med 1983;62: Stannard C. Phantom limb pain. Br J Hosp Med 1993;50: Durance J, O Shea P. Upper limb amputees: a clinic profile. Int Disabil Stud 1988;10: Millstein S, Bain D, Hunter G. A review of employment patterns of industrial amputees factors influencing rehabilitation. Prosthet Orthot Int 1985;9: Loeser JD. Pain after amputation: phantom limb and stump pain. In: Bonica J, editor. The management of pain. 3rd ed. London: Churchill Livingstone; p Jensen TS, Krebs B, Nielsen J, Rasmussen P. Phantom limb, phantom pain, and stump pain in amputees during the first six months following limb amputation. Pain 1983;17: Abramson AS, Feibel A. The phantom phenomenon: its use and disuse. Bull N Y Acad Med 1981;57: Carlen PL, Wall PD, Nadvorna H, Steinbach T. Phantom limbs and related phenomena in recent traumatic amputations. Neurology 1978;28: Wartan SW, Hamann W, Wedley JR, McColl I. Phantom pain and sensation among British veteran amputees. Br J Anaesth 1997;78: Perry J. Atlas of limb prosthetics: surgical, prosthetic, and rehabilitation principles. In: Bouker JH, Michael JW, editors. Atlas of limb prosthetics. St. Louis: CV Mosby; p Smith DG, Ehde DM, Legro MW, Reiber GE, delaguila M, Boone DA. Phantom limb, residual limb, and back pain after lower extremity amputations. Clin Orthop 1999;361: Von Korff M, Ormel J, Keefe FJ, Dworkin SF. Grading the severity of chronic pain. Pain 1992;50: Melzack R. The short-form McGill Pain Questionnaire. Pain 1987;30: Melzack R. The McGill Pain Questionnaire: major properties and scoring methods. Pain 1975;1: Smith BH, Penny KI, Purves AM, Munro C, Wilson B, Grimshaw J, et al. The chronic pain grade questionnaire: validation and reliability in postal research. Pain 1997;71: Sherman RA, Sherman CJ. A comparison of phantom sensations among amputees whose amputations were of civilian and military origins. Pain 1985;21: Jensen TS, Rasmussen P. Phantom pain and other phenomena after amputation. In: Wall PD, Melzack R, editors. The textbook of pain. 3rd ed. London: Churchill Livingstone; p Andersson, GBJ, Pope MH, Frymoyer JW, Snook S. Epidemiology and cost. In: Pope MH, Andersson GBJ, Frymoyer JW, Chaffin DB, editors. Occupational low back pain: assessment, treatment, and prevention. St Louis: Mosby; p