Balance confidence among people with lower-limb amputations. (Research Report).

Assessing and improving mobility are among the primary goals of rehabilitation for people with lower-limb amputations. Often clinicians rely on performance tests such as the Two-Minute Walk Test (1) and the Timed Up & Go Test (2) or on indicators such as the use of mobility devices to determine a person's rehabilitation status. Although these measures offer some insight into physical performance or capability for mobility, we believe they do not sufficiently focus on psychological indicators such as a person's confidence with balance. A person's decreased confidence in his or her balance may impede mobility and community reintegration as much as having a physical impairment. Decreased confidence constitutes a potentially remediable barrier to mobility. (3,4)

Measures of balance confidence were developed to provide a sensitive measure of fear of falling. (3,5,6) Earlier approaches simply consisted of asking whether someone was afraid of falling. (7-9) Balance confidence, which is based on Bandura's theory of self-efficacy, (10) is defined as the belief that the individual has the capability to perform an activity or action. Defining fear of falling as balance confidence during activities, in our opinion, overcomes 3 limitations associated with the more general measure of fear. (6)

First, balance confidence is measured over a continuum of activities, from easy to more difficult, thereby providing better measurement qualities than if there was a simple dichotomous measure. Second, asking about the degree of confidence in performing an activity is less threatening than asking about a fear, which not only has psychiatric or phobia-related connotations but also can be perceived as a sign of weakness, especially among men. (6,11) Finally, evidence suggests that measures of self-confidence are strongly linked with independence in daily and social activities. (4,12,13)

Balance confidence has received considerable attention recently among researchers and clinicians working with elderly people. (4,14,15) However, only one published study (13) has investigated balance confidence among people with lower-limb amputations. We believe it to be plausible that balance confidence would be important among those with lower-limb amputations. The most obvious reasons are the altered gait pattern that occurs with use of prostheses, increased energy expenditure, and loss of sensory feedback associated with the loss of a lower limb, even among young people in good health whose amputation resulted from trauma. Moreover, because people with lower-limb amputations are most often elderly people with multiple comorbidities, (16) the loss of a lower limb adds an additional challenge. Finally, the prevalence for falls and fear of falling among people with lower-limb amputations appears to be very high. (17)

Our descriptive study was conducted to examine balance confidence among people with transtibial (TT) or transfemoral (TF) lower-limb amputations. Our objectives were: (1) to describe balance confidence among people with TT or TF lower-limb amputations, (2) to determine whether differences in balance confidence exist between people who have had amputations due to vascular and nonvascular causes, and (3) to determine what factors are associated with balance confidence while controlling for amputation cause and level.

Method

Design and Sample

We surveyed a sample of community-dwelling individuals with unilateral TT or TF amputations. To ensure that subjects had become accustomed to using their prostheses, only those who had been ambulating using their prostheses for a minimum of 6 months following discharge from the formal prosthetic rehabilitation program and were wearing their prostheses on a daily basis were included in the study.

A convenience sample of people who attended 1 of 2 university-affiliated clinics for people with amputations (the Southwestern Regional Amputee Clinic at St Mary's Hospital in London, Ontario, Canada, and the Chedoke Amputee Clinic in Hamilton, Ontario, Canada) between January 1 and December 31, 1998, was used. Both clinics provide 3-, 6-, and 12-month follow-up visits during the year after discharge from the rehabilitation program and annual follow-up after that. The sampling frame potentially consisted of every patient examined in these 2 clinics during that time period.

Of 563 eligible individuals, responses were received from 435 (77%). Comparisons of respondents and nonrespondents based on data from our chart review revealed no statistically significant differences at P<.05. Descriptive statistics for the total sample are presented in Table 1. The mean age of the primarily male (71%) subjects was 62.0 years (SD=15.7). The majority of the respondents were married (62.1%), had less than a grade 12 education (57.7%), and were not working (74.5%). The cause of amputation was related to vascular reasons for 52.9% of the sample, with 73.3% having a TT amputation compared with 26.7% having a TF amputation. Proportionally, 60% of the respondents had a TT amputation and 44% had a TF amputation for vascular reasons.

Measurement

Information from chart reviews was linked with survey data to create the database for the analyses. Chart review variables included sex, date of birth, amputation date, level of amputation (TF or TT), and cause of amputation (vascular or nonvascular). Etiology was determined based on the surgical reason for the amputation. Classification of the cause of amputation was based on the surgical report in the patient files. Table 2 presents a breakdown of how diagnoses were classified. Individuals identified as having a Symes amputation (n=23) were included in the TT amputation group, and those with a through-knee amputation (n=5) were included in the TF amputation group. Inclusion and classification of individuals with Symes and through-knee amputations was based on our clinical experience, which suggests that the functional ability of these individuals is very similar to that of people with TT and TF amputations, respectively.

The remainder of the information was collected using a mailed survey questionnaire following techniques recommended by Dillman. (18) Variables were included because of their clinical relevance or because of previously reported importance in studies of balance confidence in other populations.

Socio-demographic factors. Data for age and sex were taken from patient charts, and information regarding marital status, social support, education level, employment, and income status was ascertained from the survey questionnaire. Social support was measured using a 6-item version of the Interpersonal Support Evaluation List (ISEL). (19,20) The ISEL measures 4 dimensions of support: tangible, belonging, self-esteem, and appraisal. Scores from a 4-point Likert scale are summed, with higher scores indicating greater sources of support.

Amputation-related factors. The number of years since amputation was based on the date of the most recent major surgery on the limb with the amputation recorded in the subject's hospital chart. For those cases where a revision of a previous amputation was performed (eg, from TT to TF), the date of the revision was considered the amputation date. Amputation cause was determined from notes in the chart. Respondents reported current mobility device use by checking whether they used canes, crutches, walkers, or no device when ambulating with the prostheses. The ability to "walk automatically" was determined from the survey by asking whether the subject was required to concentrate on each step. This question was taken from the Prosthetic Profile of the Amputee questionnaire. (21)

Health-related factors. A physical health profile was generated based on a variety of variables. Perceived health status was assessed by having respondents rate their health on a 5-point ordinal scale ranging from "poor" to "excellent." A comorbidity count was derived using a list of 19 common health ailments, an approach used in the Ontario Health Survey. (22-24) Information about comorbidities was based on whether a physician had told the respondents that they had disorders such as heart disease, diabetes, or stroke. Data on the reliability of these measurements are not known, and we did not study their reliability. Data on medication use were collected by asking respondents if they were taking prescribed medications for any condition. (22-24) The reliability of these data also is not known. Joint pain was assessed by asking respondents whether pain was experienced in any joints. Examples included with the question included the wrists or hips in order to cue respondents to think of both upper and lower limbs. A separate question asked about the existence of general back pain. Fall injury was determined by asking the respondents whether they had "seriously" injured themselves from a fall in the 12 months prior to completing the survey questionnaire. Disability status was established by identifying any limitations in performing one or more activities of daily living using the Postal Barthel Index. (25) Kappa values for 2-week test-retest reliability of data obtained for the items among a group of individuals who had a stroke ranged from .49 to .90. (25) Although the validity of data obtained with the Barthel Index has been well established, (26) studies of validity for this self-report format have not been compared with the interview administration. We added 2 questions regarding independence with donning and doffing prostheses to the Barthel Index. Problems with the limb without the amputation were identified by use of a list of items about sensation, ulcers, pain, and swelling in the remaining limb. (21) Self-reports of alcohol consumption were scored as "daily," "occasional," or "never used."

Psychological factors. The level of depression was measured using the Center for Epidemiologic Studies Depression (CES-D) Scale. (27) Responses on 4-point Likert scales are summed across 20 items, yielding an index ranging from 0 to 60, with higher scores indicating a greater level of distress. Radloff (27) reported alpha coefficients of .85 for the general population and .90 for a group of patients with psychiatric disorders. A correlation (r) of .76 was obtained when the CES-D Scale was administered by a nurse and research clinician. (27) Test-retest reliability coefficients ranged from .4 to .7. (27,28) Low retest scores have been reported to be related to associating CES-D Scale items to recent symptoms. (27) Extensive support for validity has been reported. (26) Radloff (27) found correlations (r) of .44 to .56 with other scales of depression, and Weissman and colleagues (29) reported correlations (r) ranging from .49 to .85 with various measures of depression. A single question was used to assess adaptation to amputation and to the prosthesis. (21) A 5-point Likert scale, with anchors of "not at all adapted" and "completely adapted" at the ends of the scale, was used to indicate the degree of adaptation.

Outcome. The 16-item Activities-specific Balance Confidence (ABC) Scale (3) was used to determine balance confidence. Participants were asked to rate their level of confidence on a scale between 0% and 100% when performing a variety of activities, such as climbing stairs, reaching above the head, and walking on different surfaces. Responses are summed and then divided by 16 to provide an overall mean balance confidence score. An intraclass correlation coefficient (ICC) of .92 has been reported for 2-week test-retest reliability of measurements obtained with the ABC Scale. (3) More recently, Miller et al (30) reported a total score ICC of .91 and inter-item ICCs ranging from .53 to .87 for a sample of individuals with unilateral lower-limb amputation. Measurements obtained with the ABC Scale have been shown to correlate with those obtained with other measures of serf-efficacy (r=.49) and physical ability (r=.63) and to distinguish between groups of older adults with low and high mobility. (3,5) Further strong correlations with walk tests (r=.7) (31) and self-report measures of prosthetic function (r=.67-.82) (30) also have been reported.

Data Analysis

All continuous variables are presented as means and then changed into categorical-level variables to simplify univariate analysis and presentation of descriptive statistics. If the variables did not have a pre-established published cut point used to distinguish between levels of function, such as that established for the CES-D ([greater than or equal to] 16 suggests clinical depression), (27) then the variables were collapsed based on a statistical distribution. Tertiles were used for age, years since amputation, number of problems with the lower limb without the amputation, number of problems with the limb with the amputation, and prosthesis. The median value was used as a cut point to divide the social support data into those with higher and lower levels of support. Categorical variables such as marital status, education level, employment status, and mobility device used were collapsed into binary responses. Ordinal variables, such as adaptation to amputation and prosthesis, were collapsed into 2 groups to indicate whether the individual had achieved ("quite well adapted" to "completely well adapted") or had not achieved ("not at all adapted" to "moderately well adapted") a level of complete adaptation.

Statistical analyses included calculation of means and percentages for descriptive purposes, t tests to assess univariable differences between 2 groups, analyses of variance (ANOVAs) to assess differences among 3 or more groups, and multiple linear regression to examine multivariable relationships with the ABC Scale scores. The forward selection regression procedure was used to assess multivariable relationships, with P<.25 used for entry. All factors found to be statistically different (P<.25) using t tests and ANOVAs were included in the maximum model. Using a liberal probability value is recommended when the goal of regression analysis is to create a "reliable" group of variables that best predicts or describes a new outcome of interest. (32) Doing so produces a regression equation that may be inclined to increase the chance of a Type I error but reduces the chance of a Type II error or loss of an important independent variable that can describe the dependent variable. (32) Therefore, all variables found to be significant at P<.i that increased the adjusted multivariable coefficient of determination ([R.sup.2]) by at least 0.5% were retained in the final regression model. The exceptions were amputation level and amputation cause, both of which were kept in the model regardless of their statistical significance (32) because we think they are clinically important.

Most of the variables in this study had low missing value rates (<5%). To minimize loss of cases due to listwise deletion, missing values were replaced using multiple imputation. (33) In brief, this special form of Markov chain Monte Carlo technique is used to predict missing values for cases based on multiple simulations of available data. Essentially, multiple versions of the complete data set are generated, and the data are then allowed to converge based on the distribution of values. Multiple imputation was performed using NORM Version 2 for Windows 95/98/NT. (34) All other data management and analyses were conducted using SPSS Version 8 for Windows.

Results

The mean ABC Scale scores for each of the variables considered in the study are presented in Table 1. The mean ABC Scale score for the entire sample was 63.8 (SD=26.7); however, 35% of the sample scored 80 or better. As shown in Table 1, the ABC scores differed across levels of all variables with the exception of social support, amputation level, joint pain, and presence of a fall in the past 12 months. Patterns of mean ABC scores across levels of the variables in Table 1 are all as we expected except for employment status. We anticipated that respondents who worked would have a higher level of balance confidence than respondents who did not work.

The differences in ABC Scale scores between respondents with TF and TT amputations (4.01 points) and between respondents who had fallen in the past year and those who had not fallen (2.26 points) were not statistically significant. Both were unexpected findings.

Table 3 presents mean values for the 16 individual items of the ABC Scale for the total group as well as the mean difference between the subjects with amputations due to vascular reasons and those with amputations due to nonvascular reasons. Items are presented in rank order from most confident to least confident based on the mean score of the total group. The subjects who had amputations for nonvascular reasons reported higher levels of balance confidence than did the subjects whose amputations were due to vascular problems for all 16 items of the ABC Scale. Based on t tests, there were differences between the 2 groups for each item, and these differences remained statistically significant after adjusting the alpha level for multiple testing using the Bonferroni correction. (32) Large between-group differences ([greater than or equal to] 29 points) were observed for items such as walking in crowded areas, sweeping the floor, and reaching while up on their toes. Small differences between the 2 groups were observed for activities such as walking around the house, getting in and out of a car, and reaching at eye level.

Table 4 shows the results for the final regression model containing all of the variables that remained related for the study sample. As shown by the exclusion of 0 in the 95% confidence intervals, being younger, male, able to ambulate without a mobility device, and able to walk without concentrating and having fewer limitations in activities of daily living, fewer symptoms of depression, and no stated fear of falling were all independently related to balance confidence. Having a good to exceptional level of perceived health was independently related to balance confidence. Based on the standardized regression coefficients, mobility device use, fear of falling, and concentration while walking had the strongest relationship with balance confidence. The total variance accounted for by the regression equation was 67%, with fear of falling accounting for 4% of the explained variance.

Discussion

Studies of balance and postural sway consistently report variations in abilities between people with intact lower limbs and people with unilateral amputations. (35-37) Therefore, it seems plausible that decreased balance confidence may be important among people with amputations. Confidence in balance has been reported to be a better predictor of an individual's engagement in physical, daily, and social activities than actual measures of physical performance among elderly people (10) and is strongly correlated with prosthetic performance (what people do), prosthetic capability (what people can do), and social activity participation among people with amputations. (13) In our opinion, continued study of balance confidence among people with lower-limb amputations is important.

Myers et al (5) reported that physically active elderly people in good health had a total mean confidence score greater than 88 on the ABC Scale. In our study, individuals with amputations due to vascular and nonvascular causes had mean scores ([bar]X=54.1 and 74.7, respectively) lower than those of the sample of elderly people in good health in Myers and colleagues' study. Intervention, in the form of education, balance training, and activity, has been advocated for individuals who score below 80 on the ABC Scale. (5) This equates to at)out 81% of me respondents with amputations due to vascular causes and 46% of the respondents with amputations due to nonvascular causes in our study.

We expected that balance confidence would differ between people with amputations due to vascular and nonvascular causes as well as between people with TF and TT amputations. Differences between groups based on the cause of amputation were expected because individuals with vascular disease tend to be older, have more comorbidity, and use more medications. In addition, some studies (35-37) have suggested that people with amputations due to trauma perform better than people with amputations due to vascular causes in balance and postural sway. This expectation was verified in the bivariable analysis and further clarified in the multivariable analysis. The respondents with amputations due to vascular problems had lower balance confidence overall and for all activities measured. The differences were greatest for reaching while standing on a chair and using an escalator without holding the handrail. The difference was smallest for getting in and out of a car. Although fear of injury associated with falling from a chair or down a set of stairs may explain some of the difference, we believe the difference may more likely be related to the familiarity of the activity. Confidence in performing activities is likely to be higher in routine tasks that we frequently practice, such as transferring into a car or walking within a home. We believe a person's perceived capabilities are likely to determine which activities that individual will choose to perform. This may explain, in our view, why the differences in confidence between the respondents with amputations due to vascular causes and those with amputations due to nonvascular causes were twice as large for sweeping the floor than for walking outside to a nearby car. The older, more frail group of respondents with amputations due to vascular reasons did not perform some activities, especially those that they perceived were beyond their capability.

The level of amputation was not statistically related to balance confidence. This is surprising as we expected those respondents with a TF amputation to display behaviors consistent with lower confidence because of the loss of stability that is associated with the removal of both an ankle and a knee joint. Furthermore, lower balance confidence was anticipated given that prosthetic .joints do not provide sensory feedback. However, in both bivariable and multivariable analyses, amputation level was not associated with balance confidence (P>.05).

There are several possible explanations for our findings. The ABC Scale may not be valid for measurements from people with amputations, or it may not be sufficiently sensitive to detect clinically important differences between people with TF and TT amputations. Another possible explanation is that the ABC Scale can be used to measure balance confidence overall, but the measurements cannot be used to differentiate the 2 groups because the differences in balance confidence are too small. A difference between people with TT and TF amputations also may not have been found because the vast majority of people with TF amputations are people whose leg has been removed for vascular reasons. Although all subjects in our sample had an amputation, it is possible that we did not have a representative sample and thus selected a group of highly mobile individuals with TF amputations.

We combined individuals who had a Symes amputation with individuals who had a TT amputation. It is possible that including the 23 people who had a Symes amputation, the majority of whom (n=18) had amputations due to nonvascular problems, with the people with TT amputations may have skewed our findings. However, excluding individuals with a Symes amputation increased the overall TT mean ABC Scale score by less than 0.5 and therefore had a very small overall effect on our findings. Our rationale for combining these groups was based on our belief that a Symes amputation can be considered a long TT amputation. In both cases, the ankle is the major joint that is lost; therefore, the resulting loss of sensory feedback and ankle position sense in particular occurs at the same level. Moreover, both require a patella-tendon-bearing prosthetic limb. Finally, our clinical experience suggested that mobility between these 2 groups is very similar. As logical as it is to expect differences in balance confidence between individuals with and without knee joints, it may be that adaptation to the loss of a knee joint in terms of balance confidence is equal in these populations.

Fear of falling was an important factor explaining the variance in balance confidence. We contend that the relationship between fear of falling and balance confidence is not easily explained. Self-efficacy scales such as the ABC Scale were developed to provide a measure of fear of falling that is responsive, in part, by reducing perceived stigma, especially among men, often associated with admitting one has a "fear." (3,6) Given the similarity between the fear of falling and balance confidence constructs, it may be unreasonable to expect that the entire relationship would be explained by the variables measured in the study.

In a previous study, (17) we found that having a fall in the past 12 months remained a risk factor for fear of falling among people with lower-limb amputations. This finding suggests that past experience may not be necessary to alter balance confidence. (4,10) In his seminal work, Bandura (10) suggested that vicarious experience and verbal persuasion may influence self-efficacy. Translated for our study group, when people with amputations talk with other people who have had amputations who have fallen or had a near fall, this also may elicit decreased confidence. Furthermore, other people with well-meaning comments such as "you shouldn't go out right now because the sidewalks are wet and icy" may inadvertently reinforce decreased confidence. We believe that those who do not believe they can perform certain activities are more likely to avoid them and, therefore, less likely to fall. Ultimately, we contend, the individual's appraisal may change from being adaptive and avoiding hazardous activities, such as climbing on a chair to reach for something, to becoming maladaptive. People's fear may prevent them from doing activities within their capabilities, which may result in deconditioning and muscle atrophy. These results, in turn, may increase the likelihood of falls. Clinical trials assessing the effectiveness of interventions, such as education and strengthening programs, to decrease fear of falling and improve balance confidence and social activity among elderly people have shown modestly promising results (14,38) and, in our opinion, are worthy of study among people who have a lower-extremity amputation.

Our study had several limitations. Despite the fact that we used only questions and scales in our survey that had been used in previous published studies, the psychometric properties of some of these variables are unknown, and we did not determine reliability and validity for all of the measures we used. Because the data are primarily cross-sectional, claims of a temporal or causal relationship cannot be made. Variables such as falling in the 12 months prior to the study required the respondents to rely on their memory, and this can be susceptible to recall bias. We chose to assess the 12 months prior to the study because research into recall bias for identifying falls suggests this period of time is more reliable than periods of 3 or 6 months. (39) Other authors (40) have suggested that falls occurring more than 12 months in the past may still undermine balance confidence. Therefore, asking whether a person has ever fallen since receiving his or her prosthesis might have provided better information. Other variables, such as the presence of peripheral neuropathy, which is highly prevalent among diabetic- and nondiabetic-related vascular amputations, (41) were not measured due to the study design. Given the altered sensation associated with peripheral neuropathy, it is plausible that this variable contributed to a reduced sense of balance confidence and should be included in future studies of this population. Using a prospective-longitudinal design would overcome these limitations.

Although we collected information from both clinics, we assumed that all individuals had an annual follow-up visit. It is uncertain, however, what proportion of active prosthetic limb users did not attend clinic during the survey year. Despite our response rate (77%) and the fact that there were no differences between respondents and nonrespondents, we believe that replication of our study is needed to verify the magnitude of balance confidence and ensure model formation is robust with other populations of people with amputations.

Summary

Our results suggest that people with unilateral lower-limb amputations have low balance confidence and that the balance confidence is lower among individuals who had amputations due to vascular causes. Moreover, the respondents with amputations due to vascular problems consistently scored lower in balance confidence for each item of the ABC Scale. Preliminary study of balance confidence in this population demonstrated that a strong correlation existed among lower balance confidence scores, reduced prosthetic mobility and capability, and reduced participation in social activities, even after controlling for other important variables. (13) If this relationship can be found in longitudinal studies, we believe intervention trials similar to those conducted among the elderly population are warranted. Given the considerable cost of prosthetic rehabilitation (42) and the potential for further development of impairment--such as loss of muscle strength, endurance, and balance--that accompany inactivity, improving an individual's balance confidence may be one additional method of maximizing the quality of life after amputation.

Table 1.
Descriptive Statistics and Mean Activities-Specific Balance Confidence
(ABC) Scale Scores for the Total Sample (N=435) (a)

Socio-demographic                                      Mean ABC
Factors                                  %             Scale Score

Age (y) ([bar]X [+ or -]SD) (b)          62.0 (15.7)
  23-55                                  33.1          74.93
  56-70                                  31.7          63.94
  [greater than or equal to] 71          35.2          53.29

Sex (b)
  Male                                   71.0          67.74
  Female                                 29.0          54.45

Marital status (b)
  Married                                62.1          59.49
  Not married                            37.9          66.49

Social support                           15.1 (3.2)
  < 16 (median)                          49.7          60.53
  [greater than or equal to] 16          50.3          67.09

Education (b)
  < grade 12                             57.7          56.92
  [greater than or equal to] grade 12    42.3          73.27

Employment status (b)
  Working (full-time/part-time)          25.5          59.00
  Not working                            74.5          65.50

Income (b)
  $0-$19,999                             38.9          57.33
  $20,000-$39,999                        33.1          63.17
  [greater than or equal to] $40,000     27.1          73.97

Amputation-Related                                     Mean ABC
Factors                                  %             Scale Score

Years since amputation (b)               14.3 (16.5)
  0-3                                    31.0          56.08
  4-13                                   35.2          61.29
  [greater than or euqal to] 14          33.8          73.59

Amputation cause (b)
  Vascular (n=230)                       52.9          54.13
  Nonvascular                            47.1          74.72

Amputation level
  TT (n=313)                             73.3          64.90
  TF                                     26.7          60.89

Mobility device used inside (b)
  No                                     43.4          78.38
  Yes                                    56.6          44.89

Automatic walking ability (b)
  No                                     40.9          44.21
  Yes                                    59.1          77.42

Health-Related                                         Mean ABC
Factors                                  %             Scale Score

Comorbidity (b)                          2.7 (2.3)
  0                                      20.7          73.58
  1                                      17.0          72.29
  [greater than or equal to] 2           62.3          58.28

Joint pain
  No                                     70.3          65.13
  Yes                                    29.7          60.74

Intact leg problems (b)                  1.0 (1.0)
  0                                      41.1          70.11
  1-2                                    31.7          59.62
  3-4                                    27.1          59.23

Fall in past 12 mo
  No                                     52.4          65.02
  Yes                                    47.6          62.76

Fall injury (b)
  No                                     80.2          65.22
  Yes                                    19.8          58.19

No. of medications (b)                    1.9 (2.0)
  0                                      35.2          71.24
  1                                      17.7          70.26
  [greater than or equal to] 2           47.1          55.89

Alcohol intake (b)
  None                                   63.4          61.37
  Occasional                             18.9          68.71
  Daily                                  17.7          67.45

Perceived health (b)
  Excellent                               9.4          85.89
  Very good                              21.4          72.90
  Good                                   38.4          63.50
  Fair                                   26.9          52.39
  Poor                                    3.9          42.96

ADL limitation (b)
  No ADL limitation                      73.6          70.51
  [greater than or equal to]
    1 ADL limitations                    26.4          45.25

Psychological                                          Mean ABC
Factors                                  %             Scale Score

Depression (CES-D) (b)                   10.5 (10.6)
  < 16                                   76.7          67.98
  [greater than or equal to] 16          23.3          50.95

Adaptation to amputation (b)
  No                                     18.4          44.34
  Yes                                    81.6          68.22

Adaptation to prosthesis (b)
  No                                     21.4          42.78
  Yes                                    78.6          69.56

Fear of falling (b)
  No                                     50.8          77.4
  Yes                                    49.2          49.78

(a) TT=transtibial, TF=transfemoral, ADL=activities of daily living,
CES-D=Center for Epidemiologic Studies Depression Scale. Values in
parentheses are standard deviations.

(b) All subgroup means significantly different at P <.05.
Table 2.
Classification of vascular and nonvascular etiology of amputation.

Vascular                      Nonvascular

Peripheral Vascular Disease   Cancer
Diabetes                      Congenital Malformation
Vascularitis                  Trauma
Infection Secondary to        Infection Secondary to
  Vascular Disease              Trauma
Table 3.
Mean Item Activities-Specific Balance Confidence (ABC) Scale Scores for
Total Sample and for Respondents With Amputations Due to Vascular and
Nonvascular Causes

                           Total
                           Sample        Vascular      Nonvascular
                           (N=435)       Amputations   Amputations (a)
Item                     [bar]X   SD     (n=230)       (n=205)

 4. Reach at eye level   86.2     24.9    80.6         92.5
 9. Get in/out of car    83.9     24.3    79.4         88.9
 1. Walk around house    81.7     25.5    76.5         87.5
 8. Walk outside to
    nearby car           81.6     26.6    75.3         88.7
 3. Pick up slipper
    from floor           75.9     31.7    68.1         84.7
10. Walk across
    parking lot          74.2     32.5    65.7         83.8
 7. Sweep the floor      69.9     37.3    56.6         84.9
 2. Up and down stairs   69.3     32.5    62.9         76.4
12. Walk in
    crowded mall         63.6     36.8    52.1         76.6
11. Up and down ramp     62.0     34.1    53.4         71.6
14. Escalator
    holding rail         60.1     40.4    47.9         73.8
13. Walk in
    crowd/bumped         55.7     37.4    42.3         70.7
 5. Reach on toes        50.7     40.9    37.3         65.6
 6. Stand on chair
    to reach             39.1     40.3    22.4         57.5
15. Escalator not
    holding rail         38.6     39.8    24.9         54.0
16. Walk on
    icy sidewalks        28.9     32.4    20.6         38.3

Total ABC Scale score    63.8     26.7    54.1         74.7

(a) Difference in means between respondents with amputations due to
vascular and nonvascular causes, P <.001.
Table 4.
Regression Model of Balance Confidence for Individuals With Transtibial
and Transfemoral Lower-Limb Amputations (a)

Factor                     [beta]   b         SE      95% CI

Age                        -.111     -0.188   0.056    -0.299, -0.078
Sex                         .092      5.390   1.714     2.022, 8.759
Nonvascular amputation      .091      4.874   1.790     1.356, 8.392
Amputation level (TF)      -.036     -2.180   1.768    -5.656, 1.295
Perceived health            .064      1.688   0.865    -0.011, 3.388
Mobility device use         .308     16.557   1.836    12.947, 20.166
Concentrating on walking    .229     12.447   1.905     8.702, 16.192
ADL limitation              .114      3.123   0.859     1.435, 4.812
Depression (CES-D)         -.097     -0.243   0.081    -0.402, -0.085
Fear of falling            -.248    -13.249   1.723   -16.637, -9.862
[R.sup.2]                   .665

(a) b=unstandardized regression coefficient, SE=standard error,
CI=confidence interval, TF=transfemoral, ADL=activities of daily
living, CES-D=Center for Epidemiologic Studies Depression Scale.

All authors provided concept/idea/research design. Dr Miller and Dr Speechley provided writing and data analysis. Dr Miller provided data collection and project management. Dr Deathe provided subjects, institutional liaisons, and consultation (including review of manuscript before submission). The authors thank Dr Mark Bayley and Ms Susan Brown for their assistance with subject recruitment, Dr Susan Harris for reviewing an early version of the manuscript, and all subjects who participated in the study.

This study was approved by the Research Ethics Board for the Review of Health Sciences Research Involving Human Subjects at the University of Western Ontario.

This article was submitted May 3, 2001, and was accepted March 19, 2002.

References

(1) Butland RJA, Pang J, Gross ER, et al. Two-, six-, and 12-minute walking test in respiratory disease. Br Med J (Clin Res Ed). 1982;284: 1607-1608.

(2) Schoppen T, Boonstra A, Groothoff JW, et al. The timed "Up and Go" test: reliability and validity in persons with unilateral lower limb amputation. Arch Phys Med Rehabil. 1999;80:825-828.

(3) Powell LE, Myers AM. The Activities-specific Confidence (ABC) Scale. J Gerontol A Biol Sci Med Sci. 1995;50:M28-M34.

(4) Myers AM, Powell LE, Maki BE, et al. Psychological indicators of balance confidence: relationship to actual and perceived abilities. J Gerontol A Biol Sci Med Sci. 1996;51:M37-M43.

(5) Myers AM, Fletcher PC, Myers AH, Sherk W. Discriminative and evaluative properties of the Activities-Specific Balance Confidence (ABC) Scale. J Gerontol. 1998;53:M287-M294.

(6) Tinetti ME, Richman D, Powell LE. Falls efficacy as a measure of fear of falling. J Gerontol. 1990;45:P239-P243.

(7) O'Loughlin JL, Robitaille Y, Boivin J, Suissa S. Incidence of and risk factors for falls and injurious falls among the community-dwelling elderly. Am J Epidemiol. 1993;137:342-354.

(8) Tinetti ME, Speechley M. Prevention of falls among the elderly. N Engl J Med. 1989;320:1055-1059.

(9) Tinetti ME, Speechley M, Ginter SF. Risk factors for falls among elderly persons living in the community. N Engl J Med. 1988;319: 1701-1707.

(10) Bandura A. Self-efficacy mechanism human agency. Am Psychol. 1982;37:122-147.

(11) Maki BE, Holliday PJ, Topper AK. Fear of falling and postural performance in the elderly. J Gerontol. 1991;46:M123-M131.

(12) Tinetti ME, Mendes deLeon CF, Doucette JT, Baker DI. Fear of falling and fall-related efficacy in relationship to functioning among community-living elders. J Gerontol. 1994;49:M140-M147.

(13) Miller WC, Speechley M, Deathe AB, Koval J. The influence of falling, fear of falling, and balance confidence on prosthetic mobility and social activity among individuals with a lower extremity amputation. Arch Phys Med Rehabil. 2001;82:1238-1244.

(14) Tennstedt S, Howland J, Lachman M, et al. A randomized, controlled trial of a group intervention to reduce fear of falling and associated activity restriction in older adults. J Gerontol B Psychol Sci Soc Sci. 1998;53:P384-P392.

(15) Tinetti ME, Powell L. Fear of falling and low self-efficacy: a cause of dependence in elderly persons. Gerontology. 1993;48:25-38.

(16) De Frang RD, Taylor L, Porter JM. Basic data related to amputations. Ann Vasc Surg. 1991;5:202-207.

(17) Miller WC, Deathe AB, Speechley M. The prevalence and risk factors of falling and fear of falling among individuals with lower extremity amputation. Arch Phys Med Rehabil. 2001;82:1031-1037.

(18) Dillman DA. Mail and Telephone Surveys: The Total Design Method. New York, NY: John Wiley & Sons Inc; 1978.

(19) Cohen S, Mermelstein R, Kamarck T, Hoberman HN. Measuring the functional components of social support. In: Sarason I, Sarason B, eds. Social Support: Theory, Research, and Applications. Dordrecht, the Netherlands: Martinus Nijhoff; 1987:73-94.

(20) Schulz R, Williamson GM. A 2-year longitudinal study of depression among Alzheimer's caregivers. Psychol Aging. 1991;6:569-578.

(21) Grise MCL, Gauthier-Gagnon C, Martineau GG. Prosthetic profile of people with a lower extremity amputation: conception and design of a follow-up questionnaire. Arch Phys Med Rehabil. 1993;74:862-870.

(22) Ontario Health Survey Users' Guide: Documentation. Toronto, Ontario, Canada: Ontario Ministry of Health; 1992.

(23) Disablement and Chronic Health Problems in Ontario: Working Paper No. 5. Toronto, Ontario, Canada: Ontario Ministry of Health; 1993.

(24) Badley EM, Rasooly I, Webster GK. Relative importance of musculoskeletal disorders as a cause of chronic health problems, disability, and health care utilization: findings from the 1990 Ontario Health Survey. J Rheumatol. 1994;21:505-514.

(25) Gompertz P, Pound P, Ebrahim S. A postal version of the Barthel Index. Clin Rehabil. 1994;8:233-239.

(26) McDowell I, Newell C. Measuring Health: A Guide to Rating Scales and Questionnaires. 2nd ed. New York, NY: Oxford University Press; 1996.

(27) Radloff LS. The CES-D scale: a self-report depression scale for research in the general population. Appl Psychol Meas. 1977;1:385-401.

(28) Roberts RE. Reliability of CES-D Scale in different ethnic contexts. Psychiatry Res. 1980;2:125-134.

(29) Weissman MM, Sholomskas D, Pottenger M, et al. Assessing depressive symptoms in five psychiatric populations: a validation study. Am J Epidemiol. 1977; 106:203-214.

(30) Miller WC, Deathe AB, Speechley M. Psychometric properties of the Activities-specific Balance Confidence Scale among individuals with a lower limb amputation. Arch Phys Med Rehabil. In press.

(31) Miller WC, Deathe AB, Speechley M. Lower extremity prosthetic mobility: comparison of 3 self-report scales. Arch Phys Med Rehabil. 2001;82:1432-1440.

(32) Kleinbaum DG, Kupper LL, Muller KE, Nizam A. Applied Regression Analysis and Other Multivariable Methods. 3rd ed. Belmont, Calif: Duxbury; 1998.

(33) Schafer JL. Analysis of Incomplete Multivariate Data. New York, NY: Chapman & Hall; 1997.

(34) Schafer JL. NORM: multiple imputation of incomplete multivariate data under a normal model [computer program for Windows 95/98/NT]. Version 2. Available from: http://www.stat.psu.edu/~jls/misoftwa.html; 1999.

(35) Fernie GR, Holliday PJ. Postural sway in amputees and normal subjects. J Bone Joint Surg Am. 1978;60:895-898.

(36) Hermodsson Y, Ekadahl C, Persson BM, Roxendal G. Standing balance in trans-tibial amputees following vascular disease or trauma: a comparative study. Prosthet Orthot Int. 1994; 18:150-158.

(37) Isakov E, Mizrahi J, Ring H, et al. Standing sway and weight-bearing distribution in people with below-knee amputations. Arch Phys Med Rehabil. 1992;73:174-178.

(38) Reinsch S, MacRae P, Lachenbruch PA, Tobis J. Attempts to prevent falls and injury: a prospective community study. Gerontologist. 1992;32: 450-456.

(39) Cummings SR, Nevitt MC, Kidd S. Forgetting falls: the limited accuracy of recall of falls in the elderly. J Am Geriatr Soc. 1988;36: 613-616.

(40) Fessel KD, Nevitt MC. Correlates of fear of falling and activity limitation among person with rheumatoid arthritis. Arthritis Care Res. 1997;10:222-228.

(41) Potter PJ, Maryniak O, Yaworski R, Jones IC. Incidence of peripheral neuropathy in the contralateral limb of persons with unilateral amputation due to diabetes. J Rehabil Res Dev. 1998;35:335-339.

(42) Calle-Pascual AL, Redondo MJ, Ballesteros M, et al. Nontraumatic lower extremity amputations in diabetic and non-diabetic subjects in Madrid, Spain. Diabetes Metab. 1997;23:519-523.

WC Miller, PhD, MSC(OT), is Assistant Professor, Faculty of Medicine, School of Rehabilitation Sciences, University of' British Columbia, T325 Third Floor, Koerner Pavilion, 2211 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 2B5 ([e-mail]). Address all correspondence to Dr Miller.

M Speechley, PhD, is Associate Professor, Faculty of Medicine and Dentistry, Department of Epidemiology and Biostatistics, University of Western Ontario, London, Ontario, Canada.

AB Deathe, MD (FRCPC), is Associate Professor, Department of Physical Medicine and Rehabilitation, University of Western Ontario, and Medical Director, Amputee Program, St Joseph's Health Care London, London, Ontario, Canada.