Volume 90, Issue 1 , Pages 74-81, January 2009
Determinants of Skin Problems of the Stump in Lower-Limb Amputees
Article Outline
Abstract
Meulenbelt HE, Geertzen JH, Jonkman MF, Dijkstra PU. Determinants of skin problems of the stump in lower-limb amputees.
Objective
To identify determinants of skin problems in lower-limb amputees.
Design
Survey, using a questionnaire.
Setting
Not applicable.
Participants
Lower-limb amputees (N=2039) who either obtained their prosthesis through the Orthopedische Instrument Makerij (a group of orthopedic workshops in the Netherlands) or were a member of the (Dutch) National Society of Amputees (Landelijke Vereniging van Geamputeerden) were invited to participate. In total, 872 lower-limb amputees agreed to participate.
Intervention
Amputees filled in the questionnaire to assess characteristics of the amputation and prosthesis, level of activity, stump and prosthesis hygiene, and skin problems. Stepwise backward logistic regression was performed to analyze determinants of skin problems.
Main Outcome Measure
Skin problems in the month prior to completing the questionnaire.
Results
A total of 816 questionnaires were received. Eventually 805 questionnaires were suitable for statistical analysis. Protective determinants were (in order of magnitude of association) older age, male sex, and amputation because of peripheral arterial disease and/or diabetes. Provocative determinants were (in order of magnitude of association) use of antibacterial soap, smoking, and washing the stump 4 times a week or more often. In total, 63% of the participants (95% confidence interval, 60%–67%) reported 1 or more skin problems.
Conclusions
The provocative determinants identified in this study—use of antibacterial soap, smoking, and stump washing frequency—have to be studied for their clinical relevance.
Key Words: Amputees, Questionnaires, Rehabilitation, Skin, Skin diseases
List of Abbreviations: CI, confidence interval, OR, odds ratio
THE SKIN OF THE STUMP in lower-limb amputees is prone to problems because it is exposed to several unnatural circumstances when a prosthesis is used. These unnatural circumstances include shear and stress forces, increased moisture, and prolonged moist exposure to the chemical compounds of the prosthesis.1 As a consequence, various skin problems may develop. These skin problems and their management have been reviewed extensively in the literature.2, 3, 4, 5, 6, 7 Besides these reviews, developments in knowledge of pathophysiology and treatment are presented by means of case reports.1 In a systematic review,8 with the purpose of evaluating reported incidence and prevalence of skin problems in lower-limb amputees, 28 clinical studies and patient surveys were identified for methodologic assessment. Only 1 study of acceptable methodologic quality was identified. It reported a prevalence of skin problems of 16% (95% CI, 7%–28%) in a small group (n=47) of lower-limb amputees (age ≥65y). All amputees visited an artificial limb unit in Singapore because of complications of the stump, fitting of a prosthesis, or prosthesis repair.9 Other studies identified in the systematic review had methodologic shortcomings concerning sampling method, study population, and assessment method.8
Although several determinants causing skin problems have been suggested, including reason for amputation, present comorbidity, prosthesis fit, prosthesis characteristics (including chemical compounds), level of hygiene, and activity level of the amputee7, 10; poor prosthetic fit, poor hygiene, or both11; age, pathology, activity level, socket fit, biomechanics, and wearing patterns12; and mechanical factors,13 only a minority of these suggested determinants actually appeared to have a relationship with skin problems.
In the study by Dudek et al,14 4 determinants were identified that increased the odds of having a skin problem: transtibial level of amputation compared with other levels of amputation, being employed or unemployed compared with being retired, use of a single-point cane or no walking aid compared with another type of walking aid, and not having peripheral arterial disease. No other studies are available evaluating determinants of skin problems of the stump in lower-limb amputees. The aim of this study was to identify determinants of skin problems of the stump in lower-limb amputees.
Methods
A survey was performed using a (self-developed) questionnaire that assessed the determinants suggested in the literature, and skin problems that may have occurred.
The questionnaire consisted of a series of open questions and multiple choice questions. The following domains were assessed: demographics, characteristics of the amputation and prosthesis, activity level of the amputee, stump and prosthesis hygiene, and skin problems. The characteristics of and determinants assessed by the questionnaire are summarized in appendix 1. The time window chosen to report a skin problem was the last month prior to completing the questionnaire.
Subjects
Lower-limb amputees who received their prosthesis through the OIM (a group of orthopedic workshops) or were a member of the (Dutch) National Society of Amputees (LVvG) were invited to participate, using the opting-out method. These subjects represent 25% of the total Dutch population of lower-limb amputees who have a prosthesis. All potential participants were sent a letter in which they were invited to participate. If persons wanted to participate, they could send back a signed form with their names and addresses (which accounted for informed consent). If potential participants did not want to participate, they were asked to send the form back with information concerning sex and date of birth to facilitate a comparison between participants and nonparticipants. Participants received the questionnaire at the address they provided; they could return the questionnaire using a prepaid envelope. Questionnaires with missing data were completed by either contacting the participant by telephone or by sending the questionnaire again, with the missing questions highlighted and a request to fill in these questions. When the questionnaire was not returned at all, participants received a reminder either by telephone or, if no telephone number was available, by letter.
Data Entry
Data of the questionnaire were entered into a database. If a participant was not able to fill in the exact date of amputation, the following procedure was performed. If the day of the month was missing, the 15th of that month was entered as the date of amputation. If the month was missing, the first of July of that year was entered as the date of amputation. All participants were able to report at least the year of amputation. All data were checked manually for correct data entry.
Regarding the participants who reported more than 1 reason for amputation (n=79), the following procedure was used. When more than 1 reason for amputation was reported (ie, trauma and infection or diabetes and infection), the most logical reason based on pathophysiology was chosen as main reason for amputation and entered into the database (n=36). For instance, for a participant who endured a trauma and subsequently developed an infection, trauma was entered as reason for amputation. Because of similarities in pathophysiology, peripheral arterial disease and diabetes were entered as 1 reason for amputation in the database.
Regarding the participants who reported having a bilateral amputation (n=55), the following procedure was used. When a similar level of amputation was reported (n=42), it was verified if 1 amputation side on which skin problems were most frequent was reported. If so, that side was used for statistical analysis (n=11). When a participant reported similar skin problems on both sides, 1 side was randomly chosen for the analysis (n=15). When no side of skin problems was reported (n=16), data were checked if the participant reported occurrence of skin problems in the past or in the month prior to completing the questionnaire. If no skin problems were reported at all, 1 side was randomly chosen for statistical analysis (n=12). If skin problems had been reported but the participant had not reported a side on which the problems occurred, the questionnaire was not used for statistical analysis (n=4). Of participants with a different level of amputation (n=13), 7 did not report on which side they had the most skin problems. These 7 questionnaires were not used for statistical analysis.
As a result, 11 questionnaires were excluded for analysis, and 805 questionnaires were used for statistical analysis.
Statistical Analysis
Statistical analysis was performed using SPSS 14.0.a The determinants analyzed for an association with skin problems in the month prior to completing the questionnaire were age; sex; time since amputation; reason for amputation (peripheral arterial disease/diabetes, trauma, oncology, infection, congenital, and other); level of amputation (transtibial, knee-exarticulation, transfemoral, amputation at level of the hip or above); having a bilateral amputation; average distance walked outdoors during a day with prosthesis; percentage use of prosthesis indoors; hours a day the prosthesis is worn; having a liner; use of additional materials between stump and socket or liner; use of walking aids (unilateral or bilateral); existence of comorbidity (cardiac diseases, peripheral arterial disease, rheumatoid arthritis, artrosis, kidney problems, pulmonary problems, and other); frequency of washing stump, liner (when having a liner), and stump sockets (when having stump sockets); type of soap used for washing; performing sports with prosthesis; smoking; and whether the participant had employment. On the basis of the symptoms reported by the amputees, 2 dermatologists independently classified the symptoms into 4 additional outcome measures: suspicion for eczema, suspicion for mechanically induced skin problems, suspicion for skin problems caused by occlusion, and suspicion for skin problems caused by peripheral arterial disease. An amputee had to report at least 1 symptom related to an outcome measure to be identified as suspicious for that outcome measure. Although all additional outcome measures are therefore suspicious, to enhance readability the term suspicious will not be used in the rest of the article. The criteria used to classify the outcome measures are summarized in appendix 2.
Determinants significantly associated with 1 of the 5 outcome measures were initially identified by means of chi-square analysis for dichotomous or ordinal data and independent sample t tests for interval data. The determinants significantly related to 1 of the outcome measures were tested for multicolinearity. Thereafter, for each outcome measure, the determinants identified were entered stepwise backward (likelihood ratio) in a multivariate logistic regression analysis. If an identified determinant was ordinal, it was dichotomized for the analysis (meaning the items of the determinant were divided into 2 groups, so the determinant was either present or absent in a participant) so it could be entered in the analysis. To optimize the intercept of the models, the age was adjusted by subtracting 60 years from the age of the amputee.
Results
Participant Characteristics
In total, 2039 amputees were invited to participate (the total number of amputees was initially 2142, but some amputees got both an invitation through the OIM and the LVvG). Of the 1082 amputees who responded, 872 stated they wanted to participate. Eventually 816 complete questionnaires (40%) were obtained. After data entry was completed, 805 questionnaires were available for statistical analysis.
Participants were significantly younger (60±15y, P<.001) than nonparticipants (70±14y). Sex distribution was the same in participants and nonparticipants (62% men).
In table 1, descriptive statistics of participants are summarized. The most common levels of amputation were transtibial (49%) and transfemoral (30%). The most common reasons for amputation were trauma (42%) and peripheral arterial disease/diabetes (28%). Of the amputees, 30% were employed. Most amputees (61%) walked less than 500m/d. Half of the amputees used a liner in their prosthesis.
Table 1. Descriptive Statistics About All Participants and Those With and Without Skin Problems
| Characteristics | All Participants (n=805) | Skin Problems⁎ (n=507) | No Skin Problems⁎ (n=298) |
|---|---|---|---|
| Mean age ± SD (y) | 60±15 | 58±15 | 63±14 |
| Mean time ± SD since amputation (y) | 20±19 | 20±18 | 19±19 |
| No. (%)† | No. (%)† | No. (%)† | |
|---|---|---|---|
| Sex | |||
 Men | 498(62) | 298(59) | 200(67) |
| Women | 307(38) | 209(41) | 98(33) |
| Amputation level | |||
| Transtibial | 410(49) | 249(49) | 161(54) |
| Knee exarticulation | 91(12) | 54(11) | 37(12) |
| Transfemoral | 239(30) | 163(32) | 76(26) |
| Hip/pelvis | 21(3) | 11(2) | 10(3) |
| Bilateral | 44(6) | 30(6) | 14(5) |
| Reason for amputation | |||
| Peripheral arterial disease/diabetes | 225(28) | 117(23) | 108(36) |
| Trauma | 336(42) | 225(43) | 111(37) |
| Oncology | 109(13) | 75(15) | 34(13) |
| Congenital | 29(4) | 22(4) | 7(2) |
| Infection | 46(6) | 27(5) | 19(6) |
| Other | 60(7) | 41(8) | 19(6) |
| Comorbidity | 377(47) | 240(47) | 137(46) |
| Smoking | 202(25) | 141(28) | 61(20) |
| Employment | 242(30) | 170(34) | 72(24) |
| Walking aids | 467(58) | 303(60) | 164(55) |
| Walking distance | |||
| 0–100m/d | 212(26) | 131(26) | 81(27) |
| 100–200m/d | 123(15) | 88(17) | 35(12) |
| 200–500m/d | 158(20) | 91(18) | 67(23) |
| 500–1000m/d | 137(17) | 86(17) | 51(17) |
| >1000m/d | 175(22) | 111(22) | 64(21) |
| Use of liner | 402(50) | 252(50) | 150(50) |
| Sports with prosthesis | 182(23) | 118(23) | 64(21) |
| Frequency washing stump | |||
| 0–4 times/wk | 215(27) | 115(23) | 100(34) |
| 4 times/wk or more | 590(73) | 392(77) | 198(66) |
| % Use prosthesis indoors | |||
| 0% to 50% | 192(24) | 119(23) | 73(25) |
| 50% to 100% | 613(76) | 388(77) | 225(75) |
| Hours a day prosthesis is worn | |||
| 0–8h/d | 126(16) | 79(16) | 47(16) |
| ≥8h/d | 679(84) | 428(84) | 251(84) |
| Skin problems in period of more than 1 mo prior to completing the questionnaire | 657(82) | 476(94) | 181(60) |
⁎In the month prior to completing the questionnaire. |
†Percentages are column percentages. |
One or more skin problems in the month prior to completing the questionnaire were reported by 63% of the amputees (95% CI, 60%–67%). Of these amputees, 25% (95% CI, 21%–29%) wore the prosthesis less frequently because of those skin problems. The distribution of reported symptoms is summarized in table 2. The most frequently reported skin problems were profuse sweating (32%), redness of skin persisting more than 1 minute after removing the prosthesis (29%), and sensitive skin (23%).
Table 2. Skin Problems Reported in the Month Prior to Completing the Questionnaire
| Skin Problem Suspicious For⁎ | No. (%)‡ |
|---|---|
| Eczema | 404(50) |
| Sensitive skin† | 183(23) |
| Itching skin† | 144(18) |
| Redness of skin persisting more than 1 minute after removing prosthesis | 235(29) |
| Crusts | 41(5) |
| Mechanically induced skin problems | 346(43) |
| Blisters | 150(19) |
| Crusts | 41(5) |
| Corn/callus | 117(15) |
| Abrasion | 120(15) |
| Existing wound | 39(5) |
| Mechanical problems | 30(4) |
| Skin problems caused by occlusion | 412(51) |
| Profuse sweating | 256(32) |
| Warm skin | 66(8) |
| Pimples | 139(17) |
| Sensitive skin† | 183(23) |
| Itching skin† | 144(18) |
| Skin problems caused by peripheral arterial disease | 119(15) |
| Cold skin | 65(8) |
| White/blue skin | 77(10) |
| Problems mentioned that were not used for the outcome measures | |
| Prickly skin† | 77(10) |
| Painful skin† | 124(15) |
| Swelling | 78(10) |
| Infection | 10(1) |
| Other | 29(4) |
⁎A participant could mention more than 1 skin problem. |
†These problems were assessed using a 4-point rating scale (none, light, moderate, severe), which was dichotomized (none/light=absent, moderate/severe=present). |
‡Percentages are of the total group of participants. |
Skin problems in the period more than 1 month prior to completing the questionnaire were reported by 82% (95% CI, 79%–84%) of the amputees. The distribution of these problems is summarized in table 3. Most reported skin problems were pressure ulcers (57%) and infection (35%). Of these amputees, 57% (95% CI, 53%–60%) stated they could not wear the prosthesis temporarily because of the skin problems.
Table 3. Skin Problems Reported More Than 1 Month Prior to Completing the Questionnaire
| Type of Problem⁎ | No. (%)† |
|---|---|
| Eczema | 93(12) |
| Psoriasis | 12(2) |
| Infection | 279(35) |
| Pressure ulcer | 463(57) |
| Wounds | 246(31) |
| Mechanical complaints | 57(7) |
| Blisters | 67(8) |
| Other | 72(9) |
⁎A participant could mention more than 1 skin problem. |
†Percentages are of the total group of participants. |
Logistic Regression Analysis
The results of the logistic regression analysis are summarized in table 4. The identified determinants are labeled protective (if they were associated with a decreased risk for skin problems) or provocative (if they were associated with an increased risk for a skin problem). Higher age was a protective determinant in all outcome measures (skin problem in previous month, OR=.985; eczema, OR=.988; skin problems caused by peripheral arterial disease, OR=.977; mechanically induced skin problems, OR=.986; and skin problems caused by occlusion, OR=.975). Male sex was a protective determinant in skin problems in general (OR=.702), eczema (OR=.701), and skin problems caused by occlusion (OR=.628). Peripheral arterial disease and/or diabetes as reason for amputation was a protective determinant in skin problems in general (OR=.653) and eczema (OR=.562). The use of a prosthesis indoors more than 8 hours a day was a protective determinant in case of skin problems caused by peripheral arterial disease (OR=.577).
Table 4. Logistic Regression Models of Outcome Measures
| Determinants (and Coding) | β | OR | 95% CI of the OR |
|---|---|---|---|
| Dependent: Skin Problems in Previous Month (yes/no) | 0.336 | 1.399 | 0.915–2.141 |
| Constant | 0.336 | 1.399 | 0.915–2.141 |
| Age – 60 (per y) | −0.015 | 0.985⁎ | 0.974–0.996 |
| Sex (man=1, woman=0) | −0.354 | 0.702⁎ | 0.511–0.964 |
| Reason amputation peripheral arterial disease/diabetes (yes=1, no=0) | −0.426 | 0.653⁎ | 0.429–0.994 |
| Frequency of washing stump (4 times/wk or more=1, less than 4 times/wk=0) | 0.346 | 1.413⁎ | 1.010–1.976 |
| Use of antibacterial soap (yes=1, no=0) | 0.584 | 1.794⁎ | 1.159–2.777 |
| Smoking (yes=1, no=0) | 0.458 | 1.581⁎ | 1.098–2.277 |
| Dependent: eczema (yes/no) | |||
| Constant | 0.127 | 1.135 | 0.636–2.028 |
| Age – 60 (per y) | −0.012 | 0.988⁎ | 0.977–0.999 |
| Sex (man=1, woman=0) | −0.355 | 0.701⁎ | 0.520–0.945 |
| Reason for amputation peripheral arterial disease/diabetes (yes=1, no=0) | −0.577 | 0.562⁎ | 0.393–0.803 |
| Use of walking aids (yes=1, no=0) | 0.392 | 1.479⁎ | 1.077–2.033 |
| Dependent: peripheral arterial disease (yes/no) | |||
| Constant | −1.731 | 0.177⁎ | 0.099–0.318 |
| Age – 60 (per y) | −0.023 | 0.977⁎ | 0.964–0.990 |
| Liner usage (yes=1, no=0) | 0.489 | 1.631⁎ | 1.081–2.462 |
| Use of prosthesis indoors (50% to 100%=1, 0% to 50%=0) | −0.600 | 0.577⁎ | 0.316–0.951 |
| Use of bilateral walking aids (yes=1, no=0) | 0.488 | 1.630⁎ | 1.046–2.539 |
| Use of antibacterial soap (yes=1, no=0) | 0.504 | 1.656⁎ | 1.008–2.720 |
| Dependent: mechanical complaints (yes/no) | |||
| Constant | −0.511 | 0.600⁎ | 0.448–0.803 |
| Age – 60 (per y) | −0.014 | 0.986⁎ | 0.976–0.995 |
| Frequency of washing stump (4 times/wk or more=1, less than 4 times/wk=0) | 0.350 | 1.420⁎ | 1.018–1.980 |
| Dependent: occlusion (yes/no) | |||
| Constant | −0.231 | 0.793 | 0.539–1.168 |
| Age – 60 (per y) | −0.026 | 0.975⁎ | 0.964–0.985 |
| Sex (man=1, woman=0) | −0.465 | 0.628⁎ | 0.462–0.855 |
| Reason amputation trauma (yes=1, no=0) | 0.505 | 1.656⁎ | 1.157–2.371 |
| Use of walking aids (yes=1, no=0) | 0.618 | 1.856⁎ | 1.343–2.564 |
| Use of antibacterial soap (yes=1, no=0) | 0.599 | 1.820⁎ | 1.205–2.748 |
⁎Significant (P≤.05). |
Trauma as reason for amputation was a provocative determinant in case of skin problems caused by occlusion (OR=1.656). Use of walking aids was a provocative determinant in eczema (OR=1.479) and skin problems caused by occlusion (OR=1.820). Use of bilateral walking aids was a provocative determinant in skin problems caused by peripheral arterial disease (OR=1.630). Washing the residual limb 4 times a week or more often was a provocative determinant in skin problems in general (OR=1.413) and mechanically induced skin problems (OR=1.420). Use of antibacterial soap was a provocative determinant in skin problems in general (OR=1.794), skin problems caused by peripheral arterial disease (OR=1.656), and skin problems caused by occlusion (OR=1.820). Having a liner was a provocative determinant in skin problems caused by peripheral arterial disease (OR=1.631). Finally, smoking was a provocative determinant in skin problems in general (OR=1.581).
The regression score can be used to calculate statistically the odds of having a skin problem by using the formula Pskin disorder= es/(1+ es). In this formula, Pskin disorder is the risk of having a skin problem; S is the regression score of that person, and e=2.72.
For example, a 70-year-old man with a transfemoral lower-limb amputation as a result of diabetes who washes his stump 7 times a week, uses no antibacterial soap, and is smoking, has the following odds of having a skin problem in general. The regression score is (.366 – [.015*10] – [.354*1] – [.426*1] + [0.346*1] + [.584*0] + [.458*1]) = .24.
The odds for this person of having a skin problem in general is therefore e.24/(1+ e.24)=.62.
Discussion
Protective Determinants
Protective determinants (associated with a decreased risk for skin problems) identified in this study were higher age, male sex, amputation caused by peripheral arterial disease and/or diabetes, and the use of the prosthesis indoors more than 8 hours a day. Higher age was a protective determinant for all outcome measures. The adjustment of the age of the participant for the regression model was performed for statistical reasons to optimize the regression analysis. The age of 60 years was chosen because of clinical relevance and the similarity with the average age of the amputees. In addition, the regression coefficients are more easily interpreted. Age as a protective determinant is in contrast with a previous study among silicone sleeve users, in which higher age was associated with an increased risk for skin problems.12 An explanation for high age being protective may be the changes of the skin caused by aging. In the elderly, the ability to sweat has decreased,15 which may result in a lower level of moisture of the skin in the socket. In addition, in the elderly there is a decrease in skin thickness.16 This decrease may result in a different distribution of shear and stress forces on the residual limb, which may lead to protection against skin problems based on mechanical influence. Another explanation may be that elderly amputees tend to have a decreased level of activity12, 17 and make less use of their prosthesis.17, 18 However, activity level and low frequency of prosthesis use did not contribute significantly to the regression equation. This discrepancy may be explained by the fact that activity level was assessed only by means of reported daily walking distance. Walking speed and how the distance was walked (as a whole or with breaks) was not assessed. In addition, it was not assessed whether the skin problem had an influence on the walking distance. Finally, lower-limb amputees have difficulty assessing their own level of activity,19 introducing information bias.
Male sex was a protective determinant for skin problems in general, eczema, and skin problems caused by occlusion. This finding contrasts with the assumption that generally the activity level of males is higher than that of females,20 resulting in an increased mechanical influence of the prosthesis and more skin problems. However, this assumption was not confirmed in the regression analyses. The supposed protective influence of male sex may be the result of selective attention of females to their skin, resulting in females reporting skin problems more often than males. In general, females report more health problems compared with males.21
Peripheral arterial disease and/or diabetes as the reason for amputation were a protective determinant for skin problems in general and for eczema. This result is similar to the result of previous research.14 An explanation for this association may be that in the elderly, the main reason (94%) for lower-limb amputations is peripheral arterial disease and/or diabetes.22 After a lower-limb amputation, elderly tend to become less active compared with younger people who underwent a lower-limb amputation for the same reason.23 However, as mentioned, the activity level did not contribute significantly to the regression equation. Another explanation might be that in patients with a diabetic foot or with peripheral arterial disease, clinically eczema does not occur frequently. Perhaps this observation can be generalized to patients with a lower-limb amputation caused by peripheral arterial disease and/or diabetes.
Prosthesis use indoors more than 8 hours a day is a protective determinant for skin problems caused by peripheral arterial disease. A more frequent and prolonged use of the prosthesis may indicate a higher level of activity and may be an indication for fewer complaints as a result of peripheral arterial disease. In addition, elderly people have an increased risk of developing peripheral arterial disease and tend to use a prosthesis less.17, 18
Provocative Determinants
Provocative determinants (associated with an increased risk for skin problems) were use of walking aids, washing the stump 4 times a week or more often, use of antibacterial soap, use of a liner, and smoking.
Use of walking aids was a provocative determinant for eczema and skin problems caused by occlusion (use of walking aid), and/or skin problems caused by peripheral arterial disease (use of bilateral walking aids). This result is partly similar to the result of previous research14 in which the use of a walking aid (single-point cane) or no walking aid increased the odds for a skin problem. Perhaps (bilateral) walking aids are more often used by amputees with a low level of activity, who therefore may have a higher risk for developing skin problems, because when these amputees are walking, the skin of the amputation stump is less used to shear and stress forces. It is unclear why the use of walking aids is not a provocative determinant for mechanically induced skin problems.
Washing the residual limb 4 times a week or more often was a provocative determinant for skin problems in general and mechanically induced skin problems. The reported washing frequency may differ from the normal frequency of the participants because the questionnaire has been assessed in a warm period (summer 2005). The warmth may have evoked sweating and therefore influenced the washing frequency. Clinically, it has been advised to wash the stump once a day.24 Therefore we repeated the analysis, with washing frequency of the stump dichotomized into less than once a day and once a day or more often. Washing frequency remained a provocative determinant. This association may be explained as follows. First, frequency of washing may have increased as a result of a skin problem. One can imagine when an abrasion is present the amputee increases his level of hygiene to prevent deterioration of the abrasion. Second, the high frequency of washing induced an increased vulnerability of the skin on the stump. However, washing frequency was not a determinant for eczema, whereas one might expect such an association on the basis of pathophysiology25 (patients who have frequent contact with water and soap [detergents] have an increased chance of developing eczema). In addition, when evaluating the outcome measure eczema, itching and sensitive skin were not significant determinants in the regression model, whereas clinically these symptoms are often present in patients with eczema. Therefore, sensitive skin may not be related to the chance of developing a skin problem on the amputation stump. Besides washing frequency, the use of antibacterial soap was a provocative determinant for skin problems in general, skin problems caused by occlusion, and skin problems caused by peripheral arterial disease. A high frequency of washing with soap may result in dry skin, which may elicit skin problems.25 A participant may have started to use antibacterial soap to prevent a present skin problem from deterioration, although skin problems caused by occlusion and peripheral arterial disease are not logically associated with use of antibacterial soap.
Having a liner was a provocative determinant for skin problems caused by peripheral arterial disease. Clinically, it is common to prescribe a prosthesis with a liner to a transtibial lower-limb amputee, unless a liner is not suitable (because of the level of amputation, length of the stump, or shape of the stump). As mentioned, most lower-limb amputees have had the amputation because of peripheral arterial disease. This association between a liner and peripheral arterial disease is probably the result of confounding by indication. Hyperhidrosis or persistent heat rashes are 2 reasons to stop using a liner, although the first complaint is mostly temporary.12 Clinically, a persistent cold skin is another reason to stop using a liner. The participants in this study probably did not experience those problems (anymore), because on average, the time since amputation was 20 years. Liner usage was not protective for other types of skin problems in the regression analysis. This result is in contrast to the claim liner manufacturers make that liner use is protective against developing skin problems, but in agreement with the results of a systematic review reporting that in transtibial amputees, skin problems were not solved by liner usage but were sometimes even provoked by it.26
Smoking was a provocative determinant in skin problems in general. Smoking can cause peripheral arterial disease, also on the level of microcirculation, and an increase of elastosis that leads to a decrease in elasticity of the skin.27 This process may increase the reaction of the skin on mechanical stress, and therefore facilitate the development of skin problems.
Prevalence
The prevalence of skin problems of 63% (95% CI, 60%–67%) found in the current study is higher than other prevalences reported in the literature. Chan and Tan9 reported a prevalence of 16% (95% CI, 7%–28%), Lake and Supan12 reported a prevalence of 54% (95% CI, 41%–66%), and Dudek et al14 reported a prevalence of 40% (95% CI, 37%–44%). The difference in prevalence is probably based on sampling method, study population, and assessment method.
Study Limitations
Our study has some limitations. Our study sample seems to differ from the general population of lower-limb amputees in The Netherlands. In our study sample, peripheral arterial disease and/or diabetes was the reason for lower-limb amputation in 28% of the participants, while most lower-limb amputations in The Netherlands are performed because of peripheral arterial disease and/or diabetes (94%).22 However, a substantial number of these lower-limb amputees had a limited life expectancy.28 In addition, 38% of the participants were over 65 years of age, while of the patients who undergo a lower-limb amputation in The Netherlands, 79% are over 65 years of age.22 It is not clear whether our population resembles the general population of lower-limb amputees in The Netherlands. There is probably a difference in age and reason for amputation.
A self-developed questionnaire was used because no suitable Dutch questionnaire concerning skin problems and its determinants was available.8 Although several publications identified in a systematic review did use a questionnaire, these questionnaires assessed activity level, prosthesis use, and level of satisfaction, but not skin problems and determinants of skin problems. Research performed in the past concerning skin problems was bound to a hospital or rehabilitation center, where in a participant the type of skin problem was assessed, without taking determinants into account. By using a questionnaire in our study, we were able to obtain a large number of participants.
We achieved a response rate of 40% (from the initial number of 2039 participants). An explanation for the response rate of our study may be that lower-limb amputees were invited to participate in this study concerning skin problems of the stump. The invitation letter stated that it was important for lower-limb amputees without skin problems to participate also. However, lower-limb amputees who did not have skin problems at the time of invitation probably were less likely to participate. Another explanation may be the high age of possible participants. Analysis of the amputees who did respond but did not want to participate showed a significantly higher age than the participants. A third explanation may be the design of this study, a survey based on a postal questionnaire, for which response rates are low.29
The determinants assessed in this study were chosen on the basis of known hypotheses (reported in literature, or observed in daily practice), knowledge in pathophysiology, and clinical reasoning concerning skin problems of the stump in lower-limb amputees. This procedure does not mean that all possible determinants were mentioned in the questionnaire. Further, it is possible that determinants were misinterpreted by participants. Also, it is possible that determinants were not assessed extensively enough. However, we performed an explorative study and tried to give direction to further research.
The results of this study are probably influenced by various types of bias. Selection bias may have occurred. Amputees without skin problems may be less likely to participate in this study, as mentioned, resulting in overestimation of the prevalence. Elderly people may not be motivated or are not able to participate in this study. The latter reason is confirmed by comparing the average age of the group of participants and nonparticipants; the latter group had a significant higher average age. Because higher age was a protective determinant, our prevalence may be an overestimation, because skin problems are less frequent in elderly people.
Recall bias could have occurred because the problems that had to be reported had occurred in the past. Some people may tend to forget small skin problems or skin problems that had no influence on functioning. This type of bias may have resulted in an underestimation of the prevalence. Information bias could have occurred because skin problems were self-reported. Some participants may have misinterpreted their skin problem and did not report correctly. The direction and magnitude of this type of bias are unknown.
The time window in which symptoms could be reported may have been too long (1 month), but this window was chosen because some of the symptoms investigated (like mechanical complaints) take several days to develop or persist. When choosing a shorter time window, some types of skin problems might be missed. It is possible that participants endured more than 1 episode of skin problems, resulting in an underestimation of the prevalence.
Because of the study design, it is difficult to explain the direction of the relationship between a determinant and an outcome measure. It is difficult to establish whether a determinant was present prior to the skin problem or the determinant became present as a result of the skin problem. Thus, all significant determinants identified in this study have to be interpreted with caution. No direct causal relationships can be inferred, nor should the found determinants used at this moment alter daily practice. However, the findings of this study may give direction to future research.
Conclusions
Provocative determinants of skin problems of the stump identified in this study are (in order of magnitude of association) use of antibacterial soap, smoking, and frequency of washing the amputation stump.
Supplier
Appendix
Appendix 1. Domains of the Questionnaire
| Domains |
|---|
| Demographics |
| Source(OIMorLVvG) |
| Dateofbirth,datewhenquestionnairewasanswered |
| Age,sex,maritalstatus,levelofeducation |
| Amputationcharacteristics |
| Date,sideandlocationofamputation |
| Bilateralamputation |
| Levelofamputation,reasonforamputation |
| Multipleamputations |
| Othermedicalinformation |
| Complaintsofnonamputatedlimb |
| Presenceofcomorbidity,smoking |
| Prosthesischaracteristicsanduse |
| Hoursduringthedayprosthesiswasworn |
| Linerusage |
| Useofmaterialsbetweensocket/linerandstumpskin |
| Percentageoftimewalkingwithprosthesisindoors |
| Mobilityandactivities |
| Distancewalkedadayoutdoorswithprosthesis |
| Useofwalkingaids |
| Performingsports(withprosthesis),employment |
| Hygiene |
| Takingcareofstumpbyoneselforwithassistance |
| Shavingresidualstump |
| Frequencyofwashingstump,liner,andsocks |
| Kindofproductsusedforwashing |
| Skinproblems |
| Presenceofskinproblemsinpast |
| Presenceofallergyinpast |
| Skincomplaintsonotherpartsofbody |
| Typeofskin |
| Skinproblemsinpreviousmonth |
| Commentsandgeneralremarks |
Appendix 2. Classification of Symptoms Into the Different Outcome Measures
| Outcome measure |
| Symptoms that are part of the outcome measure |
| Suspicion of eczema |
| Sensitive skin⁎ |
| Itching skin⁎ |
| Redness of skin persisting >1 minute after removing prosthesis |
| Crusts |
| Mechanically induced skin problems |
| Blisters |
| Crusts |
| Corn/callus |
| Abrasion |
| Existing wound |
| Mechanical complaints |
| Skin problems caused by occlusion |
| Profuse sweating |
| Warm skin |
| Pimples |
| Sensitive skin⁎ |
| Itching skin⁎ |
| Skin problems caused by peripheral arterial disease |
| Cold skin |
| White/blue skin |
⁎Sensitive and itching skin were assessed using a 4-point rating scale (none, light, moderate, severe), which was dichotomized (none/light=absent, moderate/severe=present). |
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No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the authors or on any organization with which the authors are associated.
PII: S0003-9993(08)01557-8
doi:10.1016/j.apmr.2008.07.015
© 2009 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.
Volume 90, Issue 1 , Pages 74-81, January 2009
