The PPA was initially built for self-administration (postal version), but it can also be used for face-to-face and telephone interview. A guide is available and an “information chart” was developed to compile precollected data from the respondents’ medical chart (i.e., age, sex, cause of amputation, and so forth). The “information chart” complements the PPA. The PPA is a follow-up tool that can be completed in 25 minutes. Most sections are applicable at discharge from the rehabilitation center.
The PPA was initially developed and validated in French and English. It is now available in six languages: Dutch, English, French, Italian, Spanish, and Portuguese. All versions were translated using Del Greco's back-translation technique.19 The PPA was also reported as having been used in Iran.20
Except for question 11, which is an index on locomotor capabilities, no composite score can be computed for the PPA or for the six basic sections. To trace the profile of the person with LLA for each of the three factors and sort out the most significant variables related to prosthetic use, associations between the outcome variable and various factors may be done using appropriate statistical analyses such as regression analysis.
The PPA was assessed for content validity by a group of 13 experts and a group of 8 fitted lower limb amputees.4 To ensure the content validity of the instrument, the pertinence of each question with regard to the questionnaire's objectives was assessed. The pertinence of the 44 questions was high and the PPA was found to cover all relevant aspects of amputee rehabilitation. Thereafter, pretesting of the questionnaire was conducted with a random sample of 26 lower limb amputees.4
The Reintegration to Normal Living (RNL)21 scores of 70 lower extremity amputees were correlated with data collected from the PPA.11 The results confirmed convergence of analogous constructs of the RNL and the PPA questionnaire. The data of the “physical performances” construct of the PPA and the “daily activities” subscale of the RNL converged fairly to moderately well (r = 0.56, p < 0.01). Fairly good correlations (r = 0.64, p < 0.01) were also observed between the “acceptance of amputation and prosthesis” construct of the PPA and the RNL “perceptions of self” subscale.
For continuous data, test-retest reliability was considered excellent.11 The intraclass coefficient for the weekly use of the prosthesis item was 0.92 (p < 0.001) and 0.80 (p < 0.001) for the LCI. For categorical data, Cohen's kappa varied from 0.46 to 0.84. For some ordinal variables, weighted kappa was used and moderate to substantial agreements were computed (κ = 0.44 to 0.73). High agreements were obtained for nominal variables (κ = 0.60 to 0.86). For almost all factual information questions regarding health problems, condition of the nonamputated limb and residual limb, prosthetic problems, and activities of daily living, test-retest agreements were high.
Inter-rater reliability was not assessed because it was not pertinent for the postal version. When using the telephone version, training of the interviewers is necessary.
OUTCOME WITH THE PPA
The PPA questionnaire is valid and reliable for clinical and research use. It is the only tool reported in the literature that is specific to the factors related to prosthetic use by the lower limb amputee. A provincial study in Québec, Canada, on factors predisposing to prosthetic use has shown that adaptation to the amputation and prosthesis and level of amputation were significantly correlated to prosthetic wear and active use indoors and outdoors.22 Presence of arthritic problems in the nonamputated limb was negatively related to prosthetic wear. For activities outdoors, muscle cramps and sores were the limiting factors. Long delays in limb fitting, prolonged training, cardiac and respiratory problems, and constant residual limb pain were significantly related to nonuse of the prosthesis.23 Further results demonstrated that the ability to don the prosthesis, the locomotor capabilities with the prosthesis, walking distances, automaticity of gait, and assistive devices used were the main enabling factors related to prosthetic wear and active use of the prosthesis.22 People with transfemoral amputation reported greater difficulties in donning their prosthesis and a significantly higher rate of falls.22
Results of PPA use in the Netherlands showed remarkable resemblance with the Québec population in terms of prosthetic use.23 In the Netherlands, 94% of the fitted lower limb amputees did wear their prosthesis daily, 76% wore it more than 9 hours per day and 63% used it during the majority of their indoor activities and 71% for outdoor activities. The Dutch researchers also observed that the amputee profile remained stable over a period of 2 months after discharge. Factors influencing prosthetic use were not reported.
LOCOMOTOR CAPABILITIES INDEX
The LCI was designed to trace a comprehensive profile of ambulatory skills of the lower limb amputee with the prosthesis and to evaluate their level of independence while performing these activities. The LCI refers to question 11 of the PPA but can be used independently. It is composed of 14 items that measure one general construct: locomotor capabilities of the lower limb amputee with the prosthesis.4 Two subscales emerge from this general construct: basic (7 items) and advanced (7 items) locomotor capabilities with the prosthesis (Figure 5). The person is asked whether or not he/she wears the prosthesis and whether he/she would be able to do the activities listed with the prosthesis. Hence, when self-administered at follow-up, the LCI measures the perceived capacity and not the actual performance. On the other hand, clinicians have also been using the index during the course of the rehabilitation program to observe the actual performance of the person over time. When applied at the beginning of the prosthetic training, the LCI allows the clinician and the person with the LLA to set goals and later to review progress during rehabilitation and at follow-up.
The LCI is easily administered (self-administered, face-to-face, or telephone interview) and may be completed in 5 minutes. Respondents are asked to indicate the statements that best describe their situation at the moment the LCI is filled out. The LCI is composed of 4-point ordinal scales and provides an aggregated score for the 14 items. Each item is scored from 0 (not able to) to 3 (yes alone). A total score of 42 may be calculated and maximum subscores of 21 may be obtained for the basic and advanced capabilities subscales. Franchignoni et al.24 transformed the original scale of the LCI into a 5-level version, the LCI-5. The upper ordinal level of each LCI item "Yes, alone" was split into 2 levels: "Yes, alone, with ambulation aids" (score: 3 points) and "Yes, alone, without ambulation aids" (score: 4 points). Hence, the total score of the index was 56 with maximum subscores of 26. The LCI and LCI-5 were found to be highly and significantly correlated (r = 0.89, p < 0.001).
A new method of presenting results from the LCI has been developed by Geake et al.25 to facilitate interpretation of the scores by the clinicians. A computerized system uses graphical presentation of the capabilities of the patient by items and scores and indicates which of the locomotor activities needs further attention.
The LCI is available in seven languages: Dutch, English, French, Italian, Portuguese, Spanish, and Swedish. All versions were translated using Del Greco's back-translation technique and are valid for research and clinical use.19 The LCI was reported having been used in Iran and Korea,19,26 although no information is available as to the translation technique used in those two countries.
The items of the LCI were identified by a team of health professionals and persons with LLA and represent skills facilitating use of the prosthesis.4
The LCI is part of the Prosthetic Profile of the Amputee (PPA) questionnaire that was tested for construct validity.5 Data confirmed convergence of analogous constructs such as the locomotor capabilities construct of the PPA questionnaire and the daily activities construct of the RNL index. Convergent validity was also evidenced when the LCI was compared with the 2-minute walk test, the Timed Up-and-Go, and the Activity Balance Confidence scale.27
The LCI, the Functional Independence Measure (FIM), and the Amputee Activity score (AAS) were found to correlate significantly (χ2 = 57.28, p < 0.01).28 The LCI also correlated significantly with the Rivermead Mobility Index (Spearman coefficient =0.752), the Timed Walking test (Spearman coefficient =0.667), and the FIM (Spearman coefficient =0.617).24
Using the LCI, it is possible to discriminate between groups of persons with LLA for cause of amputation, levels of amputation, age, walking distance, ambulation aids, and automatism of gait.5,24,27,29 The sensitivity of the advanced activity subscale is similar to that of the full index. Effect size was computed by Miller et al.,27 and values for the LCI were larger than 0.8, thus implying a good ability to detect differences. Rushton and Miller30 reported medium effect size (value of 4.7); however the latter study included only 10 subjects.
tk;4Ceiling effects are observed with the basic activity subscale, but these appear to be reduced when using scores of the full index, specifically with the scores of the advanced activity subscale.5,29 Ceiling effects were associated with younger, more active amputees. The LCI cannot monitor change in individuals with higher locomotor capabilities. For example, it does not take into consideration the eventual reduced dependency on ambulatory aids. The LCI appears to be more appropriate for active yet elderly amputees with multiple comorbidities. To counteract the ceiling effect, Franchignoni et al.24 used the LCI-5, where the upper ordinal level of the original LCI was split into two levels that identified ambulatory aids users and nonusers. Top scores were reduced by one half, and the variability detected in the person's capabilities increased.
Internal consistency estimates and exploratory factor analysis showed evidence of homogeneity among the 14 items of the LCI.5 A Cronbach alpha of 0.95 was obtained. Two underlying factors, or subscales, were identified, and factor 1 explained 59.1% of the observed variance. The two subscales (each of seven items) were also shown to be internally consistent, with Cronbach alpha coefficients of 0.91 and 0.91, respectively.5 Miller et al.27 and Franchignoni et al.24 confirmed homogeneity among items of the LCI. Cronbach alpha coefficients were equal to 0.89 and 0.95, respectively. Other analyses using the Rasch Model confirmed homogeneity of the 14 items and the presence of the same two subscales (A.W. Heinemann, personal communication, 2000). The 4-point rating scale was found useful in distinguishing functional levels.
To evaluate test-retest reliability of the LCI,4 subjects were asked to complete the LCI twice, 4 weeks apart. This delay was considered long enough to minimize carry-over effects and short enough to expect that the health and functional status of respondents would be stable. Excellent test-retest agreements were obtained for the total score of the LCI (intraclass coefficient = 0.80). Therefore, a high level of agreement exists between the two sets of scores. Excellent correlation (r > 0.75) was also found when each item of the LCI was tested individually for reliability. The reliability of the total score of the LCI was also reported to be high by Miller et al.27 and Franchignoni et al.,24 with intraclass coefficients of 0.88 and 0.98, respectively. Miller et al.27 used a 4-week interval, whereas Franchignoni et al.24 preferred a 1-day interval. Repeatability of the LCI is at a more than acceptable level.
Inter-rater reliability was not examined because it is not pertinent for self-administration. Inter-rater reliability was not reported for face-to-face or telephone interview and was not demonstrated for evaluators in a clinical setting. Further study is required.
OUTCOME WITH THE LCI
High scores on the LCI reflect greater locomotor capabilities with the prosthesis and less dependence on external assistance.31 In the province of Québec, 1 to 5 years after discharge, prosthetic users had maintained a high level of independence with the prosthesis and were capable of managing most of the basic and advanced activities with the prosthesis.31 Global scores and basic scores did not differ significantly for people with transtibial and transfemoral amputations, but advanced scores did. The advanced activities most often reported by prosthetic users as “cannot do” were climbing and descending stairs without handrails, walking outdoors on uneven ground, and walking during inclement weather.31 These results were corroborated by other authors.23,24
Nonusers were found to have significantly lower global scores than prosthetic users, in particular for advanced activities.31 The difficulties reported by nonusers were also those reported by transfemoral amputees. Transfemoral amputees were shown to have significantly (p < 0.005) more difficulties than transtibial amputees with five of the seven advanced activities: picking up objects from the floor (Figure 5), going up and down stairs without handrails, carrying objects while walking with the prosthesis, and walking outside in inclement weather. All the difficulties identified concerned activities performed in an open environment where the amputee must predict and adapt rapidly to environmental changes or activities requiring greater stability and motor control because the center of mass is critically moved over and out of the base of support. Hence, people with scores on the advanced activities subscale equal to or lower than 6 may be at risk of eventual nonuse of the prosthesis in the years after discharge. Special attention should be given to the identified difficult activities during rehabilitation. Yet, at follow-up, the LCI measures perception of a capacity and not the actual performance of the LLA. As Franchignoni et al.24 argued, it would be interesting to assess the actual difference between capability and performance.
The PPA is a valid and reliable instrument to assess prosthetic use and to help understand the predisposing, enabling, and reinforcing factors associated with prosthetic use or nonuse. Domains investigated concern the physical condition, the prosthesis, adaptation to the amputation and the prosthesis, and the physical and social environment. It is a follow-up questionnaire, but it may be used at discharge from the rehabilitation center to measure the evolution of the lower limb amputation condition over time after rehabilitation. The LCI, which is part of the PPA, evaluates locomotor capabilities of the fitted lower limb amputation. It encompasses two underlying constructs: basic and advanced locomotor capabilities. It was initially developed for follow-up but is currently used in daily clinical practice. Global and partial scores may be derived for rapid display and interpretation of the results. Both the PPA and LCI are available in several different languages.
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Keywords:© 2006 American Academy of Orthotists & Prosthetists
amputation; artificial limbs; lower extremity; outcome assessment; psychometrics; rehabilitation