Any outcome measure that would be used by prosthetists must be user friendly. It must be fast in set-up, administration, and analysis. If change in patient functional status is investigated, two or more visits will be required to measure that change. A 15-minute test may at first seem like a reasonable amount of time. However, if several 15-minute tests need to be accomplished and if comparing test results from multiple visits is needed to evaluate potential changes in function, the time required adds up and may become unmanageable.
Prosthetists, in general, tend to resist increased demands for documentation and therefore are likely to resist participation in outcomes studies. If written questions are administered, the prosthetists need to be trained in how to respond to questions that may be asked by patients seeking clarification of the questionnaire. If a physical test is to be administered, prosthetists need to be trained in how the test is to be performed and scored. If these matters are not adequately addressed, the validity of the study may be compromised by tester-induced variables.
Outcomes measures, other than physical functioning tests, need to be appropriate for persons of different cultural backgrounds to appropriately report outcomes across the broad spectrum of persons served by prosthetists in the United States. Administration of the tool must account for language differences.
POTENTIAL BENEFITS OF OUTCOME MEASURES
It is hoped outcomes research will provide clearer indications and contraindications for specific component use. Many of the clinical decisions made today regarding fitting method and component selection are based on the prosthetist's perceived success with previous patients. We need to move from this subjective method of prosthetic prescription to an evidence-based foundation for prosthetic practice. One of the most frustrating aspects of clinical work is complying with requests for documentation as required for authorization and payment of prosthetic services. Too often this documentation is based on unsubstantiated claims by manufacturers and not on objective evaluation of the benefits that can be derived from use of a specific component for a specific patient. If outcomes research can help build an evidence-based approach to prosthetic prescription, all parties will benefit.
It is generally accepted within the field of amputee rehabilitation that timely fitting leads to the best outcomes. The evidence available today suggests that the time to fitting of the first prosthesis has a significant effect on prosthesis use and satisfaction with the device. Persons who wait more than 60 days are less likely to be satisfied with prosthesis fit, comfort, appearance, and overall performance.1 Despite the evidence that early fitting improves outcomes, some payers continue to delay the process. This problem should continue to be addressed to strengthen the claims that delayed fitting compromises prosthetic outcome.
TYPES OF OUTCOME MEASURES
QUALITY OF LIFE MEASURES
Quality of life (QOL) measures are self-report questionnaires. This is appropriate because we are interested in the individual's own appraisal of his/her QOL, such as happiness, control of destiny, and expectations versus reality.
One major barrier to clinical application of outcome measures, especially measures of QOL, is the fragmentation of amputee rehabilitation in the United States. Prosthetists are best suited to address function. But function is only one aspect of total patient care and perhaps only a minor concern with regard to QOL. Callaghan and Condie2 state that there is “a stronger relationship between mental health and quality of life than between physical health and quality of life.”
In designing a procedure for review of responses given on a QOL questionnaire, a mechanism should be in place to recognize issues that should be managed by appropriate professionals. For example, I would be uncomfortable having prosthetists acting independently to administer a questionnaire that focuses on psychosocial issues without the ability to address issues that may arise, such as depression, pain, or medication issues. However, psychosocial issues certainly affect function and satisfaction and should be addressed by the rehabilitation team.
Self-report mobility measures are questionnaire-based. These are very attractive because they require little or no involvement by the prosthetist, and the tools can perform well for general mobility questions. Unfortunately, these measures may not be sensitive enough to portray the true function of the patient and may not be detailed enough to make individualized judgments about the outcome related to specific components. An individual may have a skewed view of his or her own performance. Although a favorably skewed impression of ability may lead to a better QOL score, it would not necessarily support use of one prosthetic component over another if a real functional advantage were not achieved.
Some of the tools reviewed for this conference could not discriminate known differences. Treweek and Condie3 comment on this: “A clinically useful functional outcome measure should reflect clinical experience. A functional outcome measure for use with lower limb amputees should, at the very least, demonstrate a statistically significant difference in the scores obtained by patients who have been subdivided by age and level of amputation. A measure that does not show that transtibial amputees have more functional capacity on average than transfemoral amputees must be considered dubious since clinical observation shows that there is a very real difference” (p 182). Devlin et al.4 report that “The Houghton Scale successfully discriminated between transfemoral versus transtibial participants; however, there was no difference between unilateral and bilateral transtibial participants, nor was there any difference in Houghton scores between age groups” (p 1342). It is of paramount importance that the outcomes tools chosen are appropriate for the subject group and that they perform properly.
MOBILITY: GRADED BY AN OBSERVER
In the category of mobility tests, the 2-minute walk test stands out as a tool worth additional investigation for use in prosthetic facilities. This test shows a difference between transfemoral and transtibial prosthesis users that agrees with clinical experience. The test also shows if improvement occurs over time. It would be interesting to use this test in a same-subject test to evaluate whether differences in components, socket design, and suspension methods can be appreciated. The timed up-and-go test is also simple and seems useful for elderly amputees; however, younger, higher-functioning amputees may not be sufficiently challenged by these simple tests, resulting in a notable ceiling effect. Most lower limb amputees are elderly, so these simple tests should perform well for the greatest number of prosthetic patients.
Prosthetists, along with the prescribing physician, are required by Medicare to assign a functional level. The Amputee Mobility Predictor (AMP) seems to be ideal for this purpose. In cases in which the functional status after rehabilitation is difficult to predict, a standardized tool such as the AMP could provide a more scientific method of appropriately assigning a functional level classification, therefore allowing for provision of appropriate components during the period of acute rehabilitation when physical therapy training is most intensive.
Despite the difficulties of applying outcome measures to prosthetic practice, the benefits are well worth the effort. Clearly, amputees benefit from prosthetic intervention in general. However, for much of what we do, there is limited evidence-based research to guide clinicians as they seek to optimally restore physical function. Prosthetic prescription has become much more complex during the past decade. Patients, clinicians, and payers require quality outcomes measures to determine which prosthetic systems and methods provide optimal outcomes.
1. Pezzin LE, Dillingham TR, MacKenzie EJ, et al. Use and satisfaction with prosthetic limb devices and related services. Arch Phys Med Rehabil
2. Callaghan BG, Condie ME. A post-discharge quality of life outcome measure for lower limb amputees: test-retest reliability and construct validity. Clin Rehabil
3. Treweek SP, Condie ME. Three measures of functional outcome for lower limb amputees: a retrospective review. Prosthet Orthot Int
4. Devlin M, Pauley T, Head K, et al. Houghton scale of prosthetic use in people with lower-extremity amputations: reliability, validity, and responsiveness to change. Arch Phys Med Rehabil