Predictive Outcome Measures Versus Functional Outcome Measures in the Lower Limb Amputee (2006)

INTRODUCTION John Ware1 wrote, “Life has two dimensions: quantity and quality.” The distinction between the two entities is well illustrated in the common greeting “may you have a long and healthy life” (p. 473). Length of life is expressed in terms of average life expectancy, mortality rates, death due to specific causes, and numerous other indicators. When defining the second dimension, quality of life encompasses standard of living, the quality of housing and the neighborhood in which one lives, job satisfaction, and many other factors.1 With regard to the amputee, it has been well established that for a number of vascular amputees who have undergone an amputation due to the magnitude of vascular compromise, life expectancy is relatively short. For the amputee who has lost a limb to tumor, trauma, or congenital condition, amputation has little or no bearing on life expectancy. Medical interventions have improved care to the point where the impact of amputation on longevity has decreased tremendously. So, as quantity of life improves, what about quality of life? The World Health Organization (WHO) defined health as a “state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.”2 Health connotes “completeness” – nothing is missing from the person; it connotes “proper functions” – all is working efficiently. That would suggest that if a prosthesis has the ability to improve the quality of life for the amputee, then it should be provided. This is not to say that the “best” prosthesis belongs on all patients, primarily because what is considered the “best” for one person may be a hindrance to another. For example, a prosthetic foot that provides a mechanical high energy return at terminal stance, propelling the limb into the swing phase of gait will be a tremendous asset for a strong person with a fast cadence. Conversely, the same foot might only throw a frail, elderly person off balance, resulting in the fear of falling and a tentative gait pattern. Unfortunately, we are not sure what the best prosthesis is for the different amputee populations. The dilemma becomes apparent when trying to determine what are the best prosthetic components for each individual amputee. Common indictors such as materials, time of fabrication, complexity of design, and cost do not dictate the “best” components for each individual. Matching functional ability with the proper components is the solution for optimizing physical performance. This is not a novel concept. In fact, if questioned, most clinicians would agree that marriage of the correct prosthetic components for the appropriate level of function is one of the primary goals of the rehabilitation team. However, this goal is apparently not so easy to achieve. At the very root of the problem is the inability to define a “successful prosthetic ambulator.” There are many interpretations for this common goal, from simply using the prosthesis “about an hour per day”3 to “prosthetic use without external support on a daily basis.”4 There is no agreement anywhere with regard to the threshold of “successful prosthetic use.” The question is whether there is one threshold or many as severe authors have advocated by virtue of offering multilevel functional scales and indices. There is a wide variety of indices published within the literature.5–10 In the United States today, it appears that only one index is of significant consequence to Medicare and managed care providers, the Durable Medial Equipment Regional Carrier (DMERC) K codes or Medicare's Functional Classification Level (MFCL) index.11 Its exceptional importance is solely because assignment to a particular level of function within this index determines the level of prosthetic care, and, consequently, the financial reimbursement a prosthetist will receive for the prosthetic services rendered. After an extensive review of all available indices, the descriptors and selection of number of levels chosen for the MFCL index appears to be well constructed. This assumption is predicated on the basis that the MFCL index has a range from a fully dependent bed-bound amputee to a recreational athlete capable of higher level activities. Definitions clearly describe observable differences between each of the five levels using seemingly commonly assessed functional skills. It must be kept in mind, however, that as attractive as the MFCL may appear to be after initial examination, it was created based on content validity of a Medicare subcommittee and was not based on any formal scientific research. The use of a functional index seems to be reasonable, but how is the amputee classified? Currently, a physician or prosthetist classifies the amputee according to functional level. “Functional level” defined by Medicare is a measurement of the capacity and potential of the patient to accomplish his or her expected postrehabilitation daily function.11 Functional level is determined by three determinants: 1) the patient's past medical history, 2) the patient's current condition, including the status of the residual limb and nature of other medical problems, and 3) the patient's desire to ambulate. In reality, the physician or prosthetist looks at health status or the number of comorbidities and asks the patient if he or she wants to walk again. Helm et al.12 and Gailey et al.13 did not find comorbidity to be one of the strongest predictors regarding functional outcome, although many others had.14–17 Unfortunately, Medicare offers no standardized assessment index or formula for use by the clinician when determining the severity of the comorbidities associated with the amputee. Regarding an amputee's motivation to ambulate, it is not difficult to imagine that most amputees interested in prosthetic fitting will say they are very motivated to learn to walk and return to an active life style, especially when their response will influence the level of prosthetic care they will receive. The reality concerning the evolution of the prosthetic prescription process is that with the exception of some additional paperwork, the overall system has not changed at all. The prosthetist is still required to secure a physician's prescription prior to the fabrication of the prosthesis. If the physicians are to classify the amputees, they will continue to prescribe as they always have since there are no formal assessment guidelines. If they choose to “underprescribe” for fear that the patient will not reach rehabilitation potential, or in an attempt to contain medical costs, they can continue to do so. In many cases, the physicians have continued to leave the classification decision to the prosthetist as they have historically done by cosigning the necessary documentation. In most cases, this is very appropriate because the prosthetist is more familiar with all the prosthetic options available. As a result, the prosthetist decides the functional level of the amputee based on clinical experience without a formal assessment tool. If the prosthetists want to continue to “underfit” amputees, they can always use “lesser” prosthetic components. Conversely, if they choose to raise the level of prosthetic components beyond the amputees’ functional capability, for whatever reason, they can misclassify the amputee, or petition the physician or Medicare by providing the required documentation necessary to elevate the level of prosthetic care. The product of the MFCL system is the same subjective assignment of prosthetic components to the amputee with the minor addition of some documentation. There is no genuine system of checks and balances as originally intended. However, the most significant contribution of the MFCL process may be the formal definition of “prosthetic success” in the form of the MFCL index that describes a hierarchy of “prosthetic successes.” However, without a measurement tool that objectively and effectively assigns the amputee to each of the appropriate predetermined levels of “prosthetic success” by determining the amputee's “readiness to ambulate,” the same system that has prevailed throughout history continues to exist. The most common argument opposing the use of functional assessment tools is that professionals have the ability to accurately determine the needs of the amputee based on their years of clinical experience. After reviewing the findings of Stephen and Aitken,18 where significant differences were found in assessing mobility and self-care of the amputee who were evaluated by clinicians on the same rehabilitation team, the validity of such arguments must be questioned. If members of the same rehabilitation team find it difficult to agree where everyone theoretically has met in team meetings, treated common patients, exchanged professional information, and followed similar treatment policies, what is the likelihood that uniform agreement can be reached across multiple professions and amputee rehabilitation facilities? To further add potential confusion to the classification of amputees, Medicare offered very little in the form of guidelines or definitions concerning the five MFCL. Clearly, an objective assessment tool was needed to provide standardization to the process of assigning a functional level to the amputee. MEASUREMENT OF FUNCTION The signs of a patient getting better are often clear not only to the clinician but also to family members and the patient. The concept of functional assessment is to “measure change.” To measure change, the WHO has identified three areas of measure: 1) With impairment at the organ system level, has the underlying condition improved? 2) With disability as the functional consequence of impairment, has physical function improved? 3) With handicap as the social and societal consequence of disability, is the patient better off overall for the treatment?12 Functional outcome measures should consistently measure what they say they are going to measure.19 Consequently, we have the basis of and is a to the of and in any is best by the between on an individual with the across the range using the is the to which an measures what it is to the ability of the to measure the of In there is no standard of so is a can one measure with others that to the same The measurement tools identified from the can be into two subjective or assessment and the more objective the of assessment is a because of the of use and the ability to the patient's In there may be or with other of a use of defined and can be by the clinician but the for or is apparent if the is also the With of assessment the family or clinician is to complete a or similar and a or is can be the most objective providing more of the patient's physical do such as due to and created and that may only the patient's ability at a point in their rehabilitation not at the or in this of have been for the amputee. 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