Commonalities, differences, and challenges with patient-derived outcome measurement tools: function/activity scales.

BACKGROUND: There is a critical need to evaluate the success of orthopaedic treatments through valid outcome measures. Previous attempts to express patient outcomes using a single aggregate score led to scores that were ambiguous, often insensitive to change, and poorly correlated with the patient's assessment of the outcome of surgical procedures. WHERE ARE WE NOW?: Numerous patient-reported outcome measurement tools have been developed for assessment of patients' level of activity and functional status, especially after joint arthroplasty. However, most tools assume an idealized set of prescribed activities independent of the age, activity level, and lifestyle of each individual. Few instruments are designed to capture the priorities of individual patients, especially those involved in high-demand sporting and recreational activities. WHERE DO WE NEED TO GO?: We need valid outcome measures that provide a meaningful, individualized assessment of the functional status of each patient, taking into account the lifestyle and expectation of each individual. This advance in outcome measurement will allow clinicians to individualize treatment and provide patients with an accurate estimate of the outcome of alternative treatments and procedures. HOW DO WE GET THERE?: Much more comprehensive information is needed to characterize the activities, abilities, and physical aspirations of individual patients. This could form a database for the development of predictive models relating individual characteristics to functional outcomes. Statistical tools are needed to minimize the burden on patients in completing questionnaires to access predictive data and to ensure that all outcome assessments are psychometrically valid.