Assessing activity in joint replacement patients

Outcome evaluations of lower extremity joint reconstructions should include an assessment of patient activity. In vivo wear assessments of total joint prostheses should be based on a measure of use, not time in situ or a proxy such as age or gender; however, clinicians lack a simple method to reliably assess the activity of patients with joint replacement. The modern pedometer can be a satisfactory means of quantifying the use of lower extremity joints. The pedometer, however, requires special effort on the part of the physician or evaluator and the patient. Therefore, we compared the quantitative assessment of walking activity of 100 total joint replacement patients, as measured with a pedometer, to the UCLA activity score and a simple visual analog scale that can easily be employed during a routine office evaluation. Both the UCLA activity rating (P = .002) and the visual analog scale rating of the investigator (P = .00001) had a strong correlation with the average steps per day as recorded by the pedometer. There was, however, up to a 15-fold difference in the average steps per day for individual patients with the same UCLA score. The visual analog scale as rated by the patients of their own activity did not have as strong a correlation with the pedometer data (P = .08) as did patient age (P = .049). For practical reasons, the pedometer is probably best reserved for the evaluation of extreme cases of activity (or inactivity). This study indicates that both the UCLA activity rating and the investigator visual analog scale are valid for routine activity assessment in a clinical setting. Adjustments of the UCLA activity score for the frequency and intensity of activity, as can be done with the investigator visual analog scale, increase the accuracy of the activity rating.