AMBULATORY ACCELEROMETRY TO QUANTIFY MOTOR BEHAVIOR IN PATIENTS AFTERFAILED BACK SURGERY - A VALIDATION-STUDY

In the treatment of patients with pain, measures related to (pain) beh aviour are of major importance. Ambulatory activity monitoring can be used to obtain insight into actual behaviour. This study was designed to validate the Activity Monitor (AM), an instrument based on long-ter m ambulatory monitoring of accelerometer signals, to assess several ph ysical activities during normal daily life. Ten failed back surgery (F BS) patients performed a number of functional activities in and around their own houses. During the measurements, continuous ambulatory regi strations of accelerometer signals were made, based on four body-mount ed accelerometers (one on each upper leg, two on the trunk). Video rec ordings made simultaneously with the measurements were used as a refer ence. The continuous output of the AM (postures, transitions, dynamic activities) was compared with visual analysis of the videotapes. The o verall results showed an agreement between AM output and video analysi s of 87% (inter subject range: 83-88%). The maximal error in the deter mination of the duration of activities was 0.3%. The overall number of dynamic periods was determined well (AM: 359; video: 368), while the number of transitions was slightly overestimated (AM: 228; video: 205) . The results when using the three-sensor version of the AM were somew hat less accurate (overall agreement from 87% to 82%). The AM appeared to be a valid instrument to quantify aspects of behaviour of FPS pati ents, such as duration of activities and number of transitions. This n ew technique of ambulatory measurement of mobility activities seems to be a relevant and promising extension of the techniques currently use d in the evaluation of pain treatment. (C) 1998 International Associat ion for the Study of Pain. Published by Elsevier Science B.V.