title: Assessment of objective ambulation in lower extremity sarcoma patients with a continuous activity monitor: rationale and validation.
abstract: In addition to patient reported outcome measures, accelerometers may provide useful information on the outcome of sarcoma patients treated with limb salvage. The StepWatch (SW) Activity Monitor (SAM) is a two-dimensional accelerometer worn on the ankle that records an objective measure of walking performance. The purpose of this study was to validate the SW in a cross-sectional population of adult patients with lower extremity sarcoma treated with limb salvage. The main outcome was correlation of total steps with the Toronto Extremity Salvage Score (TESS). In a sample of 29 patients, a mean of 12 days of SW data was collected per patient (range 6-16), with 2767 average total steps (S.D. 1867; range 406-7437). There was a moderate positive correlation between total steps and TESS (r = 0.56,  P = 0.002). Patients with osseous tumors walked significantly less than those with soft tissue sarcoma (1882 versus 3715, P < 0.01). This study supports the validity of the SAM as an activity monitor for the objective assessment of real world physical function in sarcoma patients.
authors.affiliation: Department of Orthopaedics & Sports Medicine, University of Washington Medical Center, 1959 Pacific Street NE, P. O. Box 356500, Seattle, WA 98195, USA.
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Gundle
authors.affiliation: Department of Orthopaedics & Sports Medicine, University of Washington Medical Center, 1959 Pacific Street NE, P. O. Box 356500, Seattle, WA 98195, USA.
authors.forename: Stephanie E
authors.initials: SE
authors.lastname: Punt
authors.affiliation: Department of Orthopaedics & Sports Medicine, University of Washington Medical Center, 1959 Pacific Street NE, P. O. Box 356500, Seattle, WA 98195, USA.
authors.forename: Ernest U
authors.initials: EU
authors.lastname: Conrad Iii