Validity of the intelligent device for energy expenditure and activity accelerometry system for quantitative gait analysis in patients with hip osteoarthritis.

OBJECTIVE To evaluate the concurrent validity of an accelerometry-based system (Intelligent Device for Energy Expenditure and Activity) with a criterion instrument (Gaitrite) for the evaluation of spatiotemporal gait variables in orthopedic patients. DESIGN Validity study. SETTING Research laboratory in an orthopedic hospital. PARTICIPANTS Men with unilateral hip osteoarthritis (N=26; mean age ± SD, 54±9y). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Patients were asked to walk at normal and fast velocities while gait cycle, swing, double support, step length, cadence, and speed were concomitantly recorded with the 2 instruments. Concurrent criterion-related validity was examined using intraclass correlation coefficients and Bland-Altman limits of agreement. RESULTS Intraclass correlation coefficients were acceptable for all gait parameters (range, .815-.997), except step length (.783). Limits of agreement were low for gait cycle, swing, and cadence, though relatively high for double support, step length, and speed. A significant bias between the 2 measuring instruments was consistently observed. CONCLUSIONS In patients with hip osteoarthritis, quantitative gait analysis with the IDEEA accelerometry system was satisfactory for the main temporal gait parameters, while double support, step length, and walking speed quantifications were invalid. The IDEEA system should be used with caution, and modifications of the system are recommended for improved use in clinical practice and research.