Criterion and Construct Validity of Prosthesis-Integrated Measurement of Joint Moment Data in Persons With Transtibial Amputation

Prosthesis-integrated sensors are appealing for use in clinical settings where gait analysis equipment is unavailable, but accurate knowledge of patients' performance is desired. Data obtained from load cells (inferring joint moments) may aid clinicians in the prescription, alignment, and gait rehabilitation of persons with limb loss. The purpose of this study was to assess the accuracy of prosthesis-integrated load cells for routine use in clinical practice. Level ground walking of persons with transtibial amputation was concurrently measured with a commercially available prosthesis-integrated load cell, a 10-camera motion analysis system, and piezoelectric force plates. Ankle and knee flexion/extension moments were derived and measurement methods were compared via correlation analysis. Pearson correlation coefficients ranged from 0.661 for ankle pronation/supination moments to 0.915 for ankle flexion/extension moments (P < .001). Root mean squared errors between measurement methods were in the magnitude of 10% of the measured range and were explainable. Differences in results depicted differences between systems in definition and computation of measurement variables. They may not limit clinical use of the load cell, but should be considered when data are compared directly to conventional gait analysis data. Construct validity of the load cell (ie, ability to measure joint moments in-situ) is supported by the study results.