The effects of body position on pelvic tilt angles measured with a smartphone-based navigated ultrasound system in symptom-free young adults

Abstract

The study aimed to investigate whether pelvic tilt (PT) angles differ between the supine and upright position in symptom-free young adults. Additionally, the concurrent validity of the measurement system was tested on a pelvis phantom against a digital inclinometer. A new smartphone-based navigated ultrasound system was used to perform the measurements. The sample consisted of 12 symptom-free young adults. A multivariate regression model was used to analyze the data. The subjects’ pelvis in supine position was significantly more tilted anteriorly (mean PT = −7.3°, 95% C.I.: −10.6 to −3.9) than in upright position (mean PT = 0.8°, 95% C.I.: −2.5 to 4.1) (mean. diff. 8.1°; p < 0.001). Rater and trial order had no significant effects on the measured PT angles (p = 0.5). The accuracy of the system when measuring PT angles on the pelvis phantom was 0.3° (0.1° to 0.7°) and 0.2° (−0.09° to 0.6°) for the supine and upright positions respectively. Pelvic tilt angles differed significantly between the supine and the upright position in symptom-free young adults. Concurrent validity showed no differences for measurements in the upright position and small (under 0.4°) significant differences for measurements in the supine position.