Development of a noninvasive measure of pelvic and hip angles in seated posture

To develop a valid noninvasive means to measure pelvic tilt and hip angle in seated posture.

Validation cohort study using radiographs as a criterion standard for pelvic posture.

Rehabilitation hospital.

Volunteer sample of 10 adult men with no known physical disability.

Radiographs were taken as subjects sat in erect, anterior, and posterior postures. An electromagnetic tracking device was as a pointer to digitize the anterior superior and posterior superior iliac spines and as a 6 degrees of freedom (df) sensor mounted on the thigh and sacrum.

Variables included pelvic tilt and hip flexion angle. Intra- and interrater reliability of radiographic measures was determined by using intraclass correlation coefficient comparison of the results from 2 investigators. Validity was determined by comparing noninvasive measures of pelvic and hip angles to radiographic measures by using correlation, analysis of variance (ANOVA), and regression.

Reliability of radiographic measures of pelvic tilt and hip angles were >/=.98. Pelvic tilt comparison: pointer: r=.89, R(2)=.80; 6-df sensor: r=.91, R(2)=.83; hip angle comparison using 6-df sensor: r=.78 with average difference of 4.25 degrees. ANOVA showed that differences between all invasive and noninvasive measures did not differ significantly (P>.05).

Results indicated excellent reliability of radiographic analysis techniques and represented an improvement over previously published techniques. Noninvasive measures of pelvic tilt and hip angle were shown to be valid.