RELATIONSHIP OF THE PELVIC ANGLE TO THE SACRAL ANGLE - MEASUREMENT OFCLINICAL RELIABILITY AND VALIDITY

There is a need to better document the reliability and validity of ass essment measures used in physical therapy. Studies documenting the rel iability of measurement of the pelvic angle and its relationship to sa cral motion are presently inconclusive. The purpose of this study was twofold. First, we wanted to determine the reliability and validity of a goniometric measurement of the pelvic angle. We also wanted to test the hypothesis that there is a relationship between the pelvic angle and the sacral angle. Intertester and intratester reliability of gonio metric pelvic angle measurements of 23 healthy young adults were exami ned using three different raters. Radiographic measurements of the pel vic and sacral angle using two raters and goniometric measurement of t he pelvic angle using a single rater were taken from 15 patients with low back pain who had been referred for X-rays. Intraclass correlation coefficients (ICCs) of intratester reliability for goniometric measur ements of the pelvic angle were .93, .96, and .96. The intertester rel iability was .95. The ICCs for intratester reliability for radiologica l measurements were .92 and .95 for the sacral angle and .98 for both measurements of the pelvic angle. Intertester reliability coefficients were .86 and .88, respectively. The Pearson correlation coefficients for the goniometric and radiological measurements of the pelvic angle were .85 and .68. A comparison of the radiological and goniometric mea surements of the pelvic angle with the sacral angle demonstrated low a verage correlations of .43 and .58, respectively. The results indicate a high level of correlation between and within testers for goniometri c measurements of the pelvic angle but only a fair correlation between goniometric and radiological measurements of the pelvic angle. A poor correlation was noted between the pelvic angle and the sacral angle. We suggest further examination of measurements correlating the pelvic angle and the sacral angle. Studies comparing several X-rays of the sa me patient by examining the pelvis at different positions would better demonstrate a relationship between the pelvic angle and the sacral an gle.