A New Approach to the Measurement of Pelvic Asymmetry: Proposed Methods and Reliability

Abstract

ObjectiveThis is a methodological study presenting a novel method of pelvic asymmetry (PA) measurement for use in the research laboratory setting. The purpose of the study is (1) to establish intrarater and interrater reliability of the proposed measures of PA, (2) to verify the influence of repeated measurements on the reliability, and (3) to assess correlation between the proposed measures of PA. MethodsTwelve healthy volunteers participated, and 2 teams of raters were involved. Registration of anatomic landmarks’ positions in the optical motion capture system was repeated 3 times. Two asymmetry indexes were calculated: for pelvic torsion and for lateral pelvic tilt. Interclass correlation coefficients (ICCs), standard errors of measurement, and smallest detectable differences were used to describe the intrarater and interrater reliability of the 2 indexes. ResultsAfter 2 repeated registrations of pelvic landmarks’ positions, the reliability of our asymmetry indexes was good and excellent. The ICCs for intrarater reliability ranged from 0.96 to 0.97; the ICCs for interrater reliability ranged 0.81 to 0.90. There was moderate, nonsignificant correlation between asymmetry indexes for pelvis torsion and for lateral pelvic tilt (r = 0.45, P = .14). ConclusionThe 2 proposed asymmetry indexes showed good and excellent intrarater and interrater reliability after 2 repeated registrations of pelvic landmarks’ positions and thus may be useful in the research laboratory setting. However, these indexes are not strongly correlated, which suggests that the 2 types of PA may constitute different clinical entities.