Reliability of transverse plane pelvic alignment measurement during the bridge test with unilateral knee extension.

Background: The bridge test with unilateral knee extension evaluates the stability of the trunk and pelvis. The evaluation of this stability can contribute to the understanding of the occurrence of musculoskeletal injuries.

Objectives: To investigate the intra- and inter-rater reliability of a qualitative analysis and intra-test reliability of a quantitative analysis of transverse plane pelvic alignment during the bridge test with unilateral knee extension.

Method: Thirty participants (24.73±4.24 years old) were tested. The qualitative analysis was conducted by asking two raters to judge the transverse plane pelvic alignment and its reliability was assessed with the weighted kappa coefficient (k(w)). The quantitative analysis was conducted by measuring the greatest pelvic tilt angle in transverse plane and its reliability was assessed by use of the intraclass correlation coefficient (ICC); the mean change, which was evaluated using 95% confidence interval of the mean difference (95%CI d) and Bland-Altman plot; and the quantification of measurement variability, which was assessed using standard error of measurement (SEM) and the coefficient of variation of the typical error (CVTE). In addition, the minimal detectable change (MDC₉₅) was determined.

Results: The intra-rater reliability ranged from fair to moderate (k(w)=0.32 to 0.58) and the inter-rater reliability was substantial (k(w)=0.80). The intra-test reliability was excellent (ICC=0.82), the 95%CI d ranged from -0.51º to 1.99º, the SEM was 2.38° and the CV(TE) was 28.75%. The MDC₉₅ was 6.59°.

Conclusions: The inter-rater reliability was greater than the intra-rater reliability; the intra-test reliability was excellent and showed no systematic or random error.