Intra‐ and Inter‐rater Reliability of Navigated Ultrasound in the Assessment of Pelvic Tilt in Symptom‐Free Young Adults

Objectives Pelvic tilt is the angle between the anterior pelvic plane and the coronal plane. It affects cup positioning in total hip arthroplasty. The primary objective of this study was to test the intra‐ and inter‐rater reliability of a navigated smart device–based ultrasound system for pelvic tilt assessment. The secondary objective was to test the inter‐rater variability of the measurements on a hip phantom. Methods A repeated‐measures design was used. Two raters measured the pelvic tilt of 12 symptom‐free young adults in upright and supine positions. Additionally, pelvic tilt was measured on a hip phantom. Each rater performed 3 measurements in each body position on the participants and 12 measurements on the hip phantom. Intra‐ and inter‐rater reliability were calculated with the use of intraclass correlation coefficients. The variability in measurements on the hip phantom was assessed by a Bland‐Altman analysis of agreement. Results Intraclass correlation coefficient 95% confidence intervals for intra‐rater reliability ranged from good to excellent and moderate to excellent for the supine and upright positions respectively. Intraclass correlation coefficient 95% confidence intervals for inter‐rater reliability ranged from poor to excellent for both positions. Hip phantom measurements showed no significant average bias (P > .05) and no significant proportional bias (P > .05). The 95% inter‐rater limits of agreement were ±1.3° and ±1.7° for the supine and upright positions, respectively. Conclusions The intra‐rater reliability values achieved were suitable. Intraclass correlation coefficient values for inter‐rater reliability remained below an acceptable level. Possible reasons and overcoming strategies were presented. The 95% limits of agreement were good, at less than ±2°.