Comparison of the intra-rater and inter-rater reliability of two methods to measure tibial torsion: the gravity goniometer and the footprint method.

Abstract

Aim: To investigate the intra-rater and inter-rater reliability of the gravity goniometer and footprint method in measurement of tibial torsion and to investigate the agreement between the use of the gravity goniometer and the footprint method. Method: Twenty-two healthy participants (ten male and twelve female) had both footprint method and gravity goniometer measurements taken by three raters. Data collected occurred over three days, where participants attended two sessions. Raters and participant numbers were randomised. One researcher recorder data, to allow for blinding or raters from their measurements. Data analysis was performed using intraclass correlation coefficient (ICC) and Bland and Altman limits of agreement, to determine both inter and intra-rater reliability and agreement between methods. Results: The intra-rater reliability was excellent for both the gravity goniometer and the footprint method (0.64 and 0.67 respectively). Bland and Altman showed poor agreement with 18.82 between gravity goniometer measurements and 24.66 between footprint method. The inter-rater reliability showed moderate and poor ICC for gravity goniometer and footprint method (0.46 and 0.28). For agreement of the two methods Bland and Altman's limits of agreement showed 19.96 between limits of agreement. Conclusion: The results suggest that both gravity goniometer and footprint method have excellent intra-rater reliability, and both show poor inter-rater reliability. There is a large disagreement between methods, showing its lack of clinical suitability to use interchangeably. Additional research should be carried out to determine further suitability, and both methods should be compared to a gold standard.