Anatomical landmark position – Can we trust what we see? Results from an online reliability and validity study of osteopaths

Abstract

BackgroundPractitioners traditionally use observation to classify the position of patients' anatomical landmarks. This information may contribute to diagnosis and patient management. ObjectivesTo calculate a) Inter-rater reliability of categorising the sagittal plane position of four anatomical landmarks (lateral femoral epicondyle, greater trochanter, mastoid process and acromion) on side-view photographs (with landmarks highlighted and not-highlighted) of anonymised subjects; b) Intra-rater reliability; c) Individual landmark inter-rater reliability; d) Validity against a ‘gold standard’ photograph. Design: Online inter- and intra-rater reliability study. SubjectsPhotographed subjects: convenience sample of asymptomatic students; raters: randomly selected UK registered osteopaths. Methods40 photographs of 30 subjects were used, a priori clinically acceptable reliability was ≥0.4. Inter-rater arm: 20 photographs without landmark highlights plus 10 with highlights; Intra-rater arm: 10 duplicate photographs (non-highlighted landmarks). Validity arm: highlighted landmark scores versus ‘gold standard’ photographs with vertical line. Research ethics approval obtained. RatersOsteopaths (n = 48) categorised landmark position relative to imagined vertical-line; Gwet's Agreement Coefficient 1 (AC1) calculated and chance-corrected coefficient benchmarked against Landis and Koch's scale; Validity calculation used Kendall's tau-B. ResultsInter-rater reliability was 'fair' (AC1 = 0.342; 95% confidence interval (CI) = 0.279–0.404) for non-highlighted landmarks and 'moderate' (AC1 = 0.700; 95% CI = 0.596–0.805) for highlighted landmarks. Intra-rater reliability was 'fair' (AC1 = 0.522); range was ‘poor’ (AC1 = 0.160) to ‘substantial’ (AC1 = 0.896). No differences were found between individual landmarks. Validity was ‘low’ (TB = 0.327; p = 0.104). ConclusionBoth inter- and intra-rater reliability was ‘fair’ but below clinically acceptable levels, validity was ‘low’. Together these results challenge the clinical practice of using observation to categorise anterio-posterior landmark position.