An examination chair to measure internal rotation of the hip in routine settings: a validation study

SummaryObjectiveTo determine the performance of a newly developed examination chair as compared with the clinical standard of assessing internal rotation (IR) of the flexed hip with a goniometer.MethodsThe examination chair allowed measurement of IR in a sitting position simultaneously in both hips, with hips and knees flexed 90°, lower legs hanging unsupported and a standardized load of 5 kg applied to both ankles using a bilateral pulley system. Clinical assessment of IR was performed in supine position with hips and knees flexed 90° using a goniometer. Within the framework of a population-based inception cohort study, we calculated inter-observer agreement in two samples of 84 and 64 consecutive, unselected young asymptomatic males using intra-class correlation coefficients (ICC) and determined the correlation between IR assessed with examination chair and clinical assessment.ResultsInter-observer agreement was excellent for the examination chair (ICC right hip, 0.92, 95% confidence interval [CI] 0.89–0.95; ICC left hip, 0.90, 95% CI 0.86–0.94), and considerably higher than that seen with clinical assessment (ICC right hip, 0.65, 95% CI 0.49–0.77; ICC left hip, 0.69, 95% CI 0.54–0.80, P for difference in ICC between examination chair and clinical assessment ≤0.001). The average range of motion (ROM) obtained with examination chair and clinical assessment were similar (difference 1.1°, 95% CI – 0.7–2.8°, P = 0.23), and the correlation was strong (Pearson's coefficient, 0.75, 95% CI 0.62–0.84).ConclusionsThe use of the examination chair resulted in a precise assessment of hip IR in our population-based inception cohort study of young asymptomatic males. It was strongly correlated with standard clinical assessment of IR but was considerably more reliable.