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


METHODS
The examination chair allowed measurement of IR in a sitting position simultaneously in both hips, with hips and knees flexed 90 degrees, 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 degrees 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.


RESULTS
Inter-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 <or=0.001). The average range of motion (ROM) obtained with examination chair and clinical assessment were similar (difference 1.1 degrees, 95% CI - 0.7-2.8 degrees, P=0.23), and the correlation was strong (Pearson's coefficient, 0.75, 95% CI 0.62-0.84).


CONCLUSIONS
The 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.
Reichenbach
S
S
Division of Clinical Epidemiology and Biostatistics, Institute of Social and Preventive Medicine (ISPM), University of Bern, Bern, Switzerland. rbach@ispm.unibe.ch
Jüni
P
P
Nüesch
E
E
Frey
F
F
Ganz
R
R
Leunig
M
M
D001696:Biomechanical Phenomena; D004867:Equipment Design; D004864:Equipment and Supplies; D006615:Hip / Q000033:anatomy & histology*; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D008297:Male; D015207:Osteoarthritis, Hip / Q000503:physiopathology*; D016059:Range of Motion, Articular; D012016:Reference Values; D012399:Rotation; D013557:Switzerland; D055815:Young Adult