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Summary: Pelvic radiographs of 25 children aged 6 months to 2 years had the acetabular index measured 3 times by each of five pediatric orthopaedists. Interobserver measurements were found to vary ±3.0°, whereas the intraobserver variation was ±3.6°. This error reflects only measurement error and does not consider error introduced with different positioning of the pelvis.
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Spatz et al. (1997) studied this question.
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