Measuring leg-length discrepancy by the "iliac crest palpation and book correction" method: reliability and validity.

Abstract

To determine the reliability and validity of a clinical measurement of leg-length discrepancy (LLD), by using the iliac crest palpation and book correction (ICPBC) method. Intra- and interrater reliability and validity determinations. Rehabilitation center. Thirty-four healthy subjects, none of whom had an apparent LLD, as determined by iliac crest palpation. We induced a simulated LLD (7-53 mm) for each subject. To measure the LLD, the examiner performed the ICPBC method by palpating the iliac crests and correcting identified differences with a book opened to the required number of pages. The thickness of the book correction was measured. Reliability LLD measurement (n = 20), by using the ICPBC method to measure the LLD; construct validity (n = 34), comparing ICPBC measurement with the extent of the induced LLD; and concurrent validity (n = 14), the difference in heights of the superior aspect of the femoral heads from standing radiographs. The intraclass correlation coefficients (ICCs) for the intrarater and interrater reliabilities were.98 and.91, respectively. The ICCs for the construct and concurrent validities were.62 and.76, respectively. The ICPBC method underestimated the induced LLD by a mean difference +/- standard deviation of 3.8 +/- 10.3mm (p =.055) and the radiologic measure by 5.1 +/- 8.6 mm (p =.043). The ICPBC technique for measuring LLD is highly reliable and moderately valid. When there is no history of pelvic deformity and the iliac crests can be readily palpated, we recommend using iliac crest palpation to detect LLD, and the book correction to quantify it.