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

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