The effect of imposed leg length difference on pelvic bone symmetry.

This study was designed to examine the effect of varying degrees of imposed leg length difference on symmetry of the innominate bones in healthy college women with relatively equal leg lengths. Subjects' leg length was determined by clinical and roentgenographic procedures. Position of the innominate bones with and without lifts under one foot was measured with respect to the transverse plane using the Waterloo Spatial Motion and Recording Technique (WATSMART; Northern Digital, Inc., Waterloo, Ontario, Canada), which allows very high spatial resolution. Our results show that posterior innominate bone rotation occurs on the side of the lengthened limb, and anterior rotation occurs on the shorter limb. The amount of pelvic obliquity increased in an approximately linear fashion as the leg length difference was increased from 2/8 to 7/8 inch. Some individual differences were evident.