Effect of simulating leg length inequality on pelvic torsion and trunk mobility.

Although techniques such as roentgenograms and magnetic resonance imaging can provide definitive information about leg length inequality, they are not easily implemented for screening purposes. Using relative heights of palpated iliac crests as criteria for determining degree of lateral pelvic tilt, we examined the immediate effect of simulating leg length inequality on pelvic torsion and trunk flexion. In seven healthy men and 22 healthy women, 18-28 years of age, a lift of at least 15 mm was placed under either foot to laterally tilt the pelvis 1.2 degrees or more. In eight subjects with pre-existing lateral pelvic tilts of 1.8 degrees or more, a lift was also used to eliminate the tilt. We examined how this tilting affected torsion between the innominates and mobility of the trunk. The innominate contralateral to the lift became more anteriorly rotated than the ipsilateral innominate and lateral flexion of the trunk increased toward the side of the lift. Both of these effects can be associated with clinical leg length inequality, so a lateral pelvic tilt on the order of 1.2 degrees, if encountered in the clinic, should signal the suitability of more extensive examination for possible lower limb asymmetry.