Kinematic and kinetic asymmetry in patients with leg-length discrepancy

The symmetry index (SI), as one of methods to evaluate gait pattern in pati ents with leg-length discrepancy (LLD), helps to estimate the acceptable ra nge of inequality and to determine symmetry in the kinematic and kinetic da ta before and after a heel lift, although this parameter has a large standa rd deviation that undermines its accuracy. Thirty patients with LLD were st udied by st motion-analysis system and a force plate. Joint motion of the l ower extremity in the sagittal plane, back movement in the coronal plane, a nd three-dimensional ground-reaction forces (GRFs) were registered. From a linear-regression analysis, a mean value of inequality of 2.33 cm (range, 2 .12-2.54) was found to correspond to an acceptable gait symmetry. After a h eel lift, the SI of the pelvic tilt at midstance and of the vertical GRF at initial contact increases significantly, but the SI of the medial GRF at t erminal stance decreases. Patients with an inequality of a mean value of 0. 51 cru determined by palpating bilaterally the top of the iliac crest (the TIC1 subgroup) showed a lesser value of the SI of the center of pressure in the forward direction during stance compared with the group with a mean va lue of inequality of 1.39 cm (the TIC2 subgroup). As a result of our findin gs, we conclude that the effect of the amount of correction by a heel lift on gait symmetry is unpredictable.