Effects of leg length discrepancies on the forces at the hip joint.

The authors questioned whether leg length discrepancies of the magnitude ordinarily seen after total hip reconstruction (<2 cm) would substantially alter hip joint forces. Using conventional gait analysis techniques to ascertain intersegmental resultant hip forces and moments, the authors used lifts to simulate leg length discrepancies of 2.3, 3.5, and 6.5 cm in 7 normal subjects. The 2.3-cm lift produced no changes. On the side of the lift (long limb), the 3.5- and 6.5-cm lifts modestly decreased mean peak intersegmental resultant hip forces by 6% and 12%, respectively, but not moments. The changes were, however, variable, with a few subjects showing increases and the rest showing decreases in selected forces or moments. On the side opposite to the lift (short limb), the 3.5- and 6.5-cm lifts increased mean peak intersegmental resultant hip forces by 2% to 12%, but not moments except in 1 case (8%). It is concluded that leg length discrepancies of the sort commonly seen after total hip reconstruction would likely cause no substantial changes in hip forces.