Relationship between limb length discrepancy and load distribution across the sacroiliac joint--a finite element study.

We assessed the relationship between leg length discrepancy (LLD) and the load distribution across the sacro-iliac joint (SIJ). A finite element model of the spine-pelvis was developed with different amounts of LLD by increasing the length of the right femur in the model. Peak stresses and contact loads across the SIJ were computed for different amounts of LLD (1, 2, and 3 cm). The load and the peak stresses across the SIJ articular surfaces progressively increased with the increase in the LLD. Trying to offset the LLD surgically by lengthening of the short side, shortening or stunting the growth (epiphysiodesis) of the long side, or by shoe lifts should decrease the load across the SIJ and should theoretically decrease SIJ pain.