Does the morphology of the iliolumbar ligament affect lumbosacral disc degeneration?

Study Design. An anatomic study of the iliolumbar ligament was performed in association with lumbosacral disc degeneration. Objectives. To determine whether the morphology of the iliolumbar ligament contributes to lumbosacral disc degeneration. Summary of Background Data. There have been few reports concerning the clinical significance of the iliolumbar ligament. Methods. We dissected 25 male and 27 female cadavers and measured the length and cross-sectional area of the anterior and posterior bands of the iliolumbar ligament. The specimens were classified into three groups based on the grade of L4-L5 and L5-S1 disc degeneration: the L4-L5 disc was more degenerated than the L5-S1 disc (group L), the L4-L5 disc was less degenerated than the L5-S1 disc (group S), and both discs were equally degenerated (group E). The results were statistically compared among the three groups. Results. The length of the posterior bands and the summation of the length of the anterior and posterior bands were significantly shorter in group L than in group S, and the cross-sectional area of the posterior bands and the summation of the cross-sectional area of the anterior and posterior bands were significantly larger in group L than in groups S or E in the male cadaver specimens. Conclusion. If the iliolumbar ligaments (especially the posterior band of the ligament) of a male patient are short and have a large cross-sectional area, the lumbosacral junction can be stabilized by the ligaments, with the L5-S1 disc being protected from degeneration. The L4-L5 disc may be prone to degeneration.