Role of Iliolumbar Ligament in Identification of L5 Vertebra on MRI in Lumbosacral Transitional Anomalies

Labeling a transitional vertebra (lumbarization or sacralization) as "LSTV" helps in simplifying the reporting process but leads to mis-numbering and must be avoided, as reliable identification of vertebral levels is essential for surgical interventions and image guided interventions. Many parameters have been described to identify the vertebral level; however, there are contradictory results in literature regarding their usefulness. Objective: To determine the role of iliolumbar ligament (ILL) on MRI as an identifier of the L5 vertebra in cases of LSTV anomalies. Methods: 200 patients with confirmed L5 level (identified on MRI screening of whole spine) were included in the study. These were further divided into group I (159 patients), II (31 patients) and III (10 patients) consisting of normal spine, spine with sacralization and with lumbarization respectively. The level(s) of origin of the ILL was documented in all of them and analysis was done. Results: ILL was found bilaterally in all patients. All patients with normal lumbosacral junction had ILL arising from L5 bilaterally. Among sacralization group, 23 patients had ILL arising from L4, 2 patients had ILL arising from L5 and 6 patients had ILL arising from L4 on sacralized side and from L5 contralaterally. Among Lumbarization group 2 patients had ILL arising from S1, 5 patients had ILL arising from L5 and 3 patients had ILL arising from S1 on side of lumbarization and from L5 contralaterally. Conclusion: Our study demonstrated that ILL is not a reliable identifier of the L5 vertebra in the setting of LSTV anomalies. It rather identifies the lowest lumbar-type vertebral segment only.

A Cadaver Study of Iliolumbar Ligament from a Viewpoint of Surface Anatomy

OBJECTIVE: To assess the anatomical relationship between spinous process of the lumbar vertebrae and iliolumbar ligament from a viewpoint of surface anatomy. METHOD: Fourteen iliolumbar ligaments of seven human cadavers were dissected and measured distance from the lumbar spinous process to the iliolumbar ligament and vertical depth of iliolumbar ligament from the skin surface. RESULTS: All 14 iliolumbar ligaments were originated at the L5 transverse process and inserted in anterior surface of the iliac crest. Direct distance from lumbar spinous process to the origin siteof the iliolumbar ligament was 7.67+/-0.39 cm(distance from the spinous process to presumed skin point of the termination site of the ligament, 6.71+/-0.4 cm). Vertical depth from skin surface was 3.94+/-0.57 cm to the origin site of the iliolumbar ligament, and 3.67+/-0.54 cm to the termination site of the iliolumbar ligament. CONCLUSION: The iliolumbar ligament was deep seated anatomical structure in the lumbosacral region. Superficial landmark of the lumbar spinous process may be useful in approach to iliolumbar ligament.

The Relationship between the Lower Lumbar Disc Herniation and the Morphology of the Iliolumbar Ligaments Using Magnetic Resonance Imaging

OBJECTIVE: This research aimed to define the relationship between the lower lumbar disc herniation and the morphology of the iliolumbar ligaments using magnetic resonance imaging. METHOD: 24 male and 36 female patients were classified into two groups according to their disc herniation grade- those in whom the L5-S1 disc was less herniated than L4-5 disc, those in whom the L5-S1 disc was more herniated than the L4-L5 disc on magnetic resonance images. The lengths of iliolumbar ligaments were measured on T1- weighted coronal images. The angles of iliolumbar ligaments were measured on T1-weighted axial images. RESULTS: The length of iliolumbar ligament was not different between L4-L5 disc herniation and L5-S1 disc herniation. The degree of iliolumbar ligament angle difference (asymmetry of direction) at L5-S1 disc herniation was more deviated in paracentral disc herniation compared with central disc herniation. CONCLUSION: The morphology of the iliolumbar ligament, especially its asymmetry of direction, may be a factor influencing the development of disc herniation at L5-S1.