Serge Martellacci MD, Presenter: Nothing to Disclose

Francois Cotton MD, PhD, Abstract Co-Author: Nothing to Disclose

Serge Ludwig Aho-Glélé, Abstract Co-Author: Nothing to Disclose

Guillaume Koch, Abstract Co-Author: Nothing to Disclose

Douraied Ben Salem MD,PHD, Abstract Co-Author: Nothing to Disclose

Previous radiologic work on the iliolumbar ligament (ILL) was performed using MRI. We propose a simple method, which can be applied in lumbar spine CT, for identifying L5 especially when there is a transitional lumbosacral vertebrae.

This retrospectif  work is based on the study of 500 spine CT (150 cervico-thoraco-lumbo-sacral CT and 350 thoraco-lumbo-sacral CT) extracted from the radiology information system of a university hospital center. Our sample included  237 women and  263 men. We used multiplanar (coronal, sagittal and axial ) reconstructions  on the spine  to examine the different insertions of the ILL according to the various configurations of the lumbosacral junction.  

Lumbosacral transitional vertebra was found in this study in 9.8% of this population. In standard cases, the insertion of the ILL is in 95% of the cases, exclusively found on the transverse processes of L5 (Figure 1). The diagnostic pitfalls can occur in cases of surnumerary lumbar vertebrae (2.4%), and in cases of ectopic vertebral insertions: An exclusive insertion of ILL was on L4 in 0.4% of cases. A double insertion on L4 and L5 was observed in  0.6% of cases.  A double insertion on L5 and S1 was depicted in 1.6% of cases. 

The ILL can be identified easily on lumbar spine CT studies, allowing an accurate identification of the level of L5 in 95% of cases.

The iliolumbar ligament is readily identifiable on axial lumbar spine CT allowing an accurate identification of the level of L5 in 95% of cases.

Martellacci, S, Cotton, F, Aho-Glélé, S, Koch, G, Ben Salem, D, Numbering of Lumbosacral Transitional Vertebrae on CT Scan: Interest of the Iliolumbar Ligament.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11015445.html