Transitional Lumbosacral Vertebra

Vote for the Correct Spine Labeling • Xray of the Week 2016 • Week #46

RADIOLOGISTS - It's not too late to vote! This could have serious consequences for several years. If you do not like either of the major candidates, please pick C.

To vote, reply with A or B, or C in the comments. Sorry, but there are no secret ballots. The votes will be tallied, and the winner announced on Friday.

Fig. 1. A & B: Two ways of labeling the same image. Either one could be correct Fig. 1. C: "I do not know" is the correct answer.

Transitional lumbosacral vertebrae are a relatively common variant and can be seen in 15-35% of the general population [1-3]. If this variant is not recognized or not correctly described in the report, there is a risk of wrong level surgery or other spine intervention such as injection [3,4]. It is essential to evaluate all preoperative imaging modalities before reporting the levels on intraoperative images. If preoperative images are not available and the surgeon is insistent on providing a level in the report, we use the following preamble: "For the purposes of this report, the last apparent true disc level is considered to be L5-S1. Based on this, the posterior surgical instrument is present overlying the ___ level." If there is no absolute requirement to state a level in the report, one can use the following verbiage: "This ia a limited lateral intraoperative radiograph for the purpose of localization. Please refer to the operative report including designation of the operative levels by the surgeon."

Fig. 2. The iliolumbar ligaments (blue arrows).

The iliolumbar ligament is fairly reliable anatomic structure which can be used to determine the lumbosacral numbering scheme (Fig. 2). Best seen on CT scan, the iliolumbar ligament frequently arises from the transverse process of L5. However, due to wide variability in the number of vertebral segments, the iliolumbar ligament does not always indicate the L5 level. It actually merely identifies the lowest lumbar-type vertebral segment [1].

References:

1. Carrino JA, Campbell PD, Lin DC et-al. Effect of Spinal Segment Variants on Numbering Vertebral Levels at Lumbar MR Imaging. Radiology. 2011;259 (1): 196-202.

2. Uçar D, Uçar BY, Coşar Y et-al. Retrospective cohort study of the prevalence of lumbosacral transitional vertebra in a wide and well-represented population. Arthritis. 2013;2013: 461425.

3. Konin GP, Walz DM. Lumbosacral transitional vertebrae: classification, imaging findings, and clinical relevance. AJNR Am J Neuroradiol. 2010;31 (10): 1778-86. AJNR Am J Neuroradiol.

4. Bron JL, van Royen BJ, Wuisman PI. The clinical significance of lumbosacral transitional anomalies. Acta Orthop Belg. 2008;73 (6): 687-95.

Kevin Rice, MD serves as the Chair of the Radiology Department of Valley Presbyterian Hospital in Los Angeles, California and is a radiologist with Renaissance Imaging Medical Associates. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015 Dr. Rice launched Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" award for the Most Effective Radiology Educator.

Follow Dr. Rice on Twitter @KevinRiceMD

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