Abstract
Objective
To evaluate the value of psoas muscle proximal insertion for correct numbering of the lumbar vertebrae in MRI, in particular in case of lumbosacral transitional vertebra (LSTV).
Methods
Two radiologists assessed 477 MRI scans of the lumbar spine with a sagittal localizer sequence on the whole spine for numbering vertebrae caudally from C2. Proximal insertion of the psoas was determined as the most proximal vertebra with psoas over half of its body on coronal T2 STIR sequence. The last lumbar vertebra was named considering both its number and the presence or absence of LSTV according to Castellvi classification. These same parameters were also assessed on 207 PET-CT scans of another cohort including the whole spine.
Results
Proximal insertion of the psoas was L1 in 94.1% of cases: 98.5% in case of modal anatomy, 81.4% in case of LSTV, and 51.7% in case of missing or supernumerary lumbar vertebra without LSTV. There was no statistically significant difference between MRI and CT data. The inter-reader agreement for determination of psoas proximal insertion was excellent (kappa = 0.96).
Conclusion
Proximal insertion of the psoas muscle is a helpful marker for correct numbering of the lumbar vertebrae in MRI and to detect a complete lumbosacral segmentation anomaly.
Key Points
• Proximal insertion of the psoas muscle can be easily identified on a coronal T2 STIR sequence.
• Psoas proximal insertion on the spine almost always designates the first lumbar vertebra and is helpful to accurately number all lumbar vertebrae, especially in case of lumbosacral transitional vertebra.
• Conversely, when psoas muscle does not insert five lumbar bodies above the apparent lumbosacral joint, the probability of variation in the number of lumbar vertebrae is high.
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Abbreviations
- HU:
-
Hounsfield units
- LSTV:
-
Lumbosacral transitional vertebra
- MRI:
-
Magnetic resonance imaging
- PACS:
-
Picture archiving and communication system
- PET-CT:
-
Positron emission tomography-computed tomography
- STIR:
-
Short tau inversion recovery
- TE:
-
Echo time
- TI:
-
Inversion time
- TR:
-
Repetition time
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Acknowledgments
The authors thank Philippe Bruyant for his help with manuscript revision.
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The scientific guarantor of this publication is Dr. Garetier Marc.
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The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.
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One of the authors has significant statistical expertise.
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Written informed consent was obtained from all subjects in this study.
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Methodology
• Prospective and retrospective
• Observational
• Performed at one institution
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Ropars, F., Mesrar, J., Ognard, J. et al. Psoas proximal insertion as a simple and reliable landmark for numbering lumbar vertebrae on MRI of the lumbar spine. Eur Radiol 29, 2608–2615 (2019). https://doi.org/10.1007/s00330-018-5798-z
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DOI: https://doi.org/10.1007/s00330-018-5798-z