December 2022
Dear First name / Colleague,
 
Happy Holidays!  
 
New Releases

 
Partum pearls
 
Have we been using Tuffier's line incorrectly in pregnant patients? 🤰🏾👀
 
The intercristal line (also known as Tuffier’s or Jacoby's line) is an often misinterpreted radiologic finding. The intercristal line is an imaginary horizontal line drawn across the highest points of both iliac crests in an anteroposterior lumbar radiograph [1] (below left). Why was this line proposed by Dr. Jacoby (American Neurologist) in 1895 and Dr. Tuffier (French Surgeon) in 1900?
 
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         Intercristal Line on an AP Lumbar Radiograph                          
Modified from  https://e-safe-anaesthesia.org/sessions/09_05/d/ELFH_Session/1290/tab_5071.html
The spinal cord in most adults terminates at L1-L2, and there are risks associated with performing subarachnoid injections above this level. Dr. Jacoby first proposed that the horizontal intercristal line be used as a landmark for the L4 vertebral body [2]. Five years later, Dr. Tuffier suggested that the same line intersected the L4-L5 intervertebral disk [3]. The use of this line has been encouraged in an effort to promote accurate numbering of the lumbar vertebrae, thereby reducing the probability of spinal cord injury from neuraxial procedures. 
 
Many anesthesia providers are taught the following:
  1. The intercristal/Tuffier's/Jacoby's line can be approximated by palpating the posterior superior iliac spine (PSIS).
  2. The PSIS represents the L4-L5 vertebral interspace.
Let's explore these dogmas.
 
Is palpation of the PSIS an acceptable surrogate for the L4-L5 vertebral interspace in pregnant patients?
 
A 2010 study by Margarido et al [4] demonstrated that among 45 pregnant women at term, the palpated PSIS was actually located above the L4-L5 interspace in all of the subjects, and the median level of intersection was immediately below the L2-L3 interspace. In this study, interspaces that correlated with the PSIS ranged from immediately above L1-L2 to immediately above L4-L5. 
 
A larger study of 300 participants published by Malik et al [5] in 2020 also demonstrated poor correlation between the palpated PSIS and the ultrasound-identified L4-L5 interspace, particularly in patients who were pregnant and/or obese. This information should be taken into consideration while performing neuraxial procedures, especially for spinals and DPEs/CSEs, where entry into the thecal sac is intentional.  
Our impressions: With the introduction of neuraxial ultrasound, we are now able to debunk the longstanding dogma that PSIS is a surrogate for the L4-L5 interspace in pregnant patients. 
  • The posterior superior iliac spine is not the same thing as Tuffier's/Jacoby's/intercristal line, nor is it an accurate surrogate. 
  • In obese and term parturients, PSIS may intersect the spine as high as L1, with a median level of intersection around L2-L3.
  • Neuraxial ultrasound is a more accurate way to determine vertebral level. 
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1 Thapa S, Bell D, Hacking C, et al. Intercristal line. Reference article, Radiopaedia.org (Accessed on 21 Dec 2022) https://doi.org/10.53347/rID-47501
2 Jacoby GW. Lumbar puncture of the subarachnoid space. NY Med J. 1895;62:81M8.
3 Tuffier T. Anesthesie medullaire chirurgicale par injection sousarachnoidienne lombaire de cocaine; technique et results. Sem Med 1900.
4 Margarido, C.B., Mikhael, R., Arzola, C. et al. The intercristal line determined by palpation is not a reliable anatomical landmark for neuraxial anesthesia. Can J Anesth/J Can Anesth 58, 262–266 (2011). https://doi.org/10.1007/s12630-010-9432-z
5 Malik M, Ismail S. Accuracy of Tuffier's Line Identification by Palpation Method: Cross-Sectional Comparative Study Among Obese, Pregnant and Control Groups. Turk J Anaesthesiol Reanim. 2020 Apr;48(2):108-114. doi: 10.5152/TJAR.2019.82346. Epub 2019 Oct 17. PMID: 32259141; PMCID: PMC7101188.6  
 

 
Wishing you all a happy & healthy holiday season!
 
with gratitude,
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& the SafePartum Team
 
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