Brazilian Journal of Anesthesiology
Brazilian Journal of Anesthesiology
Clinical Research

Correlation of the epidural space measured intraoperatively and estimated by MRI or US: an observational study

Correlação entre a profundidade do espaço peridural medida no intraoperatório e a estimada por RM ou US: estudo observacional

Mehmet Canturk, Nazan Kocaoglu, Meltem Hakki

Downloads: 0
Views: 252


Background and objectives
To assess the agreement between the epidural depth measured from the surgical site with the epidural depths estimated with magnetic resonance imaging (MRI) and ultrasound scanning.

Fifty patients of either sex, scheduled for L4‒5 lumbar disc surgery under general anesthesia were enrolled in this prospective observational study, and the results of 49 patients were analyzed. The actual epidural depth was measured from the surgical site with a sterile surgical scale. The MRI-derived epidural depth was measured from the MRI scan. The ultrasound estimated epidural depth was measured from the ultrasound image obtained just before surgery.

The mean epidural depth measured from the surgical site was 53.80 ± 7.67 mm, the mean MRI-derived epidural depth was 54.06 ± 7.36 mm, and the ultrasound-estimated epidural depth was 53.77 ± 7.94 mm. The correlation between the epidural depth measured from the surgical site and MRI-derived epidural depth was 0.989 (r2 = 0.979, p < 0.001), and the corresponding correlation with the ultrasound-estimated epidural depth was 0.990 (r2 = 0.980, p < 0.001).

Both ultrasound-estimated epidural depth and MRI-derived epidural depth have a strong correlation with the epidural depth measured from the surgical site. Preprocedural MRI-derived estimates of epidural depth are slightly deeper than the epidural depth measured from the surgical site, and the ultrasound estimated epidural depths are somewhat shallower. Although both radiologic imaging techniques provided reliable preprocedural estimates of the actual epidural depth, the loss of resistance technique cannot be discarded while inserting epidural needles.


Epidural,  Anesthesia,  Ultrasound,  Magnetic resonance imaging,  Intraoperative


Justificativa e objetivos
Avaliar a concordância entre a profundidade peridural medida no campo cirúrgico com a profundidade peridural estimada pela Ressonância Magnética (RM) e ultrassonografia.

Cinquenta pacientes de ambos os sexos, agendados para cirurgia de disco lombar L4‒5 sob anestesia geral, foram incluídos neste estudo observacional prospectivo, e os resultados de 49 pacientes foram analisados. A profundidade peridural real foi medida no campo cirúrgico com uma régua cirúrgica estéril. A profundidade peridural obtida pela Ressonância Magnética (RM) foi medida a partir das imagens do exame de RM. A profundidade peridural estimada pelo ultrassom foi medida a partir da imagem do ultrassom obtida imediatamente antes da cirurgia.

A profundidade peridural média medida no campo cirúrgico foi de 53,80 ± 7,67 mm; a profundidade peridural média da RM foi de 54,06 ± 7,36 mm; e a profundidade peridural estimada por ultrassom foi de 53,77 ± 7,94 mm. A correlação entre a profundidade peridural medida no campo cirúrgico e a profundidade peridural derivada da RM foi de 0,989 (r2 = 0,979; p < 0,001); e a correlação correspondente com a profundidade peridural estimada por ultrassom foi de 0,990 (r2 = 0,980; p < 0,001).

Tanto a profundidade peridural estimada por ultrassom quanto à profundidade peridural derivada da RM mostram forte correlação com a profundidade peridural medida no campo cirúrgico. As estimativas pré-operatórias da profundidade peridural derivadas da RM são um pouco mais profundas do que a profundidade peridural medida no campo cirúrgico, e as profundidades peridurais estimadas por ultrassom são um pouco mais rasas. Embora ambas as técnicas de imagem radiológica tenham fornecido estimativas pré-operatórias confiáveis ​​da profundidade peridural real, a técnica de perda de resistência não pode ser descartada durante a inserção da agulha peridural.


Peridural,  Anestesia,  Ultrassonografia,  Ressonância magnética Intraoperatória


1. Bomberg H, Paquet N, Huth A, Wagenpfeil S, Kessler P, Wulf H, et al. Epidural needle insertion: a large registry analysis. Anaesthesist. 2018;67:922-30.

2. Popping DM, Elia N, Van Aken HK, Marret E, Schug SA, Kranke P, et al. Impact of epidural analgesia on mortality and morbidity after surgery: systematic review and metaanalysis of randomized controlled trials. Ann Surg. 2014;259:1056-67.

3. Bouman EA, Gramke HF, Wetzel N, Vanderbroeck TH, Bruinsma R, Theunissen M, et alEvaluation of two different epidural catheters in clinical practice. Narrowing down the incidence of paresthesia! Acta Anaesthesiol Belg. 2007;58:101-5.

4. Dalsasso M, Grandis M, Innocente F, Veronese S, Ori C-A survey of 1000 consecutive epidural catheter placements performed by inexperienced anesthesia trainees. Minerva Anestesiol. 2009;75(1-2):13-19.

5. Kang XH, Bao FP, Xiong XX, Li M, Jin TT, Shao J, et al. Major complications of epidural anesthesia: a prospective study of 5083 cases at a single hospital. Acta Anaesthesiol Scand. 2014;58:858-66.

6. Shih CK, Wang FY, Shieh CF, Huang JM, Lu IC, Wu LC, et al. Soft catheters reduce the risk of intravascular cannulation during epidural block ‒ a retrospective analysis of 1,117 cases in a medical center. Kaohsiung J Med Sci. 2012;28:373-6.

7. Tanaka K, Watanabe R, Harada T, Dan K. Extensive application of epidural anesthesia and analgesia in a university hospital: incidence of complications related to technique. Reg Anesth. 1993;18:34-8.

8. Algrain H, Liu A, Singh S, Vu TN, Cohen SP. Cervical epidural depth: correlation between cervical mri measurements of the skin-to-cervical epidural space and the actual needle depth during interlaminar cervical epidural injections. Pain Med. 2018;19:1015-22.

9. Canturk M, Karbancioglu Canturk F, Kocaoglu N, Hakki M. Abdominal girth has a strong correlation with ultrasound-estimated epidural depth in parturients: a prospective observational study. J Anesth. 2019.

10. Carnie J, Boden J, Gao Smith F. Prediction by computerised tomography of distance from skin to epidural space during thoracic epidural insertion. Anaesthesia. 2002;57:701-4.

11. Franklin AD, Lorinc AN, Shotwell MS, Greene EB, Wushensky CA. Evaluation of the skin to epidural and subarachnoid space distance in young children using magnetic resonance imaging. Reg Anesth Pain Med. 2015;40:245-8.

12. Jones JH, Singh N, Nidecker A, Li CS, Fishman S. Assessing the agreement between radiologic and clinical measurements of lumbar and cervical epidural depths in patients undergoing prone interlaminar epidural steroid injection. Anesth Analg. 2017;124:1678-85.

13. Lee HJ, Min JY, Kim HI, Byon HJ. Measuring the depth of the caudal epidural space to prevent dural sac puncture during caudal block in children. Paediatr Anaesth. 2017;27:540-4.

14. Jordan J, Konstantinou K, O'Dowd J-Herniated lumbar disc. BMJ Clin Evid. 2009;2009.

15. Nelson AM, Nagpal G-Interventional Approaches to Low Back Pain. Clin Spine Surg. 2018;31:188-96.

16. Grau T, Leipold RW, Horter J, Conradi R, Martin EO, Motsch J-Paramedian access to the epidural space: the optimum window for ultrasound imaging. J Clin Anesth. 2001;13:213-17.

17. Crawford SB, Kosinski AS, Lin HM, Williamson JM, Barnhart HX-Computer programs for the concordance correlation coefficient. Comput Methods Programs Biomed. 2007;88:62-74.

18. Lin L, Torbeck LD-Coefficient of accuracy and concordance correlation coefficient: new statistics for methods comparison. PDA J Pharm Sci Technol. 1998;52:55-9.

19. Bland JM, Altman DG-Statistical methods for assessing agreement between two methods of clinical measurement. Lancet. 1986;1:307-10.

20. Bland JM, Altman DG-Measuring agreement in method comparison studies. Stat Methods Med Res. 1999;8:135-60.

21. Arzola C, Davies S, Rofaeel A, Carvalho JC-Ultrasound using the transverse approach to the lumbar spine provides reliable landmarks for labor epidurals. Anesth Analg. 2007;104:1188-92, tables of contents.

22. Balki M, Lee Y, Halpern S, Carvalho JC. Ultrasound imaging of the lumbar spine in the transverse plane: the correlation between estimated and actual depth to the epidural space in obese parturients. Anesth Analg. 2009;108:1876-81.

23. Helayel PE, da Conceicao DB, Meurer G, Swarovsky C, de Oliveira Filho GR-Evaluating the depth of the epidural space with the use of ultrasound. Rev Bras Anestesiol. 2010;60:376-82.

24. Daniel M, Doyon D, Bekkali F, Delvalle A, Francke JP-MRI of normal spinal epidural fat. J Radiol. 1992;73:695-8.

25. Aldrete JA, Mushin AU, Zapata JC, Ghaly R-Skin to cervical epidural space distances as read from magnetic resonance imaging films: consideration of the “hump pad”. J Clin Anesth. 1998;10:309-13.

5ee3b7ba0e8825b8513195f6 rba Articles
Links & Downloads

Braz J Anesthesiol

Share this page
Page Sections