Ann Rehabil Med.  2018 Dec;42(6):814-821. 10.5535/arm.2018.42.6.814.

Needle Entry Angle to Prevent Carotid Sheath Injury for Fluoroscopy-Guided Cervical Transforaminal Epidural Steroid Injection

  • 1Department of Rehabilitation Medicine, CHA Bundang Medical Center, CHA University School of Medicine, Seongnam, Korea.
  • 2Department of Radiology, CHA Bundang Medical Center, CHA University School of Medicine, Seongnam, Korea.


To suggest rotation angles of fluoroscopy that can bypass the carotid sheath according to vertebral levels for cervical transforaminal epidural steroid injection (TFESI).
Patients who underwent cervical spine magnetic resonance imaging (MRI) from January 2009 to October 2017 were analyzed. In axial sections of cervical spine MRI, three angles to the vertical line (α, angle not to insult carotid sheath; β, angle for the conventional TFESI; γ, angle not to penetrate carotid artery) were measured.
Alpha (α) angles tended to increase for upper cervical levels (53.3° in C6-7, 65.2° in C5-6, 75.3° in C4-5, 82.3° in C3-4). Beta (β) angles for conventional TFESI showed a constant value of 45° to 47° (47.5° in C6-7, 47.4° in C5-6, 45.7° in C4-5, 45.0° in C3-4). Gamma (γ) angles increased at higher cervical levels as did α angles (25.2° in C6-7, 33.6° in C5-6, 43.0° in C4-5, 56.2° in C3-4).
The risk of causing injury by penetrating major vessels in the carotid sheath tends to increase at upper cervical levels. Therefore, prior to cervical TFESI, measuring the angle is necessary to avoid carotid vessels in the axial section of CT or MRI, thus contributing to a safer procedure.


Injections; Epidural; Fluoroscopy; Vascular system injuries; Jugular veins; Carotid arteries

MeSH Terms

Carotid Arteries
Jugular Veins
Magnetic Resonance Imaging
Vascular System Injuries


  • Fig. 1. Measurement of needle entry angle (vertical line). CA, carotid artery; IJV, internal jugular vein; VA, vertebral artery; 1st line, needle entry line to avoid carotid sheath (α angle); 2nd line, needle entry line along the posterior wall in the neural foramen (β angle); 3rd line, needle entry line to avoid carotid artery in the sheath (γ angle).

  • Fig. 2. Measured values of α, β, and γ angles. α angle, needle entry angle to avoid carotid sheath from the vertical line; β angle, needle entry angle to conventional TFESI approach from the vertical line; γ angle, needle entry angle to avoid carotid artery from the vertical line; AVR, average; STD, standard deviation; CI, confidence interval; TFESI, transforaminal epidural steroid injection.

  • Fig. 3. Magnetic resonance images of α, β, and γ angles at each level. (A) C3-4, (B) C4-5, (C) C5-6, and (D) C6-7 levels. α line, α angle to avoid carotid sheath; β line, β angle for conventional TFESI approach; γ line, γ angle to avoid carotid artery; red dashed line, carotid sheath including carotid artery and internal jugular vein; TFESI, transforaminal epidural steroid injection.

  • Fig. 4. Schematic illustrations of internal jugular vein, carotid artery, and lordotic cervical curvature. Dashed lines indicate external, internal, common carotid artery, and internal jugular vein. Consecutive squares are arrangement of schematic cervical vertebrae.


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