Needle Anatomy

To understand spinal needle manipulation, the interventionalist needs to be completely familiar with the anatomy of a typical spinal needle (Figure 2–1).

Figure 2–1 A Quincke-type spinal needle. The bevel is the opening adjacent to the needle tip where the injectate exits. The notch is the raised line or indentation at the hub end of the needle, and it is in line with the bevel. The notch is used as a marker to orient oneself to the needle’s potential direction or path after it is embedded in tissue.

Because of the angulation of the bevel, the needle moves in the direction of the pointed needle tip, which is away from the bevel (Figure 2–2). Understanding and using the needle’s property of movement away from the bevel is known as bevel control. This concept is useful primarily for sharp tip spinal needles.

Figure 2–2 Bevel control.

Bending the Needle TIP: Enhanced Steerability

An approximately 5- to 10-degree angle is typically placed at the needle’s tip. This angle bends away from the bevel and toward the tip to accentuate bevel control and to improve the user’s ability to “steer” the needle (Figures 2-3, 2-4, and 2-5). This allows for finer directional control. Since the needle does not have to be retracted and redirected as frequently, there may be less tissue damage, procedure time, and pain. An unbent needle will tend to move more directly from the skin to the target’s vicinity. However, a bent needle allows for finer control. When a bent needle is advanced, the needle’s direction may require more frequent adjustments as compared with a straight needle (Figure 2–6). Typically, the bend is most effective in the distal 1/2 to 1 cm closest to the tip. More bend is used when more maneuverability is needed. For example, L5-S1 or cervical discography may require a 30 degree bend, whereas a transforaminal steroid injection may require only 5-10 degrees.

Figures 2–3 A, A needle being slid along a surface with the needle tip down and the bevel up. B, The same needle being slid along a flat surface with the bevel down and the needle tip up. When the needle tip is down, it engages the surface and bends toward the tip and away from the bevel (top right panel). In tissue, the same phenomenon will occur, thus directing the needle toward the needle tip. The use of this property allows one to maintain control of the needle tip direction and to keep it moving away from the bevel (bevel control).

Related posts:

Cervical Spinal Cord Stimulation Thoracic Zygapophysial Joint Intraarticular Injection, Posterior Approach Thoracic Transforaminal Epidural Steroid Injection, Infraneural Approach Cervical Zygapophysial Joint Nerve (Medial Branch) Radiofrequency Neurotomy and Nerve Injection, Posterior Approach Thoracic Interlaminar Epidural Steroid Injection, Paramedian Approach Cervical Discography/Disc Access

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