Needle Techniques

Abstract

Many aspects are involved in a technically successful, efficient, and safe spinal injection procedure. These aspects are discussed in Box 2.1 . This chapter focuses on item 4 from that list: directing or “driving” the needle tip into proper position.

Keywords

bevel control, concavity, multiplanar, needle directing, needle driving, needle technique, safety

Note: Please see pages ii , iii for a list of anatomic terms/abbreviations used throughout this book.

Many aspects are involved in a technically successful, efficient, and safe spinal injection procedure. These aspects are discussed in Box 2.1 . This chapter focuses on item 4 from that list: directing or “driving” the needle tip into proper position.

Box 2.1

Keys to a successful fluoroscopically guided interventional spinal procedure:

1.

Identifying where the target is anatomically located
2.

Respecting the structures that are to be avoided and knowing their locations
3.

Identifying which radiographic views (i.e., the trajectory and safety views) best facilitate a safe and direct pathway to the target while avoiding other structures as appropriate
4.

Successfully directing the needle tip toward the target with the use of multiplanar imaging
5.

Confirming placement with real-time contrast enhancement and multiplanar imaging

Needle Anatomy

To understand spinal needle manipulation, the interventionalist needs to be completely familiar with the anatomy of a typical spinal needle ( Fig. 2.1 ). Quincke needles ( Fig. 2.2 ) were developed in 1891 and have a sharp cutting bevel that is designed to perform dural punctures. They remain widely used today, although only for interventional pain procedures where dural puncture is not the goal. Medication flows out from the needle tip, so the distal tip observed on fluoroscopy can be used as a reference to determine from where the injectate is emanating. Whitacre needles ( Fig. 2.2 ) have a blunt, pencil-point tip and are designed to spread tissues without cutting them, theoretically reducing the incidence and severity of post-dural puncture headache (PDPH). ^∗

∗ Please see page ii for a list of anatomical terms/abbreviations used in this book.

Original Whitacre needles had a small side port so anesthetic slowly flowed. Because the side port is not located at the tip, the needle may penetrate the subarachnoid space, but the anesthetic flows epidurally. Newer versions of Whitacre needles have a larger side port, which is located more distally. Whitacre needles are advocated for obstetric anesthesia because of their lower risk for PDPH. The Sprotte needle ( Fig. 2.2 ) is one variation of the pencil-point design. It may allow for more unilateral flow during spinal anesthesia and may facilitate catheter spread through the side port. Because these modifications are mainly designed for intrathecal use and the goal of most pain procedures is the spread of medication at the direct site of the needle tip, the authors prefer to use Quincke-type needles for all but interlaminar procedures. The bevel may be short or long, with the short bevel theoretically producing less tissue damage. However, short bevels have not been shown to reduce the risk for vascular injury. The Tuohy needle has a long, curved bevel with a sharp distal tip that is often utilized to safely enter the epidural space and facilitate the introduction of catheters. The Tuohy needle has a smooth proximal bevel to reduce the risk for cutting a receding catheter. The hub is often used to assist with catheter steering at the needle tip. The Tuohy and Crawford needles are preferred for interlaminar epidural procedures because of their blunt tips, which allow interventionalists to better feel the ligamentum flavum and loss of resistance. The authors prefer to use Tuohy needles for interlaminar epidural injections with or without catheter use.

Bevel Control

Because of the angulation of the bevel in a Quincke needle, the needle moves in the direction of the pointed needle tip, which is away from the bevel ( Figs. 2.3 and 2.4 ). The notch, at the proximal end of the needle, denotes the side on which the bevel is placed. Understanding and using the needle’s property of movement away from the bevel is known as bevel control. This concept is primarily useful for triangular tipped Quincke-type spinal needles, as opposed to pencil-point needles such as the Whitacre or Sprotte needles. Because of their curved base, the Tuohy needles actually slightly deviate toward the bevel or notch.