Ultrasound-Guided Lumbar Spine Injections

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Chapter 20 Ultrasound-Guided Lumbar Spine Injections

Chapter Overview

Chapter Synopsis: This chapter focuses on the use of ultrasound imaging for guidance during many different types of injection procedures for back pain. The benefits of using ultrasonography include its economy, portability, and safety. Any spinal injection procedure requires an intimate knowledge of the underlying anatomy, and use of ultrasound guidance requires a similar familiarity with the intricacies of sonographic data. Ultrasound needle guidance has recently supplanted some more traditionally used imaging techniques, including computed tomography and fluoroscopy. Future development of the technique may include the use of three-dimensional sonographic imaging. The techniques guided by ultrasonography described in the chapter include injections for lumbar medial branch or facet nerve block, facet joint injections, lumbar periradicular injections, and intramuscular trigger point injections. Practitioners should take advantage of hands-on learning opportunities, and novices should focus on intramuscular injections to develop expertise in ultrasound-guided injection techniques.

Important Points:

Clinical Pearls:

Clinical Pitfalls:


This chapter summarizes today’s knowledge and evidence about ultrasound-guided lumbar spinal injections with a focus on sonoanatomy and clinical practice.

Today low back pain is a big medical and economical challenge not only for the physician and the individual patient but also for the community. Although nonspecific low back pain, in which invasive interventions should be reduced to a minimum if not avoided at all, seems to be the predominant entity, in many cases, specific causes and confined anatomical sources are the reason for pain or have to be ruled out. Traditionally, fluoroscopy or even computed tomography (CT) has been used in these cases as guidance devices, first to increase specificity and second to avoid complications arising from improper needle placement. In the past years, ultrasonography moved into the focus of interest not only in regional anesthesia but also for interventions in pain medicine. Ultrasound-guided injection techniques are interesting alternatives to fluoroscopy- and CT-guided methods. Today, portable ultrasound machines offer high quality together with a relatively moderate price. Advantages include no exposure to ionizing radiation for both the patient and the physician, availability as a bedside method, and use in remote locations such as developing countries because there is no restriction to specially equipped radiological facilities. As opposed to radiography, there is no contraindication for ultrasonography during pregnancy, which is another great advantage, when treatment of severe low back pain is especially challenging and injections are unavoidable.

Lumbar medial branch or facet nerve blocks, facet joint injections, intramuscular trigger point injections, and lumbar periradicular injections have become technically possible with ultrasound guidance or assistance. A concise presentation and validation of the methods follows.

Basic Principles of Ultrasound-Guided Injections

Ultrasound Machines, Transducers, and Knobology

Today a huge variety of ultrasound machines in different sizes from different companies is available. Portable machines have reached quality levels comparable to larger scale gear. For applications in regional anesthesia and pain therapy, high-resolution technology combined with excellent musculoskeletal imaging properties is of great help to the practitioner. Linear broadband transducers with high frequencies up to 15 MHz are preferred when small structures close to the surface have to be targeted. Curved-array broadband probes with lower frequencies around 5 MHz are used for deeper targets. At least one of each of these two basic types of transducers should be available to physicians routinely performing ultrasound-guided interventions in pain management. Fig. 20-1 shows a typical linear probe on the left side of the image and a curved-array probe on the right with a schematic shape of the resulting sonographic images. Please note that the side of the mark on the transducer (arrow) is corresponding to the mark on the image (star). This is important for correct image orientation. Color-flow Doppler ultrasonography helps to identify vessels and is part of the basic machine equipment today. Finally, the operator has to be familiar with basic machine settings such as depth, gain, and focus.

Needles, Techniques, and Sterility

Needle choice depends on both target depth and operator preference. Better visualization is possible with larger diameter needles and shallow insertion angles; however, patient comfort is often associated with the contrary. Good choices are needles with facet tips and diameters between 20 and 25 gauges. Recently, higher reflective ultrasound needles have been developed and are the subject of evaluation at the moment. Image orientation can be short or cross axis (SAX; i.e., transverse plane) or long axis (LAX; i.e., longitudinal plane relative to the target nerve or the spinal column). Needle insertion can be out of plane or in plane relative to the LAX of the transducer’s footprint. Whereas out-of-plane techniques offer shorter access but only visualization of the needle tip, in-plane techniques are associated with a longer path to the target but visualization of the entire needle (Fig. 20-2). The needle insertion point for the out-of-plane technique is close to the longer side; for the in-plane technique, it is close to the shorter side of the transducer’s footprint (Fig. 20-3). Sometimes the transducer has to be turned 90 degrees after needle insertion to ensure proper positioning in a second plane. Sterile working conditions are mandatory for invasive procedures, including covering of the probe and use of sterile ultrasound gel. Special covers designed for this purpose are available today; the image shows how to cover a probe with such a shield (Fig. 20-4).

Sonography of the Lumbar Spine—Basic Scanning Sequence

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