Jul 11, 2018, 12:25 PM by Ashutosh Joshi, MBBS, MD, DNB, FCAI, EDRA, and Anuj Bhatia, MBBS, MD, FRCA, FRCPC

Ultrasonography (US) has unique benefits over anatomic landmarks (ALs) and fluoroscopy (FL), including lack of ionizing radiation, visualization of soft tissues and vascular structures, and portability. International publications on US-guided neuraxial, peripheral nerve, and joint-related procedures to relieve pain indicate an expanding role for this imaging modality. The objective of this review is to discuss important publications in the past 5 years on the use of US in interventional pain medicine.

Neuraxial Procedures

Cervical Spine. Two studies by a group of Canadian and Thai researchers reported that US-guided C5 and C6 medial branch block (MBB) needle placement was accurate in 100% and 97.5% of procedures, respectively (as verified by FL), and vascular penetration was avoided in 30% of procedures.^[1] The authors also reported that US-guided C7 MBB required less time to perform, used fewer needle passes than the FL-guided technique, and avoided vascular penetration in 40% of patients without compromising success rates, postblock analgesia, or complication rates.^[2] Reduced procedural discomfort, fewer attempts, and faster procedure times for CMBB with US as compared to fluoroscopy were also reported by Korean investigators, with similar success and complication rates in the two groups.^[3] Finally, use of US allowed identification of critical vessels around the cervical nerve roots while providing similar analgesic benefit as FL-guided injections, as evident in two recent studies from Korea.^[4-5]

“Current evidence is stronger for using ultrasonography to guide injections into joints and around peripheral nerves as compared to neuraxial procedures.”

Lumbar Spine. In a trial by Korean investigators, US-guided lumbar intraarticular injections had similar analgesic and functional outcomes as compared to FL-guided injections,^[6] but the mean body mass index (BMI) of the participants was under 25 kg/m2 . Cadaveric studies on US-guided lumbar facet joint and lumbar transforaminal epidural injections from the United States have reported 88% and 91.3% accuracy, respectively, as verified by FL.^[7-8] However, targets could not be visualized with US at the foramen between the fifth lumbar and sacral vertebrae in 8% of the procedures because of prominent iliac crests.^[8] In another trial from Taiwan, shorter performance time for US-guided lumbar nerve root block and similar analgesic efficacy in comparison to FL-guided injections were reported, but participants' mean BMI was less than 25 kg/m2 . ^[9] A Korean retrospective study on 146 patients who received USor FL-guided lumbar MBB reported shorter procedure time with US while conferring similar analgesic benefits.^[10] A limitation of US-guided MBB is that access to the fifth lumbar dorsal ramus is often challenging because of prominent iliac crests. A group of researchers from Austria, Canada, Switzerland, and Italy performed a cadaveric study to develop a US-guided, out-of-plane technique for this procedure with a success rate of 80%.^[11]

Sacroiliac Joint (SIJ). US-and FL-guided SIJ intra-articular injections were associated with similar analgesic benefits, functional improvement, and patient satisfaction in two studies from Korea and Canada.^[12-13] The authors also reported enhanced safety with US because blood vessels around the SIJ could be avoided. However, the US-guided approach had slightly lower accuracy^[12-13] and required more time^[13] for performing SIJ injections when compared to FL. US-guided lateral sacral branch blocks were associated with a shorter performance time, fewer needle passes, and a lower incidence of vascular breach than FL-guided technique with similar analgesic outcomes in both groups in a Canadian study. Interestingly, the interventionists' level of experience significantly affected performance time with US but not with FL.^[14]

Peripheral Joint Procedures

Lower-Limb Joints. A recent Spanish study reported similar accuracy for US- and FL-guided injections into the hip joint.^[15] Furthermore, investigators from United States found that US-guided injections of the hip were less painful than FL-guided injections and patients who had undergone procedures with those modalities preferred US over FL.^[16] We identified one systematic review and two studies from China, Iran, and Korea, respectively, that reported higher accuracy rates (validation with FL) and more analgesic benefit with US-guided knee injections.^[17-19] A study by French investigators reported greater efficacy and patient satisfaction with imaging guidance (US or FL) for ankle (tibiotalar) joint injections than with ALs (84% and 66%, respectively). However, no differences were observed between US or FL groups in terms of efficacy or satisfaction.^[20]

Upper-Limb Joints. US-guided glenohumeral (GH) joint injections were found to be more accurate and to yield better analgesic and functional benefits than AL-guided approach in two studies from Iran and the United States.^[21-22] A study from Hong Kong and a meta-analysis reported similar accuracy for US- and FL-guided injections in the GH joint.[23,24] Use of US significantly improved the accuracy of intra-articular acromioclavicular joint, elbow joint, and distal radioulnar joint injections when compared to AL technique in studies from Switzerland and Korea.^[25–27]

Peripheral Nerve Procedures

A team of investigators from Austria, Germany, and Switzerland reported that US can be used to identify and block the greater occipital nerve in cadavers either at the level of the C2 transverse process or the occiput with a higher success rate at the C2 level (100% vs 86%).^[28] Two studies from the United States and Canada also showed that vascular and esophageal penetration are potential risks that can be prevented by using US to guide cervical sympathetic blocks.^[29,30] US-guided ilioinguinal and iliohypogastric nerve blocks were shown to be as effective as AL-guided blocks for the treatment of chronic postherniorrhaphy pain by a team from the United States.^[31] However, inaccurate placement of injectate has been reported in AL-guided nerve blocks.^[32] A team from Austria suggested an alternative technique to block the suprascapular nerve near its origin from the upper trunk of the brachial plexus with 81% visualization as compared to 36% in traditional suprascapular site.^[33] In another study, use of US conferred higher accuracy and lower injectate volumes than ALs as a guidance method for intercostal nerve injections in cadaveric study from Canada and the United States.^[34] A Canadian study on cadavers and volunteers that compared AL- and US-guided needle placement and identification of the lateral femoral cutaneous nerve, respectively, showed a huge improvement in accuracy with US (5.3% and 84.2%, respectively).^[35] However, another Canadian study found that US- and FL-guided pudendal nerve blocks were similar in accuracy and visualization of surrounding structures like vessels and nerves, but the procedural time was longer with US (428 vs 219 seconds).^[36]

Conclusions

Despite its potential to enhance accuracy, efficacy, and safety, a paucity of high-quality trials to confirm advantages of US over traditional modalities and a perception that experience of the interventionalist impacts procedural performance with US guidance are significant barriers to widespread use of US for interventional pain. Furthermore, cadaveric studies that demonstrate the potential of US in increasing accuracy of interventional procedures need to be replicated in patients. Current evidence is stronger for using ultrasonography to guide injections into joints and around peripheral nerves as compared to neuraxial procedures. Studies that combine use of ultrasonography (for identifying and avoiding vessels and other structures) and fluoroscopy (for simultaneous visualization of multiple spinal levels) may improve outcomes of neuraxial procedures.

References

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