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Ultrasound-guided intervention for pain management “Ultrasound imaging offers many advantages over fluoroscopy and computed tomography…”
Traditionally, fluoroscopy and computed tomography (CT) have been the two common imaging modalities used for interventional pain procedures. A decade ago, ultrasound emerged as a popular choice for pain intervention, as evident by the rapid growth of literature and workshops in this field . Ultrasound imaging offers many advantages over fluoroscopy and CT because of its affordability, portability, absence of radiation, and independence of infrastructure and facilities. It also allows visualization of target structures, soft tissues and real-time guidance for injection . However, ultrasound has it own limitations: an inability to reveal structures beyond the bone window and poor reliability for deep structure imaging. In general, ultrasound for pain interventions can be divided according to the following target structures: peripheral, axial and musculoskeletal . Examples of these interventions will be discussed below. The most notable example for peripheral structure is cervical sympathetic trunk (CST) block . Commonly described as stellate ganglion block, CST block is typically performed with landmark-based
or fluoroscopy-guided techniques. The targets are either the anterior tubercle or transverse process at C6–7 level. There are two reasons why ultrasound has become the technique of choice [1,3]. First, CST is defined by the fascial plane (prevertebral fascia), which ultrasound, not fluoroscopy, can visualize. Second, in older techniques the needle is inserted between the trachea and carotid artery. Recent literature suggested a high prevalence of esophagus and vessels in this region [4,5]. Ultrasound imaging allows the visualization and avoidance of these important structures and enables a ‘lateral’ approach to the CST . Large randomized controlled trials are required to confirm the safety, accuracy and outcome over conventional techniques. Another example is meralgia paresthetica, which is a painful mononeuropathy of the lateral femoral cutaneous nerve. Anesthesiologists are commonly involved in the management of these patients. The success rate of the traditional landmark-based technique is notoriously poor because of the huge anatomical variation of the nerve . Ultrasound allows visualization of the nerve. A comparison
“…many exciting developments are in the pipeline for ultrasound technology.”
Toronto Western Hospital, University of Toronto, Canada, McL 2-405 Toronto Western Hospital, 399 Bathurst Street, Toronto, Ontario, M5T 2S8, Canada *Author for correspondence: Tel.: +1 416 603 5118; Fax: +1 416 603 6494; [email protected]
10.2217/PMT.13.70 © 2014 Future Medicine Ltd
Pain Manage. (2014) 4(1), 13–15
Editorial Peng & Soneji study revealed the success rates of ultrasound versus landmark techniques were 84 and 5%, respectively . Most importantly, in patients with meralgia paresthetica, the nerve is usually enlarged due to postcompression hypertrophy. In a case series of meralgia paresthetica patients with an average BMI of 31 kgm-2, the success rate of u ltrasound-guided injection was 100% .
“…ultrasound allows refinement of some existing techniques.” The standard practice for lumbar medial branch block is fluoroscopy-guided as the target is a bone structure. Ultrasound-guided techniques have been validated and compared with fluoroscopy-guided injection. The accuracy was approximately 90–95% , but the success rate fell to an unacceptable 62% in patients with BMI greater than 30 kgm-2 . Thus, the ultrasound technique should be restricted as an alterative to fluoroscopy in patients with a low BMI. By contrast, ultrasound-guided techniques have shown promising results in cervical medial branch blocks, especially for the third occipital nerve . In contrast to the lumbar region, obesity is less contributory to the cervical region. A recent randomized trial compared ultrasound and fluoroscopy techniques on third occipital nerve injection. Both techniques achieved similar success rate and incidence of vascular puncture . However, the ultrasound-guided technique allowed a shorter performance time and fewer needle passes . Although the average BMI was approximately 26–27 kgm-2 in both groups, it is worth mentioning that two and one patients in the ultrasound and fluoroscopy groups, respectively, exceeded a BMI of 35 kgm-2. The ultrasound technique for medial branch at C3–6 has also been validated and compared with fluoro scopy with high success rates of 85–98% [10,12]. However, this ultrasound-guided technique is of limited use for medial branch injection at C7. The use of the ultrasound-guided injection for musculoskeletal structures is a well-accepted practice and is rapidly growing . Ultrasound scanning allows accurate localization of the target structures and can be used as a diagnostic tool for the detection of abnormalities. Literature supporting the superiority of accuracy with ultrasound-guided technique is robust, irrespective of the experience and confidence factor of the practitioner [2,14,15]. Improvement in accuracy
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of the injection results in a better outcome [2,16]. In addition, it enables some procedures that fluoroscopy or a CT scan cannot, such as phenol injection of neuroma, fenestration or injection of platelet-rich plasma into tendon. In the near future, there will be several key developments in ultrasound for pain medicine. First, similar to the development of ultrasound for regional anesthesia, the first phase of literature was mainly on the development of new ultrasound-guided techniques, the validation of these new techniques, as well as comparative studies with existing standard techniques. The second phase of literature will focus on outcome as well as safety. Guidelines for education and training on ultrasound-guided pain intervention have recently been published . This will stimulate the incorporation of ultrasound into different pain programs and more ultrasound related research is likely to follow. Second, many exciting developments are in the pipeline for ultrasound technology. Currently the quality of target visualization limits the clinical application of ultrasound-guided interventions for axial structures. However, newer techniques such as fusion scan (combining CT or MRI pictures with ultrasound images), target-directing system or so-called Global Positioning System (GPS), and real-time 3D scan can potentially enhance the accuracy and reliability of ultrasound-guided spine injections . High-intensity, focused ultrasound is already used in tumor ablation and in some noninvasive surgeries. Recently, it has been explored for nerve ablation and can potentially be used as a noninvasive technique for neural destruction or deactivation . Third, ultrasound allows refinement of some existing techniques. Traditionally, chemical neurolysis has been performed by injecting blindly (without the visualization of nerve) around the nerve. With the use of ultrasound, it is possible to perform neurolysis by injecting a very small amount of neurolytic agent inside the nerve or neuroma. Morton’s neuroma is one example . With the ability to visualize the target structures, it allows precise injection inside the target structures, such as placement of platelet-rich plasma within the tendon of the common extensor origin in tennis elbow. Furthermore, it allows a nonsurgical method to remove calcium from a calcific tendon. In summary, the application of ultrasound for pain intervention has emerged as a popular
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Ultrasound-guided intervention for pain management technique in the last 10 years because of its many advantages over traditional methods. In the near future, more exciting developments will come in view of the growing interest, better ultrasound technology and evolving concepts of intervention, secondary to better visualization of target structures. Is ultrasound for chronic pain intervention a new era? It is just the beginning.
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Bhatia A, Flamer D, Peng P. Evaluation of sonoanatomy relevant to the performance and safety in stellate ganglion block in 100 subjects. Can. J. Anesth. 59, 1040–1047 (2012). Hui GKM, Peng PWH. Meralgia paresthetica – what an anesthesiologist needs to know. Reg. Anesth. Pain Medicine. 36, 156–161 (2011). Hurdle MF, Weingarten TN, Crisostomo RA et al. Ultrasound-guided blockade of the
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P Peng has received equipment support from Sonosite Canada. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. No writing assistance was utilized in the production of this manuscript. 14
Peng P, Narouze S. Ultrasound-guided interventional procedures in pain medicine: a review of anatomy, sonoanatomy and procedures. Part I: non-axial structures. Reg. Anesth. Pain Med. 34, 458–474 (2009).
Siegenthaler A, Mlekusch S, Schliessbach J, Curatolo M, Eichenberger U. Ultrasound imaging to estimate risk of esophageal and vascular puncture after conventional stellate ganglion block. Reg. Anesth. Pain Med. 37, 224–227 (2012).
Financial & competing interests disclosure
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