Randomized Placebo-Controlled Trial of 60-Day Percutaneous Peripheral Nerve Stimulation Treatment Indicates Relief of Persistent Postoperative Pain, and Improved Function After Knee Replacement.

OBJECTIVES: Total knee arthroplasty (TKA) is an effective surgery for end-stage knee osteoarthritis, but chronic postoperative pain and reduced function affect up to 20% of patients who undergo such surgery. There are limited treatment options, but percutaneous peripheral nerve stimulation (PNS) is a promising nonopioid treatment option for chronic, persistent postoperative pain. The objective of the present study was to evaluate the effect of a 60-day percutaneous PNS treatment in a multicenter, randomized, double-blind, placebo-controlled trial for treating persistent postoperative pain after TKA. MATERIALS AND METHODS: Patients with postoperative pain after knee replacement were screened for this postmarket, institutional review board-approved, prospectively registered (NCT04341948) trial. Subjects were randomized to receive either active PNS or placebo (sham) stimulation. Subjects and a designated evaluator were blinded to group assignments. Subjects in both groups underwent ultrasound-guided placement of percutaneous fine-wire coiled leads targeting the femoral and sciatic nerves on the leg with postoperative pain. Leads were indwelling for eight weeks, and the primary efficacy outcome compared the proportion of subjects in each group reporting ≥50% reduction in average pain relative to baseline during weeks five to eight. Functional outcomes (6-minute walk test; 6MWT and Western Ontario and McMaster Universities Osteoarthritis Index) and quality of life (Patient Global Impression of Change) also were evaluated at end of treatment (EOT). RESULTS: A greater proportion of subjects in the PNS groups (60%; 12/20) than in the placebo (sham) group (24%; 5/21) responded with ≥50% pain relief relative to baseline (p = 0.028) during the primary endpoint (weeks 5-8). Subjects in the PNS group also walked a significantly greater distance at EOT than did those in the placebo (sham) group (6MWT; +47% vs -9% change from baseline; p = 0.048, n = 18 vs n = 20 completed the test, respectively). Prospective follow-up to 12 months is ongoing. CONCLUSIONS: This study provides evidence that percutaneous PNS decreases persistent pain, which leads to improved functional outcomes after TKA at EOT.

Water-circulating probes significantly modify lesion length and axon damage in cooled radiofrequency ablations when compared with similar-sized standard radiofrequency probes in rats.

INTRODUCTION: Preclinical research demonstrated water-cooled radiofrequency (CRF) ablations have a significant impact on structural and functional changes compared to standard radiofrequency (SRF) ablations. Clinical procedures utilizing RF to treat chronic pain conditions also show sustained functional outcomes. We hypothesize that the design of the RF probes plays an important role in interventional procedure success, but it remains unclear which specific design features. METHODS: RF ablations were performed in male Lewis rats (n=51) using multiple-sized probes for CRF (17 Ga/2 mm and 17Ga/4 mm) and SRF (22Ga/5 mm, 18Ga/10 mm and 16Ga/10 mm) to evaluate generator energy output, lesion length, axon damage by histology and nerve function analysis via electromyography. To exclude probe design variables beyond size and remain objective, we tested cooled probes with and without water circulation, which resulted in the CRF probe performing like an SRF probe. RESULTS: Consistent with our previous findings in smaller probes, CRF large probes delivered more energy (p<0.01) and generated multiple zones of thermal damage in sciatic nerves. When the water-circulating feature was turned off, however, energy output (p<0.001) and lesion length (p<0.05) was significantly reduced. CRF probes with the water circulation also featured significantly more axonal disruption, than larger sized SRF probes (p<0.0001). CONCLUSIONS: Overall, this data confirms that CRF's water-circulating technology has a greater impact on energy deposition, lesion length and axon damage compared with SRF ablations. Moreover, results suggest that the structural differences between RF modalities cannot be solely attributed to probe size, and it may shed light on its differences in clinical outcomes.

Infusion Therapy in the Treatment of Neuropathic Pain.

PURPOSE OF REVIEW: Neuropathic pain is a prevalent and burdensome condition. While oral medical therapies are the first-line treatment for refractory neuropathic pain, in some cases, infusion therapy may be employed. This article is a systematic review of recent publications regarding epidemiologic, pathophysiologic, diagnostic, and therapeutic advancements in the treatment of neuropathic pain using intravenous infusion therapy. Special consideration will be given to relevant and practically used agents and available information on outcomes. RECENT FINDINGS: Individuals with neuropathic pain from various etiologies (e.g. trigeminal neuralgia, post-herpetic neuralgia, diabetic neuropathy) often find short-term relief from infusion therapies. However, it is difficult to generalize the findings of these studies to form a standard treatment regimen. The purpose of this paper is to provide clinicians an up-to-date summary of recent literature regarding several infusion therapies in treating neuropathic pain.

Peripheral Joint Radiofrequency Ablation.

This article provides a detailed description of peripheral joint radiofrequency ablation and its contemporary use in the treatment of chronic knee, hip, and shoulder pain. Special attention is given to anatomy and innervation of the joints discussed, technical approach, selection criteria, contraindications, and patient outcomes.

Cooled Radiofrequency Ablation of the Trochanteric Branch of the Nervus Femoralis to Treat Greater Trochanteric Pain Syndrome.

OBJECTIVE: Greater trochanteric pain syndrome is a common cause of lateral hip pain. Corticosteroid injections are commonly utilized as nonsurgical interventions; however, they are not effective for all patients. This technical case report describes a method for treating greater trochanteric pain syndrome by utilizing cooled radiofrequency ablation. METHODS: The trochanteric branch of the nervus femoralis is identified as providing sensory innervation to the greater trochanter and its surrounding structures. We have identified fluoroscopic targets to block the nerve and perform cooled radiofrequency ablation. We present two patient cases which demonstrated significant pain relief of greater trochanteric pain syndrome with this treatment. CONCLUSIONS: Cooled radiofrequency ablation of the trochanteric branch of the nervus femoralis is a potential treatment for greater trochanteric pain syndrome. This procedure provides a potential steroid-sparing interventional treatment based on reproducible fluoroscopic landmarks.

HIV Neuropathy-a Review of Mechanisms, Diagnosis, and Treatment of Pain.

PURPOSE OF REVIEW: This article is a systematic review of data from 2018 to 2020 regarding information from publications on epidemiologic, diagnostic, and therapeutic advancements in human immunodeficiency virus-associated peripheral neuropathy. RECENT FINDINGS: The epidemiology/pathology of HIV neuropathy is discussed. Diagnostics includes skin wrinkling-eutectic mixture of local anesthetic test and neurologic examinations. Therapeutic interventions include pharmacologic and nonpharmacologic management as well as self-management strategies. Peripheral neuropathy continues to affect the lives of persons living with HIV. First-line treatment with pregabalin or gabapentin for HIV neuropathic pain has limited data on adequate response. Exercise and self-management strategies may provide benefit in pain reduction. Continuing research on risk factors and biomarkers for HIV-related peripheral neuropathy will be critical for future diagnostic and therapeutic agents.

Putting Our Shoulder to the Wheel: Current Understanding and Gaps in Nerve Ablation for Chronic Shoulder Pain.

Shoulder pain is prevalent, burdensome, and functionally limiting, with diverse pathology and associated treatments. This narrative review provides a summary of relevant neuroanatomy, proposed ablation targets, safety and efficacy concerns for ablation targets, and current research gaps. Radiofrequency ablation (RFA) of peripheral sensory nerves is a well-established treatment for chronic joint and spine pain, but it is relatively nascent for shoulder pain. Cadaveric studies demonstrate the shoulder joint is innervated by articular branches of the suprascapular nerve, axillary nerve, lateral pectoral nerve, and upper and lower subscapular nerves. Shoulder articular branch RFA appears to be a safe and effective treatment for chronic shoulder pain, but there are currently no widely accepted protocols for ablation targets. There are also no randomized controlled trials (RCT) assessing safety and efficacy of proposed targets or the prognostic value of articular blocks. Future research studies should prioritize categorical data, use appropriate functional measures as primary endpoints, and would ideally include a large-scale RCT.

Innervation of the Posterior Hip Capsule: A Cadaveric Study.

OBJECTIVE: Recent studies of hip anatomy have turned to the posterior hip capsule to better understand the anatomic location of the posterior capsular sensory branches and identify nerves with potential for neural blockade. Current literature has shown the posterior hip capsule is primarily supplied by branches from the sciatic nerve, nerve to quadratus femoris, and superior gluteal nerve (1, 2). This cadaveric study investigated the gross anatomy of the posterior hip, while also identifying potential targets for hip analgesia, with emphasis on the superior gluteal nerve and nerve to quadratus femoris. DESIGN: Cadaveric study. SETTING: UT Health San Antonio Anatomy Lab. METHODS: In total, 10 total cadavers (18 hips total), were posteriorly dissected identifying nerve to quadratus femoris, superior gluteal nerve, and sciatic nerve. Nerves were labeled with radio-opaque markers. Following the dissections, fluoroscopic images were obtained at sequential angles to identify neural anatomy and help expand anatomic knowledge for interventional pain procedures. RESULTS: The posterior hip capsule was supplied by the sciatic nerve in 1/16 hips, the nerve to quadratus femoris in 15/18 hips, and the superior gluteal nerve in 6/18 hips. CONCLUSIONS: The nerve to quadratus femoris reliably innervates the posterior hip joint. Both the sciatic nerve and superior gluteal nerve have small articular branches that may be involved in posterior hip innervation, but this is not seen commonly. The results of this study may elucidate novel therapeutic targets for treatment of chronic refractory hip pain (i.e., the nerve to quadratus femoris).

Fluoroscopically guided mandibular nerve block: a modified lateral approach.

BACKGROUND AND OBJECTIVES: Mandibular nerve blocks are indicated for atypical face pain and trigeminal neuralgia. We hypothesized that a modified lateral approach, which entailed a combination of lateral and anterior approach techniques to the mandibular nerve block would lead to similar efficacy and improved safety profile rather than the typical lateral or anterior techniques. METHODS: This alternative approach was derived from anatomical investigation using the Radiology Anatomy Atlas Viewer and reconstructed axial cadaveric slices. We used axial slices at the level of the lateral pterygoid plate, and at the level of the temporomandibular joint to devise a needle path appropriate for this block. RESULTS: The modified lateral approach to the mandibular nerve block was verified theoretically through cadaveric reconstructed slices and has been successfully performed in our practice. Precise needle trajectory could avoid both periosteal contact and gross redirection, as well as other procedural complications. CONCLUSION: The modified lateral approach to a mandibular nerve block avoids the respective risks associated with either the lateral and anterior approach. Facial intervention techniques typically pose increased safety challenges, however through cadaveric anatomic reconstruction, we have developed a safer approach for mandibular nerve blockade.

Thermal Radiofrequency Ablation of the Articular Branch of the Lateral Pectoral Nerve: A Case Report and Novel Technique.

The lateral pectoral nerve (LPN) innervates anterior shoulder structures. We report a novel technique for radiofrequency ablation (RFA) of the articular branch of the LPN (abLPN) to treat persistent anterior shoulder pain. Ultrasound and fluoroscopy were used to identify bony and vascular landmarks to target the midlateral and superior-lateral coracoid process (CP). Multiple thermal RFA lesions were delivered along this location without complication using a 20-gauge cannula. As a result, the patient has continued substantial relief of resting and dynamic deep anterior shoulder pain beyond 3 months. Ablation of the abLPN may provide anterior shoulder analgesia without causing motor weakness.

Quantitative analysis of the distal, lateral, and posterior articular branches of the axillary nerve to the shoulder: implications for intervention.

INTRODUCTION: The terminal sensory branches innervating the shoulder joint are potential therapeutic targets for the treatment of shoulder pain. This cadaveric study investigated in detail the anatomic pathway of the posterior terminal sensory branch of the axillary nerve (AN) and its relationship to nearby anatomic structures for applications, such as nerve block or ablation of the shoulder joint. METHODS: For this study, nine shoulders were dissected. Following dissection, methylene blue was used to stain the pathway of the terminal sensory branches of the AN to provide a visual relationship to the nearby bony structures. A transparent grid was overlaid on the humeral head to provide further detailed information regarding the innervation to the shoulder joint. RESULTS: Eight of the nine shoulders displayed terminal sensory branches of the AN. The terminal sensory branches of the AN innervated the posterolateral head of the humerus and shoulder capsule and were deep and distal to the motor branches innervating the deltoid muscle and teres minor muscle. All terminal branches dissected innervated the shoulder capsule at the posteroinferior-lateral aspect of the greater tuberosity of the humerus. All specimens displayed innervation to the shoulder joint in the lateral most 25% and inferior most 37.5% before methylene blue staining. CONCLUSION: The terminal sensory branches of the AN consistently innervate the inferior and lateral aspects of the posterior humeral head and shoulder capsule. These nerves are easily accessible and would provide a practical target for nerve block or ablation to relieve shoulder pain without compromising motor integrity.

Evidence-based pain medicine for primary care physicians.

The last several decades have seen a marked increase in both the recognition and treatment of chronic pain. Unfortunately, patients frequently misunderstand both the nature of pain and the best practices for its treatment. Because primary care physicians treat the majority of chronic pain, they are ideally situated to provide evidence-based pain care. The majority of the medical evidence supports a biopsychosocial model of pain that integrates physical, emotional, social, and cultural variables. The goal of this primer is to assist primary care physicians in their understanding of pain, evaluation of the chronic pain patient, and ability to direct evidence-based care. This article will discuss the role of physical rehabilitation, pain psychology, pharmacotherapy, and procedural interventions in the treatment of chronic pain. Given the current epidemic of drug-related deaths, particular emphasis is placed on the alternatives to opioid therapy. Unfortunately, death is not the only significant complication from opioid therapy, and this article discusses many of the most common side effects. This article provides general guidelines on the most appropriate utilization of opioids with emphasis on the recent Centers for Disease Control and Prevention guidelines, risk stratification, and patient monitoring. Finally, the article concludes with the critical role that a pain medicine specialist can play in the management of patients with chronic pain.

Cadaveric Study of the Articular Branches of the Shoulder Joint.

BACKGROUND AND OBJECTIVES: This cadaveric study investigated the anatomic relationships of the articular branches of the suprascapular (SN), axillary (AN), and lateral pectoral nerves (LPN), which are potential targets for shoulder analgesia. METHODS: Sixteen embalmed cadavers and 1 unembalmed cadaver, including 33 shoulders total, were dissected. Following dissections, fluoroscopic images were taken to propose an anatomical landmark to be used in shoulder articular branch blockade. RESULTS: Thirty-three shoulders from 17 total cadavers were studied. In a series of 16 shoulders, 16 (100%) of 16 had an intact SN branch innervating the posterior head of the humerus and shoulder capsule. Suprascapular sensory branches coursed laterally from the spinoglenoid notch then toward the glenohumeral joint capsule posteriorly. Axillary nerve articular branches innervated the posterolateral head of the humerus and shoulder capsule in the same 16 (100%) of 16 shoulders. The AN gave branches ascending circumferentially from the quadrangular space to the posterolateral humerus, deep to the deltoid, and inserting at the inferior portion of the posterior joint capsule. In 4 previously dissected and 17 distinct shoulders, intact LPNs could be identified in 14 (67%) of 21 specimens. Of these, 12 (86%) of 14 had articular branches innervating the anterior shoulder joint, and 14 (100%) of 14 LPN articular branches were adjacent to acromial branches of the thoracoacromial blood vessels over the superior aspect of the coracoid process. CONCLUSIONS: Articular branches from the SN, AN, and LPN were identified. Articular branches of the SN and AN insert into the capsule overlying the glenohumeral joint posteriorly. Articular branches of the LPN exist and innervate a portion of the anterior shoulder joint.

A Novel Use of Regional Anesthesia for Spastic Hemiplegia Evaluation and Treatment: A Case Report.

Spastic hemiplegia is a common sequela of stroke. Spasticity that is not optimally reduced with systemic therapy is often treated with intramuscular botulinum toxin injections. Spastic tone can increase the difficulty of appropriately positioning the patient for botulinum toxin injections, lengthen procedure duration, and increase periprocedural pain. Our patient, a 53-year-old woman, was unable to be adequately positioned to receive botulinum toxin injections to her left upper extremity because of challenging flexion synergy posturing and related positional pain. A left interscalene brachial plexus local anesthetic block administered under ultrasound guidance was used to produce both temporary dense muscle relaxation and profound anesthesia, facilitating successful and comfortable botulinum toxin injections in this patient.

Radiofrequency ablation near the bone-muscle interface alters soft tissue lesion dimensions.

BACKGROUND AND OBJECTIVES: Radiofrequency (RF) lesions are safe and effective in the treatment of spine pain; however, models developed to study factors affecting lesion dimensions have been performed in homogeneous media that may not accurately simulate human anatomy and electrophysiology. We present a novel ex vivo porcine model for performing RF lesion studies and report the influence of bone on projection of RF ablation lesions into soft tissue. METHODS: Radiofrequency lesions were performed in porcine rib specimens using monopolar 18-gauge, 10-mm straight active tip cannula, with a lesion temperature of 80°C for 150 seconds. Ten lesions were performed in pure porcine muscle tissue and abutting porcine rib bone with surrounding muscle. Lesions were exposed with dissection and measured with digital calipers. RESULTS: Maximal effective lesion radius approximately doubled against the bone compared with the pure muscle group (mean, 5.65 mm [95% CI, 5.43-5.87 mm] vs 2.68 mm [95% CI, 2.55-2.81 mm], P < .0001), although this was seen only in a vertical direction and not horizontally. In addition, the prelesion and postlesion impedance of the bone-muscle interface was consistently higher than the muscle-only interface (mean, 165.6 Ohm [95% CI, 146.6-184.6 Ohm] vs 137.8 Ohm [95% CI, 135.5-140.1 Ohm], P = 0.004; 144.3 Ohm [95% CI, 134.3-154.3 Ohm] vs 124.3 Ohm [95% CI, 119.3-129.3 Ohm], P = 0.001). Other dimensions and estimated volume were not significantly different. CONCLUSIONS: Bone adjacent to RF lesions alters the surrounding electrophysiological environment causing RF lesions to project further perpendicularly from the needle axis, vertically to bone, than previously expected. This phenomenon should be considered in the future modeling and clinical practice of RF.