Current Waveforms in Spinal Cord Stimulation and Their Impact on the Future of Neuromodulation: A Scoping Review.

BACKGROUND: Neuromodulation is a standard and well-accepted treatment for chronic refractory neuropathic pain. There has been progressive innovation in the field over the last decade, particularly in areas of spinal cord stimulation (SCS) and dorsal root ganglion stimulation. Improved outcomes using proprietary waveforms have become customary in the field, leading to an unprecedented expansion of these products and a plethora of options for the management of pain. Although advances in waveform technology have improved our fundamental understanding of neuromodulation, a scoping review describing new energy platforms and their associated clinical effects and outcomes is needed. The authors submit that understanding electrophysiological neuromodulation may be important for clinical decision-making and programming selection for personalized patient care. OBJECTIVE: This review aims to characterize ways differences in mechanism of action and clinical outcomes of current spinal neuromodulation products may affect contemporary clinical decision-making while outlining a possible path for the future SCS. STUDY DESIGN: The study is a scoping review of the literature about newer generation SCS waveforms. MATERIALS AND METHODS: A literature report was performed on PubMed and chapters to include articles on spine neuromodulation mechanism of action and efficacy. RESULTS: A total of 8469 studies were identified, 75 of which were included for the scoping review after keywords defining recent waveform technology were added. CONCLUSIONS: Clinical data suggest that neuromodulation remains a promising tool in the treatment of chronic pain. The evidence for SCS for treating chronic pain seems compelling; however, more long-term and comparative data are needed for a comparison of waveforms when it comes to the etiology of pain. In addition, an exploration into combination waveform therapy and waveform cycling may be paramount for future clinical studies and the development of new technologies.

Adipose Tissue Impacts Radiofrequency Ablation Lesion Size: Results of an Ex Vivo Poultry Model.

BACKGROUND: Radiofrequency ablation (RFA) is a common treatment in which radiofrequency (RF) is used to heat neural tissue and reduce pain. The impact of adipose content in tissue on the lesion size may impact efficacy, and to date, there is little, if any, data comparing its influence on RFA. OBJECTIVES: We evaluated the influence of adipose tissue on RF lesion size. STUDY DESIGN: Controlled, ex vivo study. SETTING: Academic institution in a procedural setting. METHODS: RF lesions were created using 20-G 10-mm protruding electrode (PE) needles inserted into unbrined chicken breasts and thighs at 21°C. RF current was applied for 90 seconds at 80°C. Chicken breasts were used as the control group and chicken thighs were used as the high adipose variant. Four different groups were examined: 1- Standard 20 g RFA needle, 2- 20 g RFA PE needle, 3- Standard RFA needle with lidocaine 2% injectate, and 4- Standard RFA needle with iohexol 240 mg injectate. There were 12 lesions performed in each group; length, width, and depth were measured. RESULTS: The control group had significantly deeper lesions in all 4 cohorts. Lesions' lengths were smaller in the fat-rich group. The control and PE cohorts showed a significant difference in width between the 2 fat-rich and nonfatty groups. LIMITATIONS: Radiofrequency ablation was performed at room temperature and not heated to physiological temperature. This was an ex vivo study, thus factors of human anatomy and physiology could not be evaluated. CONCLUSIONS: Adipose tissue content was inversely related to lesion size in all samples. This factor should be considered when assessing methods of enhancing lesion size in human models.

Percutaneous Ultrasound-Guided Coracohumeral Ligament Release for Refractory Adhesive Capsulitis: A Prospective, Randomized, Controlled, Crossover Trial Demonstrating One-Year Efficacy.

BACKGROUND: Adhesive capsulitis (AC) is a painful and disabling condition with restricted range of motion (ROM) that affects 2% to 3% of the population and up to 20% of patients with diabetes. AC can be idiopathic, iatrogenic, or secondary to shoulder injuries. Some associated conditions include diabetes mellitus, thyroid disorders, dyslipidemia, stroke, prolonged immobilization, and autoimmune conditions. Management ranges from analgesics to physical therapy, local injections, hydrodilatation, and advanced surgical interventions. This study examines percutaneous coracohumeral ligament (PCHL) sectioning with the hypothesis that interruption would improve pain and ROM in patients with AC refractory to conservative management. OBJECTIVES: To use sonographically guided percutaneous interruption of the CHL for the treatment of refractory AC. STUDY DESIGN: A prospective, randomized, controlled, cross-over trial. SETTING: Academic medical center. METHODS: Patients were identified based on inclusion and exclusion criteria under the supervision of the Principal Investigator. After primary screening, research staff explained the study, risks, and benefits to the patients, and consent was obtained. Patients' pain score and shoulder ROM were assessed before and after the procedure, at one month, and one year. The Oxford Shoulder Scoring (OSS) questionnaire was also completed before the procedure and in the one-year follow-up visit.Forty patients were enrolled with refractory AC. Forty-six shoulders were treated; 6 patients underwent a bilateral procedure. Block 2:1 randomization was performed for the 2 groups (PCHL release [PCHLR] and local anesthetic CHL [LACHL]). The LACHL group received a lidocaine injection at CHL, and the PCHLR group received the CHL using a Tenex® (Tenex Health, Lake Forest, CA) needle. ROM, Numeric Rating Scale (NRS-11), and OSS were evaluated at baseline, immediate postprocedure, and long term. RESULTS: Among 46 shoulders included in the study, 7 were excluded due to lost to follow-up, total shoulder replacement, and shoulder manipulation. Twenty-six were randomized to the PCHLR group and 13 to LACHL group. ROM (external rotation and abduction), pain, NRS-11 score, and OSS score were measured at baseline and long term, confirmed by a nonbiased health care personnel. There was no statistically significant difference in ROM, NRS-11, and OSS between the 2 cohorts at the baseline visit. Nine patients in LACHL group crossed over to the PCHLR arm at one month. Data analysis in the long term revealed durability of the PCHLR group with a statistically significant difference in ROM, NRS-11, and OSS. External rotation improved by double, and abduction improved by almost 30% (P value < .001). NRS-11 decreased from 8 (IQR 8, 9) at baseline to 3 (IQR 2, 7) at long term among those who received PCHLR. The baseline mean OSS in the PCHLR group increased from 7.44 to 31.86 at one-year follow-up and was statistically significant (P value < .001). LIMITATIONS: This study represents a small population of patients with a CHL-related ROM deficit. Patients were not excluded for osteoarthritis or other motion-disabling shoulder conditions. We submit that the strength of the study could have been improved if the physician performing the procedure was blinded and if the patient was blinded as well to minimize operator and patient bias. CONCLUSIONS: We demonstrate that our technique for PCHLR is a safe, effective, and durable procedure that improved ROM, pain, and shoulder function in our patient population when compared to the control. KEY WORDS: Tenex, frozen shoulder, pain, range of motion, function, shoulder, minimally invasive, durable.

Percutaneous Ultrasound-Guided Tenotomy of the Iliotibial Band for Trochanteric Pain Syndrome: A Longitudinal Observational Study With One-Year Durability Results.

BACKGROUND: Upper lateral hip pain is a common complaint in adults and is referred to as greater trochanteric pain syndrome (GTPS) and is more prevalent among older women. This is a debilitating condition that could result in lower physical activity and quality of life, and higher unemployment rate. GTPS is a clinical diagnosis, and many cases improve with conservative medical management (CMM). However, there is still a gap between patients not responding to CMM and those who are not good surgical candidates. Thus, percutaneous ultrasound tenotomy (PUT) may be a valuable treatment option to limit this gap. OBJECTIVES: Demonstration of the one-year pain and functional outcomes, including sit to stand. SETTING: Academic tertiary care medical center. METHODS: Forty-eight consecutive patients with refractory trochanteric pain due to iliotibial band (ITB) tendinopathy. Fifty-six hips were treated; 8 patients underwent bilateral procedures. Electronic medical record review of consecutive patients who underwent ITB TENEX® was performed at Montefiore Medical Center from December 2019 to December 2021. Institutional guidelines recommended TENEX® for greater trochanteric pain refractory to conservative treatment and ultrasound (US) confirmed ITB tendinopathy (hypoechogenicity or thickened tendon > 6 mm). Pain level, as well as sit-to-stand, side-lying, and walking tolerance levels were evaluated at baseline preprocedure visit and one-year visit. Follow-up was performed by independent practitioners and corroborated by chart review. RESULTS: Numeric Rating Scale (NRS-11) improved by 4 points across all patients. Seventy percent of patients endorsed pain relief at one-year visit. Median preprocedure NRS-11 was 9. The reported median NRS-11at one year was 5 (Wilcoxon signed rank NRS-11 demonstrated a Z score of -6.042 with P < 0.001). One-year analysis among all patients revealed 57%, 78%, and 66% improvement in side-lying, sit-to-stand, and walking tolerance levels, respectively. LIMITATIONS: We believe that our results must be confirmed with a randomized control trial with a control arm and more patients included. CONCLUSIONS: PUT of the ITB using the TENEX® tissue remodeling device could be a safe and effective treatment for ITB tendinopathy-associated GTPS.

Contrast Spread After Erector Spinae Plane Block at the Fourth Lumbar Vertebrae: A Cadaveric Study.

INTRODUCTION: In recent years, the erector spinae plane block (ESPB) has seen widespread use to treat acute and chronic pain in the regions of the thoracic spine. While limited data suggest its increasing utilization for pain management distal to the thoracic, abdomen and trunk, the anesthetic spread and analgesic mechanism of ESPB at the level of the lumbar spine has not been fully described or understood. METHODS: This is an observational anatomic cadaveric study to assess the distribution of solution following an ESPB block performed at the fourth lumbar vertebrae (L4) using ultrasound guidance to evaluate the spread of a 20 ml solution consisting of local anesthetic and methylene blue. The study was performed in an anatomy lab in a large academic medical center. Following injection of local anesthetic with contrast dye, cadaveric dissection was performed to better understand the extent of contrast dye and to determine the degree of staining to further predict analgesic potential. We reviewed the findings of other ESPB cadaveric studies currently available for comparison. RESULTS: Following cadaveric dissection in an anatomy lab, the contrast dye was observed in the ESP space, and staining was found most cranially at L2 and extending caudally underneath the sacrum. Evaluating the depth of its spread, we found it to be confined to the posterior compartment of the spine sparing the nerve roots bilaterally, which is consistent with the only other cadaveric study of ESPB performed at L4. CONCLUSION: Our results demonstrate the clinical utility of lumbar ESPB where posterior confinement of local anesthesia is preferred. However, further investigation is needed to determine the efficacy of ESPB in lower extremity analgesia which is predicated on ventral nerve root involvement.

The Effect of Local Anesthetics and Contrast Agents on Radiofrequency Ablation Lesion Size.

BACKGROUND: Radiofrequency ablation (RFA) is a validated treatment option for the treatment of chronic pain in patients with lumbar spondylosis. Lesion size has been suggested to correlate with good clinical outcomes. This has created an abundance of scientific interest in the development of products with larger lesion characteristics. Needle characteristics, energy transfer, and heat rate are known to modify lesion size. Here, we demonstrate that common intraoperative solutions, such as lidocaine, iodine, and gadolinium-based products, can also affect lesion shape. OBJECTIVES: To determine whether lidocaine and contrast agents modify lesion characteristics during the performance of monopolar RFA. STUDY DESIGN: Controlled, ex vivo study using clinically relevant conditions and pre-injections. SETTING: Academic institution in a procedural setting. METHODS: RFA lesion size was compared among six cohorts: 1) lidocaine 1%, 2) lidocaine 2%, 3) iohexol 180, 4) iohexol 240, 5) gadodiamide, and 6) control (no fluid control). Radiofrequency (RF) current was applied for 90 seconds at 80°C via 20-gauge 100-mm standard RFA needles with 10-mm active tips in orgranic chicken breasts without preservative at room temperature (21°C). Twelve lesions were performed for each medication cohort. The length, width, and depth of each lesion were measured. The statistical significance between each medication group and the control group was evaluated by t test. RESULTS: The mean lesion surface area of monopolar RFA without any pre-injection used was 80.8 mm2. The mean surface area of the monopolar RF lesion with a pre-injection of 0.2 mL of 2% lidocaine was 114 mm2, and the mean surface area of the monopolar RF lesion with a pre-injection of 0.2 mL of iohexol 240 was 130.6 mm2. The statistical analysis demonstrated that the control group had significantly smaller lesion sizes than did the groups in which lidocaine 2% and iohexol 240 were used (P<0.01). There were no statistically significant differences among the groups in which lidocaine 1%, iohexol 180, and gadodiamide were used. A notable difference was a 20% longer lesion with iohexol 240 compared with the control group and a 20% wider lesion with lidocaine 2% compared with the control group. LIMITATIONS: In vivo anatomy within a human was not used in this study, nor were the chicken breasts heated to physiological temperature. Randomization of pieces of chicken breast did not occur, and thus intrinsic differences among the chicken breast pieces could play a confounding role. CONCLUSIONS: Lidocaine 2% and iohexol 240, when used as pre-injections in RFAs, were found to be associated with statistically significant increases in lesion surface area. However, RFAs with lidocaine 1%, iohexol 180, or gadodiamide were not found to produce a statistically significant difference in lesion size compared with monopolar RFA without the use of injectate.

Best Practices for Minimally Invasive Lumbar Spinal Stenosis Treatment 2.0 (MIST): Consensus Guidance from the American Society of Pain and Neuroscience (ASPN).

Introduction: Lumbar spinal stenosis (LSS) is a common spinal disease of aging with a growing patient population, paralleling population growth. Minimally invasive treatments are evolving, and the use of these techniques needs guidance to provide the optimal patient safety and efficacy outcomes. Methods: The American Society of Pain and Neuroscience (ASPN) identified an educational need for guidance on the prudent use of the innovative minimally invasive surgical therapies for the treatment of symptomatic LSS. The executive board nominated experts spanning anesthesiology, physiatry, orthopedic surgery, and neurosurgery based on expertise, publications, research, diversity and field of practice. Evidence was reviewed, graded using the United States Preventive Services Task Force (USPSTF) criteria for evidence and recommendation strength and grade, and expert opinion was added to make consensus points for best practice. Results: The world literature in English was searched using Medline, EMBASE, Cochrane CENTRAL, BioMed Central, Web of Science, Google Scholar, PubMed, Current Contents Connect, Scopus, and meeting abstracts to identify and compile the evidence (per section) for LSS-related pain. Search words were selected based upon the section represented. Identified peer-reviewed literature was critiqued using USPSTF criteria and consensus points are presented. Discussion: The algorithm for patient selection in the management of symptomatic spinal stenosis is evolving. Careful consideration of patient selection and anatomic architecture variance is critical for improved outcomes and patient safety. Conclusion: ASPN created a guidance for best practice for minimally invasive surgical treatment of symptomatic spinal stenosis.

MRI and Anatomical Determinants Affecting Neuroforaminal Stenosis Evaluation: A Descriptive Observational Study.

Purpose: Neuroforaminal stenosis (NFS), a narrowing of the intervertebral foramen, is a cause of disability in the aging population. Formal magnetic resonance imaging (MRI) classification of NSF has been developed recently and contradictory findings have been reported. This study aims to assess whether in-plane, anatomically conformed two-dimensional (2D) views of the neuroforamen characterize NFS more accurately than traditional axial, coronal, and sagittal views in healthy individuals with and without simulated scoliosis. Patients and methods: This observational study was approved by the designated institutional review board at our academic tertiary care center. Four volunteers underwent lumbar spine MRI twice, once in the supine position and once with intentionally introduced hip tilt. The latter resulted in lumbar curvature mimicking positioning errors approximating degenerative lumbar scoliosis. Anatomically oriented cuts such as axial with endplate correction and coronally obliqued parasagittals, also called coronal obliques, were performed. Standard sagittal and axial views were also performed in both the supine and rotated groups. Results: Coronal oblique and anatomically oriented axial views demonstrated the highest correlation with true neuroforaminal caliber. Deviation from anatomical congruence resulted in false measurements of neuroforaminal size. The hip-tilt studies produced MR that were less favorable to characterization of the caliber of neuroforamina. Coronal sections demonstrated reliability only when performed at the mid-pedicular lines. Standard axial views were reliable only when taken at the upper one-third of the neuroforamen. Coronal oblique views demonstrated superiority when evaluating consecutive neuroforamen on one image compared to non-obliqued parasagittal slices. Conclusion: To minimize error in neuroforaminal analysis, imaging specialists should perform anatomically oriented cuts to conform to individual patient anatomy. When this cannot be performed due to a patient's spine rotation or position, the MRI reader should view oblique, axial, and coronal images simultaneously and dynamically for proper foraminal characterization.

An Algorithmic Approach to the Physical Exam for the Pain Medicine Practitioner: A Review of the Literature with Multidisciplinary Consensus.

BACKGROUND: Increased utilization of telemedicine has created a need for supplemental pain medicine education, especially for the virtual physical assessment of the pain patient. Traditional clinical training utilizes manual and tactile approaches to the physical examination. Telemedicine limits this approach and thus alternative adaptations are necessary to acquire information needed for sound clinical judgement and development of a treatment plan. Clinical assessment of pain is often challenging given the myriad of underlying etiologies contributing to the sensory experience. The COVID-19 pandemic has led to a dramatic increase in the use of virtual and telemedicine visits, further complicating the ease of assessing patients in pain. The increased reliance on telemedicine visits requires clinicians to develop skills to obtain objective information from afar. While eliciting a comprehensive history and medication assessment are performed in a standard fashion via telemedicine, a virtual targeted physical examination is a new endeavor in our current times. In order to appropriately diagnose and treat patients not directly in front of you, a pivot in education adaptations are necessary. OBJECTIVE: To summarize best care practices in the telemedicine physical exam while presenting an algorithmic approach towards virtual assessment for the pain practitioner. DESIGN: Review of the literature and expert multidisciplinary panel opinion. SETTING: Nationally recognized academic tertiary care centers. SUBJECTS: Multidisciplinary academic experts in pain medicine. METHODS: Expert consensus opinion from the literature review. RESULTS: An algorithm for the virtual physical exam for pain physicians was created using literature review and multidisciplinary expert opinion. CONCLUSIONS: The authors here present simple, comprehensive algorithms for physical exam evaluations for the pain physician stemming from a review of the literature.

The MOTION Study: A Randomized Controlled Trial with Objective Real-World Outcomes for Lumbar Spinal Stenosis Patients Treated with the mild® Procedure: One-Year Results.

OBJECTIVE: The purpose of this study is to provide Level-1 objective, real-world outcome data for patients with lumbar spinal stenosis suffering from neurogenic claudication secondary to hypertrophic ligamentum flavum. DESIGN: The MOTION Study is a prospective, multicenter, randomized controlled trial comparing the mild® Procedure (minimally invasive lumbar decompression; Vertos Medical, Aliso Viejo, CA, USA) as a first-line therapy in combination with nonsurgical conventional medical management (CMM) vs CMM alone as the active control. METHODS: Patients in the test group received the mild Procedure at baseline. Both the mild+CMM group and the control group were allowed unrestricted access to conventional real-world therapies. Patient-reported outcomes included the Oswestry Disability Index, the Zurich Claudication Questionnaire, and the Numeric Pain Rating Scale. A validated Walking Tolerance Test, the incidence of subsequent lumbar spine interventions, and the occurrence of adverse events were used to measure objective outcomes. RESULTS: Sixty-nine patients in each group were analyzed at 1-year follow-up. No device- or procedure-related adverse events were reported in either group. Results from all primary and secondary outcome measures showed statistical significance in favor of mild+CMM. CONCLUSIONS: One-year results of this Level-1 study demonstrated superiority of mild+CMM over CMM alone for patients with lumbar spinal stenosis who were suffering from neurogenic claudication secondary to hypertrophic ligamentum flavum. Use of the validated Walking Tolerance Test to objectively measure increased ability to walk without severe symptoms provided evidence of statistically significantly better outcomes for mild+CMM than for CMM alone. With no reported device or procedure-related adverse events, the long-standing safety profile of the mild Procedure was reaffirmed. mild is a safe, durable, minimally invasive procedure that has been shown to be effective as an early interventional therapy for patients suffering from symptomatic lumbar spinal stenosis.

Telemedicine and current clinical practice trends in the COVID-19 pandemic.

Telemedicine is the medical practice of caring for and treating patients remotely. With the spread of the coronavirus disease-2019 (COVID-19) pandemic, telemedicine has become increasingly prevalent. Although telemedicine was already in practice before the 2020 pandemic, the internet, smartphones, computers, and video-conferencing tools have made telemedicine easily accessible and available to almost everyone. However, there are also new challenges that health care providers may not be prepared for, including treating and diagnosing patients without physical contact. Physician adoption also depends upon reimbursement and education to improve the telemedicine visits. We review current trends involving telemedicine, how pandemics such as COVID-19 affect the remote treatment of patients, and key concepts important to healthcare providers who practice telemedicine.

Telemedicine During COVID-19 and Beyond: A Practical Guide and Best Practices Multidisciplinary Approach for the Orthopedic and Neurologic Pain Physical Examination.

BACKGROUND: The COVID pandemic has impacted almost every aspect of human interaction, causing global changes in financial, health care, and social environments for the foreseeable future. More than 1.3 million of the 4 million cases of COVID-19 confirmed globally as of May 2020 have been identified in the United States, testing the capacity and resilience of our hospitals and health care workers. The impacts of the ongoing pandemic, caused by a novel strain of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), have far-reaching implications for the future of our health care system and how we deliver routine care to patients. The adoption of social distancing during this pandemic has demonstrated efficacy in controlling the spread of this virus and has been the only proven means of infection control thus far. Social distancing has prompted hospital closures and the reduction of all non-COVID clinical visits, causing widespread financial despair to many outpatient centers. However, the need to treat patients for non-COVID problems remains important despite this pandemic, as care must continue to be delivered to patients despite their ability or desire to report to outpatient centers for their general care. Our national health care system has realized this need and has incentivized providers to adopt distance-based care in the form of telemedicine and video medicine visits. Many institutions have since incorporated these into their practices without financial penalty because of Medicare's 1135 waiver, which currently reimburses telemedicine at the same rate as evaluation and management codes (E/M Codes). Although the financial burden has been alleviated by this policy, the practitioner remains accountable for providing proper assessment with this new modality of health care delivery. This is a challenge for most physicians, so our team of national experts has created a reference guide for musculoskeletal and neurologic examination selection to retrofit into the telemedicine experience. OBJECTIVES: To describe and illustrate musculoskeletal and neurologic examination techniques that can be used effectively in telemedicine. STUDY DESIGN: Consensus-based multispecialty guidelines. SETTING: Tertiary care center. METHODS: Literature review of the neck, shoulder, elbow, wrist, hand, lumbar, hip, and knee physical examinations were performed. A multidisciplinary team comprised of physical medicine and rehabilitation, orthopedics, rheumatology, neurology, and anesthesia experts evaluated each examination and provided consensus opinion to select the examinations most appropriate for telemedicine evaluation. The team also provided consensus opinion on how to modify some examinations to incorporate into a nonhealth care office setting. RESULTS: Sixty-nine examinations were selected by the consensus team. Household objects were identified that modified standard and validated examinations, which could facilitate the examinations.The consensus review team did not believe that the modified tests altered the validity of the standardized tests. LIMITATIONS: Examinations selected are not validated for telemedicine. Qualitative and quantitative analyses were not performed. CONCLUSIONS: The physical examination is an essential component for sound clinical judgment and patient care planning. The physical examinations described in this manuscript provide a comprehensive framework for the musculoskeletal and neurologic examination, which has been vetted by a committee of national experts for incorporation into the telemedicine evaluation.

Aggregation properties of triamcinolone acetonide injection in human serum: considerations when performing epidural steroid injections.

BACKGROUND: Morbidity has been reported as a sequelae of crystalline steroid epidural steroid injections (ESIs), and particulate steroid size, aggregation, and embolization in brain and spinal cord may be the mechanism related to these neurologic effects. OBJECTIVE: The objective of the study was to examine the aggregation properties of triamcinolone acetonide in commonly used local anesthetics with and without human serum. SETTING: This study was conducted in an academic tertiary care center. HYPOTHESIS: Triamcinolone acetonide shows different aggregation characteristics in serum compared to a non-physiologic solution. DESIGN: Triamcinolone acetonide was mixed with lidocaine 1% (first group) and bupivacaine 0.5% (second group) in a 1:1 ratio and then mixed with either distilled water (control group) or serum ex vivo. A pathologist blinded to our hypothesis inspected all solutions under light microscopy with 100× and 400× magnifications. Total number of particulate steroid aggregates and the number of particles forming each aggregate (recorded as single,1 double,2 triple,3 quadruple,4 or large [>4} crystals) were counted. Particle size and aggregate size were measured (in µm). The ratios of quadruple to total aggregates, large to total, and quadruple with large to total aggregates were calculated. Steroid-serum solutions and steroid-sterile water were then compared. RESULTS: Triamcinolone aggregates showed an increased crystal and aggregate size when compared with other steroids. Within the triamcinolone subgroup, the mixture of lidocaine 1% and serum resulted in the largest crystal aggregates. LIMITATIONS: Whole blood analysis may have provided a more physiologically accurate model but was not chosen due to poor microscopic analysis. Serum donor variability may also have affected particle characteristics. CONCLUSION: Fewer large triamcinolone aggregates were noted in the presence of serum when compared to the non-serum control groups. However, when compared to previously studied particulate steroids, it had the largest aggregates when added to serum.

Cervical Medial Branch Block Volume Dependent Dispersion Patterns as a Predictor for Ablation Success: A Cadaveric Study.

BACKGROUND: Neck pain is one of the most common causes of chronic pain and the fourth leading cause of disability worldwide; it is estimated that between 36% and 67% of this pain is due to facet arthropathy. For patients who have pain refractory to conservative treatments literature supports management with diagnostic cervical medial branch blocks (MBBs) to identify the associated facet innervation as the source of pain followed by therapeutic radiofrequency ablation (RFA) of the identified nerves. Cervical RFA has good published outcomes; however, the procedure is dependent upon the specificity of the diagnostic block to achieve maximal success. Currently, this prerequisite test has false positive rates between 27% and 63% and recent studies have shown that this may, in part, be a consequence of currently accepted injection volumes of 0.50 mL or more, which may decrease the sensitivity of MBBs. OBJECTIVE: To evaluate the possible differences in volume dispersion between 0.25 and 0.50 mL of injectate during cervical MBBs. STUDY DESIGN: Cadaveric study. SETTING: An academic medical center in the United States. PATIENTS: Not applicable. METHODS: This was a cadaveric study in which six subjects were chosen with intact cervical spines. Cervical MBB were performed bilaterally at the midcervical spine, using a posterior approach under fluoroscopic guidance. 0.25 or 0.50 mL of a 9:1 solution of Omnipaque 180 mg iodine/mL and 1% medical grade methylene blue were administered on the left and right sides, respectively. Postinjection computed tomography (CT) imaging and gross dissection were performed to assess injectate spread. MAIN OUTCOME MEASURES: Outcome measures after using commonly injected volumes for cervical MBB, included visualized and measured spread (by CT and gross dissection) of cervical medial branch blocks, coating adjacent structures not targeted by RFA. RESULTS: Postinjection CT imaging and cadaveric dissection demonstrated that, although both volumes adequately coated the medial branches, the 0.50 mL cohort reliably spread dorsally to superficial muscles (splenius) and nerves distant from the targeted nerves (dorsal motor branches to splenius), whereas the 0.25 mL injectate cohort was contained in the deep and intermediate muscular cervical layers directly juxtaposed to the targeted cMBBs. CONCLUSION: Results suggest that 0.50 mL injections of local anesthetic during cervical MBBs contacts many nonintended targets, thus decreasing the specificity of a targeted diagnostic cervical MBB. Furthermore, we demonstrated that 0.25 mL of injectate reliably bathed the cervical medial branches without extensive extravasation. This indicates that there would potentially be fewer local anesthetic effects on distant tissues, increasing the specificity of cervical MBBs and likely improving RFA planning.