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Literature Review - May 2021

May 1, 2021, 01:00 AM by Sudheer Potru, DO, Emory University School of Medicine; Anthony Machi, MD, UT Southwestern Medical Center; and Jerry Jones, MD, University of Tennessee Health Science Center

Cite as: Potru S., Machi A., Jones J. Literature review - May 2021. ASRA News. 2021;46.


Editor’s note: “Literature Review” is a feature designed to provide you with brief summaries of recent articles of interest, particularly from sources that our readers might not normally consume. 

Percutaneous Peripheral Nerve Stimulation of the Medial Branch Nerves for the Treatment of Chronic Axial Back Pain in Patients After Radiofrequency Ablation

Deer TR, Gilmore CA, Desai MJ, et al. Pain Med. 2021;22(3):548-560.

Selection and summary by Sudheer Potru, DO

Introduction: While lumbar medial branch radiofrequency ablation is an effective treatment for axial low back pain, it involves denervation of the multifidus and often yields decreasing levels of pain relief when done repeatedly over time.  An axial pain treatment that is motor-sparing and long-lasting is desired.

Methods: A prospective, multicenter trial was performed in 15 patients with chronic axial low back pain who had medial branch radiofrequency ablation greater than six months prior to enrollment. Percutaneous peripheral nerve stimulation (PNS) leads were placed in all subjects near the medial branch nerves at the level closest to the center of the painful region of the low back for a total of 60 days. Patients were excluded if they had radicular pain, a history of prior lumbar surgery, scoliosis, pending litigation, or active depression identified by a score >20 on the Beck Depression Inventory. Inventories were used to measure pain interference, pain intensity, and disability at two and five months post-placement.

Results: The average pain intensity score was reduced from 6.3 to 2.4 (SD=1.6, p<0.0001). Of the 15 participants, 13 had a clinically meaningful reduction in average pain intensity and disability (at least 10-point reduction in Oswestry Disability Index), and 12 out of 15 had clinically significant reduction in pain interference (at least 30% reduction in Brief Pain Inventory-9 score).  

At five months, 11 out of 15 participants (73%) experienced clinically significant reduction in pain intensity (at least 50%) and pain interference, and 67% of participants reported clinically significant improvements in disability. All but one patient (93%) had clinically significant improvement in at least one of the three major outcomes listed. Four participants experienced lead migration or dislodgement and received lead replacements per protocol.

Key point: Peripheral nerve stimulation may be a highly effective treatment for those with chronic axial low back pain and should be considered as part of the treatment algorithm moving forward.


Optimized Acupuncture Treatment (Acupuncture and Intradermal Needling) for Cervical Spondylosis-Related Neck Pain:  A Multicenter Randomized Controlled Trial

Chen L, Minying L, Fan L, et al. Pain. 2021;162(3):728-739.

Selection and summary by Sudheer Potru, DO

Introduction: Neck pain due to cervical spondylosis is a significant public health issue with a large economic burden.  Although helpful treatments exist, including physical therapy and cervical medial branch radiofrequency ablation, many of these lack conclusive evidence. 

Methods: A multicenter, single-blinded, randomized controlled trial was performed to study the efficacy of optimized acupuncture versus shallow acupuncture and sham acupuncture on cervical spondylosis-related (CS-R) neck pain.  Typically, in the authors’ environment in China, daily acupuncture is employed for CS-R neck pain and is associated with poor compliance and lack of efficacy. Instead the authors utilized an optimized acupuncture regimen, which allowed for treatment every other day and included both acupuncture and intradermal needling.

Patients were included if they had a diagnosis of cervical spondylosis based on imaging, age range 18-60 years, multiple episodes of neck pain > 30 minutes in the previous month, VAS score >3 once in the past week, and no history of acupuncture treatment in the previous three months. Exclusion criteria included diagnosis of cervical spondylosis with myelopathy, presence of systemic diseases (including tumors and diabetes mellitus), history of neck trauma (including vertebral fracture or surgery), history of congenital spinal abnormality, neurological impairment related to myasthenia gravis or abnormal reflexes, and pregnancy/lactation.

Each treatment group had nearly 300 participants. All patients in all groups received treatment from the same nine providers for four weeks. Sham acupuncture points were set close to the actual acupuncture points to prevent patient ability to distinguish location. The Northwick Park Neck Pain Questionnaire (NPQ) and Short Form-36 (for quality-of-life measures) were assessed at four weeks (immediately post-intervention), eight weeks, and 16 weeks.

Results: At weeks 4, 8, and 16, significant NPQ differences were observed between the optimized acupuncture group and the shallow and sham groups, although all three cohorts demonstrated significant improvements in both NPQ and SF-36 over the 16-week study period. Most SF-36 scores were higher in the optimized acupuncture groups versus the shallow and sham cohorts. However, wide variability existed in the treatment effects overall.

Key point: An optimized acupuncture regimen including intradermal needling may be more assistive than regular acupuncture in treatment of cervical spondylotic neck pain and could be an effective adjunct for this type of neck pain.


Quadriceps Weakness After Single-Shot Adductor Canal Block

Yee EJ, Gapinski ZA, Ziemba-Davis M, et al. J Bone Joint Surg. 2021;103(1): 30-36.

Selection and summary by Anthony Machi, MD

Introduction: The adductor canal block (ACB) is commonly utilized for analgesia for total knee arthroplasty (TKA) because it is efficacious and generally does not cause motor blockade. However, motor blockade can result from ACB and is well documented in the literature. Prior studies investigated technical aspects that led to the development of motor blockade such as location, dose of injectate, and volume of injectate. Other factors, such as anatomic differences and tissue characteristics, may contribute to the development of motor blockade too. In addition, the prevalence of motor blockade resulting from ACB in a typical practice has not been well characterized.

Methods: The authors performed a retrospective examination of 1,083 patients who underwent TKA from 2014-2017 at an academic hip and knee center. Patients received multimodal analgesia and an ACB after induction of anesthesia with a spinal and a standardized light general anesthesia. The ACB was performed in the distal canal with a long acting local anesthetic with or without adjuvants (Table 2). Weakness was assessed by manual muscle testing by physical therapists postoperatively on the day of surgery unless patients’ surgery concluded late in the day, when it was then assessed on postoperative day (POD) 1.

Results: Ninety-two of 1,083 (9%) of patients had quadriceps weakness. Weakness was associated most strongly with the highest milliliters of local anesthetic per kg/m2, decreased body mass, female sex, and use of epinephrine as an adjuvant. The majority (83%) of patients were assessed on the day of surgery and 17% on POD 1. The prevalence of weakness was 9.9% in patients assessed on POD 0 and 4.6% on POD 1, indicating a likely association with the ACB.

Key point: The ACB appears to have 9% prevalence of quadriceps weakness in patients receiving TKA by a conservative assessment, and patient factors, such as the ratio of muscle to fat, may influence proximal spread to the femoral triangle.

Liposomal Bupivacaine Interscalene Nerve Block in Shoulder Arthroplasty Is not Superior to Plain Bupivacaine: A Double-Blinded Prospective Randomized Control Trial

Hattrup SJ, Chung AS, Rosenfeld DM, et al. J Shoulder Elbow Surg. 2021;30(3): 587-598.

Selection and summary by Jerry Jones, MD

Introduction: Interscalene nerve blocks with long-acting local anesthetics are commonly performed to minimize the negative consequences of pain and opioid use after major shoulder surgery. Previous studies have shown some analgesic and opioid-sparing benefits after shoulder surgery with the addition of liposomal bupivacaine to plain bupivacaine for interscalene nerve blocks or when compared to placebo. Outcomes for other orthopedic surgeries with liposomal bupivacaine have been mixed. Large, prospective studies have not been performed comparing single injection interscalene nerve blocks with bupivacaine and bupivacaine with liposomal bupivacaine to evaluate clinically meaningful differences following major shoulder surgery.

Methods: The authors performed a prospective, double-blinded study on 104 patients undergoing a primary (anatomical or reverse) total shoulder replacement utilizing an interscalene block with either 25 ml of bupivacaine 0.5% or 10 ml of liposomal bupivacaine (133 mg) along with 7.5 ml of 0.5% and 7.5 ml of bupivacaine 0.25% (25 ml total) for postoperative pain. In addition to intravenous dexamethasone at the time of the nerve block, fentanyl was given IV intraoperatively, oral acetaminophen 1,000 mg was scheduled every 8 hours, and rescue analgesics included tramadol, oxycodone, and fentanyl IV according to the severity of pain. The authors hypothesized a lower 72-hour average pain score, a longer time until block cessation, lower overall opioid consumption, and better patient satisfaction score in patients receiving liposomal bupivacaine.
Results:  No significant differences in average pain scores, in time to first opioid rescue, total morphine milligram equivalent use, or patient satisfaction with analgesia were identified. While on the second postoperative day, a statistically significant improvement in average visual analogue pain score in the liposomal bupivacaine group was found (2.4 vs 3.3, P= 0.0409), it was less than the established minimal clinically important difference.

Key point: In the context of severely painful shoulder surgery and limited multimodal analgesia, the addition of liposomal bupivacaine to plain bupivacaine for an interscalene nerve block provides no additional clinically relevant analgesic or opioid-sparing benefit to plain bupivacaine.

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