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Sustained vagal activity with a failed shift in the sympathovagal balance toward sympathetic predominance in response to sitting after ISBPB is associated with the development of HBE.

BackgroundIn a previous biomechanical study, eccentric glenospheres with more inferior position of the center of rotation were shown to improve range of motion and reduce the incidence of scapular notching after reverse total shoulder arthroplasty (RSA). The purpose of this study was to compare the clinical and radiological results of RSA using an eccentric glenosphere to those using a concentric glenosphere and to determine the usefulness of the eccentric glenosphere.MethodsFrom 2009 to 2015, we performed a retrospective review of 20 consecutive patients who underwent RSA using a deltopectoral approach. Nine patients underwent RSA using a concentric glenosphere (group A) while 11 had an eccentric glenosphere (group B). The average follow-up period was 13.9 months (range, 12 to 18 months). All glenoid components were placed with 15° of inferior tilt. Clinical results were assessed using the visual analog pain scale score (VAS), the American Shoulder and Elbow Surgeon (ASES) score, the Korean shoulder scoring system (KSS), and the Constant score. On radiological evaluation, prosthesisscapular neck angle (PSNA), peg-glenoid rim distance (PGRD), scapular neck-inferior glenoshere rim distance (inferior glenoshpere overhang), acromion-greater tuberosity (AT) distance, glenoid-greater tuberosity (GT) distance, and severity of notching according to the Nerot-Sirveaux classification were assessed.ResultsThe clinical results improved significantly in both groups, but there was no statistically significant difference between the two groups. A significant intergroup difference was observed with regard to PGRD (24.8 ± 1.6 mm for group A vs. 22.2 ± 1.9 mm for group B; p = 0.002) and inferior glenosphere overhang (2.0 ± 1.7 mm for group A vs. 5.8 ± 1.6 mm for group B; p = 0.000). Seven of 9 patients in group A developed notching compared with 2 of 11 patients in group B (p = 0.022). The other radiological parameters such as inferior tilt and AT and GT distances were not significantly different between two groups. Complications such as loosening and scapular fractures did not occur.ConclusionsThe eccentric glenosphere in RSA was more effective in reducing the rate of notching than the concentric glenosphere although clinical outcomes were not significantly different in the short-term follow-up.

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Background A classical approach to produce interscalene brachial plexus block (ISBPB) consistently spares the posterior aspect of the shoulder and ulnar sides of the elbow, forearm, and hand, which are innervated by the lower trunk of the brachial plexus (C8–T1). As an alternative to the classical approach, a caudal approach to ISBPB successfully produces anesthesia of the ulnar sides of the elbow, forearm, and hand. However, its beneficial effects on anesthesia in the posterior aspect of the shoulder have not been investigated. In addition, the C8 nerve root is not routinely selectively blocked during ISBPB. Therefore, we will compare the C5 to C7 and C5 to C8 nerve root blocks during a caudal approach to ISBPB to assess the clinical benefit of C8 nerve blocks for the surgical anesthesia of the posterior aspect of the shoulder. Methods/design In this prospective parallel-group single-blind randomized controlled trial, 74 patients scheduled to undergo arthroscopic shoulder surgery under ISBPB are randomly allocated to receive the C5 to C7 or C5 to C8 nerve root block at a 1:1 ratio. The primary outcome is pain intensity, which is rated as 0 (no pain), 1 (mild pain), or 2 (severe pain), during the introduction of a posterior portal into the glenohumeral joint. The secondary outcomes are (1) the extent of the ipsilateral sensory, motor, hemidiaphragmatic, and stellate ganglion blockade, (2) changes in the results of a pulmonary function test, (3) incidence of complications related to ISBPB, (4) postoperative numerical pain rating scale scores, (5) patients’ satisfaction with the ISBPB, (6) dose and frequency of analgesic use, and (7) incidence of conversion to general anesthesia. Discussion This study is the first to evaluate the beneficial effects of the C8 nerve root block during ISBPB, which has rarely been performed due to the technical challenge in visualizing and blocking the C8 nerve root. It is expected that a C8 nerve root block performed during ISBPB will provide sufficient surgical anesthesia of the posterior aspect of the shoulder, which cannot be achieved by a classical approach to ISBPB. Trial registration ClicnicalTrials.gov, NCT03487874 . Registered on 4 April 2018. Electronic supplementary material The online version of this article (10.1186/s13063-019-3624-9) contains supplementary material, which is available to authorized users.