Anterior Glenoid Block as an Alternative Technique to Interscalene Brachial Plexus Block

Interscalene brachial plexus block is known for providing superior analgesia for shoulder procedures; however, there is a risk of hemi-diaphragmatic paralysis due to phrenic nerve palsy, which may restrict its use in certain populations.¹ The suprascapular, axillary, and subscapular nerves innervate the shoulder joint.^2,3 Recent anatomical data have helped anesthesiologists construct novel blocks that target the sensory afferents to the glenohumeral joint and acromioclavicular joint.⁴ One such example is pericapsular local anesthetic (LA) infiltration deep into the subscapularis muscle, with targets being the articular branches from the axillary and subscapular nerves that supply the glenohumeral joint.⁴

We present an anterior glenoid block that could be combined with a selective anterior suprascapular nerve block to potentially reduce the risk of phrenic nerve block after shoulder surgery.

METHOD

Blocking Techniques

The patient was supine for anterior glenoid block and a curvilinear transducer (2–6 MHz) was placed parallel to the clavicle’s underside. The transducer was then advanced caudally to reveal the larger tuberosity, smaller tuberosity, anterior articular glenoid, and subscapularis muscle (Figure A, B). At the glenoid fossa margin, the articular branches of axillary and subscapular nerves located deep to the subscapularis muscle innervate the superior/anteroinferior quadrants of the glenohumeral joint. Ropivacaine 0.5% 15 mL was injected medially to laterally through the deltoid and subscapularis muscles to bone contact (Figure C). We advocate injecting LA into the deep surface of the subscapularis muscle in high-body mass index (BMI) patients whose anterior glenoid may not be apparent on ultrasound scans due to its depth. The anterior suprascapular nerve block (0.5% ropivacaine 4 mL) was performed with the method described by Abdallah et al.⁵

Initial Clinical Experience

With the approval of the Ethics Committee of Shanghai Jiaotong University Affiliated Sixth People’s Hospital and the written informed patient consent, we conducted this procedure on 45 patients undergoing arthroscopic rotator cuff repair. The primary outcomes were as follows: (1) 11-point (0–10) numeric rating scale (NRS) pain score after surgery; (2) degree of preserved diaphragmatic function (DPDF): the ratio of postoperative to preblock (baseline) diaphragmatic excursion amplitude under M-mode ultrasonography;⁶ and (3) degree of preserved handgrip strength (DPHS): the ratio of postoperative to preblock (baseline) handgrip strength (the maximal force patients exerted when instructed to squeeze the dynamometer handles as tightly as feasible). Measurements were done at 4, 8, and 24 hours postoperatively. The data were summarized by mean and standard deviation (SD) for normally distributed continuous data, median and interquartile range (IQR) for nonnormally distributed continuous data, and percentages with a 95% confidence interval (CI) for categorical data.

RESULTS

Characteristics of the 45 participants were as follows: age, 43 (11) years; height, 169 (11) cm; weight, 62 (11) kg; sex, 26 (58%) women; and American Society of Anesthesiologists (ASA) physical status I and II. Thirty-nine patients (86.7%; 95% CI, 72.5%–94.5%) had mild pain (NRS ≤ 4) within 24 hours of the intervention (Table). Similarly, 39 (86.7%; 95% CI, 72.5%–94.5%) and 41 (91.1%; 95% CI, 77.9%–97.1%) patients showed diaphragm amplitude and grip strength values that were higher than 80% of their baseline levels. No complications related to bleeding, hematoma, infection, or nerve damage were observed.

DISCUSSION

Our Research Letter reports an anterior glenoid block for shoulder arthroscopy which may diminish the risk of phrenic nerve block. Blockade of the axillary and subscapular nerve’s articular branches may reduce the loss of grip strength associated with conventional interscalene block. We hypothesize that the anterior glenoid block may potentially provide effective analgesia after shoulder surgery. Randomized clinical trials are required to compare this block with other regional blocks used for shoulder surgery.

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