Analgesic efficacy of suprascapular nerve block versus combined suprascapular and axillary nerve block in patients undergoing shoulder arthroscopy: A prospective, randomized, comparative study

Abstract

Background and aim:  This study aimed to compare the efficacy of combined suprascapular nerve block (SSNB) and axillary nerve block (ANB) with SSNB alone for analgesia after shoulder arthroscopy in terms of level of pain scores, total analgesic consumption and patient satisfaction in 24 hours.  

Methods: Forty one patients posted for shoulder arthroscopy were randomly allocated into two groups, group S (n=20), receiving SSNB and group C (n=21) receiving combined SSNB and ANB. Visual analogue scale (VAS) both at rest and during movement at 1, 3, 6, 12, 24 hours and at the time of first demand, total consumption of analgesics in 24 hours and patient satisfaction score at 12 and 24 hours were noted.

 Results: The VAS scores both at rest and during movement were significantly less in group C at 1, 6, 12 hours and at the time of first demand of analgesic (p < 0.05).  Compared to group S, group C had a longer pain free duration (154.3 ± 11.41 min vs 36.60 ± 6.553 min; p < 0.001) and lesser cumulative consumption of pethidine (300.0 ± 8.894 mg vs 336.8 ± 13.27 mg; p = 0.0256). The satisfaction level was better in group C at 12 hours (p = 0.002) but comparable to the group S at 24 hours (p= 0.0673). 

Conclusion: Combined SSNB and ANB provided better pain relief in first 12 hours, better patient satisfaction in the first 12 hours and decreased overall consumption of analgesics in the first 24 hours compared to SSNB alone.  

Introduction

Immediate postoperative pain can be severe and is an important outcome measure for patients in shoulder arthroscopic surgeries.^[1] In addition to keeping the patient comfortable, adequate pain control enhances the recuperation after surgery. Moreover, shoulder arthroscopic surgeries are frequently performed as ambulatory procedures and inadequate pain relief can be a reason for readmissions if not adequately dealt.

Interscalene block (ISB) is the most widely used and studied technique for post shoulder arthroscopy pain relief and is associated with certain unpleasant adverse effects like   Horner’s syndrome, phrenic nerve paralysis and a potential risk of intradural injection.^[2] Suprascapular nerve block has been suggested as an alternative and safer block for postoperative analgesia in shoulder arthroscopy.^[3,4] Although some authors have found it to be inadequate to provide an effective pain relief.⁴ As suprascapular nerve contributes to 70% of the sensory nerve supply to the shoulder joint, and axillary circumflex nerve is the other major nerve (contributing to 25%), therefore a combined block of these two nerves should provide more effective pain relief than SSNB alone. 

We conducted this prospective, randomized study to compare the efficacy of combined SSNB and ANB with SSNB alone for post operative pain relief after shoulder arthroscopic procedures in terms of level of pain scores, total analgesic consumption, patient satisfaction and adverse effects in first twenty four hours after surgery. We hypothesized that combined block (SSNB + ANB) will be more effective than SSNB alone in relieving post operative pain following shoulder arthroscopic surgeries.

Materials And Methods

This prospective, randomized, comparative study was approved by the institutional ethics committee at KPC Medical College and Hospital, Kolkata (No. KPCMH/Ethics/19/184 dated 01/07/2019) and was registered in the clinical trial registry - India (CTRI/2021/02/031042). All procedures performed in the study were in accordance with the ethical guidelines of the declaration of Helsinki. Before inclusion in the study, voluntary written informed consent was obtained from all participants.

Forty one American Society of Anaesthesiologists (ASA) grade I and II patients older than 18 years of age presenting for shoulder arthroscopic surgery were included in the study. Patients who were allergic to the medications used in this study, those with a contraindication to peripheral nerve block (puncture site infection, bleeding disorders), those who did not understand the visual analogue scale (VAS), or those who refused for the nerve block were excluded from the study.

During the pre-anaesthesia consultation, the study and procedure were explained to the patients in their own language and a written informed consent was obtained. Upon arrival in the operating room, monitoring lines for electrocardiogram (ECG), noninvasive blood pressure (NIBP), pulse oximetry (SpO2) were attached and an 18 or 20-G peripheral venous cannula was placed in the opposite upper limb to start an infusion of ringer lactate. With the help of computer generated randomization patients were divided in two groups - Group S (n=20) in which patients received SSNB alone and Group C (n=21) in which patients received a combined block (SSNB + ANB).

Performing the Blocks:

Suprascapular nerve block: SSNB was performed using the technique of Meier ^[5] with the aid of a peripheral nerve stimulator (Stimuplex HNS 12). With the patient in the sitting position and arm in complete adduction, a line connecting the lateral part of the acromium and the medial end of the spine of the scapula was established. A 22 guage, 10 cm insulated needle was inserted at a point located 2 cm medial and 2 cm cephalad to the midpoint of this line. The direction of the needle was lateralocaudal (45° in the coronal plane), with a ventral lean of about 30°. After the stimulation of infraspinatous muscle was achieved at the initial current of 1.5 mA and then at 0.5 mA, 10 mL of 0.5% ropivacaine was injected slowly after negative aspiration.

Axillary nerve block:   ANB was performed using the technique of Price ^[6] with the aid of a peripheral nerve stimulator (Stimuplex HNS 12).  With the patient in sitting position and arm in adduction, a line joining the anterior aspect of the acromium and the inferior angle of the scapula was drawn across the skin. From the midpoint of this line a horizontal line was drawn laterally. From the postero-lateral aspect of the acromium, a vertical line was traced down right behind the humerus. The point of intersection of this line with the horizontal line was the needle puncture site where a 22 guage, 10 cm insulated needle was passed straight anterior, towards the posterior aspect of the humerus. At the depth of 6-8 cm with a current of 1.5 mA twitches in the anterior deltoid were observed which were further confirmed with a current of 0.5 mA and 10 mL of 0.5% ropivacaine was injected slowly. 

After the block, patients were monitored for 15 minutes before giving general anaesthesia and the success of block was assessed by testing for cold sensation using spirit soaked cotton swab along the distribution of suprascapular and axillary nerves.

General anaesthesia:

 After preoxygenation, induction was done with injection propofol 2 mg kg^-1; relaxation was achieved with injection rocuronium to facilitate intubation. Fentanyl 2 µg kg^-1 was used for intraoperative analgesia. Anaesthesia was maintained with nitrous oxide, oxygen and sevoflurane. Thirty minutes before extubation all the patients received 20 mg kg^-1 paracetamol intravenously. Neostigmine with glycopyrrolate was used to reverse the muscle relaxation; patients were shifted to recovery room after extubation. 

Parameters observed:

Post-operative pain was assessed using VAS (at rest and during movement) at 1 hour, 3 hours, 6 hours, 12 hours and 24 hours after surgery. The 11 point VAS ranged from 0 (no pain) to 10 (worst imaginable pain). VAS was also noted when patients demanded the analgesic for the first time.

All the patients were given injection pethidine 1.5 mg kg^-1, upto 100 mg, intramuscularly when they demanded or when VAS was 4 or more and the total consumption of the drug in the 24 hours was noted.

Patient satisfaction was assessed on a three point scale with 1 (dissatisfied), 2 (moderately satisfied) and 3 (highly satisfied) at 12 hours and 24 hour postoperatively.

Patients were also monitored for any adverse effects for the 24 hours like nausea, vomiting, respiratory depression, itching, etc.

Sample size calculation and statistical analysis: To have an adequate study power the required sample size was calculated using Clin Calc, an online sample size calculator (www.clincalc.com/stats/samplesize.aspx). Considering an alpha level (probability of type I error) of 0.05 and beta level (probability of type II error) of 0.05 to establish the desired power of 95%, 20 patients were required for each group. 10% i,e four patients were added in anticipation of  attrition. So a total of 44 patients were included in the study. The normal (Gaussian) distribution of the data was determined using Shapiro-Wilk test and statistical significance was analyzed by Student’s t-test, Mann-Whitney U test, and Fisher’s exact test using GraphPad PRISM 9, a p value <0.05 is considered significant.

Results

A total of 44 patients were recruited out of which three patients were excluded from the study, two for not meeting the inclusion criteria and one for refusing to participate. Therefore 41 patients were included in the study 20 in the group S and 21 in the group C (Figure-1). The anthropometric data, duration of surgery and surgical procedures were comparable in the two groups (p > 0.05) (Table-1). The VAS scores both at rest and movement were significantly reduced in patients receiving combined block (SSNB + ANB)  at 1 hour, 6 hours, 12 hours and at the time when patient first demanded analgesic (p < 0.05). However, at 3 hours and 24 hours the VAS scores at rest as well as at movement were comparable for both the groups (p > 0.05) (Table-2, Figure-2). 

Not only the VAS scores were significantly lesser in the group C (4.81 ± 0.13) compared to group S (6.6±0.18), the time for the first demand of analgesic was also significantly longer (154.3 ± 11.41 min vs 36.60 ± 6.553 min; p < 0.001). The patients in group S required a significantly lesser cumulative parenteral pethidine (300.0 ± 8.894 mg) compared to those of  group S (336.8 ± 13.27 mg) in the 24 hours period (p = 0.0256) (Table-3).

The number of patients who were highly satisfied in the group C were significantly more at 12 hours (p = 0.002), however, at 24 hours the satisfaction scores were comparable for both the groups (p > 0.0673) (Table-4, Figure-3).

Six patients in group S and five patients in group C had experienced nausea. None of the patients had any episode of vomiting, respiratory symptoms, itching or allergic reactions. 

Discussion

Arthroscopy is the preferred technique for shoulder orthopaedic surgeries as it allows small incisions making the surgery less invasive. Arthroscopic surgery has quicker recovery, reduces hospitalization time, allows an early return to the normal activity and hence is frequently done as an ambulatory procedure. However, it is associated with moderate to severe pain in the postoperative period which is more during movement. The pain can hinder early mobilisation and initiation of physiotherapy, and sometimes, delays discharge or can lead to readmission.^[1] Shoulder joint and the peri-articular tissues are highly innervated and postoperatively there is massive nociceptive discharge which produces deep somatic pain and bouts of reflex spasm of muscles.^[7] Systemic drugs both NSAIDs and opioids are relatively inadequate to control the post-operative pain following shoulder surgery and peripheral nerve blocks are often required as a part of multimodal analgesia.^[2] ISB is the most widely used peripheral nerve block for anaesthesia and postoperative analgesia of shoulder surgeries.^[2,3]  However, it is associated with adverse effects like diaphragmatic paralysis due to phrenic nerve block and a potential risk of pneumothorax and inadvertent epidural or vertebral artery injection which can sometimes lead to serious complications.^[4] Other regional techniques like pericapsular block, intraarticular injection, suprascapular block are also practiced either alone or in combination with ISB with varying results. SSNB was advocated as an alternative to ISB for its diaphragm sparing effect, relative safety and acceptable effectiveness.^[8,9] However, there are studies that have questioned the efficacy of SSNB alone for the adequate pain relief following shoulder arthroscopic surgeries.^[10,11] The major motor and sensory innervation to the shoulder is from the suprascapular nerve and circumflex axillary nerve, while minor sensory innervation is from the lateral pectoral, musculocutaneous, subscapular and supraclavicular nerves.^[2] Therefore, the blockade of the two major nerves should provide a better postoperative pain relief.  Changjiao Sun et al^[4] in a meta- analysis of 17 randomized controlled trials involving 1255 patients  have observed   that ISB though gives better analgesia in the immediate post-operative period is associated with adverse effects which can be of concern in patients of severe obstructive pulmonary disease, obstructive sleep apnoea and morbid obesity. They concluded that SSNB is equal to or even better than ISB in offering post operative analgesia especially in later time (8-12 hours after operation). SSNB is still practised as an alternative to ISB for postoperative analgesia in shoulder arthroscopy.^[4]  Price DJ initiated the use of ANB with SSNB for shoulder arthroscopic surgeries and evaluated the effectiveness of the dual block in 60 patients and classified it as shoulder block.^[6] The technique was simultaneously evolved  by Checcucci et al who found it to be an effective and safe technique for intraoperative anaesthesia and postoperative analgesia for certain shoulder arthroscopic surgeries.^[12] 

In the present study the patients who received SSNB alone had requested the first analgesic within an hour of completion of surgery. Suprascapular nerve though supplies a major part of the sensory fibres to the joint, has hardly any cutaneous innervation, therefore does not provide analgesia from skin incisions and hence additional approach of pain control was required immediately after surgery.  On the contrary patients who received a combined shoulder block were comfortably pain free for a significantly longer duration of time and had lower VAS scores at first demand, 1 hour, 6 hours and 12 hours both at rest and during movement. Patients who were highly satisfied were significantly more in the combined block group at 12 hours but at 24 hours the VAS scores as well as the satisfaction scores were comparable in both the groups. Lee et. al. compared a combined SSNB and ANB to SSNB alone in patients undergoing shoulder arthroscopy and reported significantly lower mean VAS scores and high satisfaction levels in combined group at postoperative 1, 3, 6, 12, 18 and 24 hours.^[13]  SH Ko et. al. compared the effect of arthroscopically guided SSNB and blinded ANB with those of blinded SSNB in terms of postoperative pain and satisfaction within the first 48 hours after arthroscopic rotator cuff repair.^[14] A catheter was inserted and kept in situ for the repeat injection at 12 hours in arthroscopically guided SSNB. They observed lower pain scores and greater satisfaction levels with SSNB and ANB compared to SSNB alone during the study period. Better analgesia and patient satisfaction with the combination block was demonstrated in another study by Park et. al.^[15]  They compared a combination of SSNB, ANB and intravenous patient controlled analgesia (PCA) with SSNB and intravenous PCA and only intravenous PCA.  The VAS scores of the combination block group were significantly lower than the other two groups at different time points up to 48 hours with episodes of rebound pain at 12 and 36 hours which were attributed to the attenuation of block effect. 

The findings of the present study corroborates with the results of other authors for first 12 hours where the pain scores were lower and satisfaction scores better in SSNB and ANB group. It has been described that the SSNB seems to be less effective in treating early postoperative pain but is associated with effective pain control at 24 to 48 hours.^[4]  Jeske et. al. have also described that SSNB with 10 mL of 1%  ropivacaine have a duration of 24 to 48 hours.^[16] There is no study which has evaluated the duration of ANB individually. Our findings are in accordance with the results of a recent meta-analysis by Zhao et al.^[17] The authors compared the analgesic efficacy and safety of SSNB + ANB with SSNB and ISB and found that SSNB + ANB and ISB provided better analgesia than SSNB alone in the first 48 hours after surgery. They also observed that SSNB + ANB provided an equivalent pain relief as ISB in the first 12 hours. Our results further strengthen the fact that the effect of ANB is conspicuous in the first 12 hours of the postoperative period as after 12 hours the pain and satisfaction scores were comparable in both the study groups. 

Basat et al have used an arthroscopic approach to block and catheterize the two nerves during shoulder arthroscopy for rotator cuff repair.^[18] The catheter was utilized for postoperative supplementation of the local anaesthetic and steroids injection. This technique though provides an excellent pain relief is technically more challenging and cannot be done pre-emptively, besides the in situ catheters can be associated with complications like displacement, infection etc. Although, the overall analgesic consumption was significantly lesser in the combined block group, the incidence of postoperative nausea and vomiting was not significantly different. All study subjects had received intravenous ondensetron 4 mg at 8 hour intervals. 

Present study very well demonstrates the effectiveness of a combined SSNB and ANB over SSNB alone for better analgesia following shoulder arthroscopy in the early postoperative period, however there are certain limitations of this study. First, the safety of the SSNB and ANB in terms of preservation of respiratory function is not evaluated. Although both SSNB and ANB are phrenic nerve sparing blocks, but it’s a known fact that an accessory phrenic nerve is present in 60-75% of the individuals and provides an independent contribution to the phrenic nerve.^[19] The anterior approachof SSNB is more frequently associated with phrenic nerve involvement. An ultrasonographic assessment of the diaphragm after the block would have more clearly evaluated the involvement of the phrenic nerve with these nerve blocks. Second, the role of SSNB alone in the postoperative pain relief could not be established as a control group was not included in the study.  

Conclusion

Compared to SSNB alone, combined SSNB and ANB block provided better pain relief in first 12 hours, better patient satisfaction in the first 12 hours and a reduced overall consumption of analgesics in the first 24 hours after shoulder arthroscopy.  

Declarations

Author’s contributions: 

1. Subrata Ray: Overall study plan, study conception, supervision, execution, data acquisition, data management, literature search, manuscript writing.
2. Anuradha Mitra: Execution of study, data acquisition, data management, literature search, manuscript editing.
3. Ramapati Sanyal: Data acquisition and management, statistical analysis, manuscript editing.
4. Tabish Hussain: Statistical analysis and interpretation of data, revising the article critically for intellectual content.
5. Anjum Naz: Design, conception and execution of study, data management, literature search, manuscript writing and editing.

References

1. Rasmussen JK, Nikolajsen L, Bjørnholdt KT. Acute postoperative pain after arthroscopic rotator cuff surgery: A review of methods of pain assessment. SICOT-J. 2018; 4: 49.
2. Hewson DW, Oldman M, Bedforth NM. Regional anaesthesia for shoulder surgery. BJA Education 2019;19: 98-104  
3. Hussain N, Goldar G, Ragina N, Banfield L, Laffey JG, Abdallah FW. Suprascapular and Interscalene Nerve Block for Shoulder Surgery: A Systematic Review and Meta-analysis. Anesthesiology. 2017; 127(6): 998-1013.
4. Sun C, Ji X, Zhang X, Ma Q, Yu P, Cai X et al. Suprascapular nerve block is a clinically attractive alternative to interscalene nerve block during arthroscopic shoulder surgery: a meta-analysis of randomized controlled trials. J Orthop Surg Res. 2021; 16(1): 376. 
5. Meier G, Bauereis C, Maurer H. The modified technique of continuous suprascapular nerve block. A safe technique in the treatment of shoulder pain. Anaesthesist. 2002;51: 747-53.
6. Price DJ. The shoulder block: a new alternative to interscalene brachial plexus blockade for the control of postoperative shoulder pain. Anaesth Intensive Care. 2007; 35(4): 575-81. 
7. Lanna M, Pastore A, Policastro C, Iacovazzo C. Anesthesiological considerations in shoulder surgery. Transl Med UniSa. 2012; 3: 42-48.
8. Konradsen LKP, Larsen VHBH. Suprascapular nerve block or interscalene
    brachial plexus block for pain relief after arthroscopic acromioplasty. Ambul
    Surg. 2009; 15: 16–9.
9. Lim YC, Koo ZK, Ho VW, Chang SS, Manohara S, Tong QJ. Randomized,
    controlled trial comparing respiratory and analgesic effects of interscalene,
    anterior suprascapular, and posterior suprascapular nerve blocks for
    arthroscopic shoulder surgery. Korean J Anesthesiol. 2020; 73(5): 408–16.
10. Desroches A, Klouche S, Schlur C, Bauer T, Waitzenegger T, Hardy P.
     Suprascapular nerve block versus interscalene block as analgesia after
     arthroscopic rotator cuff repair: a randomized controlled non-inferiority trial.
     Arthroscopy. 2016; 32(11): 2203–9. 
11. Kumara AB, Gogia AR, Bajaj JK, Agarwal N. Clinical evaluation of post-operative analgesia comparing suprascapular nerve block and interscalene brachial plexus block in patients undergoing shoulder arthroscopic surgery. J Clin Orthop Trauma. 2016; 7(1): 34–9. 
12. Checcucci G, Allegra A, Bigazzi P, Gianesello L, Ceruso M, Gritti G. A new technique for regional anesthesia for arthroscopic shoulder surgery based on a suprascapular nerve block and an axillary nerve block: an evaluation of the first results. Arthroscopy. 2008; 24(6): 689-96. 
13. Lee JJ, Kim DY, Hwang JT, Lee SS, Hwang SM, Kim GH, Jo YG. Effect of ultrasonographically guided axillary nerve block combined with suprascapular nerve block in arthroscopic rotator cuff repair: a randomized controlled trial. Arthroscopy. 2014; 30(8): 906-14.
14. Ko SH, Cho SD, Lee CC, Choi JK, Kim HW, Park SJ, et al. Comparison of Arthroscopically Guided Suprascapular Nerve Block and Blinded Axillary Nerve Block vs. Blinded Suprascapular Nerve Block in Arthroscopic Rotator Cuff Repair: A Randomized Controlled Trial. Clin Orthop Surg. 2017; 9(3): 340-7.
15. Park JY, Bang JY, Oh KS. Blind suprascapular and axillary nerve block for post-operative pain in arthroscopic rotator cuff surgery. Knee Surg Sports Traumatol Arthrosc. 2016; 24(12): 3877-83. 
16. Jeske HC, Kralinger F, Wambacher M, Perwanger F, Schoepf R, Oberladstaetter J, et al. A randomized study of the effectiveness of suprascapular nerve block in patient satisfaction and outcome after arthroscopic subacromial decompression. Arthroscopy. 2011; 27(10): 1323-8.
17. Zhao J, Xu N, Li J, Liang G, Zeng L, Luo M, et al. Efficacy and safety of suprascapular nerve block combined with axillary nerve block for arthroscopic shoulder surgery: A systematic review and meta-analysis of randomized controlled trials. Int J Surg. 2021; 94: 106111. 
18. Basat HÇ, Uçar DH, Armangil M, Güçlü B, Demirtş M. Post operative pain management in shoulder surgery: Suprascapular and axillary nerve block by arthroscope assisted catheter placement. Indian J Orthop. 2016; 50: 584-9.
19. Loukas M, Kinsella CR Jr, Louis RG Jr, Gandhi S, Curry B. Surgical anatomy of the accessory phrenic nerve. Ann Thorac Surg. 2006;82(5):1870-5. 

Tables

Table-1: Patient characteristics. Data is represented as mean ± SEM or numbers. Statistical analysis was done by Student's t-test (for data with normal distribution) and Mann-Whitney U test (for data with non-normal distribution) using GraphPad PRISM 9, p value < 0.05 is considered significant.

Table-2: Postoperative pain score. Pain was assessed with VAS with 0 = no pain and 10 = worst imaginable pain. Data is represented as mean ± SEM. Statistical analysis was done by Mann-Whitney U test using GraphPad PRISM 9, p value <0.05 is considered significant.

Table-3: Time of first demand of analgesia and total consumption of analgesics. Data are expressed as mean ± SEM and statistical analysis was done by Student's t-test using GraphPad PRISM 9, p value <0.05 is considered significant.

Table-4:  Satisfaction scores of patients. Data is expressed as numbers and analyzed with Fischer exact test using GraphPad PRISM 9.   P<0.05 is significant.