Summary

The addition of an intra-operative peri-articular cocktail injection appears to be a safe and effective method to reduce acute post-operative pain following TSA compared to an isolated interscalene nerve block.

Abstract

Introduction

Interscalene nerve block (INB) is as an effective technique to provide post-operative anesthesia for total shoulder arthroplasty (TSA). However, the analgesic effects of the block typically resolve between 8-and 24-hours following administration, which results in rebound pain and subsequent increased opioid utilization. With the aim of transitioning the shoulder arthroplasty procedure toward out-patient surgery, decreasing opioid consumption in the acute post-operative period is the main goal to achieve a shorter hospital stay. The objective of this study was to determine the effect that the combination of INB and intra-operative peri-articular injection (PAI) has on opioid consumption and acute post-operative pain scores in patients undergoing TSA. We hypothesized that the combination of INB + PAI will significantly reduce opioid consumption and pain scores for the first 24 hours following surgery as compared to INB alone.

Methods

We reviewed 130 consecutive patients who underwent elective primary TSA at a single tertiary institution. The first 65 patients were treated with INB alone, followed by 65 patients treated with INB + PAI. The PAI utilized was 50ml of a combination of Ropivacaine (123mg), Epinephrine (0.25mg), Clonidine (40mcg), and Ketorolac (15mg). The PAI was injected using a standardized protocol; 10ml into the subcutaneous tissues prior to incision, 15ml into the supraspinatus fossa, 15ml at the base of the coracoid process, and 10ml into the deltoid and pectoralis muscles. A standardized post-operative oral pain medication protocol was utilized for all patients. The primary outcome measured was acute post-operative opioid consumption represented by morphine equivalent units (MEU), while the secondary outcome measured was Visual Analog Scale (VAS) pain scores over the first 24 hours after surgery, operative time, length of stay, and acute peri-operative complications.

Results

There were no significant differences in patient demographics between the INB alone compared to patients with INB + PAI. Patients who received INB + PAI had a significantly lower 24-hour post-operative opioid consumption as compared to INB alone group (38.6±30.5 MEU versus 60.5±37.3 MEU, P<0.001). Moreover, the demand for rescue intravenous opioids from severe breakthrough pain was also decreased by 16.9% in INB + PAI group (20% versus 36.9%, P=0.033). Additionally, VAS pain scores for the first 24 hours following surgery in the INB + PAI group was significantly lower as compared to INB alone group (2.9±1.5 versus 4.3±1.6, P=<0.001). There were no differences between both groups in the operative time, length of inpatient stay and acute peri-operative complications.

Conclusion

Patients undergoing TSA with INB + PAI demonstrated significantly decreased 24-hour post-operative total opioid consumption and 24-hour post-operative pain scores as compared to group treated with INB alone. There was no observed increase in acute peri-operative complications related to PAI. Thus, the addition of an intra-operative peri-articular cocktail injection appears to be a safe and effective method to reduce acute post-operative pain following TSA compared to an isolated interscalene nerve block.

LEVEL OF EVIDENCE:
Level II, Prospective Cohort Design; Treatment Study

KEYWORDS:
Total shoulder arthroplasty, Interscalene nerve block, Peri-articular injection, Multimodal analgesia, Peri-operative analgesia, Opioid consumption