Does Reducing the Concentration of Bupivacaine When Performing Therapeutic Shoulder Joint Injections Impact the Clinical Outcome?

Abstract

Mixtures of local anesthetics and steroids are routinely injected intraarticularly to temporarily relieve joint pain, even though local anesthetics have been reported to cause chondrocyte death in a dose- and time-dependent manner. This study aimed to determine if intraarticular injections of bupivacaine 0.5% and bupivacaine 0.25% would provide similar pain relief. All fluoroscopically guided glenohumeral joint injections performed using 2.5 mL of bupivacaine and 0.5 mL (20 mg) of triamcinolone acetonide over a 42-month period were included if a pain score was recorded before, 5-10 minutes after, and 1 week after injection. Pain reduction of more than 2 points was considered much improved clinically with pain reduction of more than 1 point considered the minimum clinically important difference (MCID) threshold. Statistically significant and much improved pain reduction was achieved using both bupivacaine 0.5% and 0.25% 5-10 minutes (-3.7 points; 95% CI, -3.4 to -4.0 points; p ≤ 0.001; and -3.3 points; 95% CI, -3.0 to -3.5 points; p ≤ 0.001) and 1 week (-2.5 points; 95% CI, -2.2 to -2.9 points; p ≤ 0.001; and -2.1 points; 95% CI, -1.8 to -2.3 points; p ≤ 0.001) after injection, respectively. Adjusting for age, sex, pain score before injection, and indication, the mean decrease in pain was greater in the bupivacaine 0.5% group by 0.30 points 5-10 minutes after injection (95% CI, -0.03 to 0.63 points; p = 0.08) and 0.46 points 1 week after injection (95% CI, 0.13-0.77 points; p = 0.01). Both bupivacaine 0.5% and bupivacaine 0.25% provide statistically significant and much improved pain relief 5-10 minutes and 1 week after intraarticular glenohumeral injections. Bupivacaine 0.5% provided greater pain relief than bupivacaine 0.25%, but the difference was less than 0.5 points and therefore did not meet the MCID threshold.