Single-Shot Versus Continuous Interscalene Blockade in Primary Shoulder Arthroplasty: A Systematic Review and Meta-Analysis of Randomized Controlled Trials and Observational Studies.

BACKGROUND: The optimal regional anesthesia strategy for anatomic and reverse total shoulder arthroplasty (aTSA/rTSA) remains a subject of debate. While single-shot interscalene blocks (SSIB) are often limited by short duration and potential rebound pain, continuous interscalene catheters (CIC) are associated with higher complication rates and procedural complexity. This meta-analysis evaluates the effectiveness and safety of both techniques, specifically investigating the impact of the local anesthetic agent. METHODS: A systematic search was conducted in PubMed, Embase, CENTRAL, and CINAHL through March 2026 for RCTs and observational studies. The primary outcome was pain intensity (VAS/NRS) at 24 hours. Secondary outcomes included opioid consumption, length of hospital stay (LOS), technical and block-related complications, and procedural costs. RESULTS: Seven studies involving 2,639 patients were included (1,182 SSIB, 1,457 CIC). No statistically significant global difference was found regarding 24-hour pain scores (MD -0.23; P = .70) or opioid consumption (P = .91). In subgroup analysis, CIC was associated with lower pain scores when standard local anesthetics were used (MD 1.18; P < .001), whereas SSIB with liposomal bupivacaine was associated with borderline lower pain scores (MD -1.02; P = .05); however, these differences lie at the lower margin of published thresholds for a minimal clinically important difference (MCID) in acute postoperative pain. A post hoc analysis at 48 hours (three studies, 695 patients) showed no significant difference (MD -0.81; P = .20). SSIB was associated with a more than fourfold lower rate of technical and block-related complications (0.4% vs. 4.6%; RR 0.22; P = .005). No significant difference was observed in LOS (P = .45); material costs, compared descriptively, were higher for CIC ($357-$474) than for SSIB ($24-$190). CONCLUSION: At 24 hours, SSIB was associated with analgesia comparable to CIC, with the direction of effect depending on the local anesthetic agent used. SSIB was associated with significantly fewer technical and block-related complications and lower material costs. These findings suggest a favorable risk-benefit profile of SSIB for primary shoulder arthroplasty, although outcomes beyond 48 hours require further investigation. LEVEL OF EVIDENCE: Level III, Systematic Review/Meta-Analysis, Treatment Study.