Comparison of the effectiveness of local anesthesia for the digital block between single-volar subcutaneous and double-dorsal finger injections: a systematic review and meta-analysis of randomized control trials

Local anesthesia is an effective method to perform digital nerve blocks. In this study, we compare the effectiveness of single-volar subcutaneous and double-dorsal injection through a systematic review and meta-analysis of randomized controlled trials (RCTs). A systematic search of PubMed, Embase, and the Cochrane Library from inception to 7 April 2021 was performed. RCTs with the effects of single-volar subcutaneous and double-dorsal injection were eligible. Meta-analysis was performed using random effect models with pooled standardized mean differences (SMDs) and 95% confidence intervals (CI). RoB 2.0 and GRADE of Recommendation Assessment, Development, and Evaluation criteria were applied for evaluating the bias. A total of 2484 studies were initially identified, with 11 eligible RCTs finally included in the meta-analysis (1363 patients). The pooled data of nine studies showed single-volar injection had a statistically significantly lower pain score (pooled SMD: 0.20, 95% CI, 0.01 to 0.39, p = 0.041, I2 = 58%, N = 1187) and higher patient preference but invalid anesthesia at the dorsal proximal digit. No significant differences were observed in the onset of anesthesia, adjacent digit invalid numbness, distal phalanx invalid anesthesia, additional injection rate, and adverse effects. In conclusion, this meta-analysis of RCTs showed that the single-volar injection was associated with a lower pain sensation during injection and higher patient satisfaction with a reduced anesthetic effect over the proximal dorsal phalanx. Further high-quality RCTs with a higher number of cases are needed to validate our results.