Is subcutaneous volar nerve block injection associated with a lower invalid anesthesia rate than traditional dorsal digital nerve block injection for patients presenting with finger injury requiring regional anaesthesia? – An Update

Objective: To test whether selection bias has affected the reported effect estimate for subcutaneous volar nerve block injection in comparison to traditional dorsal digital nerve block injection (RD –0.39. 95%CI: -0.47 to -0.30), in order to reduce the invalid anesthesia rate for patients with finger injury requiring regional anaesthesia. Method: Trial adjusted, simulated comparator trial (SCT) based I2 test for single randomised controlled trials, using revised I2 threshold limits. Result: A baseline covariate imbalance, either due to chance or due to selection bias was established, being equivalent to selection bias level = B% 0-30 (Bias category = 1). This level suggests that 0-30% of (0 – 123 of the total 409) subjects were non-randomly allocated in favour of one treatment group above the other. Conclusion: The effect estimate reported by the tested trial suggests a significant difference between the compared procedures in favor of subcutaneous volar nerve block for reducing the invalid anesthesia rate. The selection bias level, estimated by use of the trial adjusted, simulated comparator trial (SCT) based I2 test for single RCTs, B% = 0-30, appears to be not high enough in order to have affected the reported estimate. In line with new findings, this report updates previous report to the same RCT: EBSM Volume 2, Issue 2, 2026 Pages 27-30, DOI: 10.5281/zenodo.17760880.