Fifteen studies were included (n=886 patients): 14 RCTs and one CCT. Twelve studies were of higher quality (score≥6) and three were of lower quality (score≤5).
Correlation between volume difference and pain relief was 0.8027 (p=0.002, 12 studies) for the immediate category, 0.5019 (p=0.168, nine studies) for the short-term category and 0.9470 (p=0.014, five studies) for the intermediate category. Insufficient data were available to calculate the correlation coefficient in the long-term category (one study).
There was a statistically significant difference when comparing the mean effect size where the volume injected was the same between the two groups (mean, standard deviation (SD): 0.07, ±0.26) with those where the volumes were different between comparison groups (mean, SD: 0.81, ±0.6) irrespective of the medications injected.