Sample size
We performed a preliminary power analysis to calculate the sample size (G*power 3.1.9.2, UCLA, Los Angeles, CA, USA) in order to compare the intergroup mean values of BCTQ at baseline and 6 months post-injection.29 At least 46 subjects were required to achieve sufficient power ([1-β] = 0.8; α = 0.05; effect size = 0.85 because no preliminary data were available, we used a large effect size of 0.85).