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).