Statistical Analysis

The improvements in MF and MIR were analyzed first using the paired Student t test; then, the Bonferroni test for multiple comparisons was used to assess the mean improvement in MF and MIR at 45°, 70°, and 90° of flexion in the St5°, St10°, and Complex5° groups. The differences in improvement in MF and MIR at each flexion angle in each single-dimensional change (St, Ar, and Ct) of 5° or 10° were also assessed using the paired Student t test and the Bonferroni test. P < .05 was considered statistically significant. All statistical analyses were performed using JMP PRO 15.0.0 software (SAS Institute Inc).

A post hoc power analysis with an effect size of 0.5 was performed as described by Cohen ⁶ ; the inclusion of 43 hips indicated a power of 0.74 with α = .05, which was considered a suitable sample size. The posterior power was calculated using G*Power, Version 3.1.9.6. ¹⁰