Can we predict which patients with plantar heel pain are more likely to benefit from insoles? A secondary exploratory analysis of a randomized controlled trial

Table 4 Interaction between variables of interest and treatment with custom insoles compared to sham insoles for the total FFI score at 26-weeks follow-up

Variables	Unstandardized β (95% CI)	Interpretation
Body Mass Index (kg/m²)	0.49 (−1.00, 1.98)	Lower BMI is associated with a lower total FFI score in patients treated with custom insole (non-significant)**
Neuropathic pain DN4 total score (0–10)	1.58 (− 2.56, 5.73)	Lower score on the DN4 score for neuropathic pain is associated with a lower total FFI score in patients treated with custom insole (non-significant)**
Bilateral pain (yes)	−2.16 (− 21.49, 17.16)	Presence of bilateral pain is associated with a lower total FFI score in patients treated with custom insole (non-significant)**
Sex (male)	−12.10 (−29.46, 5.25)	Male sex is associated with a with a lower total FFI score in patients treated with custom insole (non-significant)**
FFI score at baseline	0.02 (−0.39, 0.43)	Lower FFI score at baseline is associated with a lower total FFI score in patients treated with custom insole (non-significant)**
First step pain at baseline	0.47 (−3.07, 4.01)	Lower pain score for first step pain at baseline is associated with a lower total FFI score in patients treated with custom insole (non-significant)**

*Variables were multiplied with a factor indicating treatment (custom insole vs sham)
**A lower total FFI is indicative of a lower pain and better function

ISSN: 1757-1146