Clinical outcomes of optimized versus plain prefabricated insoles for mechanical foot pain in subtle Cavus foot: A randomized controlled trial.

Abstract

Subtle cavus foot (SCF), identified by the "peek-a-boo" sign and a positive Coleman block-test, is frequently associated with mechanical foot pain. While prefabricated insoles are commonly used in clinical practice, evidence supporting their effectiveness in SCF - particularly when modified according to SCF-specific design principles - is limited. This prospective randomized controlled trial compared Specifically Optimized Prefabricated Insoles (SOPI) with unmodified Plain Prefabricated Insoles (PPI) in individuals with clinically identified SCF and mechanical foot pain. Twenty-nine participants were randomized; 26 completed the study (13 per group). SOPI were modified in-office using forefoot valgus wedging and first-ray fill reduction, while PPI were provided as-is. The primary outcome was the Foot Function Index (FFI), assessed at baseline and at 1, 2, and 3 months. Baseline FFI total and subscale scores were comparable between groups. At 3 months, the SOPI group demonstrated greater improvements than the PPI group in FFI total scores (mean difference 12.2, 95%CI: 5.2-19.3, P =.002), FFI pain scores (15.0, 95%CI: 5.9-24.1, P =.006), FFI disability scores (13.5, 95%CI: 5.2-21.8, P =.004), and FFI activity limitation scores (4.9, 95%CI: 0.5-9.3, P =.015), with differences exceeding reported minimal clinically important differences. Our preliminary data suggest that SCF-specific optimization of prefabricated insoles may improve pain and function over three months compared to unmodified insoles. However, these findings are inconclusive due to the underpowered sample size and should be interpreted as hypothesis-generating. Confirmation in larger, adequately powered studies with longer follow-up is required.