An investigation into the effects of metatarsal padded insoles in the management of painful plantar corns

Background
The management of painful plantar corns form a key aspect of routine podiatric care. Existing research focuses on treatments to remove the corn rather than interventions that address the causative factors responsible for its development. Treatments aimed at removing corn tissue, including standard treatment of sharp scalpel debridement and enucleation, are associated with short lived outcomes for patients necessitating repetitive podiatric intervention. Since pressure is regarded as an important factor in the development of corns, the literature focuses around implementation of pressure-relieving strategies alongside corn removal treatments, to improve patient outcomes by preventing recurrence. Metatarsal padded insoles are commonly used by podiatrists to reduce pressure in the management of corns, yet there is currently no research available supporting this clinical practice. This research aimed to address this gap in the literature by investigating a currently ambiguous issue in routine podiatric practice: do metatarsal aperture padded insoles, in conjunction with debridement, improve patient outcomes significantly more than sharp debridement alone in the management of corns?

Methods
A pragmatic, parallel group, randomised controlled pilot trial was conducted, whereby 30 participants were allocated to receive either sharp scalpel debridement alone (control group, n = 15) or sharp scalpel debridement alongside a metatarsal padded insole (intervention group, n = 15). The primary outcomes measured were the presence of an
improved plantar corn at six months following treatment and time-to-resolution. Secondary outcomes were; pain, foot disability, and health-related quality of life.

Prior to conducting a proof of concept pilot study, several preliminary investigations were undertaken to determine the type of forefoot padded insole to be tested, which involved: extensive analysis of the research regarding forefoot pads, a survey to investigate current practice, compressional stiffness testing of materials, patients’ perspective of metatarsal padded insoles, and pressure analysis.

Results
The preliminary investigations determined that the preferable insole for reducing pressure at the forefoot was a metatarsal pad made from a medium-density polyurethane material. Further to this, an aperture at the site of the corn should provide greater reductions in pressure.

Results of the pilot study showed that a larger-scale study is feasible with recommendations, including; recruitment strategies, efficacy of expanding the study over multiple sites using multiple researchers, and extending the evaluation from six to 12 months. At six months 29% (4/14) of the corns had completely resolved in the control group compared with 13% (2/16) in the intervention group (p = 0.793). Partial resolution (a greater than 50% reduction in baseline area measurement) occurred in 50% of the participants in both control (n = 7) and intervention (n = 8) groups. Time-to-resolution was greater in the intervention group than those in the control (χ2(1) = 0.325; p = 0.569). The intervention group showed a greater reduction in mean pain of 23 mm, in comparison to 17 mm in the
control, when compared to baseline mean scores (62 mm (SD 21 mm), 47 mm (SD 30 mm), respectively).

Conclusion
These preliminary investigations have emphasised that a larger-scale study evaluating metatarsal padded insoles is feasible and warranted to determine if this common intervention is effective in managing painful plantar corns. Findings from the pilot suggest that there is no significant difference in resolution rates and time-to-resolution between those receiving debridement and insole therapy to those receiving debridement alone. Conclusions should not be drawn from these findings as considerable imbalances between participants at baseline were found, which could have substantially impacted on the effectiveness of the treatment. Future research should continue to investigate treatments that address the cause of corn development, rather than simply the removal of the lesion to improve outcomes for patients.