Background: The repetitive peak contact pressure and frictional stresses under bony prominences during gait cause callus formation, that is an initial stage of ulcer formation in a diabetic foot with neuropathy. Custom-made insole (CMI) is mostly used to offload the abnormal peak contact pressure. However, the effectiveness of CMI fabricated from different material combination is rarely discussed especially for diabetic foot with ulceration. Finite element analysis can provide an efficient evaluation of different insoles combination for diabetic foot with ulceration.
Objective: The aim of this study was to predict the peak plantar pressure at the ulcerated site and effectively offload with CMI in diabetic foot with ulceration.
Materials and Methods: A subject-specific 3D foot model was reconstructed with the flat insole and CMI. The top surface of tibia and fibula were fixed, and a displacement of 3mm was exerted from the ground along with the upward Achilles tendon force. The peak contact pressure was compared with the foot without insole from four regions of the foot.
Results: The peak contact pressure increased 75.39% with ulceration compared to without ulceration and without any insole at the medial forefoot. However, this peak contact pressure reduced 51.72% with flat insole compared to without any insole. The trend of reduction was 64.98% with CMI compared to the flat insole. Moreover, the material combinations to fabricate CMI changed the plantar pressure distribution in diabetic foot with ulceration.
Conclusion: CMI effectively reduced and redistribute abnormal peak plantar pressure in diabetic foot with ulceration. Diabetic foot ulceration can be prevented from further complication with selection of appropriate insole and material to offload abnormal peak plantar pressure. Further studies are required to compared different feet with different designs of CMI.