## 4 Discussion  
In this study, a subject-specific 3D FEA foot model with CMI assigned with different materials and their combinations was developed to investigate the effects of materials on peak contact pressure in a diabetic foot with neuropathy. FEA results revealed that the peak contact pressure was reduced with CMI fabricated from all materials used in this study compared to without CMI. Specifically, using CMI with soft material (EVA) tends to reduce the peak contact pressure effectively compared with CMI with stiffer material (TPU). The higher regional contact pressure shifted to the midfoot and the peak contact pressure was reduced from hindfoot and forefoot with CMI. There was a notable reduction of frictional stress with softer material under the first metatarsal head compared with stiffer material. The predicted results from FEA were validated with the experimental study using the Pedar(r) system by comparing the peak contact pressure during balanced standing with CMI fabricated from EVA. In this comparison, the FEA results were in agreement with the experimental results. The present FEA study predicted that all the CMIs showed a reduction of peak contact pressure compared to without CMI. The CMI fabricated either from a single soft material or a combination of softer and stiffer materials resulted in a reduction of peak contact pressure compared to without CMI. Similar reduction of peak contact pressure was found while using different cushioning materials and conformity  
Figure 5: (**A**) The finite element analysis (FEA) results for the maximum frictional stress obtained from different CMI materials varied from soft to hard compared to without CMI, and (**B**) the comparison of frictional stress obtained from FEA in the case of without and with CMI fabricated from EVA using a single layer of softer material. compared with the flat insole [42]. Other studies reported a 30% to 40% reduction of peak contact pressure using CMI [43; 44]. The current FE model indicates increased peak contact pressure at the forefoot and hindfoot without CMI. However, the ratio of peak contact pressure between forefoot and hindfoot was less than two showing lower severity of ulceration (Table 3). Researchers found that a severe neuropathic group had a FF/HF ratio higher than two during gait; however, mild to moderate neuropathic groups still had this ratio of less than two [45]. The FF/HF ratio was reduced from 1.07 to 0.87 with CMI fabricated from Multiform, Plastazote(r) and microcellular rubber compared to without CMI during gait [16; 17]. A similar reduction of contact pressure ratio was found in this study during balanced standing with CMI fabricated from EVA. CMIs are strongly dependent on the mechanical characteristics of the material used to provide cushioning [46; 47]. The peak plantar pressure reduces with a customized insole, especially from the forefoot compared with a flat insole [48]. Based on our results, the CMI with a softer material was able to redistribute plantar pressure better as compared to stiffer materials and their combinations. Nevertheless, the addition of a base layer of stiffer material has a minimal effect on plantar pressure distribution. The stiffer top layer tends to increase the peak contact pressure compared with the soft top layer material. Similar results were found in our study using softer CMI, as other studies found it was effective in reducing the plantar pressure up to 53% compared to the painful forefoot region of the foot [49; 50]. Therefore, CMI with a softer material can be prescribed to people with prolonged standing activities. However, soft materials are not prescribed in a clinical setup as various offloading structures such as metatarsal pads, metatarsal bars or medial arch support because they cannot withstand the repetitive subject's load during daily living activities. In addition, clinicians would most probably design the CMI with a multi-density material combination to achieve clinical goals from the subjects with different foot complications.