# Evaluation of Patients with Hallux Valgus Wearing a 3D-Printed Orthosis during Walking
## 4 Discussion  
An orthosis, which is an insole with toe separators, and night splints are commonly used for painful foot disorders. Previous evaluations of different conservative treatments have focused on the HV angle and symptom improvement, and the effects of using orthoses or insoles on pain reduction have been reported [3]. In addition, a few studies have assessed the effectiveness of orthotic management in controlling valgus deformity [2,4]. [PERSON] et al. [5] used toe separators incorporating an insole or night splint but reported unfavourable outcomes for deformity correction. In addition, a Cochrane review conducted on conservative interventions indicated that neither a foot orthosis nor a night splint is more beneficial than no treatment [12]. These results indicate that the effectiveness of foot orthoses in preventing or reducing the HV angle varies. In the development of a 3D-printed orthosis, the hallmark is maintained in a relatively dorsiflexed position by using the orthosis from the middle to terminal stance. This hallux position is attributable to the orthosis with inherent thickness. In 3D printing, the orthosis thickness was controlled to 2.5 mm. The sagittal motion pattern observed in this study agrees with that observed previously [13]. An increased dorsiflexion movement is probably related to the first-ray hypermobility in the pre-swing phase. The dorsiflexion range is restricted by the loop design of the HV orthosis; however, the degree of limitation did not significantly interfere with push-off. The kinetic study showed consistent temporal patterns of horizontal and vertical components, which correspond to those obtained in a previous study conducted on GRF [14]. The participants in this study did not find any change in the peak reaction force after wearing the orthosis. According to sagittal motion analysis, use of the orthosis does not interfere with the initial loading response or subsequent push-off throughout the stance phase of gait. This study investigated the application of a hallux orthosis to control valgus deformity. An immediate reduction in the abduction angle was noted during static standing. The 3D-printed orthosis applied the bending moment using a strap to ensure static angle correction and could instantly prevent excessive valgus motion. In addition, regular night splints are commonly used in a static manner with no dynamic correction. However, the wearers of such night splints often experience discomfort due to the rigidity of the material. Thus, this study applied a soft material to print an HV orthosis, which allows the user to walk normally while retaining HV correction. However, changing the 3D printing material can yield different HV correction effects for users: a stiffer material offers better correction effects but at the expense of user comfort. Therefore, identification of an appropriate 3D printing material is necessary in the future. The 3D-printed orthosis developed in this study has some advantages over existing orthotic devices. Regarding the cost, the hallux orthosis weighs approximately 23-40 g, and the material costs less than US$3. If the patient wants to fabricate the 3D printed orthosis, the manufacturing cost is about US$6. However, the price of prefabricated orthoses ranged from US$10 to US$40 in the Taiwanese market. Therefore, the 3D printed orthosis is inexpensive. Regarding its function, the patients always complain that prefabricated orthosis is too soft to correct the HV angle or too hard to use for walking. As a result, the semi-rigid material to fabricate HV orthosis is very important. In the experiment, this 3D printed orthosis reached a goal of correcting the HV angle and enabling walking smoothly. The use of a soft and resilient material can make the device durable for continuous use and is potentially inexpensive compared with currently available custom-made orthoses. Regarding the study, there were some limitations that need to be noted:  
1. The aim of this research was to verify the immediate effects of using 3D-printed hallux orthoses.