The Application of 3d Printing Technology in Fabricating Foot Orthosis for Hallux Valgus

Hallux valgus (HV) is a foot disorder manifesting by lateral deviation of the great toe and medial deviation of the first metatarsal. HV not only affects foot appearance, but also causes functional disability, including foot pain, impaired gait patterns, balance disorders, which further lead to easily falling and impaired quality of life. Among all the etiologies of hallux valgus, inadequate biomechanics loading caused by flexible flat foot plays the main role. Patients generally receive conservative treatments when having a mild (＜30°) HV angle, including night splints, foot exercises, and orthotic application. However, the reported effect of these interventions were not satisfying. The technique of orthotic fabrication has evolved from handmade to 3D printing which allows the orthosis to be more individualized and accurately aligned with the foot shape.Botulinum toxin type A has been widely used in relieving muscle spasm and muscle imbalance and had been reported to be effective in improving HV angle. In the first year, we aim to recruit fifty HV patients and use the diagnosis criteria of first metatarsophalangeal angle greater than 15 degrees on AP weight-bearing foot radiograph. Patients are randomly divided into two groups. Traditional handmade total contact with movable toe separator insole will be applied in control group for 3 months. Customized 3D printing total contact insole with fixed toe separator will be applied in experimental group for 3 months. The outcome measurements include Visual Analogue Scale(VAS), Foot Functional Index(FFI), and first metatarsophalangeal angle obtained from AP weight-bearing foot radiograph. In the second year, we will recruit fifty patients with not only HV but also flexible flat foot and randomly divided into two groups. For the diagnosis of flexible flat foot, patients were first screened by the same physician according to following clinical observation: the medial longitudinal arch of the foot can be well observed when the patients sit on the examination table without weight bearing, but collapsed while standing. Static arch index was then calculated. Arch indices equal or greater than 0.26 were classified as low-arched. Control group receive customized 3D printing total contact insole with fixed toe separator, while experimental group receive customized 3D printing total contact insole with fixed toe separator and additional forefoot medial wedge in five degrees inclination for flexible flat foot condition. The outcome measurements include assessments in the first year with the addition of plantar pressure measurement with Pedar in-shoe system and gait analysis(Vicon MX motion system corp,Oxford,UK). In the third year, we will recruit fifty patients with HV and randomly divide into two groups. Experimental group receive Botulinum toxin type A(BTX-A) injection into the oblique head and transverse head of the adductor hallucis muscle, the flexor hallucis brevis muscle, and the extensor hallucis longus muscleunder dual guide of ultrasound and electrical stimulator. Control group receive normal saline injection in above muscles. Both groups receive customized 3D printing total contact insole with fixed toe separator for 3 months. The outcome measurements include all assessments in the second year.

Project ID:PC10707-0073
External Project ID:MOST107-2314-B182-011