Optimization of a Patient-Specific External Fixation Device for Lower Limb Injuries

Abstract

The use of external fixation devices is considered a valuable approach for the treatment of bone fractures, providing proper alignment to fractured fragments and maintaining fracture stability during the healing process. The need for external fixation devices has increased due to an aging population and increased trauma incidents. The design and fabrication of external fixations are major challenges since the shape and size of the defect vary, as well as the geometry of the human limb. This requires fully personalized external fixators to improve its fit and functionality. This paper presents a methodology to design personalized lightweight external fixator devices for additive manufacturing. This methodology comprises data acquisition, Computer tomography (CT) imaging analysis and processing, Computer Aided Design (CAD) modelling and two methods (imposed predefined patterns and topology optimization) to reduce the weight of the device. Finite element analysis with full factorial design of experiments were used to determine the optimal combination of designs (topology optimization and predefined patterns), materials (polylactic acid, acrylonitrile butadiene styrene, and polyamide) and thickness (3, 4, 5 and 6 mm) to maximize the strength and stiffness of the fixator, while minimizing its weight. The optimal parameters were found to correspond to an external fixator device optimized by topology optimization, made in polylactic acid with 4 mm thickness.

Bioinspired design proposal for a new external bone fixator device

“…It consists of the creation of a dimensional object through the injection of material filament to form overlapping layers, whose shape is based on a digital 3D model [70]. Similar to the IEF, the new device fabrication also depends on the variation of the shape and size of the fracture [2]. Because of that, the additive manufacturing method is interesting once it is ideal to produce personalized medical devices and implants [2,71].…”

“…Over the years, the increase in life expectancy and the high incidence of bone fractures have shown that it remains a serious and common life event [1][2][3]. Therefore, the use of fixation treatment is still highly important [4].…”

“…Therefore, the use of fixation treatment is still highly important [4]. In general, the treatments of fractures are divided into conservative and operative approaches [2,5]. The surgical treatment brings fewer disabilities and pain after one year [6], lower rates of recurrence [7] and lower rates of nonunion that require reintervention [8] when compared with the conservative techniques.…”

“…The concept of external fixation devices is the insertion of pins/wires into the tissue and bone. These pins/wires are connected to the external apparatus that will give support in order to keep the bone fractures in place [2]. The devices that perform external fixation are the Ilizarov External Fixator (IEF), the standard uniplanar fixator and the hybrid fixator [5].…”

Additive manufacturing for prostheses development: state of the art

“…Prostheses are evaluated based on their functionality in various activities (walking, running, swimming, etc.) and their mechanical parameters (strength, materials, structure, geometry, weight or complexity) (Alqahtani et al , 2021; Goldstein et al , 2020; Guo Dong et al , 2020; Jarl et al , 2012; Stenvall et al , 2020). According to the evaluation, some participants in a recreational pool scenario found an additively manufactured lower limb prosthesis acceptable and straightforward (Goldstein et al , 2020).…”