## 1 Introduction  
Finding cost-effective and equitable healthcare solutions is a fundamental objective of sustainable medicine, and Additive Manufacturing (AM) technology (also colloquially named 3D Printing) can contribute to this goal by enabling the production of personalized medical devices at lower costs while also facilitating the decentralized manufacturing across different regions [1]. The external fixators (EFs) are among the medical devices for which cost remains an important concern, particularly in low-income regions [2], while their availability in conflict zones and disaster relief settings further underlines the need for more accessible and adaptable solutions [3, 4, 5]. EFs are used for stabilizing fractures and treating congenital deformities, malformations, dislocations, contractures, and dysplasia [6]. Their mechanical performance depends on the EF-bone stiffness, healing stage, and load-bearing demands. Excessive stress or micro-strains can delay the healing by promoting fibrous tissue over stable callus formation [7; 8; 9; 10; 11], while excessive rigidity may inhibit interfragmentary movements (IFMs), critical for early callus development, especially for fracture gaps over 1 mm [11]. Compared to internal fixation, EFs allow for a closed fracture reduction with minimal vascular disruption and enable real-time monitoring via imaging, making MRI compatibility an important design factor [7; 12]. However, EFs also pose challenges, including their structural complexity, need for surgical expertise, and risks like pin loosening, mechanical failure, delayed union, vascular injury, and infection at anchoring sites, these requiring careful monitoring [7]. As mentioned, cost is another major challenge, with temporary fixators around $5892 per frame, and definitive fixation around $6013 [13]. Given the high incidence of traumatic injuries in low- and middle-income countries, more affordable alternatives are required. [PERSON] et al. [4] highlighted the importance of locally producing EFs, and, in this context, AM can be a promising alternative. By supporting decentralized manufacturing, AM aligns with the 3D-Printing Point-of-Care concept [14], which enhances EF availability in resource-limited settings, war zones, and even outer space. The use of 3D-printed EF components, especially rings and clamps, is still emerging, with limited studies available in the literature. A review by [PERSON] et al. [15] identified only nine studies, four of which addressed tibial fractures. Designs included circumferential frames such as the Q-fixator by [PERSON] et al. [16] and [PERSON] et al. 's contouring shell [17], and unilateral bars for distal radius fractures [18]. Due to the low stiffness of materials like PLA, ABS, and Onyx, these studies often propose bulkier geometries for compensation. Some research focused on 3D-printed clamps, such as [PERSON] et al. [19], who proposed an Onyx clamp tested per ASTM F1541 [20], showing performance comparable to commercial versions. Building on these efforts, this study proposes a cost-effective alternative to conventional EF rings using 3D-printed PLA-CF. The focus is on hybrid fixators, less studied than linear or Iliazorov EF's types [9]. A finite element analysis (FEA) evaluates the mechanical feasibility of this solution, aiming for a balance between strength and weight. FEA was widely applied in EF studies to optimize the design parameters and assess the mechanical stability under different loading conditions, including axial compression, bending, and torsion [21; 22; 23; 24; 25; 26]. [PERSON] et al. examined Iliazorov, unilateral, and hybrid fixators for femoral fractures, showing that, while unilateral fixators provide greater stability, they may not offer adequate support for complex fractures [21]. [PERSON] et al. showed that a double-cross tibial EF configuration offers superior biomechanical stability [11], while [PERSON] et al. found that the Delta fixator provides better stability for pinon fractures [22].