Low cost 3D printed clamps for external fixator for developing countries: a biomechanical study

Abstract

Background External fixation is a mainstream limb reconstruction technique, most often used after a traumatic injury. Due to the high rates of trauma in developing countries, external fixation devices are often utilized for immediate fracture stabilization and soft tissue repair. Proper external fixation treatment too often still fails to be adopted in these regions due to the high cost and trauma complexity. A novel, inexpensive, unilateral fixator was constructed using 3D printed clamps and other readily available supporting components. ASTM standard F1541 tests were used to assess the biomechanical properties of this novel external fixator. Methods Applicable sections of ASTM standard F1541 were used to determine the biomechanical properties of the novel external fixator. 3D printed clamps modeled using SolidWorks and printed with chopped carbon fibers using a fuse deposition modeling (FDM) based 3D printer by Markforged (Boston, MA) were used. This study included 3 different testing configurations: axial compression, anterior-posterior (AP) bending, and medial-lateral (ML) bending. Using the novel unilateral fixator with 3D printed clamps previously sterilized by autoclave, an input load was applied at a rate of 20 N/s, starting at 0 N via a hydraulic MTS tester Model 359. Force and deformation data were collected at a sampling rate of 30 Hz. There was a load limit of 750 N, or until there was a maximum vertical deformation of 6 mm. Also, 4 key dimensions of the 3D printed clamps were measured pre and post autoclave: diameter, width, height and length. Results The novel external fixator had axial compression, AP and ML bending rigidities of 246.12 N/mm (σ = 8.87 N/mm), 35.98 N/mm (σ = 2.11 N/mm) and 39.60 N/mm (σ =2.60 N/mm), respectively. The 3D printed clamps shrunk unproportionally due to the autoclaving process, with the diameter, width, height and length dimensions shrinking by 2.6%, 0.2%, 1.7% and 0.3%, respectively. Conclusion Overall, the biomechanical properties of the novel fixator with 3D printed clamps assessed in this study were comparable to external fixators that are currently being used in clinical settings. While the biomechanics were comparable, the low cost and readily available components of this design meets the need for low cost external fixators in developing countries that current clinical options could not satisfy. However, further verification and validation routines to determine efficacy and safety must be conducted before this novel fixator can be clinically deployed. Also, the material composition allowed for the clamps to maintain the appropriate shape with minimal dimensional shrinkage that can be accounted for in clamp design.

Manufacturing a First Upper Molar Dental Forceps Using Continuous Fiber Reinforcement (CFR) Additive Manufacturing Technology with Carbon-Reinforced Polyamide

“…Moreover, it was highlighted that CFR technology can provide sturdier and more force-resistant products compared to FFF technology. This is consistent with a previous study, where an external fixator was fabricated using this technology and the Onyx material [ 22 ]. In the case of flexural fatigue tests, 30-mm deflection can be considered to be a limit, since a significant decrease in tensile strength was measured above this value, as well as a change from “V”-shaped fracture lines to a straight pattern.…”

“…Despite the mechanical characterization being carried out in detail, in the future, it will be extremely important to evaluate the potential disinfection protocols that can be used for medical instruments fabricated with 3D printers without causing major change to their material properties. This aspect is crucial in terms of reusability, and precise, critical evaluations are still needed in terms of the sterilization of these medical instruments [ 22 , 31 ]. Furthermore, cost-effectivity analysis should be considered; however, the availability of 3D printing technologies is continuously increasing [ 32 ].…”

An engineering review of external fixators

“…Landaeta et al. [106] developed a novel linear fixator, where the clamps were 3D printed using a composite material containing nylon with chopped carbon fibre randomly distributed in the filament. During the biomechanical testing, this clamp arrangement was found to provide sufficient rigidity with minimum shrinkage.…”

Use of external fixators in developing countries: a short socioeconomic analysis

“…The main reasons for a higher number of road traffic accidents are poorly maintained road systems, overcrowding, and the number of people travelling in each vehicle [ 1 ]. Gun violence is another reason for fracture in developing countries [ 8 ]. The common causes of fractures among children in developing countries are poor local laws, poor adult supervision of young children, poor quality and lack of well-designed public recreational and sports facilities [ 9 ].…”

“…Increasing incidence and complexity of fractures, limited health care facilities such as inadequate operating theatre facilities, lack of equipment, lack of expertise, long distances to a healthcare facility and patient or family ignorance are barriers to effective management of fracture in developing countries [ 21 ]. Over 50% of the world’s traumatic injuries occur in low and middle-income countries [ 8 ]. External fixation techniques are widely utilised for fracture stabilisation in developing countries due to increasing trauma accidents [ 8 ].…”