title: Finite element analysis of three commonly used external fixation devices for treating Type III pilon fractures.
abstract: Pilon fractures are commonly caused by high energy trauma and can result in long-term immobilization of patients. The use of an external fixator i.e. the (1) Delta, (2) Mitkovic or (3) Unilateral frame for treating type III pilon fractures is generally recommended by many experts owing to the stability provided by these constructs. This allows this type of fracture to heal quickly whilst permitting early mobilization. However, the stability of one fixator over the other has not been previously demonstrated. This study was conducted to determine the biomechanical stability of these external fixators in type III pilon fractures using finite element modelling. Three-dimensional models of the tibia, fibula, talus, calcaneus, navicular, cuboid, three cuneiforms and five metatarsal bones were reconstructed from previously obtained CT datasets. Bones were assigned with isotropic material properties, while the cartilage was assigned as hyperelastic springs with Mooney-Rivlin properties. Axial loads of 350 N and 70 N were applied at the tibia to simulate the stance and the swing phase of a gait cycle. To prevent rigid body motion, the calcaneus and metatarsals were fixed distally in all degrees of freedom. The results indicate that the model with the Delta frame produced the lowest relative micromovement (0.03 mm) compared to the Mitkovic (0.05 mm) and Unilateral (0.42 mm) fixators during the stance phase. The highest stress concentrations were found at the pin of the Unilateral external fixator (509.2 MPa) compared to the Mitkovic (286.0 MPa) and the Delta (266.7 MPa) frames. In conclusion, the Delta external fixator was found to be the most stable external fixator for treating type III pilon fractures.
authors.affiliation: Medical Devices and Technology Group (MEDITEG), Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, Malaysia. Electronic address: mhanif008@gmail.com.
authors.forename: Muhammad Hanif
authors.initials: MH
authors.lastname: Ramlee
authors.affiliation: Medical Devices and Technology Group (MEDITEG), Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, Malaysia. Electronic address: rafiq@biomedical.utm.my.
authors.forename: Mohammed Rafiq Abdul
authors.initials: MR
authors.lastname: Kadir
authors.affiliation: Tissue Engineering Group (TEG), National Orthopaedic Centre of Excellence in Research and Learning (NOCERAL), Department of Orthopaedic Surgery, Faculty ofMedicine, University of Malaya, 50603 Lembah Pantai, Kuala Lumpur, Malaysia. Electronic address: mrmurali08@gmail.com.
authors.forename: Malliga Raman
authors.initials: MR
authors.lastname: Murali
authors.affiliation: Tissue Engineering Group (TEG), National Orthopaedic Centre of Excellence in Research and Learning (NOCERAL), Department of Orthopaedic Surgery, Faculty ofMedicine, University of Malaya, 50603 Lembah Pantai, Kuala Lumpur, Malaysia. Electronic address: tkzrea@um.edu.my.
authors.forename: Tunku
authors.initials: T
authors.lastname: Kamarul
mesh_terms: D001696:Biomechanical Phenomena; D016267:External Fixators; D020342:Finite Element Analysis; D006801:Humans; D016013:Likelihood Functions; D055595:Mechanical Phenomena; D009068:Movement; D013314:Stress, Mechanical; D013977:Tibia / Q000000981:diagnostic imaging / Q000502:physiology / Q000601:surgery; D013978:Tibial Fractures / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D014057:Tomography, X-Ray Computed
keywords: Biomechanics; External fixator; Finite element; Micromovement; Pilon fractures; Stability