Background: O’Driscoll type III fractures of the ulnar coronoid process present significant challenges in orthopedic surgery, requiring precise fixation techniques to achieve optimal recovery. Despite considerable scientific interest, the impact of different fixation methods on the restoration of normal bone structure between the ulna and coronoid remains insufficiently understood. There is limited knowledge regarding the biomechanical effects of Kirschner wires and screws in providing adequate stability and stress distribution under elbow loading conditions. Moreover, beyond the choice of fixation device, it is essential to determine the optimal application parameters, including orientation, quantity and positioning, to maximize mechanical performance and clinical outcomes. This finite element analysis aims to evaluate three distinct fracture fixation strategies to identify the most effective approach for clinical practice. Materials & Methods: CT images of a left elbow, including the distal humerus and proximal ulna, were imported for a semi-automatic segmentation process to generate corresponding 3D bone geometries. Cortical and trabecular regions were identified, and cartilage layers were modeled as offsets of the bone surfaces. Material properties and friction coefficients were assigned based on literature data. Four configurations were analyzed: a native (intact) control condition and a coronoid fracture treated with either a single K-wire (SW), double K-wire (DW), or a Screw. To simulate a worst-case scenario in term of stability, the radius was excluded from the model. The elbow was positioned at 30° flexion, and a 1 kN proximo-distal load was applied to the humerus along with an internal 3° humeral rotation. These boundary conditions were designed to replicate joint loading during arm positioning in a forward fall. Stress distribution, micro-motions, and micro-rotations were calculated to compare the mechanical behavior of the different fixation strategies. Results: The results highlight differences between the SW technique and the other two configurations (DW and Screw). The SW technique exhibits greater displacements and higher stress peaks due to the material properties and the limited fixation provided by only one wire, resulting in lower stability of the coronoid fracture fragment. In the DW configuration, stability is enhanced both translationally and rotationally due to the additional wire, a stabilization effect also observed in the Screw configuration. Regarding stress distribution, the DW technique demonstrates inferior performance compared to the Screw technique, primarily due to differences in material mechanical properties. The Screw configuration ensures a more homogeneous stress distribution, fully loading the coronoid fracture fragment to facilitate osteosynthesis and generate a stress pattern more closely resembling physiological conditions. Conclusion: It was observed that DW, due to the presence of two fixation elements, as well as the Screw, provide greater resistance to mobilization, which could compromise the initial stability of bone synthesis. However, based on the predefined evaluation criteria - stress distribution, micro-motions, and micro-rotations - the technique involving a Screw ranks as the most effective. Despite exhibiting slightly lower resistance to movement compared to DW (remaining within the safe limit), this technique more efficiently distributes stress, thereby facilitating physiological post-operative osteosynthesis processes and ultimately promoting improved patient recovery.
Contesto: Le fratture di tipo III del processo coronoideo dell’ulna, secondo O’Driscoll, rappresentano una sfida in ortopedia, richiedendo fissazioni precise per garantire il recupero. L’impatto biomeccanico di fili di Kirschner e viti sulla stabilità e distribuzione degli sforzi è ancora poco compreso. Oltre al tipo di dispositivo, anche parametri come orientamento, numero e posizionamento sono cruciali per ottimizzare i risultati. Questo studio agli elementi finiti valuta tre strategie di fissazione per identificare l’approccio più efficace. Materiali e Metodi: Sono state segmentate immagini TC di un gomito sinistro per generare modelli 3D dell’omero distale e dell’ulna prossimale. Corticale, trabecolare e cartilagine sono stati modellati separatamente, con proprietà materiali derivate da letteratura. Sono state analizzate quattro configurazioni: gomito intatto (controllo), frattura con un filo di Kirschner (SW), due fili (DW) e una vite (Screw). Il radio è stato escluso per simulare condizioni sfavorevoli. Il carico articolare è stato simulato con una flessione di 30°, un carico di 1 kN e una rotazione interna di 3°. Sono stati analizzati stress, micromovimenti e microrotazioni. Risultati: La configurazione SW ha mostrato maggiori spostamenti e picchi di stress, indicando minore stabilità. Le configurazioni DW e Screw hanno garantito migliore stabilità traslazionale e rotazionale. Tuttavia, la vite ha fornito una distribuzione degli sforzi più omogenea e fisiologica, favorendo l’osteosintesi rispetto alla DW, che ha mostrato prestazioni inferiori per le proprietà del materiale. Conclusione: DW e Screw garantiscono maggiore stabilità rispetto a SW. Tuttavia, la vite risulta la tecnica più efficace secondo i criteri biomeccanici considerati, offrendo una migliore distribuzione degli sforzi e supportando un recupero post-operatorio più efficiente.
Biomechanical Evaluation of Different Fixation Strategies for O’Driscoll Type III Coronoid Fractures: a Finite Element Study.
PITUCCI, DAVIDE
2024/2025
Abstract
Background: O’Driscoll type III fractures of the ulnar coronoid process present significant challenges in orthopedic surgery, requiring precise fixation techniques to achieve optimal recovery. Despite considerable scientific interest, the impact of different fixation methods on the restoration of normal bone structure between the ulna and coronoid remains insufficiently understood. There is limited knowledge regarding the biomechanical effects of Kirschner wires and screws in providing adequate stability and stress distribution under elbow loading conditions. Moreover, beyond the choice of fixation device, it is essential to determine the optimal application parameters, including orientation, quantity and positioning, to maximize mechanical performance and clinical outcomes. This finite element analysis aims to evaluate three distinct fracture fixation strategies to identify the most effective approach for clinical practice. Materials & Methods: CT images of a left elbow, including the distal humerus and proximal ulna, were imported for a semi-automatic segmentation process to generate corresponding 3D bone geometries. Cortical and trabecular regions were identified, and cartilage layers were modeled as offsets of the bone surfaces. Material properties and friction coefficients were assigned based on literature data. Four configurations were analyzed: a native (intact) control condition and a coronoid fracture treated with either a single K-wire (SW), double K-wire (DW), or a Screw. To simulate a worst-case scenario in term of stability, the radius was excluded from the model. The elbow was positioned at 30° flexion, and a 1 kN proximo-distal load was applied to the humerus along with an internal 3° humeral rotation. These boundary conditions were designed to replicate joint loading during arm positioning in a forward fall. Stress distribution, micro-motions, and micro-rotations were calculated to compare the mechanical behavior of the different fixation strategies. Results: The results highlight differences between the SW technique and the other two configurations (DW and Screw). The SW technique exhibits greater displacements and higher stress peaks due to the material properties and the limited fixation provided by only one wire, resulting in lower stability of the coronoid fracture fragment. In the DW configuration, stability is enhanced both translationally and rotationally due to the additional wire, a stabilization effect also observed in the Screw configuration. Regarding stress distribution, the DW technique demonstrates inferior performance compared to the Screw technique, primarily due to differences in material mechanical properties. The Screw configuration ensures a more homogeneous stress distribution, fully loading the coronoid fracture fragment to facilitate osteosynthesis and generate a stress pattern more closely resembling physiological conditions. Conclusion: It was observed that DW, due to the presence of two fixation elements, as well as the Screw, provide greater resistance to mobilization, which could compromise the initial stability of bone synthesis. However, based on the predefined evaluation criteria - stress distribution, micro-motions, and micro-rotations - the technique involving a Screw ranks as the most effective. Despite exhibiting slightly lower resistance to movement compared to DW (remaining within the safe limit), this technique more efficiently distributes stress, thereby facilitating physiological post-operative osteosynthesis processes and ultimately promoting improved patient recovery.| File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12075/22700