Biomechanical stability of five fixation techniques for pediatric distal radius metaphyseal-diaphyseal junction...

Pediatric distal radius metaphyseal-diaphyseal junction (DRMDJ) fractures represent a distinct and inherently unstable fracture pattern that frequently necessitates surgical intervention. The variability in current clinical management strategies, and there remains a paucity of biomechanical evidence to guide optimal fixation selection. A computed tomography (CT) image of the forearm were acquired from a 10-year-old male volunteer, and digital imaging and communications in medicine (DICOM) data were extracted for three-dimensional model reconstruction. A virtual fracture was simulated at the DRMDJ using computer-aided modeling technique. Five distinct fixation constructs were evaluated: locking plate, three crossed kirschner wires (K-wires), antegrade elastic stable intramedullary nailing (ESIN-A), retrograde elastic stable intramedullary nailing (ESIN-R), and external fixation. Finite element analysis (FEA) was performed to assess and compare the biomechanical performance of these fixation constructs under seven wrist loading conditions: flexion, extension, pronation, supination, ulnar deviation, radial deviation, and axial loading. Quantitative assessments were conducted using key biomechanical parameters, including peak displacement at the fracture site, peak Von Mises stress at the fracture site and peak Von Mises stress at the fixation constructs. The comparison was based on the locking plate as the reference. Regarding the peak overall displacement at fracture sites, the crossed K-wires demonstrated good stability across all loading conditions. Both ESIN-A and ESIN-R showed favorable performance only under radial deviation and axial loading, with significant displacement increase under rotational loads. The external fixation outperformed the locking plate in pronation loading condition, while remaining comparable to locking plate in other loading conditions, maintaining overall stability. Regarding peak Von Mises stress at the fracture site, the crossed K-wires demonstrated good performance under axial loading, pronation, and radial deviation conditions, while showing poor results under other conditions. Both ESIN-A and ESIN-R exhibited poor stability across all test conditions. The external fixation performed well under pronation, supination, ulnar deviation, axial loading, and radial deviation conditions, but showed inadequate performance during flexion and extension maneuvers. Regarding peak Von Mises stress at the fixation constructs, the crossed K-wires demonstrated good stress peak performance under pronation conditions but showed poor results under other postural conditions. Both ESIN-A and ESIN-R exhibited consistently poor stress peak performance across all test conditions. The external fixation demonstrated optimal stress peak performance under extension, pronation, supination, and axial loading conditions, outperforming steel plates in pronation and supination conditions while showing inferior performance in flexion, ulnar deviation, and radial deviation conditions. In the FEA model of pediatric DRMDJ fracture, the external fixation and locking plate constructs demonstrated comparable, relatively lower fracture-site displacement under the idealized loading conditions applied. The crossed K-wire construct-modeled in an optimal configuration that may be technically challenging to achieve clinically-showed intermediate biomechanical indices. ESIN-A and ESIN-R constructs exhibited greater displacement, which is consistent with the intentionally low structural stiffness inherent to elastic fixation and does not necessarily indicate clinical instability. These computational findings alone do not directly dictate clinical decision-making; while the results suggest that, from a purely structural perspective, constructs with lower inherent stiffness might theoretically require additional external support, such extrapolation remains speculative. Importantly, FEA cannot capture critical clinical factors, including pin-site infection, soft-tissue irritation, patient tolerance, and the dynamic elastic stabilization afforded by ESIN. Therefore, the present results should be regarded as comparative and hypothesis-generating, and their clinical translation requires validation through well-designed, multicenter prospective clinical studies.