| Objective To analyze and compare the difference in mechanical stability between external fixation with bone cement rod and crossed Kirschner wires, and to provide a theoretical basis for surgical treatment of the fifth metacarpal neck fracture, a three-dimensional finite element numerical simulation was used.Methods 3D CT image data of the wrist joint of a healthy volunteer were selected. Firstly, Mimics Research 21.0 and Geomagic Studio 2021 software were used to process the 3D graphic data. On this basis, Solidworks 2020 software was applied to construct the external fixation scaffold of bone cement rod for fracture of the neck of the fifth metacarpal bone model (model A) and cross Kirschner wire fixation for fracture of the neck of the fifth metacarpal bone model (model B). Material attributes of each model were assigned and meshed in ANSYS Workbench 17.0 to establish a three-dimensional finite element model. Finally, axial application and three-point bending of the fifth metacarpal were performed on the articular surface of the fifth metacarpal head to calculate the maximum displacement of the distal fracture block of the two pressure methods, so as to evaluate the stability of the external fixation of the bone cement rod in the treatment of the fifth metacarpal neck fracture.Results ① When axial pressure was applied, the values of the maximum, minimum displacement and average displacement of the distal fracture fragment of model A were greater than those of model B, the values of the maximum, minimum displacement and average displacement of the proximal fracture fragment of model A were smaller than those of model B, and the maximum relative displacement, minimum relative displacement and average relative displacement of model A were greater than those of model B. ②In three-point bending force application, the maximum displacement of the distal fracture block of model A was less than that in model B, the minimum displacement of the distal fracture block was equal to that in model B, the mean values of the maximum and minimum displacements of the proximal fracture block were greater than those in model B, and the maximum relative displacement, the minimum relative displacement, and the mean relative displacement were greater in model A than in model B. ③Comparison of the overall stresses and the stresses in the two fixtures between model A and model B. The stresses in model A were significantly lower than those in model B.Conclusion The displacement and total position of the external fixation stent of the cement rod and the cross fixation of the Kirschner wire did not exceed 1 mm in the axial and longitudinal directions in the treatment of the fifth metacarpal neck fracture, and the difference was small. However, the external fixation bracket of the bone cement rod has less stress than that of the crossed Kirschner wire in the two force application methods, indicating that the external fixation bracket of the bone cement rod can provide reliable mechanical stability. |
