Divergent K-wires in the sagittal plane have minimal impact on fixation stability and the resulting early clinical outcomes in patients with transverse patellar fractures

Transverse patellar fractures are typically treated with tension band wiring using Kirschner wires. This technique converts anterior tensile forces into articular compressive forces, providing the stability essential for early fracture healing and weight-bearing. Fixation configuration significantly influences stability; while divergent constructs offer superior angular stability in other fractures, AO principles recommend parallel wires to permit dynamic fragment compression. Although a divergent angle is often observed on lateral radiographs, its impact on early healing and weight-bearing remains unclear. The main objective of this study was to investigate this issue and provide theoretical guidance for optimizing TBW fixation. This retrospective study included patients who underwent K-wire tension band fixation for transverse patellar fractures. The angle between the K-wires was measured on immediate postoperative lateral radiographs. Early fracture union and pain-free weight-bearing were assessed at the 3-month follow-up. Biomechanical models were developed to simulate varying K-wire trajectories observed radiographically. Inter-model differences in implant stress distribution and fracture fragment displacement were quantified under axial loading at different angles. Clinical and biomechanical analyses revealed consistent findings. Similar K-wire divergent angles were observed in patients with differing clinical outcomes, specifically regarding early fracture union and pain-free weight-bearing. Under all loading conditions, models with different K-wire trajectories exhibited comparable stress and displacement values. The divergent configuration of K-wires has only a minimal impact on the stability of transverse patellar fracture fixation and on early clinical outcomes following TBW in patients with transverse patellar fractures.