Candy box technique for the fixation of inferior pole patellar fractures: finite element analysis and biomechanical experiments

Abstract

Background Maintaining effective reduction and firm fixation in inferior pole patellar fractures is a highly challenging task. There are various treatment methods available; although tension-band wiring combined with cerclage wiring (TBWC) is the mainstream approach, its effectiveness is limited. Herein, we propose and evaluate a new technique called candy box (CB), based on separate vertical wiring (SVW), for the treatment of inferior pole patellar fractures. Specifically, we provide biomechanical evidence for its clinical application. Methods Five fixation models were built: SVW combined with cerclage wiring (SVWC); TBWC; modified SVW with the middle (MSVW-A) or upper (MSVW-B) 1/3 of the steel wire reserved, and CB. A finite element analysis was performed to compare the displacement and stress under 100-N, 200-N, 300-N, 400-N and 500-N force loads. Three-dimensional printing technology was utilized to create fracture models, and the average displacement of each model group was compared under a 500-N force. Results The results of the finite element analysis indicate that CB technology exhibits significantly lower maximum displacement, bone stress, and wire stress compared to that with other technologies under different loads. Additionally, in biomechanical experiments, the average force displacement in the CB group was significantly smaller than that with other methods under a 500-N force (P < 0.05). Conclusions CB technology has the potential to overcome the limitations of current techniques due to its superior biomechanical characteristics. By incorporating early functional exercise and ensuring strong internal fixation, patient prognosis could be enhanced. However, further clinical trials are needed to fully evaluate the therapeutic effects of CB technology.

Computational evaluation of wire position using separate vertical wire technique and candy box technique for the fixation of inferior pole patellar fractures: a finite element analysis

“…Then, the fixed wire around the periphery of the patella was replaced with two wires on the side of the patella through the bone tunnel ( Figure 1 ). Our team has previously confirmed both biomechanical advantages and potential clinical benefits associated with CB technology ( Fan et al, 2023 ).…”

“…In this new approach, we replace the circumferential wire of the SVWC technique with two transverse bone tunnel wires positioned at the upper/middle 1/3 of the patella. We then conducted finite element analysis and biomechanical testing, which confirmed that the CB technique performs exceptionally well under different loads ( Fan et al, 2023 ). However, there is currently no definitive explanation for the optimal positions of vertical bone tunnel steel wires in SVW technology and horizontal bone tunnel steel wires in CB technology.…”

“…However, when steel wires are inserted into the fractured comminuted area at the inferior pole, it can result in weak fixation and potential displacement of small bone fragments. This increases the risk of internal fixation failure and nonunion ( Zhu et al, 2022 ; Fan et al, 2023 ).…”