Finite Element- and Design of Experiment-Derived Optimization of Screw Configurations and a Locking Plate for Internal Fixation System

Abstract

Objectives. The optimization for the screw configurations and bone plate parameters was studied to improve the biomechanical performances such as reliable internal fixation and beneficial callus growth for the clinical treatment of femoral shaft fracture. Methods. The finite element analysis (FEA) of internal fixation system under different screw configurations based on the orthogonal design was performed and so was for the different structural parameters of the locking plate based on the combination of uniform and orthogonal design. Moreover, orthogonal experiment weight matrixes for four evaluation indexes with FEA were analyzed. Results. The analytical results showed the optimal scheme of screw configuration was that screws are omitted in the thread holes near the fracture site, and single cortical screws are used in the following holes to the distal end, while the double cortical screws are fixed in thread holes that are distal to the fracture; in the other words, the length of the screws showed an increasing trend from the fracture site to the distal end in the optimized configuration. The plate structure was optimized when thread holes gap reached 13 mm, with a width of 11 mm and 4.6 mm and 5 mm for thickness and diameter of the screw, respectively. The biomechanical performance of the internal fixation construct was further improved by about 10% based on the optimal strain range and lower stress in the internal fixation system. Conclusions. The proposed orthogonal design and uniform design can be used in a more efficient way for the optimization of internal fixation system, which can reduce the simulation runs to about 10% compared with comprehensive test, and the methodology can be also used for other types of fractures to achieve better internal fixation stability and optimal healing efficiency, which may provide a method for an orthopedist in choosing the screw configurations and parameters for internal fixation system in a more efficient way.

Osteosynthesis of diaphyseal tibia fracture with locking compression plates: A numerical investigation using Taguchi and ANOVA

“…Our finding also corroborated the result of, 16 which studied the risk of implant failure and argued against the placement of screws close to the fracture site. With regard to the present results for the optimal screw diameter ( D = 5.5 mm), LCP thickness ( T = 4 mm), and plate width ( W = 12 mm), it is encouraging to compare our findings with those found by another study, 55 which resulted in 5 mm, 4.6 mm, and 11 mm, as optimal values for D , T , and W , respectively. Although the findings of the study by Sheng and coworkers were determined through an optimization scheme, the criteria used for evaluating the optimal performance of LCP were limited to the stress in the internal fixation construct and interfragmentary strain in callus, which was less general and simpler than our study.…”

A mechanobiological approach to find the optimal thickness for the locking compression plate: Finite element investigations

“…Recently, Sheng and co-workers used experimentally validated FE models, without modeling tissue differentiation at the fracture gap, and found the optimal thickness of 4.6 mm for the internal fixation of femoral mid-shaft fracture, fixed by an 10-holes LCP, using a comprehensive optimization process for the LCP system. 44…”

Ideal plate screw configuration in femoral shaft fractures: 3D finite element analysis

“…The location and configuration of the screws in the plate is another important parameter in plate and screw osteosynthesis. In a study they conducted, Wei Sheng et al [13] found that the stress loads on the plate in nine different plate screw configurations of the same length were similar. They also found that the stress on the plate and femur increased significantly in the first and second screw holes near the fracture.…”

“…Screw diameter also plays an important role in the mechanics of internal fixation [28,29]. In their study comparing the screw diameters of 4 mm, 4.5 mm, 5 mm, Wei Sheng et al [13] revealed that the highest stress on the plate was on the 4 mm screws. They showed that the most suitable screws were those with 5mm diameter.…”

“…It has been stated that most of the causes of failure of internal fixation materials are related to material fatigue [11]. There are many studies about the plate screw configuration [12][13][14]. However, there is still no consensus on the optimal plate screw configuration.…”