Biomechanical investigation of the type and configuration of screws used in high tibial osteotomy with titanium locking plate and screw fixation

Yen-Nien Chen,Yao-Te Peng,Chih-Hsien Chen,Chun-Ting Li,Chih-Wei Chang,Chih-Han Chang,Chi-Rung Chung

doi:10.1186/s13018-019-1062-8

Abstract

BackgroundTo maintain the corrected alignment after high tibial osteotomy (HTO), fixation with titanium locking plate and screws is widely used in current practice; however, screw breakage is a common complication. Thus, this study was to investigate the mechanical stability of HTO with locking plate and various screw fixations, including the length as well as the type.MethodsA finite element (FE) model involving a distal femur, meniscus, and a proximal tibia with HTO fixed with a titanium locking plate and screws was created. The angle of the medial open wedge was 12°, and bone graft was not used. Two types of screws, namely conventional locking and far-cortical locking screws, with various lengths and configurations were used. At the proximal tibia, conventional locking screws with different lengths, 30 and 55 mm, were used; at the tibia shaft, different screw fixations including one-cortical, two-cortical, and far-cortical locking screws were used.ResultsThe use of far-cortical locking screw generated the highest equivalent stress on the screws, which was four times (from 137.3 to 541 MPa) higher than that of the one-cortical screw. Also, it led to the maximum deformation of the tibia and a greater gap deformation at the osteotomy site, which was twice (from 0.222 to 0.442 mm) larger than that of the one-cortical screw. The effect of different locking screw length on tibia deformation and implant stress was minor.ConclusionThus, far-cortical locking screws and plates increase interfragmentary movement but the screw stress is relatively high. Increasing the protection time (partial weight duration) is suggested to decrease the risk of screw breakage in HTO through fixation with titanium far-cortical locking screws and plates.

Highlights

High tibial osteotomy (HTO) with medial opening wedge is a surgical technique to reconstruct the bony structure of knees and correct their mechanical axis [1, 2]
This study aimed to explore the mechanical stability and screw stress of high tibial osteotomy (HTO) fixed with titanium locking plate and screws comparing various lengths and types of locking screws using the finite element (FE) method
The HTO model with medial open wedge and metallic locking plate and screw fixation was created in SolidWorks, too

Summary

Introduction

High tibial osteotomy (HTO) with medial opening wedge is a surgical technique to reconstruct the bony structure of knees and correct their mechanical axis [1, 2]. Further studies focused either on the structural stability established between the bone and plate or on the creation of beneficial biomechanical stimuli from interfragmentary movement via flexible/ dynamic fixation were made in the past [11,12,13] In these biomechanical studies, some issues including the geometry and configuration of plate, the use of wedge spacer, and even the interfragmentary movement promoting callus formation during bony healing [7, 11, 14,15,16] were investigated. To maintain the corrected alignment after high tibial osteotomy (HTO), fixation with titanium locking plate and screws is widely used in current practice; screw breakage is a common complication. This study was to investigate the mechanical stability of HTO with locking plate and various screw fixations, including the length as well as the type

Objectives

Methods

Results

Conclusion