Biomechanical study of anterior and posterior pelvic rings using pedicle screw fixation for Tile C1 pelvic fractures: Finite element analysis

Abstract

Objective The purpose of this study was to analyse the biomechanical characteristics of pedicle screws with different placement methods and diameters in the treatment of Tile C1 pelvic fractures by finite element simulation technology and to compare them with the plate fixation model to verify the effectiveness of pedicle screw fixation. Methods A three-dimensional digital model of a normal pelvis was obtained using computed tomography images. A finite element model of a normal pelvis containing major ligaments was built and validated (Model 1). Based on the verified normal pelvis finite element model, a Tile C1 pelvic fracture model was established (Model 2), and then a plate fixation model (Model 3) and a pedicle screw fixation model with different screw placement methods and diameters were established (Models 4–15). For all pelvic fracture fixation models, a vertical load of 500 N was applied on the upper surface of the sacrum to test the displacement and stress distribution of the pelvis in the standing state with both legs. Results The finite element simulation results showed the maximum displacement of Model 1 and Models 3–15 to be less than 1 mm. The overall maximum displacement of Models 4–15 was slightly larger than that of Model 3 (the maximum difference was 177.91×10−3 mm), but the maximum displacement of iliac bone and internal fixation in Models 4–15 was smaller than that of Model 3. The overall maximum stress (maximum stress of the ilium) and maximum stress of internal fixation in Models 4–15 were less than those in Model 3. The maximum displacement difference and maximum stress difference at the fracture of the pubic ramus between each fixed model were less than 0.01 mm and 1 MPa, respectively. The greater the diameter and number of pedicle screws were, the smaller the maximum displacement and stress of the pelvic fracture models were.The maximum displacement and stress of the pelvic fracture models of the screws placed on the injured side of the pubic region were smaller than the screws on the healthy side. Conclusion Both the anterior and posterior pelvic rings are fixed with a pedicle screw rod system for treatment of Tile C1 pelvic fractures, which can obtain sufficient biomechanical stability and can be used as a suitable alternative to other implants.The greater the diameter and number of pedicle screws were, the greater the pelvic stability was, and the greater was the stability of the screws placed on the injured side of the pubic region than the screws on the healthy side.

Numerical study of pedicle screw construction and locking compression plate fixation in posterior pelvic ring injuries: Analyzed by finite element method

“…The peak stress of the implant was lower than the yield stress in both models, suggesting that the 2 fixation methods for the treatment of unstable pelvic ring injuries could be safe. The results were in concordance with those of Song et al [ 13 ] who conducted a biomechanical study on the treatment of Tile C1 pelvic fractures and found that the maximum stresses of the ilium and implant in the pedicle screw model were less than those in the plate model. In another biomechanical study, Salášek et al [ 25 ] demonstrated that the pedicle screw construction experienced lower stress than 2 sacroiliac screws.…”

“…[ 6 , 11 ] To address these limitations, the pedicle screw construction has been introduced as an alternative to treat posterior pelvic ring injuries. [ 13 ] Bi et al [ 5 ] clinically compared the pedicle screw construction with the LCP in a retrospective study and observed that the size of incision, operation duration and bleeding volume were statistically smaller in the pedicle screw group than in the LCP group.…”

“…Evidence suggests that the pedicle screw construction can provide sufficient biomechanical stability in the treatment of unstable posterior pelvic ring injuries. Song et al [ 13 ] compared pedicle screw fixation with 2 anterior reconstruction plates in the treatment of Tile C1 pelvic fractures (unilateral sacroiliac joint injury combined with superior and inferior pubic ramus fractures) using FE simulation, and the results showed that the maximum displacements of the ilium and implant in the pedicle screw model were smaller than those in the plate model. Our results showed that the maximum vertical displacement, the maximum posterior displacement, the maximum right displacement, and the overall maximum displacement of the sacrum in the pedicle screw model decreased by 50.1%, 43.5%, 75.4%, and 51.2% compared to the plate model.…”

“…[ 11 ] To avoid these limitations, a minimally invasive pedicle screw-rod fixator has been used for the treatment of posterior pelvic ring injuries. [ 13 ] The posterior fixator utilizes 2 pedicle screws connected to a transverse rod for the structural stability of the posterior pelvic ring using a percutaneous invasive technique. Clinical trials have also demonstrated good results with the posterior pedicle screw construct for unstable posterior pelvic ring injuries.…”