Effect of Lumbar Fusion and Pelvic Fixation Rigidity on Hip Joint Stress

Abstract

Study Design. This study compared hip stress among different types of lumbopelvic fusion based on finite element (FE) analysis. Objective. We believe that the number and placement of S2 AI screws, and whether the screws loosen likely influence hip joint stress in the finite element model. Summary of Background Data. Spinopelvic fixation hs been shown to increase the risk of progression for hip joint osteoarthritis. The biomechanical mechanism is not well understood. We hypothesize that the rigid pelvic fixation may induce stress at adjacent joints. Methods. A three-dimensional nonlinear FE model was constructed from the L4 vertebra to the femoral bone. From the intact model, we made four fusion models, each with different lower vertebrae instrumentation: 1) L4-S1 fusion; 2) L4-S2 AI screw fixation; 3) L4-S2 AI screw fixation with S2 AI screw loosening; and 4) L4-S1 and dual AI screw fixation (DSIF). A compressive load of 400 N was applied vertically to the L4 vertebra, followed by an additional 10 Nm bending moment about different axes to simulate either flexion, extension, left lateral bending, or right axial rotation. The distal femoral bone was completely restrained. von Mises stress and angular motion were analyzed across the hip joints within each fusion construct model. Results. Hip joint cartilage stress, and range of motion increased for all postures as pelvic fixation became more rigid. The DSIF model increased stress and angular motion at the hip joint more than SIF model. Our results suggest that more rigid fixation of the pelvis induces additional stress on the hip joint, which may precipitate or accelerate adjacent joint disease. Conclusion. Dual sacral AI fixation led to the highest stress, while loosening of S2 AI decreased stress on the hip joint. This study illustrates that more rigid fixation among lumbosacral fusion constructs increases biomechanical stress on the hip joints.

Spine

“…This study from Chicago (Illinois, USA) took a purely biomechanical approach and used a finite element model (FEM) to measure the effect of lumbar fusion, by looking at the stress on the hip joints following different types of lumbar fusion. 2 The study team constructed a four-fusion model with increasing stiffness: 1) L4-S1 fusion; 2) L4-S2 AI screw fixation; L4-S2AI screw fixation with S2AI screw loosening; and 4) L4-S1 and dual AI screw fixation (DSIF). The models were then loaded, first with a compressive load of 400 N applied vertically to the L4 vertebra, followed by 10 Nm bending moments to simulate flexion, extension, lateral bending, and axial rotation.…”

Elucidation of the Mechanism of Occasional Anterior Longitudinal Ligament Rupture with Posterior Correction Procedure for Adult Spinal Deformity Using LLIF–Finite Element Analysis of the Impact of the Lordotic Angle of Intervertebral LLIF Cage

“…FEA is a method used mainly in industrial fields, such as the construction industry, to perform mechanical simulations using a computer. Based on the design drawings of buildings and automobiles, three-dimensional (3D) models are created on a computer and converted into polyhedral called finite elements, and the stress, deformation, and motion of each element with respect to load and motion are predicted and analyzed [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. When correction surgery for ASD is planned, computed tomography (CT) is usually performed before surgery for diagnosis and treatment, and the surgical plan is also made using 3D measurements constructed from the CT data.…”

“…When correction surgery for ASD is planned, computed tomography (CT) is usually performed before surgery for diagnosis and treatment, and the surgical plan is also made using 3D measurements constructed from the CT data. By combining the above-mentioned FEA and CT data, it is possible to perform mechanical evaluation and simulation for surgery in various aspects when performing correction surgery for ASD [ 23 , 25 , 29 ].…”