Effect of Sacropelvic Hardware on Axis and Center of Rotation of the Sacroiliac Joint: A Finite Element Study.

Background: The sacroiliac joint (SIJ) transfers the load of the upper body to the lower extremities while allowing a variable physiological movement among individuals. The axis of rotation (AoR) and center of rotation (CoR) of the SIJ can be evaluated to analyze the stability of the SIJ, including when the sacrum is fixed. The purpose of this study was to determine how load intensity affects the SIJ for the intact model and to characterize how sacropelvic fixation performed with different techniques affects this joint.

The Simulation of Muscles Forces Increases the Stresses in Lumbar Fixation Implants with Respect to Pure Moment Loading.

Simplified loading conditions such as pure moments are frequently used to compare different instrumentation techniques to treat spine disorders. The purpose of this study was to determine if the use of realistic loading conditions such as muscle forces can alter the stresses in the implants with respect to pure moment loading. A musculoskeletal model and a finite element model sharing the same anatomy were built and validated against data, and coupled in order to drive the finite element model with muscle forces calculated by the musculoskeletal one for a prescribed motion.

Innovative sacropelvic fixation using iliac screws and triangular titanium implants.

Purpose: Sacropelvic fixation is frequently used in combination with thoracolumbar instrumentation for the correction of severe spinal deformities. The purpose of this study was to explore the effects of the triangular titanium implants on the iliac screw fixation. Our hypothesis was that the use of triangular titanium implants can increase the stability of the iliac screw fixation.

Assessment of trunk muscle activation and intervertebral load in adolescent idiopathic scoliosis by musculoskeletal modelling approach.

Adolescent idiopathic scoliosis (AIS) is a three-dimensional deformity of the spine, the aetiology and pathogenesis of which are poorly understood. Unfortunately, biomechanical data describing trunk muscle activation and intervertebral load, which can contribute to understanding the pathomechanics of the AIS spine, cannot be measured in vivo due to the invasiveness of the procedures. The present study provides the biomechanical characterization of the spinal loads in scoliotic subjects by exploiting musculoskeletal modelling approach, allowing for calculating biomechanical measures in an assigned posture.

The use of triangular implants to enhance sacropelvic fixation: a finite element investigation.

Background Context: Long thoracolumbar fixation and fusion have become a consolidated treatment for severe spinal disorders. Concomitant sacropelvic fixation with S2 alar-iliac (S2AI) screws is frequently performed to limit instrumentation failure and pseudarthrosis at the lumbosacral junction.

Purpose: This study explored the use of triangular titanium implants in different configurations in which the implants supplemented standard sacropelvic fixation with S2AI screws in order to further increase the stability of S2AI fixation.