Soehnlen, S. | Search bioRxiv

bioRxiv2024

Pelvic Ring Fractures: Does Spinopelvic Alignment Affect Sacral and Lumbopelvic Fixation Stability?

Background ContextPelvic ring is a complex boney and ligamentous complex and its structural integrity is paramount to be able to withstand the high forces. Pelvic ring fractures, which can result from low-energy impacts or high-velocity injuries and falls from great heights, can severely impair the structural integrity of the pelvic ring. These injuries can be fatal, especially in geriatric patients, with mortality rates ranging between 10% and 16%. Pelvic ring injuries require immediate stabilization, typically performed through internal fixation, to maintain circulatory balance and achieve anatomical restoration of the pelvis. MethodsA previously validated FE model of the spine, pelvis, and femur model was used to evaluate how different fixation techniques for pelvic ring injury affect spinopelvic biomechanics. The SS, PI, PT and LL of the normal, intact model was modified to generate two more SS models for this study. One modified model with an SS of 20{o} was considered the low SS model (SSD), while the second modified model with an SS of 32{o} was termed the high SS model (SSI). A unilateral pelvic ring fracture was simulated by resecting the left side of the sacrum and pelvis. The fractures were stabilized using two different posterior stabilization techniques 1) The fractures were stabilized using two different posterior stabilization techniques, and 2) L5-Ilium posterior screw fixation without cross connector (L5_PF_WO_CC). ResultsSSI demonstrated the higher range of motion, followed by Normal model and least by SSD model at right Sacroiliac Joint. No differences were seen between with and without cross connector model for range of motion at right SIJ. For L5-S1 motion models treated with cross connectors demonstrated the least motion compared to those treated without cross connectors for all configurations and loading conditions. For the sacrum fracture, models with high sacral slopes recorded the least horizontal displacement, followed by decreased sacral slope models for both configurations and loading conditions.

bioengineering↗

bioRxiv2024

Biomechanical Implications of Spinopelvic Alignment on Femoral Head Cartilage and the Proximal Femoral Physis in Slipped Capital Femoral Epiphysis: A Theoretical Finite Element Analysis

BackgroundSlipped capital femoral epiphysis (SCFE) is a prevalent pediatric hip disorder. Recent studies suggest the spines sagittal profile may influence the proximal femoral growth plates slippage, an aspect not extensively explored. This study utilizes finite element analysis to investigate how different spinopelvic alignments affect shear stress and potential slippage at the growth plate. MethodsA finite element model was developed from CT scans of a healthy adult male lumbar spine, pelvis, and femurs. The model was subjected to various sagittal alignments through rotational boundary conditions. Simulations of two-leg stance, one-leg stance, walking heel strike, ascending stairs heel strike, and descending stairs heel strike were conducted. Parameters measured included hip joint contact area, stress, and maximum Tresca (shear) stress on the growth plate. FindingsPosterior pelvic tilt cases indicated larger shear stresses compared to the anterior pelvic tilt variants except in two leg stance. Two leg stance resulted in decreases in the posterior tilted pelvi variants compared to anterior tilted pelvi, however a combination of posterior pelvic tilt and high pelvic incidence indicated larger shear stresses on the growth plate. One leg stance and heal strike resulted in higher shear stress on the growth plate in posterior pelvic tilt variants compared to anterior pelvic tilt, with a combination of posterior pelvic tilt and high pelvic incidence resulting in the largest shear stress. InterpretationOur findings suggest that posterior pelvic tilt and high pelvic incidence can lead to increased shear stress at the growth plate. Activities performed in patients with these alignments may predispose to biomechanical loading that shears the growth plate, potentially causing slippage.

bioengineering↗