gms | German Medical Science

Objectives: Spinopelvic fractures and approaches of operative stabilization are a constant source of controversial discussion. Some biomechanical data support the benefit of a spinopelvic stabilization and minimally invasive procedures help reduce the dissatisfying complication rate at the spinopelvic region. A spinopelvic stabilization can also be used as a triangular osteosynthesis in a minimally invasive manner. However, the role of a cross connector within these devices in still unclear. The additive insertion for the implantation of a cross connector makes the approach far more traumatic. To date, there has been no evaluation on the biomechanical need of a cross connector in the stabilizing lumbopelvic device.

Methods: A finite element model (FEM) of the L1-L5 spine segment with sacrum, both iliac bones, and a stabilization device was reconstructed from patient-specific CT images. Biomechanical outcomes from the numerical model were investigated by addressing uncertainties in material properties and levels of osseointegration. The biomechanical relevance of a cross connector in Denis zone I sacrum fractures was assessed in the FEM by applying bending (anteroposterior and lateral) as well as twisting forces in models of spinopelvic stabilization with and without a cross connector linked to the spinopelvic stabilization system (Two-way ANOVA/Mixed Model with post-hoc t-test and a Tukey correction for multiple hypothesis).

Results and conclusion: The designed FEM showed comparable values in ROM with reference to the literature. The superiority of the spinopelvic stabilization (L5/Os ilium) with or without cross connector compared to a non-operative procedure was confirmed in all analyzed loading conditions by reduced range-of-motion (ROM) and reduced stresses in the disk L5/S1, vertebral body L5 and the fracture area. By considering the combination of all loading cases, the presence of a cross connector reduced the maximum stress in the fracture area of around 10%. This difference has been statistically evaluated by considering uncertainties in material properties and different levels of osseointegration in the axial rotation case.

Together, the implementation of a spinopelvic stabilization (L5/Os ilium) in sacrum fractures sustained the fracture and led to enhanced biomechanical properties compared to a non-reductive procedure. The additional cross connector did not alter the resulting range of motion in L4/L5 or L5/sacrum. However, the addition of a cross connector significantly reduced the occurring stresses in the fracture area.

Figure 1 [Fig. 1]