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OBJECTIVES This study aims to compare mechanical stability of osteosynthesis (plate and screw fixation) alone versus the same method supplemented with hip arthroplasty (hybrid solution) for double column fractures in elderly. PATIENTS AND METHODS Mechanical investigations were performed on an advanced finite element pelvis model developed for double column fractures. The following simulated implant combinations were analyzed: modular acetabular basket with a ring with polyaxial screws and U-plate; plates with polyaxial screws placed on the medial-horizontal (linea terminalis) and quadrilateral bone surfaces; modular acetabular cup with U-plates; and polyaxial screws in sizes optimized based on a finite element model (FEM). Using the models, the possible shifts in peak load positions arising in different movement patterns caused by load and tension and implant deformation were measured. RESULTS Hybrid systems resulted in minimal deformation of the implants already available on the market. We observed less possible shifts and greater stability in the acetabular fracture zones, compared to conventional osteosynthesis alone. Optimization with available and compatible implant sizes led to a further significant increase in stability. CONCLUSION Hybrid method combining osteosynthesis and prosthesis implantation provide more stability in biomechanical models in the treatment of double column fractures in elderly.

OBJECTIVES This study aims to investigate if the stabilization of iliac wing fractures influences the stability of the acetabular osteosynthesis, if surgical fixation is the choice of treatment, and which technique to be used. MATERIALS AND METHODS In the study, measurements were performed with an improved finite element model. Tension and displacement values were measured in bicolumnar acetabular fractures in the following cases: combination of cranial and medial plate fixation through the linea terminalis, or combination of cranial plate and quadrilateral surface plates. The iliac wing fracture was either not fixed, or fixed with screws or with a plate. RESULTS In cases where osteosynthesis was performed through the linea terminalis, 0.01 mm fracture gap displacement was observed with the use of a combination of cranial and quadrilateral surface plate fixations. In the combination of cranial and medial positioned plates, the displacement in the fracture gap was 0.088 mm. The fixation of the iliac wing fracture did not improve the stability of the osteosynthesis of the linea terminalis. Plate fixation of the iliac wing fracture was more stable than screw fixation alone. CONCLUSION In double column fractures, if the reduction does not require an anterior approach, it is not necessary to fix the iliac wing fracture only to improve the stability of the fixation. If the reduction does require an anterior approach, it is worth fixing the iliac wing fracture with the technically less demanding screw fixation.

Objectives In this study, we aimed to create a realistic model which is suitable for computerized simulation of any kind of fractures and provides reliable results. Patients and methods We used a plastic pelvic model to construct advanced specimens. The data were retrieved from the computed tomography scans of a healthy pelvis. A geometrically exact model by the means of three-dimensional scanning of the plastic pelvis was obtained. The material properties of the bony parts based on the data retrieved from the computed tomography scans were modified. The pelvis was divided into distinct segments and the proportion of the cortical and cancellous bone substance in each segment were determined to make the material properties accurate. In the validation of the pelvic model, a type C pelvic injury was simulated and the fracture of the sacrum and the symphyseolysis were stabilized with plates. These data were compared with those of previously performed cadaver experiments. Results Based on the simulation performed on the new model, the shift values between the fragments of the broken sacrum approximated the reported values of our cadaver experiments and also arising strains remained in the tolerable interval. Conclusion Our new finite element pelvic model represents the pelvis more accurately than the former one. As the validation of the model was successful, it is suitable for computerized simulation of any kind of fractures offering reliable results.