Zoltán Jónás

Further development of our finite element pelvic model to compare fixation methods for pelvic fractures

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.

A complementary thoracic implant for the surgical correction of the scoliotic curve. A preliminary report

SummaryThe results of the surgical correction of scoliosis through posterior approach have significantly improved by the introduction of new implants during the past decades. Even with these improvements the available implants only allow limited correction especially regarding axial rotation, and also their application is rather complicated. We developed a new implant which simultaneously grasps and exerts forces on both transverse processes of the vertebrae, to achieve a more efficient and safer correction with a simple surgical technique. In our paper we report on the concept of the new implant, its most important features, its mechanical tests, cadaver experimentations, and biomechanical assessments.

Intraosseous structural graft technique: a new surgical concept in the treatment of superolateral defects in case of dysplastic acetabulum, during hip replacement surgery biomechanical and cadaver experimentations

AbstractPurposeThe replacement of the dysplastic hip, despite the numerous available surgical techniques, is not entirely solved. One of the reasons for this is the relative lack of bone in the acetabulum. In this study, we present a new concept (intraosseous structural graft technique), with the aim to improve the primary stability and biological environment of the graft.MethodsDuring the procedure in the cranial quadrant of the acetabulum, a proximally hinged cortico-spongious plate is fashioned that is opened laterally and a wedge-shaped graft made from the femoral head is impacted. The precisely fitted graft has good primary rotational and cranial stability which is further improved by a bicortical screw.ResultsThe hypothesis is supported by examination on 3D models. Cadaver experimentations were performed on 19 hips of 10 cadavers, and stability testing was done on a further 20 hips of 10 cadavers with a material testing apparatus. Also the analysis of the biological and mechanical properties of the graft and the implant were examined.ConclusionBased on our results, it can be concluded that our technique provides good primary stability with a more favorable biological condition for bony incorporation compared to other bulk bone graft techniques.

Does surgically fixation of pubic fracture increase the stability of the operated posterior pelvis

OBJECTIVES This study aims to investigate whether surgical treatment of pubic rami fractures increases the stability of the posterior pelvis. PATIENTS AND METHODS A finite element pelvic model with improved geometric and material characteristics was analyzed. By imitating a standing position, a type I Denis sacrum fracture and a unilateral pubis fracture, we measured the differences in tension and displacement. The posterior injury was treated with a direct plate synthesis or transsacral plate synthesis, while the pubis fracture was left without fixation or fixed with either a retrograde pubic screw or plate synthesis. RESULTS The operative fixation of pubic rami fractures decreased the movement in the fracture gap not only at the site of the pubis fracture, but also at the site of the fixed sacrum fracture. The plate synthesis provided greater stability of the anterior fracture than the retrograde screw. The tensions in the implants were below the allowed values. CONCLUSION We concluded that surgically fixation of pubic fracture increases the stability of the operated posterior pelvis.