Performing a MOWHTO via the biplanar rather than the monoplanar technique allows larger-sized wedges to be opened with less risk of lateral cortical fracture. Thus, larger gaps can be opened and higher angle corrections can be achieved using the biplanar osteotomy procedure. From a clinical viewpoint, the biplanar osteotomy technique reduced the risk of lateral cortical hinge fracture during MOWHTO.

Background: Both the ilioinguinal and Stoppa approaches have been used as standard methods for treating anterior column fractures of the pelvis. Objective: We aimed to compare the rigidity of pelvises that were treated using these two approaches. Methods: Fifteen synthetic pelvises were used as test models. Of these, 5 pelvises did not undergo any treatment (control group), and 10 pelvises underwent treatment of one column using the ilioinguinal approach and the other using the medial Stoppa approach (treated group). The compression test was performed on all pelvises, and rigidity of the pelvises was compared between the control and treated groups. Results: A statistical difference was found in the angle between the center of the femoral head and the line from the pubic symphysis to load application between the control and treated groups, using the ilioinguinal approach. The parametric displacement was greater in the treated group using the ilioinguinal approach than in the control group. There were no significant differences between the control and treated groups using the Stoppa approach, and the ilioinguinal approaches. Conclusion: Clinically, the Stoppa approach has several advantages over the ilioinguinal approach. However, based on the compression test, there was no difference in biomechanical rigidity between the fixations performed using these two approaches.

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Introduction. Polyaxial screws had been only tested according to the ASTM standards (when they were perpendicularly positioned to the rod). In this study, effects of the pedicle screws angled fixation to the rod on the mechanical properties of fixation were investigated. Materials and Method. 30 vertically fixed screws and 30 screws fixed with angle were used in the study. Screws were used in three different diameters which were 6.5 mm, 7.0 mm, and 7.5 mm, in equal numbers. Axial pull-out and flexion moment tests were performed. Test results compared with each other using appropriate statistical methods. Results. In pull-out test, vertically fixed screws, in 6.5 mm and 7.0 mm diameter, had significantly higher maximum load values than angled fixed screws with the same diameters (P < 0.01). Additionally, vertically fixed screws, in all diameters, had significantly greater stiffness according to corresponding size fixed with angle (P < 0.005). Conclusion. Fixing the pedicle screw to the rod with angle significantly decreased the pull-out stiffness in all diameters. Similarly, pedicle screw instrumentation fixed with angle decreased the minimum sagittal angle between the rod and the screw in all diameters for flexion moment test but the differences were not significant.

Transdiscal screw fixation is generally performed in the treatment of high-grade L5-S1 spondylolisthesis. The main thought of the study is that the biomechanical performances of the transdiscal pedicle screw fixation can be identical to standard posterior pedicle screw fixations with or without transforaminal lumbar interbody fusion cage insertion. Lumbosacral portions and pelvises of 45 healthy lambs' vertebrae were dissected. Animal cadavers were randomly and equally divided into three groups for instrumentation. Three fixation systems, L5-S1 posterior pedicle screw fixation, L5-S1 posterior pedicle screw fixation with transforaminal lumbar interbody fusion cage insertion, and L5-S1 transdiscal pedicle screw fixation, were generated. Axial compression, flexion, and torsion tests were conducted on test samples of each system. In axial compression, L5-S1 transdiscal fixation was less stiff than L5-S1 posterior pedicle screw fixation with transforaminal lumbar interbody fusion cage insertion. There were no significant differences between groups in flexion. Furthermore, L5-S1 posterior fixation was stiffest under torsional loads. When axial compression and flexion loads are taken into consideration, transdiscal fixation can be alternatively used instead of posterior pedicle screw fixation in the treatment of L5-S1 spondylolisthesis because it satisfies enough stability. However, in torsion, posterior fixation is shown as a better option due to its higher stiffness.