RESUMEN
Background: Severing part of the thorax prior to bar placement is effective to improve outcomes in performing the Nuss procedure for asymmetric pectus excavatum. This study aims to elucidate the patterns of severing to provide an ideal outcome. Methods: Three-dimensional biomechanical computer models were produced simulating the thoraxes of 10 actual patients with asymmetric pectus excavatum. Virtual surgical operation was performed on the 10 models in 4 patterns: group 1-no part of the thorax was severed (default group). Group 2-The sternum was severed (sternum-severing group). Group 3-The ribs on the affected side were severed (rib-severing group). Group 4-Both the sternum and ribs on the affected side were severed (sternum/rib-severing group). After performing this preparation, simulation of bar placement was performed. Comparing the pre- and postoperative shapes of the models, we examined whether symmetry improved for each group. Results: Symmetry of the chest wall improved for rib-severing group and sternum/rib-severing group. Asymmetry remained for default group and sternum-severing group. Conclusions: Performance of the Nuss procedure for asymmetric pectus excavatum does not greatly improve symmetry of the chest wall. Severing the ribs as an additional maneuver is effective to improve symmetry.
RESUMEN
Background: Part of the skull can be lost due to neurosurgical diseases or trauma. Skulls with partial defects can develop different fracture patterns from those of intact skulls. This study aims to clarify the differences. Methods: A 3-dimensional skull model was produced by referring to the computer-tomography data of a 23-year-old intact male volunteer. We defined the model as Intact Model. Another model was produced by removing part of the frontal bone, which was defined as Defect Model. Dynamic simulations of impacts were performed varying the site and direction of impact. Fracture patterns caused by the impacts were calculated using dynamic analysis software (LS-DYNA; Livermore Software Technology Corp.) and were compared between the intact model and defect model. Results: When Defect Model was impacted, fracture involved wider areas than when Intact Model was impacted. This finding was observed not only when Defect Model was impacted on its defect side but also when it was impacted on its intact side. Conclusions: When a skull carrying a defect on one side is impacted, serious fracture occurs even when the non-defect side is impacted, meaning that a skull with a defect is vulnerable to impacts on the non-defect side. This finding should be taken into consideration in deciding indications of skull defect reconstruction.
RESUMEN
Background: Various materials are used to reconstruct cranial defects. The present study focuses on what happens when reconstructed skulls are impacted in trauma situations. Using biomechanical analysis, the present study elucidates how the hardness of reconstruction material affects the vulnerability of reconstructed skulls. Methods: A 3-dimensional finite element model was produced simulating the skull of an intact adult male. A defect was made on the left hemi-frontal part of the skull model. The defect was restored with artificial bone with 3 different hardness models. These models were respectively defined as Hard Model (simulating reconstruction with titanium), Moderate Model (simulating reconstruction with a material equivalent to human bone), and Soft Model (simulating reconstruction with hydroxyl apatite). Virtual impacts were applied on these models in 9 patterns, and the conditions of subsequent fracture were evaluated using finite element analysis. For each of the 9 impact patterns, the conditions of subsequent fracture were compared among the 3 models. Results: In 8 of the 9 impact patterns, the condition of fracture was more widespread for Hard Model than for Moderate Model and Soft Model. Conclusions: Skulls reconstructed with a hard material can develop serious fracture if they are impacted again. Therefore, usage of hard materials should be avoided to prevent serious injuries from secondary trauma.