How Partial Skull Defect Affects Vulnerability of the Skull in Traumatic Situations: A Biomechanical Study.

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.