The Biomechanical Mechanism of Cranial Implant Exposure Following Decreased Intracranial Pressure: A Finite Element Analysis Study

Background: Skull prosthesis is widely used for cranioplasty, yet long-term implant exposure remains a challenging complication frequently requiring reoperation. Clinical observations suggest an association between low intracranial pressure (ICP) and progressive scalp thinning, with possible progression to mesh erosion and implant exposure. However, the potential biomechanical mechanism by which dynamic ICP fluctuations may contribute to scalp atrophy and implant exposure has not been characterized owing to limitations of in vivo measurement. Methods: To investigate the potential biomechanical basis of low ICP-induced exposure, finite element analysis was used to simulate the mechanical responses of three cranial implant designs (combine-pattern titanium mesh, circular-pore titanium mesh, polyetheretherketoneplate) and overlying scalp under dynamic ICP. A skull model was generated from Computed Tomography data. Loading included a uniform 50 N force with continuously graded ICP (−15 to 30 mmHg) and localized 50 N forces at central and off-central regions under discrete ICP levels. Results: This study provides the biomechanical insights that low ICP may amplify stress on scalp overlying combined-pattern titanium mesh, supporting the “low ICP–scalp atrophy–exposure” cascade. The circular-pore titanium mesh consistently exhibited low and stable mechanical responses across all pressures, whereas polyetheretherketone plate demonstrated nonlinear behavior with aberrantly high-stress under specific boundary conditions. The central implant region was identified as a potentially vulnerable zone. Conclusions: Low ICP significantly elevates central scalp stress, suggesting it may be a mechanical contributor to implant exposure. Circular-pore titanium mesh and polyetheretherketone plate showed more favorable biomechanical behavior, warranting further validation. In high-risk scenarios, central porosity reduction or flexible transitions may be considered potential design modifications to mitigate exposure.