The Viscoelastic Properties of a Decompressive Craniectomy Site toward Clinical Application

摘要

Background: Decompressive craniectomy (DC) is a neurosurgical procedure in which part of the skull is removed to rescue from acute brain edema. We often palpate the stiffness of a cranial defect in a patient with DC due to prospect the brain stiffness. Object: This study aims to evaluate viscoelastic property of a DC site in bed-side by using a tactile resonance sensor with a stress-strain function. We would like to discuss the relationship between viscoelastic properties and tissue elastance of a DC site. Method: Seven participants were measured the viscoelastic properties of a DC site under stable conditions. This sensor had the push-pull motor automatically and measured simultaneously both pressure (Pr) and change in frequency (dF) for a measured depth. This handheld device was adjusted to come in contact with skin surface for clinical application of a palpation-like usage. Results: We plotted the average scatter graphs of Pr and dF for the depth. So we calculated the shear elastic modulus (G) by using the Lee & Radok's correspondence principle under the assumption of an isotropic, small deformation of a spherical indentation. The exponential curve fitting was presumed as the viscoelastic model with 1 spring and 3 dumpers. The Poisson' ratio (v) was 0.447 from G-value and Young's modulus. The tissue elastance (= AP/AV) was evaluated as elastance = Ge~*0.00246 at depth 3.0mm. Conclusions: The measurement of viscoelastic properties of a decompressive site yielded the following values under the stable conditions: Ge = 1.714 ± 0.75 and v=0.447. This technique was no adverse effect. The G-value of a decompressive site was reflected to the tissue elastance at the max depth. The stiffness of a decompressive site might be close to brain stiffness.