title: Measuring pulsatile forces on the human cranium.
abstract: The cyclic stresses in the cranium caused by pulsation of the brain play an important role in the design of materials for cranioplasty, as well as craniofacial development. However, these stresses have never been quantified. In this study, the force in the epidural space against the cranium was measured intraoperatively in 10 patients using a miniature force probe. Heart and ventilatory rates computed from the force tracing correlated closely with the corresponding measured values in the patients, confirming that the forces measured were indeed a result of brain pulsation. The mean outward systolic normal and tangential stresses were 54.2 kilo-Pascals (kPa) and 345.4 kPa, respectively. The systolic shear stress was 199.8 kPa. Through mechanotransduction, these stresses play a role in cranial development. The calculated yield stress of a cranioplasty repair was 0.4 MPa, which is within one order of magnitude of the known strength of common calcium-phosphate cements. This indicates a possible relation of these pulsatile forces and occult failure of calcium-phosphate cement cranioplasties through material fatigue.
authors.affiliation: Division of Plastic Surgery and the Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Cory S
authors.initials: CS
authors.lastname: Goldberg
authors.forename: Oleh
authors.initials: O
authors.lastname: Antonyshyn
authors.forename: Rajiv
authors.initials: R
authors.lastname: Midha
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Fialkov
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001696:Biomechanical Phenomena; D001794:Blood Pressure / Q000502:physiology; D001843:Bone Cements / Q000737:chemistry; D001921:Brain / Q000502:physiology*; D002130:Calcium Phosphates / Q000737:chemistry; D004824:Epidural Space; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D012119:Respiration; D012212:Rheology; D012886:Skull / Q000254:growth & development / Q000502:physiology*; D013314:Stress, Mechanical; D013718:Tensile Strength; D014057:Tomography, X-Ray Computed; D014159:Transducers
chemical_list: D001843:Bone Cements; D002130:Calcium Phosphates; C020243:calcium phosphate