A nonlinear biomechanical model for evaluation of cerebrospinal fluid shunt systems.

In view of complications arising from physical properties of cerebrospinal fluid shunts, a biomechanical model of hydrocephalus was set up to study in vivo parameters that may influence their function. These include: intracranial pressure, compliance and pulses, intrathoracic, intra-abdominal, and subcutaneous pressures, and the effects of siphonage and repeated valve flushing. Each of these factors was studied separately upon shunt implantation in the model. Results of testing of a sample low-pressure valve with antisiphon device conformed with consumer information in regard to valve opening pressure and pressure flow measurements. No customer information, however, was supplied concerning the deleterious effects of direct subcutaneous pressure, variable degrees of siphonage, and repeated valve flushing that were demonstrated by the model. Such results indicate that shunts should be similarly tested prior to marketing and implantation in patients.