Mineralization and biodegradation of CSF shunting systems

The mineralization and biodegradation of cerebrospinal fluid shunting systems were studied using material from 25 shunts that had been implanted for between 6 days and 10 years. New unused materials were also examined for comparison. Surface changes in six systems could be observed under an operating microscope. Substantial quantities of a white deposit had adhered to the tubing in four of the shunts. These changes were most advanced in the galeal penetrative portion of the shunts and are believed to have been caused by mechanical stress. Scanning electron microscopic analysis revealed surface wrinkles, microscopic holes, and tiny particles, suggesting deterioration of the material itself. An energy-dispersive analysis using x-rays demonstrated that the surface deposits were due to mineralization of calcium phosphate and that the tiny particle growth was aluminum. These changes may be a consequence of the degradation of silicone rubber. A discriminant analysis of the mineralization was carried out; thus, the age of the host and the duration of system implantation could be correlated with the incidence of mineralization (p less than 0.1). A measurement of the physical properties showed progressive change with a remarkable deterioration in systems implanted for more than 5 years.