Microstructural Alterations of Silicone Catheters in an Animal Experiment: Histopathology and SEM Findings

Introduction: Biocompatibility of implants in humans has been classified as inert, tolerated, and bioactive. In shunt-treated patients, catheter-induced complications account for up to 70% of all hardware failures. Our objective was to study whether foreign body reactions to silicone shunt catheters in subcutaneous tissue and at their distal, intraperitoneal ends leading to occlusion can be reproduced in an animal model. Materials and Methods: Twelve different silicone catheters were implanted in 6-week-old Wistar rats: (a) purely in the subcutaneous tissue and (b) through the subcutaneous tissue into the peritoneal cavity. One of the catheters was of our own design with a silicated surface. After 1 year, all catheters were explanted and were examined by histopathology and scanning electron microscopy (SEM). Results: Histopathological analysis revealed the development of collagenous membranes and chronic immune reactions around the catheters. Completely organized intraluminal obliteration was seen in six intraperitoneally inserted catheters. SEM demonstrated calcifications and signs of biodegradation. Silicated catheters showed the most extensive calcifications. Discussion: Hydrocephalus shunt catheters cannot be termed inert or biotolerated. Rather, they must be regarded as bio-active implants. The extensive reaction on silicated catheters can act as reference to estimate the biocompatibility of surface modifications. The model proved appropriate for further studies.