Animal Experiments to Evaluate Complications of Foreign Materials on Silicone with Shunt Catheters: Preliminary Results
Use of silicone to manufacture hydrocephalus shunts has been critical for the successful introduction of modern shunt therapy. However reactions to foreign material cause biodegradation, calcification, and massive scarring, and their impact on the still h
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Abstract Objective Use of silicone to manufacture hydrocephalus shunts has been critical for the successful introduction of modern shunt therapy. However reactions to foreign material cause biodegradation, calcification, and massive scarring, and their impact on the still high shunt failure rate might have been undervalued in the past. We established an animal model to simulate the conditions and reactions with the silicone catheter in human patients. Methods We implanted catheters from different hydrocephalus shunt manufacturers available on the world market in 12 four-week old Wistar rats. To mimic shearing forces and tensile stress, the tubes were firmly fixed proximally and distally in a growing rat. The catheters remained in the subcutaneous tissue for 1 year before being removed and studied using scanning electron microscopy and histological studies. Results All of the implanted long catheters showed fractures and calcification on their surfaces, whereas the short fragmented catheters did not. Conclusion The immunological reactions with silicone and the biodegradation of the material can be simulated in this animal model to study details of the pathophysiology of this process. Keywords Hydrocephalus • shunt catheter • silicone • immune reaction • complication • biodegradation R. Eymann (*) Department of Neurosurgery, Medical School, Saarland University, Kirrberger Street, Building 90, Homburg-Saar, Saarland 66421, Germany e-mail: [email protected] M. Ullrich Department of Neurosurgery, Unfallkrankenhaus Berlin, Warener Straße 7, Berlin D-12683, Germany e-mail: [email protected] K. Michael Department of Neurosurgery, Saarland University Medical School, Kirrberger Street, Building: 90.1, Homburg-Saar 66421, Germany
Introduction Use of silicone to manufacture hydrocephalus shunts has been one key to the successful introduction of modern shunt therapy. Although this material is one of the main causes of late shunt complications (1), and despite improvements in materials, devices and surgical techniques, no alternatives to silicone have been identified to this day. Based on series reviews and case reports, it is apparent that late shunt complications arise almost entirely due to problems associated with foreign body reactions on the silicone catheter and/or aging of the shunt material. There are two different types of reactions to silicone shunts: the degradation and mineralization of the catheter by itself and as an consequence to immune reactions several biological reactions. 1. Biodegradation and mineralization of the catheter (5) • Calcification with fixing scarring (1,10) • Fractures of the silicon catheter (1) • Corrosion of the material (1) 2. Potential consecutive biological reactions • Abdominal cerebrospinal fluid pseudo cysts (3,7,12) • Atrial thrombosis and cardiopulmonary complications (14,15) • Perforation of the catheter through the skin and organs such as bowel perforation (9,13) • Occlusion of the distal and ventricular catheter (4) • Increasing patients malpositioning during the growt
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