Laboratory performance of single-piece ventriculoperitoneal shunts with distal slit-valve control

Three different types of single-piece ventriculoperitoneal shunts with distal slit-valve control (Codman Unishunt, Codman Unishunt with chambers, and Heyer-Schulte one-piece shunt) in their low- and medium-pressure forms were assessed in the laboratory by both static and dynamic tests. A statistical analysis of variance showed large differences in performance which were not confined to the different pressure ranges as may have been expected. Substantial variation occurred between nominally identical shunts and between identically rated shunts of different makes. Guidelines for an industry standard are proposed.