gms | German Medical Science

62nd Annual Meeting of the German Society of Neurosurgery (DGNC)
Joint Meeting with the Polish Society of Neurosurgeons (PNCH)

German Society of Neurosurgery (DGNC)

7 - 11 May 2011, Hamburg

Bench-tests of 941 hydrocephalus valves – conclusions after 23 years

Meeting Abstract

  • A. Aschoff - Department of Neurosurgery, University of Heidelberg, Heidelberg
  • M. Akbar - Department of Orthopaedics, University of Heidelberg, Heidelberg
  • D. Biedermann - Department of Neurosurgery, University of Heidelberg, Heidelberg
  • J. Ludwig - Department of Neurosurgery, University of Heidelberg, Heidelberg
  • E. Tajeh - Department of Neurosurgery, University of Heidelberg, Heidelberg
  • D. Hertle - Department of Neurosurgery, University of Heidelberg, Heidelberg

Deutsche Gesellschaft für Neurochirurgie. Polnische Gesellschaft für Neurochirurgen. 62. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit der Polnischen Gesellschaft für Neurochirurgen (PNCH). Hamburg, 07.-11.05.2011. Düsseldorf: German Medical Science GMS Publishing House; 2011. DocMO.03.07

DOI: 10.3205/11dgnc007, URN: urn:nbn:de:0183-11dgnc0073

Published: April 28, 2011

© 2011 Aschoff et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.


Outline

Text

Objective: Shunts should keep the ICP within the physiological ranges unaffected by body position, subcutaneous pressure, valve body deformations, vasogenic intracranial volume changes and other potentially disturbing factors.

Methods: Within 23 years we tested in vitro 941 hydrocephalus valves, of them 90 different designs, 385 new and 529 probes explanted after max. 34 years. The sample consisted of 212 proximal and 24 distal slit valves (17/10 designs), 106 diaphragm (20), 161 simple, 197 adjustable and 206 gravitational ball valves (9/10/11 different versions) and 36 other valves (8 designs). The accuracy was measured conform to ISO 7191:1989. 179 specimens had long-term-tests, of them 121 for 360–500 days. Up to 37 subtests were dedicated to hysteresis, flow dependent on pressure, reflux, susceptibility to external fluid pressure, vectorial forces, flection, temperature, protein (500 mg/ml), air bubbles, pulsations, pumping and sterilization. Adjustable valves were exposed to MRI 1.0-4.0 T and tests of the adjustment (linearity, tolerance of decentration). Gravitational valves were checked varying the angle of verticalization and simulating common body movements.

Results: In the sample with complete test-battery only 36% of all valves met the manufacturer’s specifications. 24% showed deviations of ± 21 - 50 mm H2O, 15% of ± 51 - 80 mm H2O and 15 % of ± 81 - 135 mm H2O. 13% failed up to 1446 mm H2O. Ball-valves were superior with 61% good and 21% fair results. After 90 days 72% showed drifts, after 365 days 89%. 32 % of the valves were not reflux-resistant, 29% irritable by external fluid pressure (resistance-increase up to 3000%!), 50% susceptible to vectorial forces and 56% to flections. - In upright position 81% showed over-drainage (>100 ml/h), 9% had an insufficient flow (<15 ml/h). Adjustable valves showed no physiological flow-rates in horizontal and upright position; many show a lack of robustness and in long-term dysfunctions of adjustments. ASDs had problems with safety, Orbis-Sigma with accuracy. The best approximation to physiological functions showed gravitational ball valves (± adjustable).

Conclusions: 1. The majority of valves still showed deficits in accuracy, long-term-stability, safety and adequate flow-rates either in upright or in horizontal position. 2. Intelligent shunts are no longer a ”Mission Impossible”.