gms | German Medical Science

60th Annual Meeting of the German Society of Neurosurgery (DGNC)
Joint Meeting with the Benelux countries and Bulgaria

German Society of Neurosurgery (DGNC)

24 - 27 May 2009, Münster

Breakage of the adjustment helix in four adjustable Medos-Hakim valves

Meeting Abstract

  • K. Dette - Klinik für Neurochirurgie, Universitätsklinikum Heidelberg
  • F. Ebinger - Abteilung für Pädiatrische Neurologie des Universitätsklinikums Heidelberg
  • A. Unterberg - Klinik für Neurochirurgie, Universitätsklinikum Heidelberg
  • A. Aschoff - Klinik für Neurochirurgie, Universitätsklinikum Heidelberg

Deutsche Gesellschaft für Neurochirurgie. 60. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit den Benelux-Ländern und Bulgarien. Münster, 24.-27.05.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. DocMO.15-09

doi: 10.3205/09dgnc110, urn:nbn:de:0183-09dgnc1109

Published: May 20, 2009

© 2009 Dette et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



Objective: The filigree adjustment rotor of the Codman-Medos (Medos-P) valve has a relatively soft silicone and plastic housing. Inadequate pumping manoeuvres and shocks are a risk for breaking out or decentering the rotor.

There are only a few reports in the literature about breakage of Medos-P rotors. In all cases the dislocation of the adjustment helix results in an impossibility of readjustment. In addition, an over- or underdrainage may occur in these cases.

Methods: In over 500 implantations between 1990 and 2008, we observed four specimens with a damage of the proximal rotor and three valves with breakage of the distal valve. The failure was diagnosed by clinical shunt dysfunction and x-ray-examination. The verification was made by lab investigation with magnification glasses and macro-photos.

Results: No patient had a relevant head trauma. In one case the valve was powerfully pumped by a non-neurosurgeon. Two patients showed symptoms of overdrainage (headaches in vertical body position) without subdural effusions or haematoma. One patient presented with a chronic subdural haematoma requiring surgical insertion of a drain. In all cases, the helix of the valve was dislocated in the pumping chamber. Surgical revision was necessary in all cases. The distal valve produces 10 mm H2O resistance only, therefore fractures can be clinically inapparent.

Conclusions: The identical defects in these cases suggest that the housing of the Medos-P-valves is mechanically too weak and can be destroyed even by minor shocks of daily life or pumping manoeuvres.

We propose a reinforcement of the valve body and mechanics, e.g. by titanium or more stable plastics. In cases of overdrainage, a damage of the valve must be thought of.