title: More malfunctioning Medos Hakim programmable valves: cause for concern?
abstract: OBJECTIVE
  In recent years, the authors have noticed a growing number of programmable valve defects at their institution. Therefore, they conducted this study to evaluate the increased incidence of malfunctioning valves.
  
  
  METHODS
  They investigated all revisions that had been performed at their institution between 1994 and 2010 for dislodgement of the stator of a standard Medos Hakim programmable valve with a prechamber.
  
  
  RESULTS
  Fifteen valves were removed because of dislodged stators. The valves had been implanted between May 16, 1993, and December 27, 2002, and were explanted between February 19, 2006, and January 22, 2010. Thus, the valves had been in place for a mean period of 11 years (median 11 years, range 7-14 years). The percentage of dislodged stators was almost 3% (15 of 546 valves). Particularly noteworthy is that all malfunctioning valves were found in children who had been younger than 1 year of age at the time of implantation.
  
  
  CONCLUSIONS
  Medos Hakim programmable valve malfunctions are rare events but should receive careful attention. When the pressure setting cannot be adjusted, a malfunction should always be suspected and radiographic imaging should be performed to assess the valve. Stator dislodgement is the most serious form of valve adjustment failure.
authors: Department of Neurosurgery, German Armed Forces Hospital of Ulm, Germany. UweMaxMauer@bundeswehr.org
authors: Uwe Max
authors: UM
authors: Mauer
authors: Ulrich
authors: U
authors: Kunz
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002557:Cerebrospinal Fluid Shunts / Q000295:instrumentation*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006849:Hydrocephalus / Q000601:surgery*; D007223:Infant; D008297:Male; D011475:Prosthesis Failure; D012086:Reoperation