title: Electromyographic investigation on handling forces of mechanically counterbalanced and sensor-servomotor-supported surgical microscopes.
abstract: BACKGROUND
  Recent developments in sensor-servomotor-driven microscopes again initiated a discussion on the value of such technology for practical use in neurosurgery. The need for less force in moving a motor-supported microscope is advantageous. However, questions remain if well-known difficulties in the past such as resonance phenomenon, loss of natural feeling, and unequal handling forces in different situations have been overcome by the new generation of sensor-servo-supported surgical microscopes.
  
  
  METHODS
  Handling forces of a mechanically counterbalanced neurosurgical microscope (Zeiss NC4, Zeiss, Oberkochen, Germany) were compared with those of a sensor-servo-supported neurosurgical microscope (Moeller HiR 20-1000, Moeller, Wedel, Germany). Handling forces were correlated with the surface electromyogram measurement of the muscle activity of 4 neurosurgeons. The activity of the forearm muscles was measured while handling the 2 different microscopes in standardized tests.
  
  
  RESULTS
  The electrophysiologic measurement revealed that significantly less muscle activity was required to handle the sensor-servo-driven microscope in all directions. The untrained surgeons profited less than the skilled ones. Differences were most evident with disbalanced microscopes.
  
  
  CONCLUSIONS
  With this technology, the neurosurgeons exerted less effort, especially in strenuous test situations where the single-handed use of the microscope was mandatory. The reduced muscle forces that move the sensor-servo-type microscope and the continuously balanced state that might help prevent unwanted correction movements will ease intraoperative handling in general.
authors.affiliation: Department of Neurosurgery, BG-Hospital-Bergmannstrost, 06112 Halle, Germany. hoell@bergmannstrost.com
authors.forename: Thomas
authors.initials: T
authors.lastname: Hoell
authors.forename: Michaela
authors.initials: M
authors.lastname: Nagel
authors.forename: G
authors.initials: G
authors.lastname: Huschak
authors.forename: Andre
authors.initials: A
authors.lastname: Beier
authors.forename: Hans Joerg
authors.initials: HJ
authors.lastname: Meisel
mesh_terms: D001132:Arm / Q000502:physiology*; D001696:Biomechanical Phenomena; D004576:Electromyography; D006804:Ergonomics / Q000592:standards*; D006801:Humans; D008853:Microscopy / Q000295:instrumentation*; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D019635:Neurosurgical Procedures / Q000295:instrumentation*