title: Comparison of orthodox versus off-optical axis endoscopic manipulations.
abstract: BACKGROUND
  During complex laparoscopic operations, the surgeon often has to use both instruments to one side of the telescope (off-optical axis work). This experimental study was undertaken to compare this orthodox versus the off-optical axis endoscopic manipulations regarding the performance parameters and motion analysis and muscle work of the surgeon's dominant upper limb.
  
  
  METHODS
  Ten surgeons participated in the study; each sutured 50-mm enterotomy in pig's small bowel in each of three setups: (1) in-optical axis manipulation (one instrument on either side of the laparoscope) (2) off-optical axis manipulation (both instruments on one side of the laparoscope to the dominant hand of the surgeon), and (3) off-optical axis manipulation both instruments on one side of the laparoscope on the nondominant side). The main outcome measures were the placement error score, execution time, leakage pressure, motion analysis, and telemetric electromyography parameters of the surgeon's dominant upper limb.
  
  
  RESULTS
  There was no significant difference in all parameters of performance, muscle work, and fatigue between setup 1 and setup 3. However, marked degradation of all parameters of performance with increased muscle work and fatigue was observed with setup 2 compared to setups 1 and 3. The reason for the deterioration with setup 2 is related to the altered "monitor display angle" which are different from the actual physical angles. With this setup, the instrument-to-target physical angle of 30 degrees appears on the screen as ?30 degrees and this disturbs both the manipulation and the azimuth angles obscuring the needle-tissue entry point. In addition, the instrument casts a shadow on its medial side and this tends to obscure the exact relations between instrument, needlepoint, and the tissue.
  
  
  CONCLUSIONS
  Off-optical axis work is a good alternative to the orthodox setup provided the instruments are placed to the nondominant hand. The marked degradation in performance encountered during off-optical axis work to the dominant hand of the surgeon is due to the resulting altered monitor display angles. The importance of these monitor display angles in influencing task performance has been previously overlooked.
authors.affiliation: Department of Surgery and Molecular Oncology and Surgical Skills Unit, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland.
authors.forename: T A
authors.initials: TA
authors.lastname: Emam
authors.forename: G
authors.initials: G
authors.lastname: Hanna
authors.forename: A
authors.initials: A
authors.lastname: Cuschieri
mesh_terms: D000818:Animals; D007839:Functional Laterality; D013502:General Surgery / Q000193:education*; D006801:Humans; D007396:Internship and Residency; D020706:Laparoscopes; D008328:Man-Machine Systems; D018763:Muscle Fatigue; D013536:Suture Techniques; D013552:Swine; D013647:Task Performance and Analysis