title: Surgical instrument force exerted during endoscopic sinus surgery: differences within the ethmoid sinus complex.
abstract: BACKGROUND
  Endoscopic sinus surgery (ESS) has been the most important technical advance in surgical rhinology in the last 25 years. The technique is now used beyond its initial sinus confines but knowledge of the forces required to perform ESS is limited. Greater understanding of these forces will lead to improved surgical training and safety. The aim of this study was to quantify the magnitude of the forces exerted during punch osteotomy of the bony lamella of the paranasal sinuses and surrounding bony structures during ESS.
  
  
  METHODS
  Fifteen formalin-fixed cadaveric heads underwent simulated ESS. Peak axial forces were measured using a pair of modified Blakesley forceps. Measurements were recorded during osteotomy of the paranasal sinus complex, skull base, and crests of the optic nerve and internal carotid artery. Statistical comparison between the mean forces was performed.
  
  
  RESULTS
  A mean force of 6.06 N was required to breach the lamellae of the ethmoid sinus complex. This was significantly less than the mean force required to breach the skull base, excluding the olfactory cleft (17.80 N; p < 0.0001), crests of the optic nerve (15.43 N; p < 0.001), and internal carotid artery (13.15 N; p < 0.001). There was no significant difference between the ethmoid lamella and the lamina papyracea (6.13; p = 0.67).
  
  
  CONCLUSIONS
  Significantly greater force was required to breach the skull base and other safety critical areas encountered in ESS, than the bony lamellae of the ethmoid sinus complex. Although this result is reassuring, in vivo studies are now required to validate this relationship in the operative patient.
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, University of Dundee, Ninewells Hospital, Dundee, United Kingdom. pxross@dundee.ac.uk
authors.forename: Peter D
authors.initials: PD
authors.lastname: Ross
authors.forename: Paul
authors.initials: P
authors.lastname: Joice
authors.forename: Ramez G
authors.initials: RG
authors.lastname: Nassif
authors.forename: Paul S
authors.initials: PS
authors.lastname: White
mesh_terms: D002102:Cadaver; D004724:Endoscopy; D005005:Ethmoid Sinus / Q000033:anatomy & histology / Q000601:surgery*; D006801:Humans; D010027:Osteotomy / Q000295:instrumentation / Q000379:methods; D010256:Paranasal Sinuses / Q000033:anatomy & histology / Q000601:surgery*; D011364:Professional Practice; D019291:Skull Base / Q000601:surgery; D013314:Stress, Mechanical; D013525:Surgical Instruments