title: Intra-operative quantification of the surgical gesture in orbital surgery: application to the proptosis reduction.
abstract: BACKGROUND
  Proptosis is characterized by a protrusion of the eyeball due to an increase of the orbital tissue volume. To recover a normal eyeball positioning, the most frequent surgical technique consists in the osteotomy of orbital walls combined with a loading on the eyeball to initiate tissue decompression. The first biomechanical models dealing with proptosis reduction, validated in one patient, have been previously proposed by the authors.
  
  
  METHODS
  This paper proposed an experimental method to quantify the intra-operative clinical gesture in proptosis reduction, and the pilot study concerned one clinical case. The eyeball's backward displacement was measured by an optical 3D localizer and the load applied by the surgeon was simultaneously measured by a custom-made force gauge. Quasi-static stiffness of the intra-orbital content was evaluated.
  
  
  RESULTS
  The average values for the whole experiment was 16 N (SD: 3N) for the force exerted by the surgeon and 9 mm (SD: 4mm) for the eyeball backward displacement. The averaged quasi-static stiffness of the orbital content was evaluated to 2.4N/mm (SD: 1.2) and showed a global decrease of 45% post-operatively.
  
  
  CONCLUSIONS
  The protocol and the associated custom-designed devices allowed loads, induced displacements and macroscopic stiffness of the orbital content to be measured intra-operatively. The clinical relevance has been demonstrated in a pilot study. To our knowledge, no study has been published allowing the clinical gesture in proptosis reduction to be quantified intra-operatively. Associating an enlarged database and validated patient-related predictive models will reinforce the surgical efficiency and patient comfort contributing to diagnosis and intra-operative guidance.
authors.affiliation: TIMC-IMAG Laboratory, UMR CNRS 5525, Faculté de Médecine, 38706 La Tronche, France.
authors.forename: V
authors.initials: V
authors.lastname: Luboz
authors.forename: P
authors.initials: P
authors.lastname: Swider
authors.forename: D
authors.initials: D
authors.lastname: Ambard
authors.forename: F
authors.initials: F
authors.lastname: Boutault
authors.forename: Y
authors.initials: Y
authors.lastname: Payan
mesh_terms: D000465:Algorithms; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D005094:Exophthalmos / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D025321:Surgery, Computer-Assisted