title: The Mechanics of Brow-Suspension Ptosis Repair: A Comparative Study of Fox Pentagon and Crawford Triangle Techniques.
abstract: OBJECTIVE
  To perform quantitative analysis of the most commonly used brow-suspension configurations.
  
  
  METHODS
  The inflection positions for Fox pentagon and Crawford triangle configurations were marked on 49 healthy volunteers (male and female) and photographs taken in 3 states: "normal," "closed," and "raised." The skin marks were measured vectorially with respect to the medial canthus, and displacement changes were evaluated for "normal-to-closed" ("blinking") and from "closed-to-raised" ("eye-opening") states. The distance between a pair of inflection marks, representing the approximate path of sling configurations, were also measured and analyzed in relation to the mechanical properties of a variety of synthetic brow-suspension materials.
  
  
  RESULTS
  "Blinking" resulted in the greatest displacement in the medial eyelid incision, resulting in the greatest strain on the line connecting the medial eyelid and medial brow inflections. No significant differences in the strains for individual lines were found between the Fox and Crawford techniques, although the former shows a significantly lower overall strain in the whole loop than the latter. The displacements of some inflections and of the strains of a few lines differed significantly in men and women.
  
  
  CONCLUSIONS
  Within the scope of this study, the blinking action was shown to result in the maximum strain of ~40%, which lies within the elastic region of stress-strain curves for some commonly used synthetic brow-suspension materials. No one method was statistically superior, although the Fox pentagon gave a significantly lower overall strain when the sling material was assumed to move somewhat around the inflections within a closed loop.
authors.affiliation: *Department of Mechanical Engineering, University College London, Torrington Place, London, United Kingdom; †Department of Materials Science and Metallurgy, Cambridge Centre for Medical Materials, University of Cambridge, Cambridge, United Kingdom; ‡BMI Goring Hall Hospital, West Sussex, United Kingdom; and §UCL Institute of Ophthalmology NIHR Biomedical Research Centre for Ophthalmology, London, United Kingdom.
authors.forename: Kyung-Ah
authors.initials: KA
authors.lastname: Kwon
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Shipley
authors.forename: Mohan
authors.initials: M
authors.lastname: Edirisinghe
authors.forename: Serena M
authors.initials: SM
authors.lastname: Best
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Cameron
authors.forename: Cornelia
authors.initials: C
authors.lastname: Poitelea
authors.forename: Geoffrey E
authors.initials: GE
authors.lastname: Rose
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Ezra
mesh_terms: D000328:Adult; D000368:Aged; D001763:Blepharoptosis / Q000601:surgery*; D001767:Blinking / Q000502:physiology; D005143:Eyelids / Q000601:surgery*; D005260:Female; D005546:Forehead / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D013536:Suture Techniques