title: Analysis of a severe head injury in World Cup alpine skiing.
abstract: Traumatic brain injury (TBI) is the leading cause of death in alpine skiing. It has been found that helmet use can reduce the incidence of head injuries between 15% and 60%. However, knowledge on optimal helmet performance criteria in World Cup alpine skiing is currently limited owing to the lack of biomechanical data from real crash situations.
  
  
  OBJECTIVE
  This study aimed to estimate impact velocities in a severe TBI case in World Cup alpine skiing.
  
  
  METHODS
  Video sequences from a TBI case in World Cup alpine skiing were analyzed using a model-based image matching technique. Video sequences from four camera views were obtained in full high-definition (1080p) format. A three-dimensional model of the course was built based on accurate measurements of piste landmarks and matched to the background video footage using the animation software Poser 4. A trunk-neck-head model was used for tracking the skier's trajectory.
  
  
  RESULTS
  Immediately before head impact, the downward velocity component was estimated to be 8 m·s⁻¹. After impact, the upward velocity was 3 m·s⁻¹, whereas the velocity parallel to the slope surface was reduced from 33 m·s⁻¹ to 22 m·s⁻¹. The frontal plane angular velocity of the head changed from 80 rad·s⁻¹ left tilt immediately before impact to 20 rad·s⁻¹ right tilt immediately after impact.
  
  
  CONCLUSIONS
  A unique combination of high-definition video footage and accurate measurements of landmarks in the slope made possible a high-quality analysis of head impact velocity in a severe TBI case. The estimates can provide crucial information on how to prevent TBI through helmet performance criteria and design.
authors.affiliation: 1Oslo Sports Trauma Research Center, Oslo, NORWAY; 2Section of Orthopedic Surgery, School of Medicine, Tokyo Medical and Dental University Hospital, Tokyo, JAPAN; 3Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, NORWAY; 4Royal Institute of Technology, Stockholm, SWEDEN; 5Australian Centre for Research into Injury in Sport and its Prevention (ACRISP), Federation University Australia, Ballarat, AUSTRALIA; 6Department of Sport Science, University of Innsbruck, Innsbruck, AUSTRIA; 7Department of Sport and Exercise Science, University of Salzburg, Salzburg, AUSTRIA; 8Aspetar Orthopaedic and Sports Medicine Hospital, Doha, QATAR.
authors.forename: Junya
authors.initials: J
authors.lastname: Yamazaki
authors.forename: Matthias
authors.initials: M
authors.lastname: Gilgien
authors.forename: Svein
authors.initials: S
authors.lastname: Kleiven
authors.forename: Andrew S
authors.initials: AS
authors.lastname: McIntosh
authors.forename: Werner
authors.initials: W
authors.lastname: Nachbauer
authors.forename: Erich
authors.initials: E
authors.lastname: Müller
authors.forename: Tone
authors.initials: T
authors.lastname: Bere
authors.forename: Roald
authors.initials: R
authors.lastname: Bahr
authors.forename: Tron
authors.initials: T
authors.lastname: Krosshaug
mesh_terms: D000054:Acceleration; D000328:Adult; D001696:Biomechanical Phenomena; D006259:Craniocerebral Trauma / Q000209:etiology* / Q000517:prevention & control; D006260:Head Protective Devices; D006801:Humans; D008297:Male; D012307:Risk Factors; D012865:Skiing / Q000293:injuries*; D014741:Video Recording