[1] Univ Zurich Hosp, Div Trauma Surg, Zurich, Switzerland
[2] Univ Maryland, Sch Med, Dept Orthopaed, R Adams Cowley Shock Trauma Ctr, Suite 300,110 S Paca St, Baltimore, MD 21201 USA
[3] McMaster Univ, Dept Clin Epidemiol & Biostat, Hamilton, ON, Canada
[4] McMaster Univ, Dept Surg, Div Orthopaed Surg, Hamilton, ON, Canada
[5] Ctr Hlth Evaluat & Outcome Sci, Vancouver, BC, Canada
[6] Univ British Columbia, Sch Populat & Publ Hlth, Vancouver, BC, Canada