[1] Fac Med Broussais Hotel Dieu, Dept Publ Hlth, F-75006 Paris, France
[2] Assistance Publ Hop Paris, Lariboisiere Hosp, Dept Orthoped, Paris, France
[3] Assistance Publ Hop Paris, Bichat Hosp, Epidemiol Unit, Paris, France
[4] Assistance Publ Hop Paris, Henri Mondor Hosp, Dept Biostat & Med Informat, Creteil, France