[1] Hosp Infantil Mexico Dr Federico Gomez, Clin Epidemiol Res Unit, Mexico City, DF, Mexico
[2] Univ Nacl Autonoma Mexico, Fac Med, Mexico City, DF, Mexico
[3] Dermatol Ctr Dr Ladislao de La Pascua, Mexico City, DF, Mexico
[4] Univ Oxford, Nuffield Dept Orthopaed Rheumatol & Musculoskelet, Oxford, England
[5] Reg Manager IOF Latin Amer, Buenos Aires, DF, Argentina
[6] High Specialty Traumatol & Orthopaed Hosp Lomas V, Med Unit, Mexican Inst Social Secur, Mexico City, DF, Mexico