[1] Hosp Univ Vall Hebron, Paediat Orthopaed Unit, Barcelona, Spain
[2] Univ Autonoma Barcelona, Barcelona, Spain
[3] HFR Hop Cantonal, Dept Rheumatol Phys Med & Rehabil, Fribourg, Switzerland
[4] Hosp Univ Vall Hebron, Spine Unit, Barcelona, Spain
[5] Hosp del Mar, CIBER Epidemiol & Publ Hlth CIBERESP, IMIM, Hlth Serv Res Grp,Res Inst, Barcelona, Spain
[6] Catalan Agcy Hlth Informat Evaluat & Qual, Barcelona, Spain
[7] Publ Hlth Agcy Barcelona Inst Biomed Res IIB St P, Barcelona, Spain
[8] Hop Univ Geneve, Div Gen Med Rehabil, Geneva, Switzerland
[9] Hop Univ Geneve, Div Clin Pharmacol & Toxicol, Geneva, Switzerland