[1] Lund Univ, Dept Clin Sci Malmo Social Med & Global Hlth, Malmo, Sweden
[2] Lund Univ, Dept Hlth Sci, Hlth Sci Ctr, Lund, Sweden
[3] Skane Univ Hosp, Natl Ctr Qual Registers, Lund, Sweden
[4] Skane Univ Hosp, Dept Orthopaed, S-20503 Malmo, Sweden
[5] Lund Univ, Dept Clin Sci Lund, Div Paediat, Lund, Sweden