[1] Lund Univ, Dept Orthoped, Lund, Sweden
[2] Boston Univ, Sch Med, Clin Epidemiol Res & Training Unit, Boston, MA 02118 USA
[3] Diakonhjemmet Hosp, Oslo, Norway
[4] Boston Univ, Sch Med, Dept Radiol, Boston, MA 02118 USA
[5] Klinikum Augsburg, Dept Radiol, Augsburg, Germany
[6] Brigham & Womens Hosp, Boston, MA 02115 USA