1 Department of Development and Regeneration, KU Leuven, Leuven, Belgium.
2 Department of Biomedical Data Sciences, Leiden University Medical Center (LUMC), Leiden, the Netherlands.
3 Centre for Statistics in Medicine, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom.
4 Oxford University Hospitals NHS Foundation Trust, Oxford, United Kingdom.