Wiegers, E. J. A., Sewalt, C. A., Venema, E., Schep, N. W. L., Verhaar, J. A. N. ., Lingsma, H. F. and Den Hartog, D. . (2019) “The volume–outcome relationship for hip fractures: a systematic review and meta-analysis of 2,023,469 patients”, Acta Orthopaedica, 90(1), pp. 26–32. doi: 10.1080/17453674.2018.1545383.