Answer to the Letter to the Editor of C. Birkenmaier concerning “Rehydration of a degenerated disc on MRI synchronized with transition of Modic changes following stand-alone XLIF” by K. Kita, T. Sakai, M. Abe, Y. Takata and K. Sairyo (Eur Spine J; 2017). doi:10.1007/s00586-017-4945-6