z-Value development of DAH annulus size for subgroups over time. Black lines delineate patients younger than 10 years with a DAH smaller than 15 mm at implantation, green—patients younger than 10 years with a DAH bigger than 15 mm and red—patients older than 10 years. z-Value development of DAH annulus size over time. Package labelled annulus diameter was rounded to z-value integers, and each postoperative measurement is again expressed as a z-value according to the actual height and weight of the patient. A loess fit curve was then drawn for each implant size group. The green area shows the normal range in the middle of which the lines should converge.