A method of determining disc space geometry with the use of an expandable trial having endplate-mapping capabilities. An expandable trial is inserted into the disc space and its height is adjusted to obtain the desired decompression and spinal alignment (which is typically confirmed with the use of CT or Fluoroscopic imaging). The endplate dome/geometry dome is then determined by one of the following three methods: a) direct imaging through the trial, b) balloon moldings filled with flowable in-situ fluid (for example, silicon, polyurethane, or PMMA) from superior/inferior endplates or c) light-based imaging through superior & inferior balloons.