Here is a simulation of the surgery using Sperm Whale vertebra. You can clearly see that the disk has been removed in the upper joint and the disk is diseased in the lower joint.
This alternate view of a dolphin vertebra clearly shows the channel for the spinal cord. This channel does not exist in a sperm whale. We can only assume the great distances from the sperm whale head to the sperm whale tail has forced the larger whale to use a distributed control system, with special tail-control, flipper-control, and internal-organ-control systems mounted locally.