I presume there would have been X rays taken at post mortem. If he did have plates and screws these would have been identified. PV ordered X rays when first contacted.
I knew it wouldn't sit comfortably with you! Its too simple, straightforward, plausible, ticks all the boxes and doesn't involve thousands of conspiracy theories!

The main objective of a PM is to determine cause of death. Given all victims sustained more than one gunshot wound, 8 in the case of NB, why would it follow that complete body xrays would be undertaken? Esepcially if he could determine cause of death from one or more of the gunshot wounds.
Not necessarily. If xrays were taken in that area some metals are difficult to detect and/or can be hidden by bone.Where's the evidence Dr Vanezis ordered xrays? Ordered them from where?
He does refer to observing a fragmented bullet on a radiograph which he was unable to locate in the body cavity.