Are sagging and incomplete implant removal a big concern with removing jaw angle MEDPOR implants? (photos)

I had jaw angle MEDPOR custom implant done in 2016. I would like to have them removed in order to have a orthognatic surgery. Surgeon only will do surgery if the medpor is removed Is it possible to remove the entire implants in one procedure? I read some reports that the surgeon was not able to remove the entire medpor implant and pieces of the implant were left in. Finally, would sagging and irregularities be a big concern due to extraction of considerable soft tissue attached to the implant?