It is my understanding that fusion of vertebrae cannot be seen on X-rays but that thickening/solidifying between vertebrae can be seen which MAY BE fusion, but that fusion itself can not be definitively diagnosed or decided. Fusion can be decided/diagnosed at a surgery to stress the joining of the vertebrae or in the negative sense, when someone w/ spinal surgery has sudden pain and the X-ray shows non-junction.
Adult Onset Degenerative Scoliosis @65, 25* T & 36* L w/ 11.2 cm coronal balance; T kyphosis 90*; Severe disc degen T & L stenosis
2013: T3- S1 Fusion w/ ALIF L4-S1/XLIF L2-4, PSF T4-S1 in 2 surgeries
2014: Hernia @ ALIF repaired; Emergency surgery for Spinal Cord Injury at T4,5 sec to PJK
2015: Revision Broken Bil T & L rods and no fusion: 2 revision surgeries; hardware P. Acnes infection
2016: Ant/Lat Lumbar diskectomy w/ 5 cages + BMP