I have ao spine internal fixation t12 - l1 for burst fracture15 years ago. can bolts/rods fall into hip or groin as i have pain from l1 down to groin.

Back pain: Less likely from bolts or rods dropping. If you have a spinal disease at a level, you can have pain below that level because of cord compression . Please get examined by a doctor asap.

Most unlikely!: The screws/rods used are unlikely to move that much. I believe you might be getting nerve impingement from the arthritis or a disc lesion that's causing your symptoms. You should see a spine surgeon so it can be investigated properly.