I’m far from an orthopaedic specialist, just someone who has lived a life that has given me more broken bones than most.
On the 2nd of April 2013 I got T8 burst fracture from a bad skydiving landing. Discharged with a body brace after two weeks of full immobilisation. I kept wearing the brace, but kept moving as much as possible, walking as much as I could bear as soon as possible and starting very light jogging about a month after the break. I finished my first 70.3 in May this year (just a year over the injury) will do my first full distance in September, and have zero sign of ever having broken my back (except some tightness around where the break was when I do longer runs >20km).
I agree that keeping on moving is key, over the years I’ve broken each arm, each leg and my back, and the only one that took a long time to heal was the simplest arm break where I wore the cast for the entire time recommended by the doctor. For the rest, I was moving earlier than advised (especially careful in each case to avoid re-brake caused by shock loading the injury), but keeping the injured limbs as mobile as possible, trimming the cast back slowly to back the support off gradually prevented full wasting of the muscles, ligaments and tendons in each of the rest. I may have lucky genetics wrt bone healing, but I was running pain free 6 weeks after a bad calcaneous fracture, and I was back to BASE jumping within 2 months (a pre-triathlon life that I have since retired from) - the prognosis was 6 months at best and maybe never running again.
I have been particularly lucky, and by chance have had field leading physicians look after me for a calcaneous break and my back break. Both advised keeping mobile as much as I could bear. When pressed, one (off the record) suggested that time frames for splinting and casting breaks are conservative and that doctors are bound by liability and risk management to cater for those that don’t heal so well, a secondary purpose of casts is to remind the patient to treat injuries extra careful.
Key take home, is that muscles, ligaments and bones evolved to respond positively to stress, so as long as a healthy callus forms around the joint (steer clear of anti-inflammatories like ibuprofen, aspirin etc that can impede callus formation and therefore delay bone healing) like exercise should speed up your healing. You just have to be careful that you don’t re-break the old injury so avoid sudden jolts and shocks at all costs.
But your break could be different. Mine vertebral body was shattered, but the pieces stayed together because I was training my core heavily in the months leading up to the accident. And being a T8, it was well supported by my ribs etc. Your doctor should be able to give you an idea of how stable your break is.
I’m not a doctor so take my advice with a grain of salt and definitely talk to your doctor. If you find a good doctor that will talk openly, you might get similar advice.
Good luck with the break man. I hope you’re as lucky as I have been!