How can you manage back pain after you've broken your third and fourth lumbar?

Depends on the type: Of injury & fracture as well as your age, health, bone density, lifestyle ( exercise routine, smoking, weight), underlying medical issues & how your fractures were treated: with /without surgery. Fractures heal but it can depend on how they heal & under what conditions lead to fractures in first place. Also, were there any associated injuries or nerve issues. This should be reviewed by your doc.