Does anyone have any information about breaking a fibula?

If only fibula is fractured at the upper third (may be even spiral fracture) it is not of much consequence and it will be healing by 3-4 weeks. But you have to be doubly sure that lower end is not involved. When you say that ankle is sprained, there might be some injury to lower end of fibula as well. If this is so, it will take a long time - 6-8 weeks and that too after an expert orthopedics surgeon intervenes. So better consult an expert orthopaedician.