Fracture is break of bone complete or incomplete.
Major of the factures can be treated with immobilisation with proper CAST techniques and correct duration. 
Few conditions need to be operated either by closed or open techniques.
Conditions needing surgery/operation:
Open injuries/ large wound., very unstable #, #extending in joints, Grossly displaced or dislocated, multiple bone # etc.
With proper implants and technique of surgery, fractures can be treated very well