The paper presents our observations of femur shaft fractures healing treated by closed locked intramedullary nailing. The method is, from biological and biomechanical point of view, adventageous connection of conservative fracture treatment and operative method fulfilling stable osteosynthesis requirements and standards. Callus formation in the vicinity of fracture site confirms some elasticity of stabilization, even in spite of static locking. The indications to dynamization should be considered thoroughly. In bone healing stimulation bone marrow injection in the fracture site is efficient. The high effectivenes of method together with low number of complications decides that it almost entirealy replaced plate osteosynthesis.