Treatment of patients with fractures of femur has a particular relevance in modern traumatology, especially in patients with polytrauma. The treatment of such fractures is complicated by the fact that it depends not only on the nature of the fracture, but also on the general condition of the patient. These fractures are caused by high-energy trauma, they have the tendency to be splintered or fragmented, and often accompanied by neurovascular complications, especially in the distal part. Such fractures are often accompanied by soft tissue damage. Purpose: improving the results of treatment of intra-and periarticular fractures of the distal femur in patients with polytrauma. Material and methods. In the present study, a prospective analysis of using conversion osteosynthesis in the treatment of 72 patients with intra-and periarticular fractures of the lower third of the femur patients with polytrauma, according to the ISS severity scale (ISS 17–40) was performed in a multidisciplinary hospital. Results. The most optimal time for conversion osteosynthesis to patients with polytrauma was 5–7 days, which prevented the occurrence of traumatic shock and prevented the occurrence of inflammatory complications in the postoperative period. Conclusion. The study confirmed the feasibility of conversion osteosynthesis in the treatment of patients with intra-and periarticular fractures of the lower third of the femur. The use of the technique of transferring the fixation of fragments by the external fixation to the internal osteosynthesis (conversion) contributed to a reduction in the duration of treatment of patients in the hospital with fractures of the long bones.