fastening of the ends of fragmented bone after osteotomy and in the treatment of fractures in order to realign and secure the fragments in a position that would promote callus formation. Osteosynthesis can be closed, involving the fixation of bone fragments by mechanical means: wires are passed through the fragments at some distance from the line of fracture and held in repositioning devices, such as rings and arches. With open osteosynthesis, the fragments are secured with metal or plastic devices that are introduced into the canals of tubular bones; plates can be screwed to the cortical layers of the bone. Osteosynthesis can be performed in one of several stages, but the operation must be closed if several stages are involved. It can also be performed with bone grafts: autografts use bone taken from the patient himself; homografts—from preserved cadaver tissues; and heterografts—from an animal of another species.

Osteosynthesis can be stable or unstable. The former ensures the reliable fixation of fragments in apposition and does not require additional external fixation with a cast or some other means. Unstable osteosynthesis requires additional external fixation until the fragments are joined. Compression osteosynthesis—a special kind of osteosynthesis involving compression of the fragments along the bone axis—has no clear advantage over the ordinary types of osteosynthesis inasmuch as the fragments do not join faster and the quality of the union is not better.

Osteosynthesis is performed under local or general anesthesia in specialized medical institutions. During wartime, osteosynthesis can only be done in a specialized field hospital.