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Cortical bone subjected to compression by screw threads retains its integrity and is not resorbed. Screws which generate compression at the interface of their threads with bone can be expected to provide adequate fixation until bone union occurs.

To evaluate treatment of nonunions or pseudarthrosis in humans by pulsating electromagnetic fields (PEMF), the authors tested the method in four- to six-year-old beagle dogs with midshaft osteotomies of both ulnae. This type of osteotomy in dogs leads to nonunion. After surgery one foreleg of each dog was stimulated for an average of 25 days; the second foreleg served as a control. Subsequently all ulnae were harvested, radiographs were obtained, and the stiffness of the callus was mechanically tested. Thus, the reputed efficiency is not confirmed by controlled experiments on dogs. The stimulated bones were neither radiologically nor mechanically superior to the controls.

Corrective osteotomy of the long bones may be required in patients with Paget's disease. Experiments on rabbits suggest that the safety of the procedures is of concern while the patient receives Calcitonin. Twenty-four rabbits were divided into 4 groups of 6 animals. Half of each group received maintenance doses of Calcitonin subcutaneously. In all animals the left and right ulnae were osteotomized through middiaphysis. The right ulna was fixed with a "mini" dynamic compression plate. The left ulna was not immobilized. Each group of animals was sacrificed at successive intervals of 3 weeks. Histologically, no difference was found in the healing of the fracture of test or control animals. Radiographically, the fracture line persisted longer in animals receiving Calcitonin (6 weeks vs 3 weeks). All fractures healed by 9 weeks. The fracture line disappeared more rapidly in all the immobilized bones. Based on these observations, administration of Calcitonin is not a contraindication for corrective osteotomy in Paget's disease. Osteotomies should be rigidly fixed to maintain the correction achieved surgically until healing is established.

Movement between screw threads and bone inhibits bone formation, revascularization and remodeling of dead bone. Movement causes the screw to become enveloped by fibrous tissue in response to necrosis and resorption of adjacent dead cortical bone. This results in a radiologically discernible radiolucent "halo" about the screw, a certain sign of screw loosening.