Radiographic changes in cortical bone after intramedullary nailing. An experimental investigation on rabbits.

Transverse osteotomies of the midshaft of the tibia in 75 rabbits were stabilized with intramedullary nails which prevented rotational instability. In a further 36 animals intramedullary nailing was performed without preceding osteotomy. The animals were able to move freely immediately after the operation without any supporting case or splint. The structural changes in the bones were analysed radiographically 3 to 24 weeks after the operation. Fracture repair was accompanied by moderate periosteal callus formation and remodelling of the callus was seen from 9 weeks on. A sleeve of new endosteal bone surrounding the nail was found after 12 weeks. Porotic transformation of the diaphyseal cortical bone was seen in both osteotomized and non-osteotomized bones from 12 weeks onwards. It is concluded that intramedullary nailing provides favourable conditions for fracture repair and enables accurate radiographic assessment of the healing. Attention is focused on the causes and features of secondary porotic transformation of the cortical bone after intramedullary nailing.