Effect of unreamed, limited reamed, and standard reamed intramedullary nailing on cortical bone porosity and new bone formation

Objective: To compare the effects of unreamed nail insertion and reamed nai l insertion with limited and standard canal reaming on cortical bone porosi ty and new bone formation. Design: A canine segmental tibial fracture was created in fifteen adult dog s. The tibiae were stabilized with a statically locked 6.5-millimeter intra medullary nail without prior canal reaming (n = 5), after limited reaming t o 7.0 millimeters (n = 5), or after standard canal reaming to 9.0 millimete rs (n = 5). Porosity, new bone formation, and the mineral apposition rate o f cortical bone were directly compared between the three nailing techniques . Results: A significant increase in cortical bone porosity and new bone form ation was seen in all three groups of experimental animals compared with th e control tibiae. The overall lowest porosity levels were measured in the l imited reamed group, with similar porosity levels measured in the unreamed and standard reamed groups. Porosity was lower in the limited reamed group in the entire cortex of the segmental and distal cross sections, as well as the endosteal, anterior, and posterior cortices along the length of the ti bia. Overall, there was no difference in the amount of new bone formation o r the mineral apposition rate between the three groups of animals at eleven weeks after surgery. Discussion: The results of this study suggest that limited intramedullary r eaming is a biologically sound alternative for the treatment of tibial diap hyseal fractures in which the circulation is already compromised.