[The factors affecting thermal necrosis secondary to the application of the Ilizarov transosseous wire]

We investigated thermal changes associated with the application of the Ilizarov transosseous wires, the extent of necrosis, and the factors affecting necrosis.

We used a pair of tibiae from a 1-year-old cow. After removal of metaphyseal areas, each of four equal diaphyseal zones marked on both tibiae was drilled at 600, 900, 1,200 and 1,800 rpm, each time with a new wire. Heat changes were recorded with heat electrodes during the application and the speed of the wire was calculated. For histopathological examination, specimens were obtained at the access and exit sites to assess the extent of necrosis. Thermal changes between the zones and immediate and remote cortices were compared. The most significant factor affecting the heat changes was analyzed by linear regression.

Heat changes varied between 48.4 degrees C (at 1,200 rpm) and 151.9 degrees C (at 600 rpm). The thickness of the immediate cortex, the time and speed for the wire to pass the cortex were found as significant parameters in heat changes (p=0.003, p=0.01, and p=0.01, respectively). A negative correlation was found between the speed of the wire and the thickness of the necrotic area (r=-0.901, p=0.001). Regression analysis showed that the time for the wire to pass through the cortex was the most significant factor in inducing heat changes in both cortices (p=0.001, p=0.003, respectively). Histopathologically, the extent of necrosis and bone erosion was associated with lower drill speeds. Necrosis was significantly notable in the immediate cortex than that of the remote one (p=0.006).

Transosseous wires should be passed at high drill speeds and with earliest time elapses to reduce thermal necrosis.