Heat caused by drilling cortical bone. Temperature measured in vivo in patients and animals

In vivo temperature measurements were performed at drilling in the femoral cortex of the rabbit, dog and man. In the clinical study the bone temperature was measured at fixation of a Richards plate to stabilize a pertrochanteric fracture. With a drill speed of around 20 000 rpm and saline cooling, temperatures of 40 degrees C in rabbits, 56 degrees C in dogs and 89 degrees C in patients were recorded at a distance of 0.5 mm from the periphery of the drill hole. The difference in temperature between the animal and clinical studies was mainly attributed to the difference in cortical thickness between the species. When drilling straight through the canine femur from the lateral to the medial side, a 9 degrees C higher temperature was measured in the remote, medial cortex compared to that recorded in the lateral cortex. This difference arose because it is difficult for the cooling agent to reach the medial cortex. The results of the present study indicate that temperatures measured in animal experiments are not applicable to the clinical situation where very high temperatures may arise on drilling in cortical bone, even if saline cooling is used.