حمید کیوانی

Thermal injury to the bone during drilling action is one of the primary concerns in orthopedic surgery. The temperature and length of time during which bone tissue is exposed to it, causes thermal injury. In this study, the effect of drill head friction on thermal necrosis in goat tibia was investigated histopathologically.    

Five healthy male Iranian goats were selected and 8 holes were made on the body of the tibia using a sharp spiral and split point drill and a medial approach in both hind limbs at 50, 100, 200, 250, 300, 350 and 1000 rpm. To study the effect of cooling agent on reducing the incidence of thermal necrosis in the left hind limb, sterile normal saline was used, but normal saline was not used in the right hind limb. Then, on each of the 3rd, 5th, 7th, 9th and 11th days after the operation, one of the animals was humanely slaughtered and the tibia of both limbs was sent to the laboratory for histopathological study.

Pathological results indicated that thermal necrosis was observed in 36 of 40 holes made in the right hind limb, with approximately 90% of the holes made in the left hind limb, while thermal necrosis was observed in 55% of the 40 holes made in the left hind limb. Thermal necrosis was also observed in 60% of the holes made at 250, 300, 350, and 1000 rpm in both limbs.

The results of this study indicate that speeds above 250 rpm/min contributes significantly to thermal necrosis because reducing the time by increasing the force applied to the head will reduce the likelihood of thermal necrosis. Also, using a cooling solution during drilling is one of the effective ways to reduce the incidence of thermal necrosis.