Heat Production and Thermal Necrosis by Cortical Drilling / 대한정형외과연구학회지

ABSTRACT

PURPOSE: The present study was performed to determine the optimum conditions(RPM, load, sharpness of drill) for drilling human cortical bone with standard drill, and to evaluate the histological changes occuring in bone after drilling. MATERIALS AND METHODS: in experiment I, we measured temperature elevations and the durations of temperature elevation in cadaveric femoral cortices at specific distances from the drill hole wall while drilling. The effects of drilling force, speed and new versus worn drill on the termperature were determined. In experiment II, we also measured temperature elevations in the same manner in porcine femoral cortices and evaluated the histological changes occuring in bone after drilling. RESULTS: In experiment I, the most significant temperature elevation(68.4degrees C ) was found when worn drill was used. The lower drilling force and faster speed resulted in 55.1degrees C and 45.8degrees C temperature elevation, respectively. However, drill diameter was not a significant factor for temperature elevation. In experiment II, greater heat production was measured with worn drill, at lower drilling forces, at faster drill speed. The acute histologic reactions in bone were hyperemia, degeneration of osteocytes, change in bone stainability, tears, and fragmentation of the bone edges around the drill holes. The observed histological changes were proportional to the amount of trauma produced, that is, the greater the degree of thermal irritation, the greater the degree of histologic activity. CONCLUSION: In cortical drilling, greater heat production was measured with worn drill, at lower drilling forces, at faster drill speed and the greater the degree of thermal irritation, the greater the degree of histologic activity. A further study of the reaction of bone to drilling at longer intervals of time at different conditions may possibly show whether aseptic thermal necrosis could be prevented.