ORTHOPEDIC DRILLING & THERMAL INJURY ANALYSIS

Abstract

In orthopedic surgery, fixation pins are used to provide stability of bone segments to ensure proper healing. The drilling process to implant these pins can generate a considerable amount of heat. Raising the temperature of bone tissue above 47°C for a prolonged amount of time can cause cell death in a process called thermal osteonecrosis. Should bone tissue surrounding implants like fixation pins die and begin to break-down, the stability of said implants becomes at risk for failure. The failure of a surgical implant can be costly, resulting in additional surgery for repairs and prolonged recovery time. Reducing the amount of heat generated during drilling can greatly lessen the potential for thermal injury. This study aims to evaluate the effect of varying drilling parameters on heat generation, namely examining if internal temperatures be reduced by varying the rotational velocity and feed rate in orthopedic drilling, and thus reduce the probability of thermal osteonecrosis. Experiments were performed comparing combinations of feed rates and spindle speeds for the drilling process parameters, specifically feed rates of 1.5, 3.0, 5.0, 9.0, and 12.0 mm⁄s and spindle speeds of 1000, 2000, and 3000 rpm. The tests used traditional smooth-shaft fixation pins, with trocar tips, that were drilled into 20 PCF synthetic bone. A Flir T440 infrared camera was used to record thermal video of the drilling process. Data acquired from the infrared camera shows that lower spindle speeds resulted in lower maximum temperatures while varying feed rates had only a moderate effect. With these results orthopedic drilling can be optimized for reduced heat generation and the prevention of thermal osteonecrosis.