A Comparison of the Temperature Rise Generated in Bone by the Use of a Standard Oscillating Saw Blade and the “Precision” Saw Blade

Abstract

Introduction. Osteonecrosis may be triggered by bone temperatures above 47 °C during routine orthopaedic bone cuts using power-driven saws with potentially negative impacts on bone healing. A new oscillating-tip saw blade design (Precision®; Stryker, Kalamazoo, USA) has been recently developed with a saw blade design that may influence the amount of heat generated. We have, therefore, sought to compare the bone temperature achieved using this new blade design with a standard oscillating saw during a standardized cutting task. Method. Six human cadaveric femora were obtained. Each femur was clamped and a distal femoral cutting jig was applied. An initial cut was performed to visualize the distal metaphyseal bone. The cutting block was then moved 2 mm proximal and a further cut performed, measuring the temperature of the bone with an infrared camera. This was repeated, moving the block 2 mm proximal with each cut, alternating between a standard oscillating saw blade (12 cuts) and the Precision® saw blade (12 cuts). The bone density at the level of each slice was established from a CT scan of each specimen which had been performed prior to the experiment. Results. The two blades did not differ with respect to the integrated mean temperature calculated for each cut (p = 0.89). The average peak temperatures were not significantly different between blades (p = 0.14). There was no significant difference between blades for peak heating rate (p = 0.7), although the area of bone heated above the 47 deg osteonecrotic threshold was significantly (p = 0.04) less for the standard saw blade. Conclusions. The Precision® blade may have advantages over standard oscillating blade, but reduced heat generation was not observed in this study. Indeed, the Precision® blade generated heat that exceeded the bony osteonecrosis threshold in a greater proportion of bone than the standard blade, questioning its use for osteotomy or uncemented knee arthroplasty. Further work should examine modifications to the blade design to better optimize the requirements of speed, accuracy and heat generation.