Abstract
Introduction & aims
Osteonecrosis may be triggered by bone temperature above 45°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, Mich) has been recently developed but the saw blade design may influence the amount of heat generated. We have therefore sought to compare the bone temperature during a standardised cutting task with two different saw blade designs.
Method
Three pairs of human cadaveric femora were obtained. Each femur was clamped and a distal femoral cutting jig was applied. An initial cut was performed to visualise 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 infra-red camera. This was repeated, moving the block 2 mm proximal with each cut, alternating between a standard oscillating saw blade and the “Precision” saw blade. The density of the cut bone was then established from a CT scan of each specimen performed prior to the experiment.
Results
The 2 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) but the blades differed with respect to the proportion of pixels heated above the 45 deg osteonecrotic threshold, with a significant difference in the integrated curve between blades (p = 0.046) in favour of the standard saw blade.
Conclusions
The “Precision” blade may have advantages over standard oscillating blade but reduced heat generation was not found in our study. On the contrary, the “precision” blade potentially reaches the bony osteonecrosis threshold more often, questioning its use for osteotomy or uncemented knee arthroplasty. Further work should examine modifications to the blade design to better optimise the requirements of speed, accuracy and heat generation.
