Thermal Effects of Burr and Saw Cutting Tools in Total Knee Arthroplasty

Aseptic loosening after total knee arthroplasty (TKA) can follow thermal bone injury produced by power tools. This study compared the intraoperative bone temperatures generated by rotary burrs used in robotic-assisted TKA (rTKA) with those from oscillating saws used in conventional TKA (cTKA).

A single-centre observational trial employed infrared thermography (30 Hz, ±0.05°C) to record surface temperatures during the distal femoral cut in 14 primary TKAs (rTKA = 6, cTKA = 8). Burr cuts used a 6-mm spherical burr at 80,000 rpm; saw cuts used Stryker sagittal blades. Peak and mean temperatures and the time spent above 47°C, 56°C and 70°C were extracted from the recordings and compared with Mann-Whitney tests.

All procedures exceeded the osteonecrosis threshold (47°C); maximal temperatures surpassed 90°C in every burr case and in 5/8 saw cases. Median cutting time was 241 s with the burr versus 26 s with the saw (p = 0.002). The bone remained above 47°C for a median 107 s (IQR 138) with the burr, nearly four-fold longer than with the saw (8 s; IQR 10; p < 0.001). Similar differences were observed above 56°C (65 s vs. 3 s) and 70°C (15 s vs. 0.5 s). Mean temperatures (∼51°C) did not differ significantly between devices.

Rotary burrs and oscillating saws both generate potentially harmful heat during TKA, but burrs markedly prolong exposure to cytotoxic temperatures and lengthen operative time. These findings suggest a higher theoretical risk of thermally mediated bone injury and subsequent implant loosening when burrs are used without active cooling. Larger controlled studies should assess mitigation strategies such as irrigation, cooled instrumentation or modified cutting protocols.