Investigation of thermally induced damage to surrounding nerve tissue when using curettage and cementation of long bone tumours, modelled in cadaveric porcine femurs

Abstract

Introduction: Curettage with cement augmentation is a technique used in the treatment of bone tumours. Thermal energy released during the cement polymerisation process can damage surrounding tissues. This study aims to record temperature changes at various sites on and around bone during the cementing process. We hypothesised that adjacent structures, such as the radial nerve, may be threatened by this process in the clinical setting.

Materials and methods: Using 18 porcine femurs as a model of the human humerus, we used thermocouples and a thermal imaging camera to measure changes in temperature during the cementing process. Fractures were created in nine samples to establish whether a discontinuity of the cortex had an effect on thermal conduction.

Results: Significantly higher temperatures were recorded in samples with a fracture compared to those without a fracture. The site overlying the centre of the cement bolus (hypothetical site of the radial nerve) demonstrated higher temperatures than all other sites on the same cortex. When considering the radial nerve site, over half the samples demonstrated temperatures exceeding 47 °C for over a minute. When a threshold of 50 °C for more than 30 s was considered, three samples without a fracture exceeded this value compared to two with a fracture.

Conclusion: The temperatures recorded were sufficient to cause damage to neural tissue. Limiting thermal exposure to soft tissues is recommended. Increased attention is required when using larger cement boluses, or where bone quality is poor or a fracture, iatrogenic or preexisting, is present.

Keywords: Cement; Curettage; Long bone tumours; Radial nerve damage; Thermal energy.

Fig. 1

Porcine femur showing 12-mm/12-mm window

Fig. 2

Porcine femur demonstrating ‘fracture line’ extending to anterior cortex

Fig. 3

Demonstrates experimental set-up, with and without fracture

Fig. 4

Showing thermocouple set-up at proposed site of radial nerve

Fig. 5

Porcine femur showing cavity filled with cement

Fig. 6

Graph showing thermal imaging camera data against time with 95% confidence intervals plotted. Programme used: statsmodels.org and matplotlib version 3.0.2

Fig. 7

Graph showing thermal imaging camera data against time with one standard deviation plotted. Programme used: pandas.pydata and matplotlib version 3.0.2