Extreme temperatures

When thinking about cutting tools for surgery, the first picture to appear in most people’s minds is a knife with a small, sharp blade; a scalpel. Scalpels and other mechanical tools (for example, scissors) to cut and/or remove tissue are certainly the most widely used tools in the trade. However, they are not the only option to cut and/or remove tissue.

Various alternative methods to cut and/or remove tissue can be summarised under a unifying view of exploiting extreme temperatures for such purposes. These alternative methods rely on the effects of very high and very low temperatures on living tissues.

Very high temperatures for a surgical cutting device can be produced by different physical effects. The most common techniques are provided by the properties of (several different types of) lasers, or by high-frequency electrical current (surgical diathermy). There are subtle differences between these high (diathermy) to very high (laser tools) temperature devices and their strengths and disadvantages, and as compared with cutting with a scalpel. High temperature cutting devices may have strategic advantages where it is important to reduce or stop bleeding. They may also increase the risk of wound necrosis.

Very low temperatures exploit the unique properties of this ubiquitous and unique liquid, water. Suitable freezing techniques of tissues (known as cryotherapy), usually employing liquid nitrogen (liquid N2 temperature is -196°C) as the refrigerant, freeze water molecules in tissue cells. Water has a physical anomaly in that it expands when turning into ice. Therefore, this freezing process is harmful to cells which subsequently die because of damage by ice crystals, and then get removed by the body’s healing processes. Thus, application of very low temperatures indirectly leads to tissue removal. Although tissue can be removed by extreme cold it cannot be cut in the same way as a scalpel, diathermy or laser beam cut tissue.

Next we examine the working of the various high and low temperature devices and how they interact with biological tissues, before we consider the conditions where and how these techniques are best used in clinical practice in maxillofacial surgery.

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