I read with interest the article by Gruber et al that is designed to address concerns about the zone of thermal injury associated with various energy sources used to transect the vagina at the time of total hysterectomy. On one hand, the authors have demonstrated that in their hands, with instruments and electrosurgical unit (ESU) settings presumably similar to what they use in humans, there is a progression of injury that is least with an ultrasonic scalpel and greatest with the bipolar instruments, with a monopolar instrument falling between the 2.

The demonstration of these differences is useful and may well indicate a clinically significant component of the pathogenesis of apparent increased risk of posthysterectomy vault dehiscence that has been reported in conjunction with both laparoscopic and robotic hysterectomy. However, there are a number of issues related to the description of the design of this study that suggest that the authors are not familiar with basic concepts of radiofrequency electrical energy that may have an impact on the results.

There are a number of terms that are misused. For example, the authors frequently misuse the term cautery. Cautery is the passive transfer of heat from a heated object to a tissue surface; the instruments that they use in this study are not based on cautery; they are based on radiofrequency electricity that heats the tissue largely secondary to electromagnetic oscillation of intracellular ions and perhaps enhanced by the process of resistive heating.

There is another pair of incorrect terms, monopolar energy and bipolar energy. In fact, the type of energy used in both types of instruments is identical: radiofrequency electromagnetic energy is delivered to tissue either with a bipolar instrument (in which both poles are on the same device) or a monopolar instrument (in this case the scissors) in which only 1 electrode is on the instrument, whereas the other, the dispersive electrode, is located remotely. The specifications of radiofrequency ESUs are important when trying to interpret tissue effects because specifics of the waveforms such as peak-to-peak voltage vary among different machines. In this study, we do not know what type of ESU was used for the monopolar system, and we also do not know which Olympus-Gyrus generator (Olympus-Gyrus, Southborough, MA) was used for the bipolar system. As a result, it is difficult to know what the “blended” waveform actually was, although in any generator blend is a modulated low-voltage output, not a combination of waveforms as is suggested by the authors.

Another issue relates to the comingling of 2 very different bipolar instruments as study bipolar devices. One of these devices is designed to cut and provide lateral coagulation simultaneously (J hook), whereas the other is a grasping forceps with no cutting mechanism. The authors did not describe how cutting was achieved with this device. Furthermore, although they did demonstrate substantial differences between the forceps and the J hook in Figure 7, they did not point out that the confounding of the results related to the heterogeneity of the methods makes interpretation of the bipolar data difficult.

There are a number of inherent biases in this study not identified by the authors. The ultrasonic system was set to the power associated with the lowest amount of lateral thermal injury. However, the same was not the case for the monopolar instrumentation. For example, it is quite possible that the authors could have generated a high current (or power) density, sufficient to transect the vagina, but with much lower power if they used a monopolar needle or blade. Such an approach could have been associated with an even smaller zone of collateral thermal injury adjacent to the incision. The design of the generator can also have an impact because impedance monitoring allows for variable and often reduced power to the electrode if the system has that capability.

Although perhaps seeming pedantic, these issues belie a relative lack of understanding that can undermine the design and interpretation of these types of studies. It is time that the editors of our journals take note of these issues and devise standards for study design and reporting that allow for a better understanding and interpretation of the results of the investigation of energy based surgical systems.