Development of the McMaster Embalming Scale (MES) to assess embalming solutions for surgical skills training

Human cadavers used for surgical training are embalmed using various methods to facilitate tissue storage and longevity while preserving the natural characteristics required to achieve high fidelity functional task alignment. However, there are no standardized means to evaluate the suitability of embalming solutions for this purpose. The McMaster Embalming Scale (MES) was developed to assess the extent to which embalming solutions allow tissues to achieve physical and functional correspondence to clinical contexts. The MES follows a five-point Likert scale format and evaluates the effect of embalming solutions on tissue utility in seven domains. This study aims to determine the reliability and validity of the MES by presenting it to users after performing surgical skills on tissues embalmed using various solutions. A pilot study of the MES was conducted using porcine material. Surgical residents of all levels and faculty were recruited via the Surgical Foundations program at McMaster University. Porcine tissue was unembalmed (fresh- frozen) or embalmed using one of seven solutions identified in the literature. Participants were blinded to the embalming method as they completed four surgical skills on the tissue. After each performance, participants evaluated their experience using the MES. Internal consistency was evaluated using Cronbach's alpha. Domain to total correlations and a g-study were also conducted. Formalin-fixed tissue achieved the lowest average scores, while fresh frozen tissue achieved the highest. Tissues preserved using Surgical Reality Fluid (Trinity Fluids, LLC, Harsens Island, MI) achieved the highest scores among embalmed tissues. The Cronbach's alpha scores varied between 0.85 and 0.92, indicating a random sample of new raters would offer similar ratings using the MES. All domains except odor were positively correlated. The g-study indicated that the MES is able to differentiate between embalming solutions, but an individual rater's preference for certain tissue qualities also contributes to the variance in scores captured. This study evaluated the psychometric characteristics of the MES. Future steps to this investigation include validating the MES on human cadavers.