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Tissue-hardening effect and health-hazard issue of formaldehyde (FA) have long been a great disadvantage of this conventional fixative in anatomical research. We recently developed a FA-free embalming method for cadavers which utilizes N-vinyl-2-pyrrolidone (NVP) and enables assessment of motion kinetics by maintaining the softness of embalmed tissue. By assessing the feasibility of NVP-embalmed tissue to mimic vocalization, this study aimed to prove the potential of embalmed cadavers, which have previously been used only for the understanding of anatomical morphology, for the assessment of precise motion physiology in the human body. Ten cadavers embalmed in NVP (n = 6) and FA (n = 4) were incorporated in this study. Excised larynges underwent experimental phonation to mimic vocalization with fast and pliable vibration of vocal folds. High-speed digital imaging was utilized for the assessment of vocal fold vibration. Furthermore, acoustic analysis of the voiced sound, and reproducibility examination were also performed. Regular vocal fold vibrations successfully produced voiced sounds during experimental phonation using NVP-embalmed larynges. The vibratory frequency, vibration amplitude, and stretch rate of the vocal folds were comparable to those of living humans. Six months after the first experiment, the vocal parameters were reproduced, to suggest the long-term preservation potential of our NVP-embalming technique. On the other hand, neither voiced sound nor vocal fold vibration were observed in FA-embalmed larynges. This novel embalming technique could pioneer the next era to utilize embalmed cadavers for the examination of motion physiology in the human body.

The traditional apprenticeship approach to surgical skill education for young surgeons has drastically changed to more systematic surgical training using cadavers. Cadavers fixed with formalin are not suitable for surgical training because of their associated health hazards and overhardening. Recently, we established a formalin-free soft preservation method for human cadavers using N-vinyl-2-pyrrolidone. Since 2012, 61 cadavers have been embalmed with pyrrolidone in our institution. Tissues of pyrrolidone-embalmed cadavers are soft and pliable, and their bodies can be preserved for as long as 37 months without any signs of corruption. In this review, we introduce our recent attempts to apply pyrrolidone-embalmed cadavers in surgical and medical procedure training, including endotracheal intubation, motion physiology of the vocal folds, laparoscopic surgery, endoscopic skull base surgery, and development of novel medical devices. Future research perspectives on pyrrolidone embalming are discussed.

The demand for cadavers for clinical skills training is increasing. However, conventional formalin-fixed bodies are often unsuitable for surgical training because the tissues become too hard. We recently developed a new formalin-free embalming method with N-vinyl-2-pyrrolidone (pyrrolidone) that has excellent fixative, disinfectant, and preservative properties, while still keeping tissues soft and pliable. In the study reported here we investigated the feasibility of laparoscopic manipulation using pyrrolidone-fixed cadavers. Donated cadavers were embalmed either with pyrrolidone (n = 7) or with formalin-containing fixative (n = 3). A laparoscopic 12-mm trocar was inserted into the umbilical region, and CO2 gas was insufflated. Intra-abdominal structures were observed with an endoscopic camera. In the pyrrolidone-embalmed cadavers, the abdomen remained soft and depressed. In addition, CO2 injection resulted in a marked expansion of the abdominal cavity, and it was possible to move the laparoscope freely in all directions. Clear endoscopic images of the abdominal viscera were obtained. The gallbladder and rectum were identified by grasping the surrounding organs with forceps. By contrast, in the formalin-fixed bodies, the abdominal wall was rigid, and it was difficult to move the laparoscope in the peritoneal space and observe structures in detail. The amount of CO2 and changes in abdominal diameter and circumference in response to CO2 injection were significantly larger in the pyrrolidone group. In conclusion, we successfully created a sufficient pneumoperitoneum state and obtained clear endoscopic images in the pyrrolidone-embalmed cadavers. Handling and dissection of the intra-abdominal structures with forceps closely replicated real-life surgery. These findings suggest the feasibility of laparoscopic training on cadavers embalmed with this pyrrolidone fixative.