Thiel Cadaveric Nerve Tissue: A Model for Microsurgical Simulation

Abstract

Peripheral nerve research as well as nerve repair simulation has relied heavily on the rat animal model, more specifically on the rat sciatic nerve.1 As the use of animals in experiments and training has received much criticism from animal rights activists and society at large, the field of surgical simulation is currently emerging. In microsurgery, high-fidelity Silastic models, animal parts such as chicken thighs or wings, and cadaveric specimens have been used. Based on the available experience with Thiel embalmed cadaveric tissue in simulation,2–4 we experimented with Thiel embalmed peripheral nerves for the purpose of microsurgical skill training. We used median, ulnar, and tibial nerves from cadavers that had been used for anatomic and surgical training and had not touched the peripheral nerve tissue. The donors had previously consented to tissue utilization in postmortem research. The tissues originated from cadavers prepared with the embalming method described by Thiel.5 This technique preserves texture, volume, color, and shape of the body as perfect as possible, with the advantage of avoiding decay observed with fresh cadaveric specimens. There is no shrinking or soaking of the soft tissues. Thirteen nerve sections measuring 5 cm eachwere prepared on a foam board. Needles (25 G) are used to fix the nerves to the foam board. A blue background was used for the exercise, as it improves contrast. An operating microscope (Opmi Pico, Carl Zeiss, Oberkochen, German) at 10 magnification was used for all microneurorrhaphies. Under magnification, the nerves were crushed in the midsection to simulate an injured nerve. The participants transected the nerve using a 15-blade scalpel, and trimmed the damagednerve tissue. The two endswere inspected for the fascicular architecture and oriented appropriately for the repair. The epineurium was then gently reflected back and the proud fascicles trimmed. Nylon 8–0 sutures were used to perform a simple epineural repair, starting with the 0and 180-degree orientation sutures and then filling in the required sutures to obtain a well-oriented microneurorrhaphy. Under magnification of the operative microscope, we found the Thiel nerve tissue to show a slight gray-brown discoloration with an epineural layer that was hydrophilic, giving the impression of edematous tissue (►Fig. 1). This thicker-than-normal epineural layer, however, offers adequate support for manipulation. Unfortunately, the cadaveric nature of themodel precludes the use of the vasa nervorum,which are not visible, for adequate orientation of the nerve. Upon transection of the nerve, it can be observed that the fascicles arewell preserved and bound byfirm endoneurium and perineurium which have not undergone the same edema as the epineurium (►Fig. 1). Despite therebeing no immediate herniation of nerve fascicles upon transection, the fascicles have a tendency to bemorehygroscopic, and by the end of the neurorrhaphy, one can observe some protrusion of fascicles in between suture. The fascicular pattern is easily identifiable and permits good alignment of the nerve before suturing. Thirteen volunteer plastic surgery, otolaryngology, and orthopedics residents utilized themodel once each, andfilled out a postsimulation survey. The results were graded on a five-point Likert scale (strongly agree, disagree, neither agree nor disagree, agree, strongly agree). A question regarding the frequency participants would use the laboratory with answers graded in five categories was also asked. The contents of the postsimulation survey are presented in ►Table 1. Descriptive statistics are presented for the results of the survey questions. All participants (100.0%) agreed that they would use themodule at least twice a year,with 53.9% (seven residents) stating theywoulduse itmore than once amonth, 38.5% (five residents) once amonth, and7.7% (one resident) twice a year. The rapid development of microsurgery over the last three decades has been echoed by the development of several simulation models for the teaching and honing of microsurgical skills. Free flaps are routine procedures in most plastic surgery centers, and residents have ample opportunity to participate and perform in these procedures. As a