With developments in the field of less-invasive procedures such as endoscopy, laparoscopy and robotic surgery, the importance of achieving basic surgical skills remains one of the most important goals during surgical residency. Qualified residency education is even more important as fewer opportunities are given due to the abovementioned surgical development and duty-hour regulations [12]. Work-hour limitations, financial constraints, and ethical concerns have forced educators to explore new options for increasing the efficiency of training and teaching outside of the operating room [3].

Open suturing in accurate anatomic tissue layers and knot-tying with adequate tension are fundamental skills to minimize surgical complications and scarring [4]. Various education curricula and assessment tools have been developed and validated utilizing artificial suture pads and animal (mainly porcine) integument models [5678]. Nevertheless, these materials are often too tough or too weak to mimic soft but elastic human skin, and they differ in terms of composition of anatomic tissue layers, including epidermis, dermis, subcutaneous fat, and superficial fascia.

Abdominoplasty is a body-contouring surgery in which substantial amounts of normal abdominal skin and subcutaneous fat are excised and discarded from the lower abdomen [9]. Autologous breast reconstruction using abdominal tissue transfers almost identical to tissue of abdominoplasty, in order to reconstruct the breast after mastectomy, involves about one-third of the (most distal) tissue that cannot be used as part of the flap because of inherent perfusion problems [10]. These tissues are usually incinerated because they are not clinically or experimentally significant (Fig. 1).

We have been utilizing this tissue to teach medical student suturing and injection techniques immediately after surgery after gaining consent from the patients to use their tissue for comprehensive research and medical educational purposes. However, this curriculum should be continued year round for only a small number at one time. Work-hour regulations forces hospital staff to seek out efficient and effective training/education curricula for residents from all surgery departments [123]. We recently held four sessions of a surgical skills workshop for a total of 53 residents from various surgery departments (13 to 14 in one session), and suturing was taught using frozen-thawed abdominal tissue. We present our experience with a focus on tissue handling and ethical issues.

The workshop included open suturing, airway management, central line insertion, and intraosseous injection, chest tube placement, and acute management of spinal cord injury and pelvic bone fractures. Two instructors participated in each 50-minute hands-on session teaching 3 to 5 residents. Suturing was taught by 2 board-certified plastic surgeons.

Abdominal tissue was obtained from patients who underwent autologous breast reconstruction and all gave consent to use their tissue for comprehensive research and medical educational purposes. Our Institutional Review Board granted exempt status for this protocol given that we obtained proper consent forms and removed all personal identification information (approval number: 2017-1249). After the surgery, abdominal tissue remnants were anonymized: all personal identifiers were removed because reidentification would not be necessary in any situation. Randomly-labeled tissues were rapidly frozen and maintained at minus 30℃ for a few months, then slowly thawed on the night prior to use. The required number of tissues were stored at 4℃ for about 12 hours, then maintained at room temperature for the final 4–5 hours. Thawed tissue returned to the status of fresh skin and subcutaneous fat including Scarpa's fascia. Tissue was then tacked on a plywood board and used for hands-on suture education and training, focusing on placing sutures at accurate anatomic layers and knot-tying with adequate tension (Fig. 2). Tissue samples were then transferred to pathology waste storage immediately after the workshop program and were disposed of by incineration along with other surgery/pathology specimens in accordance with our institution's regulations.

Tissue samples were stored frozen for 0.5 to 6 months prior to being thawed. A typical tissue specimen was a triangle-shaped full-thickness section of abdominal skin and subcutaneous fat with an average size of 10 cm × 10 cm with varying thicknesses. Tissue samples regained normal texture and consistency after thawing. Microscopic evaluation confirmed almost normal histologic structure of the specimens (Fig. 3).

The teaching program covered tension-releasing deep tissue sutures in the superficial (Scarpa's) fascia, buried dermal suture, and accurate skin closure. A total of 53 first- and second-grade residents from general, plastic, orthopedic, cardiothoracic, dental surgery, and emergency medicine departments participated in the workshop, and 45 residents finished the questionnaire after the session; the results are summarized in Table 1. Average satisfaction scores regarding the tissue used in the education were more than 9.5 out of 10 (10: completely agree/satisfied, 0: completely disagree/dissatisfied).

Table 2 summarizes total and specific item costs for the workshop program. Briefly, all 4 workshop sessions covering 53 residents cost 2,857,780 Korean Won (KRW), including 1,500,000 KRW for the instructor fees (52.5%).

Duty-hour regulations for residents inevitably causes less time to be spent in the operating room for lower-grade residents [12]. In the United States, where the history of duty limitation is longer than that of the Republic of Korea, such concerns generated a comprehensive strategy to maximize the operating experience for junior residents [3]. Nevertheless, technical developments such as laparoscopy and robotic procedures, along with recently-developed convenient devices such as absorbable staples and skin adhesives, also led to decreased opportunities for junior residents to participate in surgical procedures. Therefore, there is an increased need for efficient and effective surgical skills education.

With respect to suture technique education, placement of the suture at the accurate anatomic layer with proper tension is as important as proficiently handling surgical instruments, because secure knots with proper tension in the correct layer has a major impact on blood supply and the healing process of nearby tissue [68]. Various artificial suture pads or porcine skin are used for suturing education; however, these materials have different anatomic composition and cannot mimic human skin's soft elasticity [57]. A visual feedback system was developed to overcome the lack of accurate haptic feedback [8]. Nevertheless, elaboration regarding developing and verifying models for suture education remains relatively sparse compared to other aspects of surgical skills education [1112].

Breast reconstruction is constantly increasing since its coverage by national health insurance in Korea, and the number of hospitals where autologous (especially abdominal tissue based) breast reconstruction is also increasing. The merits of using real frozen-thawed human full-thickness skin-subcutaneous tissue for suture education wound be substantial. This kind of tissue preservation for later use has already been widely-described and clinically-utilized in various medical fields [13]. The purpose of this article was to introduce a possible alternative in surgical skills education, for a large number simultaneously, presumably after finishing basic technique education and practice using existing models. Curriculum development and objective validation of its educational benefit is beyond the scope of this study. We could not find any previous study describing this type of frozen-thawed normal tissue utilization from live humans for purely educational purpose. Nevertheless, we believe the value of proper education and training for medical students as well as for surgical residents would be as important as any study in terms of continuity and development of medicine.

In conclusion, frozen-thawed abdominal tissue remnants could be used for suture education for several residents at the same time. This could be more efficient than direct hands-on training in the operating room and would provide excellent anatomic structure and consistency at minimal cost. While this tissue can only be obtained in large centers performing abdominoplasty and/or autologous breast reconstruction, and sufficient ethical discussion should precede collection, we propose that cryopreserved human tissue remnants might be utilized in medical education and training upon complete anonymization and strict regulation.