Flap raising on pulsatile perfused cadaveric tissue: a novel method for surgical teaching and exercise

Simulation of Reconstructive Microsurgery in Soft Embalmed Cadavers: A Teaching Module for Plastic Surgery Residents

Background  Cadaveric dissection courses—comprising flap harvesting techniques, vessel dissections, flap transfers to the defect, and microvascular anastomosis—would help residents gain confidence and master these difficult major reconstructive microsurgery procedures. Formalin embalmed bodies lack natural softness and many other features of a live body. Many soft embalming techniques have evolved to mimic live tissue and Theil technique is the most popular one among them. We explored alternate soft embalming options and started using Genelyn.

Materials and Methods  Over a span of 2 years (2019–2021), we have conducted three flap dissection workshops using soft-embalmed cadavers. Six soft-embalmed and two formalin-embalmed cadavers were used. Total number of participants was 80.

Results  Feedback of experience from the third course participants in the form of grades (1–5) for different criteria was obtained and evaluated. Confidence in the dissection of the various flaps and microsurgery is noticeable in all the participants.

Conclusion  Based on our experience, we propose that flap dissection and microsurgery training on soft-embalmed cadavers be included as a teaching module in the plastic surgery postgraduate curriculum.

Development of a novel educational tool to assess skills in laparoscopic liver surgery using the Delphi methodology: the laparoscopic liver skills scale (LLSS)

BACKGROUND

No specific performance assessment scales have been reported in laparoscopic liver resection. This study aimed at developing an objective scale specific for the assessment of technical skills for wedge resection in anterior segments (WRAS) and left lateral sectionectomy (LLS).

METHODS

A laparoscopic liver skills scale (LLSS) was developed using a hierarchical task analysis. A Delphi method obtained consensus among five international experts on relevant steps that should be included into the LLSS for assessment of operative performances. The consensus was predefined using Cronbach's alpha > 0.80.

RESULTS

A semi-structured review extracted 15 essential subtasks for full laparoscopic WRAS and LLS for evaluation in the Delphi survey. Two rounds of the survey were conducted. Three over 15 subtasks did not reach the predefined level of consensus. Based on the expert's comments, 13 subtasks were reformulated, 4 subtasks were added, and a revised skills scale was developed. After the 2nd round survey (Cronbach's alpha 0.84), 19 subtasks were adopted. The LLSS was composed of three main parts: patient positioning and intraoperative preparation (task 1 to 8), the core part of the WRAS and LLS procedure (tasks 9 to 14), and completion of procedure (task 15 to 19).

CONCLUSIONS

The LLSS was developed for measuring the skill set for the education of safe and secure laparoscopic WRAS and LLS procedures in a dedicated training program. After validation, this scale could be also used as an assessment tool in the operating room and extrapolated as an operative roadmap to other complex procedures.

The Thiel cadaveric model for pelvic floor surgery: Best rated in transferable simulation-based training for postgraduate studies

OBJECTIVE

To determine whether the Thiel cadaveric model is better and more realistic than other surgical simulation techniques for learning pelvic floor and perineal surgical procedures according to the opinions of urogynecologists and surgeons participating in international postgraduate pelvic floor surgery courses using cadavers embalmed by the Thiel method.

STUDY DESIGN

An observational prospective study was performed in urogynecologists and surgeons attending international postgraduate pelvic floor and perineal surgery courses using cadavers embalmed by the Thiel method. A survey was completed by the participants after finishing the course. Based on the answers collected, we analyzed the differences, including in the satisfaction degree and teaching level for each surgical procedure, between different surgical simulation models that the participants had already used and the Thiel simulation method employed.

RESULTS

The students recognized that Thiel cadavers present more similarities to patients than other simulation methods. The Thiel cadaveric method was considered by most responders to be the best for the simulation of surgical procedures on the pelvic floor and perineum. Most of the surgeons surveyed recommended conducting these courses with Thiel cadavers for different colleagues in other specialties as a reliable simulation method for training for difficult surgical procedures.

CONCLUSIONS

Participants in the course on pelvic floor surgery in Thiel cadavers recognized that this is the most realistic model for surgical simulation and the best way to gain confidence, self-determination and precise surgical skills for performing pelvic floor and perineal surgery.

Pathophysiology Study of Filler-Induced Blindness

Background

A number of authors have proposed retrograde arterial embolism as the responsible mechanism for filler-induced blindness. However, no previous human study has substantiated this proposed mechanism.

Objectives

The aim of this study was to investigate the pathophysiology of filler-induced blindness using a fresh cadaver perfusion technique.

Methods

A fresh cadaver head perfusion model that simulates both physiologic blood pressure and flow rate of the carotid artery, ophthalmic artery, and supratrochlear artery was used. The common carotid artery was cannulated and the internal jugular vein exposed for open venous drainage. A plasma-based perfusate was circulated through the cadaver head, which was connected to a perfusion system consisting of a roller pump, preload reservoir, and pressure monitor. The hyaluronic acid filler mixed with methylene blue was injected into the cannulated superficial branch of the supratrochlear artery. Cadaver dissection, angiographic study, and histology were used to investigate filler-induced blindness.

Results

Cannulation of the superficial branch of the supratrochlear artery was successful in all six cadavers. Emboli to the ophthalmic artery was successfully demonstrated in the three out of 6 fresh cadaver heads. The C-arm angiogram documented a cut-off sign in the ophthalmic artery due to hyaluronic acid filler emboli. An average intravascular volume of the intraorbital part of the supratrochlear artery was 50.0 µL. The average depth of location of the superficial branch of the supratrochlear artery from the epidermal surface was 1.5 mm.

Conclusions

Our cadaveric study demonstrated that retrograde hyaluronic acid filler emboli to the ophthalmic artery could be produced by the cannulation of the supratrochlear artery. The superficial location of the supratrochlear artery, the rich vasculature surrounding it, and the variability in the anatomy make this possible.

Systematic review of surgical training on reperfused human cadavers

BACKGROUND

The role of reperfused human cadavers in surgical training has not been established.

METHODS

Reports describing reperfused human cadaver models in terms of simulated surgeries, the use of tools to assess technical competency and skills transfer to patients, cadaver status and reperfusion techniques were included.

RESULTS

Thirty-five reports were included. Most participants practised vascular (n = 27), flap (n = 6) and trauma (n = 4) procedures. Training progression was evaluated objectively in only two studies. In two publications, flap techniques were practised on cadavers and repeated successfully in patients. Eighteen studies employed whole bodies. Fresh and embalmed cadavers were both used in 17 publications. Most embalmed cadavers were formalin-fixed (n = 10), resulting in stiffness. Few trainings were offered on soft Thiel-embalmed cadavers (n = 5). Only arteries were reperfused in 20 studies, while in 13 publications, the arteries and veins were filled. Arteries and/or veins were mostly pressurized (n = 21) and arterial flow was generated in 14 studies.

CONCLUSIONS

Various reperfused human cadaver models exist, enabling practise of mainly vascular procedures. Preservation method determines the level of simulation fidelity. Thorough evaluation of these models as surgical training tools and transfer effectiveness is still lacking.

An enhanced fresh cadaveric model for reconstructive microsurgery training

BACKGROUND

Performing microsurgery requires a breadth and depth of experience that has arguably been reduced as result of diminishing operating exposure. Fresh frozen cadavers provide similar tissue handling to real-time operating; however, the bloodless condition restricts the realism of the simulation. We describe a model to enhance flap surgery simulation, in conjunction with qualitative assessment.

METHODS

The fresh frozen cadaveric limbs used in this study were acquired by the University. A perfused fresh cadaveric model was created using a gelatin and dye mixture in a specific injection protocol in order to increase the visibility and realism of perforating vessels, as well as major vessels. A questionnaire was distributed amongst 50 trainees in order to assess benefit of the model. Specifically, confidence, operative skills, and transferable procedural-based learning were assessed.

RESULTS

Training with this cadaveric model resulted in a statistically significant improvement in self-reported confidence (p < 0.005) and prepared trainees for unsupervised bench work (p < 0.005). Respondents felt that the injected model allowed easier identification of vessels and ultimately increased the similarity to real-time operating. Our analysis showed it cost £10.78 and took 30 min.

CONCLUSIONS

Perfusion of cadaveric limbs is both cost- and time-effective, with significant improvement in training potential. The model is easily reproducible and could be a valuable resource in surgical training for several disciplines.Level of Evidence: Not ratable.

Cadaveric Spinal Surgery Simulation: A Comparison of Cadaver Types

Study Design Single-blinded study. Objective To assess the suitability of three types of cadaver for simulating pedicle screw insertion and establish if there is an ideal. Methods Three types of cadaver-Thiel-embalmed, Crosado-embalmed, and formaldehyde-embalmed-were draped and the spines exposed. Experienced surgeons were asked to place pedicle screws in each cadaver and give written questionnaire feedback using a modified Likert scale. Soft tissue and bony properties were assessed, along with the role of simulation in spinal surgery training. Results The Thiel cadaver rated highest for soft tissue feel and appearance with a median score of 6 for both (range 2 to 7). The Crosado cadaver rated highest for bony feel, with a median score of 6 (range 2 to 7). The formaldehyde cadaver rated lowest for all categories with median scores of 2, 2.5, and 3.5, respectively. All surgeons felt pedicle screw insertion should be learned in a simulated setting using human cadavers. Conclusion Thiel and Crosado cadavers both offered lifelike simulation of pedicle screw insertion, with each having advantages depending on whether the focus is on soft tissue approach or technical aspects of bony screw insertion. Both cadaver types offer the advantage of long life span, unlike fresh frozen tissue, which means cadavers can be used multiple times, thus reducing the costs.

Development of an Extracorporeal Perfusion Device for Small Animal Free Flaps

Background

Extracorporeal perfusion (ECP) might prolong the vital storage capabilities of composite free flaps, potentially opening a wide range of clinical applications. Aim of the study was the development a validated low-cost extracorporeal perfusion model for further research in small animal free flaps.

Methods

After establishing optimal perfusion settings, a specially designed extracorporeal perfusion system was evaluated during 8-hour perfusion of rat epigastric flaps followed by microvascular free flap transfer. Controls comprised sham-operation, ischemia and in vivo perfusion. Flaps and perfusate (diluted blood) were closely monitored by blood gas analysis, combined laser Doppler flowmetry and remission spectroscopy and Indocyanine-Green angiography. Evaluations were complemented by assessment of necrotic area and light microscopy at day 7.

Results

ECP was established and maintained for 8 hours with constant potassium and pH levels. Subsequent flap transfer was successful. Notably, the rate of necrosis of extracorporeally perfused flaps (27%) was even lower than after in vivo perfusion (49%), although not statistically significant (P = 0,083). After sham-operation, only 6% of the total flap area became necrotic, while 8-hour ischemia led to total flap loss (98%). Angiographic and histological findings confirmed these observations.

Conclusions

Vital storage capabilities of microvascular flaps can be prolonged by temporary ECP. Our study provides important insights on the pathophysiological processes during extracorporeal tissue perfusion and provides a validated small animal perfusion model for further studies.

Lifelike Vascular Reperfusion of a Thiel-Embalmed Pig Model and Evaluation as a Surgical Training Tool

BACKGROUND

Vascular reperfusion of Thiel cadavers can aid surgical and anatomical instruction. This study investigated whether ideal embalming circumstances provide lifelike vascular flow, enabling surgical practice and enhancing anatomical reality.

METHODS

Pressure-controlled pump-driven administration of blue embalming solution was assessed directly postmortem in a pig model (n = 4). Investigation of subsequent pump-driven vascular injection of red paraffinum perliquidum (PP) included assessment of flow parameters, intracorporeal distribution, anatomical alterations, and feasibility for surgical training. The microscopic distribution of PP was analyzed in pump-embalmed pig and gravity-embalmed human small intestines.

RESULTS

Embalming lasted 50-105 min, and maximum arterial pressure was 65 mm Hg. During embalming, the following consecutive alterations were observed: arterial filling, organ coloration, venous perfusion, and further tissue coloration during the next weeks. Most organs were adequately preserved. PP generated low arterial pressures (<30 mm Hg) and drained through the venous cannula. Generally, realistic reperfusion and preservation of original anatomy were observed, but leakage in the pleural, abdominal, and retroperitoneal cavities occurred, and computed tomography showed edematous spleen and liver. Reduction of arterial flow rates after venous drainage is a prerequisite to prevent anatomical deformation, allowing simulation of various surgeries. In pump-embalmed pig small intestines, PP flowed from artery to vein through the capillaries without extravasation. In contrast, arterioles were blocked in gravity-embalmed human tissues.

CONCLUSIONS

In a pig model, immediate postmortem pressure-controlled pump embalming generates ideal circumstances for (micro)vascular reperfusion with PP, permitting lifelike anatomy instruction and surgical training.

Eight free flaps in 24 hours: a training concept for postgraduate teaching of how to raise microvascular free flaps

Microvascular free flaps are complex but important tools in oral and maxillofacial surgery (OMFS), and though techniques to raise flaps are challenging surgeons often have little structured training. In this study we have evaluated a structured, three-day, hands-on, practical training course on raising flaps. Five human, Thiel-embalmed cadavers were used for training in how to raise the following flaps: radial forearm, anterolateral thigh, lateral arm, fibular, latissimus dorsi, scapular, iliac crest, and rectus abdominis. The total duration of the course was 24 hours over three days. All participants were asked to evaluate the design and conduct of the course, their own learning curve, and general questions about their knowledge of how to raise flaps and microsurgery. There was a significant increase in participants' assessments of how they raised all free flaps, except the lateral arm flap (4.74 (0.68) compared with 2.42 (0.81); p=0.052) before and after the course. The radial forearm flap was thought to be the most relevant in clinical practice (n=40; 75%), followed by the anterolateral thigh (n=5; 9%) and fibular (n=4; 8%) flaps. Comparisons between residents and consultants showed unsurprising differences in experience with microsurgery and self-assessment in raising particular free flaps before the course. We have shown that a structured, hands-on course using a well-established simulation model can significantly improve postgraduate surgeons' skills in raising free flaps.