A new microsurgical research model using Thiel-embalmed arteries and comparison of two suture techniques

Validation of Novel Microsurgical Vessel Anastomosis Techniques: A Systematic Review

INTRODUCTION

 Thorough validation of novel microsurgical techniques is deemed essential before their integration into clinical practice. To achieve proper validation, the design of randomized controlled trials (RCTs) should be undertaken, accompanied by the execution of comprehensive statistical analyses, including confounder adjustment and power analysis. This systematic review aims to provide an encompassing overview of the validation methodologies employed in microsurgical studies, with a specific focus on innovative vessel anastomosis techniques.

METHODS

 A literature search was conducted in PubMed for articles describing the validation of novel microsurgical vessel anastomosis techniques in animal or human subjects.

RESULTS

 The literature search yielded 6,658 articles. A total of 6,564 articles were excluded based on title and abstract. Ninety-four articles were assessed for full-text eligibility. Forty-eight articles were included in this systematic review. Out of 30 comparative studies, 9 studies validated novel modified interrupted suture techniques, 6 studies modified continuous techniques, 6 studies modified sleeve anastomosis techniques, 1 study a modified vesselotomy technique, 7 studies sutureless techniques, and 1 study a modified lymphaticovenular anastomosis technique. Twenty-eight studies contained animals (n = 1,998). Fifteen animal studies were RCTs. Two studies contained human/cadaveric subjects (n = 29). Statistical power analysis and confounder adjustment were performed in one animal study. Out of 18 noncomparative studies, 5 studies validated novel modified interrupted suture techniques, 1 study a modified continuous technique, 2 studies modified sleeve anastomosis techniques, 4 studies modified vesselotomy techniques, 4 studies sutureless techniques, and 2 studies modified lymphaticovenular anastomosis techniques. Ten studies contained animal subjects (n = 320), with two RCTs. Eight studies contained human subjects (n = 173). Statistical power analysis and confounder adjustment were performed in none of the animal or human studies.

CONCLUSION

 The current methods of microsurgical technique validation should be reconsidered due to poor study design. Statistical analysis including confounder adjustment and power analysis should be performed as a standard method of novel technique validation.

Thiel embalming in neonates: methodology and benefits in medical training

Current teaching and training methods for surgical techniques in the pediatric population involve artificial models (manikins), animals or adult human cadavers embalmed using various techniques. We found no references in the literature concerning the use of the Thiel method in the pediatric population. The aim of this study, therefore, was to assess the viability of using pediatric human cadavers embalmed through Thiel’s technique and to compare them with standard pediatric manikins. After donation of a 24-week stillborn, the Thiel technique was carried out for fixation following the usual protocol. A video recording with eye-tracking glasses was used to perform an examination, and techniques. The same procedures were conducted on a pediatric manikin. Medical students, medical residents and physicians were asked to respond to questions in an online survey after being shown the video. A total of 92 responses were obtained. The Thiel-embalmed stillborn was assessed as superior to the manikin in all items. Our study confirmed that this technique is feasible even with extremely small donors. The value of this form of preservation for medical training is not widely known though it is receiving increasing interest. Our results show that Thiel fixation in pediatrics is clearly more highly valued than a manikin and offers great potential. This innovative application of the Thiel method in the pediatric population is technically possible. It poses no additional difficulties and is very positively assessed for undergraduate and postgraduate teaching.

Thiel-embalmed porcine placenta: A valid and reusable microsurgical practice model

BACKGROUND

Simulation models are increasingly important for skill acquisition during microsurgery training. Prosthetics, living and non-living biological models have been proposed in the literature in the optics of recreating real-life scenarios in a controlled environment. This study aims to validate and prove the reusability of a novel non-living biological model: the porcine placenta.

METHODS

A prospective comparative study was carried out to assess face and content validities of the proposed model, as well as the reusability and quality of the Thiel-embalming method. Participants were asked answer a questionnaire for each anastomosis they performed on porcine placental vessels of ≤2mm (small) and 2-4mm (large). Scores were classified according to different subgroups, either small or large vessels and first or second sessions. Reliability analysis of the questionnaire was carried out using Cronbach's α, to ensure an α>0.7. Median scores for each question were analyzed using boxplots and compared amongst each subgroup using a non-parametric independent Mann-Whitney U test.

RESULTS

With nine participants, the Cronbach's α for each category of question was 0.867, 0.778, 0.720 and 0.593. Statistical differences were found between responses of small and large vessels on 5/10 questions, where large vessels reported higher validity. No statistical differences were found between scores of the first and second sessions.

CONCLUSION

By evaluating face and content validity, the Thiel-embalmed porcine placenta has proven its suitability as a microsurgery model, especially for vessels of larger caliber. Qualities that distinguish this model is its reliable reusability, its low cost-effectiveness, and its ethical acceptability.

High Fidelity Microsurgical Simulation: The Thiel Model and Evaluation Instrument

Background

The Thiel embalmment method has recently been used in a number of medical simulation fields. The authors investigate the use of Thiel vessels as a high fidelity model for microvascular simulation and propose a new checklist-based evaluation instrument for microsurgical training.

Methods

Thirteen residents and 2 attending microsurgeons performed video recorded microvascular anastomoses on Thiel embalmed arteries that were evaluated using a new evaluation instrument (Microvascular Evaluation Scale) by 4 fellowship trained microsurgeons. The internal validity was assessed using the Cronbach coefficient. The external validity was verified using regression models.

Results

The reliability assessment revealed an excellent intra-class correlation of 0.89. When comparing scores obtained by participants from different levels of training, attending surgeons and senior residents (Post Graduate Year [PGY] 4-5) scored significantly better than junior residents (PGY 1-3). The difference between senior residents and attending surgeons was not significant. When considering microsurgical experience, the differences were significant between the advanced group and the minimal and moderate experience groups. The differences between minimal and moderate experience groups were not significant. Based on the data obtained, a score of 8 would translate into a level of microsurgical competence appropriate for clinical microsurgery.

Conclusions

Thiel cadaveric vessels are a high fidelity model for microsurgical simulation. Excellent internal and external validity measures were obtained using the Microvascular Evaluation Scale (MVES).

Thiel-embalming technique: investigation of possible modification in embalming tissue as evaluation model for radiofrequency ablation

Contrary to freezing preservation and formalin embalming, Thiel embalmed cadaver presents soft texture and color very close to that of living organism, and many applications based on Thiel embalmed cadavers have been reported. However, Thiel embalmed cadavers cannot be used as reliable evaluation model for radiofrequency ablation (RFA) due to dramatic changes of electrical conductivity in the embalmed tissue. To address this issue, we investigated various modifications of the original Thiel embalming solution. By altering the chemicals' species and concentration we figured out a formula that can greatly reduce the embalming fluid's electrical conductivity without significantly compromising the 18-day embalmed kidney samples' suppleness and color. We also investigated a two-stage embalming technique by first submerging the kidney sample into original Thiel's tank fluid for 28 days, then the sample was withdrawn from the tank fluid and placed into modified dilution fluids for additional two weeks. Stiffening and discoloration occurred in these diluted samples implying the reversibility of Thiel-embalmed tissues' suppleness and color with the removal of the strong electrolytes. This study presents a modified embalming method which could be used for RFA evaluation and also helps our understanding of the mechanism of embalmment process.

Factors Correlating With Microsurgical Performance: A Clinical and Experimental Study

BACKGROUND

Microsurgery is one the most complex surgical skills to master. The factors correlating with microsurgical performance, however, are poorly understood. Understanding these factors will aid in the training and assessment of microsurgeons.

METHODS

A total of 29 microsurgery fellows enrolled in a dedicated 1-year microsurgery fellowship were included in the study. For the clinical evaluations, microsurgical anastomosis performance was evaluated during multiple procedures in the operating room at the start, midpoint, and end of the fellowship by all departmental faculty using a validated microsurgical assessment tool. For the laboratory evaluations, blinded video recordings of each fellow performing an arterial femoral anastomosis in a live rat model at the start and end of the fellowship were evaluated using 3 validated microsurgical global ratings scale tools. Correlations between performance and the factors assessed by the tools were evaluated.

RESULTS

In the clinical study there were a total of 474 anastomosis evaluations; clinical performance correlated best with speed, instrument handling, and motion. In the laboratory study 58 evaluations were conducted, and performance tracked most closely with instrument handling, flow of operation, and operative steps, as well as correlating significantly inversely with time taken. The most common errors committed were unequal stitch bites, wrong grasp/damage tissue, and loose knot.

CONCLUSIONS

Speed, both subjective and objective, instrument handling, operative flow, and motion, were relevant to performance of a microsurgical anastomosis. A prospective trial is now necessary to determine whether these factors should be considered in definitions of competency in microsurgery training pathways.

Defining Standards in Experimental Microsurgical Training: Recommendations of the European Society for Surgical Research (ESSR) and the International Society for Experimental Microsurgery (ISEM)

Background: Expectations towards surgeons in modern surgical practice are extremely high with minimal complication rates and maximal patient safety as paramount objectives. Both of these aims are highly dependent on individual technical skills that require sustained, focused, and efficient training outside the clinical environment. At the same time, there is an increasing moral and ethical pressure to reduce the use of animals in research and training, which has fundamentally changed the practice of microsurgical training and research. Various animal models were introduced and widely used during the mid-20th century, the pioneering era of experimental microsurgery. Since then, high numbers of ex vivo training concepts and quality control measures have been proposed, all aiming to reduce the number of animals without compromising quality and outcome of training. Summary: Numerous microsurgical training courses are available worldwide, but there is no general agreement concerning the standardization of microsurgical training. The major aim of this literature review and recommendation is to give an overview of various aspects of microsurgical training. We introduce here the findings of a previous survey-based analysis of microsurgical courses within our network. Basic principles behind microsurgical training (3Rs, good laboratory practice, 3Cs), considerations around various microsurgical training models, as well as several skill assessment tools are discussed. Recommendations are formulated following intense discussions within the European Society for Surgical Research (ESSR) and the International Society for Experimental Microsurgery (ISEM), based on scientific literature as well as on several decades of experience in the field of experimental (micro)surgery and preclinical research, represented by the contributing authors. Key Messages: Although ex vivo models are crucial for the replacement and reduction of live animal use, living animals are still indispensable at every level of training which aims at more than just a basic introduction to microsurgical techniques. Modern, competency-based microsurgical training is multi-level, implementing different objective assessment tools as outcome measures. A clear consensus on fundamental principles of microsurgical training and more active international collaboration for the sake of standardization are urgently needed.

Ureterorenoscopy training on cadavers embalmed by Thiel's method: simulation or a further step towards reality? Initial report

Introduction

The technique of ureterorenoscopy has a significant learning curve. Cadavers embalmed by the Thiel method have been successfully used for simulation training in a number of surgical specialties. Here we present our experience of the first use of Thiel cadavers in a formal ureteroscopy training course.

Material and methods

The inaugural ‘Masterclass in Flexible Ureterorenoscopy’ was run with participants performing ureterorenoscopy on three Thiel cadavers under expert supervision. A qualitative questionnaire was delivered to the participants and faculty. Assessed domains were tissue characteristics of the cadaveric urinary tract, anatomical features and procedural aspects. A five-point Likert score was used to assess responses. Data regarding participant experience in endourology were also collected.

Results

8 questionnaires were collected. All participants completed cadaveric ureterorenoscopy. Three-quarters reported the overall quality of tissue in the cadaveric bladder, ureters and pelvicalyceal system as high or excellent. Half reported the cadaveric bladder as being softer than in a live patient, whilst five out of eight thought that the cadaveric ureter was softer and more prone to trauma. Seven out of eight were satisfied with the overall quality of the cadaveric model. The quality of vision and irrigation in the upper urinary tracts was reported as high.

Conclusions

Thiel cadavers have been shown to have excellent tissue characteristics, as well as being durable and reusable. We have described the first use of Thiel cadavers in a designated ureterorenoscopy course, with high levels of delegate satisfaction. Further work is required to develop the role of Thiel cadavers as part of an integrated, modular urology training.

Comparison of Biomechanical and Histological Outcomes of Different Suture Techniques in Rat Rectus Abdominis Muscle Repair

The aim of this study was to determine the strongest suture technique that retains the most muscle thickness to obtain functional outcome for Sprague-Dawley rat rectus abdominis muscle repair. We exposed the paired rectus abdominis muscle of 32 Sprague-Dawley rats on both sides (n = 64) and cut transversely. Immediate closure of the muscle was performed using one of 4 different suture methods (group A: interrupted suture, group B: horizontal mattress suture, group C: vertical mattress suture, group D: overlapping suture). After 8 weeks, the sutured muscle was dissected and cut for evaluation of tensile strength and muscle thickness. Histologic findings were evaluated using automatic quantitative component image analysis software (i-Solution) and immunohistochemical staining using CD31. P values were based on the Mann-Whitney test and Bonferroni correction. Group A showed the strongest tensile strength (P < 0.001). This group also demonstrated the greatest muscle thickness in comparison to the other groups. Differences between group A and the other groups were statistically significant (P < 0.001). Group A showed the highest ratio of muscle fibers and demonstrated the highest expression of CD31 (P < 0.05). The interrupted suture method used for muscle closure shows the greatest tensile strength and muscle thickness and is therefore a good option for suturing skeletal muscle. This finding has clinical applicability for suturing in the repair of skeletal muscle, especially for congenitally dehisced muscle repair.

Horizontal mattress technique for anastomosis of size-mismatched vessels

OBJECTIVE

To evaluate the horizontal mattress technique in microvascular anastomosis for size-mismatched vessels.

METHODS

The present study involved cadaveric simulation using size-mismatched (1.5:1) Thiel-embalmed cadaveric arteries. The authors performed horizontal mattress anastomoses using 9-0 nylon suture and recorded the procedure. Vessel patency was evaluated by saline infusion. Vessels were cut open and photographed; histological slides were prepared and stained with hematoxylin and eosin.

RESULTS

Four anastomoses were performed. Vessels were found to be patent in all cases, with grade 0 leaks. Intima-on-intima apposition with no intraluminal exposure of muscularis nor adventitia were observed.

CONCLUSION

The present cadaveric study supports the technical feasibility of using horizontal mattress sutures in size-mismatched end-toend anastomoses.

Horizontal mattress technique for anastomosis of size-mismatched vessels

Objective

To evaluate the horizontal mattress technique in microvascular anastomosis for size-mismatched vessels.

Methods

The present study involved cadaveric simulation using size-mismatched (1.5:1) Thiel-embalmed cadaveric arteries. The authors performed horizontal mattress anastomoses using 9-0 nylon suture and recorded the procedure. Vessel patency was evaluated by saline infusion. Vessels were cut open and photographed; histological slides were prepared and stained with hematoxylin and eosin.

Results

Four anastomoses were performed. Vessels were found to be patent in all cases, with grade 0 leaks. Intima-on-intima apposition with no intraluminal exposure of muscularis nor adventitia were observed.

Conclusion

The present cadaveric study supports the technical feasibility of using horizontal mattress sutures in size-mismatched end-to-end anastomoses.