Effect of the two-wall-stitch mistake upon patency of rat femoral vein anastomosis: Preliminary observations

Rat Microvascular Model is Tolerant to Technical Errors

BACKGROUND

 Extensive studies have been conducted using the rat model to understand the potential technical errors that lead to anastomotic failure. However, current literature indicates that the rat model has excellent tolerance to diverse errors committed by microsurgeons. The error-investigating rat model is often created by one or two experienced surgeons, and only one isolated technical error is examined. These biases may potentially cause limitations of the results from previous studies. Meanwhile, venous anastomoses have rarely been investigated in previous literature. Therefore, it is important to elucidate this topic with a more comprehensive study design.

METHODS

 Ninety-four arterial and 94 venous anastomoses on Sprague-Dawley rat femoral vessels that were performed by 47 microsurgeons who participated in the microsurgery course at the Columbia University and the University of Thessaloniki were evaluated. In total, 10 technical errors were examined: (1) disruption of suture line, (2) back-wall stitch, (3) oblique stitch, (4) wide bite, (5) partial thickness bite, (6) unequal suture distance, (7) tear in vessel wall, (8) excessively tight suture, (9) suture threads in lumen, and (10) large edge overlap. The frequency of each error committed, and the 30-minute postoperative patency was also recorded. The underlying causal relationship between these errors, potential interaction, and the short-term anastomosis patency was analyzed statistically.

RESULTS

 Only the back-wall stitch was found to have a significant causal effect on arterial anastomosis failure (p < 0.001). Back-wall stitch, wide bite, and partial thickness bite significantly impact venous anastomosis patency (p < 0.001). No other statistically significant result was found.

CONCLUSION

 Overall, the rat model is highly resilient to various technical errors despite these mistakes being often considered clinically unacceptable. Therefore, researchers need to consider the resilience of the rat model when designing and analyzing future studies. In addition, microsurgery instructors should focus on individual stitch quality rather than the final patency.

Microsurgical Anastomosis Rating Scale (MARS10): A Final Product Scoring System for Initial Microsurgical Training

Background

High cost and ethical controversy of using living models in microsurgical training made non-living models more popular. However, non-living models don't provide appropriate feedback of microsurgical performance. Currently existing Global Rating Scales used for advanced microsurgical skills validation are difficult to apply on non-living model. This study presents a simple instrument for basic assessment of microsurgical anastomosis on non-living model.

Methods

Seventy medical students were divided into 2 groups depending on their prior microsurgical experience. Each participant performed 3 end-to-end anastomoses on chicken femoral artery model. Anastomoses were reviewed by 3 blinded experts and then photographed. Evaluation included a patency tests, longitudinal cut of anastomosis, and the newly proposed tool 10 Point Microsurgical Anastomosis Rating Scale (MARS10). Presented scale consists of 5 factors important for anastomosis closure (anastomosis closure, suture spacing, bites size, knot tying, and cut ends length), graded on 3 point scale (0-2 points). Results were analyzed with analysis of variance, Spearman correlation, and t Student test.

Results

Anastomoses evaluated by experts as patent significantly correlated with a high summary score in MARS10 scale (r = 0.73 P < .0001). There was a significant difference in MARS10 score between groups (P < .0001). There were no significant inter-rater differences in scoring among all 3 evaluators (p > .05).

Conclusions

10 Point Microsurgical Anastomosis Rating Scale is a quick, valid, and reliable tool to assess microsurgical end-to-end arterial anastomoses on non-living model.

A sequence of flaps and dissection exercises in the living model to improve the learning curve for perforator flap surgery

INTRODUCTION

The training to learn how to perform perforator flaps requires practice on a living model to optimize dissection and to evaluate outcome. The purpose of this study was to describe a training model that optimizes the use of animals in order to perform the maximum number of exercises per animal.

MATERIAL AND METHODS

The sequence has been planned and practiced by the first and last author, recorded perfected and implemented in a two-day surgical course. The sequence was then evaluated by the trainers and the trainees by means of a questionnaire.

RESULTS

All students were able to complete the sequence of exercises before the end of the second day except two (8/10) who could not complete one exercise each. The students considered the Deep Superior Epigastric Artery Perforator flap the most difficult to perform, being the most technically demanding. The sequence of exercises was judged either easily reproducible or reproducible by all the students. Two students suggested to postpone the DSEAP flap to the second day, after some training, to optimize the experience with the most challenging and rewarding flap.

CONCLUSIONS

The training sequence proposed offers a wide range of exercises and allows four trainees, divided in two teams, to work and learn on the same animal. They can perform a wide range of flaps and also harvest the internal mammary vessels. The living model allows for evaluation of the quality of the surgical performance, judged by the difficulties and complications encountered during dissection, and finally through the feedback of flap perfusion.

Predictive value of the milking patency test when performing the arterial microanastomosis in head and neck surgery

BACKGROUND

The milking patency test (MPT) is widely used to assess the patency of microanastomosis, despite it being proven to be a traumatic test.

METHODS

We performed microanastomoses with intentional two-wall stitches and asked senior microsurgeons to evaluate the permeability of the anastomoses by looking first at the results of the MPT, then according to artery pulsation.

RESULTS

Microsurgeons were all accurate in evaluating normal or clamped anastomoses. But in anastomoses with defects, the MPT was considered normal 94%, 85%, and 73%. MPT has a positive predictive value of 100% but with a negative predictive value of 27.5%. Observation of the artery pulsation distal to the anastomosis gave similar results.

CONCLUSIONS

Our experiment shows that the two-wall stitches on arterial anastomoses are hardly detected by an MPT. The observed pulsation of the artery gives the same results and could be used instead, without damaging the vessels.

Effect of Previous Irradiation on Vascular Thrombosis of Microsurgical Anastomosis: A Preclinical Study in Rats

BACKGROUND

The objective of the present investigation was to compare the effect of neoadjuvant irradiation on the microvascular anastomosis in cervical bundle using an experimental model in rats.

METHODS

One hundred forty male Sprague-Dawley rats were allocated into 4 groups: group I, control, arterial microanastomosis; group II, control, venous microanastomosis; group III, arterial microanastomosis with previous irradiation (20 Gy); and group IV, venous microanastomosis with previous irradiation (20 Gy). Clinical parameters, technical values of anastomosis, patency, and histopathological parameters were evaluated.

RESULTS

Irradiated groups (III and IV) and vein anastomosis groups (II and IV) showed significantly increased technical difficulties. Group IV showed significantly reduced patency rates (7/35) when compared with the control group (0/35). Radiotherapy significantly decreased the patency rates of the vein (7/35) when compared with the artery (1/35). Groups III and IV showed significantly reduced number of endothelial cells and also showed the presence of intimal thickening and adventitial fibrosis as compared with the control group.

CONCLUSION

Neoadjuvant radiotherapy reduces the viability of the venous anastomosis in a preclinical rat model with a significant increase in the incidence of vein thrombosis.

Vascular anatomy of the hamster retractor muscle with regard to its microvascular transfer

BACKGROUND

The hamster retractor muscle (RET) is used as an in vivo model in studies of skeletal muscle ischemia-reperfusion injury. The RET is unique in that the muscle can be isolated while preserving the primary vascular supply so that its contractile function can be measured simultaneously with local microvascular responses to experimental interventions. The goal of this study was to understand the anatomical origin of the vascular supply to the RET and determine whether the RET can be used as a free flap after surgical isolation of the thoracodorsal vessels.

METHODS

Microdissection was performed to determine the anatomy of the vasculature that supplies and drains the RET.

RESULTS

Distinct numbers and patterns of feed arteries (2-4) and collecting veins (1-3) were identified (n = 26 animals). Dye injection (n = 8) of the thoracodorsal artery demonstrated that the RET remains perfused following its isolation on the thoracodorsal pedicle. Heterotopic allograft transplantation of the RET (n = 2) was performed by anastomosing the thoracodorsal vessels to the femoral vessels using the end-to-side technique.

CONCLUSIONS

The anatomical relationships indicate that the RET can be used as a free flap model for evaluating the effect of preservation strategies and transplantation on skeletal muscle microcirculation and contractile function.

Thrombotic effect of purposeful back-wall stitch for different suture locations and vessels in rats

Many microsurgeons experience inadvertent back-wall stitch as a cause of immediate anastomotic failure. To investigate this factor as a possible cause of delayed arterial anastomotic failure that does not appear in the operation room, a purposeful back-wall stitch (PBWS) model of microarterial anastomosis was applied in various configurations on femoral and carotid arteries of rats. Carotid (n = 28) and femoral (n = 28) artery groups were equally divided into 4 different subgroups according to the type of PBWS. Control subgroups had no PBWS. Thirty-degree, 60-degree, and 90-degree subgroups had PBWS located at 30, 60, and 90 degrees, respectively. Patencies were assessed at 60 minutes and 24 hours. Immediate milking test demonstrated normal anterograde refilling in all anastomoses. PBWS increased thrombosis in femoral arteries, while it did not increase it in the carotid at either evaluation times. The only significant difference was between 90 degrees PBWS and the control subgroup irrespective of the vessel factor in 24 hours. Histologic examination supported absence of thrombosis, as suggested by surgical examination. This may show that small-sized arteries are more inclined to thrombosis compared with larger ones and the thrombosis risk increases as the inadvertent back-wall stitch is more centrally located. Contrary to general notion that the inadvertent back-wall stitch causes immediate thrombosis, thromboses later than 1 hour, and even patent anastomoses in 24 hours, were observed in femoral and carotid artery groups. This study suggests that the inadvertent back-wall stitch should also be considered as a possible cause of late anastomotic problems.