Transfer of Learning from Practicing Microvascular Anastomosis on Silastic Tubes to Rat Abdominal Aorta

Modeling the Microsurgical Learning Curve Using a Poisson-Based Statistical Approach for Skill Assessment

OBJECTIVE

 The learning curve (LC), a multifaceted concept, plays a pivotal role in evaluating surgical training. This study aimed to define critical inflection points in the microsurgical learning curve, develop a reliable index for skill assessment, and statistically validate this approach using Poisson distribution theory.

METHOD

 A standardized microsurgical training protocol was employed using a biological simulator. Data regarding time to complete the task and error rates were collected over 132 attempts by a single operator. The primary outcome variable, the major mistake average (MMA), was used to generate a learning curve. Its progression was analyzed using autoregressive integrated moving average (ARIMA) modeling and validated with Poisson dispersion theory to determine the randomness of error occurrence at advanced stages of training. The entire trial was conducted by a single operator, a consultant neurosurgeon from our institution, who had been properly instructed on the protocol and the corresponding operator's manual.

RESULTS

 Task completion time (TCT) ranged from 860 to 3,054 seconds (mean: 1,472 seconds; R² = 0.561). MMA peaked at the 19th attempt (0.263) and decreased progressively, reaching 0.091 by the 132nd attempt (R² = 0.835). Three distinct phases of learning were identified, culminating in a plateau phase during which major mistakes followed a Poisson distribution (Chi² = 3.841), suggesting random occurrence independent of skill deficits.

CONCLUSION

 The MMA was found to be a robust and objective indicator of microsurgical proficiency. Its statistical validation using Poisson distribution theory supports its utility in skill assessment and training programs. Further studies involving multiple operators are warranted to confirm these findings.

Learning Curve of Microsurgical Anastomosis: Training for Resident Education

BACKGROUND

Acquiring microsurgical anastomosis skills requires considerable time and effort. Moreover, appropriate and systematic training for acquiring microsurgical anastomosis skills is lacking. Therefore, this study investigated the learning curve for acquiring microsurgical anastomosis techniques among orthopaedic surgery residents.

METHODS

The study involved 12 orthopaedic surgery residents without experience in microsurgical anastomosis. The residents were divided into two groups: the 'Experienced group' with more than 6 months of suturing experience and the 'Inexperienced group' with no suturing experience. Each participant underwent 30 practice sessions, suturing a 3.5-mm diameter silastic tube. The time taken for each anastomosis and its quality were evaluated. Individual learning curves were derived, and the number of trials required to reach the time plateau was determined.

RESULTS

The Experienced group reached the time plateau after an average of 16.3 ± 1.4 attempts while the Inexperienced group reached it after an average of 24.2 ± 2.5 attempts. The time required for the first two attempts was 40.4 ± 6.2 min for the Experienced group and 61.2 ± 8.6 min for the Inexperienced group (P < 0.001). The time required for the last two attempts was 11.4 ± 0.7 min for the Experienced group and 12.8 ± 0.8 min for the Inexperienced group. Comparing the quality scores of the first two attempts, the Experienced group scored 4.3 ± 0.5 points and the Inexperienced group scored 3.1 ± 0.5 points (P < 0.001). The Experienced group scored 7.8 ± 0.5 points for the last two attempts while the Inexperienced group scored 6.9 ± 0.3 points (P < 0.001).

CONCLUSIONS

Individuals new to suturing improved anastomosis time and quality by approximately 30 times. This finding suggests that practitioners can optimize their training while educators can refine the curriculum by predicting learning curves and providing timely feedback to enhance skill development.

Intensive 2-days training on perfused human placenta for microvascular anastomoses

BACKGROUND AND PURPOSE

We report on an intensive two-day training program on microanastomoses performed on perfused human placenta models. A specific scoring system was elaborated to evaluate the participants' microsurgical skills and report the participants' results.

MATERIALS AND METHODS

Trainees who attended the Zurich Microsurgery Courses in 2023 were included in the study. Before performing the microanastomoses, each participant received a visual didactic training. Training was made on perfused human placenta models. To perform the microvascular anastomoses, vessels of different diameters were chosen, and 9-0 and 10-0 microsutures were used. The course was structured in two days. On day one, participants practiced microvascular dissection, microsuturing and end-to-end anastomoses, while the second day was dedicated to end-to-side and to repeat the most useful microanastomosis depending on the specialty. A score system for the evaluation of a successful microanastomosis was developed and applied to assess the participants' anastomoses. User satisfaction was measured by means of a survey-based questionnaire.

RESULTS

Fifty-two participants from different institutions, specializations and levels of experience were included. A significant improvement in the overall microsurgical skills of the included cohort was documented (p < 0.005). The initial average score per anastomosis of 3.56 points (SD 0.71) increased to an average of 3.8 points (SD 0.87) at the end of the course. The steepest learning curve was observed in the placement of knots (Δ 0.48 points, p = 0.003) and microvascular dissection (Δ 0.44 points, p = 0.002). Most participants rated the fidelity and importance of the placental microsuturing course as extremely high.

CONCLUSION

The two-day training program is efficient to teach microvascular dissection and microanastomosis techniques. A significant improvement of participants' microsurgical skills was reported. The human placenta model proved to be a high-fidelity simulator with great user satisfaction.

Neurosurgical Microvascular Anastomosis: Systematic Review of the Existing Simulators and Proposal of a New Training Classification System

BACKGROUND

The literature lacks a combined analysis of neurosurgical microvascular anastomosis training models. We performed a systematic literature search to provide an overview of the existing models and proposed a classification system based on the level of simulation and reproducibility of the microvascular anastomosis.

METHODS

The systematic literature search followed the PRISMA guidelines. We consulted MEDLINE, Web of Knowledge, and EMBASE independently for papers about bypass training models. Every training model was analyzed according to six tasks supposed to esteem their fidelity to the real operative setting by using a scoring system from zero to two. Finally, authors classified the models into five classes, from A to E, by summing the individual scores.

RESULTS

This study included 109 papers for analysis. Training models were grouped into synthetic tubes, ex vivo models (animal vessels, fresh human cadavers, human placentas) and in vivo simulators (live animals-rats, rabbits, pigs). By applying the proposed classification system, live animals and placentas obtained the highest scores, falling into class A (excellent simulators). Human cadavers and animal vessels (ex vivo) were categorized in class B (good simulators), followed by synthetic tubes (class C, reasonable simulators).

CONCLUSIONS

The proposed classification system helps the neurosurgeon to analyze the available training models for microvascular anastomosis critically, and to choose the most appropriate one according to the skills they need to improve.

Validation of a dynamic 4D microsurgical bypass simulator for training and teaching microvascular anastomosis techniques with blood flow and fluorescence imaging

Objective

Microvascular anastomosis is challenging, and training surgeons to develop and maintain skills is imperative. Current training models either miss the simulation of the surgical workflow, lack 3D key-hole space, need ethical approval, require special preparation, or lack realism. To circumvent these issues, this study describes the use of a mixed reality 3D printed model with integrated blood flow for training cerebral anastomosis and assesses its validity.

Methods

Different-sized 3D-printed artificial micro artery models in a 3D brain space with a keyhole opening were used. The model was connected to a 4D simulator to induce pulsatile blood flow. Neurosurgical microscopes and exoscopes were used for visualization. Nine participants (n = 6 board-certified cerebrovascular neurosurgeons; n = 3 in-training) participated in the study and practiced anastomosis techniques with the simulator. Two senior, experienced vascular neurosurgeons mentored live teaching activity on the simulator. Participants completed a survey to score the face and content validity of the simulation on a 5-point Likert scale. Simulation time and anastomosis score differences between in-training and board-certified participants were compared for construct validity.

Results

Participants scored the simulation difficulty similar to actual surgery, proving face validity. All participants agreed that practice on the provided simulator models would improve bypass techniques (μ = 4.67/5 ± 0.47) and instrument handling (μ = 4.56/5 ± 0.68). Board-certified participants had better anastomosis scores than in-training participants (non-significant difference).

Conclusions

The 4D simulator and the high-fidelity artificial 3D printed model effectively simulated actual bypass surgery in a key-hole fashion with blood flow abilities. Limited resources and preparation time are needed for the training setup. The model provides benefits in learning and maintaining anastomosis skills and allows for easy adaptation to different microanatomical scenarios.

A novel latex patch model enables cost-effective hands-on teaching in vascular surgery

Objectives

We developed a new simulator for hands-on teaching of vascular surgical skills, the Leipzig Latex Patch Model (LPM). This study aimed to quantify the effectiveness and acceptance of the LPM evaluated by students, as well as evaluation of the results by experienced vascular surgeons.

Methods

A prospective, single-center, single-blinded, randomized study was conducted. Fifty 5th-year medical students were randomized into two groups, first performing a patch suture on the LPM (study group) or established synthetic tissue model (control), then on porcine aorta. The second suture was videotaped and scored by two surgeons using a modified Objective Structured Assessment of Technical Skill (OSATS) score. We measured the time required for suturing; the participants completed questionnaires.

Results

Participants required significantly less time for the second suture than the first (median: LPM 30 min vs. control 28.5 min, p = 0.0026). There was no significant difference in suture time between the groups (median: 28 min vs. 30 min, p = 0.2958). There was an increase in confidence from 28 % of participants before to 58 % after the course (p < 0.0001). The cost of materials per participant was 1.05€ (LPM) vs. 8.68€ (control). The OSATS-scores of the LPM group did not differ significantly from those of the control (median: 20.5 points vs. 23.0 points, p = 0.2041).

Conclusions

This pilot study demonstrated an increase in technical skills and confidence through simulator-based teaching. Our data suggests comparable results of the LPM compared to the conventional model, as assessed by the OSATS-score. This low-cost, low-threshold training model for vascular suturing skills should make hands-on training more accessible to students and surgical residents.

Key message

We developed and validated a low-cost, low-threshold training model for vascular suturing skills. This should make hands-on training more accessible to medical students and surgical residents in the future.

Egg membrane as a training model for microsurgery

Teaching microsurgery is limited by the availability of appropriate training models. In-vivo models, such as rats, remain the gold standard, but ethical and economic limitations restrict their use for initial training. This study investigated the feasibility of using egg membrane as an inert model, an accessible and economical alternative for introduction to microsurgery. The specifications for inert models include ease of access, low cost, high reproducibility and realistic reproduction of relevant characteristics. Fourteen microsurgery students assessed egg membrane as an inert training model on a 10-item questionnaire evaluating the specifications for use in microsurgery teaching. Easy access to the material and the ease with which it could be set up were evaluated positively. Dissection of the membrane added an educational dimension, distinguishing this model from other inert alternatives. On the other hand, the flexibility of the egg membrane and its resistance to the passage of the needle or the tightening of the thread were generally considered to be different from the in-vivo arterial wall. In conclusion, egg membrane as an inert model offers a practical, economical alternative in microsurgery training despite a lack of fidelity in reproducing the most relevant characteristics of the arterial wall. This model is more suited to the initial phase of learning microsurgery: in particular, working under a microscope, eye/hand coordination, tremor management and digital dexterity.

Learning curve and influencing factors of performing microsurgical anastomosis: a laboratory prospective study

Despite being a critical component of any cerebrovascular procedure, acquiring skills in microsurgical anastomosis is challenging for trainees. In this context, simulation models, especially laboratory training, enable trainees to master microsurgical techniques before performing real surgeries. The objective of this study was to identify the factors influencing the learning curve of microsurgical training. A prospective observational study was conducted during a 7-month diploma in microsurgical techniques carried out in the anatomy laboratory of the school of surgery. Training focused on end-to-end (ETE) and end-to-side (ETS) anastomoses performed on the abdominal aorta, vena cava, internal carotid and jugular vein, femoral artery and vein, caudal artery, etc. of Wistar strain rats under supervision of 2 expert anatomical trainers. Objective and subjective data were collected after each training session. The 44 microsurgical trainees enrolled in the course performed 1792 anastomoses (1577 ETE, 88%, vs. 215 ETS, 12%). The patency rate of 41% was independent from the trainees' surgical background and previous experience. The dissection and the temporary clamping time both significantly decreased over the months (p < 0.001). Technical mistakes were independently associated with thrombosis of the anastomoses, as assessed by the technical mistakes score (p < 0.01). The training duration (in weeks) at time of each anastomosis was the only significant predictor of permeability (p < 0.001). Training duration and technical mistakes constituted the two major factors driving the learning curve. Future studies should try and investigate other factors (such as access to wet laboratory, dedicated fellowships, mentoring during early years as junior consultant/attending) influencing the retention of surgical skills for our difficult and challenging discipline.

Mind the Gap: a Competency-Based Scoping Review of Aesthetic and Reconstructive Reported Simulation Training Models

BACKGROUND

Simulation training has become an integral part of plastic surgery postgraduate curricula. It facilitates the acquisition of skills in a safe environment that can be later transferred to real-life settings. A variety of models have been described covering some aspects of the specialty better than others. The aim of this study was to identify and classify all the previously reported plastic surgery simulation models and the possible gaps having the Accreditation Council for Graduate Medical Education (ACGME) list of competencies as a guide.

METHODS

Through a Delphi process, the complete list of ACGME minimum requirements for certification was analyzed to identify domains amenable for simulation training. A systematic search was conducted in Pubmed looking for all previously reported simulation models in plastic surgery. Predefined inclusion and exclusion criteria and parallel blind review were used to identify eligible models.

RESULTS

A total of 81 ACGME competencies were identified. Following a 3-round Delphi process, consensus was reached on 19 reconstructive and 15 aesthetic surgery domains suitable for simulation training. 1667 articles were initially retrieved from Pubmed, of which 66 articles were eligible for inclusion. Descriptive (65%), quasi-experimental (24%) and experimental studies (11%) were found. For the 34 identified ACGME competencies, there were simulation models described for 58.8% of these, mostly covering reconstructive surgery (84.2%) while for aesthetic surgery it was 13.3%.

CONCLUSIONS

This scoping review has identified that there are still gaps in ACGME competencies that could benefit from new simulation training models, especially in those related to aesthetic surgery.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Developing microsurgical milestones for psychomotor skills in neurological surgery residents as an adjunct to operative training: the home microsurgery laboratory

OBJECTIVE

A variety of factors contribute to an increasingly challenging environment for neurological surgery residents to develop psychomotor skills in microsurgical technique solely from operative training. While adjunct training modalities such as cadaver dissection and surgical simulation are embraced and practiced at our institution, there are no formal educational milestones defined to help residents develop, measure, and advance their microsurgical psychomotor skills in a stepwise fashion when outside the hospital environment. The objective of this report is to describe an efficient and convenient "home microsurgery lab" (HML) assembled and tested by the authors with the goal of supporting a personalized stepwise advancement of microsurgical psychomotor skills.

METHODS

The authors reviewed the literature on previously published simulation practice models and designed adjunct learning modules utilizing the HML. Five milestones were developed for achieving proficiency with each graduated exercise, referencing the Accreditation Council for Graduate Medical Education (ACGME) guidelines. The HML setup was then piloted with 2 neurosurgical trainees.

RESULTS

The total cost for assembling the HML was approximately $850. Techniques for which training was provided included microinstrument handling, tissue dissection, suturing, and microanastomoses. Five designated competency levels were developed, and training exercises were proposed for each competency level.

CONCLUSIONS

The HML offers a unique, entirely home-based, affordable adjunct to the operative neurosurgical education mandated by the ACGME operative case logs, while respecting resident hospital-based education hours. The HML provides surgical simulation with specific milestones, which may improve confidence and the microsurgical psychomotor skills required to perform microsurgery, regardless of case type.

Constructing an Individualized Middle Cerebral Artery Model Using 3D Printing and Hydrogel for Bypass Training

The importance and complexity of cerebral bypass surgery (CBS) highlight the necessity for intense and dedicated training. Several available training models are yet to satisfy this need. In this technical note, we share the steps to construct a digital imaging and communications in medicine (DICOM)-based middle cerebral artery (MCA) model that is anatomically accurate, resembles handling properties of living tissue, and enables trainers to observe the cerebrovascular anatomy, improve and maintain microsurgical dexterity, and train in the essential steps of CBS. The internal and external molds were created from the geometry of DICOM-based MCA using Fusion 360 software (Autodesk, San Rafael, USA). They were then three-dimension (3D) printed using a polylactic acid filament. The 15% w/v solution of polyvinyl alcohol (PVA) was prepared and injected between the molds. Using five freeze-thaw cycles the solution was converted to tissue-mimicking cryo-gel. The model was then placed in a chloroform bath until the internal mold dissolved. To evaluate the accuracy of the MCA model, selected characteristics were measured and compared with the MCA mesh. The DICOM-based MCA model was produced using 3D printing that was available in the lab and the overall cost was less than $5 per model. The external mold required six and a half hours to be 3D printed, while the internal mold only required 23 minutes. Overall, the time required to 3D print the DICOM-based MCA model was just short of seven hours. The greatest statistically significant difference between the virtual MCA model and the DICOM-based MCA model was found in the length of the pre-bifurcation part of the M1 segment and the total length of the superior bifurcation trunk of M1 and superior branch of M2. The smallest statistically significant difference was found at the diameter of the inferior post-bifurcation trunk of the M1 segment and the diameter at the origin of the artery. This technical report aims to show the construction of a CBS training system involving the DICOM-based MCA model that demonstrates the shape of the vascular tree, resembles the handling/suturing properties of living tissue, and helps set up a homemade training station. We believe that our DICOM-based MCA model can serve as a valuable resource for CBS training throughout the world due to its cost-effectiveness and straightforward construction steps. Moreover, once the DICOM-based MCA model is used with our training station, it may offer an option for trainers to gain and maintain CBS skills despite limitations on time, cost, and space. This work was presented in February 2019 at the American Association of Neurological Surgeons/Congress of Neurological Surgeons (AANS/CNS) Cerebrovascular Section Annual Meeting held in Honolulu, Hawaii.

Learning microvascular anastomosis: Analysis of practice patterns

BACKGROUND

Performing a successful microsurgical vascular anastomosis (MVA) is challenging and requires lots of practice. However, the most efficient practice protocol is yet to be found. We aimed to compare and analyze two major practice patterns for fine motor tasks as applied to learning MVA: distributed and mass practice protocols. Ten neurosurgeons with comparable experience in microsurgery (but no experience in vascular anastomosis) were randomized to practice MVA either using a distributed (1 session/day) or a mass practice (6 sessions/day) protocol. A total of 24 sessions of practice and 2 recall test sessions were given. Anastomosis score, time to complete a single stitch and the total time to complete an anastomosis were recorded. Mass practice protocol caused a clear fatigue effect observed toward the end of each mass practice trial block. Statistical comparison using one-way analysis of variance showed significantly higher anastomosis scores and shorter times to place a single stitch as well as to complete the anastomosis in distributed practice group for the last 3 acquisition practice trials, and the 2 recall tests (p < 0.05). The relative advantage of the distributed practice protocol could be attributed to forgetting/spacing effect. Although mass practice protocol resulted in worse performance, it still showed a gradual improvement trend in performance from beginning to the end. Therefore, certain adjustments to a mass practice protocol (such as increasing the number of practice blocks) could potentially lead to an eventual performance level comparable to a distributed protocol. This point is a subject of further investigation.

Superiority of living animal models in microsurgical training: beyond technical expertise

Background

Many studies are investigating the role of living and nonliving models to train microsurgeons. There is controversy around which modalities account for the best microsurgical training. In this study, we aim to provide a systematic literature review of the practical modalities in microsurgery training and compare the living and nonliving models, emphasizing the superiority of the former. We introduce the concept of non-technical skill acquisition in microsurgical training with the use of living laboratory animals in the context of a novel proposed curriculum.

Methods

A literature search was conducted on PubMed/Medline and Scopus within the past 11 years based on a combination of the following keywords: “microsurgery,” “training,” “skills,” and “models.” The online screening process was performed by two independent reviewers with the Covidence tool. A total of 101 papers was identified as relevant to our study. The protocol was reported in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.

Results

Living models offer the chance to develop both technical and non-technical competencies (i.e., leadership, situation awareness, decision-making, communication, and teamwork). Prior experience with ex vivo tissues helps residents consolidate basic skills prior to performing more advanced techniques in the living tissues. Trainees reported a higher satisfaction rate with the living models.

Conclusions

The combination of living and nonliving training microsurgical models leads to superior results; however, the gold standard remains the living model. The validity of the hypothesis that living models enhance non-technical skills remains to be confirmed.

Level of evidence: Not ratable.

Nonbiological Microsurgery Simulators in Plastic Surgery Training: A Systematic Review

BACKGROUND

Simulation has gained notable recognition for its role as an effective training and assessment modality in the present era of competency-based medical education. Despite the well-documented efficacy of both live and cadaveric animal models, several ethical, financial, and accessibility issues persist with their use. Lower fidelity nonbiological simulators have gained recognition for their ability to circumvent these challenges. This systematic review reports on all prosthetic and virtual reality simulators in use for microsurgery training, with an emphasis on each model's complexity, characteristics, advantages, disadvantages, and validation measures taken.

METHODS

A systematic search was performed using the National Library of Medicine (PubMed), MEDLINE, and Embase databases. Search terms were those pertaining to prosthetic and virtual reality models with relevance to microsurgical training in plastic surgery. Three independent reviewers evaluated all articles retrieved based on strict inclusion and exclusion criteria.

RESULTS

Fifty-seven articles met the inclusion criteria for review, reporting on 20 basic prosthetic models, 20 intermediate models, 13 advanced models, and six virtual reality simulators.

CONCLUSIONS

A comprehensive summary has been compiled of all nonbiological simulators in use for microsurgery training in plastic surgery, demonstrating efficacy for the acquisition and retention of microsurgical skills. Metrics-based validation efforts, however, were often lacking in the literature. As plastic surgery programs continue to innovate, ensure accountability, and safely meet today's training standards, prosthetic simulators are set to play a larger role in the development of a standardized, ethical, accessible, and objectively measurable microsurgery training curriculum for the modern-day plastic and reconstructive surgery resident.

Comparison of Conventional Microscopic and Exoscopic Experimental Bypass Anastomosis: A Technical Analysis

BACKGROUND

Recently, the use of digital exoscopes has been increasingly promoted as an alternative to microscopes. The aim of this study is to compare experimental bypass quality in both visualization methods.

METHODS

This study used two hundred 1-mm chicken wing vessels, which were used for either exoscopic or microscopic (100 samples each) bypass procedures. All procedures were recorded between July 2018 and September 2018. The bypass quality was evaluated according to our published practical scale (time, stitch distribution, intima-intima attachment, and orifice size).

RESULTS

Both methods are effective in doing bypass suturing (practical scale score was good, 86% vs. 85%; P = 0.84). There were no significant differences regarding intima-intima attachment (P = 0.26) and orifice size (P = 0.25). However, suturing time (P < 0.001) was less using the microscope, whereas stitch distribution (P = 0.001) was better using the exoscope. Different suturing techniques (interrupted vs. continuous) had overall comparable results (P = 0.55).

CONCLUSIONS

Both methods produced equally satisfactory results in experimental bypass procedures. The exoscope has the potential for better 3-dimensional visualization and sharing the surgeon's view with others for teaching purposes.

Side-to-Side Anastomosis Training Model Using Rat Common Carotid Arteries

BACKGROUND

The side-to-side anastomosis is one of the difficult bypass configurations that may be used in various complex cerebral vascular and neoplastic cases. Few pure arterial models exist for practicing this bypass subtype.

OBJECTIVE

To provide an optimized side-to-side anastomosis training model using rat common carotid arteries (CCA).

METHODS

Bilateral CCAs were exposed in the neck of 10 anesthetized Sprague-Dawley rats. The arteries were juxtaposed in parallel, using temporary aneurysm clips applied proximally and distally. CCA caliber and the length of CCA juxtaposition were measured. Side-to-side anastomosis was completed and ischemia time was recorded. Unintended complications were recorded for further analysis.

RESULTS

Anastomosis was completed successfully in all animals. The CCAs were approximated in all animals without any difficulty or undue tension. In 2 rats, death occurred prior to completion of anastomosis, which was attributed to injury to the external jugular vein during vessel exposure. Mean ischemia time was 35 min with an average of 22 sutures done to complete the anastomosis. The average CCA caliber was 1.1 ± 0.2 mm and the arteries could be juxtaposed for an average length of 10.2 ± 1.5 mm.

CONCLUSION

Full exposure of the cervical segment of the CCAs enables tension-free approximation of adequate length of the vessel for a side-to-side anastomosis. Avoiding complications during exposure helps in prevention of animal death during the ischemia period.

National trends in cerebral bypass surgery in the United States, 2002–2014

OBJECTIVE

Cerebral bypass procedures are microsurgical techniques to augment or restore cerebral blood flow when treating a number of brain vascular diseases including moyamoya disease, occlusive vascular disease, and cerebral aneurysms. With advances in endovascular therapy and evolving evidence-based guidelines, it has been suggested that cerebral bypass procedures are in a state of decline. Here, the authors characterize the national trends in cerebral bypass surgery in the United States from 2002 to 2014.

METHODS

Using the National (Nationwide) Inpatient Sample, the authors extracted for analysis the data on all adult patients who had undergone cerebral bypass as indicated by ICD-9-CM procedure code 34.28. Indications for bypass procedures, patient demographics, healthcare costs, and regional variations are described. Results were stratified by indication for cerebral bypass including moyamoya disease, occlusive vascular disease, and cerebral aneurysms. Predictors of inpatient complications and death were evaluated using multivariable logistic regression analysis.

RESULTS

From 2002 to 2014, there was an increase in the annual number of cerebral bypass surgeries performed in the United States. This increase reflected a growth in the number of cerebral bypass procedures performed for adult moyamoya disease, whereas cases performed for occlusive vascular disease or cerebral aneurysms declined. Inpatient complication rates for cerebral bypass performed for moyamoya disease, vascular occlusive disease, and cerebral aneurysm were 13.2%, 25.1%, and 56.3%, respectively. Rates of iatrogenic stroke ranged from 3.8% to 20.4%, and mortality rates were 0.3%, 1.4%, and 7.8% for moyamoya disease, occlusive vascular disease, and cerebral aneurysms, respectively. Multivariate logistic regression confirmed that cerebral bypass for vascular occlusive disease or cerebral aneurysm is a statistically significant predictor of inpatient complications and death. Mean healthcare costs of cerebral bypass remained unchanged from 2002 to 20014 and varied with treatment indication: moyamoya disease $38,406 ± $483, vascular occlusive disease $46,618 ± $774, and aneurysm $111,753 ± $2381.

CONCLUSIONS

The number of cerebral bypass surgeries performed for adult revascularization has increased in the United States from 2002 to 2014. Rising rates of surgical bypass reflect a greater proportion of surgeries performed for moyamoya disease, whereas bypasses performed for vascular occlusive disease and aneurysms are decreasing. Despite evolving indications, cerebral bypass remains an important surgical tool in the modern endovascular era and may be increasing in use. Stagnant complication rates highlight the need for continued interest in advancing available bypass techniques or technologies to improve patient outcomes.

A Practical Cadaveric Model for Intracranial Bypass Training

BACKGROUND

Intracranial bypass is technically challenging and difficult to learn owing to its relative rarity and complexity. Although multiple training models for intracranial bypass exist, a detailed depiction of the use and fidelity of cadaveric specimens for bypass training is lacking in the literature. This study describes use of preserved cadaveric specimens as a practical training model for performance of multiple intracranial bypasses and discusses the surgical setup for a cadaveric bypass laboratory.

METHODS

Using a cadaveric specimen and basic microneurosurgical instruments and supplies, 5 intracranial bypasses were performed (superficial temporal artery [STA]-to-middle cerebral artery [MCA], MCA-to-MCA, STA-to-posterior cerebral artery [PCA], anterior cerebral artery-to-anterior cerebral artery, and posterior inferior cerebellar artery-to-posterior inferior cerebellar artery) using pterional, subtemporal, interhemispheric, and suboccipital approach. Bypass integrity was assessed by direct fluid injection into the adjacent vessel segment. All procedures were recorded.

RESULTS

Procedural steps mirrored actual bypass surgery and included vessel marking, performance of arteriotomy, and completion of an end-to-end, end-to-side, or side-to-side anastomosis. Simulations included anatomically appropriate exposures of common intracranial (MCA, PCA, posterior inferior cerebellar artery, anterior cerebral artery) and extracranial (STA) vessels encountered during cerebral bypass surgery and high-fidelity recreations of the operative corridors associated with deeper anastomoses, such as STA-to-PCA bypass. Vessel diameters were 1.5-2.1 mm, and anastomosis times were 20-40 minutes. Immediate feedback on anastomotic integrity was achieved via direct fluid injection adjacent to the anastomosis site.

CONCLUSIONS

The cadaveric specimen trainee model is a relatively simple yet high-fidelity approach for learning intracranial bypass.

The Identification of Factors That Influence the Quality of Bypass Anastomosis and an Evaluation of the Usefulness of an Experimental Practical Scale in This Regard

BACKGROUND

Several factors associated with interrupted and continuous suturing techniques affect the quality of bypass anastomosis. It is difficult to determine the impact of these factors during surgery. The primary objective of this study was to evaluate factors with the potential to influence the quality of bypass anastomosis using either interrupted or continuous suturing. A secondary objective was to evaluate the usefulness of a practical scale when comparing interrupted and continuous suturing techniques to improve bypass anastomosis.

METHODS

Interrupted (n = 100) and continuous (n = 100) suturing techniques were used in 200 end-to-side bypasses to a depth of 3 cm and were assessed by 5 neurosurgeons.

RESULTS

Vessel closing time (P < 0.001), stitch distribution (P < 0.001), intima-intima attachment (P < 0.001), and size of the orifice (P < 0.001) had a significant impact on the quality of the bypass regardless of the suturing technique used. The suturing technique used (interrupted or continuous) and positioning of the recipient vessel (vertical or horizontal) did not significantly influence the quality of anastomosis. Using multivariate analysis, the highest statistical significance with regard to bypass quality was attributed to the large size of the orifice and intimal attachment.

CONCLUSIONS

There were advantages and disadvantages to both suturing techniques. The scale was a practical way to measure and improve performance.

Microvascular anastomosis under 3D exoscope or endoscope magnification: A proof-of-concept study

Background:

Extracranial–intracranial bypass is a challenging procedure that requires special microsurgical skills and an operative microscope. The exoscope is a tool for neurosurgical visualization that provides view on a heads-up display similar to an endoscope, but positioned external to the operating field, like a microscope. The authors carried out a proof-of-concept study evaluating the feasibility and effectiveness of performing microvascular bypass using various new exoscopic tools.

Methods:

We evaluated microsurgical procedures using a three-dimensional (3D) endoscope, hands-free robotic automated positioning two-dimensional (2D) exoscope, and an ocular-free 3D exoscope, including surgical gauze knot tying, surgical glove cutting, placental vessel anastomoses, and rat vessel anastomoses. Image quality, effectiveness, and feasibility of each technique were compared among different visualization tools and to a standard operative microscope.

Results:

3D endoscopy produced relatively unsatisfactory resolution imaging. It was shown to be sufficient for knot tying and anastomosis of a placental artery, but was not suitable for anastomosis in rats. The 2D exoscope provided higher resolution imaging, but was not adequate for all maneuvers because of lack of depth perception. The 3D exoscope was shown to be functional to complete all maneuvers because of its depth perception and higher resolution.

Conclusion:

Depth perception and high resolution at highest magnification are required for microvascular bypass procedures. Execution of standard microanastomosis techniques was unsuccessful using 2D imaging modalities because of depth-perception-related constraints. Microvascular anastomosis is feasible under 3D exoscopic visualization; however, at highest magnification, the depth perception is inferior to that provided by a standard operative microscope, which impedes the procedure.

Microvascular Anastomosis: Proposition of a Learning Curve

BACKGROUND

Learning to perform a microvascular anastomosis is one of the most difficult tasks in cerebrovascular surgery. Previous studies offer little regarding the optimal protocols to maximize learning efficiency. This failure stems mainly from lack of knowledge about the learning curve of this task.

OBJECTIVE

To delineate this learning curve and provide information about its various features including acquisition, improvement, consistency, stability, and recall.

METHODS

Five neurosurgeons with an average surgical experience history of 5 yr and without any experience in bypass surgery performed microscopic anastomosis on progressively smaller-caliber silastic tubes (Biomet, Palm Beach Gardens, Florida) during 24 consecutive sessions. After a 1-, 2-, and 8-wk retention interval, they performed recall test on 0.7-mm silastic tubes. The anastomoses were rated based on anastomosis patency and presence of any leaks.

RESULTS

Improvement rate was faster during initial sessions compared to the final practice sessions. Performance decline was observed in the first session of working on a smaller-caliber tube. However, this rapidly improved during the following sessions of practice. Temporary plateaus were seen in certain segments of the curve. The retention interval between the acquisition and recall phase did not cause a regression to the prepractice performance level.

CONCLUSION

Learning the fine motor task of microvascular anastomosis adapts to the basic rules of learning such as the “power law of practice.” Our results also support the improvement of performance during consecutive sessions of practice. The objective evidence provided may help in developing optimized learning protocols for microvascular anastomosis.