Low-Fidelity Simulator for the Standardized Training of Fetoscopic Meningomyelocele Repair

High-fidelity, low-cost synthetic training model for fetoscopic spina bifida repair

BACKGROUND

Fetoscopic spina bifida repair is increasingly being practiced, but limited skill acquisition poses a barrier to widespread adoption. Extensive training in relevant models, including both ex vivo and in vivo models may help. To address this, a synthetic training model that is affordable, realistic, and that allows skill analysis would be useful.

OBJECTIVE

This study aimed to create a high-fidelity model for training in the essential neurosurgical steps of fetoscopic spina bifida repair using synthetic materials. In addition, we aimed to obtain a cheap and easily reproducible model.

STUDY DESIGN

We developed a 3-layered, silicon-based model that resemble the anatomic layers of a typical myelomeningocele lesion. It allows for filling of the cyst with fluid and conducting a water tightness test after repair. A compliant silicon ball mimics the uterine cavity and is fixed to a solid 3-dimensional printed base. The fetal back with the lesion (single-use) is placed inside the uterine ball, which is reusable and repairable to allow for practicing port insertion and fixation multiple times. Following cannula insertion, the uterus is insufflated and a clinical fetoscopic or robotic or prototype instruments can be used. Three skilled endoscopic surgeons each did 6 simulated fetoscopic repairs using the surgical steps of an open repair. The primary outcome was surgical success, which was determined by water tightness of the repair, operation time <180 minutes and an Objective Structured Assessment of Technical Skills score of ≥18 of 25. Skill retention was measured using a competence cumulative sum analysis of a composite binary outcome of surgical success. Secondary outcomes were cost and fabrication time of the model.

RESULTS

We made a model that can be used to simulate the neurosurgical steps of spina bifida repair, including anatomic details, port insertion, placode release and descent, undermining of skin and muscular layer, and endoscopic suturing. The model was made using reusable 3-dimensional printed molds and easily accessible materials. The 1-time startup cost was €211, and each single-use, simulated myelomeningocele lesion cost €9.5 in materials and 50 minutes of working time. Two skilled endoscopic surgeons performed 6 simulated, 3-port fetoscopic repairs, whereas a third used a Da Vinci surgical robot. Operation times decreased by more than 30% from the first to the last trial. Six experiments per surgeon did not show an obvious Objective Structured Assessment of Technical Skills score improvement. Competence cumulative sum analysis confirmed competency for each surgeon.

CONCLUSION

This high-fidelity, low-cost spina bifida model allows simulated dissection and closure of a myelomeningocele lesion. VIDEO ABSTRACT.

Training model for the fetal myelomeningocele correction with multiportal endoscopic technique

PURPOSE

The recent history of myelomeningocele has shown that treatment during the fetal life may reduce the risk of developing hydrocephalus in individuals by approximately 50%. Thus, a significant advancement involves fetal surgery performed through an endoscopic technique in which portals are placed to introduce the forceps and laparoscopic instruments. However, the development of this technique requires training; therefore, this study aimed to develop a training model for fetal myelomeningocele repair technique with multi-portal endoscopy.

METHODS

Two stages of endoscopic technique development were performed. The first stage consisted of exercises in order to familiarize the surgeon with 2D-vision endoscopic surgery, associated with the application of exercises focused on surgical skills, such as the development of laparoscopic knots in a synthetic model. The second stage involved the creation and application of the stages of myelomeningocele closure with a non-living animal model consisting of a chicken breast to simulate the myelomeningocele and a basketball to simulate the gravid uterus, in which perforations were made to introduce vascular introducers (portals) that, as in vivo, are used as portals (trocars) for the introduction of laparoscopic instruments. Overall, two different scenarios with three portals and two portals were tested.

RESULTS

In three-portal simulator, the triangular apex trocar was used for the introduction of 4-mm 0° or 30° optics or even Minop type neurodoscope (Aesculap®, Germany) that was operated by the assistant surgeon; the other two portals are used for the introduction of laparoscopic instruments. Thus, the surgeon is able to perform maneuvers bimanually since dissection to laparoscopic sutures. In two-portal simulator, the surgeon and assistant stay side by side and one of the portals is used for the optic and the other for the laparoscopic instruments. There is no possibility of bimanual dissection in this method.

CONCLUSION

Realistic simulation models for endoscopic fetal surgery for myelomeningocele correction are easily performed and help develop the necessary skills for fetal surgery teams.

Development of a simulator for training of fetoscopic myelomeningocele surgery

OBJECTIVE

To develop a realistic simulation model for laparotomy-assisted fetoscopic spina bifida aperta (SBa) surgery, to be used for training purposes and preoperative planning.

METHODS

The predefined general requirement was a realistic model of an exteriorized uterus, allowing all neurosurgical steps of the intervention. The uterus was modelled using ultrasound and MRI images of a 25 weeks' gravid uterus, consisting of flexible polyurethane foam coated with pigmented silicone. The fetal model, contained an opening on the dorsal side for a customizable spinal insert with all the aspects of a SBa, including a cele, placode, and myofascial and skin layer. The model was assessed in a series of validation experiments.

RESULTS

Production costs are low, uterus and fetus are reusable. Placental localization and the level and size of the spinal defect are adjustable, enabling case-specific adaptations. All aspects of the simulator were scored close to realistic or higher for both appearance and functional capacities.

CONCLUSIONS

This innovative model provides an excellent training opportunity for centers that are starting a fetoscopic SBa repair program. It is the first simulation model with adjustable spinal defect and placental localisation. Further objective validation is required, but the potential for using this model in preoperative planning is promising.

A comparison of MRI appearance and surgical detethering rates between intrauterine and postnatal myelomeningocele closures: a single-center pilot matched cohort study

INTRODUCTION

Intrauterine myelomeningocele repair (IUMR) and postnatal myelomeningocele repair (PNMR) differ in terms of both setting and surgical technique. A simplified technique in IUMR, in which a dural onlay is used followed by skin closure, has been adopted at our institution. The goal of this study was to compare the rates of clinical tethering in IUMR and PNMR patients, as well as to evaluate the appearance on MRI.

METHODS

We conducted a retrospective review of 36 patients with MMC repaired at our institution, with 2:1 PNMR to IUMR matching based on lesion level. A pediatric neuroradiologist blinded to the clinical details reviewed the patients' lumbar spine MRIs for the distance from neural tissue to skin and the presence or absence of a syrinx. An EMR review was then done to evaluate for detethering procedures and need for CSF diversion.

RESULTS

Mean age at MRI was 4.0 years and mean age at last follow-up was 6.1 years, with no significant difference between the PNMR and IUMR groups. There was no significant difference between groups in the distance from neural tissue to skin (PNMR 13.5 mm vs IUMR 17.6 mm; p = 0.5). There was no difference in need for detethering operations between groups (PNMR 12.5% vs IUMR 16.7%; RR 0.75; CI 0.1-5.1).

CONCLUSIONS

There was no significant difference between postnatal- and intrauterine-repaired myelomeningocele on MRI or in need for detethering operations. These results imply that a more straightforward and time-efficient IUMR closure technique does not lead to an increased rate of tethering when compared to the multilayered PNMR.

Minimally Invasive Fetal Surgery and the Next Frontier

Most patients with congenital anomalies do not require prenatal intervention. Furthermore, many congenital anomalies requiring surgical intervention are treated adequately after birth. However, there is a subset of patients with congenital anomalies who will die before birth, shortly after birth, or experience severe postnatal complications without fetal surgery. Fetal surgery is unique in that an operation is performed on the fetus as well as the pregnant woman who does not receive any direct benefit from the surgery but rather lends herself to risks, such as hemorrhage, abruption, and preterm labor. The maternal risks involved with fetal surgery have limited the extent to which fetal interventions may be performed but have, in turn, led to technical innovations that have significantly advanced the field. This review will examine congenital abnormalities that can be treated with minimally invasive fetal surgery and introduce the next frontier of prenatal management of fetal surgical pathology.

Care Levels for Fetal Therapy Centers

Fetal therapies undertaken to improve fetal outcome or to optimize transition to neonate life often entail some level of maternal, fetal, or neonatal risk. A fetal therapy center needs access to resources to carry out such therapies and to manage maternal, fetal, and neonatal complications that might arise, either related to the therapy per se or as part of the underlying fetal or maternal condition. Accordingly, a fetal therapy center requires a dedicated operational infrastructure and necessary resources to allow for appropriate oversight and monitoring of clinical performance and to facilitate multidisciplinary collaboration between the relevant specialties. Three care levels for fetal therapy centers are proposed to match the anticipated care complexity, with appropriate resources to achieve an optimal outcome at an institutional and regional level. A level I fetal therapy center should be capable of offering fetal interventions that may be associated with obstetric risks of preterm birth or membrane rupture but that would be very unlikely to require maternal medical subspecialty or intensive care, with neonatal risks not exceeding those of moderate prematurity. A level II center should have the incremental capacity to provide maternal intensive care and to manage extreme neonatal prematurity. A level III therapy center should offer the full range of fetal interventions (including open fetal surgery) and be able manage any of the associated maternal complications and comorbidities, as well as have access to neonatal and pediatric surgical intervention including indicated surgery for neonates with congenital anomalies.

Complex gastroschisis: a new indication for fetal surgery?

Gastroschisis (GS) is a congenital abdominal wall defect, in which the bowel eviscerates from the abdominal cavity. It is a non-lethal isolated anomaly and its pathogenesis is hypothesized to occur as a result of two hits: primary rupture of the 'physiological' umbilical hernia (congenital anomaly) followed by progressive damage of the eviscerated bowel (secondary injury). The second hit is thought to be caused by a combination of mesenteric ischemia from constriction in the abdominal wall defect and prolonged amniotic fluid exposure with resultant inflammatory damage, which eventually leads to bowel dysfunction and complications. GS can be classified as either simple or complex, with the latter being complicated by a combination of intestinal atresia, stenosis, perforation, volvulus and/or necrosis. Complex GS requires multiple neonatal surgeries and is associated with significantly greater postnatal morbidity and mortality than is simple GS. The intrauterine reduction of the eviscerated bowel before irreversible damage occurs and subsequent defect closure may diminish or potentially prevent the bowel damage and other fetal and neonatal complications associated with this condition. Serial prenatal amnioexchange has been studied in cases with GS as a potential intervention but never adopted because of its unproven benefit in terms of survival and bowel and lung function. We believe that recent advances in prenatal diagnosis and fetoscopic surgery justify reconsideration of the antenatal management of complex GS under the rubric of the criteria for fetal surgery established by the International Fetal Medicine and Surgery Society (IFMSS). Herein, we discuss how conditions for fetoscopic repair of complex GS might be favorable according to the IFMSS criteria, including an established natural history, an accurate prenatal diagnosis, absence of fully effective perinatal treatment due to prolonged need for neonatal intensive care, experimental evidence for fetoscopic repair and maternal and fetal safety of fetoscopy in expert fetal centers. Finally, we propose a research agenda that will help overcome barriers to progress and provide a pathway toward clinical implementation. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Implementation Process and Evolution of a Laparotomy-Assisted 2-Port Fetoscopic Spina Bifida Closure Program

INTRODUCTION

Prenatal closure of open spina bifida via open fetal surgery improves neurologic outcomes for infants in selected pregnancies. Fetoscopic techniques that are minimally invasive to the uterus aim to provide equivalent fetal benefits while minimizing maternal morbidities, but the optimal technique is undetermined. We describe the development, evolution, and feasibility of the laparotomy-assisted 2-port fetoscopic technique for prenatal closure of fetal spina bifida in a newly established program.

METHODS

We conducted a retrospective cohort study of women consented for laparotomy-assisted fetoscopic closure of isolated fetal spina bifida. Inclusion and exclusion criteria followed the Management of Myelomeningocele Study (MOMS). Team preparation involved observation at the originating center, protocol development, ancillary staff training, and surgical rehearsal using patient-matched models through simulation prior to program implementation. The primary outcome was the ability to complete the repair fetoscopically. Secondary maternal and fetal outcomes to assess performance of the technique were collected prospectively.

RESULTS

Of 57 women screened, 19 (33%) consented for laparotomy-assisted 2-port fetoscopy between February 2017 and December 2019. Fetoscopic closure was completed in 84% (16/19) cases. Over time, the technique was modified from a single- to a multilayer closure. In utero hindbrain herniation improved in 86% (12/14) of undelivered patients at 6 weeks postoperatively. Spontaneous rupture of membranes occurred in 31% (5/16) of fetoscopic cases. For completed cases, median gestational age at birth was 37 (range 27-39.6) weeks and 50% (8/16) of women delivered at term. Vaginal birth was achieved in 56% (9/16) of patients. One newborn had a cerebrospinal fluid leak that required postnatal surgical repair.

CONCLUSION

Implementation of a laparotomy-assisted 2-port fetoscopic spina bifida closure program through rigorous preparation and multispecialty team training may accelerate the learning curve and demonstrates favorable obstetric and perinatal outcomes.

Comparison of two- and three-dimensional endoscopic visualization for fetal myelomeningocele repair: a pilot study using a fetoscopic surgical simulator

INTRODUCTION

The objective of this study was to evaluate the utility of three-dimensional (3D) versus conventional two-dimensional (2D) endoscopy for fetal myelomeningocele repair using a low-fidelity fetoscopic surgical simulator.

METHODS

A low-fidelity fetoscopic box trainer was developed for surgical simulation of myelomeningocele repair. Participants with varying surgical experience were recruited and completed three essential tasks (cutting skin, dural patch placement, and suturing skin) using both 2D and 3D endoscopic visualization. Participants were randomized to begin all tasks in either 2D or 3D. Time to completion was measured for each task, and each participant subsequently completed the NASA Load Index test and a questionnaire evaluating their experience.

RESULTS

Sixteen participants completed the study tasks using both 2D and 3D endoscopes in the simulator. While the mean performance time across all tasks was shorter with 3D versus 2D endoscopy (cutting skin, 47 vs. 54 seconds; dural patch placement, 38 vs. 52 seconds; and suturing skin, 424 vs. 499 seconds), the results did not reach statistical significance. When comparing times to completion of each of the three tasks between levels of expertise, participants in the expert category were faster when suturing skin on the 2D modality (P = 0.047). Under 3D visualization, experts were faster at cutting the skin (P = 0.008). When comparing experiences using the NASA-TLX test, participants felt that their performance was better using 3D over the 2D system (P = 0.045). Overall, 13 of 16 (81.3%) participants preferred 3D over 2D visualization.

CONCLUSIONS

Three-dimensional endoscopes could potentially be used in the near future for relative improvement in visualization and possibly performance during complex fetoscopic procedures such as prenatal repair of myelomeningocele defects. Further studies utilizing 3D scopes for other related procedures may potentially support clinical implementation of this technology in fetal surgery and also prove to be a useful tool in surgical training.

Validation of a high-fidelity training model for fetoscopic spina bifida surgery

Open fetal surgery for spina bifida (SB) is safe and effective yet invasive. The growing interest in fetoscopic SB repair (fSB-repair) prompts the need for appropriate training. We aimed to develop and validate a high-fidelity training model for fSB-repair. fSB-repair was simulated in the abdominal cavity and on the stomach of adult rabbits. Laparoscopic fetal surgeons served either as novices (n = 2) or experts (n = 3) based on their experience. Technical performance was evaluated using competency Cumulative Sum (CUSUM) analysis and the group splitting method. Main outcome measure for CUSUM competency was a composite binary outcome for surgical success, i.e. watertight repair, operation time ≤ 180 min and Objective-Structured-Assessment-of-Technical-Skills (OSATS) score ≥ 18/25. Construct validity was first confirmed since competency levels of novices and experts during their six first cases using both methods were significantly different. Criterion validity was also established as 33 consecutive procedures were needed for novices to reach competency using learning curve CUSUM, which is a number comparable to that of clinical fSB-repair. Finally, we surveyed expert fetal surgeons worldwide to assess face and content validity. Respondents (26/49; 53%) confirmed it with ≥ 71% of scores for overall realism ≥ 4/7 and usefulness ≥ 3/5. We propose to use our high-fidelity model to determine and shorten the learning curve of laparoscopic fetal surgeons and retain operative skills.

Fetoscopic techniques for prenatal covering of gastroschisis in an ovine model are technically demanding and do not lead to permanent anchoring on the fetus until the end of gestation

INTRODUCTION

This is the cumulative technical report on the operative procedures and limitations of fetoscopic bag insertion, intestinal bag placement, and bag fixation to the fetus in a series of pilot studies in an ovine model for prenatal treatment of gastroschisis.

MATERIAL AND METHODS

In 24 German blackhead sheep, a surgically created gastroschisis was managed by fetoscopic placement of the extruded intestines into a bag. The bag was then fastened onto the fetal abdominal wall. Different materials (sterile gloves, latex condoms, laparosopic retrieval bags) and different fixation techniques (laparoscopic staplers, interrupted and continuous sutures) have been examined. The fetuses were retrieved and evaluated at the end of gestation.

RESULTS

Uterine bag insertion was successful in 15 of 24 (62.5%) and intestinal bag placement in 10 of 15 available fetuses (66.6%). The main factor limiting fetoscopic procedures was chorioamniotic separation (CAS). Sterilized condoms provided the most appropriate type of bags and the V-Loc™ running suture, the most expedient type of fixation, which was achieved in 9 of the 10 fetuses (complete = 2, partially = 7) by using a three port access (5 mm and 2 × 3 mm). All bags were encountered completely or partially dislocated from the fetus at the end of gestation.

CONCLUSIONS

Fetoscopic intestinal bag placement and fixation in gastroschisis technically demanding. None of the evaluated techniques led to permanent anchorage of the bag to the fetus. The development of specially designed instruments, bags and fixation methods is required to optimize this approach.

Fetal Surgery

Fetal surgery is an established but still rapidly evolving specialty, born from the rationale that destructive embryologic processes, recognized early in gestation, can be curtailed by prenatal correction. As more and more centers begin offering fetal interventions, quality of care must be verified through transparency about clinical capabilities and resources. Level designations should be assigned based on capability, as in trauma and neonatal ICU centers for excellence, and volume requirements must be set for fetal surgery certification. Regionalization of this specialty care may be required to optimize outcomes.

Fetoscopic spina bifida repair

INTRODUCTION

Spina bifida is the most common non-lethal congenital birth defect of the central nervous system that causes chronic disability due to the combined effects of local nerve damage and the sequelae of non-communicating hydrocephalus. This abnormality can be identified early in gestation and the damage can be progressive over the course of pregnancy. Advances in fetal treatment have made minimally invasive prenatal surgery a realistic consideration for spina bifida in order to improve the outcome for children affected this condition.

EVIDENCE ACQUISITION

Prenatal surgery for spina bifida via open fetal surgery with hysterotomy decreases the rate of ventriculoperitoneal shunt placement and improves motor function compared to standard postnatal surgery. Maternal risks of open fetal surgery are primarily related to complications of the hysterotomy including thinning or rupture that begins in the index pregnancy but persists for every future pregnancy. Minimizing maternal risks is the largest impetus to explore and optimize a minimally invasive fetoscopic alternative. Techniques vary from using a complete percutaneous approach to open fetoscopy, which requires laparotomy but is minimally invasive to the uterus. This allows vaginal delivery at term and no scar complications are reported thus far. Fetal short-term neurosurgical outcomes compare favorably with improvement in hindbrain herniation >70% and decreased need for treatment for hydrocephalus between 40-45% after prenatal surgery performed either fetoscopically or through open fetal surgery.

EVIDENCE SYNTHESIS

Maternal obstetric outcomes are superior for fetoscopic spina bifida repair compared to open fetal surgery and avoids the ongoing risk in future pregnancy. Neonatal and infant benefits appear equivalent. The open fetoscopic approach minimizes the risk of ruptured membranes and subsequent preterm delivery as opposed to a completely percutaneous procedure. International collaboration is ongoing to share experience and assess long term treatment effects.

CONCLUSIONS

Continued refinement of a minimally invasive strategy for prenatal treatment of spina bifida is necessary to maximize benefits to the child and further minimize maternal risks and preterm birth.

A mixed-reality surgical trainer with comprehensive sensing for fetal laser minimally invasive surgery

PURPOSE

Smaller incisions and reduced surgical trauma made minimally invasive surgery (MIS) grow in popularity even though long training is required to master the instrument manipulation constraints. While numerous training systems have been developed in the past, very few of them tackled fetal surgery and more specifically the treatment of twin-twin transfusion syndrome (TTTS). To address this lack of training resources, this paper presents a novel mixed-reality surgical trainer equipped with comprehensive sensing for TTTS procedures. The proposed trainer combines the benefits of box trainer technology and virtual reality systems. Face and content validation studies are presented and a use-case highlights the benefits of having embedded sensors.

METHODS

Face and content validity of the developed setup was assessed by asking surgeons from the field of fetal MIS to accomplish specific tasks on the trainer. A small use-case investigates whether the trainer sensors are able to distinguish between an easy and difficult scenario.

RESULTS

The trainer was deemed sufficiently realistic and its proposed tasks relevant for practicing the required motor skills. The use-case demonstrated that the motion and force sensing capabilities of the trainer were able to analyze surgical skill.

CONCLUSION

The developed trainer for fetal laser surgery was validated by surgeons from a specialized center in fetal medicine. Further similar investigations in other centers are of interest, as well as quality improvements which will allow to increase the difficulty of the trainer. The comprehensive sensing appeared to be capable of objectively assessing skill.

Early postnatal bladder function in fetoscopic myelomeningocele repair patients

PURPOSE

Prenatal repair of myelomeningocele (MMC) via hysterotomy has demonstrated neurosurgical and motor benefits, when compared to postnatal repairs. Urologic benefits, however, remain to be seen. The purpose of this study was to review early postnatal bladder function in patients undergoing a novel endoscopic approach for MMC repair using an exteriorized uterus.

METHODS

A prospective urologic assessment of patients undergoing fetoscopic MMC repair and receiving subsequent care at our facility, was performed. Patients were managed and urodynamic studies risk-stratified according to the Centers for Disease Control and Prevention Urologic and Renal Protocol for the Newborn and Young Child with Spina Bifida.

RESULTS

Fetoscopic MMC repair was performed in 14 patients. No patients had hydronephrosis or bladder thickening at birth. Detrusor overactivity was observed in nine (64.3%) patients. Impaired compliance was seen in eight (57.1%) patients. No patients had a detrusor leak point pressure of > 40 cm H2O or evidence of detrusor sphincter dyssynergia. Three (21.4%) patients had vesicoureteral reflux, seven (50.0%) had an open bladder neck, and none had trabeculated bladders.

CONCLUSION

In this early experience with fetoscopic MMC repair, postnatal bladder function does not appear to be any worse than that of previously reported prenatal or postnatal closures.