Advancing Fetoscopic Repair of Complex Gastroschisis

Abstract

Gastroschisis, a congenital abdominal wall defect located to the right of the intact umbilical cord (UC), results in the herniation of fetal abdominal organs into the amniotic cavity without a protective membrane covering these structures. Complex gastroschisis (CG), comprising approximately 10% of cases, is associated with significantly higher morbidity and mortality rates compared to simple gastroschisis. Fetoscopic repair of CG offers the potential to improve gastrointestinal health at birth, but thus far, no procedure has been successfully demonstrated as safe and feasible. Therefore, the goal of this graduation project was to provide a proof of principle for a novel dedicated method that enables the swift closure of the abdominal wall defect during a fetoscopic repair procedure for CG.

The development of this method began with an analysis of the clinical context, including the characteristics of the abdominal wall defect, the adjacent umbilical cord and vessels, and the fetoscopic surgical setup, which provided a clear design direction. After generating various concept solutions, the key concept — a silicone ring with membrane — was selected using the Harris Profile methodology. This concept was designed for insertion into the fetal abdominal cavity, with the membrane effectively covering the opening of the defect.

Eight configurations of the silicone ring with a membrane were then prototyped through injection molding of liquid silicone rubber in a 3D-printed mold. The rings varied in shape (round or rusk), diam- eter (20 mm and 30 mm), and stiffness (shore hardness A25 and A40). Additionally, a validation model simulating a 24-week-old fetus with CG was developed with input from medical experts.

The validation experiments demonstrated that the silicone ring with a membrane securely remained in place, effectively closing the abdominal wall defect under intra-abdominal pressure conditions ranging from 0 to 40 mmHg. These experiments, conducted using the validation model, simulated conditions during and immediately after fetal intervention in a 24-week-old fetus with CG following intestinal repositioning. These experiments provided proof of principle for the silicone ring with membrane as a novel method that enables the swift closure of the abdominal wall defect in CG during a fetoscopic repair procedure. Notably, round-shaped rings were favored, and larger diameters allowed for coverage of larger defects. However, it’s noteworthy that the 20 mm round ring effectively covered an oval-shaped defect measuring 13.5 × 12.7 mm, aligning with the reported mean defect size in CG. Furthermore, the experiments demonstrated the feasibility of introducing the rings through a 12 Fr (20 mm rings) or 14 Fr (30 mm rings) surgical port, aligning with the preferred surgical setup.

Future research is required to clinically investigate the defect diameter in CG and optimize the silicone ring with membrane’s design. Additionally, enhancing the validation model to serve dual purposes as both a validation and training model will facilitate user tests. Moreover, developing an instrument for introducing the ring into the uterus and refining the surgical technique for precise ring positioning will be essential steps toward the clinical application of this innovative approach.