Suture Characteristics after Exposure to Amniotic Fluid from an in vitro Model of Fetal Surgery

Abstract

Introduction Suture tensile properties have only been tested in extrauterine environments. Amniotic fluid (AF) is a complex milieu of enzymes and inflammatory factors. This study tested the mechanical properties of sutures with a variety of inherent properties, after exposure to AF from patients with conditions prompting fetal intervention. Methods AF was obtained from three patients with twin-twin transfusion syndrome (TTTS), and three patients with neural tube defects (NTD). Six types of 2-0 sutures were placed on 1.2 N of tension to mimic placement in vivo, and incubated in AF at 37° C (98.6° F). These included ethylene terephthalate (Ethibond), glycomer 631 (V-Loc), poliglecaprone 25 (Monocryl), poly-4-hydroxybutyrate (Monomax), polydioxanone (PDS), and polyglactin 910 (Vicryl). Failure load, stress, strain, and initial modulus were tested after 24 hours of incubation and after 4 weeks, and compared with control (unincubated) sutures using t tests, Kruskal-Wallis tests, and stress-strain curves. Results Poliglecaprone 25 and polyglactin 910 dissolve more quickly in AF compared to outside the uterus, disintegrating at 4 weeks. Ethylene terephthalate and polydioxanone experienced little change across 4 weeks of incubation. Glycomer 631 and poly-4-hydroxybutyrate exhibited interesting behavior in AF: glycomer 631 became more deformable at 24 hours but later regained toughness by 4 weeks, while poly-4-hydroxybutyrate became tougher and in some cases stronger with time in AF. As a class, braided sutures act more like rigid materials, and monofilaments act like deformable plastics. Conclusion These findings along with other suture characteristics such as ease of handling and availability may inform fetal intervention teams as they optimize procedures in a relatively new surgical field.