Saud Aldeghaither, Benjie Tang, Donald McLean, Emma Wright, Zhigang Wang, Afshin Alijani, Ian Tait, Alfred Cuschieri. Cushieri Skills Center &institute of medical science and technology, University of Dundee,Dundee, Scotland.
Objective
The aim of this study was to investigate the adhesion and retraction properties of C3 bioadhesive polymers, in an ex-vivo model of liver retraction.
Background
Conventional laparoscopic instruments that are used for liver retraction may cause surgical site trauma, and are not suitable for tissue retraction in Lapro-endoscopic single site (LESS) and natural orifice trans-luminal surgery (NOTES) technologies. Bioadhesive retraction systems may decrease surgical site trauma, and overcome the ergonomic difficulties associated with LESS and NOTES soft tissue and solid organ retraction.
Methods and Materials
A model was designed to simulate retraction of the liver that is often required in minimal access surgery (MAS). C3 bioadhesive polymers were attached to the surface of the liver, and the adhesion and retraction properties of these polymers were evaluated. Studies were carried out using an Instron Force machine, and maximum detachment forces, polymer adhesion times, and duration of polymer adhesion with active liver retraction were evaluated. Studies were performed in an ex-vivo porcine liver model where the liver was placed in a scaffold designed to simulate the anatomy of the human liver in the supine position. Body temperature and moisture simulation was achieved by placing the scaffold in a water-bath at 37o. Optimal liver retraction and gallbladder exposure was defined by fixing three colored labels to the gallbladder fundus, infundibulum and biliary tree. The retraction forces were applied and measured by the Instron connected to the C3 polymer disks by a surgical thread. The C3 polymer was reinforced by a plastic disk. In all experiments a retraction acceleration force of 1N/sec was applied, to determine the biological tissue adhesion and retraction properties of the C3 polymer. Data was analysed using the IBM SPSS Statistics 20 software package. Data distribution was evaluated for Skeweness, and results evaluated by Mann-Whitney, and Kruskal-Wallis tests. Relations between groups were studied using Pearson correlation.
Results
31 porcine livers were used in this study. After a 30s application time the force required to detach the C3 polymer from the liver was >20N. The mean force required to provide optimal surgical exposure was 4.85N (SD 0.63); and the average duration of polymer adhesion with good liver retraction was 130 minutes (range 17-240 minutes). Optimal C3 polymer adhesion to the liver was reached after a 30s tissue application time (p=0.02), compared to application times of 10s and 20s. Excessive hydration caused rapid detachment of the polymer from the liver surface.
Conclusion
The adhesion and retraction properties of C3 polymer bioadhesive films are encouraging, and their use as a biological retraction system is feasible and reproducible in an experimental setting. Bioadhesive films may provide a novel method of organ and tissue retraction in minimal access surgery.
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