Development of a Measurement System for Laparoendoscopic Single-Site Surgery: Reliability and Repeatability of Digital Image Correlation for Measurement of Surface Deformations in SILS Port

OBJECTIVE Analysis of mechanical measurements in laparoendoscopic single-site surgery (LESS) is important for instrument design and surgical simulators. The aim of this study was to develop a measuring system for different instruments and manipulations in LESS using a single-incision laparoscopic surgery (SILS) port. METHODS The loads on the SILS port were applied and recorded by the universal material testing machine by the following method. The handle of the forceps inserted in the SILS port was connected with the machine by a fishing wire and pulled at a constant rate. The surface deformations (displacements and strains) of the SILS port were recorded with digital image correlation (DIC) simultaneously. The correlation between deformation measurements and loads were analyzed. This experiment was repeated 8 times. RESULTS Strong correlations existed between deformation measurements calculated by DIC and objective criteria "loads" applied and recorded by the universal material testing machine (r>0.98). The correlation coefficients were statistically significant (P<.001). A high repeatability of the results appeared in all repetitions of the experiment. CONCLUSIONS A DIC measurement system has been developed for LESS, and comprehensive mechanical parameters of a SILS port can be obtained precisely by using this system. It is reliable and repeatable for evaluation of instruments and manipulations in LESS.