Mechanical and leakage integrity testing considerations for evaluating the performance of tissue containment systems

Abstract

Tissue containment systems (TCS) are medical devices that may be used during morcellation procedures during minimally invasive laparoscopic surgery. TCS are not new devices but their use as a potential mitigation for the spread of occult malignancy during laparoscopic power morcellation of fibroids and/or the uterus has been the subject of interest following reports of upstaging of previously undetected sarcoma in women who underwent a laparoscopic hysterectomy. Development of standardized test methods and acceptance criteria to evaluate the safety and performance of these devices will speed development, allowing for more devices to benefit patients. As a part of this study, a series of preclinical experimental bench test methods were developed to evaluate the mechanical and leakage performance of TCS that may be used in power morcellation procedures. Experimental tests were developed to evaluate mechanical integrity, e.g., tensile, burst, puncture, and penetration strengths for the TCS, and leakage integrity, e.g., dye and microbiological leakage (both acting as surrogates for blood and cancer cells) through the TCS. In addition, to evaluate both mechanical integrity and leakage integrity as a combined methodology, partial puncture and dye leakage was conducted on the TCS to evaluate the potential for leakage due to partial damage caused by surgical tools. Samples from 7 different TCSs were subjected to preclinical bench testing to evaluate leakage and mechanical performance. The performance of the TCSs varied significantly between different brands. The leakage pressure of the TCS varied between 26 and > 1293 mmHg for the 7 TCS brands. Similarly, the tensile force to failure, burst pressure, and puncture force varied between 14 and 80 MPa, 2 and 78 psi, and 2.5 N and 47 N, respectively. The mechanical failure and leakage performance of the TCS were different for homogeneous and composite TCSs. The test methods reported in this study may facilitate the development and regulatory review of these devices, may help compare TCS performance between devices, and increase provider and patient accessibility to improved tissue containment technologies.

Figure 1

Experimental setup for tensile testing.

Figure 2

Schematic of the burst testing setup.

Figure 3

Diagram of the ASTM D2240 durometer pins that were used for the puncture testing in our experiments. Dimensions in brackets are in Inches while the dimentions just below are in millimeters.

Figure 4

Experimental setup for puncture testing.

Figure 5

Schematic of the dye penetration set-up.

Figure 6

Picture of the dye penetration testing apparatus used after the partial puncture testing.

Figure 7

Flow chart describing the partial puncture and subsequent dye penetration testing.

Figure 8

SEM images (cross-sectional view along the thickness) of all seven TCSs.

Figure 9

Planar SEM view of TC#3 taken from the nylon side (left) and polymer side (right). On the polymer side the nylon fibers are leaving an impression on the polymer layer in addition to a few voids in the polymer layer.

Figure 10

Stress–strain relationship from tensile testing of TCS materials. The thicker brighter lines represent the averaged curve (denoted by ‘Average’ here for each TCS material) from the stress–strain curves of all specimens tested of a specific TCS; the last point on the curve also shows the variation with standard deviation of the stress and strain values obtained from all specimens of a specific TCS material. n = 3 for TC# 1, 2, 3, 5; n = 4 for TC# 4, 6; n = 8 for TC#7.

Figure 11

Air pressure as a function of time for different containment systems during burst testing. The thicker brighter lines represent the averaged curve from the pressure–time curves of all specimens tested of a certain containment system; the last point on the curve also shows the variation with standard deviation of the pressure and time values obtained from all specimens of a certain containment system. n = 3 for all TCSs except TC# 4 (n = 4).

Figure 12

The force exerted by the type D durometer pins as a function of compressive displacement of the TCS specimen for two different TCSs.

Figure 13

Maximum force to puncture (F_puncture) for different containment systems from puncture testing using Type OO blunt and Type D sharp durometer pins with one standard deviation error bars. n = 3 for all TCSs.

Figure 14

Partial puncture leak force, F_{leak-puncture,} compared to the full puncture force, F_puncture, for Type D Pin; n = 3 for all TCSs during full puncture testing; For partial puncture testing, n = 3 for TC#4–7, and n = 10 for TC#1&2.