A Study of Changes in Mechanical Properties of Hernia Mesh Material After Exposure to
Concentrated Acids
1.0 INTRODUCTION
Test Procedures:
Shear hysteresis (2HG) improved by 22.39% in the wale direction and 14.76% in the course
direction.
ASTM-D3776: Mass per Unit Area
Mechanical properties evaluated under low deformation loads: Kawabata Evaluation System
Testing: Tensile, Shear, Bending, Compression, Surface
Fabric Strength: ASTM-D2261: Tearing Strength of Fabrics by Tongue Procedure; ASTM-D6797:
Burst Strength Constant Rate of Extension Method; ASTM-D5034: Breaking Strength and Elongation
of Textile Fabrics (Grab Test).
Several health sciences, medical and pharmacological journals assess the
effects of regular or excessive oral dosages of ibuprofen, naproxen, aspirin
or other non-steroidal anti-inflammatory drugs as the leading cause for
chemically induced peptic ulcers.1 A peptic ulcer is a defect in the lining of
the stomach or the first part of the small intestine. If this protective lining
stops working correctly and the lining breaks down, it results in inflammation
(gastritis) or an ulcer. A hole that goes all the way through the stomach or
duodenum is called a perforation causing a medical emergency.
4.0 RESULTS AND DISCUSSION
The major health risk associated with peptic ulcers is that their presence allows gastric acid to flow
freely into the body and come in contact with other tissues and biomaterials (such as hernia mesh)
potentially breaking them down or damaging their ability to function correctly.
A hernia occurs when an organ, intestine or fatty tissue squeezes through a hole or a weak spot in the
surrounding muscle or connective tissue. Hernias often occur at the abdominal wall and are corrected
using an implanted surgical device (typically a synthetically constructed knit structure) to provide
additional support to weakened tissue. The synthetic materials used can be absorbable, nonabsorbable or a combination of the two.
Non-absorbable mesh will remain in the body indefinitely and is
considered a permanent implant. It is used to provide permanent
reinforcement to the repaired hernia. Any factors that alter this permanent
structure present a possible health problem or comfort issue.
2.0 OBJECTIVE
Research in the medical community and in the pharmacology field verifies the correlation between
peptic ulcers (holes forming in the internal organs along the gastro-intestinal track due to high acid
levels) and unregulated, excessive dosages of Ibuprofen and Aspirin. Theoretically, the presence of a
peptic ulcer could provide a transport mechanism that allows high levels of strong stomach acids (pH
of 1.5) to enter into the body and have direct contact with other internal organs and biomaterials
possibly disrupting bio-activities and eroding their tissues. This study will examine the mechanical
changes, if any, after non-absorbable hernia mesh is exposed to a strong simulated stomach acid.
Strength Proper es (Control vs Exposed)
50
40.88
40
32.84
35
31.34
30
25
Control
20
Exposed
15
9.05 9.01
5
1.16 1.15
1.1 1.08
Wale
Course
0
Tongue Tear (kg)
Wale
Course
Grab Break (kg)
Burs ng Strength
(PSI)
Figure 3 SEM Images of Unexposed (left) and Exposed (right) Hernia Mesh
Figure 1 indicates that after completing multiple strength tests the hernia mesh exhibited
minimal changes to its overall strength properties. In each trial, the test brings the mesh to
failure but showed in some cases to be slightly more resistant to breaking. Overall, the textile
exhibited no significant change in strength.
Tensile
5.0 CONCLUSIONS & FUTURE WORK
Shear
In summary, the results showed no change in ASTM strength properties. However, the
mechanical properties observed by Kawabata testing showed significant changes. Future work
could examine the potential linkage between the changes observed in the mechanical
properties and any perceived changes in comfort level the patient might experience during the
presence of a peptic ulcer.
A longer exposure time (14 days) could be used to determine if more significant changes in
properties would be observed.
Compression
Gastric Phase and
Constituents
At the moment, poly-glycolic acid is being substituted for the common polypropylene hernia
mesh to absorb other contaminates in the body.5 Textiles that are considered absorbable
surgical devices could be examined to compare the results obtained from a non-absorbable
mesh.
Bending
6.0 REFERENCES
Surface
1 "Peptic
Ulcer." Mayo Foundation for Medical Education and Research (MFMER) (2011). Web.
2Malfertheiner, Peter, Francis K L Chan, and Kenneth E L McCall. Peptic Ulcer Disease. Wiley
Online Resources. Department of Gastroenterology, Hepatology and Infectious Diseases, 14 Aug.
2009. Web.
3Tamplin, Mark L. "Inactivation of Escherichia Coli O157:H7 in Simulated Human Gastric Fluid."
Applied and Environmental Microbiology 71.1 (2005): 320-25. Web.
4 Koeppen, Bruce M., and Bruce A. Stanton. "The Gastric Phase of the Integrated Response to a
Meal." Berne & Levy's Physiology. 6th ed. New York: Mosby, 2009. 1-6. Print.
5Craig, PH, JA Williams, KW Davis, AD Magoun, AJ Levy, S. Bogdansky, and JP Jones. "A Biologic
Comparison of Polyglactin 910 and Polyglycolic Acid Synthetic Absorbable Sutures." Europe
PubMed Central 141.1 (1975): 1-10. Web.
This solution was prepared by dissolving the following compounds into
1.8L of deionised/distilled water at room temperature with aggregation:
6.3g D-glucose (Sigma-Aldrich/USA), 3.69g NaCl (Fisher-Science
Education/USA), 1.08g KH2PO4 (Sigma/USA), 0.198g CaCl2 (SigmaAldrich/Mexico), 0.666g KCl (Sigma/USA), 0.0239g Porcine salts (Fluka
Analytical/New Zealand), and 0.0239g Glycine (Sigma/Switzerland).
*It should be noted that enzymes were not used because enzymatic
treatments are substrate specific and gastric enzymes do not typically
contain species capable of breakdown breaking down polyesters
polypropylene and other plastics.
There is no visible evidence of deterioration. The difference in appearance in Figure 3 is related to
the difference in specimen preparation for SEM.
Figure 2 Kawabata Testing: Mechanical Properties of Unexposed and Exposed Hernia Mesh
Material: Monofilament polypropylene, 66 denier, 48.5g/m2 warp knit (See Figure 3) with the a 28
gauge structure:
Guide Bar 1: 1-0/1-2/2-1/2-3/2-1/1-2, threading: 1in, 1out
Guide Bar 2: 2-3/2-1/1-2/1-0/1-2/2-1, threading: 1in, 1 out
After the solution was thoroughly mixed, 4mL of 37% 12M HCl (SigmaAldrich/USA) was added until the pH meter determined the solution to
be 1.57. The temperature controlled oven was set to 37˚C (98.6˚F).The
cut textile samples were submerged (right) completely into the solution
and the beaker was sealed off using parafilm and placed into the oven
for seven days.
The hernia mesh exhibited a 17.29% reduction in Linearity of Compression (LC) value, indicating a
greater compliance to pressure. A 13.38% improvement in Recovery from Compression (RC) was
also observed.
43.02
45
3.0 MATERIALS AND METHODS
Solution: Simulated gastric fluid (bottom)
was generated for this experiment based
on the methodology found in the Applied
and Environmental Microbiology journal
article by researcher Mark L. Tamplin.3
After extensive research this solution was
the most viable option due to its more
accurate representation of the
constituents (right) present in the human
stomach as per Berne and Levy’s Gastric
Phase text in Physiology, 6th ed.4
The exposed product exhibited reduced bending (B) resistance in both the wale (15.29%) and
course (20.97%) direction, indicating greater ease of movement.
Surface friction (MIU) increased in both the wale (11.27%) and course direction (18.6%). Also noted,
a 34.15% increase in the mean deviation of surface friction (MMD), (an increase in MMD properties
has been identified with a feeling of roughness). SMD (surface roughness) in this case are
measuring the surface contour of the warp knit structure. It is noted the the SMD values increased by
35.77% in the course direction and decreased by 14% in the wale direction.
Figure 1 Strength Properties of the Unexposed and Exposed Hernia Mesh
10
Often treatment periods after a peptic ulcer is diagnosed, depending on
the severity of the perforation, will be between 7 to 14 days.2 Accordingly,
the duration of a peptic ulcer will dictate the quantity of gastric fluids
capable of emptying from the stomach into the body.
Kayla Stevens
Nicholas Rusin
Professor Janet Brady, Advisor
Philadelphia University, The Kanbar College of Design,
Engineering and Commerce
Focusing on those mechanical properties that exhibited the most significant change (i.e. greater
than ten percent) the following was observed:
A greater change in tensile properties was observed in the wale direction of particular note is the
32% decrease in tensile resilience coupled with an increase of 14.8% in extension under
maximum load. The change in these two properties would indicate greater extension coupled
with lower recovery.
ACKNOWLEDGMENTS
The authors wish to acknowledge the support of Philadelphia University and the PURC facility,
Janet Brady, Herbert Barndt, Niny Rao, and Jeffrey Ashley.