Comparison of Surface Roughness

INTRODUCTION AND OBJECTIVE:
Surface roughness and irregularity can impact both biocompatibility and encrustation
resistance in a ureteral stent. Denstedt (1998) states that the physical properties of a
device appear to play a role in biocompatibility. He goes on to state that a device with a
smooth surface may be more biocompatible because it reduces the mechanical trauma
at the device-tissue interface (4). Animal studies have validated this by showing less
ureteral reactions such as ulceration, epithelial hyperplasia, inflammation, edema, etc.
in materials with a smooth surface than those that do not have these characteristics.(4)(a)
With regards to encrustation, Yachia (1998) states that “encrustation is affected by
surface properties such as roughness and irregularity, surface charge and zeta potential
(electrokinetic potential), surface hydrophobicity and wetability” (p. 155)(2). While the
actual mechanism for encrustation is multi-faceted, it takes the adherence of proteins on
the stent surface to start the encrustation process. The mechanism of encrustation
involves the following steps(2):
1) Protein molecules adhere to the surface of the stent.
2) These proteins create a conditioning film, known as a biofilm, on the surface.
3) Urease-producing bacteria attach to this biofilm.
4) The bacteria continue to grow and forms a community.
5) The bacteria produce urease which attacks urea and the byproducts raise the urine
pH.
6) The increased pH attracts calcium and magnesium ions to the biofilm matrix.
7) The calcium and magnesium ammonium phosphate crystals are stabilized by the
biofilm matrix
8) Crystals form (2) (3)
Given this, studies(5) have shown that the rougher or more irregular the surface, the
higher the probability for adhesion of protein to the surface and thus a higher propensity
for encrustation.(3)
The purpose of this paper is to report on the evaluated surface roughness of various
ureteral stents using Scanning White Light Interference Microscopy (SWLIM).
(a)
See page 4
Why is ‘Surface Roughness’ Important?
Smooth surfaces may have better biocompatibility and encrustation resistance.(5)
Biocompatibility: Smooth surfaces reduce mechanical trauma at the device-tissue
interface(4). Animal studies have shown less ureteral reactions such as ulceration,
epithelial hyperplasia, inflammation and edema(4).
Encrustation Resistance: The first step in encrustation is protein adherence on the
biomaterial [stent surface](2). Smooth surfaces are less likely to have proteins stick to
them than rough surfaces(3).
METHODOLOGY:
Ureteral stents were investigated by an external laboratory using Scanning White Light
Interference Microscopy (SWLIM) analysis *. These included the following 6Fr stents:
BARD® INLAY OPTIMA® Stent, Boston Scientific PercuFlex™ Plus stent, Boston Scientific
Polaris™ Ultra stent and Boston Scientific Contour™ stent.
Three samples of each stent type were tested. The surface roughness on six different
areas on each stent for a total of 18 data points was measured. Data was then
summarized, and analyzed. The key indicator, Ra, or roughness average, was
evaluated. The higher the Ra value, the rougher the surface area.
RESULTS:
The data show that of the samples tested, the Boston Scientific Contour™ stent
samples yielded an average Ra of 685.3 nm, the highest average of the stent samples,
therefore the roughest surface area. In contrast, the BARD® INLAY OPTIMA® stent had the
lowest average Ra value of 139.6 nm, resulting in the smoothest surface of the samples
evaluated. Below the data are summarized:
N
Lowest Ra
Standard Deviation
BARD® INLAY OPTIMA® Stent
Boston Scientific Contour™ Stent
18
18
72.6
344.8
58.5
185
Boston Scientific PercuFlex™ Plus Stent
18
278.9
99.3
Boston Scientific Polaris™ Ultra Stent
18
204.3
123.7
In addition to the numerical information, visual scans were performed to better depict
the topographical characteristics of the surface. The following images are scans of the
individual stent samples of the individual product families with the lowest Ra’s of all data
points.
SUMMARY:
The evaluation of the n=18 stent samples tested demonstrate that the BARD® INLAY
OPTIMA® stent has a smoother surface than Boston Scientific’s Contour™, PercuFlex™
Plus, and Polaris™ Ultra stents.
•
•
•
The Boston Scientific Polaris™ Ultra stent is 181% rougher than the INLAY
OPTIMA® stent.
The Boston Scientific PercuFlex™ Plus stent and is 284% rougher than the
INLAY OPTIMA® stent.
The Boston Scientific Contour™ stent is 375% rougher than the INLAY OPTIMA®
stent
The smoothness of the INLAY OPTIMA® stent helps reduce protein adhesion and thus (all
other factors being equal), may help reduce the potential for encrustation better than
competitive products. The smoother surface may also reduce ureteral reactions such as
ulceration, epithelial hyperplasia, inflammation, edema, etc. due to reduced mechanical
trauma at the stent-tissue interface.
REFERENCES:
1. “The Effect of Biomaterial Surface Properties on Encrustation of Urological Devices”
Simon Choong, Hugh Whitfield
Journal of Endourology, Vol. 11 (Sl): Sept. 1997
2. Stenting the Urinary System
Daniel Yachia
Mosby Year Book, Inc, St Lousi MO, 1998 pg 78-91, pg 155
3. “Urinary Encrustation of Alloplastic Materials
Simon K.S. Choong, M.S. FRCS, and Hugh N. Whitfield, M.A. M.Chir.,FRCS, FEBU
4. “Biomaterials Used in Urology: Current Issues of Biocompatibility, Infection and
Encrustation”
J.D. Denstedt, T.A. Wollin, G. Reid
Journal of Endourology, Vol.12, No. 6 December 1998 493:500
a. Preclinical data may not correlate to outcomes in humans.
*Study funded by C. R. Bard, Inc.
®
INLAY OPTIMA Ureteral Stent and Multi-Length Ureteral Stent
Indications for Use:
The InLay OPTIMA™ Ureteral Stent and Multi-Length Ureteral Stent with Suture are indicated to relieve
obstruction in a variety of benign, malignant and post-traumatic conditions in the ureter. These conditions
include stones and/or stone fragments, or other ureteral obstructions such as those associated with
ureteral stricture, malignancy of abdominal organs, retroperitoneal fibrosis or ureteral trauma, or in
association with Extracorporeal Shock Wave Lithotripsy (ESWL). The stent may be placed using
endoscopic surgical techniques or percutaneously using standard radiographic technique. It is
recommended that the indwelling time not exceed 365 days. The stent is not intended as a permanent
indwelling device.
Contraindications:
(Refer to the Instructions for Use for the Complete List of Adverse Effects, Precautions, and Warnings.)
There are no known contraindications for use.
Precautions: (Before use, consult product labels and inserts for any indications, contraindications,
hazards, warnings, cautions and instructions for use.)
• Suture may be cut off prior to stent placement. Remove suture if indwelling time is expected to be
longer than 14 days.
• Avoid improper handling of stent such as bending, kinking, tearing, etc. Misuse could damage the
overall integrity of the stent.
• Ureteral stents should be checked periodically for signs of encrustation and proper function.
Periodic checks of the stent by cystoscopic and/or radiographic procedures are
recommended at intervals deemed to be appropriate by the physician in consideration of the
individual patient’s condition and other patient specific factors. When long-term use is indicated,
it is recommended that indwelling time not exceed 365 days. The stent is not intended as a
permanent indwelling device. *
• With any ureteral stent, migration is a possible complication, which could require medical intervention
for removal. Selection of too short a stent may result in migration.
• Care should be exercised when removing the stent from the inner polybag to eliminate tearing or
fragmentation.
• The insertion of a ureteral stent should only be done by those individuals who have comprehensive
training in the techniques and risks of the procedure.
Potential Complications:
Potential complications associated with retrograde/antegrade positioning of indwelling ureteral stents
include the following:
• Edema • Stone formation • Peritonitis • Extravasation • Ureteral reflux • Stent dislodgement,
fragmentation, migration, occlusion • Fistula formation • Loss of renal function • Hemorrhage •
Pain/Discomfort • Stent encrustation • Hydronephrosis • Perforation of kidney, renal pelvis, ureter, and/or
bladder • Ureteral erosion • Infection • Urinary symptoms
Warning:
After use this product may be a potential biohazard. Handle and dispose of in accordance with
acceptable medical practice and with applicable local, state and federal laws and regulations.
For the latest information, always check the “Instructions for Use” that comes packaged with the
product.
Please consult product labels and inserts for any indications, contraindications, hazards,
warnings, cautions and directions for use.
Bard and InLay Optima are registered trademarks of C. R. Bard Inc.
All other trademarks are property of their respective owners.
Copyright © 2014 C. R. Bard, Inc. All Rights Reserved
1403-32
R03/14
THP
P05/14 2.5M