A comparative evaluation of coefficient of friction and mechanical properties of commercially available Foley catheters

Assessment of Urostomy Parastomal Herniation Forces Using Incisional Prevention Strategies with an Abdominal Fascia Model

Background

Approximately 10 000 patients undergo cystectomy/ileal conduit annually in the USA, of whom over 70% subsequently develop a parastomal hernia (PSH). Still, no well-established "best" practice for stoma creation to prevent a PSH exists.

Objective

To measure the relationship between incision size/type/material and axial tension force (ATF) as a surrogate for herniation force, using several models to mimic abdominal fascia.

Design setting and participants

Abdominal fascia models included silicone membrane, ex vivo porcine, and embalmed human cadaveric fascia. A dynamometer pulled a Foley catheter (20 mm/min) with the balloon inflated to 125% incision (linear, cruciate, and circular) diameter using a motorized positioning system. The maximum ATF before herniation was recorded. The study was repeated in unused silicone/tissue for suture reinforcement. We evaluated silicone, ex vivo porcine, and human abdominal fascia.

Intervention

Incision sizes (1-3 cm) in 0.5-cm increments were evaluated in silicone. A 3-cm incision was used in porcine/human tissue.

Outcome measurements and statistical analysis

ATF for herniation was recorded/compared across incision types/sizes using Mann-Whitney U and Kruskal-Wallis tests as appropriate, with α = 0.05.

Results and limitations

Linear incision ATF was significantly greater than cruciate and circular incisions. A cruciate incision had significantly greater ATF than a circular incision. In cadaveric tissue, incisions were significantly greater for linear (34.5 ± 12.8 N) versus cruciate (15.3 ± 2.9 N, p = 0.004) and for cruciate versus circular (p = 0.023) incisions. Results were similar in ex vivo porcine fascia and silicone. Reinforcement with a suture significantly increased ATF in all materials/incision sizes/types. The ex vivo nature is this study's main limitation.

Conclusions

This study suggests that urostomy fascial incision type may influence ATF required for herniation. Linear incisions may be preferable. Urostomy reinforcement may significantly increase ATF required for a PSH. These data may help establish best practices for PSH risk reduction.

Patient summary

The results of this study illustrate that urostomy fascia incision type may influence the force required to create a parastomal hernia. Linear incisions may be preferable.

Development and Characterization of Lactobacillus rhamnosus-Containing Bioprints for Application to Catheter-Associated Urinary Tract Infections

Catheter-associated urinary tract infections (CAUTI) are a significant healthcare burden affecting millions of patients annually. CAUTI are characterized by infection of the bladder and pathogen colonization of the catheter surface, making them especially difficult to treat. Various catheter modifications have been employed to reduce pathogen colonization, including infusion of antibiotics and antimicrobial compounds, altering the surface architecture of the catheter, or coating it with nonpathogenic bacteria. Lactobacilli probiotics offer promise for a "bacterial interference" approach because they not only compete for adhesion to the catheter surface but also produce and secrete antimicrobial compounds effective against uropathogens. Three-dimensional (3D) bioprinting has enabled fabrication of well-defined, cell-laden architectures with tailored release of active agents, thereby offering a novel means for sustained probiotic delivery. Silicone has shown to be a promising biomaterial for catheter applications due to mechanical strength, biocompatibility, and its ability to mitigate encrustation on the catheter. Additionally, silicone, as a bioink, provides an optimum matrix for bioprinting lactobacilli. This study formulates and characterizes novel 3D-bioprinted Lactobacillus rhamnosus (L. rhamnosus)-containing silicone scaffolds for future urinary tract catheterization applications. Weight-to-weight (w/w) ratio of silicone/L. rhamnosus was bioprinted and cured with relative catheter dimensions in diameter. Scaffolds were analyzed in vitro for mechanical integrity, recovery of L. rhamnosus, antimicrobial production, and antibacterial effect against uropathogenic Escherichia coli, the leading cause of CAUTI. The results show that L. rhamnosus-containing scaffolds are capable of sustained recovery of live bacteria over 14 days, with sustained production of lactic acid and hydrogen peroxide. Through the use of 3D bioprinting, this study presents a potential alternative strategy to incorporate probiotics into urinary catheters, with the ultimate goal of preventing and treating CAUTI.

Comparative trial assessing suture techniques and types of urinary catheters in vesicourethral anastomotic tensile strength in a porcine model

PURPOSE

Vesicourethal anastomosis (VUA) during radical prostatectomy can be achieved using various suture plication techniques. Traditionally, an indwelling urinary catheter remains in-situ to facilitate the healing process of the reconstructed VUA. Compromise or rupture of this anastomosis may lead to acute urinary leak and subsequent urinoma or stricture formation. This ex-vivo porcine model aims to evaluate VUA tensile strength using different suture techniques and catheter types.

METHODS

Male porcine bladders were obtained and prostatectomy was performed. The specimens were randomized and VUA were created using 3-point interrupted, 6-point interrupted or 6 point continuous 3-0 monocryl suture. 20Fr catheters were utilized, specifically varying manufacturers (A and B) and catheter balloon shapes (round versus oval). The VUA model was placed within a reproducible pulley system and graduated weights were applied until failure of the catheter balloon or the model VUA. Model failure was defined as either 'VUA rupture', 'Catheter passage through VUA' or 'catheter failure'.

RESULTS

Twenty consecutive porcine bladders were prepared, tested and utilized for analysis. VUA reconstructed with 3-point fixation was more likely to suffer VUA rupture (p=0.025) compared to 6-point interrupted or 6-point continuous VUA. Higher tensile pressure causing catheter balloon rupture (p=0.009) was observed for Manufacturer A. Catheters with oval-balloon shape were more likely to dislodge past the VUA without disruption of the anastomosis (p=0.002).

CONCLUSIONS

During prostatectomy, anastomotic technique and catheter selection can significantly alter the tensile properties of the VUA. Further research is required to validate our findings in clinical models.

Determination of urethral catheter surface lubricity

Device for in-vitro measurement of static and kinetic friction coefficient of catheter surface was developed. Tribometer was designed and constructed to work with exchangeable counter-faces (polymers, tissue) and various types of tubes, in wet conditions in order to mimic in-vivo process. Thus seven commercially available urethral catheters, made from vinyl polymers, natural latex with silicone coating, all-silicone or hydrogel coated, and one made from polyvinylchloride with polyurethane/polyvinylpyrrolidone hydrogel coating obtained in our laboratory, were tested against three various counter faces: polymethacrylate (organic glass), inner part of porcine aorta and porcine bladder mucosa. Additionally, the hydrophility/hydrophobity of tested catheters was stated via water wetting contact angle measurement. Super-hydrophilic biomaterials revealed low friction on tissue and hydrophobic counter-face; slightly hydrophobic showed higher friction in both cases, while more hydrophobic manifested low friction on tissue but high on hydrophobic polymer. The smoothest friction characteristic was achieved in all cases on tissue counter-faces. The measured values of the static coefficient of friction of catheters on bladder mucosa counter-face were as follows: the highest (0.15) for vinyl and siliconised latex catheters and 3 folds lower (0.05) for all-silicone ones. Hydrogel coated catheters exhibited the lowest static and kinetic friction factors.

Frictional properties of poly(MPC-co-BMA) phospholipid polymer for catheter applications

A fundamental understanding of surface properties of the biomaterials at a nanometer scale should be generated in order to understand cellular responses of the tissue to biomaterials thereby minimizing or eliminating tissue trauma at a macrometer scale. In this study poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) ([poly(MPC-co-BMA]) was evaluated as a potential coating material for vascular applications to provide smooth catheterization using atomic force microscopy (AFM) techniques.A uniform coating of [poly(MPC-co-BMA] equivalent to a thickness of 2.5 microm on a polyurethane (PU) catheter material was provided using dip casting technique. Using a contact mode AFM, no significant difference in surface roughness (R(a)) and frictional force (f) between uncoated (R(a)=10.2+/-1.9 nm, f=0.907+/-0.02) and coated (R(a)=11.7+/-1.8 nm, f=0.930+/-0.06) surfaces was observed under dry conditions. However, under wet conditions the R(a) of the coated surface (3.4+/-1.0 nm) was significantly lower than uncoated PU surface (9.0+/-1.8 nm). The coating on PU substrate offered the least frictional resistance (f=0.004+/-0.001) illustrating enhanced boundary lubrication capability due to hydration of phosphorylcholine polymer as compared to a significantly higher f for uncoated PU (0.017+/-0.007) surfaces. These tribological and chemical characteristics of the [poly(MPC-co-BMA)] coating could increase the overall efficacy of PU for clinical applications.