Quantifying the forces needed for ureteral stent removal: Initial evaluation of magnetic stent removal devices on benchtop and porcine models.
Animal models
Magnetic force
Pediatric
Porcine
Preclinical studies
Ureteral stent
Journal
Journal of pediatric urology
ISSN: 1873-4898
Titre abrégé: J Pediatr Urol
Pays: England
ID NLM: 101233150
Informations de publication
Date de publication:
Oct 2020
Oct 2020
Historique:
received:
31
12
2019
accepted:
21
03
2020
pubmed:
29
4
2020
medline:
22
6
2021
entrez:
29
4
2020
Statut:
ppublish
Résumé
Indwelling ureteral stents are commonly used in pediatric surgeries for kidney stones and urinary tract obstruction, but often require instrumentation or anesthesia for removal. We evaluated the use of novel magnet devices to remove indwelling ureteral stents with a distally attached magnetic bead. Since the forces required for stent removal are unknown, we aimed to characterize and quantify the forces required for stent removal for future prototype testing. A custom 3-D urinary tract model was used for benchtop testing, and 6 female porcine subjects were used for in vivo testing after obtaining institutional approval. A modified porcine urethral model that patterned the human female urethral anatomy with approximately 4.5 cm urethral length was used. A HF-10 digital force gauge measured the force required to remove stents with varying properties (stent size, presence of curl, and size of distal magnetic bead). These force measurements were compared to the quantified magnetic forces generated by external magnets and catheter tip magnets. Furthermore, the magnetic retrieval devices were tested with various magnetic beads on both benchtop and porcine models. The required force for removal of a 5 Fr x 14 cm double J stent was significantly higher in the benchtop model compared to the porcine model (4.7N v. 0.8N, p < 0.001). Forces of at least 1N were required from the external magnets to move the stent and bead across a 4-5 cm distance from the bladder neck to the urethral meatus. External magnets at a distance of 4-5 cm produced insufficient forces for removal, and thus they failed to remove the magnetic bead and stent from the bladder. The catheter-based retrieval device showed better success with a variety of different magnet pairs on the retrieval device and stent. Furthermore, the addition of saline to the bladder allowed for better retrieval rates of the smallest beads, even by the smallest magnetic tip catheters. The forces required for ureteral stent removal are <1N in the porcine model, and improved benchtop models that emulate such parameters will facilitate future stent removal device testing. Given this threshold, external magnets did not generate sufficient force for stent removal at the required distance of 4-5 cm, whereas catheter tip magnetic retrieval overcomes the minimum distance limitation and showed successful retrieval. While these results are encouraging, further studies will define the optimal combination of catheter magnetic tip size and stent magnetic bead size.
Sections du résumé
BACKGROUND
BACKGROUND
Indwelling ureteral stents are commonly used in pediatric surgeries for kidney stones and urinary tract obstruction, but often require instrumentation or anesthesia for removal. We evaluated the use of novel magnet devices to remove indwelling ureteral stents with a distally attached magnetic bead. Since the forces required for stent removal are unknown, we aimed to characterize and quantify the forces required for stent removal for future prototype testing.
METHODS
METHODS
A custom 3-D urinary tract model was used for benchtop testing, and 6 female porcine subjects were used for in vivo testing after obtaining institutional approval. A modified porcine urethral model that patterned the human female urethral anatomy with approximately 4.5 cm urethral length was used. A HF-10 digital force gauge measured the force required to remove stents with varying properties (stent size, presence of curl, and size of distal magnetic bead). These force measurements were compared to the quantified magnetic forces generated by external magnets and catheter tip magnets. Furthermore, the magnetic retrieval devices were tested with various magnetic beads on both benchtop and porcine models.
RESULTS
RESULTS
The required force for removal of a 5 Fr x 14 cm double J stent was significantly higher in the benchtop model compared to the porcine model (4.7N v. 0.8N, p < 0.001). Forces of at least 1N were required from the external magnets to move the stent and bead across a 4-5 cm distance from the bladder neck to the urethral meatus. External magnets at a distance of 4-5 cm produced insufficient forces for removal, and thus they failed to remove the magnetic bead and stent from the bladder. The catheter-based retrieval device showed better success with a variety of different magnet pairs on the retrieval device and stent. Furthermore, the addition of saline to the bladder allowed for better retrieval rates of the smallest beads, even by the smallest magnetic tip catheters.
CONCLUSIONS
CONCLUSIONS
The forces required for ureteral stent removal are <1N in the porcine model, and improved benchtop models that emulate such parameters will facilitate future stent removal device testing. Given this threshold, external magnets did not generate sufficient force for stent removal at the required distance of 4-5 cm, whereas catheter tip magnetic retrieval overcomes the minimum distance limitation and showed successful retrieval. While these results are encouraging, further studies will define the optimal combination of catheter magnetic tip size and stent magnetic bead size.
Identifiants
pubmed: 32340884
pii: S1477-5131(20)30074-7
doi: 10.1016/j.jpurol.2020.03.020
pii:
doi:
Types de publication
Journal Article
Langues
eng
Sous-ensembles de citation
IM
Pagination
596.e1-596.e8Informations de copyright
Copyright © 2020 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.