Scanning Electron Microscope Analysis of Ascenda® Catheter kinking
Intrathecal Catheters for Targeted Drug Delivery: Scanning Electron
® Microscope Analysis of Ascenda Catheter kinking
Elizabeth Kregel, BBME, Kara Rodriguez, BBME, Mike Walz, BBME, Amy Nelson, BBME, Haitao Zhang, PhD, Rosa Trejo, BA, MSMS Medtronic, Minneapolis, MN
BACKGROUND Intrathecal catheters must be soft, pliable, and of small diameter, but also remain stable and patent to function as intended for targeted drug delivery in the intrathecal space.
Engineering Testing on the Benchtop
Physician Input
Kink seen proximal to anchor
Figure 3: Iterative Testing Methodology Polyurethane Outer Layers Silicone Inner Layer Polyester Braid
Observational analyses of a subset of returned intrathecal catheter products with possible kinks identified three primary locations along the catheter where potential kinks could be observed (Figure 2). DISTAL TO ANCHOR
Various methods were used throughout the process, and this poster will focus specifically on scanning electron microscope Analysis. Replicating Clinical Scenarios on the Benchtop
PROXIMAL TO ANCHOR
OBJECTIVE: Continue to build in-depth understanding of intrathecal catheter clinical performance, focusing on the potential occurrence of kinking via SEM analysis.
Crease width (µm)
Ascenda Catheter Kinking Computer Modeling of Catheter Bending
CT Scanning of Catheter Kinks
Scanning Electron Microscope Analysis
Figure 5: Kink Observed in a Product Returned From the Field Figure 7: Examples of Crease (Kink) Measurements These images of field returns served as a baseline to compare to samples tested in-house. Bench tests were conducted simulating clinical scenarios that could potentially cause a catheter to kink. These catheters were then analyzed using SEM methods and compared to the images of explanted catheters returned from the field. This SEM comparison identified which in-house kinked catheters and associated benchtop test methods were relevant to clinical scenarios.
Data Mining and Trending
RESULTS Ongoing, iterative testing showed that in vivo catheter kinking can be replicated in benchtop testing. Kink factors are dependent upon kink location and the testing team is continuing to determine contributing factors which may lead to a catheter kink; these factors may depend on the location of the catheter. SEM analysis will continue to be leveraged with ongoing testing to compare results to returned product.
METHODS
Figure 2: A Review of Returned Products Revealed that Kinking is Primarily Localized to Three Areas
Total Width (µm) Mode
Figure 4: Various Methods to Understand Catheter Kinking
NEAR CATHETER TO CATHETER CONNECTOR
Length (µm)
Medtronic engineering, scientific, and medical staff began with formalized brainstorming activities followed by analysis of field complaints and returned products. These process inputs led to multiple, iterative benchtop tests to recreate the clinical environment. Physicians were also involved in the review of findings and results.
Figure 1: Ascenda® Intrathecal Catheter Design Kinking of the pliable catheter tubing is a possible undesired consequence during clinical use conditions (catheter placement within the in vivo tissue environment).
Crease Measurements
Scanning Electron Microscopic (SEM) imaging was leveraged to compare kinked catheters from the field to kinked catheters recreated in-house. SEM analysis allowed comparison of the surface topography of the kinked area to better identify similar potential causes of catheter kinking. As part of the ongoing study, a set of explanted, kinked catheters were obtained from the Returned Product Analysis (RPA) Lab and analyzed using SEM methods. An example is shown in Figure 5 and Figure 6.
Poster 102 | January 19-22, 2017 2017 Annual Meeting of the North American Neuromodulation Society, Las Vegas, Nevada, USA
Figure 6: Kink (from Figure 5) viewed with a SEM These catheter images were then categorized based on the severity of the damaged area. Measurements were taken of each damaged area which included total length, total width, and crease width. Examples of these measurements can be seen in Figure 7.
CONCLUSIONS Continued analysis of the potential for catheter kinking will occur through ongoing testing and SEM analysis. The goal of this study is to identify opportunities for best practices in implant technique and, if needed, further product enhancements.
® Microscope Analysis of Ascenda Catheter kinking
Elizabeth Kregel, BBME, Kara Rodriguez, BBME, Mike Walz, BBME, Amy Nelson, BBME, Haitao Zhang, PhD, Rosa Trejo, BA, MSMS Medtronic, Minneapolis, MN
BACKGROUND Intrathecal catheters must be soft, pliable, and of small diameter, but also remain stable and patent to function as intended for targeted drug delivery in the intrathecal space.
Engineering Testing on the Benchtop
Physician Input
Kink seen proximal to anchor
Figure 3: Iterative Testing Methodology Polyurethane Outer Layers Silicone Inner Layer Polyester Braid
Observational analyses of a subset of returned intrathecal catheter products with possible kinks identified three primary locations along the catheter where potential kinks could be observed (Figure 2). DISTAL TO ANCHOR
Various methods were used throughout the process, and this poster will focus specifically on scanning electron microscope Analysis. Replicating Clinical Scenarios on the Benchtop
PROXIMAL TO ANCHOR
OBJECTIVE: Continue to build in-depth understanding of intrathecal catheter clinical performance, focusing on the potential occurrence of kinking via SEM analysis.
Crease width (µm)
Ascenda Catheter Kinking Computer Modeling of Catheter Bending
CT Scanning of Catheter Kinks
Scanning Electron Microscope Analysis
Figure 5: Kink Observed in a Product Returned From the Field Figure 7: Examples of Crease (Kink) Measurements These images of field returns served as a baseline to compare to samples tested in-house. Bench tests were conducted simulating clinical scenarios that could potentially cause a catheter to kink. These catheters were then analyzed using SEM methods and compared to the images of explanted catheters returned from the field. This SEM comparison identified which in-house kinked catheters and associated benchtop test methods were relevant to clinical scenarios.
Data Mining and Trending
RESULTS Ongoing, iterative testing showed that in vivo catheter kinking can be replicated in benchtop testing. Kink factors are dependent upon kink location and the testing team is continuing to determine contributing factors which may lead to a catheter kink; these factors may depend on the location of the catheter. SEM analysis will continue to be leveraged with ongoing testing to compare results to returned product.
METHODS
Figure 2: A Review of Returned Products Revealed that Kinking is Primarily Localized to Three Areas
Total Width (µm) Mode
Figure 4: Various Methods to Understand Catheter Kinking
NEAR CATHETER TO CATHETER CONNECTOR
Length (µm)
Medtronic engineering, scientific, and medical staff began with formalized brainstorming activities followed by analysis of field complaints and returned products. These process inputs led to multiple, iterative benchtop tests to recreate the clinical environment. Physicians were also involved in the review of findings and results.
Figure 1: Ascenda® Intrathecal Catheter Design Kinking of the pliable catheter tubing is a possible undesired consequence during clinical use conditions (catheter placement within the in vivo tissue environment).
Crease Measurements
Scanning Electron Microscopic (SEM) imaging was leveraged to compare kinked catheters from the field to kinked catheters recreated in-house. SEM analysis allowed comparison of the surface topography of the kinked area to better identify similar potential causes of catheter kinking. As part of the ongoing study, a set of explanted, kinked catheters were obtained from the Returned Product Analysis (RPA) Lab and analyzed using SEM methods. An example is shown in Figure 5 and Figure 6.
Poster 102 | January 19-22, 2017 2017 Annual Meeting of the North American Neuromodulation Society, Las Vegas, Nevada, USA
Figure 6: Kink (from Figure 5) viewed with a SEM These catheter images were then categorized based on the severity of the damaged area. Measurements were taken of each damaged area which included total length, total width, and crease width. Examples of these measurements can be seen in Figure 7.
CONCLUSIONS Continued analysis of the potential for catheter kinking will occur through ongoing testing and SEM analysis. The goal of this study is to identify opportunities for best practices in implant technique and, if needed, further product enhancements.
