Elastomeric Tine Fixation for Implantable Devices
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Solution Overview
Problem
Existing tissue-penetrating fixation components for implantable medical devices may compress or occlude blood vessels and cause tissue trauma during implantation and retraction, and they face challenges with cyclic loading and fatigue under chronic implant conditions.
Innovation Solution
The design incorporates tine portions with a hook segment and a short distal segment featuring a tooth and a distal arch, which are elastically deformable to reduce the risk of blood vessel compression and tissue trauma, and include tapering for strain relief and a constant thickness for enhanced fatigue life, allowing for effective penetration and secure fixation while minimizing interference with blood vessels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If tine portions are made long and rigid for secure fixation, then fixation strength is improved, but risk of blood vessel compression and tissue trauma increases
Solution Approach 1:
The tine portion is divided into multiple segments: a proximal segment with first curvature for engagement, a mid-portion with second curvature for flexibility, and a distal segment with third curvature for tissue penetration. This segmentation allows each portion to perform its specific function while reducing overall harm to tissue and blood vessels.
Solution Approach 2:
The tine portion utilizes superelastic material properties with temperature-dependent behavior. At implantation temperature (body temperature), the material exhibits enhanced elasticity and flexibility, allowing the tine to bend and conform to tissue contours, reducing compression on blood vessels while maintaining fixation strength.
2Object-affected harmful factors
If tine portions are made elastic for reduced tissue trauma, then tissue trauma is reduced, but fixation reliability under cyclic loading decreases
Solution Approach 1:
The tine portion is constructed from a composite structure combining superelastic material properties with a multi-curvature geometry. The superelastic material provides both flexibility to reduce tissue trauma and high fatigue resistance to maintain fixation reliability under cyclic loading conditions.
Solution Approach 2:
The tine portion incorporates multiple curvatures (first, second, and third curvatures) along its length. These curved geometries distribute stress more evenly during cyclic loading, preventing stress concentration while maintaining flexibility to reduce tissue trauma.
3Ease of operation
If distal segment is made long for better tissue penetration, then penetration capability is improved, but risk of blood vessel occlusion increases
Solution Approach 1:
The tine portion is segmented into proximal, mid, and distal portions with different curvature characteristics. The distal segment has a third curvature that directs the tip for precise penetration while limiting the overall reach, preventing excessive penetration that could occlude blood vessels.
Solution Approach 2:
The superelastic material properties allow the distal segment to be sufficiently long for effective penetration while remaining flexible enough to bend and avoid rigid compression of blood vessels during and after penetration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the fixation and retraction processes by reducing the risk of blood vessel occlusion and tissue trauma, improving strain relief, and extending the fatigue life of the tine portions, ensuring stable and secure chronic implantation without compromising the integrity of the surrounding tissue or blood supply.
Implementation Method 1
Each tine portion 230 is preferably formed from a superelastic material, such as Nitinol. Figure 3A illustrates device 200 having been loaded into distal end 310 so that a hook segment 231 of each tine portion 230 is elastically deformed, from a pre-set curvature thereof, to an open position
Implementation Method 2
Each tine portion 230 is preferably formed from a superelastic material, such as Nitinol. The full penetration of tine portions 230, shown in Figure 3D, is representative of acute fixation of device 200 at the implant site
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A tine portion of an implantable medical device includes a hook segment and a distal segment extending therefrom, wherein the hook segment is pre-set to extend along a curvature and is elastically deformable therefrom to an open position. The distal segment includes a tooth and an end that surrounds the tooth, wherein the end includes a pair of legs and a distal arch. The legs extend along a length of, and on opposing sides of the tooth, and the distal arch extends between the legs, distal to a tissue-piercing tip of the tooth. When the hook segment is in the open position, and a force is applied along a longitudinal axis of the device, to push the distal arch of the distal segment against tissue, for initial tissue penetration, the legs of the end of the distal segment bend in elastic deformation to expose the tissue-piercing tip to the tissue.