Non-Circular PTFE Suture for Knot Retention and Hydrolysis Resistance
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Solution Overview
Problem
Existing nonabsorbable surgical sutures of USP sizes 12-0, 11-0, 10-0, 9-0, and 8-0 face issues such as degradation due to hydrolysis, reduced tensile strength and material cohesion at knots, and inadequate knot retention, limiting their effectiveness in surgical procedures.
Innovation Solution
Development of a USP Class I nonabsorbable surgical suture with a synthetic fiber featuring a non-circular cross-section, increased porosity, compliance, and reduced coefficient of friction, which maintains structural integrity and knot security over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional monofilament sutures are used, then the suture is easy to manufacture and handle, but the suture degrades due to hydrolysis and loses tensile strength over time
Solution Approach 1:
The suture combines polytetrafluoroethylene (PTFE) base material with expanded porous structure to create a composite that resists hydrolysis while maintaining tensile strength. The PTFE material inherently resists chemical degradation, and the expanded porous structure adds mechanical properties that prevent collapse and maintain strength over time.
Solution Approach 2:
The suture uses an expanded porous PTFE structure with controlled porosity (30-80%) that provides resistance to hydrolysis while maintaining mechanical integrity. The porous structure allows for tissue ingrowth and bonding without compromising the suture's tensile strength or promoting degradation.
2Reliability
If conventional circular cross-section sutures are used, then the suture has uniform strength, but the suture has inadequate knot retention and slips
Solution Approach 1:
The suture transitions from a circular cross-section to a non-circular (flattened or oval) cross-section with reduced width in one dimension. This asymmetric shape prevents the suture from rotating within the knot, improving knot retention and preventing slippage while maintaining adequate material cohesion through the PTFE structure.
Solution Approach 2:
The suture maintains a smooth curved cross-sectional shape (oval or flattened circular) that distributes stress evenly while preventing knot slippage. The curved geometry allows the suture to conform to the knot structure without creating sharp stress concentrations that would weaken the material.
3Length of moving object
If the suture diameter is reduced for finer surgical work, then the suture is more suitable for delicate procedures, but the suture has reduced tensile strength
Solution Approach 1:
The suture uses changed material parameters (PTFE with high crystallinity and molecular weight) and structural parameters (expanded porous structure, non-circular cross-section) to achieve high tensile strength in a fine diameter suture. These parameter changes allow the suture to maintain strength-to-diameter ratio superior to conventional monofilament sutures.
Solution Approach 2:
The suture optimizes local properties including high-density PTFE regions for strength, porous regions for tissue bonding, and flattened cross-section for knot retention. This local optimization of material and structural properties allows fine diameter to coexist with high tensile strength and knot security.
4Reliability
If the suture has high porosity for tissue bonding, then the suture promotes tissue ingrowth, but the suture may lose structural integrity
Solution Approach 1:
The suture creates a composite structure where PTFE matrix provides structural integrity and strength, while the expanded porous network provides tissue bonding capability. The composite architecture ensures that porosity (30-80%) does not compromise the load-bearing capacity of the suture.
Solution Approach 2:
The suture uses controlled porous PTFE structure where pore size and distribution are optimized to balance tissue ingrowth promotion with structural strength maintenance. The porous structure allows tissue penetration and bonding while the PTFE matrix maintains overall structural integrity and prevents suture failure.
Data Source
AI summary
A surgical suture of a synthetic fiber is provided. The suture includes a non-circular cross-section, and may further include maximal and minimal cross-sectional dimensions with the minimal cross-sectional dimension. The suture may further include a compressible width that supports knot formation and retention, and planar side surfaces that guide knot formation and curvatures. The suture may also include a series of microfilaments that define larger monofilaments or formations that are twisted or braided along the length of the suture.