Soft Tissue Tensioner With Universal Joint for Uniform Graft Loading
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Solution Overview
Problem
Current implants and instrumentation for securing soft tissue, particularly the anterior cruciate ligament (ACL), face challenges in achieving uniform tension and secure fixation due to issues such as damage to the graft, loosening of implants, and uneven fixation, which can lead to unsatisfactory repairs.
Innovation Solution
The development of sheaths and tensioners with interdigitating ribs and expandable designs, along with a tensioner mechanism, to ensure uniform tension and secure fixation of soft tissue to bone, using a system that includes a sheath with interlocking ribs and a tensioner with a universal joint for simultaneous tensioning of multiple strands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional interference screws are used to secure soft tissue to bone, then fixation is achieved, but the soft tissue and/or suture can wrap around the threads of the screw causing damage and unequal fixation
Solution Approach 1:
A smooth, rounded button or pledget is introduced as an intermediary element between the interference screw and the soft tissue/suture. This intermediary prevents direct contact between the threaded screw and the soft tissue, eliminating the wrapping and pinching effects while still allowing the screw to provide secure fixation to the bone through the button.
Solution Approach 2:
The fixation system is divided into separate functional components: the interference screw for bone anchorage, the button/pledget for soft tissue interface, and the soft tissue/suture itself. This segmentation allows each component to perform its specific function optimally without the harmful interactions that occur when components are combined into a single element.
2Object-affected harmful factors
If a sheath is positioned between the interference screw and soft tissue to prevent damage, then soft tissue protection is improved, but fixation strength is reduced due to separation from the screw
Solution Approach 1:
The button or pledget serves as an intermediary that maintains both soft tissue protection and fixation strength. It provides a large surface area for soft tissue contact that distributes forces evenly, while simultaneously providing sufficient friction and mechanical engagement with the interference screw to maintain strong fixation.
Solution Approach 2:
The button or pledget changes the physical parameters of the interface between the screw and soft tissue. By providing a smooth, rounded surface with appropriate dimensions and material properties, it transforms the harmful threaded contact into a beneficial friction-based engagement that maintains both protection and strength.
3Manufacturing precision
If each strand of multi-strand graft is tensioned individually to achieve even load distribution, then uniform tension is achieved, but the procedure becomes time-consuming and difficult
Solution Approach 1:
Multiple strands of the graft are merged together and passed through a single button or pledget. This combining allows all strands to be tensioned simultaneously through one integrated structure rather than requiring separate tensioning of each strand, significantly reducing procedure time while maintaining uniform tension through the distributed contact of the button with all strands.
Solution Approach 2:
The button or pledget serves multiple functions simultaneously: it acts as a tensioning device for multiple strands, a protective interface for the soft tissue, and a fixation element for the interference screw. This multi-functionality eliminates the need for separate devices for each function, streamlining the procedure.
4Reliability
If the sheath is expanded to secure the soft tissue, then fixation is improved, but the soft tissue can be pinched or subjected to unequal fixation along its length
Solution Approach 1:
The button or pledget is designed with segmented or distributed contact surfaces that engage with the soft tissue at multiple points along its length. This segmentation ensures that expansion or tightening forces are distributed evenly across all contact points rather than concentrated at a single location, preventing pinching and unequal fixation.
Solution Approach 2:
The button or pledget incorporates local variations in its structure or material properties to optimize the quality of contact at different locations. For example, it may have varying surface textures, compliance, or geometric features at different points to ensure uniform pressure distribution and prevent localized damage while maintaining overall fixation security.
Data Source
AI summary
The present disclosure includes, in one embodiment, a tensioner instrument having a body having a channel and a plurality of arms projecting outward from the body, each arm including a cleat having a slot adapted to receive a suture; a base member positioned within the channel of the body; an actuating mechanism having a first coupling member adapted to engage a second coupling member on the body to removeably couple the actuating mechanism to the body; and a universal joint adapted to allow for relative movement between the base member and the body such that, when each suture is positioned within each cleat and the actuating mechanism is actuated, the tensioner applies uniform tension to each suture positioned in each cleat.