Interference Screw for Active Tendon-Bone Compression
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Solution Overview
Problem
Current tendon-to-bone fixation techniques in orthopedic surgery are cumbersome, often requiring multiple drill holes, additional accessories, and assistance, with limited tendon-to-bone compression, leading to suboptimal fixation strength and potential complications such as graft tunnel widening and increased surgical time.
Innovation Solution
A device that uses cancellous bone for fixation, providing active tendon-to-bone compression by deploying a wedge mechanism within a single bone tunnel, eliminating the need for additional accessories and allowing single-handed implantation, replicating the native ACL anatomy by shortening graft length and enhancing stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional bone tunnel techniques with suture fixation are used, then tendon to bone fixation is achieved, but the procedure is time-consuming and fixation strength is limited to suture strength
Solution Approach 1:
The invention extracts the fixation function from the suture material and transfers it to the interference screw device. The screw provides direct mechanical fixation to the bone, eliminating reliance on suture strength and reducing surgical time by consolidating multiple fixation steps into a single device insertion.
Solution Approach 2:
The interference screw acts as an intermediary device between the tendon graft and the bone tunnel. It provides a mechanical bridge that transfers load directly to the bone, overcoming the limitations of suture-based fixation and enabling stronger, faster fixation.
2Ease of operation
If bone tunnels are created to allow graft passage, then tendon fixation is enabled, but tunnel creation is complicated and time-consuming
Solution Approach 1:
The bone tunnel is pre-formed before tendon graft insertion, allowing the graft to be passed through easily. The interference screw is then inserted into this pre-prepared tunnel to secure the graft, separating the tunnel creation step from the fixation step and reducing overall surgical time.
Solution Approach 2:
The fixation procedure is segmented into distinct steps: tunnel creation, graft passage, and screw fixation. This segmentation allows each step to be optimized independently, with the pre-formed tunnel facilitating easy graft passage and the subsequent screw insertion providing rapid fixation.
3Strength
If tunnels are made small for good tendon-bone contact, then fixation quality improves, but graft passage becomes difficult
Solution Approach 1:
The interference screw serves as a mediator that allows the use of smaller bone tunnels. The screw provides the necessary mechanical support and fixation strength, enabling the tunnel to be sized optimally for tendon-bone contact while the screw handles the mechanical load of graft passage and fixation.
4Reliability
If multiple drill holes and accessories are used for fixation, then fixation security is improved, but device complexity and surgical procedure become more complicated
Solution Approach 1:
The invention merges multiple fixation functions into a single interference screw device. The screw combines anchoring, compression, and fixation capabilities in one component, eliminating the need for multiple separate accessories and drill holes while maintaining fixation security.
Solution Approach 2:
The interference screw is designed as a universal device that performs multiple functions: it anchors the tendon graft, provides compression against the bone, and secures fixation within the bone tunnel. This multi-functionality reduces the number of separate components needed and simplifies the overall fixation system.
5Strength
If interference screws are used for fixation, then fixation strength is improved, but direct tendon to bone compression is not provided
Solution Approach 1:
The interference screw is designed to provide dynamic compression as it is inserted into the bone tunnel. The screw mechanism allows for adjustable compression force to be applied directly to the tendon graft against the bone surface, enabling both strong fixation and direct compression simultaneously.
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 device achieves high tendon-to-bone fixation strength, exceeding 1,000 N, with improved graft stiffness and reduced surgical complexity, addressing the limitations of existing methods by providing secure and efficient tendon fixation with minimal negative impact on the tendon.
Implementation Method 1
A wedge member is provided convertible between a retracted position and a deployed position. The wedge member is movable for deploying the arm outwardly.
Implementation Method 2
The deploying member comprises a deployment screw having external threading. The wedge member has internal threading receiving the external threading of the deployment screw.
Data Source
AI summary
A soft tissue fixation system, most typically applicable to orthopedic joint repairs, such as anterior cruciate ligament (ACL) knee repair procedures, comprises an implant which is placeable in a tunnel disposed in a portion of hone, wherein the tunnel is defined by walls comprised of bone. A first member is deployable outwardly to engage the tunnel walls for anchoring the implant in place in the tunnel, and a second member is deployable outwardly to engage tissue material to be fixed within the tunnel. The second member also functions to move the tissue material outwardly into contact with the tunnel walls to promote tendon-bone fixation. Extra graft length is eliminated by compression of the tendon against the bone at the aperture of the femoral tunnel, which more closely replicates the native ACL and increases graft stiffness. The inventive device provides high fixation of tendon to bone and active tendon-bone compression. Graft strength has been found to be greater than 1,000 N (Newtons), which is desirable for ACL reconstruction systems.