Self-Fixing Bone-Tendon-Bone Graft with Threaded Blocks
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Solution Overview
Problem
Current bone-tendon-bone grafts face challenges such as lengthy surgical procedures, difficulty in attaching slippery tendons to bone blocks, and issues with tensile strength and stability, particularly in severe joint injuries like ACL tears, due to the need for interference screws and complex manufacturing processes.
Innovation Solution
A self-fixing bone-tendon-bone graft design featuring threaded bone blocks that can be rotated as a unit for simultaneous insertion into bone tunnels, with a tensioner to apply and adjust tension, and omega-shaped cavities on the bone blocks for enhanced tendon gripping, eliminating the need for interference screws and simplifying the surgical process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional stitching or stapling methods are used to attach tendon to bone blocks, then the surgical procedure can be completed, but the tensile strength and stability of the graft is insufficient
Solution Approach 1:
The bone blocks are designed with self-tapping threaded surfaces that automatically create their own fixation structure in the bone tunnel during insertion, eliminating the need for separate interference screws or complex attachment procedures. The threads engage with the bone tunnel walls to provide robust mechanical interlocking and tensile strength.
Solution Approach 2:
The graft is divided into discrete modular components: bone blocks with threaded surfaces, tendon/ligament material, and optional tensioners. This segmentation allows each component to be optimized independently and assembled during surgery, simplifying the overall attachment process while maintaining strength.
2Reliability
If interference screws are used to fix the bone blocks, then fixation stability is improved, but the surgical time and procedure complexity increase
Solution Approach 1:
The threading feature is integrated directly into the bone block structure, combining the fixation mechanism with the bone block itself. This eliminates the need for separate interference screws and reduces the number of surgical steps while maintaining stable fixation through the threaded engagement with the bone tunnel.
Solution Approach 2:
The bone blocks are pre-formed with threaded surfaces during manufacturing, so that the fixation structure is already in place before surgery. During implantation, the threads are activated by the insertion motion itself, which simultaneously positions and secures the bone block without requiring additional fixation steps.
3Productivity
If the bone blocks are designed with threads for self-fixation, then surgical time is reduced and fixation is simplified, but the manufacturing precision requirements increase
Solution Approach 1:
The thread geometry parameters (pitch, diameter, helix angle) are optimized to balance manufacturability with surgical performance. The threads are designed with dimensions that can be reliably manufactured using standard CNC machining or additive manufacturing, while still providing adequate engagement with the bone tunnel for strong fixation.
Solution Approach 2:
The bone blocks may be constructed from composite materials or multi-layer structures that allow for integrated threading features. This enables the threading to be formed as part of the manufacturing process rather than requiring separate machining operations, reducing manufacturing complexity while maintaining precision.
4Strength
If the tendon is not pre-tensioned, then the assembly is simpler, but the graft lacks the necessary tensile strength and stability
Solution Approach 1:
A tensioning mechanism is incorporated that allows the tendon to be dynamically adjusted and locked at the desired tension level during surgery. The tensioner can be positioned between the bone blocks and features a ratchet or locking mechanism that maintains the applied tension while allowing for easy adjustment during the procedure.
Solution Approach 2:
A tensioner component serves as an intermediary device between the bone blocks and the tendon. This tensioner applies and maintains the necessary tensile force on the tendon, ensuring proper pre-tensioning without requiring the tendon to be directly attached to the bone blocks with complex fixation mechanisms.
Data Source
AI summary
The present invention has multiple aspects relating to assembled self fixing bone-tendon-bone (BTB) grafts and BTB implants. A preferred application in which self fixing assembled bone-tendon-bone (BTB) grafts and implants of the present technology can be used is for ACL repairs in a human patient. In one embodiment, a self fixing BTB graft is characterized by the presence of threads along at least a portion of the exterior surface of one or both bone blocks. In another embodiment, a self fixing assembled bone-tendon-bone implant comprises a removable tendon tensioner which imparts a predetermined tension on the tendon of the BTB graft.