Cannulated Screw Suture Bone Fixation Rotational Control
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Solution Overview
Problem
Current bone fixation methods, such as plate and screw constructs and suture systems, face limitations in providing both rotational control and axial strength perpendicular to the fixation site, with screws experiencing loosening under external forces and sutures offering inferior rotational control.
Innovation Solution
A bone fixation system comprising a cannulated screw, a length of suture, a tensioning tab, and an anchor, where the screw has a threaded external surface and internal passageway for the suture, and the anchor secures the suture ends to create an interference fit and provide rotational control and axial strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If plate and screw constructs are used for bone fixation, then rotational control is provided, but axial strength perpendicular to the fixation site is insufficient due to screw loosening under external forces
Solution Approach 1:
The patent combines a cannulated screw with a suture button construct into a single integrated fixation system. The suture is passed through the cannulated screw and anchored to bone, creating a composite construct that merges the rotational control capability of the screw with the high axial pullout strength of the suture button system.
Solution Approach 2:
The fixation system uses a composite construction combining metal (cannulated screw) with high-strength suture material. This composite approach allows the metal component to provide rotational stability while the suture material provides superior axial strength perpendicular to the fixation site, overcoming the limitations of either material alone.
2Strength
If suture systems are used for bone fixation, then axial pullout strength is greater than traditional plate and screw constructs, but rotational control and control against forces acting in a direction other than the suture axis is inferior
Solution Approach 1:
The patent integrates a suture button system with a cannulated screw, where the suture provides superior axial pullout strength while the cannulated screw component provides the necessary rotational control and stability against forces acting in directions other than the suture axis.
Solution Approach 2:
The cannulated screw acts as an intermediary structure that the suture passes through, allowing the suture to achieve its full axial strength potential while the screw provides the rotational control function that sutures alone cannot provide. The intermediary structure enables both functions to work together synergistically.
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 system achieves a low-profile solution that combines the rotational control of screws with the pullout strength of suture buttons, effectively resisting in-line pullout and providing compressive forces for fracture healing in various orthopedic applications.
Implementation Method 1
The anchor can be dimensioned to create an interference fit inside the passageway of the screw
Implementation Method 2
The screw comprises an elongated shaft having a threaded external surface
Implementation Method 3
the strength depends on cortical opposition to a grapple-like hook, as opposed to the rotation friction obtained via screw threads
Data Source
AI summary
A bone fixation system includes a length of suture, a screw, a tensioning tab, and an anchor. The length of suture has a first end and a second end. The screw comprises an elongated shaft having a threaded external surface, wherein the screw has a distal end, a proximal end, and an internal surface defining a passageway within the screw extending between the distal end and the proximal end, wherein the passageway is configured to receive the length of suture. The tensioning tab is affixed to a section of the length of suture. The anchor is configured to secure the first end of the length of suture adjacent to the proximal end of the screw.