Bone Fixation System with Locking Cap and Set Screw
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Solution Overview
Problem
Traditional wire or pin fixation in orthopedic surgeries lacks compression and rotational control, leading to complications such as nonunion and malunion, especially in small bone fractures and joint arthrodesis.
Innovation Solution
A bone fixation system comprising a cap with a body and stem portion, a wire with a threaded end, and a set screw, which provides compression and rotational stability by anchoring the wire in one bone portion and compressing the cap against the other bone portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional wire or pin fixation is used, then the application is simple, but compression and rotational control are lacking
Solution Approach 1:
The fixation system is divided into separate functional components: a K-wire for insertion, a locking cap with set screw for compression and rotation control, and a threaded anchor for secure fixation. This segmentation allows each component to perform its specific function optimally while maintaining overall system simplicity.
Solution Approach 2:
The system transitions from a static wire fixation to a dynamic locking mechanism where the cap can be adjusted along the wire and the set screw can be tightened to provide progressive compression and rotational stability as healing progresses.
2Reliability
If screw fixation devices are used for small bone fractures, then compression and rotational control are provided, but the devices are too large and may cause further fracturing
Solution Approach 1:
The locking cap and set screw mechanism nests around the K-wire, creating a compact fixation system that provides screw-like compression and rotational control without requiring a large screw head or complex implant structure that would create stress concentrators in small bones.
Solution Approach 2:
The K-wire serves as an intermediary element that transmits compressive forces and prevents rotation without requiring direct bone-to-bone contact through large implants. The wire distributes forces along its length, reducing stress concentration at any single point.
3Reliability
If intra-articular implants are used for small joint arthrodesis, then arthrodesis can be achieved, but the implants are expensive and require complex implantation
Solution Approach 1:
The K-wire with locking cap system serves multiple functions: it provides compression, prevents rotation, maintains alignment, and secures bone fragments together. This multi-functional approach eliminates the need for specialized intra-articular implants and complex implantation procedures while achieving reliable arthrodesis.
4Ease of manufacture
If traditional wire fixation is used, then the procedure is cost-effective, but nonunion and malunion occur due to excess motion
Solution Approach 1:
The locking cap and set screw are prepared in advance and can be quickly assembled onto the K-wire during surgery. The system pre-loads compression forces and locks rotational movement before the bone heals, preventing excess motion that would lead to nonunion or malunion while maintaining the cost-effectiveness of wire fixation.
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 improved compression and rotational stability, reducing the risk of nonunion and malunion, and is suitable for fixing small bone fractures and joint arthrodesis with fewer complications.
Implementation Method 1
a wire with a first end and a threaded second end anchorable in the second bone portion
Implementation Method 2
the cap may be movable along wire toward the threaded second end of the wire to decrease a distance between the cap and the threaded second end of the wire
Implementation Method 3
A set screw may be receivable in the second bore of the cap; the set screw may be actuable to contact the wire to fix a position of the wire within the first bore
Implementation Method 4
the stem portion of the cap includes one or more anti-rotation features that contact the first bone portion in response to pressure urging the cap against the first bone portion to prevent rotation of the cap
Data Source
AI summary
A system and method for osseous fixation is a surgical hardware device that allows bone fixation for purposes of fracture repair, arthrodesis, or other types of orthopedic applications. A partially threaded wire or pin is inserted into the bone and external compression and rotational stability are achieved with a locking cap. The locking cap may include serrations or other anti-rotation features which engage bone to provide rotational stability. Upon adequate bone healing, the external cap may be used to facilitate removal of the wire/pin from the bone.