Bone Fixation Plate With Locking Screw Mechanism
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Solution Overview
Problem
Current sternum fixation methods, such as stainless steel wire sutures, are prone to loosening due to low cyclic forces from breathing, especially in osteoporotic patients, leading to complications like mediastinitis and increased mortality, as they fail to provide stable fixation in low-density bones.
Innovation Solution
A screw and plate assembly with a locking mechanism that minimizes micro-movement, featuring a higher torque capability, increased thread density for cortical bone, and a cap to secure the screw to the plate, preventing sawing effects and optimizing fixation in both cortical and cancellous bone types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If stainless steel wire sutures are used for sternal fixation, then the procedure is simple and cost-effective, but the fixation loosens due to low cyclic forces from breathing, especially in osteoporotic patients
Solution Approach 1:
The patent changes the mechanical parameters of the fixation system by transitioning from flexible wire sutures to rigid plate and screw assemblies. The plate provides rigid stabilization while the screws with locking mechanisms maintain fixed angular relationships, fundamentally altering how forces are distributed and resisted during breathing cycles.
Solution Approach 2:
The fixation system combines dissimilar materials and structural elements - a rigid plate component with multiple screw components, where at least one screw is locked at a specific angle relative to the plate. This composite assembly integrates different mechanical properties to achieve both stability and adaptability for various bone densities including osteoporotic conditions.
2Reliability
If rigid fixation techniques with plate and screw assembly are used, then fixation stability is improved, but the procedure time increases and surgeon skill requirement increases
Solution Approach 1:
The plate and screws are designed as pre-configured components where the plate includes predetermined openings and the screws are designed to be inserted at specific angles. The locking mechanism allows screws to be secured at fixed angular relationships before final assembly, reducing intraoperative adjustment time and simplifying the surgical procedure while maintaining rigid fixation stability.
3Reliability
If locked screws are used to prevent micro-movement, then fixation stability is improved, but the device complexity increases
Solution Approach 1:
The fixation system is divided into distinct functional segments: a plate component with multiple openings, individual screw components with heads, and a locking mechanism. This segmentation allows each component to be optimized independently - the plate provides rigid support, the screws provide angular adjustment, and the locking mechanism secures the configuration - while collectively achieving stable fixation without excessive overall complexity.
Data Source
AI summary
An assembly for rigid bone fixation includes a plate and a screw. The screw can be rotated freely within the plate in a non-locking configuration to secure the plate against the bone. A locking mechanism is engaged to prevent the screw from moving relative the plate. In one embodiment, the plate includes a threaded portion and a non-threaded portion. The screw head rotates within the non-threaded portion to tighten the screw and pull the plate against the bone. The locking mechanism can include a moveable nut that rotates within the threaded portion of the plate to lock the screw and plate in a locking mode. The locking mechanism can include a second screw to actuate and expansion portion of screw inserted into the bone. The assembly can be used for rigid fixation of bones that experience cyclic loads, such as the sternum and mandible. Methods of rigid bone fixation are also described.