Low Profile Bone Plate Locking via Wire Element
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Solution Overview
Problem
Conventional bone plate and screw systems face challenges with non-locking screws loosening due to micromotion and locking screws being costly, while bone plates with a height of 5 mm or greater complicate wound closure, leading to potential complications.
Innovation Solution
A bone plate system with non-threaded through-holes and standard bone screws using a locking element, such as a flange or wire, to create a locking relationship without the need for specialized screws or increased plate height, allowing for angulated insertion and low-profile design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If locking screws with threaded heads are used to create a stable locking relationship, then the reliability of bone fixation is improved, but the device complexity and cost increase
Solution Approach 1:
The locking function is segmented from the screw head and transferred to a separate locking element (such as a flange or wire) that can be inserted through a non-threaded hole in the bone plate. This allows the screw itself to remain simple while the locking mechanism is provided by a separate component that engages with the bone plate independently.
Solution Approach 2:
A locking element acts as an intermediary component between the screw and the bone plate. This locking element (flange or wire) passes through the non-threaded hole and engages with the bone plate to provide the locking function, while the screw simply provides compression force without needing threaded features.
2Reliability
If bone plate height is increased to 5 mm or greater to accommodate locking screw heads and threads, then the locking relationship is improved, but the ease of operation during wound closure deteriorates
Solution Approach 1:
The threaded features that traditionally required significant bone plate thickness are extracted from the bone plate-screw interface and relocated to a separate locking element. This allows the bone plate to maintain a low profile (less than 5 mm) while still providing effective locking through the separate locking mechanism that engages with the non-threaded hole.
3Device complexity
If non-threaded screw holes are used with standard screws to reduce cost and simplify the system, then the device complexity is reduced, but the reliability of bone fixation deteriorates due to screw loosening from micromotion
Solution Approach 1:
A locking element (flange or wire) serves as an intermediary that transforms the non-threaded hole into an effective locking mechanism. The locking element engages with the bone plate through the non-threaded hole and prevents screw loosening, while the screw itself remains a simple standard screw without threaded features.
Solution Approach 2:
The system changes the parameter of the hole from threaded to non-threaded, and compensates for the loss of locking capability by introducing a separate locking element that provides the necessary mechanical engagement to prevent screw loosening while maintaining simplicity.
Data Source
AI summary
Disclosed embodiments of a low profile bone plate can allow for a locking relationship between the bone plate and one or more bone screws, without requiring specialized bone screws. According to the disclosure, a locking element and/or a flange can be provided in one or more through-holes in the bone plate to engage with the threads of the bone screw, to lock the screw in place. Locking elements, such as a straight wire or spring coil positioned near the bone-contacting surface of the bone plate can have a cross sectional diameter less than the pitch of the bone screw threads, so as not to interfere with insertion and tightening of the bone screw. Thus, standard bone screws without threaded heads or tapered shafts can be locked with a bone plate having a minimal thickness, which can advantageously improve chances of wound healing.