Conical Split Washer Bone Anchor Locking Mechanism
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bone anchor locking devices fail to securely prevent loosening and easy removal of bone anchors in spinal implants, particularly in cervical plates, which can lead to instability and complications during surgical procedures.
Innovation Solution
A bone anchor locking device featuring a conical split washer positioned between a dome and a base, allowing the bone anchor to be securely locked by expanding against the base upon insertion and retracting to prevent backout, with a release mechanism using a tubular tool to facilitate easy removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional locking device is used to secure bone anchors, then the bone anchor is held in place, but the device fails to prevent loosening and easy removal, leading to instability
Solution Approach 1:
The split washer transitions from a compressed state (allowing insertion) to an expanded state (preventing removal). The washer is compressed during installation to allow the bone anchor to pass through, then expands to lock against the domed chamber wall, creating a dynamic locking mechanism that adapts to the insertion and retention phases
Solution Approach 2:
The locking device is divided into separate functional components: a split washer for dynamic expansion/contraction, a domed chamber for constraint, and a recessed base for positioning. This segmentation allows each component to perform its specific function optimally - the split washer provides the locking action while the dome and base provide structural support
2Reliability
If the bone anchor is securely locked to prevent loosening, then stability is improved, but removal becomes difficult
Solution Approach 1:
The split washer's dynamic expansion and contraction properties enable it to lock securely during normal operation while allowing controlled removal when needed. The washer can be compressed back to its smaller diameter using a removal tool, releasing the lock and enabling bone anchor extraction
Solution Approach 2:
A removal tool acts as an intermediary to compress the split washer back to its insertion diameter. This intermediary device temporarily overrides the locking mechanism by applying compressive force through the dome, allowing the bone anchor to be removed without damaging the implant components
3Reliability
If the locking device uses a complex mechanism to prevent loosening, then reliability improves, but device complexity increases
Solution Approach 1:
The split washer is a self-actuating component that automatically expands to lock the bone anchor in place without requiring additional actuators, springs, or complex mechanisms. The expansion is driven directly by the insertion force of the bone anchor itself, eliminating the need for separate locking mechanisms
Solution Approach 2:
The locking function is merged with the structural support function by integrating the split washer with the domed chamber and recessed base. The dome and base are not merely structural elements but actively participate in the locking mechanism by providing surfaces for the washer to expand against and lock against
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 device effectively secures bone anchors, reducing the risk of loosening and simplifying the removal process, thereby enhancing surgical stability and ease of use.
Implementation Method 1
The split washer has an inner conical surface sloped to slide and expand against at least a portion of the base on insertion of a bone anchor to allow a maximum diameter of a head of a bone anchor to pass and thereafter the split washer retracts
Data Source
AI summary
A bone anchor locking device for receiving a bone anchor having a shank and an enlarged head, the device has a bone anchor, a dome and a conical split washer. The receiving portion has a base extending radially outward and inwardly to a wall. The dome has a center aperture sized to pass a bone anchor. The split washer has an inner conical surface sloped to slide and expand against at least a portion of the base on insertion of a bone anchor to allow a maximum diameter of a head of a bone anchor to pass and thereafter the split washer retracts overlying the maximum diameter of the head to prevent a bone anchor from backing out.