Bone Anchor Compression Cap Snap-Fix Retention
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Solution Overview
Problem
Traditional bone anchor fixation methods require deformation of the receiver member, which can weaken the structure and increase manufacturing costs and time, and there is a risk of the compression member being misplaced or lost during surgical procedures.
Innovation Solution
A bone screw assembly with a compression cap and receiver member featuring opposed projections and complementary recesses that snap into engagement, allowing for secure fixation without the need for deformation, reducing the risk of misplacement and maintaining the compression cap in a fixed position relative to the receiver member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the swaging process is used to secure the compression member to the receiver member, then the compression member is prevented from moving or being lost, but the structure of the bone anchor is weakened and manufacturing time increases
Solution Approach 1:
The compression member is divided into multiple segments or portions that can be independently deformed. This allows the deformation force to be distributed across different sections, preventing concentration of stress at a single point and thus avoiding structural weakening of the bone anchor while still achieving secure retention.
Solution Approach 2:
The deformation process changes the physical parameters of the compression member, specifically its cross-sectional shape and dimensional properties. By controlling these parameter changes through staged deformation, the compression member achieves permanent engagement with the receiver member without requiring excessive force that would weaken the overall bone anchor structure.
2Reliability
If the swaging process is used to secure the compression member, then the compression member is fixed in position, but manufacturing expense and time increase
Solution Approach 1:
Dividing the compression member into segments enables parallel or sequential deformation processes that can be more efficiently managed during manufacturing. This segmentation allows for optimized tooling and process sequencing, reducing total manufacturing time while maintaining reliable fixation.
Solution Approach 2:
The compression member is pre-formed with specific geometric features or preliminary deformations that facilitate the final securing process. This preliminary action reduces the complexity and time required for the final deformation step, while ensuring reliable fixation is achieved.
3Reliability
If traditional compression members are used, then secure fixation can be achieved, but there is a risk of misplacement or loss before securing
Solution Approach 1:
The compression member incorporates preliminary engagement features or self-centering geometries that automatically align it with the receiver member upon insertion. This preliminary action eliminates the risk of misplacement before securing, as the design inherently guides proper positioning, while still achieving reliable fixation through the subsequent deformation process.
Data Source
AI summary
Various exemplary methods and devices are provided for fixing bone anchors to bone. In general, the methods and devices can allow for a bone anchor to be fixed to a bone at a desired angle to a surface of the bone. In an exemplary embodiment, a bone anchor assembly is provided that includes a bone anchor configured to engage bone, a receiver member for seating a head of the bone anchor, and a compression member for securing the bone anchor at fixed angle with respect to the receiver member when the compression member is seated within the receiver member. Corresponding engagement features of the compression member and the receiver member can be engaged in a secured configuration to inhibit or prevent removal of the compression cap from the receiver member and optionally to substantially prevent longitudinal and/or rotational movement of the compression member with respect to the receiver member.