Nested Bone Compression Device for Loosening in Cancellous Bone
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Solution Overview
Problem
Existing bone fixation devices tend to loosen over time due to the soft nature of cancellous bone, leading to discomfort and potential need for recurring surgery, as they fail to provide strong and stable compression of bone fragments.
Innovation Solution
A bone compression device featuring an elongated fastener with an externally threaded portion and an anchor with an internally threaded bore, along with a locking screw to prevent relative rotation, which compresses bone fragments together and includes washers and a deformable insert to enhance stability and prevent backing out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If compression screws are used to compress bone fragments, then bone fragments are held together, but the screws tend to back out over time due to soft cancellous bone material
Solution Approach 1:
The device employs a nested structure where the compression screw is received within a compression nut, which is then received within a bone anchor. This multi-layer nesting provides progressive stabilization: the compression nut prevents screw backing out, while the bone anchor prevents nut rotation, creating a hierarchical locking system that addresses the reliability issue of screw loosening in soft bone material.
Solution Approach 2:
The fixation system is divided into separate functional components: the compression screw for applying force, the compression nut for locking the screw position, and the bone anchor for securing the entire assembly. This segmentation allows each component to perform its specific function optimally, with the anchor providing stable anchorage in the bone while the nested screw-nut mechanism provides compression and locking.
2Stability of the object's composition
If fixation devices are used to secure broken bone parts, then bone fragments are held together, but the devices may disassemble as screws and nails loosen from the bone material
Solution Approach 1:
The nested arrangement of the compression screw within the compression nut within the bone anchor creates multiple levels of constraint. The screw is constrained by the nut, which is constrained by the anchor, providing redundant stabilization that prevents disassembly even if one component loosens, thereby maintaining both alignment and device integrity.
Solution Approach 2:
The compression nut is pre-threaded onto the compression screw before insertion, and the entire assembly is pre-loaded with compression force. This preliminary configuration ensures that the bone fragments are compressed and locked in place from the moment of insertion, preventing subsequent loosening and maintaining stability.
3Strength
If an anchor with internally threaded bore is used to receive the fastener, then the fastener can be secured, but relative rotation between fastener and anchor may occur
Solution Approach 1:
The compression nut is nested within the bone anchor and threaded onto the compression screw. This nested configuration creates a second threading interface that prevents relative rotation between the screw and anchor. The nut acts as an intermediate locking element that secures the screw's rotational position while the anchor secures the nut's position.
Solution Approach 2:
The compression nut serves as an intermediary component between the compression screw and the bone anchor. It mediates the connection by providing a threaded interface with the screw while being received by the anchor, thereby preventing direct rotational movement between the screw and anchor and ensuring rotational stability.
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 compresses and stabilizes bone fragments, reducing the risk of loosening and discomfort, while supporting the fracture against bending stresses, thus promoting healing with a strong and secure fixation.
Implementation Method 1
an elongated fastener with an externally threaded portion, an anchor with an internally threaded bore for threadedly receiving the externally threaded portion of the fastener
Implementation Method 2
a lock for locking together the fastener and the anchor against relative rotation. The lock may be in the form of an externally threaded locking screw threadedly receivable within the anchor
Implementation Method 3
An anchor shoulder engages a rim of the second bore such that in an operative position the anchor shoulder and the fastener head portion compress the first and second bone fragments together
Data Source
AI summary
Embodiments of the invention provide a bone compression device for fixing first and second bone fragments together. The device includes an elongated fastener threadedly receivable within an anchor and a lock movably positioned within the anchor bore to lock the fastener and anchor against relative rotation. The lock may include an externally threaded locking screw threadedly receivable within the anchor coaxial with the fastener shank. The locking screw can be advanced within the anchor bore to lock the position of the fastener shank portion within the anchor bore. Embodiments of the device may be inserted within first and second bores formed in two bone fragments and tightened to compress the two bone fragments together.