Bone Anchor Sleeve Expansion via Camming Rivet
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Solution Overview
Problem
Existing bone anchors are difficult to implant and prone to dislodgement, leading to tendon or ligament retear and potential damage to surrounding bone.
Innovation Solution
A bone anchor comprising a rivet, a hollow sleeve with axial slits, and an expansion nut, where the sleeve expands into the bone hole upon movement of the rivet and nut, providing secure fixation and resistance to pull-out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing bone anchors are used, then soft tissue can be attached to bone, but the anchors are difficult to implant and prone to dislodgement
Solution Approach 1:
The bone anchor is divided into three separate components: a rivet with head, a hollow sleeve with axial slits, and an expansion nut. These components can be independently manufactured, assembled, and implanted, allowing for easier handling and implantation while maintaining reliable fixation when assembled together
Solution Approach 2:
The hollow sleeve is inserted over the rivet body, and the expansion nut is threaded onto the rivet proximal to the sleeve. This nested arrangement allows all components to be implanted through a single bone tunnel, simplifying the implantation procedure while ensuring proper assembly and reliable fixation
2Strength
If existing bone anchors are used, then soft tissue attachment is achieved, but the anchors are prone to pull-out causing retear or bone damage
Solution Approach 1:
The hollow sleeve transitions from a compressed state during implantation to an expanded state after deployment. The axial slits allow the sleeve to expand radially outward against the bone tunnel walls, creating friction and mechanical interlocking that significantly increases pull-out resistance and prevents tendon retear or bone damage
Solution Approach 2:
The sleeve's radial dimension changes from a small diameter during insertion to a larger diameter after expansion. This parameter change allows the sleeve to pass through the bone tunnel easily and then expand to create strong anchorage, providing high pull-out resistance without causing damage during implantation
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 bone anchor is easily implantable and resistant to pull-out, ensuring stable attachment of soft tissue to bone, reducing the risk of retear and bone damage.
Implementation Method 1
movement of the rivet from a first position to a second position causes the sleeve to cam over the rivet head and expansion nut until said expansion nut engages the shoulder, forcing the sleeve to expand into a wall of a bone hole
Implementation Method 2
The sleeve further has a plurality of axial slits in communication with the internal channel of the sleeve and defining a plurality of flexible wall sections
Data Source
AI summary
A bone anchor having a rivet having a proximal end and a head distal to an elongate body, a sleeve having an internal channel for slidably receiving the body, and an expansion nut having a channel therethrough for slidably receiving said body, proximal of said sleeve is provided. The sleeve further has a shoulder provided within the internal channel in the region of the proximal end for engaging the expansion nut. The rivet, sleeve and expansion nut are arranged such that movement of the rivet from a first position to a second position causes the sleeve to cam over the rivet head and expansion nut until said expansion nut engages said shoulder, forcing the sleeve to expand into a wall of a bone hole.