Bone Anchor Inner Chamber for Bicortical Spinal Fixation
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Solution Overview
Problem
Existing bone anchors for spinal deformity correction often fail to achieve adequate fixation due to inadequate purchase in cancellous bone, leading to undesirable movement and recurrence of spinal deformities, and existing designs that penetrate the distal cortical wall pose risks.
Innovation Solution
The development of bone anchors with an inner chamber and opposing thread forms that compact cancellous bone, creating a compressed region for enhanced fixation, allowing bicortical purchase without penetrating the distal cortical wall, and utilizing a tether or ligament to apply corrective forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If existing bone anchors are designed to extend entirely through the vertebral bodies to provide bicortical purchase, then fixation strength is improved, but the risk of penetrating the distal cortical wall and causing damage increases
Solution Approach 1:
The inner chamber is prepared in advance during manufacturing to receive and compact bone material. This preliminary preparation allows the anchor to create a compressed bone region that provides bicortical purchase functionality without requiring the anchor to physically penetrate through the entire vertebral body, thus avoiding cortical wall damage while maintaining fixation strength.
Solution Approach 2:
The inner chamber acts as an intermediary structure that receives compacted bone material to create a functional bicortical purchase region. This intermediary bone compacted within the inner chamber provides the necessary fixation strength without requiring direct penetration of the distal cortical wall, thereby resolving the contradiction between strength and safety.
2Object-affected harmful factors
If bone anchors rely solely on cancellous bone purchase, then the risk of cortical wall penetration is reduced, but fixation strength and stability decrease leading to anchor movement
Solution Approach 1:
The inner chamber is pre-configured to receive and compact bone material during anchor insertion. This preliminary action creates a dense, compressed bone region that significantly enhances fixation strength beyond what cancellous bone alone can provide, while the anchor still stops before penetrating the distal cortical wall.
Solution Approach 2:
The bone material within the inner chamber undergoes parameter changes through compaction, transforming from loose cancellous bone to a dense, compressed bone structure. This parameter change in bone density and compactness within the inner chamber provides enhanced fixation strength equivalent to or exceeding traditional bicortical purchase, while avoiding cortical wall penetration.
3Strength
If the anchor length is increased to achieve bicortical purchase, then fixation strength is improved, but the complexity of the device and surgical procedure increases
Solution Approach 1:
The inner chamber is pre-formed during manufacturing with the capability to receive and compact bone material. This preliminary preparation allows a shorter anchor to achieve the fixation strength of a longer anchor, as the compacted bone within the inner chamber provides the necessary purchase without requiring the anchor to extend through the entire vertebral body.
Solution Approach 2:
Instead of increasing anchor length in the longitudinal dimension to achieve bicortical purchase, the invention utilizes the inner chamber dimension to compact bone material and create a functional purchase region. This dimensional approach allows achieving the same fixation strength with a shorter anchor, reducing device complexity and surgical difficulty.
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 solution provides increased fixation strength and stability, reducing the risk of anchor dislodgment and enhancing the efficacy of spinal correction by achieving functional bicortical purchase without penetrating the cortical wall, thereby stabilizing the spinal column effectively.
Implementation Method 1
compact the cancellous bone to form a compressed bone region. The compressed bone region may be advanced distally of the bone anchor by advancing the bone anchor within the bone
Implementation Method 2
providing, in some embodiments, an inner chamber that is threaded, which may provide a number of benefits, such as drawing additional bone into the chamber, placing such bone under compression to accelerate healing and incorporation with the implant
Data Source
AI summary
Methods, devices, and systems for spinal deformity correction. In some embodiments, a bone anchor may comprise an outer thread form, an inner chamber, and a non-threaded introducer tip. The introducer tip may comprise a cylindrical shape comprising a distal edge configured to facilitate penetration into the first vertebral body. The distal edge may have a larger width than an adjacent section of the first bone anchor proximal to the distal edge. In some embodiments, a removable cap may be provided. In some embodiments, the bone anchor may comprise a tether seat having distinct regions each configured to receive a distinct tether.