Tethering Screw Mechanism for Spinal Alignment and Pedicle Protection
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Solution Overview
Problem
Existing spinal correction devices, such as spinal rods, screws, and hooks, often cause pedicle damage and are ineffective due to wire pull-through, failing to provide safe and effective spinal alignment for each patient.
Innovation Solution
A tethering screw system comprising a bone screw with a threaded shank and head portion, an elongate fastening member, and a securing member with a set screw, allowing secure engagement and flexible alignment of vertebral bodies using a flexible fastening member and a securing mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hooks are inserted in pairs in each vertebra to provide spinal correction, then spinal alignment is improved, but pedicle damage occurs
Solution Approach 1:
The patent removes the hook component from the spinal correction system entirely, replacing it with a screw-based tethering system. This extraction eliminates the pedicle damage associated with hook insertion while maintaining the ability to achieve spinal alignment through alternative means (screws inserted into vertebral bodies with tether cords providing the correction force).
2Object-affected harmful factors
If wires are used when pedicles are small to avoid damage, then pedicle damage is reduced, but the wire is pulled through anatomy and becomes ineffective
Solution Approach 1:
The patent utilizes a cord or tether with a specific curvature or loop configuration that allows it to engage securely with the screw heads. The curved or looped shape of the tether prevents it from being pulled straight through the anatomy, while still allowing insertion through small pedicles. The tether's geometry creates mechanical interlocking that maintains effectiveness without requiring large pedicles.
3Reliability
If spinal rods and screws are used to maintain vertebral position, then spinal alignment is achieved, but the system complexity increases
Solution Approach 1:
The patent eliminates the need for spinal rods by using individual screws with tether cords that directly connect and maintain vertebral positions. This extraction of the rod component simplifies the overall system while maintaining alignment capability through the tethered screw configuration.
Solution Approach 2:
The patent divides the spinal correction function into independent screw-tether units that can be applied to individual vertebrae. Each screw with its tether cord acts as an independent corrective element, allowing modular assembly and simplifying the overall system architecture compared to a continuous rod system.
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 system provides safe and effective spinal correction by preventing pedicle damage and ensuring stable vertebral alignment through a flexible and secure fastening mechanism, adaptable to various surgical needs.
Implementation Method 1
The set screw is configured to threadably engage the inner walls of the head portion of bone screw, wherein when the set screw threadably engages the inner walls of the head portion of the bone screw, the engaging portion advances relative to the fastening member
Data Source
AI summary
A tethering screw system includes a bone screw, a fastening member, and a securing member. The bone screw includes a threaded shank and a head portion. The head portion includes inner walls defining a slot and a recess distal of the slot. The fastening member is received in the recess of the head portion of the bone screw. The securing member has an engaging portion and a set screw rotatably coupled with the engaging portion. The engaging portion is configured to secure the fastening member in the recess of the head portion. The set screw is configured to threadably engage the inner walls of the head portion of bone screw, wherein when the set screw threadably engages the inner walls of the head portion of the bone screw, the engaging portion advances relative to the fastening member to secure the fastening member in the recess of the head portion.