Expandable Pedicle Screw Anchoring in Low-Quality Bone
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Solution Overview
Problem
Low-quality cancellous bone, often found in patients with osteoporosis or other conditions, poses challenges for the stability of pedicle screws used in spinal fusion procedures, as conventional bone cement solutions can lead to extravasation and inadequate anchoring.
Innovation Solution
The development of a pedicle screw with an expandable container and temporary anchoring device, which increases the strength of the bone-screw interface by expanding and deforming fins within the cancellous bone, preventing cement extravasation and enhancing anchorage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If bone cement is used to fill the vertebral body to improve anchorage in low-quality cancellous bone, then anchorage strength is improved, but cement extravasation occurs causing harmful effects
Solution Approach 1:
The expandable container is divided into multiple segments or sections that can expand independently, allowing the bone cement to be contained in discrete compartments rather than a single large space, reducing the risk of extravasation while maintaining anchorage strength
Solution Approach 2:
The expandable container acts as an intermediary barrier between the bone cement and the surrounding bone tissue, containing the cement within defined boundaries and preventing it from extravasating into surrounding tissues while still providing effective anchorage
2Ease of manufacture
If conventional pedicle screws are used in low-quality cancellous bone, then the procedure is simple, but anchorage stability is insufficient
Solution Approach 1:
The screw incorporates an expandable container that transitions from a compact delivery state to an expanded anchored state, allowing the device to adapt to the bone cavity and provide enhanced stability while maintaining relatively simple insertion procedures
Solution Approach 2:
The expandable container changes its physical parameters (volume, shape, expansion ratio) after insertion to optimize anchorage in low-quality cancellous bone, transforming from a small delivery configuration to a larger expanded configuration that provides superior hold
3Strength
If the expandable container is expanded to increase anchorage strength, then bone-screw interface strength is improved, but device complexity increases
Solution Approach 1:
The expandable container is nested within the screw structure, with the container, neck, and temporary anchoring device forming a hierarchical nested arrangement that consolidates multiple functions into a compact integrated device, reducing overall complexity while maintaining expansion capability
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
This solution significantly enhances the anchorage strength and stability of pedicle screws in low-quality cancellous bone, preventing cement extravasation and ensuring a solid, stable anchor for spinal fusion procedures.
Implementation Method 1
expanding and deforming fins within the cancellous bone
Implementation Method 2
The expandable container may be expanded by the pressurized fluid
Data Source
AI summary
Screws for anchoring in cancellous or other low-quality bone are described. One type of screw addresses the problem of extravazation of bone cement when filling an area of low-quality bone. The screw includes an expandable container for retaining bone cement and anchoring the screw in low-quality bone. The screw also includes an anchoring device for holding the screw in place in the bone while it is supplied with bone cement or other appropriate filler. The screw further includes a head for connecting to a rod or other apparatus. A second type of screw uses an expandable container to deform two or more fins to compress cancellous bone and/or anchor in cancellous bone.