Expandable Pedicle Screw with Radial Blades for Bone Anchorage
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Solution Overview
Problem
Conventional pedicle screws face challenges in securing within the spine due to poor screw purchase, especially in osteoporotic bone, leading to increased failure rates and complications such as cement leakage and nerve injury during surgical procedures.
Innovation Solution
A pedicle screw assembly with a retractable shaft and cannulated support anchor featuring movable blades that expand radially upon retraction, providing enhanced gripping and attachment to both cortical and cancellous bone, reducing dependence on cancellous bone for stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional threaded screws are used in the spine, then the screw can be implanted in both cortical and cancellous bone, but the screw purchase is poor due to reliance on cancellous bone which is more likely to suffer bone loss
Solution Approach 1:
The screw assembly transitions from a static conventional design to a dynamic expandable design. The blades are initially retracted during insertion to minimize trauma, then expanded after positioning to maximize purchase in cortical bone, adapting the screw's configuration to the specific requirements of the implantation site and patient anatomy.
Solution Approach 2:
The invention adds a radial expansion dimension to the traditional linear screw design. By incorporating expandable blades that extend radially outward from the central shaft, the screw engages cortical bone in multiple dimensions, creating superior anchorage that is not dependent solely on the depth of insertion along the screw's longitudinal axis.
2Reliability
If cement is injected inside a cannulated screw to address poor screw purchase, then screw stability may be improved, but complications such as cement leakage into the spinal canal and nerve injury occur
Solution Approach 1:
The invention extracts and eliminates the cement injection step from the surgical procedure. Instead of relying on cement to enhance screw purchase, the design uses mechanically expandable blades that provide stable fixation through direct engagement with cortical bone, removing the source of cement-related complications entirely.
Solution Approach 2:
The expandable blades serve as an intermediary mechanism between the screw shaft and the bone. Rather than using cement as a bonding agent, the blades mechanically interlock with cortical bone structures, providing a reliable connection that avoids the hazards of cement leakage while achieving the same goal of enhanced screw stability.
3Ease of operation
If the screw shaft is located within cancellous bone to engage both cortical and cancellous bone, then the screw can achieve initial fixation, but the result is often poor screw purchase and ultimately implant failure
Solution Approach 1:
The blades are positioned in a retracted state during the insertion phase, allowing the screw to be easily implanted into the bone without excessive trauma. After the screw is properly positioned, the blades are then expanded to engage cortical bone structures, providing enhanced long-term stability. This preliminary retraction followed by expansion sequence optimizes both ease of implantation and reliability of fixation.
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 expandable design enhances screw stability and purchase, reducing the risk of screw pull-out and complications associated with cement use, while maintaining structural integrity and minimizing tissue damage.
Implementation Method 1
the blades are biased radially outwardly from a collapsed configuration to an expanded configuration upon lateral movement of the retractable shaft within the support anchor
Implementation Method 2
a retractable shaft having a distal head portion and a proximal threaded shaft, a cannulated support anchor having a proximal, threaded inner surface that is configured to mate with the threaded shaft of the retractable shaft
Implementation Method 3
The distal head portion of the retractable shaft comprises a spear having a distal point and a proximal abutment edge. The proximal abutment edge of the spear may be configured to push the blades radially outward as the spear travels or moves within the support anchor.
Data Source
AI summary
Provided herein are various expandable pedicle screw assemblies and associated surgical methods. In one exemplary embodim0ent, the methods and devices provide a pedicle screw assembly having a support anchor, a retractable shaft or screw, and one or more blades operatively connected to the retractable shaft. Expansion of the retractable shaft within the support anchor may be effective to move the blades between a collapsed configuration and an expanded configuration in which the blades are biased laterally away from the screw assembly. In some embodiments, the biasing of the blades begins along a distal end of the screw assembly and/or the amount of biasing is maximized along the distal end. The retractable shaft may help to impart structural rigidity to the assembly, preventing breakage, while the blades may help to maximize screw purchase with the surrounding bone tissue, preventing displacement and pull-out.