Ratchet Bone Plate Assembly for Dynamic Spinal Fusion
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Solution Overview
Problem
Existing implantable orthopedic devices often inhibit desirable loading of anatomical structures, such as bones, which can prevent ossification and healing, and lack adaptability and features to prevent unintentional backing out of fasteners.
Innovation Solution
A dynamic vertebral column construct with interconnected plate segments, springs, and cam mechanisms that allow for controlled load sharing, adjustable preload, and prevention of dynamic loading, along with features to inhibit screw backout, such as U-shaped spring rods and retention clips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rigid orthopedic devices are used to provide substantial load transfer, then structural support is improved, but bone loading and ossification are inhibited
Solution Approach 1:
The patent employs a dynamic bone plate assembly with ratchet mechanisms that allow controlled movement between plate segments. This dynamic structure enables the device to transition from a rigid load-bearing state to a more compliant state that permits physiological bone loading, thereby resolving the contradiction between providing structural support and allowing bone ossification.
Solution Approach 2:
The ratchet mechanism allows adjustment of the structural parameters of the bone plate by controlling the degree of movement between segments. This enables the device to change its mechanical properties from rigid to semi-flexible, adapting the load transfer characteristics to promote bone healing while maintaining necessary structural support.
2Ease of manufacture
If fixed bone plate configuration is used, then manufacturing simplicity is improved, but adaptability to various anatomical situations is reduced
Solution Approach 1:
The bone plate is divided into multiple segments connected by ratchet mechanisms, allowing independent adjustment of each segment's position. This segmentation enables the device to adapt to various anatomical configurations and patient-specific requirements while maintaining a relatively simple manufacturing process for each individual component.
Solution Approach 2:
The adjustable ratchet mechanism transforms a static, fixed configuration into a dynamic, adaptable structure. The plate can be configured in multiple positions post-implantation to suit different anatomical situations, providing versatility without requiring complex custom manufacturing for each case.
3Ease of operation
If standard bone screws are used, then ease of installation is improved, but prevention of unintentional backing out is insufficient
Solution Approach 1:
A ratchet mechanism serves as an intermediary component between the bone plate and the bone screws. This intermediary structure provides a mechanical locking action that prevents screw backout while maintaining the simplicity of screw installation, thereby resolving the contradiction between ease of operation and reliability.
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
Enhances spinal fusion by providing controlled load sharing and adaptability, promoting bone healing while preventing screw backout, and allowing for selective dynamic or static configurations to suit various anatomical situations.
Implementation Method 1
a spring connected between adjacent plate segments... adapted and configured to provide a predetermined preload between the first and second plate segments
Implementation Method 2
A cam can be provided on one of the first and second plate segments, and be moveable between engagement with cam surface in connection with the other of the first and second plate segments
Implementation Method 3
at least first and second plate segments adapted and configured for movement relative to one another from a spaced apart position and an approximated position, and ratchet means for allowing the first and second plate segments to move from the approximated position while preventing the first and second plate segments from moving toward a spaced apart position
Data Source
AI summary
A bone plate assembly is disclosed which includes at least one plate segment having at least one aperture extending therethrough for receiving a head portion of a bone screw, and a structure supported by the plate segment and intersecting the aperture for retaining the head portion of the bone screw with respect to the plate segment.