Bone Plate Screw Hole Pinch Point Geometry
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Solution Overview
Problem
Existing spinal plates used in orthopedic surgeries often cause damage to surrounding bone and tissue during implantation and may not effectively prevent the backout of spinal implants, leading to instability in the spinal column.
Innovation Solution
A bone plate and plating system with a locking screw mechanism, featuring a screw hole with a counterbore and conical surface that provides a flexible, variable geometry for secure attachment to the bone, minimizing damage and preventing backout through a detented engagement mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fasteners are used to fasten the spinal plate to vertebrae, then the plate can be attached to stabilize the vertebrae, but damage is caused to the surrounding bone and tissue during implantation
Solution Approach 1:
The screw hole incorporates a counterbore with a beveled surface that creates a localized engagement zone at the pinch point. This localized geometry concentrates the securing action at a specific region (the pinch point where the beveled surface intersects the conical surface) rather than distributing it across the entire screw-bone interface, thereby minimizing damage to surrounding bone and tissue while maintaining reliable fixation.
2Reliability
If conventional fasteners are used to fasten the spinal plate, then attachment is achieved, but the spinal implant may backout leading to instability
Solution Approach 1:
The counterbore with beveled surface is designed to create a pinch point that preliminarily engages the screw before full insertion is complete. This preliminary anti-action (the pinch point engagement) prevents the screw from backing out by creating a mechanical lock that opposes the backout force, thereby maintaining spinal column stability.
Solution Approach 2:
The variable geometry of the counterbore with its beveled surface creates a dynamic engagement mechanism. The pinch point provides a flexible, variable geometry that adapts to the screw insertion process, allowing for secure attachment while preventing backout through the detented engagement between the pinch point and the screw threads.
3Reliability
If a secure locking mechanism is implemented to prevent backout, then stability is improved, but device complexity increases
Solution Approach 1:
The counterbore with beveled surface merges multiple functions into a single geometric feature. The same pinch point geometry that provides the locking mechanism to prevent backout also serves to guide screw insertion and distribute loads. This merging of functions achieves reliable backout prevention without proportionally increasing device complexity.
Data Source
AI summary
A bone plate and plating system are for use of the same are disclosed. The bone plate includes a body having a span sufficient to overlap a portion of a bone. A screw hole extends through the body in order to receive a bone screw to attach for engaging the plate to the bone. The screw hole includes a counterbore having a beveled surface that intersects at a pinch point a bore having a conical surface of revolution that transitions into the bone engaging surface of the body. The beveled surface includes a variable geometry defining interleaved and rotationally-spaced contact and non-contact bone screw regions.