Pentagonal Spinal Rod Asymmetric Cross-Section
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Solution Overview
Problem
Current spinal rods have a low contact area with spinal rod holders, leading to potential loosening or breaking under loading during normal activity due to inadequate seating, which compromises spinal stabilization.
Innovation Solution
A spinal rod with a pentagonal or V-shaped cross-section that interacts with the spinal rod holder to provide positive seating, preventing rotational movement and enhancing secure retention, preferably made from biocompatible materials like PEEK with optional curvature for superior/inferior angulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a round spinal rod is used, then the spinal rod can be easily manufactured and inserted, but the contact area with the spinal rod holder is sparse leading to inadequate seating and potential loosening under loading
Solution Approach 1:
The spinal rod transitions from a round symmetric cross-section to an asymmetric V-shaped or pentagonal cross-section. This asymmetric geometry creates specific angled surfaces that mate with corresponding features in the spinal rod holder, significantly increasing the contact area and preventing rotational movement, thereby resolving the seating stability issue
2Reliability
If a round spinal rod is used, then the design is simple, but rotational movement within the holder cannot be prevented under loading during normal activity
Solution Approach 1:
The V-shaped or pentagonal cross-section introduces asymmetric geometry that naturally prevents rotational movement. The angled sides of the rod engage with corresponding angled surfaces in the holder, creating a mechanically locked configuration that secures the rod against rotation while maintaining reasonable design complexity
Solution Approach 2:
The invention adds geometric complexity in the cross-sectional dimension (from circular to V-shaped/pentagonal) to prevent rotational movement. This dimensional change creates multiple contact points and angular interfaces that constrain the rod within the holder, addressing the retention security issue without requiring additional components
Data Source
AI summary
A spine or spinal rod has a cross-section defining angled sides that cooperate with a spinal rod opening of a spinal rod holder. In one form, the spine rod has an essentially pentagonal cross-section that thus essentially defines angled sides or side surfaces that interact with the spinal rod holder opening to positively seat the spine rod into the spinal rod holder and prevent spine rod from rotation. In the pentagonal cross-section form, the spine rod has a top or posterior side/side surface, a bottom or anterior side/side surface, a first lateral side/side surface, a second lateral side/side surface, a first angled sub-lateral side/side surface and a second angled sub-lateral side/side surface. The first and second angled sub-lateral sides/side surfaces provide contact with angled sides of the spine rod holder opening. In another form, the spine rod has an essentially V-shaped cross-section that defines sides/side surfaces that interact with the spinal rod holder opening. Preferably, but not necessarily, the spine rod is formed of PEEK. Other bio-compatible materials, however, may be used.