Facet Fixation Cap with Eccentric Lobes for Stable Joint Stabilization
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Solution Overview
Problem
Current facet screw systems for joint fixation require complex and time-consuming oblique fluoroscopic techniques for proper placement, which can be cumbersome and sensitive, whereas the existing facet fixation system employs a simpler pedicle targeting trajectory using M/L and A/P fluoroscopy, reducing placement sensitivity and enhancing bone surface capture.
Innovation Solution
The facet fixation system comprises a cap with a base and a raised portion, featuring a non-circular perimeter with lobes and an aperture for receiving a fastener, allowing for stabilization of the facet joint with improved load-bearing capabilities and optional lateralization for interspinous process access, along with instrumentation like dilators, cannulas, and guides for precise implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If oblique fluoroscopic technique is used for facet screw placement, then placement precision can be achieved, but device complexity and procedure time increase
Solution Approach 1:
A guide instrument is introduced as an intermediary tool to facilitate accurate facet screw placement. The guide provides a standardized trajectory and positioning mechanism, eliminating the need for complex oblique fluoroscopic techniques while maintaining placement precision. The guide acts as a mediator between the surgeon and the bone, enabling accurate screw insertion through a simplified approach.
Solution Approach 2:
The facet joint region is segmented into specific anatomical landmarks and trajectory zones that can be accessed through standardized approaches. By dividing the complex placement task into discrete, guide-defined positions, the procedure becomes less sensitive to variations in anatomy and reduces the need for complex imaging techniques.
2Manufacturing precision
If oblique fluoroscopic technique is used for facet screw placement, then placement precision can be achieved, but loss of time increases
Solution Approach 1:
The guide instrument is designed with pre-defined trajectories and positioning features that have been optimized in advance. This preliminary design work allows for rapid, accurate placement without requiring time-consuming fluoroscopic adjustments during the procedure. The guide encapsulates complex positioning logic that would otherwise require multiple imaging attempts.
3Strength
If cap geometry is designed for increased bone surface capture, then fixation strength improves, but device complexity increases
Solution Approach 1:
The cap geometry features an asymmetric design with a larger lateral dimension than anterior-posterior dimension. This asymmetric shape is optimized to match the anatomical orientation of the facet joint and maximize bone surface contact in the most critical loading direction. The asymmetry provides enhanced fixation strength without requiring complex multi-directional features.
Solution Approach 2:
The cap surface features localized engagement elements or surface characteristics in specific regions that maximize bone contact and fixation strength where it is most needed. Rather than uniformly complex geometry throughout, the design concentrates geometric features at critical interfaces with the bone.
Data Source
AI summary
Facet fixation implants include a cap member with a circular base portion and an eccentric raised portion. The raised portion includes first and second lobes and is smoothly contoured to provide an unobtrusive profile when implanted. Beveled teeth project from the implant to provide fixation and compression across the facet joint. The cap member includes an offset aperture which receives a fastener. Tools, guiding instruments and methods for implantation of the implants are disclosed.