Fenestrated Bone Screw Bi-Cortical Fixation and Cement Confinement
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Solution Overview
Problem
Current spinal implant systems face challenges in providing stable fixation and preventing screw loosening and biologic agent leakage during surgical treatment of spinal disorders, particularly in degenerative conditions and curvature abnormalities.
Innovation Solution
A bi-cortical fenestrated bone screw with a cannulated shaft and distal tip, featuring fenestrations to facilitate cortical purchase and reduce the risk of screw loosening, while a cannulated portion along the shaft prevents leakage of bone cement outside the vertebral body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid distal tip is used in the bone fastener, then cortical purchase is improved and screw loosening is reduced, but biologic agent leakage outside the vertebral body occurs
Solution Approach 1:
The distal tip is segmented into a solid proximal portion and a porous distal portion. The solid proximal portion provides stable cortical purchase, while the porous distal portion allows biologic agent delivery to the vertebral body without leakage outside. This segmentation resolves the contradiction by separating the fixation function from the drug delivery function.
Solution Approach 2:
Different regions of the distal tip have different properties: the proximal portion is solid for mechanical anchoring, while the distal portion is porous for controlled biologic agent release. This local differentiation allows each region to perform its specific function optimally without compromising the other.
2Reliability
If fenestrations are added to the bone fastener, then cortical purchase is enhanced and screw loosening is reduced, but device complexity increases
Solution Approach 1:
The shaft is divided into fenestrated and non-fenestrated segments. The fenestrated segment provides enhanced cortical purchase through the openings, while the non-fenestrated segments maintain structural integrity. This segmented approach enhances fixation without requiring the entire shaft to be complexly structured.
3Ease of operation
If a cannulated shaft is used, then biologic agent delivery is improved, but structural strength is reduced
Solution Approach 1:
The cannulated shaft is segmented with both fenestrated and non-fenestrated portions. The non-fenestrated segments provide structural reinforcement, while the fenestrated segments allow biologic agent delivery. This segmentation maintains overall shaft strength while enabling effective drug delivery.
Solution Approach 2:
Different portions of the shaft have different structural qualities: some areas are cannulated for drug delivery, while others are solid for strength. This local differentiation allows the shaft to simultaneously provide both functions without compromising overall structural integrity.
Data Source
AI summary
A bone fastener includes a distal member having a proximal portion and a closed distal tip. The distal member includes an outer surface engageable with a first cortical surface and a second cortical surface. The proximal portion includes an inner surface that defines a longitudinal cavity and at least one fenestration in communication therewith. Systems, spinal constructs, surgical instruments and methods are disclosed.