Acetabular Shell Removal Tool with Chisel Guide
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Solution Overview
Problem
Existing methods for removing an acetabular shell in hip prosthesis replacement, such as the X-PLANT tool, face challenges in precisely cutting the shell free from surrounding bone due to screw attachment, which often damages the polyethylene liner and prevents the chisel from maintaining proximity to the shell's periphery.
Innovation Solution
A fixture with a chisel guide that attaches to the acetabular shell, allowing a chisel to move along a path that substantially circumscribes the outer surface, using an anchor, centering plate, locking plate, and chisel guide to maintain precision and prevent damage to the liner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the X-PLANT tool is used with a ball pivoting in the socket to keep the chisel close to the shell periphery, then the chisel positioning is improved, but the polyethylene liner is damaged when screws need to be removed
Solution Approach 1:
The fixture is attached to the acetabular shell before the chisel cutting operation begins. This preliminary attachment establishes a stable reference framework that maintains chisel positioning precision throughout the entire removal process, eliminating the need to damage the liner for screw removal.
Solution Approach 2:
The fixture acts as an intermediary component between the chisel and the acetabular shell. It provides a stable mounting structure with a chisel guide that maintains precise positioning without requiring damage to the polyethylene liner, thus mediating between the cutting operation and the protected liner.
2Ease of operation
If hand-held curved chisels and mallet are used to cut and pry the shell away, then the removal process is simple, but excess bone is removed with the shell
Solution Approach 1:
The chisel guide serves as an intermediary that directs the chisel blade along the precise periphery of the acetabular shell. This guide structure maintains cutting precision while the overall fixture system remains relatively simple to operate with a mallet.
Solution Approach 2:
The invention replaces the traditional hand-held chisel operation with a fixture-mounted chisel system. This substitution provides mechanical guidance through the chisel guide, improving precision while maintaining the simplicity of mallet-based operation.
3Ease of operation
If screws are removed from the shell before chisel cutting, then the shell can be removed, but the liner mechanism is damaged and the liner moves
Solution Approach 1:
The fixture is attached to the shell before any cutting operation begins, establishing a stable reference framework. This preliminary action ensures the liner remains stable and protected throughout the entire process, eliminating the need to remove screws that would damage the liner mechanism.
Solution Approach 2:
The fixture serves as an intermediary structure that enables shell removal without requiring screw extraction. It provides the necessary mounting and guidance functions while preserving the integrity of the polyethylene liner and its locking mechanism.
Data Source
AI summary
A tool for separating an acetabular shell of a hip prosthesis from the surrounding pelvic bone includes a fixture which attaches to the acetabular shell and has a chisel guide mounted on it. A chisel associated with the chisel guide is curved to conform to the outer periphery of the acetabular shell, and the chisel guide causes the chisel to circumscribe the acetabular shell as the chisel is inserted between the acetabular shell and the pelvis.