Acetabular Bearing Removal Tool for Modular Hip Joint Revision
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Solution Overview
Problem
There is a need for an efficient system to remove a modular acetabular bearing from an acetabular cup without requiring the removal of the cup itself, facilitating revision surgery or addressing bearing surface wear in hip replacement systems.
Innovation Solution
A system comprising an acetabular cup with a ramped slot and a ring with radially extending fingers, which can be unlocked and spread by a removal tool to allow the bearing to be levered away from the cup, utilizing complementary interlocking portions to inhibit rotation and ensure secure engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a modular acetabular bearing is locked to the acetabular cup using a ring with fingers in slots, then the bearing is securely retained and rotation is inhibited, but the bearing cannot be removed without removing the entire acetabular cup
Solution Approach 1:
The removal tool is designed with segmented functional zones: a ring engaging portion with ramped surfaces that interface with the ring fingers, and a bearing engaging portion with a lever arm. This segmentation allows the tool to sequentially perform different functions (spreading the ring, then levering the bearing) without requiring removal of the acetabular cup, thereby resolving the contradiction between secure retention and ease of repair
Solution Approach 2:
The removal tool acts as an intermediary device between the surgeon and the locked bearing-cup assembly. It mediates the removal process by first engaging the ring fingers through the slots, spreading them radially outward using ramped surfaces, and then using the lever arm to pry the bearing away from the cup, enabling bearing removal while preserving the cup
2Reliability
If the ring fingers are tightly engaged in the cup slots to prevent bearing movement, then the bearing is securely locked, but the ring cannot be spread to unlock the bearing
Solution Approach 1:
The removal tool is designed with preliminary engagement features where the ring engaging portion first locates and engages the ring fingers within the slots before any spreading action occurs. The ramped surfaces are positioned to initially contact the fingers at a point that allows gradual spreading, reducing the force required and enabling controlled unlocking while maintaining secure locking during normal operation
Solution Approach 2:
The ring fingers are designed to be dynamically responsive: they maintain a tight locked position during normal bearing retention, but can be radially spread outward when force is applied through the removal tool's ramped surfaces. This dynamic behavior allows the same structure to provide both secure locking and controlled unlocking
3Ease of repair
If a removal tool is designed to engage and spread the ring fingers radially outward, then the bearing can be unlocked, but the tool structure becomes complex
Solution Approach 1:
The removal tool merges multiple functions into a single integrated instrument: the ring engaging portion with ramped surfaces combines the functions of locating the ring, engaging the fingers, and providing the spreading action. The bearing engaging portion with lever arm combines prying action and bearing extraction. This merging reduces the need for multiple separate tools while maintaining full functionality, thereby reducing overall system complexity
Solution Approach 2:
The removal tool is designed as a multi-functional device that can engage both the ring structure and the bearing structure, perform spreading actions on the ring fingers, and execute levering actions on the bearing. This universality allows a single tool to handle the complete bearing removal process, reducing the number of specialized tools needed and simplifying the surgical instrument set
4Reliability
If the bearing is tightly retained by the ring and cup interlocking portions, then rotation is inhibited and bearing position is stable, but the bearing cannot be levered away from the cup
Solution Approach 1:
The removal process follows a preliminary action sequence: first the ring is engaged and spread to unlock the bearing from the ring constraint, then the bearing engaging portion is positioned to contact the bearing, and finally the lever arm is used to pry the bearing away from the cup. This sequential preliminary action on the ring before direct bearing engagement reduces the extraction force needed and prevents damage to the bearing or cup
Data Source
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AI summary
A system for replacing a portion of a hip joint can include a cup having an outer surface and an inner surface. A bearing can include an outer bearing surface and an inner articulating surface. The outer bearing surface can be positioned adjacent to the cup. A ring can be selectively disposed between the cup and the bearing. The ring can define an annular body having a slit formed therein. A removal tool can define a proximal end and a distal end. The distal end can define a ring engaging surface and a bearing engaging surface. The ring engaging surface can be adapted to engage the ring at the slit such that the ring expands radially from a locked position away from engagement with the bearing to an unlocked position. The bearing engaging surface can be adapted to engage the bearing and urge the bearing away from the cup.