Tibial Insert Locking Mechanism for Revision Surgery
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Solution Overview
Problem
Existing modular tibial prostheses face challenges in easily and damage-free removal of the tibial insert from the baseplate, particularly during revision surgeries, due to the use of one-way locking mechanisms like snap mechanisms that are difficult to disengage without causing damage.
Innovation Solution
A locking mechanism comprising a locking pin, a spring, and a recessed pocket, where the pin is under spring force and extends to engage with a mating hole on the baseplate, allowing for easy removal without damaging the insert or locking mechanism, using a lead-in ramp for compression and a handheld tool to compress the pin for removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If one-way locking mechanisms like snap mechanisms with mechanical interlocks are used, then the locking strength and stability of the insert to baseplate connection is improved, but the ease of removal and risk of damage during removal deteriorates
Solution Approach 1:
The locking mechanism transitions from a static one-way lock to a dynamic two-way lock. The spring-loaded pin can be compressed by a surgical tool to release the locking engagement, allowing easy removal, and then automatically returns to its locked position when released, providing both strong locking and easy removal capabilities.
Solution Approach 2:
The spring-loaded pin can be temporarily 'discarded' from its locked position during removal operations, allowing the insert to be removed from the baseplate. After removal, the pin automatically 'recovers' its locked position when the insert is reinstalled, providing reliable locking without permanent damage.
2Reliability
If one-way locking mechanisms are used, then the locking reliability is improved, but the loss of time during removal operations and the need for new inserts increases
Solution Approach 1:
The dynamic spring-loaded mechanism allows rapid release and relocking operations. The pin can be quickly compressed with a surgical tool for removal, and automatically returns to the locked position during reinstall, significantly reducing surgical time compared to manual disengagement of one-way locks.
Solution Approach 2:
The spring-loaded pin performs self-locking and self-unlocking functions. During installation, the pin automatically engages the locking hole without manual manipulation. During removal, the pin can be easily compressed and automatically returns to its locked state, eliminating the need for complex manual disengagement procedures and reducing surgical time.
3Stability of the object's composition
If one-way locking mechanisms are used, then the connection stability is improved, but the risk of damage to the insert and locking mechanism during removal increases
Solution Approach 1:
The dynamic spring-loaded pin allows controlled compression during removal operations, preventing forced disengagement that causes damage. The pin can be temporarily released by compression and then automatically re-engage during reinstall, eliminating the risk of damage associated with forcing one-way locks open.
Solution Approach 2:
The spring mechanism provides built-in cushioning by allowing controlled compression of the pin during removal operations. This pre-designed compression path prevents sudden forcing and potential damage to the insert or locking mechanism, protecting components before damage can occur.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Facilitates quick and damage-free removal of the tibial insert from the baseplate, enhancing surgical efficiency and providing a cost benefit by allowing reuse of the insert, which is particularly advantageous in revision surgeries.
Implementation Method 1
A spring detent includes a locking pin mounted in the bore of the insert and has a curved wire spring element mounted in the bearing insert recess. The wire spring element has an end engaging the pin for biasing the pin outwardly of the bearing insert anterior side surface.
Implementation Method 2
During assembly, a lead-in ramp on the anterior surface wall of the baseplate compresses the pin. After final seating of the insert on the baseplate, the compressed pin, under the spring tension forcibly extends and engages into a mating hole on the baseplate.
Data Source
AI summary
A tibial implant includes a baseplate having a proximally facing surface surrounded at least in part by a proximally extending wall. The wall has a ramp surface extending from the wall towards the baseplate proximally facing baseplate surface and a bore located distally of the ramp. A polyethylene bearing insert is mounted on the baseplate and has a distally facing surface engaging the proximally facing surface of the baseplate. The distally facing bearing insert surface has a recess and the insert has a side surface with a passageway extending from the recess through the insert side surface. A spring detent is mounted in the bearing insert recess and has a moveable pin biased outwardly of the bearing insert side surface and into the bore of the baseplate.