Tibial Trial Insert Spacing Adjustment Mechanism
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Solution Overview
Problem
Current tibial trial insert systems for knee arthroplasty face challenges in accurately adjusting the relative spacing between the femoral and tibial components, leading to potential errors during surgery and compromising patient safety due to loose or non-pre-assembled parts.
Innovation Solution
A tibial trial insert system with a spacing adjustment assembly featuring a telescopic mechanism and shims, where the connector and base elements are movably and captively coupled, allowing limited proximal/distal movement, and shims with specific thicknesses and matching portions to prevent incorrect adjustments, ensuring precise positioning and preventing excessive shim insertion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a spacing adjustment assembly with movable connector and base elements is used, then the ease of operation is improved, but the device complexity increases
Solution Approach 1:
The spacing adjustment assembly is divided into separate connector element and base element components that can be movably coupled. This segmentation allows the elements to be handled independently during surgery while maintaining the ability to form a unified structure when assembled, thereby improving ease of operation without requiring the entire assembly to be manipulated as a single complex unit.
Solution Approach 2:
The coupling arrangement employs a nested structure where the connector element and base element interlock through complementary geometric features. One element is partially inserted into or coupled with the other, creating a compact yet movable joint that simplifies handling during surgery while maintaining structural integrity.
2Manufacturing precision
If the connector element and base element are movably coupled with limited movement, then the manufacturing precision is improved, but the device complexity increases
Solution Approach 1:
The coupling arrangement is designed to provide dynamic, limited movement in the proximal/distal direction while maintaining fixed positioning in other directions. This controlled mobility allows for precise spacing adjustment during surgery by permitting only the necessary degree of freedom, thereby improving manufacturing precision without requiring overly complex constraints in all directions.
Solution Approach 2:
The coupling arrangement provides different degrees of freedom in different directions: it allows limited movement in the proximal/distal direction for adjustment purposes while constraining movement in anterior/posterior and medial/lateral directions. This anisotropic constraint strategy achieves precise spacing control without requiring complex mechanisms in all spatial dimensions.
3Measurement precision
If shims are made slidable with specific thicknesses and matching portions, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The shims are designed with specific, discrete thickness parameters and complementary matching portions that enable precise control of proximal/distal height adjustments. By varying the thickness parameter across different shim variants and incorporating matching geometric features, the system achieves measurement precision through selective combination of standardized components rather than through complex adjustment mechanisms.
Solution Approach 2:
The shims incorporate asymmetric matching portions with specific geometric features that prevent incorrect pairing or stacking sequences. These asymmetric features ensure that shims can only be assembled in the correct order and orientation, thereby guaranteeing measurement precision while using simple, standardized shim components rather than complex adjustment devices.
4Reliability
If the coupling arrangement limits proximal/distal movement, then the reliability is improved, but the ease of operation worsens
Solution Approach 1:
The coupling arrangement incorporates built-in mechanical stops or geometric constraints that prevent excessive proximal/distal movement before it can occur. By designing the coupling interfaces with predetermined travel limits, the system proactively prevents incorrect assembly or over-insertion of shims, thereby improving reliability without requiring complex active control mechanisms that would complicate surgical handling.
Data Source
Figure 1
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AI summary
Tibial trial insert system (1), comprising: a bearing component (100) having a superior articulating (101) surface and an inferior surface (102); a plate component (200) having a superior surface (201) and an inferior fixation surface (202); a spacing adjustment assembly (300) configured to be arrangeable between the inferior surface of the bearing component and the superior surface of the plate component, the spacing adjustment assembly having at least one superior connector (301) element configured to removably engage with the bearing component, at least one inferior base element (302) configured to removably engage with the plate component, and having a coupling arrangement (303, 304, 305,306) movably coupling the connector element with the base element in proximal/distal direction and to a limited extent; a plurality of shims (500, 500', 600, 700, 720, 740), each shim configured to be slidable between an inferior surface of the connector element and a superior surface of the base element to adjust a proximal/distal height of the spacing adjustment assembly, in order to thereby adjust a relative proximal/distal spacing between the bearing component and the plate component.