Constrained Acetabular Trialing System With Cut-Out Retention
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Solution Overview
Problem
Constrained hip implants, particularly bi-polar hip implants, require a trialing system that ensures the trial head remains locked to the trial shell during trial reduction while being easy to assemble, disassemble, manufacture, clean, and sterilize, as existing systems often face issues with dissociation and complexity in these processes.
Innovation Solution
A trialing system comprising a trial shell with a substantially spherical bearing cavity and a trial head featuring a cut-out region and orientation indicators, allowing the head to be securely retained within the shell during articulation, with a head entry portion smaller than the bearing cavity, enabling easy assembly and disassembly, and facilitating alignment and retention mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a trial head and trial shell are designed to lock together during trial reduction, then reliability is improved, but device complexity increases
Solution Approach 1:
The trial head is segmented with a cut-out region that creates a specific orientation interface with the trial shell. This segmentation allows the head to be retained in the shell during trial reduction while enabling easy assembly and disassembly through rotational alignment, resolving the contradiction between reliability and device complexity.
Solution Approach 2:
The cut-out region in the trial head creates an asymmetric interface that provides orientation-specific retention. The asymmetric design ensures the trial head locks into the trial shell in the correct orientation during trial reduction, while still allowing straightforward assembly and disassembly by aligning the asymmetric features, thus improving reliability without significantly increasing complexity.
2Measurement precision
If the bearing cavity extends beyond 180 degrees, then measurement precision is improved, but manufacturing complexity increases
Solution Approach 1:
The bearing cavity is designed with a spherical geometry that extends beyond 180 degrees. This curved, spherical design provides superior articulation verification and measurement precision while being manufacturable using standard spherical machining techniques, thus achieving high measurement precision without excessive manufacturing complexity.
3Ease of operation
If the head entry portion diameter is smaller than the bearing cavity diameter, then ease of operation is improved, but manufacturing precision requirements increase
Solution Approach 1:
The head entry portion is designed as a segmented interface with the cut-out region in the trial head. This segmentation creates a straightforward dimensional relationship where the entry portion diameter is smaller than the bearing cavity diameter, enabling easy assembly and disassembly operations while maintaining achievable manufacturing precision through standardized machining tolerances.
Data Source
AI summary
A trial head and shell for use in trial reduction of hip implants, and particularly bipolar implants, having locking features that prevent the head from dissociating from the shell during trialing, yet which allow the head and shell to be readily assembled and disassembled in the operating room. A cut-out region is formed in an outer bearing surface of the head. The cut-out region allows the head to pass through a trial shell opening and into the shell, yet is oriented such that when the head is associated with a femoral neck, the head cannot disassociate from the shell. Orientation indicators can be provided for use in assembly and disassembly. The trial head and associated shells can be provided in the form of a surgical kit including hip implants. Methods of use are provided.