Stemless Humerus Implant Locking Member for Secure Fixation
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Solution Overview
Problem
Existing robotic systems lack precision and accuracy in preparing bones for shoulder arthroplasty, particularly for stemless implants, which require secure placement in the humerus without a stem.
Innovation Solution
A robotic surgery system with a robotic manipulator and cutting tool, guided by a localizer and controller, forms cavities in the humerus to receive a shoulder implant, featuring an undercut for a locking member to prevent implant withdrawal, using virtual objects for precise bone preparation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a stemless implant is used to spare bone material, then bone removal is reduced and patient benefit increases, but implant stability and security decrease due to lack of stem engagement in humeral canal
Solution Approach 1:
The implant is divided into separate functional components: a proximal body for articulation and a distal body with locking members for fixation. The locking members are further segmented into multiple discrete elements that can engage with the bone at different locations, providing distributed stability without requiring a traditional stem
Solution Approach 2:
The locking members are positioned within cavities formed in the humerus, with the distal body nesting within the bone structure. The locking members can be inserted through the distal body and engage with the bone from the interior, creating a nested configuration that secures the implant without extensive bone removal
2Extent of automation
If existing robotic systems are used for shoulder arthroplasty, then automated bone preparation is provided, but accuracy and precision are insufficient for stemless implant placement
Solution Approach 1:
The robotic system performs preliminary actions by forming cavities with precise dimensions and orientations before implant insertion. The system pre-defines the exact location, size, and shape of cavities for the distal body and locking members, ensuring that when the implant is inserted, it achieves optimal fit and stability
Solution Approach 2:
The robotic system incorporates feedback mechanisms that monitor the bone preparation process in real-time, adjusting cutting parameters and cavity formation based on actual bone density and geometry measurements, thereby achieving high precision for the complex multi-cavity structure required by stemless implants
3Reliability
If a locking mechanism is added to prevent implant withdrawal, then implant security improves, but device complexity increases
Solution Approach 1:
The locking members are designed to engage with the bone and distal body through self-service mechanisms, where the implant structure itself provides the locking action without requiring separate external locking devices. The distal body incorporates integrated locking members that automatically engage with prepared cavities in the bone, providing secure fixation as part of the implant's own structure
Solution Approach 2:
The locking function is merged with the distal body structure, combining the fixation element and the locking mechanism into a single integrated component. This reduces overall device complexity by eliminating separate locking devices while maintaining secure implant fixation through the combined structure
Data Source
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AI summary
An implant component (102) for a humerus (H) formed with an undercut portion (132) comprises a proximal body (114) having a semi-spherical head (116), and a distal body (120) configured to be secured to the proximal body (114). The distal body (120) comprises a locking member (126) extending radially outwardly from the distal body (120). The locking member (126) is rotatable about an implant axis (IA) from an unlocked position to a locked position whereby the locking member (126) is configured to engage the undercut portion (132) for limiting withdrawal of the implant component (102) from the humerus (H).