Stemless Shoulder Implant Locking Undercut for Bone-Sparing 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 less bony material removal and secure placement.
Innovation Solution
A robotic surgery system with a robotic manipulator, cutting tool, and localizer, controlled by controllers to form specific cavities in the bone for receiving a stemless implant, including a first cavity for the implant body and a second cavity with an undercut for a locking member, ensuring secure implant fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a stemmed implant is used in shoulder arthroplasty, then implant stability is improved through the humeral canal, but more bony material must be removed from the patient
Solution Approach 1:
The implant is divided into two functional components: a main body for initial placement and a separate locking member for securing. The locking member extends radially outward and rotates into a second cavity to engage an undercut, providing stability without requiring a stemmed design that would necessitate removal of the humeral canal.
Solution Approach 2:
The locking mechanism transitions from axial insertion to radial engagement. The locking member rotates from an unlocked position within the first cavity to a locked position where it engages the undercut in the second cavity, creating stability through a dimensional change rather than relying on deep axial insertion into the humeral canal.
2Loss of substance
If a stemless implant is used to preserve bony material, then bone-sparing advantage is achieved, but implant stability and secure placement become more difficult
Solution Approach 1:
The system prepares two cavities before implant placement: a first cavity for receiving the implant body and locking member in an unlocked position, and a second cavity rotated relative to the first to define an undercut. This preliminary preparation enables the locking mechanism to function without requiring removal of additional bone for a stemmed implant.
Solution Approach 2:
The locking member acts as an intermediary between the implant body and the bone. It extends radially outward from the body, rotates into the second cavity, and engages the undercut to provide secure fixation, effectively mediating the connection between the stemless implant and the humerus without requiring a traditional stem.
3Adaptability or versatility
If traditional robotic systems are used for shoulder arthroplasty, then general arthroplasty capability is provided, but precision and accuracy for stemless implant placement are insufficient
Solution Approach 1:
The robotic system is configured with specific tools and parameters for creating the unique two-cavity structure required by stemless implants with locking members. The system can precisely control the formation of the first cavity for implant reception and the second rotated cavity for the undercut, providing localized precision for this specific implant type while maintaining general arthroplasty capability.
Solution Approach 2:
The robotic system adjusts its operational parameters to accommodate the specific requirements of stemless implant placement, including the angular orientation for creating the rotated second cavity and the depth control for forming the undercut. These parameter changes enable high precision for stemless implants while the system retains versatility for other arthroplasty procedures.
Data Source
AI summary
Robotic system and methods for preparing a bone of a joint to receive an implant. Virtual object(s) are used to define a volume of material to be removed from the bone for receipt of the implant. A robotic manipulator controls a cutting tool based on the virtual object(s) to form a first cavity and a second cavity in the bone. The second cavity is formed beneath the first cavity and is rotated relative to the first cavity to define an undercut in the bone. The first and second cavities receive a body and a locking member of the implant in an unlocked position. The locking member is rotated within the second cavity to a locked position whereby the undercut engages the locking member to limit withdrawal of the implant from the bone.