Stemless Prosthesis Anchor With Locking Arm Fixation
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Solution Overview
Problem
Conventional stemless humeral components face challenges in initial dislodgement resistance due to lack of bone ingrowth, which can lead to instability and complications during and after surgery.
Innovation Solution
A stemless prosthesis assembly featuring a base member with a helical structure and a locking device that includes a proximal support and a first arm, which is configured to be disposed in a pathway through the helical structure to enhance initial pull-out and back-out resistance, providing secure fixation to the humerus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a stemless humeral component is used to preserve bone and simplify the procedure, then bone loss is decreased and procedural complexity is reduced, but initial dislodgement resistance is compromised due to lack of bone ingrowth
Solution Approach 1:
The patent applies preliminary action by incorporating a locking device with arms that engage bone tissue before bone ingrowth occurs. The locking arms are positioned within pathways in the base member to mechanically secure the prosthesis to the humerus in the early postoperative period, preventing dislodgement before biological fixation is established.
Solution Approach 2:
The locking device serves as an intermediary mechanism between the base member and the bone. The locking arms mediate the connection by engaging the bone through pathways in the base member, providing temporary mechanical support until bone ingrowth occurs, after which the locking device can be removed.
2Reliability
If conventional stem components are used with medullary canal insertion, then initial mechanical stability is achieved, but bone removal is required and removal of the component becomes difficult due to bone ingrowth
Solution Approach 1:
The patent applies segmentation by dividing the fixation function into two separate mechanisms: a base member with pathways that allows minimal bone preparation, and a separate locking device that provides mechanical stability. This segmentation eliminates the need for extensive medullary canal preparation while maintaining initial stability.
3Reliability
If a locking device with multiple arms is used to enhance initial fixation, then dislodgement resistance is improved, but device complexity increases
Solution Approach 1:
The patent applies the taking out principle by extracting the locking device as a separate, removable component from the base member. The locking device with its multiple arms can be independently applied and removed, simplifying the overall system while providing enhanced initial fixation. The locking arms are taken out as discrete elements that engage through pathways in the base member.
Data Source
AI summary
A shoulder assembly is provided which includes a base member including a collar; a helical structure extending from the collar in a distal direction; and a first pathway projecting distally of the collar and through the helical structure adjacent to an inner periphery thereof, the first pathway being generally transverse to the helical structure and extending in a space between successive portions of the helical structure; and a locking device comprising a proximal support and a first arm projecting distally of the proximal support, the first arm configured to be disposed in the first pathway projecting distally of the collar when the proximal support is disposed adjacent to the collar; where the first arm is disposed through bone in the space between successive portions of the helical structure when the shoulder assembly is implanted.