Expandable Segmented Joint Implant Fixation Posts
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Solution Overview
Problem
Conventional joint prostheses face challenges in achieving initial stability due to limitations in bone fixation methods, such as bone cement fatigue and inadequate biologic fixation, often requiring mid-surgery changes and increased risk of post-operative loosening.
Innovation Solution
The development of a joint prosthesis with hollow segmented posts that allow for initial stability through cement injection and expansion to increase the press fit within the bone, providing flexibility between biologic and cement fixation methods without altering the implant or bone preparation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If biologic fixation through porous surfaces is used, then long-term stability is improved, but initial stability is insufficient leading to potential loosening
Solution Approach 1:
The fixation post is divided into multiple segments that can expand independently, allowing the post to be inserted in a compact state and then expanded within the bone cavity to achieve both initial press-fit stability and long-term biologic fixation through bone ingrowth into the porous surfaces between segments
Solution Approach 2:
The fixation post transitions from a static inserted state to a dynamic expanded state, where the segments are forced apart to increase the diameter of the post within the bone cavity, providing adjustable initial stability while maintaining the porous surfaces for long-term biologic fixation
2Stability of the object's composition
If cement fixation is used, then initial stability is improved, but long-term reliability deteriorates due to cement fatigue and breakdown
Solution Approach 1:
The expandable post provides preliminary mechanical stability through expansion and press-fit within the bone cavity, creating a stable environment that facilitates subsequent bone ingrowth into the porous surfaces, thereby establishing both initial and long-term fixation without relying on cement
Solution Approach 2:
The physical parameters of the fixation post are changed by expanding the segments to increase diameter and create press-fit within the bone cavity, providing initial stability through mechanical expansion rather than cement, while the porous surfaces maintain their chemical and biological properties for long-term bone ingrowth
3Stability of the object's composition
If precise instruments and consistent surgical techniques are required for biologic fixation preparation, then initial stability is improved, but surgical complexity and time increase
Solution Approach 1:
The expandable post performs self-adjustment within the bone cavity, expanding to fit the available space and providing stable fixation without requiring extremely precise pre-preparation of the bone cavity, thereby reducing surgical complexity while maintaining initial stability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances initial stability and adaptability during surgery, allowing for potential reduction in surgical time and improving long-term implant stability by enabling the use of cement fixation if biologic fixation is insufficient.
Implementation Method 1
The segments can be expandable to form or increase a press fit within a bore or hole drilled in the patient's bone
Implementation Method 2
Bone cement is mixed in the operating room and injected into the preparation sites for the implants
Data Source
AI summary
Disclosed are embodiments of an improved joint prosthesis that can provide the option to improve initial stability without removing the implant or altering the preparation. Embodiments of improved joint implant components can comprise one or more expandable, hollow segmented posts. Methods of implant fixation are also disclosed. Disclosed methods can provide the opportunity for establishing initial biologic fixation (bone ingrowth), and can also provide an adjunct fixation through injecting cement down the center of the post if initial stability is not achieved or is questionable.