Rotatable Spine Knee Prosthesis for Wear Reduction
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Solution Overview
Problem
Current knee prostheses face challenges in replicating the natural internal and external rotation of the knee joint, particularly in deep flexion and extension, leading to wear and instability due to inadequate cam and spine surface contact and interaction.
Innovation Solution
A knee joint prosthesis design featuring a rotatable spine that extends through a tibial baseplate and insert, with a tapered distal portion to balance rotation and stability, ensuring maximum cam and spine surface contact area and minimizing wear through controlled taper angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the spine is designed with a fixed position and non-rotating structure, then vertical stability is improved, but rotational freedom and natural knee motion replication deteriorate
Solution Approach 1:
The spine is designed to rotate within a cavity of the tibial baseplate, transforming from a static fixed structure to a dynamic rotatable component. This allows the spine to adapt to internal/external rotation of the femoral component while maintaining vertical stability through gravitational and contact forces, thereby resolving the contradiction between stability and rotational freedom
Solution Approach 2:
The taper angle of the spine is optimized to balance vertical stability and rotational freedom. A specific taper angle range provides sufficient friction to prevent excessive rotation while allowing natural knee motion, and ensures proper seating of the spine in the cavity to maintain vertical stability
2Device complexity
If the cam and spine surface contact area is minimized, then device complexity is reduced, but wear and instability increase
Solution Approach 1:
The spine features a tapered conical shape with curved surfaces that contact the cam. This curved geometry naturally increases the contact area between cam and spine compared to flat surfaces, distributing contact pressures and reducing wear while maintaining a relatively simple overall structure
3Adaptability or versatility
If the taper angle of the spine is increased, then rotational freedom is improved, but vertical stability deteriorates
Solution Approach 1:
The taper angle of the spine is optimized to balance vertical stability and rotational freedom. A specific taper angle range provides sufficient friction to prevent excessive rotation while allowing natural knee motion, and ensures proper seating of the spine in the cavity to maintain vertical stability
Data Source
AI summary
A knee joint prosthesis is disclosed. The knee joint prosthesis can include a tibial baseplate, a tibial insert, and a spine. The tibial baseplate can include a tibial plateau, having a proximal surface and an opposing distal surface, and a tibial stem extending from the distal surface of the tibial plateau. The tibial insert can be located on the proximal surface of the tibial plateau and can include an aperture. The spine can extend through the aperture of the tibial insert and into a cavity of the tibial stem, from the proximal surface of the tibial plateau. The spine can be rotatable with respect to the tibial baseplate and the tibial insert. The knee joint prosthesis can further include a femoral component including a posteriorly-located femoral cam. The posteriorly-located femoral cam can engage the spine during movement of the knee joint prosthesis.