Curved Tibial Insert Geometry for Bone-Conserving Knee Implants
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing orthopaedic knee prostheses require significant bone resection due to the need for a minimum thickness of the tibial insert, leading to excess bone removal and potential instability from shear forces, particularly in uni-compartmental replacements.
Innovation Solution
Uni-compartmental tibial inserts with curved articular and bottom surfaces that maintain a constant thickness, allowing for a rounded tibial tray attachment, reducing the need for planar cuts and conserving bone, and incorporating protrusions to enhance stability and resist shear forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a minimum thickness of the tibial insert is maintained, then the reliability of the prosthesis is improved, but the volume of bone removed during surgery increases
Solution Approach 1:
The tibial insert employs a curved bottom surface instead of a flat surface, allowing the insert to conform to the natural curvature of the tibial tray. This curved geometry enables the maintainance of minimum thickness requirements while reducing the overall volume of bone that must be removed to accommodate the implant, directly resolving the contradiction between reliability and bone conservation
Solution Approach 2:
The invention changes the geometric parameters of the tibial insert by implementing a non-planar, curved bottom surface profile. This parameter modification allows the insert to achieve the required minimum thickness for reliability while minimizing the resection depth needed, thereby reducing bone loss during implantation
2Ease of manufacture
If planar cuts are made in the tibia for tibial tray attachment, then the ease of manufacture is improved, but the stability of the implant against shear forces deteriorates
Solution Approach 1:
The curved bottom surface of the tibial insert complements the curved top surface of the tibial tray, creating a rounded interface that naturally resists shear forces through geometric interlocking. This curved geometry provides mechanical stability without requiring additional bone-attachment features like pegs or keels, while still allowing for relatively simple surgical implantation
3Stability of the object's composition
If additional bone-attachment features like pegs or keels are added, then the stability of the implant is improved, but the complexity of the device increases
Solution Approach 1:
The invention extracts and eliminates the need for additional bone-attachment features such as pegs or keels by utilizing the curved bottom surface geometry itself to provide sufficient stability. This simplification removes unnecessary components and reduces device complexity while maintaining adequate implant stability through the curved interface design
Data Source
AI summary
A tibial insert includes an articular surface and a bottom surface opposite the articular surface. The bottom surface includes one or more bone-conserving features. In some embodiments, the bottom surface may be curved to match a curvature of the articular surface such that a thickness of the tibial insert is relatively constant. In other embodiments, the bottom surface may be relatively planar but include a protrusion extending from a planar base surface to maintain a minimum thickness of the tibial insert. The described features may be incorporated in a uni-compartmental tibial prosthesis, a bi-compartmental tibial prosthesis, or a total knee prosthesis.