Tibial Insert Keel Design for Stress Distribution
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Solution Overview
Problem
Current unicompartmental knee replacement surgeries face challenges in minimizing invasive procedures and reducing stress risers in the tibia during implantation, which can lead to potential fractures.
Innovation Solution
A tibial insert with a keel design featuring a cylindrical shape, rounded distal surface, and channels for bone cement, along with a recessed platform for increased fixation and stress distribution, is used in conjunction with minimally invasive surgical methods to reduce the risk of stress risers and enhance implant stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional knee replacement surgery is performed, then the damaged joint is replaced, but the procedure is highly invasive and causes significant patient trauma
Solution Approach 1:
The tibial insert is divided into multiple functional segments: a platform portion for load distribution, a keel portion for anchoring, and channels for bone cement injection. This segmentation allows each part to perform its specific function optimally while enabling less invasive surgical implantation compared to traditional monolithic designs
Solution Approach 2:
Channels are pre-formed within the keel structure during manufacturing, allowing bone cement to be injected through these predetermined pathways during surgery. This preliminary preparation enables more controlled and less invasive implantation procedures while ensuring proper fixation
2Stability of the object's composition
If the keel is designed with sharp edges for secure fixation, then implant stability is improved, but stress risers increase leading to potential tibial fractures
Solution Approach 1:
The keel features a rounded distal end with a continuous radius of curvature connecting the first and second downwardly-extending surfaces. This curved geometry eliminates stress concentration points that would occur with sharp edges or corners, distributing mechanical stresses evenly throughout the tibial bone while maintaining secure implant fixation
Solution Approach 2:
The keel's cross-sectional geometry is modified with a continuous radius of curvature parameter, transitioning from angular shapes that create stress risers to smooth curved surfaces that distribute stresses. This parameter change maintains fixation stability while eliminating the harmful stress concentration effect
3Strength
If bone cement is injected to secure the implant, then fixation strength is improved, but air pockets may form reducing cement effectiveness
Solution Approach 1:
Channels are pre-formed within the keel structure during manufacturing, creating designated pathways for bone cement injection. These pre-formed channels guide the cement flow and facilitate air pocket evacuation, ensuring complete and effective cement bonding between the implant and tibial bone
Solution Approach 2:
The channels act as intermediary pathways that mediate between the bone cement injection source and the fixation interface. By providing controlled flow paths, the channels enable thorough cement distribution while allowing air pockets to escape, thereby ensuring reliable cement-bone-implant bonding
4Object-affected harmful factors
If a rounded keel design is used to reduce stress risers, then fracture risk is reduced, but implant anchoring strength may be compromised
Solution Approach 1:
The keel is segmented into a rounded distal end for stress distribution and an upper portion with embedded channels for anchoring. This segmentation allows the rounded geometry to reduce stress risers while the channel structure provides mechanical interlocking for strong anchoring
Solution Approach 2:
The keel combines the rounded geometric form (for stress distribution) with the channel structure (for anchoring). This composite design integrates two conflicting requirements: smooth curved surfaces to eliminate stress concentrations and internal channels to provide mechanical interlocking for secure fixation
Data Source
AI summary
A tibial insert includes a platform defining an upper bearing surface and a bottom surface. A keel of the tibial insert is coupled to the bottom surface of the platform. A surgical method for knee anthroplasty is also disclosed.