Talar Implant with Offset Radii for Joint Tension Restoration
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Solution Overview
Problem
Post-traumatic osteoarthritis in the ankle joint leads to malalignment, asymmetric loading, and cartilage degeneration, resulting in altered joint kinematics and functional loss due to inadequate restoration of joint tension and articular surface reconstruction in existing implants.
Innovation Solution
A talar implant with a superior surface defined by a smaller arc radius and an inferior surface defined by a larger arc radius, configured to restore joint tension in the neutral position, with varying radii and offsets to accommodate natural joint motion, preserving talar bone stock and providing support through an anterior extension, and optionally including a peg for anchoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing implants are used to replace the talar dome, then joint function is restored, but joint tension is not adequately restored and joint kinematics remain altered
Solution Approach 1:
The implant design changes the geometric parameters of the articular surface by using different radii of curvature for the superior and inferior surfaces. The superior surface has a smaller radius of curvature to restore the dome shape, while the inferior surface has a larger radius to maintain bone stock, creating the necessary offset to restore joint tension and kinematics
2Ease of manufacture
If the articular surface is reconstructed with a uniform thickness implant, then manufacturing is simplified, but joint tension and kinematics cannot be restored
Solution Approach 1:
The implant design applies local quality by varying the thickness distribution across the implant body. The superior surface is shaped with a smaller radius of curvature to restore the dome, while the inferior surface uses a larger radius to preserve bone. This localized variation in geometry creates the necessary joint tension restoration without complicating manufacturing
Solution Approach 2:
The design changes the geometric parameters by defining the superior surface with radius R1 and the inferior surface with radius R2, where R1 < R2. This parameter variation creates the offset between the centers of curvature, which is essential for restoring joint tension while maintaining manufacturability through standard casting or machining processes
3Stability of the object's composition
If bone stock is removed to accommodate a standard implant, then implant fit is improved, but talar bone integrity is compromised
Solution Approach 1:
The implant design changes the radius parameter of the inferior surface to be larger than that of the superior surface. This creates an offset between the centers of curvature that allows the implant to fit the deformed talar dome while preserving the remaining bone stock, as the larger inferior radius accommodates the bone that would otherwise need to be removed
4Ease of manufacture
If the implant uses the same radius of curvature for both superior and inferior surfaces, then manufacturing is easier, but the center of rotation cannot be offset to restore joint tension
Solution Approach 1:
The design explicitly changes the radius parameters of the two surfaces: the superior surface uses radius R1 and the inferior surface uses radius R2, with R1 < R2. This parameter differentiation automatically creates the offset between centers of curvature when the implant is manufactured, restoring joint tension without requiring additional offset mechanisms or complicating the fabrication process
Data Source
AI summary
A talar implant, comprising: a superior surface, defined by an arc having at least one first radius; an inferior surface, defined by an arc having at least one second radius, a lateral side; a medial side; a posterior portion having a first width; and an anterior portion having a second width; wherein the implant is configured to restore a tibio-talar joint tension, wherein the superior surface is separated from the inferior surface by a thickness, wherein the at least one first radius is smaller than the at least one second radius, wherein the center of the arc having at least one first radius is offset from the center of the arc having at least one second radius in at least one plane of the talar implant, and wherein the anterior portion further comprises an extension configured to provide support.