Ankle Prosthesis with Talocalcaneal Stem for Stress Distribution
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Solution Overview
Problem
Conventional ankle replacement prosthetics face issues with loosening of components from bone surfaces, limited movement, and increased stress levels due to high impact on the talus, leading to potential failure and the need for surgical correction or fusion, which can exacerbate subtalar disease and pain.
Innovation Solution
The method involves attaching a tibial component to the tibia and a talocalcaneal component to a fused talus and calcaneus with a stem through a slot, allowing for controlled motion and stress distribution, using a conical hub and spherical contact surfaces to absorb stress and facilitate normal anatomical movement, while preventing inversion/eversion rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ankle replacement prosthesis components are attached to bone surfaces, then the prosthesis provides foot movement and normal gait, but the components loosen from the bone surfaces over time leading to failure
Solution Approach 1:
The prosthesis is divided into separate modular components (tibial component, talus component, calcaneus component) that can be independently attached to different bone surfaces. This segmentation allows each component to be optimized for its specific attachment site and load distribution requirements, improving overall reliability and service life.
Solution Approach 2:
The patent introduces a third dimension of attachment by extending the prosthesis structure into the calcaneus bone in addition to the traditional tibial and talar attachments. This multi-dimensional attachment strategy distributes loads across multiple bone interfaces, preventing component loosening and extending prosthesis durability.
2Ease of operation
If conventional prosthesis design limits movement between components, then component stability is maintained, but patient mobility and normal anatomical movement are restricted
Solution Approach 1:
The prosthesis incorporates dynamic movement capabilities between components, allowing physiological ranges of motion in dorsiflexion, plantarflexion, inversion, and eversion. The modular design with articulated surfaces enables controlled movement while maintaining stability through precise mechanical constraints and bone attachment points.
Solution Approach 2:
The patent varies movement parameters by allowing different degrees of freedom for different components. The talus component permits inversion/eversion movement relative to the tibial component, while the calcaneus component provides additional movement capacity, collectively restoring normal anatomical motion patterns without compromising stability.
3Strength
If conventional prosthesis concentrates stress on the talus, then structural support is provided, but high stress levels weaken the bone and expedite failure
Solution Approach 1:
The load-bearing function is segmented across multiple components and attachment sites. The tibial component, talus component, and calcaneus component each bear portions of the structural load, distributing stress away from concentration on the talus alone and preventing bone weakening.
Solution Approach 2:
Structural support is extended into a third dimension by anchoring the prosthesis through the calcaneus bone in addition to the tibial and talar regions. This multi-point, multi-dimensional support system distributes mechanical stresses across a larger volume of bone tissue, reducing peak stress concentrations and preventing stress-induced bone failure.
Data Source
AI summary
An ankle replacement prosthesis includes a tibial component, attached within a cavity formed in the tibia, and a talocalcaneal component, attached within a slot formed within a talocalcaneal compound, previously formed by fusing the talus and the calcaneus. Preferably, the talocalcaneal component includes a neck, to which a head, having a contact surface engaging a contact surface within the tibial component, is adjustably attached. These contact surfaces may both be spherical, with the contact surface of the talocalcaneal component being formed as a ball fitting within a socket formed by the contact surface of the tibial component, or these contact surfaces may include mating feature that limit inversion/eversion rotation of the foot, while providing for dorsal/plantar rotation thereof.