Anatomically Relieved Orthopedic Augment for Tibial Stress Distribution
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Solution Overview
Problem
Orthopedic implants, particularly in the tibia, face premature failure due to torsional stress, shear forces, and unequal compressive loads, which can lead to bone resorption and interface failures, exacerbated by uneven cortical contact and stress shielding.
Innovation Solution
An anatomically shaped orthopedic augment with a varying outer portion conforming to the metaphyseal-diaphyseal junction and metaphyseal regions of the bone, featuring reliefs to prevent contact with adjacent bone walls, allowing for flexible placement and even load distribution, thereby reducing torsional stress and preventing bone interface failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a conventional cylindrical augment is used, then the manufacturing process is simple, but the augment cannot conform to the anatomical shape of the bone canal, resulting in unequal cortical contact and stress concentration
Solution Approach 1:
The augment features a non-uniform geometry where the outer portion has a first shape at the distal end and a second shape at the proximal end, with different curvature radii and cross-sectional dimensions. This local variation in geometry allows the augment to conform to the anatomical contours of the bone canal at different locations, optimizing cortical contact and stress distribution without requiring a completely complex custom-shaped component.
Solution Approach 2:
The augment employs asymmetric geometry with the outer portion having different shapes at its distal and proximal ends. The first shape at the distal end has a different curvature radius and cross-sectional area compared to the second shape at the proximal end. This asymmetry enables the augment to match the non-uniform anatomical structure of the bone canal, improving fit and load distribution while maintaining manufacturing feasibility through controlled geometric variation.
2Reliability
If the augment contacts the cortical bone walls, then fixation is enhanced, but stress shielding occurs and bone resorption is promoted
Solution Approach 1:
The augment is divided into distinct functional portions: an inner portion with a first diameter for receiving implant components, and an outer portion with a second, larger diameter for bone interface interaction. The outer portion further includes a first shape at the distal end and a second shape at the proximal end, creating segmented zones that optimize both fixation and stress distribution. This segmentation allows controlled cortical contact in specific regions while minimizing stress shielding through geometric design.
Solution Approach 2:
The augment utilizes varying geometric parameters along its length, including changing diameter, curvature radius, and cross-sectional shape. The transition from the inner portion to the outer portion, and between the first and second shapes, creates a gradient of cortical contact. This parameter variation allows the augment to maintain sufficient fixation through controlled contact while distributing stresses to prevent localized bone resorption and stress shielding.
3Manufacturing precision
If the augment is designed to fit tightly in the bone canal, then positioning precision is improved, but torsional stress and shear forces concentrate at the interface
Solution Approach 1:
The augment transitions from a simple cylindrical form to a three-dimensional anatomically contoured shape with varying cross-sections along its length. The outer portion's first and second shapes create a multi-dimensional interface that matches the bone canal's anatomy. This dimensional complexity allows precise positioning while distributing contact forces across a more extensive surface area, reducing stress concentration and improving interface durability against torsional and shear loads.
Data Source
AI summary
Anatomically shaped augments that are configured for implantation in a bone and which have one or more reliefs. A distal end of an outer portion of the augment can have a shape that is configured to generally conform to the shape of a metaphyseal-diaphyseal junction of an intramedullary canal of a bone. A proximal end of the outer portion can have a shape that is configured to generally conform to a shape of the metaphyseal region of the intramedullary canal. The reliefs can be configured to reduce a size of the augment and enhance the degree of freedom in the implant positioning and/or sizing of the augment. Further, such reliefs may contour the augment so as to prevent cortical bone contact and/or prevent contact with the implant device that may be associated with misalignment between an intramedullary canal and metaphyseal or diaphyseal regions of the bone.