Three-dimensional lattice structures for implants
Inventors
Laine, Christopher • Helmar, Ian • Diehl, Lucas • Tinley, Jason • Chappuis, Kevin D. • Sullivan, John F.
Assignees
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Publication Number
US-11806240-B2
Publication Date
2023-11-07
Expiration Date
Abstract
The three-dimensional lattice structures disclosed herein have applications including use in medical implants. Some examples of the lattice structure are structural in that they can be used to provide structural support or mechanical spacing. In some examples, the lattice can be configured as a scaffold to support bone or tissue growth. Some examples can use a repeating modified rhombic dodecahedron or radial dodeca-rhombus unit cell. The lattice structures are also capable of providing a lattice structure with anisotropic properties to better suit the lattice for its intended purpose.
Core Innovation
The invention provides three-dimensional porous lattice structures for medical implants. The porous lattice structure includes a plurality of repeating unit cells, and each unit cell includes sub-unit cells defined by connected faces that enclose a volume. Within each sub-unit cell, a node is located within the volume and a plurality of struts extend from the node to define rhombic openings between the struts.
The lattice structure includes directional mechanical behavior by defining a first loading direction and a second loading direction oriented at an angle offset from the first loading direction. The porous lattice structure comprises a first elastic modulus in the first loading direction and a second elastic modulus in the second loading direction, wherein the first elastic modulus is less than the second elastic modulus. At least one rhombic opening comprises two internal angles equal to a lateral separation angle ranging between 109.5 degrees and 180 degrees.
The disclosed lattice geometry includes at least one of a rhombic dodecahedron shaped sub-unit cell and a radial dodeca-rhombus shaped sub-unit cell, implemented as repeating modified rhombic dodecahedron (MRDD) and radial dodeca-rhombus (RDDR) unit cells. The disclosure links the directional modulus differences to engineering lower elastic modulus along a loading direction than along off-axis directions, to reduce stress shielding, including by geometric tuning via elongation of unit cells along different axes and adjustment of rhombus face acute and obtuse angles and lateral separation angle.
Claims Coverage
One independent claim is identified. It defines the porous lattice architecture with repeating unit cells and rhombic openings with a constrained lateral separation angle, directional mechanical response across two offset loading directions, and at least one specified sub-unit-cell shape.
Directional porous lattice elastic modulus with offset loading directions
The porous lattice structure comprises a first loading direction and a second loading direction oriented at an angle offset from the first loading direction, and comprises a first elastic modulus in the first loading direction and a second elastic modulus in the second loading direction, wherein the first elastic modulus is less than the second elastic modulus.
Rhombic openings with lateral separation angle defined by two internal angles
At least one rhombic opening comprises two internal angles that equal a lateral separation angle ranging between 109.5 degrees and 180 degrees.
Repeating unit cells with node-and-strut rhombic openings for medical implants
The porous lattice structure for use in medical implants comprises a plurality of repeating unit cells, each unit cell comprising sub-unit cells with connected faces defining a volume, a node located within the volume, and struts extending from the node within the volume to define rhombic openings therebetween.
Rhombic dodecahedron or radial dodeca-rhombus shaped sub-unit cells
The porous lattice structure comprises at least one of a rhombic dodecahedron shaped sub-unit cell and a radial dodeca-rhombus shaped sub-unit cell.
The claim coverage centers on a porous lattice architecture that generates rhombic openings with a constrained lateral separation angle and provides anisotropic directional stiffness by enforcing a first elastic modulus lower than a second elastic modulus across two offset loading directions, implemented using rhombic dodecahedron shaped and/or radial dodeca-rhombus shaped sub-unit cells.
Stated Advantages
Reduced stress shielding by engineering directional elastic modulus in the loading direction relative to off-axis directions.
Documented Applications
Medical implants, including spinal fusion/interbody devices, where anisotropic lattice scaffolds are used to reduce stress shielding.
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