Dual tether support of vertebra
Inventors
Hoernschemeyer, Daniel Gerard • Prygoski, Matthew • Detlefsen, Rick • Tozakoglou, Evangelos
Assignees
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Publication Number
US-12082849-B2
Publication Date
2024-09-10
Expiration Date
Abstract
An apparatus includes a first flexible connector and a second flexible connector. The apparatus also includes a first bone anchor including a first tethering head configured to receive a first portion of the first flexible connector. The apparatus also includes a second bone anchor including a second tethering head configured to receive a second portion of the first flexible connector. The apparatus also includes a third bone anchor defining a first aperture configured to receive therethrough the first bone anchor. The third bone anchor also defines a first peripheral channel configured to receive a first portion of the second flexible connector. The apparatus also includes a fourth bone anchor defining a second aperture configured to receive therethrough the second bone anchor. The fourth bone anchor also defines a second peripheral channel configured to receive a second portion of the second flexible connector.
Core Innovation
The invention provides an apparatus for coupling a first bone portion to a second bone portion using a first flexible connector and a second flexible connector routed through separate bone anchors. A first bone anchor includes a first tethering head configured to receive a first portion of the first flexible connector, and a second bone anchor includes a second tethering head configured to receive a second portion of the first flexible connector.
The apparatus also defines a third bone anchor with a first aperture and a first peripheral channel configured to receive a first portion of the second flexible connector, and a fourth bone anchor with a second aperture and a second peripheral channel configured to receive a second portion of the second flexible connector. The routing across tethering heads and peripheral channels implements load sharing across multiple attachment points.
In disclosed embodiments, the tether pathways and mechanical behavior of the flexible connectors are configurable to provide axial strength and stiffness without increasing anchor profile by using load sharing across two tether attachment points. The disclosure further describes staged load engagement using tethers having different stiffness, elasticity, and initial tension, redundancy if one tether fails, growth modulation staging or reset after tether fracture by leaving one tether slack, and moment generation in one or multiple planes using aligned versus offset or tangential tether paths or anchors accepting two side-by-side cords.
Claims Coverage
The independent claim specifies an apparatus for coupling two bone portions using two flexible connectors routed through four bone anchors, with each connector portion received by a corresponding tethering head or peripheral channel. The inventive features center on dual flexible connector routing, tethering heads for one connector, and peripheral channels through apertured anchors for a second connector.
Dual flexible connector coupling with tethering heads and peripheral channels
An apparatus including a first flexible connector and a second flexible connector, where a first bone anchor with a first tethering head receives a first portion of the first flexible connector and a second bone anchor with a second tethering head receives a second portion of the first flexible connector, and where a third bone anchor defines a first aperture and a first peripheral channel configured to receive a first portion of the second flexible connector, and a fourth bone anchor defines a second aperture and a second peripheral channel configured to receive a second portion of the second flexible connector.
Different ultimate tensile strength between flexible connectors
The apparatus is further configured such that the first flexible connector and the second flexible connector have different ultimate tensile strengths, with the second ultimate tensile strength being significantly less than the first.
Different substantially uniform cross-sectional areas for flexible connectors
The apparatus is further configured such that the first flexible connector and the second flexible connector each have a substantially uniform cross-sectional area, and the second substantially uniform cross-sectional area is significantly less than the first substantially uniform cross-sectional area.
Substantially inelastic versus substantially elastic connector behavior
The apparatus is further configured such that one of the first flexible connector and the second flexible connector is configured to be substantially inelastic and the other is configured to be substantially elastic.
Rotatable tethering head on a threaded shank
The apparatus further configured such that the first bone anchor has a threaded shank and the first tethering head rotatably couples to and can be rotated relative to the threaded shank about the shank’s longitudinal axis.
Eyelet in a peripheral channel
The apparatus further defined such that the first peripheral channel includes an eyelet.
Overall, the claims coverage centers on an apparatus that couples two bone portions using dual flexible connectors routed through bone anchors with tethering heads for one connector and peripheral channels through apertures for the other. Dependent features further narrow the mechanical characteristics of the flexible connectors and refine bone-anchor hardware with rotatable tethering heads on threaded shanks and peripheral channels including an eyelet.
Stated Advantages
Increased axial strength and stiffness without increasing anchor profile via load sharing across two tether attachment points.
Staged load engagement using tethers of different stiffness, elasticity, and initial tension.
Redundancy if one tether fails.
Growth modulation staging or reset after tether fracture by leaving one tether slack.
Moment generation in one or multiple planes using aligned versus offset or tangential tether paths or anchors accepting two side-by-side cords.
Documented Applications
Coupling a first bone portion to a second bone portion using a dual-tether or dual flexible connector vertebral coupling apparatus.
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