External bone fixation struts and systems

Inventors

Mullaney, Michael

Assignees

Arthrex Inc

Abstract

The present application provides external bone fixation systems. The systems include one or more pairs of bone fixation platforms in the form of rings or partial rings. The platforms may be coupled to corresponding bone segments. The pair of platforms are configured to accept a plurality of struts extending therebetween. The struts are configured to attach to the platforms via joints that provide three degrees of rotation. The struts are also configured such that their longitudinal length extending between the joints/platforms can be incrementally adjusted while attached to the platforms. The struts are further configured such that their total range of length adjustment can be increased by coupling at least one add-on component to the struts in situ. The lengths of each of the plurality of struts may be adjusted to arrange the platforms, and thereby the bone segment coupled thereto, in particular relative positions and orientations.

Core Innovation

The described invention is an external fixation system that uses an external, length-adjustable strut assembly to movably couple a first external fixation platform to a second external fixation platform. The system is described as a hexapod-like 6DOF arrangement where multiple length-adjustable strut assemblies are connected between ring or partial ring platforms. Each strut assembly includes a strut body with an internal cavity and joints at opposite axial ends to couple the components to the two platforms.

The strut assembly includes a threaded key that provides an internal thread of the strut body and a threaded rod assembly translatably received within the strut body. The threaded rod assembly includes an external thread configured to engage the internal thread and axially extends within the internal cavity toward a second joint. An outer sleeve received about the threaded key enables the axial length between the first axial end portion of the strut body and the second axial end portion of the threaded rod assembly to be adjustable via rotation of the outer sleeve.

In additional embodiments, the threaded key is implemented as first and second threaded keys received within first and second openings of the strut body, and the threaded rod assembly includes coupled threaded rod portions that extend to the second joint. The described structure supports extension and adjustment range through add-on threaded rod segments coupled through a connecting element, including embodiments with different thread pitches and embodiments having a non-threaded region. Further joint and adjustment mechanisms are described, including cardan/spherical or revolute joint arrangements and manual torque adjustment using a cross pin, as well as alternative platform alignment approaches using fiducial markers.

Claims Coverage

The provided independent claims cover three main inventive constructs: a strut assembly with a threaded-key/outer-sleeve length-adjustment mechanism, a strut assembly further specifying different thread pitches for first and second threaded portions, and an external fixation system with two platforms connected by such a length-adjustable strut assembly. Across the independent claims, the inventive features include the threaded-key internal threading, a translatably received threaded rod assembly engaged by internal and external threads, a second joint coupling to the second platform, and an outer sleeve rotation mechanism that adjusts the axial length between the first platform coupling and the threaded-rod end coupling.

Across the independent claims, the claim coverage centers on a length-adjustable strut assembly for an external fixation system where a threaded key provides an internal thread, a translatably received threaded rod assembly engages that internal thread via an external thread, joints couple the strut body and threaded rod assembly to respective first and second external fixation platforms, and rotation of an outer sleeve adjusts the axial length between the strut body end and the threaded-rod end. Two independent claims further specify that the threaded key uses first and second openings, and that a connecting element coupling two threaded rods can include externally threaded portions with different thread pitches.

Stated Advantages

Documented Applications