Mechanical ligament balancing devices

Inventors

Angibaud, Laurent • Mauldin, Michael • Rueff, Matt

Assignees

Advita Ortho LLC

Abstract

A device including a first plate configured to interface with a first bone structure of a joint; a second plate configured to interface with a second bone structure of the joint opposite the first bone structure; and at least one mechanical actuation mechanism disposed between the first plate and the second plate and configured to apply a distraction force along an axis between the first plate and the second plate so as to urge the first plate and the second plate away from one another, wherein the device is configured so as to have a range of motion ranging from a minimum distance between the first plate and the second plate to a maximum distance between the first plate and the second plate, and wherein the mechanical actuation mechanism is configured such that the distraction force is substantially constant distraction force across the range of motion.

Core Innovation

The invention provides a device comprising a first plate configured to interface with a first bone structure of a joint, and a second plate configured to interface with a second bone structure of the joint opposite the first bone structure. At least one mechanical actuation mechanism is disposed between the first plate and the second plate and is configured to apply a distraction force along an axis between the first plate and the second plate so as to urge the first plate and the second plate away from one another. The device defines a range of expansion between a minimum distance and a maximum distance between the first plate and the second plate.

The mechanical actuation mechanism comprises a first actuation sub-mechanism and a second actuation sub-mechanism. The first actuation sub-mechanism provides a first actuation sub-mechanism distraction force, and the second actuation sub-mechanism provides a second actuation sub-mechanism distraction force that is antagonist to the first actuation sub-mechanism distraction force. As the device moves through the range of expansion from the maximum distance to the minimum distance, the first actuation sub-mechanism distraction force varies and the second actuation sub-mechanism distraction force varies.

The varying first actuation sub-mechanism distraction force and the varying second actuation sub-mechanism distraction force combine to provide the distraction force that is a substantially constant distraction force across the range of expansion. The described approach further includes stability mechanisms to constrain plate degrees of freedom and mechanical implementation variants in which the opposing actuation sub-mechanisms use antagonist behavior to maintain the substantially constant distraction force.

The document further describes performing a cut to the second bone structure to produce a cut surface, positioning the device within the joint such that the second plate abuts the cut surface, and characterizing laxity of ligaments of the joint while the device is positioned within the joint. The substantially constant distraction force across the range of expansion is used to characterize ligament laxity and joint gap conditions during intraoperative assessment and spacing.

Claims Coverage

The document includes two independent claims: one device claim and one method claim. Both claims revolve around applying distraction force via antagonist actuation sub-mechanisms whose combined output yields a substantially constant distraction force across a defined range of expansion.

Across the independent claims, the central inventive concept is the use of two antagonist actuation sub-mechanisms whose individually varying distraction forces combine to yield a substantially constant distraction force over the device’s expansion range, and, in the method claim, using that device while positioned in the joint to characterize ligament laxity.

Stated Advantages

Documented Applications