Methods and apparatus for coupling a prosthesis to a spinal segment

Inventors

Alamin, Todd • Kothari, Manish • Malandain, Hugues • Cahill, Colin • Fielding, Louis

Assignees

Empirical Spine Inc

Abstract

A method for coupling a prosthesis to a spinal segment in a patient includes the steps of selecting first and second reference points disposed along the spinal segment and pre-operatively measuring a target distance. The target distance extends between the first and second reference points while the patient is in a preferred posture such as the standing position. A prosthesis is coupled to the spinal segment and the prosthesis is then intra-operatively adjusted in order to set the distance between the first and second reference points based on the target distance.

Core Innovation

The invention relates to orthopedic methods and apparatus for restricting flexion of a spinal segment in a patient. A tether structure comprises one or more straps adapted to be coupled with a superior spinous process and an inferior spinous process or sacrum, and the tether structure is used to apply tension to components of the system to achieve a desired spinal mechanical behavior.

A compliance element is coupled with the tether structure and elastically elongates as tension is applied through the tether structure. A first constraining tool is releasably coupled with the compliance element so as to hold the compliance element in a first desired position and allow only a first predetermined amount of elastic elongation as tension is applied to the first compliance element through the tether structure.

The system further includes mechanically defined adjustment and verification concepts, including selecting pre-operative reference points on spinous processes in a standing posture and using lateral/AP radiographs with a target distance to place the device in a neutral or desired configuration while permitting extension. Additional embodiments describe estimating device sizing using major and minor axes and calculating prosthesis circumference using calibration markings, as well as using pain-triggered radiography with radiopaque markers to determine a threshold position, together with compliance elements and constraining tools that prevent compliance elongation during adjustment.

The detailed embodiments also describe compliance elements that provide elastic resistance to flexion, including spring-like compliance elements. Constraining tools include cradles and arms with elongate shafts and lumens for temporarily holding and aligning the compliance elements, including dual tools for two compliance elements, and features for concentric alignment with a locking mechanism and counter-torque during tether tightening.

Claims Coverage

The partial content provides one independent claim and several dependent claims. Across these, the independent claim covers a flexion-restraining spinal tether system with an elastically elongating compliance element and a releasably coupled constraining tool that permits a predetermined amount of elastic elongation.

Taken together, the claims cover restricting flexion of a spinal segment using a tether structure coupled between a superior spinous process and an inferior spinous process or sacrum, an elastically elongating compliance element, and a releasably coupled constraining tool that holds the compliance element in a desired position while allowing only a predetermined amount of elastic elongation, with further refinements for adjustability, symmetric bilateral compliance/tool pairs, locking and driver alignment via an elongate shaft with a lumen, and a threshold condition for when constraining begins.

Stated Advantages

Documented Applications