Intervertebral implant and system of an intervertebral implant and an instrument for inserting the intervertebral implant

A method of inserting an intervertebral implant between vertebrae using an instrument, the intervertebral implant comprising an upper wall configured to engage a first vertebral end plate, a lower wall configured to engage a second vertebral end plate, wherein a central axis extends through the upper wall and the lower wall, and wherein the implant has a length and a width in respective directions perpendicular to the central axis, the length of the implant being greater than the width of the implant, an axially compressible load transmitting part extending between the upper wall and the lower wall and configured to transmit load between the upper wall and the lower wall, wherein the load transmitting part is attached to the upper wall at at least two first connecting locations, is attached to the lower wall at at least two second connecting locations, and has an X-shaped profile, with the X-shape being viewable in a widthwise direction along which the width of the implant extends, and two sidewalls on opposite sides of the implant, wherein each sidewall extends between at least one of the first connecting locations and at least one of the second connecting locations and is distinct from the load transmitting part, each sidewall having at least a portion that is located at a same axial height as an axially compressible region of the load transmitting part while also being positioned farther away from the central axis than the entire upper wall, the entire lower wall, and the load transmitting part in a lengthwise direction along which the length of the implant extends, wherein at least one of the upper wall or the lower wall is convexly curved, wherein a plurality of bone engagement projections are formed on the at least one of the upper wall or the lower wall, wherein all of the bone engagement projections are located between the connecting locations of the load transmitting part and project farther axially than all portions of the implant that include or that are located outside of the connecting locations toward the sidewalls, with at least one of the plurality of projections approximate the central axis defining a greatest axial height of the implant measured between the upper and lower walls, wherein the load transmitting part is configured to assume a compressed condition in which the greatest axial height of the implant is a first height, and an expanded condition in which the greatest axial height of the implant is a second height greater than the first height, and wherein the implant is made of a material that exhibits shape memory properties that permit the implant to remain in the compressed condition without outside forces acting upon it and to change to the expanded condition in response to a temperature being at a recovery level, the method comprising:

• engaging the implant with an instrument when the implant is in the compressed condition without compressing the implant;
• inserting the implant between vertebrae using the instrument;
• and
• releasing the implant after insertion between the vertebrae.