Spinal implant with attachment system

A method of treating a patient's spine comprising:

• accessing at least a portion of a patient's spine via a posterior approach;
• inserting an implantable body between vertebral bodies of the patient's spine, wherein the body comprises an upper surface, a lower surface, an anterior portion, and a non-expandable posterior portion having a fixed height, wherein a first aperture is defined within the posterior portion of the body
• inserting a fixation element into the first aperture to attach the body to the vertebral bodies, wherein a space exists between the fixation element and an inner surface of the body defining the first aperture when the fixation element is fully inserted into the first aperture, which permits a non-zero degree of nutation by the fixation element with respect to the first aperture;
• placing a plate onto the body, the plate having a complementary fit with the posterior portion of the body and configured to nest against the posterior portion of the body, the plate comprising one or more arms, a first of the one or more arms providing a second aperture that aligns with the first aperture within the posterior portion of the body to permit access to a head portion of the fixation element, wherein the first of the one or more arms or a second of the one or more arms comprises a separate adjustable arm that is adjustable in height relative to a remainder of the plate, the placement being based on aligning the second aperture over the head portion of the fixation element;
• and
• inserting at least one locking element through the second aperture into the head portion of the fixation element.