Expandable spinal fusion implant, related instruments and methods

An intervertebral spacer, comprising:

• a first side having a proximal end and a distal end, and comprising a first plurality of links joined by a first plurality of joints;
• a second side having a proximal end and a distal end, and comprising a second plurality of links joined by a second plurality of joints;
• a proximal end including an insertion link having an aperture dimensioned to receive an insertion tool, said insertion link joined to the proximal ends of the first side and the second side;
• a distal end including a coupling assembly for receiving a portion of the insertion tool;
• a first support face configured to contact a first vertebral body endplate;
• a second support face opposite said first support face, and configured to contact a second vertebral body endplate,
• wherein said intervertebral spacer has an insertion configuration in which the intervertebral spacer is elongated and the first side and the second side are linear and an axis of insertion is parallel to a longitudinal axis of the intervertebral spacer, and an expanded configuration in which the first side and the second side are displaced to define a graft aperture therebetween;
• and
• a positioner gear assembly housed in the distal end of the intervertebral spacer, and configured to maintain the intervertebral spacer in the expanded configuration.