Expandable intervertebral implants and instruments

An interbody device system comprising:

• a first end body and a second end body opposite the first end body, the first and second end bodies are separated from one another by a central interior space;
• a first intermediate body and a second intermediate body opposite the first intermediate body, each of the first and second intermediate bodies positioned between the first and second end bodies, an elongated gap at an interface of the periphery of each end body and the periphery of each intermediate body, wherein opposing peripheral surfaces at the interfaces of each end body and each intermediate body are complementarily curved;
• a first channel extending from an exterior surface of the device into the central interior space;
• and
• a screw extending through the channel;
• wherein the interbody device is transformable between a compact configuration in which the central interior space is minimized and an expanded configuration in which the central interior space is maximized, wherein the screw locks the interbody device in the expanded configuration, and wherein a width of each elongated gap between the opposing peripheral surfaces of the end bodies and the intermediate bodies remains constant whether the device is in the compact configuration or the expanded configuration.