An implant for insertion between vertebral body endplates includes first and second end members, each with a respective endplate contact surface and an extension portion. An intermediate section may be contained between the first and second end members and includes a port into which a substance may be inserted. The intermediate section may be expandable upon the introduction of the substance between a first size to space the first and second end members a first distance apart and a second enlarged size to space the first and second end members a second greater distance apart. The intermediate section may be implemented as an expandable balloon-like member. The intermediate section may include a permeable portion to allow the substance, which may include bone growth materials, to pass from inside the implant to contact the vertebral body endplates.