An insert for establishing a desired spacing between a pair of succeeding vertebrae and having a body including an extending end for supporting a location associated with a first selected lumbar vertebrae. An opposite extending end supports a spaced apart and opposing location associated with a second successively positioned lumbar vertebrae. Upon pre-positioning the body in an open space established between the vertebrae, an actuating input causes the first extending end to displace outwardly relative to the second end and into contacting support with the vertebrae.