Disc space sizing devices

1. A spacing device for adjusting or measuring the spacing between adjacent vertebral bodies, comprising:

at least one distraction member movable between a first configuration for insertion into an intervertebral disc space and a second configuration in which the at least one distraction member has a larger height dimension than in the first configuration for adjusting or measuring the spacing between adjacent vertebral bodies;

an elongated actuator that translates along a longitudinal axis for moving the at least one distraction member between the first configuration and the second configuration; and

a plurality of links pivotally connecting the at least one distraction member to the actuator, wherein

the at least one distraction member includes outer and inner faces, the outer face being configured to contact one of the adjacent vertebral bodies in the second configuration and the inner face facing the actuator,

a monolithic distal portion of the actuator includes a plurality of enlarged portions spaced longitudinally along the longitudinal axis and each enlarged portion comprising a pivot point pivotally connecting at least one of said links to the actuator and at least one of said enlarged portions including a proximal half that is substantially symmetrical to a distal half, and

the inner face of the at least one distraction member defines a recess partially receiving one of the enlarged portions of the actuator when the at least one distraction member is in the first configuration.

2. A spacing device according to claim 1 , wherein the height dimension of the at least one distraction member is infinitely adjustable between the height dimension of the at least one distraction member in the first configuration and the height dimension of the at least one distraction member in the second configuration.

3. A spacing device according to claim 1 , wherein the at least one distraction member comprises a pair of distraction members movable toward and away from each other in moving between the first configuration and the second configuration.

4. A spacing device according to claim 3 , wherein the actuator for moving the at least one distraction member between the first configuration and the second configuration is movable between the pair of distraction members.

5. A spacing device according to claim 3 , wherein each distraction member includes an inner face defining a recess partially receiving said one of the enlarged portions of the actuator when the distraction members are in the first configuration.

6. A spacing device according to claim 1 , wherein the actuator is longitudinally movable with respect to the at least one distraction member.

7. A spacing device according to claim 1 , further comprising a delivery cannula including a distal-facing surface configured to contact a proximal end of the at least one distraction member when the at least one distraction member is moved from the first configuration to the second configuration.

8. A spacing device according to claim 1 , wherein

the inner face of the at least one distraction member defines a second recess partially receiving another one of the enlarged portions of the actuator when the at least one distraction member is in the first configuration.

9. A spacing device according to claim 1 , wherein

the at least one distraction member includes proximal and distal ends, and

the plurality of links are fully positioned between the proximal and distal ends of the at least one distraction member when the at least one distraction member is in the first configuration.

10. A spacing device according to claim 1 , wherein

the at least one distraction member includes proximal and distal ends, and

at least one of the links is fully positioned between the proximal and distal ends of the at least one distraction member when the at least one distraction member is in the first configuration.

11. A spacing device for adjusting or measuring the spacing between adjacent vertebral bodies, comprising:

at least one distraction member movable between a first configuration for insertion into an intervertebral disc space and a second configuration in which the at least one distraction member has a larger height dimension than in the first configuration for adjusting or measuring the spacing between adjacent vertebral bodies;

an elongated actuator with a longitudinal axis for moving the at least one distraction member between the first configuration and the second configuration; and

first and second pairs of links pivotally connecting the at least one distraction member to the actuator, wherein

a monolithic distal portion of the actuator includes a plurality of enlarged portions spaced longitudinally along the longitudinal axis, at least one of said enlarged portions includes a proximal half that is substantially symmetrical to a distal half of said at least one of said enlarged portions, each pair of links includes a distal end pivotally connected to a different one of the enlarged portions of the actuator,

the at least one distraction member includes proximal and distal ends,

the first pair of links is fully positioned between the proximal and distal ends of the at least one distraction member when the at least one distraction member is in the first configuration,

the entire first pair of links is spaced longitudinally of the entirety of the second pair of links, and

the actuator is configured for non-rotational movement along the longitudinal axis to move the at least one distraction member between the first configuration and the second configuration.

12. A spacing device according to claim 11 , wherein the height dimension of the at least one distraction member is infinitely adjustable between the height dimension of the at least one distraction member in the first configuration and the height dimension of the at least one distraction member in the second configuration.

13. A spacing device according to claim 11 , wherein the at least one distraction member comprises a pair of distraction members movable toward and away from each other in moving between the first configuration and the second configuration.

14. A spacing device according to claim 13 , wherein the actuator for moving the at least one distraction member between the first configuration and the second configuration is movable between the pair of distraction members.

15. A spacing device according to claim 11 , wherein the actuator is longitudinally movable with respect to the at least one distraction member.

16. A spacing device according to claim 11 , further comprising a delivery cannula including a distal-facing surface configured to contact a proximal end of the at least one distraction member when the at least one distraction member is moved from the first configuration to the second configuration.

17. A spacing device according to claim 11 , wherein the second pair of links is fully positioned between the proximal and distal ends of the at least one distraction member when the at least one distraction member is in the first configuration.

18. A spacing device for adjusting or measuring the spacing between adjacent vertebral bodies, comprising:

at least one distraction member movable between a first configuration for insertion into an intervertebral disc space and a second configuration in which the at least one distraction member has a larger height dimension than in the first configuration for adjusting or measuring the spacing between adjacent vertebral bodies;

an elongated actuator that translates along a longitudinal axis for moving the at least one distraction member between the first configuration and the second configuration; and

first and second pairs of links pivotally connecting the at least one distraction member to the actuator, wherein

a monolithic distal portion of the actuator includes a plurality of enlarged portions spaced longitudinally along the longitudinal axis and each enlarged portion comprising a pivot pin pivotally connecting one of said pairs of links to the actuator,

at least one of said enlarged portions includes a proximal half that is substantially symmetrical to a distal half of said at least one of said enlarged portions,

the at least one distraction member includes proximal and distal ends and outer and inner faces, the outer face being configured to contact one of the adjacent vertebral bodies in the second configuration and the inner face facing the actuator and including a portion extending to a position between the first and second pairs of links,

the first pair of links is fully positioned between the proximal and distal ends of the at least one distraction member when the at least one distraction member is in the first configuration, and

the entire first pair of links is spaced longitudinally of the entirety of the second pair of links.