Interspinous process implants having deployable engagement arms
Spinal implants include an elongated body portion dimensioned and configured for percutaneous introduction into a target interspinous process space, at which interspinous distraction and/or spinal fusion are desired. The body portion can include a threaded outer surface, or alternatively a smooth surface. The body portion can include one or more interior cavities, and can include deployable engagement members adapted and configured to move in tandem between a stowed position retracted within the interior cavity of the body portion and a deployed position extended from the interior cavity of the body for engaging adjacent spinous processes. An internal drive assembly for selectively moving the engagement members from the stowed position to the deployed position can be provided, as can a elements for locking the engagement members in a deployed position.
1. A spinal implant comprising:
an elongated threaded body portion dimensioned and configured for percutaneous introduction into the interspinous process space and having a longitudinal axis, the body portion including an interior cavity and a pair of deployable engagement members mounted to rotate in tandem about a common axis extending transverse to the longitudinal axis of the body portion between a stowed position retracted within the interior cavity of the body portion and a deployed position extended from the interior cavity of the body portion for engaging the spinous process,
wherein each engagement member includes a pair of curved engagement arms extending radially outwardly from a central hub and each engagement arm includes a distal claw portion having a plurality of teeth for engaging the spinous process.
2. A spinal implant as recited in claim 1 , further comprising a drive assembly extending into the interior cavity of the threaded body portion for selectively moving the engagement members in tandem from the stowed position to the deployed position.
3. A spinal implant as recited in claim 2 , further comprising means operatively associated with the drive assembly for selectively locking the engagement members in the deployed position.
4. A spinal implant as recited in claim 1 , wherein the drive assembly includes a main drive shaft that extends into the interior cavity of the body portion along the longitudinal axis of the body portion.
5. A spinal implant as recited in claim 1 , wherein the threaded body portion includes an outer profile, tapering axially inwardly in a distal nose portion thereof, configured to gradually distract adjacent spinous processes during insertion of the implant into the interspinous process space.
6. A spinal implant as recited in claim 5 , wherein threads are provided on the body portion, and extend at least partially over the nose portion thereof.
7. A spinal implant as recited in claim 6 , wherein the distal nose portion tapers axially inwardly with respect to a central region of the body, by an angle of about 30 degrees, with respect to a longitudinal axis thereof.
8. A spinal implant as recited in claim 1 , further comprising an interior core portion adapted and configured for rigidifying the spinal implant.
9. A spinal implant as recited in claim 8 , wherein the core portion includes an integral tip portion, arranged at the distal end of the implant.
10. A spinal implant as recited in claim 1 , wherein the body portion includes a separately formed proximal portion, formed of a material dissimilar from a material from which a central portion of the body portion is formed.
11. A spinal implant as recited in claim 10 , wherein the proximal portion is formed of a metal material, and the central portion of the body portion is formed of a polymeric material.
12. A spinal implant as recited in claim 1 , wherein the teeth are dissimilar.
13. A spinal implant comprising:
a) A threaded elongated body portion dimensioned and configured for percutaneous introduction into the interspinous process space, the threaded elongated body portion defining a longitudinal axis and having an interior cavity;
b) a pair of deployable engagement members adapted and configured to move in tandem about a common axis extending transverse to the longitudinal axis of the threaded elongated body portion between a stowed position retracted within the interior cavity of the threaded elongated body portion and a deployed position extended from the interior cavity of the threaded elongated body portion for engaging the spinous process; and
c) a rotatable drive shaft extending into the interior cavity of the threaded elongated body portion along the longitudinal axis thereof for selectively moving the engagement members in tandem from the stowed position to the deployed position,
wherein two engagement members are provided for engaging spinous process, each engagement member includes a pair of curved engagement arms extending radially outwardly from a central hub, and each engagement arm includes a distal claw portion having a plurality of teeth for engaging the spinous process.
14. A spinal implant as recited in claim 13 , a locking cap operatively associated with the rotatable drive shaft and the body portion for selectively locking the engagement members in the deployed position.
15. A spinal implant as recited in claim 13 , wherein the teeth are dissimilar.
16. A method of lateral insertion of a spinal implant into an interspinous process space, comprising the steps of:
a) forming an incision in a patient's skin, lateral from a target interspinous process space, in which the implant is to be placed;
b) inserting a stylet through the incision, laterally to the target interspinous process space, using an internal imaging technique, to form an entry path;
c) inserting one or more dilators, sequentially, along the entry path to dilate soft tissues between the incision and the target interspinous process space;
d) inserting a sleeve through the entry path;
e) selecting an implant having a size appropriate for a desired amount of interspinous distraction and a pair of deployable engagement members for engaging the spinous process, the engagement members being mounted for rotational deployment in tandem about a common axis that extends transverse to a longitudinal axis of the implant, wherein each engagement member includes a pair of curved engagement arms extending radially outwardly from a central hub, and each engagement arm includes a distal claw portion having a plurality of teeth for engaging the spinous process;
f) inserting the implant, held by an insertion device, through the sleeve, up to the target interspinous process space;
g) advancing the implant into the interspinous process space; and
h) deploying the pair of engagement members.
17. A method of lateral insertion of a spinal implant into an interspinous process space of claim 16 , wherein the advancing step includes rotating the implant along a longitudinal axis thereof, to effect axial advancement of the implant by way of threads formed on an outer surface thereof.
18. A method of lateral insertion of a spinal implant into an interspinous process space of claim 16 , wherein the teeth are dissimilar.