Locking screw assembly for facilitating direct lateral interbody fusion procedures
Methods and apparatus for affixing a retaining washer proximate an interbody region following a direct lateral interbody fusion (DLIF) procedure. The system includes an installation device characterized by a width dimension W and a length dimension L; a retaining washer having a substantially planar surface region, the retaining washer configured to retain an interbody graft within an interbody region; and a screw having a shaft configured to secure the retaining washer to a vertebral body. The screw and the washer are configured to orient the screw shaft along an angle θ, where θ is a function of W and L.
1. A surgical assembly for affixing a retaining washer proximate an interbody region following a direct lateral interbody fusion (DLIF) procedure, the assembly comprising:
an installation device characterized by a width dimension W and a length dimension L;
a retaining washer having a substantially planar surface region, the retaining washer configured to retain an interbody graft within an interbody region; and
a screw having a shaft configured to secure the retaining washer to a vertebral body;
wherein:
the screw and the washer are configured to orient the screw shaft along an angle θ, where θ is a function of W and L;
the screw comprises a head having a substantially flat underside;
the screw shaft is oriented at angle θ relative to a line orthogonal to the substantially flat underside of the screw head; and
the screw shaft comprises a first locking mechanism extending along a portion of the shaft proximate the head, and the washer comprises a second locking mechanism configured to engage the first locking mechanism.
2. The assembly of claim 1 , wherein a proximal portion of the shaft is in the range of about 0.2 to 5 millimeters.
3. The assembly of claim 2 , wherein the first and second locking mechanisms comprise mating geometric configurations.
4. The assembly of claim 1 , wherein a proximal portion of the shaft is in the range of about 2 mm.
5. The assembly of claim 1 , wherein the retaining washer comprises a major lobe and a minor lobe, and further wherein the first and second locking mechanisms are configured to permit the surgeon to orient the major lobe proximate the interbody region by rotating the screw to a desired angular position.
6. The assembly of claim 1 , wherein the retaining washer comprises a through-hole oriented at angle θ relative to the line orthogonal to the substantially flat underside of the screw head.
7. The assembly of claim 6 , wherein the screw shaft and the through-hole are configured for mating threaded engagement.
8. The assembly of claim 1 , wherein the washer comprises a through-hole oriented at angle θ relative to the line orthogonal to the substantially planar surface region of the washer.
9. A method of installing a major lobe of a retaining plate between adjacent boney anatomical structures during a surgical procedure, the method comprising:
placing an installation tube adjacent a surgical site, the installation tube being characterized by a width dimension W, a length dimension L, and an insertion angle θ which is proportional to the arctangent of the quantity [W/L];
placing the retaining plate adjacent one of the boney anatomical structures;
introducing a screw and a distal end of a drive tool into the installation tube;
inserting the screw into a through-hole of the retaining plate, wherein the through-hole is inclined at the angle θ relative to a line orthogonal to the plane of the retaining plate; and
rotating the screw along its axis to simultaneously: i) secure the screw to one of the boney anatomical structures; and ii) orient a major lobe of the retaining plate between the adjacent boney anatomical structures.