Spinal stabilization systems and methods
A spinal stabilization system may be formed in a patient. In some embodiments, a minimally invasive procedure may be used to form a spinal stabilization system in a patient Bone fastener assemblies may be coupled to vertebrae Each bone fastener assembly may include a bone fastener and a collar. The collar may be rotated and/or angulated relative to the bone fastener. Detachable members may be coupled to the collar to allow for formation of the spinal stabilization system through a small skin incision. The detachable members may allow for alignment of the collars to facilitate insertion of an elongated member in the collars. An elongated member may be positioned in the collars and a closure member may be used to secure the elongated member to the collars.
1. A pedicle screw assembly comprising:
a threaded shank;
a housing configured to receive the threaded shank and an elongated member; and
a sleeve coupled with the housing, the sleeve having a length sufficient such that the sleeve extends above a patient's skin when the screw is secured to the patient's vertebra, wherein the sleeve and housing are adapted to be separated at a break-off section, wherein the housing is configured to receive the elongated member while the sleeve is coupled to the housing at the break-off section;
wherein the housing includes a proximal-most region of material having a reduced cross-sectional area compared to a distal region of the housing, wherein the reduced cross-sectional area defines the break-off section; and
wherein the proximal-most region of the housing is threaded at the reduced cross-sectional area and threadedly coupled with a threaded distal end of the sleeve having a reduced cross-sectional area compared to a proximal region of the sleeve.
2. The pedicle screw assembly of claim 1 , wherein the threaded shank is cannulated.
3. The pedicle screw assembly of claim 1 , wherein the pedicle screw extends along a longitudinal axis, and the housing includes a portion that is substantially “U”-shaped in a longitudinal cross-section relative to the longitudinal axis.
4. The pedicle screw assembly of claim 1 , wherein the sleeve has one or more slots configured to allow passage of the elongated member to a target site on the patient's vertebra.
5. The pedicle screw assembly of claim 1 , wherein the sleeve extends along a longitudinal axis and has a proximal portion that is substantially “C”-shaped in a transverse cross section relative to the longitudinal axis.
6. The pedicle screw assembly of claim 1 , wherein the housing has an inner threaded surface, wherein the pedicle screw assembly further comprises a screw cap configured to screw into the housing to secure the elongated member, wherein the inner threaded surface is positioned entirely below the break-off section.
7. The pedicle screw assembly of claim 1 , wherein the proximal-most region of material having the reduced cross-sectional area of the break-off section is designed to shear off at a predetermined torque in a predetermined location.
8. The pedicle screw assembly of claim 1 , wherein the proximal-most region of material having the reduced cross-sectional area is configured to be carried away by the sleeve after the break-off section is removed.
9. The pedicle screw assembly of claim 1 , wherein the housing and the sleeve are non-monolithic due to being threadedly coupled.
10. The pedicle screw assembly of claim 1 , wherein the housing is configured to receive the threaded shank along a passage having a first section formed by the proximal-most region of the material of the housing and the threaded distal end of the sleeve, and a second section formed by the distal region of the housing, wherein the first section has a first passage diameter and the second section has a second passage diameter, wherein the first passage diameter is larger than the second passage diameter .
11. The break-off pedicle screw assembly of claim 6 , wherein internal surfaces of the distal end of the sleeve having a reduced cross-sectional area are smooth.
12. A break-off pedicle screw assembly comprising:
a threaded shank; and
a break-off collar, the break-off collar having a break-off portion connecting an elongated proximal portion of the collar and a distal portion of the collar configured to couple to the shank at a threaded engagement, the distal portion configured to receive a fixation rod, wherein the elongated proximal portion has a length such that it extends beyond a patient's skin when the shank is inserted into a spinal location, and wherein the break-off portion is configured such that application of a sufficient amount of torque to the elongated proximal portion causes the elongated proximal portion to be separated from the distal portion at the break-off portion;
wherein the break-off collar has two opposing walls and a slot extending between both walls, the slot configured to receive the fixation rod, the slot extending from the distal portion through the break-off portion and at least part of the proximal portion, the break-off portion being located on the two opposing walls proximal to above where the fixation rod is configured to be received; and
wherein the break-off portion and the elongated proximal portion of the collar are thinner than the distal portion of the collar relative to an outer surface of the break-off collar.
13. The break-off pedicle screw assembly of claim 12 , wherein the threaded shank and break-off collar are cannulated.
14. The break-off pedicle screw assembly of claim 12 , wherein the break-off portion of the break-off collar includes a first portion extending proximally from the distal portion and a second portion extending distally from the elongate proximal portion, the first portion and the second portion configured to be in threaded connection with each other.
15. The break-off pedicle screw assembly of claim 14 , wherein the first portion and the second portion that are configured to be in threaded connection with each other each have a reduced cross sectional area compared to adjacent portions of the break-off collar.
16. The break-off pedicle screw assembly of claim 12 , wherein the threaded shank extends along a longitudinal axis, and the distal portion of the break-off collar is substantially “U”-shaped in a longitudinal cross-section relative to the longitudinal axis.
17. The break-off screw assembly of claim 12 , wherein the elongated proximal portion extends along a longitudinal axis and is substantially “C”-shaped in a transverse cross section relative to the longitudinal axis.
18. The pedicle screw assembly of claim 12 , wherein:
the break-off portion and the elongated proximal portion of the collar form a passage having a first diameter; and
the distal portion of the collar forms a second passage axially aligned with the first passage and having a second diameter;
wherein the first diameter is larger than the second diameter.
19. A pedicle screw assembly comprising:
a fastener having a head and a threaded shank extending from the head;
a housing comprising:
a lower portion defining an opening for the shank that is configured to mate with the head;
an upper portion defining a channel for receiving an elongated member; and
a break-off section extending upward from the upper portion away from the lower portion;
a sleeve comprising:
a lower section configured to releasably couple with the break-off section of the housing; and
an upper section configured to guide the fastener into the housing from above a skin level of a patient.
20. The pedicle screw assembly of claim 19 , wherein an inner surface of the upper portion of the housing includes threading configured to receive a closure member, wherein the threading is located entirely below the break-off section.