Monoaxial and polyaxial pedicle screws and related methods

Abstract

Methods for installing bone anchors, such as pedicle screws or other surgical screws. In some implementations, the surgical screw may be coupled with a connection member, such as a tulip assembly, configured to couple the surgical screw with a stabilization member, such as a spinal fixation rod. The connection member may be initially coupled with the surgical screw in a polyaxial configuration, after which the connection member may be secured to the surgical screw in a monoaxial configuration. The stabilization member may then be coupled and secured with the connection member such that the stabilization member cannot move relative to the connection member. In some implementations, the stabilization member may be locked or secured to the connection member after the connection member has been secured to the surgical screw in a monoaxial configuration.

1 . A method installing a surgical screw, the method comprising the steps of:
 securing a surgical screw within a bony structure;   coupling a connection member with the surgical screw, wherein the connection member is configured to couple the surgical screw with a stabilization member, and wherein the connection member is coupled with the surgical screw in a polyaxial configuration such that the surgical screw can be positioned at a plurality of angles relative to the stabilization member;   securing the connection member to the surgical screw at a fixed angle such that the connection member is coupled with the surgical screw in a monoaxial configuration;   coupling the stabilization member with the connection member; and   securing the stabilization member to the connection member such that the stabilization member cannot move relative to the connection member, wherein the step of securing the stabilization member to the connection member is performed after the step of securing the connection member to the surgical screw at a fixed angle.   
     
     
         2 . The method of  claim 1 , wherein the connection member comprises a tulip assembly. 
     
     
         3 . The method of  claim 2 , wherein the tulip assembly comprises a compressible cup configured to engage at least a portion of the surgical screw. 
     
     
         4 . The method of  claim 3 , wherein the surgical screw comprises a head portion, and wherein the compressible cup is configured to extend around the head portion such that at least a portion of the compressible cup engages a lower portion of the head portion and at least a portion of the compressible cup engages an upper portion of the head portion during the step of securing the connection member to the surgical screw at a fixed angle. 
     
     
         5 . The method of  claim 4 , wherein the tulip assembly further comprises a wedge member configured to be disposed within the tulip assembly, wherein the wedge member is configured for selectively compressing the compressible cup about the head portion of the surgical screw, thereby securing the head portion of the surgical screw in place within the tulip assembly during the step of securing the connection member to the surgical screw at a fixed angle. 
     
     
         6 . The method of  claim 5 , wherein the tulip assembly further comprises a second wedge member configured to be disposed within the tulip assembly, wherein the second wedge member is configured for selectively compressing the compressible cup about the head portion of the surgical screw, thereby securing the head portion of the surgical screw in place within the tulip assembly during the step of securing the connection member to the surgical screw at a fixed angle. 
     
     
         7 . The method of  claim 6 , wherein the second wedge member is integrally coupled with the wedge member. 
     
     
         8 . The method of  claim 1 , wherein the step of coupling the stabilization member with the connection member is performed after the step of securing the connection member to the surgical screw at a fixed angle. 
     
     
         9 . The method of  claim 1 , wherein the surgical screw comprises a pedicle screw. 
     
     
         10 . The method of  claim 1 , wherein the bony structure comprises a portion of a patient's spine. 
     
     
         11 . The method of  claim 10 , wherein the bony structure comprises a pedicle of the patient's spine. 
     
     
         12 . The method of  claim 1 , wherein the stabilization member comprises a rod. 
     
     
         13 . A method installing a bone anchor, the method comprising the steps of:
 securing a bone anchor comprising a bone anchor head within a bony structure;   coupling a tulip assembly with the bone anchor, wherein the tulip assembly is configured to couple the bone anchor with a stabilization member, and wherein the tulip assembly is coupled with the bone anchor in a polyaxial configuration such that the bone anchor can be positioned at a plurality of angles relative to the stabilization member;   securing the tulip assembly to the bone anchor at a fixed angle such that the tulip assembly is coupled with the bone anchor in a monoaxial configuration, wherein the tulip assembly is secured to the bone anchor at a fixed angle by applying a force to at least a portion of the tulip assembly, and wherein the force is transferred to the bone anchor head such that the force is at least substantially evenly distributed about the bone anchor head;   coupling the stabilization member with the tulip assembly; and   securing the stabilization member to the tulip assembly.   
     
     
         14 . The method of  claim 13 , wherein the step of securing the stabilization member to the tulip assembly is performed such that the stabilization member cannot move relative to the tulip assembly. 
     
     
         15 . The method of  claim 13 , wherein the step of securing the stabilization member to the tulip assembly is performed after the step of securing the tulip assembly to the bone anchor at a fixed angle. 
     
     
         16 . The method of  claim 13 , wherein the tulip assembly comprises a compressible sheath configured to engage at least a portion of the bone anchor head, and wherein the compressible sheath is used to transfer the force to the bone anchor head. 
     
     
         17 . The method of  claim 16 , wherein the tulip assembly further comprises a compression structure configured to compress the compressible sheath about the bone anchor head during the step of securing the tulip assembly to the bone anchor at a fixed angle, thereby securing the bone anchor head in place within the tulip assembly disposed within the tulip assembly. 
     
     
         18 . The method of  claim 17 , wherein the compressible sheath comprises a first curved surface, wherein the compression structure comprises a second curved surface, wherein the second curved surface is configured to at least substantially mate with the first curved surface during the step of securing the tulip assembly to the bone anchor at a fixed angle, thereby securing the head portion of the surgical screw in place within the tulip assembly. 
     
     
         19 . The method of  claim 18 , wherein the bone anchor head has an at least substantially spherical shape and wherein at least a portion of the compressible sheath has an at least substantially spherical shape configured to at least substantially mate with the bone anchor head. 
     
     
         20 . The method of  claim 17 , wherein the compression structure is configured to transfer a force delivered to the compressible sheath in a direction at least substantially downward towards the bone anchor head to a force at least substantially evenly distributed about the bone anchor head. 
     
     
         21 . The method of  claim 13 , wherein the bone anchor comprises a pedicle screw. 
     
     
         22 . A method installing a surgical screw, the method comprising the steps of:
 securing a surgical screw within a bony structure of a patient's spine, wherein the surgical screw comprises a screw head;   coupling a tulip assembly with the surgical screw, wherein the tulip assembly is configured to couple the surgical screw with a stabilization member, and wherein the tulip assembly is coupled with the surgical screw in a polyaxial configuration such that the surgical screw can be positioned at a plurality of angles relative to the stabilization member;   securing the tulip assembly to the surgical screw at a fixed angle such that the tulip assembly is coupled with the surgical screw in a monoaxial configuration, wherein the tulip assembly is secured to the surgical screw at a fixed angle by applying a force to at least a portion of the tulip assembly, and wherein the force is transferred to the screw head such that the force is at least substantially evenly distributed about the screw head;   coupling the stabilization member with the tulip assembly; and   securing the stabilization member to the tulip assembly such that the stabilization member cannot move relative to the tulip assembly, wherein the step of securing the stabilization member to the tulip assembly is performed after the step of securing the tulip assembly to the surgical screw at a fixed angle.