Cannulated continuous compression screw

Abstract

A bone screw may be insertable into a bone. The bone screw may have a distal member with bone-engaging threads, a proximal member configured to slidably engage the distal member, and a tension member with a proximal end coupled to the proximal member, and a distal end coupled to the distal member such that, in response to motion of the distal member away from the proximal member, the tension member elongates and urges the distal member to move toward the proximal member.

What is claimed is: 
     
         1 . A bone screw insertable into a bone, the bone screw comprising:
 a distal member comprising bone-engaging threads;   a proximal member configured to slidably engage the distal member; and   a tension member comprising:
 a proximal end coupled to the proximal member; and 
 a distal end coupled to the distal member such that, in response to motion of the distal member away from the proximal member, the tension member elongates and urges the distal member to move toward the proximal member; 
   wherein:
 one of the proximal member and the distal member comprises a torque transmission socket; 
 the other of the proximal member and the distal member comprises a shaft adjacent to a torque transmission protrusion that is slidably receivable within the torque transmission socket to transmit torque between the proximal member and the distal member; and 
 the torque transmission protrusion comprises a torque transmission feature with a first maximum diameter larger than a second maximum diameter of a portion of the shaft that is adjacent to the torque transmission feature. 
   
     
     
         2 . The bone screw of  claim 1 , wherein the tension member further comprises a shaft extending from the proximal end to the distal end, the shaft comprising a cannula sized to receive a guidewire. 
     
     
         3 . The bone screw of  claim 1 , wherein the proximal member comprises a head and a shank that houses the torque transmission socket, the head comprising head threading with a first pitch different from a second pitch of the bone-engaging threads. 
     
     
         4 . The bone screw of  claim 1 , wherein:
 the proximal member and the distal member define a longitudinal axis; and   the proximal member comprises a head and a shank that houses the torque transmission socket, the head comprising a proximal-most surface that is nonperpendicular to the longitudinal axis.   
     
     
         5 . The bone screw of  claim 1 , wherein:
 the torque transmission socket comprises a female spline; and   the torque transmission feature of the torque transmission protrusion comprises a male spline configured to mate with the female spline.   
     
     
         6 . The bone screw of  claim 1 , wherein:
 the bone screw has a length from a proximal-most end of the proximal member to a distal-most end of the distal member; and   the proximal member and the distal member cooperate to define a length limiting mechanism configured to:
 prevent the length from exceeding a maximum length; and 
 prevent the length from decreasing below a minimum length. 
   
     
     
         7 . The bone screw of  claim 1 , wherein:
 the proximal member and the distal member define a longitudinal axis;   the proximal member comprises the torque transmission socket;   the distal member comprises the torque transmission protrusion;   the distal member comprises a distal engagement surface, distinct from the torque transmission protrusion, facing away from the longitudinal axis;   the proximal member comprises a proximal engagement surface, distinct from the torque transmission socket, facing toward the longitudinal axis; and   the distal engagement surface is positioned to abut the proximal engagement surface to transmit bending loads from the distal member to the proximal member.   
     
     
         8 . A bone screw insertable into a bone, the bone screw comprising:
 a distal member comprising bone-engaging threads;   a proximal member configured to slidably engage the distal member; and   a tension member comprising:
 a proximal end coupled to the proximal member; and 
 a distal end coupled to the distal member such that, in response to motion of the distal member away from the proximal member, the tension member elongates and urges the distal member to move toward the proximal member; 
   wherein:
 the bone screw has a length from a proximal-most end of the proximal member to a distal-most end of the distal member; and 
 the proximal member and the distal member cooperate to define a length limiting mechanism configured to:
 prevent the length from exceeding a maximum length; and 
 prevent the length from decreasing below a minimum length. 
 
   
     
     
         9 . The bone screw of  claim 8 , wherein the tension member further comprises a shaft extending from the proximal end to the distal end, the shaft comprising a cannula sized to receive a guidewire. 
     
     
         10 . The bone screw of  claim 8 , wherein the proximal member comprises a shank and a head comprising head threading with a first pitch different from a second pitch of the bone-engaging threads. 
     
     
         11 . The bone screw of  claim 8 , wherein:
 the proximal member and the distal member define a longitudinal axis; and   the proximal member comprises a shank and a head comprising a proximal-most surface that is nonperpendicular to the longitudinal axis.   
     
     
         12 . The bone screw of  claim 8 , wherein:
 the length limiting mechanism comprises:
 a distal shoulder and a proximal shoulder, both of which are on one of the proximal member and the distal member; and 
 a stop feature on the other of the proximal member and the distal member; and 
   the stop feature is positioned between the distal shoulder and the proximal shoulder to define the minimum length and the maximum length by abutting the stop feature against the distal shoulder and the proximal shoulder.   
     
     
         13 . The bone screw of  claim 12 , wherein:
 the distal shoulder and the proximal shoulder are on the distal member;   the stop feature is on the proximal member;   the stop feature abuts the distal shoulder to define the minimum length; and   the stop feature abuts the proximal shoulder to define the maximum length.   
     
     
         14 . The bone screw of  claim 8 , wherein:
 the proximal member and the distal member define a longitudinal axis;   the proximal member comprises a proximal torque transmission feature;   the distal member comprises a distal torque transmission feature that engages the proximal torque transmission feature to receive torque from the proximal member;   the distal member comprises a distal engagement surface, distinct from the distal torque transmission feature, facing away from the longitudinal axis;   the proximal member comprises a proximal engagement surface, distinct from the proximal torque transmission feature, facing toward the longitudinal axis; and   the distal engagement surface is positioned to abut the proximal engagement surface to transmit bending loads from the distal member to the proximal member.   
     
     
         15 . A bone screw insertable into a bone, the bone screw comprising:
 a distal member comprising bone-engaging threads;   a proximal member configured to slidably engage the distal member; and   a tension member comprising:
 a proximal end coupled to the proximal member; 
 a distal end coupled to the distal member such that, in response to motion of the distal member away from the proximal member, the tension member elongates and urges the distal member to move toward the proximal member; and 
 a shaft extending from the proximal end to the distal end, the shaft comprising a cannula sized to receive a guidewire; 
   wherein:
 the proximal member and the distal member define a longitudinal axis; 
 the distal member comprises a distal engagement surface facing away from the longitudinal axis; 
 the proximal member comprises a proximal engagement surface facing toward the longitudinal axis; and 
 the distal engagement surface is positioned to abut the proximal engagement surface to transmit bending loads from the distal member to the proximal member without transmitting torque between the proximal member and the distal member. 
   
     
     
         16 . The bone screw of  claim 15 , wherein the proximal member comprises a shank and a head comprising head threading with a first pitch different from a second pitch of the bone-engaging threads. 
     
     
         17 . The bone screw of  claim 15 , wherein:
 the proximal member and the distal member define a longitudinal axis; and   the proximal member comprises a shank and a head comprising a proximal-most surface that is nonperpendicular to the longitudinal axis.   
     
     
         18 . The bone screw of  claim 15 , wherein:
 the proximal member comprises a proximal torque transmission feature distinct from the proximal engagement surface; and   the distal member comprises a distal torque transmission feature, distinct from the distal engagement surface, configured to receive torque from the proximal torque transmission feature.   
     
     
         19 . The bone screw of  claim 18 , wherein:
 the proximal torque transmission feature is in a torque transmission socket;   the distal torque transmission feature is on torque transmission protrusion that is slidably receivable within the torque transmission socket to transmit torque between the proximal member and the distal member;   the proximal torque transmission feature comprises a female spline; and   the distal torque transmission feature comprises a male spline configured to mate with the female spline.   
     
     
         20 . The bone screw of  claim 15 , wherein:
 the bone screw has a length from a proximal-most end of the proximal member to a distal-most end of the distal member;   the proximal member and the distal member cooperate to define a length limiting mechanism configured to:
 prevent the length from exceeding a maximum length; and 
 prevent the length from decreasing below a minimum length; 
   the length limiting mechanism comprises:
 a distal shoulder and a proximal shoulder, both of which are on one of the proximal member and the distal member; and 
 a stop feature on the other of the proximal member and the distal member; and 
   the stop feature is positioned between the distal shoulder and the proximal shoulder to define the minimum length and the maximum length by abutting the stop feature against the distal shoulder and the proximal shoulder.   
     
     
         21 . The bone screw of  claim 20 , wherein:
 the distal shoulder and the proximal shoulder are on the distal member;   the stop feature is on the proximal member;   the stop feature abuts the distal shoulder to define the minimum length; and   the stop feature abuts the proximal shoulder to define the maximum length.