Cannulated telescopic femoral neck screw device and related fixation method

Abstract

A screw assembly and method developed for the fixation of femoral neck fractures without interruption of the growth process is disclosed. The screw assembly includes a male component that is attached to the lateral cortex and a female component that is attached at the proximal epiphysis. Anchorage of the components is achieved through screw-type fixation. The screw has a built-in feature that allows for free extension of its length as the fracture site or the slipped capital physeal plate heals and normal patient growth continues. Stable fixation and rotational stability are created at the fracture (slip) site while avoiding compression forces, thus avoiding premature closure of the physeal plate.

What is claimed is: 
     
         1 . A screw assembly comprising:
 a female component including a hollow elongated shaft defining a medial threaded portion at one end of the hollow shaft and a lateral end opening at the opposite end thereof, wherein the lateral end opening is in communication with a non-cylindrically shaped channel formed along the hollow shaft;   a male component configured to be received within the non-cylindrically shaped channel of the female component, the male component including a non-cylindrical shaped shaft defining a lateral threaded portion at one end; and   a cap configured to engage the male component;   wherein the non-cylindrical shaped channel of the female component defines substantially the same cross-sectional configuration as the non-cylindrical shaped shaft of the male component such that the male component is freely slidable relative to the female component along a longitudinal axis defined by the screw assembly.   
     
     
         2 . The screw assembly of  claim 1 , wherein the male component is not rotatable relative to the female component when the female component is engaged to the male component. 
     
     
         3 . The screw assembly of  claim 1 , wherein the non-cylindrical shaped shaft of the male component and the non-cylindrical shaped channel of the female component each have a three sided cross sectional configuration or a double flat cross-sectional configuration. 
     
     
         4 . The screw assembly of  claim 1 , wherein the non-cylindrical shaped shaft of the male component and the non-cylindrical shaped channel of the female component each have a triangular, square, rectangular, or oblong cross-sectional configurations. 
     
     
         5 . The screw assembly of  claim 1 , wherein the lateral threaded portion of the male component defines a cortical-shaped profile. 
     
     
         6 . The screw assembly of  claim 1 , wherein the medial threaded portion of the female component defines a cancellous-shaped profile. 
     
     
         7 . The screw assembly of  claim 1 , wherein the medial threaded portion of the female component includes a self-tapping feature defining a flat surface area. 
     
     
         8 . The screw assembly of  claim 1 , wherein a diameter of the medial threaded portion is as large as an external diameter of the hollow elongated shaft. 
     
     
         9 . The screw assembly of  claim 1 , wherein the male component further includes a drive feature defining a hexagonal-shaped recess formed proximate the lateral threaded portion. 
     
     
         10 . The screw assembly of  claim 9 , wherein the male component defines a second lateral threaded portion formed proximate the drive feature, wherein the second lateral threaded portion is configured to engage the cap and a drive mechanism. 
     
     
         11 . The screw assembly of  claim 1 , wherein the cap comprises a middle portion with a cap portion formed at one end of the middle portion and an external threaded portion formed at the opposite end thereof. 
     
     
         12 . The screw assembly of  claim 1 , wherein the lateral threaded portion of the male component includes a self-tapping feature that defines a flat surface area. 
     
     
         13 . The screw assembly of  claim 1 , wherein the medial threaded portion of the female component defines an axial opening in communication with the non-cylindrical shaped channel. 
     
     
         14 . The screw assembly of  claim 9 , further comprising a drive mechanism configured to engage the drive feature for inserting the screw assembly into a bone. 
     
     
         15 . A screw assembly comprising:
 a female component including a hollow elongated shaft defining a lateral threaded portion at one end of the elongated hollow shaft and a medial end opening at the opposite end thereof, wherein the medial end opening is in communication with a cylindrically shaped channel formed along the elongated hollow shaft; and   a male component configured to be received within the cylindrically shaped channel of the female component, the male component including a cylindrical shaped shaft defining a medial threaded portion at one end;   wherein the cylindrical shaped channel of the female component defines substantially the same cross-sectional configuration as the cylindrical shaped shaft of the male component such that the male component is freely slidable and rotatable relative to the female component along a longitudinal axis defined by the screw assembly.   
     
     
         16 . The screw assembly of  claim 15 , wherein the lateral threaded portion of the female component defines a beveled profile.