Pedicle screw
A pedicle screw is provided to be inserted into and fixed to a pedicle of a spinal disease patient, and more particularly, a pedicle screw in which a screw thread of a clamp screw is formed to have dents and protrusions with trapezoid cross-sections so as to form a predetermined gap with a screw thread of a fixing unit having dents and protrusions with rectangular cross-sections when the clamp screw is combined with the fixing unit, and the screw thread of the clamp screw has different pitches to disperse an external impact so as to further firmly combine the clamp screw with the fixing unit.
1. A pedicle screw comprising:
a fixing unit which comprises a U-shaped housing groove which is formed in a side of the fixing unit to be opened upward so as to house a spinal rod, a fixing screw thread which is formed at an inner surface of the U-shaped housing groove so as to have dents and protrusions with rectangular cross-sections, and a combination groove which is formed in a lower surface of the fixing unit so as to penetrate the lower surface of the fixing unit;
a screw bar which comprises a spherical joint which constitutes an upper part of the screw bar and a screw thread which is formed at an outer surface of the screw bar to be inserted into a pedicle through the combination groove of the fixing unit; and
a clamp screw which comprises a clamp screw thread which is formed at an outer surface of the clamp screw to have dents and protrusions with right-angled trapezoid cross-sections so as to form a predetermined gap with the fixing screw thread of the fixing unit when the clamp screw is combined with the fixing unit;
wherein the right-angled trapezoid cross sections of the clamp screw thread decrease in height from a distal end of the right-angled trapezoid cross sections to a proximal end of the right-angled trapezoid cross sections, wherein said proximal end of the right-angled trapezoid cross sections are adjacent the outer surface of the clamp screw.
2. The pedicle screw of claim 1 , wherein the fixing screw thread of the fixing unit has the dents and protrusions with the rectangular cross-sections, wherein corners of the dents are rounded.
3. The pedicle screw of claim 1 , wherein the clamp screw thread of the clamp screw has the dents and protrusions with the right-angled trapezoid cross-sections, wherein inclined sides of the protrusions of the clamp screw thread face upward or downward, and corners of the dents are rounded toward a central axis of the clamp screw.
4. The pedicle screw of claim 1 , wherein pitches of the clamp screw thread are decreased or increased downward the clamp screw thread.
5. A pedicle screw comprising:
a fixing unit which comprises a U-shaped housing groove which is formed in a side of the fixing unit to be opened upward so as to house a spinal rod and a fixing screw thread which is formed at an inner surface of the U-shaped housing groove so as to have dents and protrusions with rectangular cross-sections;
a screw bar which is combined with the fixing unit so as to form a single body with the fixing unit; and
a clamp screw which comprises a clamp screw thread which is formed at an outer surface of the clamp screw to have dents and protrusions with right-angled trapezoid cross-sections so as to form a predetermined gap with the fixing screw thread of the fixing unit when the clamp screw is combined with the fixing unit
wherein the right-angled trapezoid cross sections of the clamp screw thread decrease in height from a distal end of the right-angled trapezoid cross sections to a proximal end of the right-angled trapezoid cross sections, wherein said proximal end of the right-angled trapezoid cross sections are adjacent the outer surface of the clamp screw.
6. The pedicle screw of claim 5 , wherein the fixing screw thread of the fixing unit has the dents and protrusions with the rectangular cross-sections, wherein corners of the dents are rounded.
7. The pedicle screw of claim 5 , wherein the clamp screw thread of the clamp screw has the dents and protrusions with the right-angled trapezoid cross-sections, wherein inclined sides of the protrusions of the clamp screw thread face upward or downward, and corners of the dents are rounded toward a central axis of the clamp screw.
8. The pedicle screw of claim 5 wherein pitches of the clamp screw thread are decreased or increased downward the clamp screw thread.
9. The pedicle screw of claim 4 , wherein the pitch of the clamp screw thread are decreased or increased from top to bottom such that the clamp screw thread alternates per revolution between engaging an upper protrusion and a lower protrusion of the fixing screw thread.
10. The pedicle screw of claim 8 , wherein the pitch of the clamp screw thread are decreased or increased from top to bottom such that the clamp screw thread alternates per revolution between engaging an upper protrusion and a lower protrusion of the fixing screw thread.