Screw assembly for spinal implant

A screw assembly for a spinal implant, comprising:

• a first unit including insertion holes positioned opposite each other, cut from an edge of an upper end of the first unit, the first unit forming an inner space, and the first unit penetrated from top to bottom, wherein the first unit further comprises:
• a linear groove depressed in parallel with an upper portion of the first unit along an outer circumference surface of the first unit;
• a first hole depressed into a preset depth and a preset size in the outer circumference surface of the first unit to be positioned in a lower portion of the first unit;
• and
• second holes, having a rectangular shape, positioned between the linear groove and the first hole, and depressed from both edges of each of the insertion holes positioned opposite each other to be disposed along an outer surface of the first unit;
• a rod having a side whose outer circumference surface is positioned on the insertion holes of the first unit and another side whose outer circumference surface is positioned on insertion holes of another first unit positioned adjacent to the first unit;
• a second unit having an upper portion rotatably received in a lower portion of the inner space and a lower portion configured to be screwed into a vertebral body of a spine so s not to be released from the spine;
• a third unit screwed to an upper portion of the inner space to hold the rod;
• a fourth unit positioned between the inner space and the upper portion of the second unit to restrict a rotation of the second unit and including a pressure cap seated in the inner space while pressing an outer surface of an upper portion of a ball joint head disposed on the upper portion of the second unit and having an upper portion contacting the outer circumference surface of the rod to be pressurized by a coupling force of the third unit coupled with the first unit;
• and
• a fifth unit enabling the pressure cap of the fourth unit to be inserted into the first unit and including a C-ring preventing the inserted pressure cap from escaping off.