Spine connecting rod

A spine connecting rod, comprising:

• a coupling assembly, including:
• a body, shaped as a cylinder, formed by detachably connecting a first cylindrical coupling part and a second cylindrical coupling part, the body having a body axis parallel to a first direction;
• and
• at least one elastic part, shaped as a cylinder, detachably disposed inside the body and configured to provide a spring forcing parallel to the first direction;
• a first rod, pivotally connected with the coupling assembly, having a first axis, a diameter of the first rod being smaller than an inner diameters of the at least one elastic part and an inner diameter of the first cylindrical coupling part, one end of the first rod being provided with a ball having a center located at the first axis, a diameter of the ball being greater than the diameter of the first rod, the diameter of the ball being greater than the of inner diameters of both the at least one elastic part and the second cylindrical coupling part, wherein the ball is rotatably disposed inside the coupling assembly and sandwiched between the first cylindrical coupling part and the second cylindrical coupling part, and at least one elastic part is sleeved around the ball abutting against the at least one elastic part;
• and
• a second rod, detachably connected with the coupling assembly, having a second axis, wherein one end of the second rod along the second axis is provided with a second external thread, the second cylindrical coupling part is provided with a second internal thread such that the second rod is threadingly engaged with the second cylindrical coupling part and the second rod is detachably connected with the second cylindrical coupling part without contacting the at least one elastic part;
• wherein the first rod and the second rod protrude out of the first coupling part and the second coupling part, respectively, the first axis and the second axis are both parallel to the first direction, the ball of the first rod is rotationally disposed inside the coupling assembly so as to allow the first rod to rotate or/and swing about the ball, and the first rod is able to undergo elastic movements parallel to the first direction by the spring forcing provided by the at least one elastic part.