| 摘要 |
A spinal fixation element includes a screw and a washer. The screw comprises an elongated body of a first diameter and the body includes a threaded portion at a distal end and a semispherical head of a second diameter at a proximal end. The second diameter is larger than the first diameter. The washer comprises a semispherical through opening of a third diameter at the top, of a fourth diameter in the middle and of a fifth diameter at the bottom. The third diameter is slightly smaller than the second diameter, the fourth diameter is slightly larger than the second diameter and the fifth diameter is smaller than the second diameter. The washer surrounds the semispherical head, is non-removably attached to the semispherical head and is rotatable and positionable at an angle relative to the elongated body. |
