A rupture of the ligament between skaphoid and lunatum is called SL dissoziation. The distance between skaphoid and lunatum increases, the lunatum doesn't result anymore bilanced between flexion and extension and assumes a position in dorsal rotation called DISI. This reduces the heigth of the carpum and is called carpum collapse.
- The ligament from the lunatum to the skaphoid pulls the lunatum in a flexion position.
- The ligament from the lunatum to the triquetrum pulls the lunatum in an extended position.
So after the rupture of the ligaments from the lunatum to the skaphoid, there are still the ligaments to the triquetrum, pulling the lunatum in an extension position and we havgete the Disi deformity.
The video you can see the opening of the space between lunatum and skaphoid in a case of successive ligament repair.