This invention relates to interconnection assemblies for use with spinal fixation systems to treat spinal defects. The interconnection assemblies can include various spinal rod connecting members and interconnecting elements to secure the spinal rod connecting members to each other in variable orientations and lengths. The interconnection assemblies can be adjusted to minimize interference with the spinal column, bony processes, and associated neural, muscular, and ligament components of the spine all the while exhibiting a low profile. The interconnecting elements and related components can be provided as a completely assembled unit that does not inadvertently become disassembled prior to or during implantation.