12. A spinal fixation system, comprising: a bone anchor having a bone-engaging portion and a spinal fixation element receiving portion with opposed arms configured to receive a spinal fixation element therebetween; a connecting member having first and second ends with a spanning portion extending therebetween; a connecting assembly having a distal surface that bears against a proximal terminal end surface of each of the opposed arms of the rod receiving portion of the bone anchor and a receiving portion that is configured to receive a portion of the connecting member.
12. A spinal fixation system, comprising: a bone anchor having a bone-engaging portion and a spinal fixation element receiving portion with opposed arms configured to receive a spinal fixation element therebetween; a connecting member having first and second ends with a spanning portion extending therebetween; a connecting assembly having a distal surface that bears against a proximal terminal end surface of each of the opposed arms of the rod receiving portion of the bone anchor and a receiving portion that is configured to receive a portion of the connecting member. 16. The system of claim 12 , wherein the connecting member is a spinal rod of a substantially uniform thickness.