A modular head-to-head cross connector or construct extension system comprising a fastener element driven into a bone in a first orientation, a first U-shaped body operable to receive the fastener element and operable to receive a first rod in a first rod receiving channel, and a first compression element driven adjacent to and against the first rod in the first rod receiving channel, thereby engaging the first rod against the fastener element in a second orientation independent of the first orientation of the fastener element. The system further comprises a second U-shaped body operable to receive first compression element and operable to receive a second rod in a second rod receiving channel, and a second compression element driven adjacent to and against the second rod in the second rod receiving channel, thereby engaging the second rod against the first compression element in a third orientation independent of the second orientation.