A spinal rod is provided that includes an elongate body having first and second ends, a length and an outside diameter. The outside diameter is substantially the same size over an entirety of the length of the elongate body. A cavity extends within the elongate body over a cavity length. The cavity length is less than the overall length of the elongate body. A stiffness of the elongate body in portions containing the cavity is less than a stiffness of a portion of the elongate body not containing the cavity.
