A spinal fixation system comprised of a bone mounting device, a support rod, and an attachment assembly interconnecting the bone mounting device to the support rod. The bone mounting device can include either bone screws configured to be screwed into the pedicle region of a vertebral body in the patient or hook mounting devices configured to be hooked around a portion of a vertebral body. The bone mounting devices include a multi-faceted connecting surface which is generally a crosshatched surface. The attachment assembly includes a housing having two openings for the support rod and a cam core member which has an eyebolt opening which is positioned in the housing so the support rod extends through the housing openings and the eyebolt opening. The cam core member also has a shaft on which the bone mounting device is positioned as well as a locking cap. The locking cap secures the bone mounting member to the shaft with the first multi-faceted connecting surface interlocking with a second multi-faceted connecting surface on either the housing or the locking cap or both. The multi-faceted connecting surfaces are configured to permit the bone mounting device to be mounted over a range of positions normal to, and over a range of rotational positions about, the shaft of the cam core member.