A spine fixation system, comprising: a) a rod (12a, 12b) which is configured to extend over a portion of the spine, b) a plurality of fasteners, wherein each fastener has a longitudinal axis and is configured to be secured to a vertebra (V1, V2, V3) to be treated, c) a plurality of connectors, wherein each connector - is connected to, or is capable of being connected to, one of the fasteners, - has a seat member for receiving and fixing the rod (12a, 12b), wherein the seat member is capable of being fixed in different rotational positions with regard to a rotational axis that extends, or is capable of being positioned such that it extends, parallel to but not coinciding with the longitudinal axis of the fastener to which the respective connector is connected, - is configured such that the rod (12a, 12b) is allowed, when received in the seat member, to swivel over the fastener when the seat member rotates around the rotational axis, and - comprises a head member which is connected to, or is capable of being connected to, one of the fasteners, and which supports the seat member so as to enable at least rotational movement of the seat member with regard to the head member before the position of the seat member is fixed, wherein the head member is capable of being fixed to the fastener, to which the respective connector is connected, in different rotational positions with regard to the longitudinal axis of this fastener. a) a rod (12a, 12b) which is configured to extend over a portion of the spine, b) a plurality of fasteners, wherein each fastener has a longitudinal axis and is configured to be secured to a vertebra (V1, V2, V3) to be treated, c) a plurality of connectors, wherein each connector - is connected to, or is capable of being connected to, one of the fasteners, - has a seat member for receiving and fixing the rod (12a, 12b), wherein the seat member is capable of being fixed in different rotational positions with regard to a rotational axis that extends, or is capable of being positioned such that it extends, parallel to but not coinciding with the longitudinal axis of the fastener to which the respective connector is connected, - is configured such that the rod (12a, 12b) is allowed, when received in the seat member, to swivel over the fastener when the seat member rotates around the rotational axis, and - comprises a head member which is connected to, or is capable of being connected to, one of the fasteners, and which supports the seat member so as to enable at least rotational movement of the seat member with regard to the head member before the position of the seat member is fixed, wherein the head member is capable of being fixed to the fastener, to which the respective connector is connected, in different rotational positions with regard to the longitudinal axis of this fastener. - is connected to, or is capable of being connected to, one of the fasteners, - has a seat member for receiving and fixing the rod (12a, 12b), wherein the seat member is capable of being fixed in different rotational positions with regard to a rotational axis that extends, or is capable of being positioned such that it extends, parallel to but not coinciding with the longitudinal axis of the fastener to which the respective connector is connected, - is configured such that the rod (12a, 12b) is allowed, when received in the seat member, to swivel over the fastener when the seat member rotates around the rotational axis, and - comprises a head member which is connected to, or is capable of being connected to, one of the fasteners, and which supports the seat member so as to enable at least rotational movement of the seat member with regard to the head member before the position of the seat member is fixed, wherein the head member is capable of being fixed to the fastener, to which the respective connector is connected, in different rotational positions with regard to the longitudinal axis of this fastener.