Polyaxial adjustment of facet joint prostheses

An apparatus comprising:

• a first spinal prosthetic member comprising a first joint element including a first support arm attachable to a first fixation element, the first support arm moveable along its longitudinal axis with respect to the first fixation element, wherein the first fixation element comprises a spherical head and wherein the first support arm is attachable to the first fixation element via a fixing element having a concave surface that rests on top of the spherical head of the first fixation element;
• and
• a second spinal prosthetic member comprising a second joint element including a support structure attachable to a second fixation element via a connection element and articulating with said first spinal prosthetic member to form an articulating assembly, the support structure configured to receive the first support arm, wherein the second spinal prosthetic member further comprises a set screw for locking a position of the second fixation element relative to the connection element;
• wherein the support structure is configured to receive a spherical bearing surface of the first support arm thereby allowing articulation between the first joint element and the second joint element,
• wherein the support structure includes a bearing surface that is completely enclosed by a surrounding perimeter extending from the bearing surface, the perimeter defining an opening, the opening directly opposite the bearing surface, and
• wherein the support structure is rotatable relative to the second fixation element to adjust a relative orientation of the bearing surface
• wherein the second fixation element has a first longitudinal axis and the support structure has a second longitudinal axis extending through a center of the bearing surface, wherein the support structure is offset from the second fixation element such that the second longitudinal axis does not intersect the first longitudinal axis
• wherein the second longitudinal axis is substantially parallel to the first longitudinal axis when the apparatus is implanted.