A system for replacing at least a portion of a natural facet joint includes a fixation member implantable in a vertebra, an inferior facet articular surface and an inferior strut which may be formed separately from the inferior articular surface. The inferior strut has a first end securable to the fixation member and a second end which may comprise a sphere with a hemispherical surface. An attachment mechanism may include a capture feature shaped to receive the second end of the inferior strut, and the mechanism may provide an adjustable configuration, allowing polyaxial adjustment between the inferior articular surface and the second end. A locking member may be actuated to exert force on the second end to provide a locked configuration. The system may further include a superior facet joint implant with a superior articular surface shaped to articulate with the inferior articular surface.