Many techniques evolved since then, from wiring, rods, pedicle screws, and recently inter-spinous fixation devices like the Aspen. Along its evolutionary trail, various methods for achieving circumferential fusion have arisen. Distinct from staged anterior/posterior fusion techniques, two methods of achieving an interbody fusion from a posterior approach have emerged: posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF). Recently, the lateral approach for interbody fusion (XLIF) has became a more common technique, requiring in some cases, complemental posterior fixation with pedicle screws, facet screws or interspinous fixation devices like the Aspen device.