Objective:To compare the intervertebral segmental stiffness between PLIF with one long posterolateral cage, PLIF with one posterolateral cage and facet joint fixation, and PLIF with 2 posterior cages. Methods:Twelve bovine lumbar functional spinal units were divided into 2 groups. group 1 had a long single threaded cage inserted posterolaterally on the left side by posterior approach with left unilateral facetectomy; group 2 had 2 regular length cages inserted posteriorly. Nondestructive tests were performed in pure compression, flexion, extension, lateral bending, and rotation. Test order was intact, implanted 2 sizes, and group 1 with internal fixation of facet joint screw. Results: Group 1 had a significantly higher stiffness than group 2 in pure compression, left bending, and rotation (P＜0.05). group 2 had higher stiffness values than group 1 in right bending. Increase of cage size of group 1 increased the stiffness of pure compression, extension, flexion, and decreased the stiffness of right bending and contercolockwise rotation. Cage size had no significant effect on group 2. Group 1 with fixation of facet joint screw had a significant increase in stiffness for extension, bilaleral bending, and colockwise rotation. Conclusion:Posterior lumbar interbody fusion with insertion of a single long threaded cage posterolaterally with unilateral facetectomy enables sufficient decompression while maintaining a majority of the posterior elements. Combined with a facet joint screw, adequate postoperative stability can be achieved.