=====Unilateral pedicle screw fixation=====
{{::translaminar_facet_screw.jpg|}}

Three [[instrumentation]] systems were tested randomly: unilateral [[pedicle screw]] (UPS), UPS with [[contralateral translaminar facet screw]] (UPSFS), and bilateral pedicle screw (BPS). 

The range of motion (ROM) and the neutral zone (NZ) of L3-5 were measured. 

All fixation types could reduce the ROM of L3-5 significantly in flexion, extension, and lateral bending, compared with the intact state. In [[axial torsion]], only BPS reduced the ROM significantly, compared with the intact state. The UPSFS technique provided intermediate stability, which was superior to the UPS in flexion-extension and lateral bending, and inferior to the BPS in lateral bending. Compared with the intact state, the NZs decreased significantly for UPS, UPSFS, and BPS in flexion-extension, while not significantly in lateral bending and axial torsion. 

In this study, among the 3 fixation techniques, BPS offered the highest stability, UPSFS provided intermediate stability, and UPS was the least stable for 2-level lumbar spinal disorders. UPSFS appeared to be able to offer a less invasive choice than BPS in well-selected patients with 2-level lumbar spinal disorders
((Liu F, Feng Z, Liu T, Fei Q, Jiang C, Li Y, Jiang X, Dong J. A biomechanical
comparison of 3 different posterior fixation techniques for 2-level lumbar spinal
disorders. J Neurosurg Spine. 2016 Mar;24(3):375-80. doi:
10.3171/2015.7.SPINE1534. Epub 2015 Dec 4. PubMed PMID: 26637067.
)).