Abstract
The oblique lateral locking plate system (OLLPS) is a novel internal fixation with a locking and reverse pedicle track screw configuration designed for oblique lumbar interbody fusion (OLIF). The OLLPS is placed in a single position through the oblique lateral surgical corridor to reduce operative time and complications associated with prolonged anesthesia and prone positioning. The purpose of this study was to verify the biomechanical effect of the OLLPS. An intact finite element model of L1-S1 (intact) was established based on computed tomography images of a healthy male volunteer. The L4-L5 intervertebral space was selected as the surgical segment. The surgical models were established separately based on OLIF surgical procedures and different internal fixations: 1) stand-alone OLIF (SA); 2) OLIF with a 2-screw lateral plate; 3) OLIF with a 4-screw lateral plate; 4) OLIF with OLLPS; and 5) OLIF with bilateral pedicle screw fixation (BPS). After validation of the intact model, physiologic loads were applied to the superior surface of L1 to simulate motions such as flexion, extension, left bending, right bending, left rotation, and right rotation. The evaluation indices included the L4/5 range of motion, the L4 maximum displacement, and the maximum stresses of the superior and inferior end plates, the cage, and the supplemental fixation. During OLIF surgery, the OLLPS provided multiplanar stability similar to that provided by BPS. Compared with 2-screw lateral plate and 4-screw lateral plate, OLLPS had better biomechanical properties in terms of enhancing the instant stability of the surgical segment, reducing the stress on the superior and inferior end plates of the surgical segment, and decreasing the risk of cage subsidence. With a minimally invasive background, the OLLPS can be used as an alternative to BPS in OLIF and it has better prospects for clinical promotions and applications.
Highlights
Advances in minimally invasive technology open up a new era of spine surgery
The L1-S1 segment range of motion (ROM) for different motions of the intact model under a 150 N axial compression preload and a 10N·m moment load was measured and compared with the outcomes of in the vitro experiment conducted by Yamamoto et al.[26] (Table 2)
The total L1-L5 ROM of the intact model in flexion-extension, lateral bending, and rotational mobility was measured by applying a 7.5 N·m moment load and compared with the finite element model investigated in Dreischarf et al.[27] (Fig. 5A)
Summary
Advances in minimally invasive technology open up a new era of spine surgery. Oblique lumbar interbody fusion (OLIF) is widely used in the treatment of degenerative diseases of the lumbar spine because of its advantages such as minimally invasive indirect decompression, efficient interbody fusion and rapid postoperative rehabilitation. A clinical study by Abe et al.[2] reported a 9.03% rate of cage subsidence. Zeng et al.[3] found a subsidence rate up to 19.8% in patients who underwent standalone OLIF surgery during postoperative follow-up. Indirect decompression failure after cage subsidence may cause a range of clinical symptoms, high reoperation rate, huge financial and health burden. In patients with a high risk of cage subsidence, OLIF with supplementary fixation may be a more prudent solution
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