Oblique Lateral Interbody Fusion Combined With Different Internal Fixations in The Treatment of Degenerative Lumbar Spine Disease: A Finite Element Analysis

Little is known about the biomechanical performance of various internal fixations in oblique lumbar interbody fusion (OLIF). In this study, finite element (FE) analysis was used to describe the biomechanical findings of various different internal fixations to compare and explore the stability of each fixation.METHODS: Six validated FE models of the L3-S1 segment were reconstructed from computed tomography images, including (1) an intact model, (2)a stand-alone (SA) model with no instrument (3) a unilateral pedicle screw model (UPS), (4) a unilateral pedicle screw contralateral translaminar facet screw model (UPS-CTLFS), (5) a bilateral pedicle screw (BPS) model, and (6) a cortical bone trajectory screw (CBT).Three-dimensional model was performed by computed tomography data, and 150N static force and 10N.m moments in different directions were applied to the models to analyze the validation of the models in comparison with previous studies. Models of the OLIF cage was created with three-dimensional scanning to improve the accuracy of the FE analysis. Range of motion (ROM) of the surgical segment stresses, stress of the cage, and stress of fixation were evaluated in the different models.RESULTS:ROM increased from least to greatest as follows: BPS, UPS-CTFS, CBT, UPS, SA. The SA group had the greatest ROM and the SA group had the greatest ROM and stresses on the CAGE. The ROM of the BPS and UPS-CTFS was not significantly different for all motion loadings. Compared with the other three models, the BPS model had lower stresses in internal fixation for all loading conditions and the CBT screw internal fixation had the highest stresses for different loads Compared with the other groups.CONCLUSIONSThe BPS model provided the best biomechanical stability for OLIF. The SA model was relatively less stable. The UPS-CFTS group reduced the ROM of the fusion segments, but the stresses on the internal fixation and CAGE were relatively higher in the UPS-CFTS Compared with the BPS group; and the CBT group had lower ROM in flexion and extension Compared with the BPS, but its ROM in rotation and lateral flexion was relatively higher. The stability of the CBT was poorer than that of the BPS and LPS-CTFS groups. The stress on the CAGE and internal fixation was greater in the CBT group.

Assessment of Paraspinal Muscle Atrophy Percentage after Minimally Invasive Transforaminal Lumbar Interbody Fusion and Unilateral Instrumentation Using a Novel Contralateral Intact Muscle-Controlled Model

<sec><title>Study Design</title><p>Retrospective comparative clinical study.</p></sec><sec><title>Purpose</title><p>This study aimed to assess paraspinal muscle atrophy in patients who underwent minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) and unilateral pedicle screw fixation using a novel contralateral intact muscle-controlled model.</p></sec><sec><title>Overview of Literature</title><p>The increased incidence of paravertebral lumbar muscle injuries after open techniques has raised the importance of implementing minimally invasive spine surgical techniques using tubular retractors and minimally invasive screw placement. The functional cross-sectional area (FCSA) represents the lean muscle mass; furthermore, FCSA is a useful marker of the contractile ability of a muscle following a spine surgery. However, the benefits of unilateral fixation and MI-TLIF on paraspinal muscles have not been defined.</p></sec><sec><title>Methods</title><p>We performed a retrospective imagenological review on eleven patients who underwent unilateral MI-TLIF and unilateral transpedicular screw lumbar placement. FCSAs of the multifidus and erector spinae were measured 1 year after surgery at adjacent levels and were compared to the contralateral intact muscles. Measurement differences between the surgical and nonsurgical sites were compared. The interobserver reliability was calculated using an intraclass correlation coefficient.</p></sec><sec><title>Results</title><p>The mean FCSA at the surgical site was 20.97±5.07 cm² at the superior level and 8.89±2.87 cm² at the inferior level. The mean FCSA at the contralateral nonsurgical site was 20.15±5.95 cm² at the superior level and 9.20±2.66 cm² at the inferior level was. The superior and inferior FCSA measurements showed no significant difference between the surgical and nonsurgical sites (<italic>p</italic>=0.5, <italic>p</italic>=0.922, respectively).</p></sec><sec><title>Conclusions</title><p>Using a mini-open tubular approach through the sulcus between the longissimus and iliocostalis, MI-TLIF and unilateral pedicle screw instrumentation produced minimal paraspinal muscle damage at the superior and inferior adjacent levels.</p></sec>