The results of intradiscal pressure (IDP) in flexion.

<p>Percentage change of IDPs in flexion between the two PLIF models (A). Percentage change = (Data of surgical model - Data of intact model)/Data of intact model ×100%. Contour plots of IDP at (B) L3-L4 and (C) L5-S1 levels.</p

Preserving Posterior Complex Can Prevent Adjacent Segment Disease following Posterior Lumbar Interbody Fusion Surgeries: A Finite Element Analysis

<div><p>Objective</p><p>To investigate the biomechanical effects of the lumbar posterior complex on the adjacent segments after posterior lumbar interbody fusion (PLIF) surgeries.</p><p>Methods</p><p>A finite element model of the L1–S1 segment was modified to simulate PLIF with total laminectomy (PLIF-LAM) and PLIF with hemilaminectomy (PLIF-HEMI) procedures. The models were subjected to a 400N follower load with a 7.5-N.m moment of flexion, extension, torsion, and lateral bending. The range of motion (ROM), intradiscal pressure (IDP), and ligament force were compared.</p><p>Results</p><p>In Flexion, the ROM, IDP and ligament force of posterior longitudinal ligament, intertransverse ligament, and capsular ligament remarkably increased at the proximal adjacent segment in the PLIF-LAM model, and slightly increased in the PLIF-HEMI model. There was almost no difference for the ROM, IDP and ligament force at L5-S1 level between the two PLIF models although the ligament forces of ligamenta flava remarkably increased compared with the intact lumbar spine (INT) model. For the other loading conditions, these two models almost showed no difference in ROM, IDP and ligament force on the adjacent discs.</p><p>Conclusions</p><p>Preserved posterior complex acts as the posterior tension band during PLIF surgery and results in less ROM, IDP and ligament forces on the proximal adjacent segment in flexion. Preserving the posterior complex during decompression can be effective on preventing adjacent segment degeneration (ASD) following PLIF surgeries.</p></div

The results of range of motion (ROM) in flexion.

<p>(A) Range of motion (ROM) in flexion among the intact (INT) model and the two posterior lumbar interbody fusion (PLIF) models, and (B) percentage change in ROM between the two PLIF models during flexion. Percentage change = (Data of surgical model—Data of intact model)/Data of intact model ×100%.</p

Results of the ligament forces at the L3-L4 and L5-S1 levels in flexion.

<p>Percentage change in the ligament forces at the L3-L4 (A) and L5-S1 (B) levels in flexion. Percentage change = (Data of surgical model—Data of intact model)/Data of intact model ×100%.</p

The ROM among three models in each loading condition.

<p>The ROM among three models in each loading condition.</p

Material properties used in finite element model of the lumbar spine.

<p>Material properties used in finite element model of the lumbar spine.</p

Comparison of Motion between the current intact model and the previous study of Renner et al.

<p>Comparison of Motion between the current intact model and the previous study of Renner et al.</p

Cage and cross-sectional view of the posterior lumbar interbody fusion model.

<p>(A) Lateral view of the polyetheretherketone (PEEK) cage, and (B) cross-sectional view of the posterior lumbar interbody fusion model with one diagonally placed PEEK cage.</p

Finite element models of posterior lumbar interbody fusion.

<p>(A) Posterior and (B) lateral view of the posterior lumbar interbody fusion with total laminectomy (PLIF-LAM) model, and (C) posterior (D) and lateral view of the PLIF with hemilaminectomy (PLIF-HEMI) model.</p