The biomechanical changes of facet joint violation after transforaminal lumbar interbody fusion combined with decompression surgery: a finite element study

Abstract

Introduction: Facet joint violation (FJV) is a common complication of intervertebral fusion surgery, altering the load-bearing capability of the facet joints and ultimately contributing to segmental instability. Furthermore, adjacent segment degeneration is one of the potential long-term complications following lumbar spinal intervertebral fusion. For patients with a history of lumbar intervertebral fusion who developed symptomatic spinal stenosis at adjacent segments, adjacent segment decompression surgery is a clinically viable option. The biomechanical effects of isolated decompression surgery or intervertebral fusion surgery have been relatively well established. However, the biomechanical impact of facet joint intrusion on patients who have undergone both lumbar intervertebral fusion and adjacent segment decompression remains unclear.

Methods: The L4-L5 intervertebral fusion model (F) and the L3-L4 decompression with L4-L5 intervertebral fusion model (DF) were developed based on a validated intact L3-L5 model (I). On the basis of DF model, six FJV models were created according to the extent and grades of facet joint violation: left mild violation (LMV), left severe violation (LSV), right mild violation (RMV), right severe violation (RSV), bilateral mild violation (BMV), and bilateral severe violation (BSV). In each scenario, the range of motion (ROM) and intradiscal pressure (IDP) at the supra-adjacent segments were analyzed.

Results: The results indicated that both decompression and intervertebral fusion surgeries increased the ROM and intradiscal stress on the L3-L4 intervertebral discs. Additionally, the presence of facet joint violation further increased the ROM and intradiscal pressure on the L3-L4 segment, with these changes being associated with the grades and extent of facet joint violation, particularly when decompression and violation occurred on the same side.

Discussion: This study revealed that decompression or facet joint violation could elevate intradiscal pressure and ROM at the supra-adjacent segment, indicating a potential synergistic interaction between these two risk factors.

Keywords: adjacent segment degeneration; decompression; facet joint violation; finite element; transforaminal lumbar interbody fusion.

FIGURE 1

The intact finite element models of L3-L5. (A) Posterior view; (B) Anterior view; (C) Lateral view. (D) The intervertebral disc of L4/5 after TLIF surgery; (E) The posterior view of the finite element model after TLIF surgery; (F) The posterior view of the finite element model after TLIF and decompression surgery. ALL, anterior longitudinal ligament; PLL, posterior longitudinal ligament; CL, capsular ligament; LF, ligamentum flavum; ISL, interspinous ligament; IL, intertransverse ligaments; and SSL, supraspinal ligament.

FIGURE 2

Criteria for grading violation of facet joint. (a) Screws were not in the facet joint and did not encroach the facet joint; (b) Screws encroached the lateral facet but did not enter the facet joint; (c) Screws passed through the articular surface of the facet joint.

FIGURE 3

Comparison of range of motion between the current intact model and previous studies.

FIGURE 4

(A) The ROM in the I, F and DF models under loading conditions of flexion, extension, left bending, right bending, left torsion and right torsion. (B) The ROM in the DF, LMV, LSV, RMV, RSV, BMV and BSV models under the six loading conditions. (C) The ROM in the cDF, cLMV, cLSV, cRMV, cRSV, cBMV and cBSV models under the six loading conditions. ROM, range of motion. I, the intact model without surgery. F, L4-L5 intervertebral fusion model. DF, L3-L4 hemi-laminectomy and L4-L5 intervertebral fusion were both performed on the left side. LMV, left mild violation. LSV, left severe violation. RMV, right mild violation. RSV, right severe violation. BMV, bilateral mild violation. BSV, bilateral severe violation. cDF, L3-L4 hemi-laminectomy was performed on the left side and L4-L5 intervertebral fusion was performed on the contralateral side. cLMV, left mild violation. cLSV, left severe violation. cRMV, right mild violation. cRSV), right severe violation. cBMV, bilateral mild violation. cBSV, bilateral severe violation.

FIGURE 5

(A) The IDP at L3-L4 in the I, F and DF models under loading conditions of flexion, extension, left bending, right bending, left torsion and right torsion. (B) The IDP at L3-L4 in the DF, LMV, LSV, RMV, RSV, BMV and BSV models under the six loading conditions. (C) The IDP at L3-L4 in the cDF, cLMV, cLSV, cRMV, cRSV, cBMV and cBSV models under the six loading conditions. IDP, intradiscal pressure. I, the intact model without surgery. F, L4-L5 intervertebral fusion model. DF, L3-L4 hemi-laminectomy and L4-L5 intervertebral fusion were both performed on the left side. cDF, L3-L4 hemi-laminectomy was performed on the left side and L4-L5 intervertebral fusion was performed on the contralateral side. LMV, left mild violation. LSV, left severe violation. RMV, right mild violation. RSV, right severe violation. BMV, bilateral mild violation. BSV, bilateral severe violation. cLMV, left mild violation. cLSV, left severe violation. cRMV, right mild violation. cRSV), right severe violation. cBMV, bilateral mild violation. cBSV, bilateral severe violation.

FIGURE 6

Von Mises stress distribution at L3/4 with the L3-L4 hemi-laminectomy and L4-L5 intervertebral fusion were both performed on the left side. I, the intact model without surgery. F, L4-L5 intervertebral fusion model. DF, L3-L4 hemi-laminectomy and L4-L5 intervertebral fusion were both performed on the left side. LMV, left mild violation. LSV, left severe violation. RMV, right mild violation. RSV, right severe violation. BMV, bilateral mild violation. BSV, bilateral severe violation.

FIGURE 7

Von Mises stress distribution at L3/4 with the L3-L4 hemi-laminectomy was performed on the left side and L4-L5 intervertebral fusion was performed on the contralateral side. cDF, L3-L4 hemi-laminectomy was performed on the left side and L4-L5 intervertebral fusion was performed on the contralateral side. cLMV, left mild violation. cLSV, left severe violation. cRMV, right mild violation. cRSV), right severe violation. cBMV, bilateral mild violation. cBSV, bilateral severe violation.