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STUDY DESIGN: Descriptive. OBJECTIVES: Trabecular bone in the vertebrae is critical for the distribution of load and stress throughout the neuroaxis, as well as the intervertebral disk, ligamentous complex, and facet joints. The objective was to assess the stress and strain distribution of the L4-S1 spine segment by a finite element analysis. METHODS: A lumbosacral spine model was built based on a CT-Scan. Trabecular-to-cortical bone distribution, ligaments, intervertebral disk, and facet joints with cartilage were included. A perpendicular force was applied over the L4 upper terminal plate of 300 N, 460 N and 600 N in neutral, plus 5 Nm and 7.5 Nm for flexion and extension movements. Maximum principal stress and total deformation were the main studied variables. RESULTS: Trabecular bone confers resistance to axial loads on the vertebrae by elastic capacity and stress distribution. MPS and TD showed axial stress attenuation in the nucleus pulposus and longitudinal ligaments, as well as load distribution capacity. Facet joints and discontinuous ligaments showed greater TD values in flexion moments but greater MPS values in extension, conferring stability to the lumbosacral junction and axial load distribution. CONCLUSION: We propose 3 anatomical systems for axial load distribution and stress attenuation in the lumbosacral junction. Trabecular bone distributes loads, while the ligamentous-intervertebral disk transmits and attenuate axial stress. Facet joints and discontinuous ligaments act as stabilizers for flexion and extension postures. Overall, the relationship between trabecular bone, ligamentous-intervertebral disk complex and facet joints is necessary for an efficient load distribution and segmental axial stress reduction.This slide can be retrieved from the Global Spine Congress 2023.
RESUMO
Background: Posttraumatic spinal cerebrospinal fluid leak (CSFL) without neurological deficit is a rare entity. Historically, the first-line treatment is a nonsurgical approach, which includes Trendelenburg positioning, carbonic anhydrase inhibitor (acetazolamide), and subarachnoid catheter, with a high successful rate of leak correction. However, in some cases, this first-line treatment could fail, being necessary the surgical approach. Case Description: A 23-year-old male with a recent stab wound to his lumbar region, complained of positional headache and fluid outflow through his wound. On physical examination, an active CSFL was detected without evidence of neurologic deficit. Imaging studies showed a CSF collection extending from the right L4 lamina to the subcutaneous tissue. CSF studies revealed bacterial meningitis. The treatment with carbonic anhydrase inhibitors, Trendelenburg position, lumbar subarachnoid catheter, and antibiotics was initiated. Failure of conservative measures prompted a surgical treatment to resolve the CSFL. Intraoperatively, a dura mater defect was identified, and an autologous paravertebral muscle flap was used for water-tight closure of the defect. The patient recovered without further complications and with CSFL resolution. Conclusion: Even though the nonsurgical approach is the first-line of treatment of traumatic CSFL cases, failures can occur. The evidence of a CSF trajectory in imaging studies could be a predictor of treatment failure of the nonsurgical treatment. The surgical treatment as second-line treatment has outstanding results regarding CSFL correction and should be considered when the prediction rate to nonsurgical approach failure is high.
