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Normal Postoperative Change, Epidural Space
Bryson Borg, MD; Jeffrey S. Ross, MD
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KEY FACTS

  • Terminology

    • Imaging

      TERMINOLOGY

      • Definitions

        • Laminectomy
          • Removal of lamina to decompress spinal canal
            • Unilateral (hemilaminectomy) or bilateral
            • Partial removal of lamina and ligamentum flavum technically a laminotomy, although terminology sometimes used interchangeably
        • Posterior instrumentation
          • Including pedicle screws, paraspinous rods, transverse rods, laminar hooks
            • Translaminar or facet screws; can be inserted with minimally invasive techniques
        • Posterolateral fusion
          • With severe loss of disc height, in lieu of interbody fusion
          • Lateral bone graft placement, fusion of transverse processes
          • Usually supplemented by posterior instrumentation
        • Peridural fibrosis
          • Some degree of peridural fibrosis along margin of thecal sac is typical finding following discectomy
            • Edema and tissue disruption at discectomy site particularly conspicuous in 1st 6 weeks postoperatively
              • Can simulate disc residual/recurrent disc herniation
          • Scarring has been implicated with nerve root irritation in failed back surgery syndrome (FBSS)
        • Postoperative fluid collection
          • Fluid collection in operative bed is not uncommon in immediate postoperative setting
            • May have complex signal
            • May have fluid-fluid levels
            • May demonstrate peripheral enhancement
          • Can be difficult to differentiate from postoperative hematoma, pseudomeningocele, infected collection
        • Malpositioned pedicle screw
          • Pedicle screw should traverse pedicle and be securely positioned within vertebral body
          • Malpositioning includes
            • Perforation of anterior cortex of vertebral body
            • Perforation of cortex of pedicle
              • ± compromise of intervertebral neural foramen or spinal canal
        • Lucency around pedicle screw
          • Clear zones (≥ 1 mm) around pedicle screws may be encountered on postoperative radiographs
            • Traditionally, concerning for loosening or infection
          • 1 longitudinal series describes majority (2/3) of clear zones as resolving over several years
            • Persistence 2 years postoperatively predictive of pseudoarthrosis

      IMAGING

      • Imaging Recommendations

        Selected References

        1. Yang H et al: MRI manifestations and differentiated diagnosis of postoperative spinal complications. J Huazhong Univ Sci Technolog Med Sci. 29(4):522-6, 2009
        2. Tokuhashi Y et al: Clinical course and significance of the clear zone around the pedicle screws in the lumbar degenerative disease. Spine (Phila Pa 1976). 33(8):903-8, 2008
        3. Rutherford EE et al: Lumbar spine fusion and stabilization: hardware, techniques, and imaging appearances. Radiographics. 27(6):1737-49, 2007
        4. Williams AL et al: CT evaluation of lumbar interbody fusion: current concepts. AJNR Am J Neuroradiol. 26(8):2057-66, 2005
        5. Carmouche JJ et al: Epidural abscess and discitis complicating instrumented posterior lumbar interbody fusion: a case report. Spine (Phila Pa 1976). 29(23):E542-6, 2004
        6. Ross JS: Magnetic resonance imaging of the postoperative spine. Semin Musculoskelet Radiol. 4(3):281-91, 2000
        7. Lonstein JE et al: Complications associated with pedicle screws. J Bone Joint Surg Am. 81(11):1519-28, 1999
        8. Fritsch EW et al: The failed back surgery syndrome: reasons, intraoperative findings, and long-term results: a report of 182 operative treatments. Spine (Phila Pa 1976). 21(5):626-33, 1996
        9. Larsen JM et al: Assessment of pseudarthrosis in pedicle screw fusion: a prospective study comparing plain radiographs, flexion/extension radiographs, CT scanning, and bone scintigraphy with operative findings. J Spinal Disord. 9(2):117-20, 1996
        10. Ross JS: Magnetic resonance assessment of the postoperative spine. Degenerative disc disease. Radiol Clin North Am. 29(4):793-808, 1991
        11. Ross JS et al: Lumbar spine: postoperative assessment with surface-coil MR imaging. Radiology. 164(3):851-60, 1987
        12. Ross JS et al: Postoperative cervical spine: MR assessment. J Comput Assist Tomogr. 11(6):955-62, 1987
        Related Anatomy
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        Related Differential Diagnoses
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        References
        Tables

        Tables

        KEY FACTS

        • Terminology

          • Imaging

            TERMINOLOGY

            • Definitions

              • Laminectomy
                • Removal of lamina to decompress spinal canal
                  • Unilateral (hemilaminectomy) or bilateral
                  • Partial removal of lamina and ligamentum flavum technically a laminotomy, although terminology sometimes used interchangeably
              • Posterior instrumentation
                • Including pedicle screws, paraspinous rods, transverse rods, laminar hooks
                  • Translaminar or facet screws; can be inserted with minimally invasive techniques
              • Posterolateral fusion
                • With severe loss of disc height, in lieu of interbody fusion
                • Lateral bone graft placement, fusion of transverse processes
                • Usually supplemented by posterior instrumentation
              • Peridural fibrosis
                • Some degree of peridural fibrosis along margin of thecal sac is typical finding following discectomy
                  • Edema and tissue disruption at discectomy site particularly conspicuous in 1st 6 weeks postoperatively
                    • Can simulate disc residual/recurrent disc herniation
                • Scarring has been implicated with nerve root irritation in failed back surgery syndrome (FBSS)
              • Postoperative fluid collection
                • Fluid collection in operative bed is not uncommon in immediate postoperative setting
                  • May have complex signal
                  • May have fluid-fluid levels
                  • May demonstrate peripheral enhancement
                • Can be difficult to differentiate from postoperative hematoma, pseudomeningocele, infected collection
              • Malpositioned pedicle screw
                • Pedicle screw should traverse pedicle and be securely positioned within vertebral body
                • Malpositioning includes
                  • Perforation of anterior cortex of vertebral body
                  • Perforation of cortex of pedicle
                    • ± compromise of intervertebral neural foramen or spinal canal
              • Lucency around pedicle screw
                • Clear zones (≥ 1 mm) around pedicle screws may be encountered on postoperative radiographs
                  • Traditionally, concerning for loosening or infection
                • 1 longitudinal series describes majority (2/3) of clear zones as resolving over several years
                  • Persistence 2 years postoperatively predictive of pseudoarthrosis

            IMAGING

            • Imaging Recommendations

              Selected References

              1. Yang H et al: MRI manifestations and differentiated diagnosis of postoperative spinal complications. J Huazhong Univ Sci Technolog Med Sci. 29(4):522-6, 2009
              2. Tokuhashi Y et al: Clinical course and significance of the clear zone around the pedicle screws in the lumbar degenerative disease. Spine (Phila Pa 1976). 33(8):903-8, 2008
              3. Rutherford EE et al: Lumbar spine fusion and stabilization: hardware, techniques, and imaging appearances. Radiographics. 27(6):1737-49, 2007
              4. Williams AL et al: CT evaluation of lumbar interbody fusion: current concepts. AJNR Am J Neuroradiol. 26(8):2057-66, 2005
              5. Carmouche JJ et al: Epidural abscess and discitis complicating instrumented posterior lumbar interbody fusion: a case report. Spine (Phila Pa 1976). 29(23):E542-6, 2004
              6. Ross JS: Magnetic resonance imaging of the postoperative spine. Semin Musculoskelet Radiol. 4(3):281-91, 2000
              7. Lonstein JE et al: Complications associated with pedicle screws. J Bone Joint Surg Am. 81(11):1519-28, 1999
              8. Fritsch EW et al: The failed back surgery syndrome: reasons, intraoperative findings, and long-term results: a report of 182 operative treatments. Spine (Phila Pa 1976). 21(5):626-33, 1996
              9. Larsen JM et al: Assessment of pseudarthrosis in pedicle screw fusion: a prospective study comparing plain radiographs, flexion/extension radiographs, CT scanning, and bone scintigraphy with operative findings. J Spinal Disord. 9(2):117-20, 1996
              10. Ross JS: Magnetic resonance assessment of the postoperative spine. Degenerative disc disease. Radiol Clin North Am. 29(4):793-808, 1991
              11. Ross JS et al: Lumbar spine: postoperative assessment with surface-coil MR imaging. Radiology. 164(3):851-60, 1987
              12. Ross JS et al: Postoperative cervical spine: MR assessment. J Comput Assist Tomogr. 11(6):955-62, 1987