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

  • Terminology

    • Imaging

      TERMINOLOGY

      • Definitions

        • Discectomy or partial discectomy
          • Surgical removal of herniated portion of intervertebral disc
        • Interbody fusion
          • Disc removal by posterior (posterior lumbar intervertebral fusion [PLIF]) or anterior (anterior lumbar intervertebral fusion [ALIF]) approach
          • Insertion of bone graft &/or fusion hardware
          • Goal is arthrodesis (fusion) across disc space
        • Disc replacement
          • Variety of intervertebral hardware
          • Preserves motion across segment: Arthroplasty rather than arthrodesis
        • Pseudoarthrosis
          • Failure to obtain bony union after fusion
          • Ideally, fused segment will show
            • Mature bridging bone on radiographs, CT
            • Cold on bone scan 6-12 months postop
            • Resolution of type I endplate marrow or conversion to type II
            • No motion on flexion-extension radiographs
          • However
            • Geometry of pseudoarthrosis may be complex and difficult to appreciate on radiographs, CT
            • Bone scan performs poorly, with significant false-negative and false-positive findings
              • Somewhat better performance at 12 months relative to 6 months postop
            • Stability provided by instrumentation may prevent motion on flexion-extension films, despite pseudoarthrosis
              • 2-3° motion may be present with fusion due to compliance of normal bone
            • Pedicle screw fracture can be seen with pseudoarthrosis
              • Instrumentation is temporizing mechanism until bony union can occur
        • 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
        • Nerve root clumping, enhancement
          • Transient nerve root clumping can be identified in early postoperative period, often resolves spontaneously
          • Solitary nerve root enhancement may be seen perioperatively; inflammation related to compression, manipulation

      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

              • Discectomy or partial discectomy
                • Surgical removal of herniated portion of intervertebral disc
              • Interbody fusion
                • Disc removal by posterior (posterior lumbar intervertebral fusion [PLIF]) or anterior (anterior lumbar intervertebral fusion [ALIF]) approach
                • Insertion of bone graft &/or fusion hardware
                • Goal is arthrodesis (fusion) across disc space
              • Disc replacement
                • Variety of intervertebral hardware
                • Preserves motion across segment: Arthroplasty rather than arthrodesis
              • Pseudoarthrosis
                • Failure to obtain bony union after fusion
                • Ideally, fused segment will show
                  • Mature bridging bone on radiographs, CT
                  • Cold on bone scan 6-12 months postop
                  • Resolution of type I endplate marrow or conversion to type II
                  • No motion on flexion-extension radiographs
                • However
                  • Geometry of pseudoarthrosis may be complex and difficult to appreciate on radiographs, CT
                  • Bone scan performs poorly, with significant false-negative and false-positive findings
                    • Somewhat better performance at 12 months relative to 6 months postop
                  • Stability provided by instrumentation may prevent motion on flexion-extension films, despite pseudoarthrosis
                    • 2-3° motion may be present with fusion due to compliance of normal bone
                  • Pedicle screw fracture can be seen with pseudoarthrosis
                    • Instrumentation is temporizing mechanism until bony union can occur
              • 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
              • Nerve root clumping, enhancement
                • Transient nerve root clumping can be identified in early postoperative period, often resolves spontaneously
                • Solitary nerve root enhancement may be seen perioperatively; inflammation related to compression, manipulation

            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