link
Bookmarks
Normal Postoperative Change, Overview
Bryson Borg, MD; Jeffrey S. Ross, MD
To access 4,300 diagnoses written by the world's leading experts in radiology, please log in or subscribe.Log inSubscribe
0
50
5
0

KEY FACTS

  • Terminology

    TERMINOLOGY

    • Definitions

      • Discectomy or partial discectomy
        • Surgical removal of herniated portion of intervertebral disc
      • Laminectomy
        • Removal of lamina to decompress spinal canal
          • Unilateral (hemilaminectomy) or bilateral
          • Partial removal of lamina and ligamentum flavum is technically a laminotomy, although terminology sometimes used interchangeably
      • 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
      • 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
      • 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 temporizing mechanism until bony union can occur
      • Malpositioned pedicle screw
        • Pedicle screw should transverse 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
      • 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 common in immediate postoperative setting
          • May have complex signal, with fluid-fluid levels
          • Will demonstrate peripheral enhancement
        • Can be difficult to differentiate from postoperative hematoma, pseudomeningocele, infected collection
        • Severity of compression by epidural fluid does not predict a patient’s neurological status
          • Poor neurological exam after decompressive surgery may require immediate return to the operating room for exploration, since immediate postoperative imaging not sufficiently sensitive to pathology
      • 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

    Selected References

    1. Wait SD et al: Prospective observational study of acute postlumbar laminectomy MRI. J Neurosurg Spine. 20(1):41-4, 2014
    2. Willson MC et al: Postoperative spine complications. Neuroimaging Clin N Am. 24(2):305-26, 2014
    3. 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
    4. 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
    5. Rutherford EE et al: Lumbar spine fusion and stabilization: hardware, techniques, and imaging appearances. Radiographics. 27(6):1737-49, 2007
    6. Williams AL et al: CT evaluation of lumbar interbody fusion: current concepts. AJNR Am J Neuroradiol. 26(8):2057-66, 2005
    7. 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
    8. Ross JS: Magnetic resonance imaging of the postoperative spine. Semin Musculoskelet Radiol. 4(3):281-91, 2000
    9. Lonstein JE et al: Complications associated with pedicle screws. J Bone Joint Surg Am. 81(11):1519-28, 1999
    10. 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
    11. 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
    Related Anatomy
    Loading...
    Related Differential Diagnoses
    Loading...
    References
    Tables

    Tables

    KEY FACTS

    • Terminology

      TERMINOLOGY

      • Definitions

        • Discectomy or partial discectomy
          • Surgical removal of herniated portion of intervertebral disc
        • Laminectomy
          • Removal of lamina to decompress spinal canal
            • Unilateral (hemilaminectomy) or bilateral
            • Partial removal of lamina and ligamentum flavum is technically a laminotomy, although terminology sometimes used interchangeably
        • 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
        • 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
        • 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 temporizing mechanism until bony union can occur
        • Malpositioned pedicle screw
          • Pedicle screw should transverse 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
        • 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 common in immediate postoperative setting
            • May have complex signal, with fluid-fluid levels
            • Will demonstrate peripheral enhancement
          • Can be difficult to differentiate from postoperative hematoma, pseudomeningocele, infected collection
          • Severity of compression by epidural fluid does not predict a patient’s neurological status
            • Poor neurological exam after decompressive surgery may require immediate return to the operating room for exploration, since immediate postoperative imaging not sufficiently sensitive to pathology
        • 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

      Selected References

      1. Wait SD et al: Prospective observational study of acute postlumbar laminectomy MRI. J Neurosurg Spine. 20(1):41-4, 2014
      2. Willson MC et al: Postoperative spine complications. Neuroimaging Clin N Am. 24(2):305-26, 2014
      3. 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
      4. 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
      5. Rutherford EE et al: Lumbar spine fusion and stabilization: hardware, techniques, and imaging appearances. Radiographics. 27(6):1737-49, 2007
      6. Williams AL et al: CT evaluation of lumbar interbody fusion: current concepts. AJNR Am J Neuroradiol. 26(8):2057-66, 2005
      7. 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
      8. Ross JS: Magnetic resonance imaging of the postoperative spine. Semin Musculoskelet Radiol. 4(3):281-91, 2000
      9. Lonstein JE et al: Complications associated with pedicle screws. J Bone Joint Surg Am. 81(11):1519-28, 1999
      10. 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
      11. 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