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 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
Pseudarthorosis
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 postoperatively
Resolution of type I endplate marrow or conversion to type II
No motion on flexion/extension radiographs
However
Geometry of pseudarthorosis 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 postoperatively
Stability provided by instrumentation may prevent motion on flexion/extension films, despite pseudarthorosis
2-3° motion may be present with fusion due to compliance of normal bone
Pedicle screw fracture can be seen with pseudarthorosis
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 pseudarthorosis
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 first 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 patient's neurologic status
Poor neurologic exam after decompressive surgery may require immediate return to 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
Eisenmenger L et al: Postoperative spine: what the surgeon wants to know. Radiol Clin North Am. 57(2):415-38, 2019
Bellini M et al: Neuroimaging of the postoperative spine. Magn Reson Imaging Clin N Am. 24(3):601-20, 2016
Wait SD et al: Prospective observational study of acute postlumbar laminectomy MRI. J Neurosurg Spine. 20(1):41-4, 2014
Willson MC et al: Postoperative spine complications. Neuroimaging Clin N Am. 24(2):305-26, 2014
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
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
Rutherford EE et al: Lumbar spine fusion and stabilization: hardware, techniques, and imaging appearances. Radiographics. 27(6):1737-49, 2007
Williams AL et al: CT evaluation of lumbar interbody fusion: current concepts. AJNR Am J Neuroradiol. 26(8):2057-66, 2005
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
Ross JS: Magnetic resonance imaging of the postoperative spine. Semin Musculoskelet Radiol. 4(3):281-91, 2000
Lonstein JE et al: Complications associated with pedicle screws. J Bone Joint Surg Am. 81(11):1519-28, 1999
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
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
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Related Differential Diagnoses
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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 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
Pseudarthorosis
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 postoperatively
Resolution of type I endplate marrow or conversion to type II
No motion on flexion/extension radiographs
However
Geometry of pseudarthorosis 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 postoperatively
Stability provided by instrumentation may prevent motion on flexion/extension films, despite pseudarthorosis
2-3° motion may be present with fusion due to compliance of normal bone
Pedicle screw fracture can be seen with pseudarthorosis
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 pseudarthorosis
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 first 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 patient's neurologic status
Poor neurologic exam after decompressive surgery may require immediate return to 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
Eisenmenger L et al: Postoperative spine: what the surgeon wants to know. Radiol Clin North Am. 57(2):415-38, 2019
Bellini M et al: Neuroimaging of the postoperative spine. Magn Reson Imaging Clin N Am. 24(3):601-20, 2016
Wait SD et al: Prospective observational study of acute postlumbar laminectomy MRI. J Neurosurg Spine. 20(1):41-4, 2014
Willson MC et al: Postoperative spine complications. Neuroimaging Clin N Am. 24(2):305-26, 2014
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
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
Rutherford EE et al: Lumbar spine fusion and stabilization: hardware, techniques, and imaging appearances. Radiographics. 27(6):1737-49, 2007
Williams AL et al: CT evaluation of lumbar interbody fusion: current concepts. AJNR Am J Neuroradiol. 26(8):2057-66, 2005
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
Ross JS: Magnetic resonance imaging of the postoperative spine. Semin Musculoskelet Radiol. 4(3):281-91, 2000
Lonstein JE et al: Complications associated with pedicle screws. J Bone Joint Surg Am. 81(11):1519-28, 1999
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
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
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