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DOI: 10.1148/rg.273065055
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Right arrow Musculoskeletal Radiology

Complications of Spinal Instrumentation1

Phillip M. Young, MD, Thomas H. Berquist, MD, Laura W. Bancroft, MD, and Jeffrey J. Peterson, MD

1 From the Department of Radiology, Mayo Clinic, 2400 San Pablo Rd, Jacksonville, FL 32224. Recipient of a Certificate of Merit award for an education exhibit at the 2005 RSNA Annual Meeting. Received April 5, 2006; revision requested August 9; revision received September 29 and accepted October 10. All authors have no financial relationships to disclose.

Figure 1A
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  		Figure 1a.  The three columns of the spine. Axial CT image (a) and lateral radiograph (b) with color overlay show the anterior (red), middle (blue), and posterior (green) columns in a normal patient.

 

Figure 1B
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  		Figure 1b.  The three columns of the spine. Axial CT image (a) and lateral radiograph (b) with color overlay show the anterior (red), middle (blue), and posterior (green) columns in a normal patient.

 

Figure 2
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  		Figure 2.  Two-column instability. Anteroposterior radiograph shows instability above the level of successful fusion in a 61-year-old woman who underwent laminectomies at L1 through L5 and posterior lumbar interbody fusion at L4 through S1.

 

Figure 3
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  		Figure 3.  Combined anterior and posterior fusion of the cervical spine. Lateral radiograph demonstrates an anterior column reconstruction with a fibular allograft and an anterior plate and screws after vertebral body resection (corpectomy) at multiple levels, as well as a posterior column reconstruction with articular pillar screws and rods. The structural integrity of the anterior and posterior columns made reconstruction of the middle column unnecessary.

 

Figure 4
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  		Figure 4.  Posterior interbody fusion of L3 to L4 in a 51-year-old man. Lateral radiograph shows the pedicle screw and rod instrumentation used to reconstruct the posterior column. Radiopaque markers indicate the location of the radiolucent bone graft cage.

 

Figure 5
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  		Figure 5.  Fracture of sublaminar wires used in corrective surgery for scoliosis. Routine surveillance radiograph demonstrates the fracture of multiple wires (arrows) and recurrent kyphosis of the thoracic spine anterior to the instrumentation.

 

Figure 6
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  		Figure 6.  Nonincorporated bone graft material. Lateral radiograph demonstrates anterior plate and screw instrumentation at C4 through C6, with intervertebral bone blocks used to reconstruct the anterior column. The graft material at C5–6 shows evidence of fusion, with blurring of graft margins and new bone formation in the interspace. Visible at the C4–5 level are persistent graft margins, sclerosis of the adjacent end-plates, and absence of new bone formation, features indicative of a lack of graft incorporation.

 

Figure 7A
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  		Figure 7a.  Resorption of nonunited graft material and hardware fracture. (a) Initial postoperative lateral radiograph demonstrates anterior plate and screw fixation of C4 to C5 with an intervertebral bone graft (*). Note the excellent graft incorporation at the levels of previous anterior fusion (C5 to C6 and C6 to C7); hardware was removed from those levels during surgical fusion of C4 to C5. (b) Extension radiograph obtained at 13-month follow-up demonstrates resorption of the graft material and fracture of the inferior screw (arrow).

 

Figure 7B
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  		Figure 7b.  Resorption of nonunited graft material and hardware fracture. (a) Initial postoperative lateral radiograph demonstrates anterior plate and screw fixation of C4 to C5 with an intervertebral bone graft (*). Note the excellent graft incorporation at the levels of previous anterior fusion (C5 to C6 and C6 to C7); hardware was removed from those levels during surgical fusion of C4 to C5. (b) Extension radiograph obtained at 13-month follow-up demonstrates resorption of the graft material and fracture of the inferior screw (arrow).

 

Figure 8A
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  		Figure 8a.  Utility of multidetector CT in evaluation of nonunion. (a) Anteroposterior radiograph demonstrates multilevel pedicle screw and rod instrumentation with a corpectomy at L3 and reconstruction with a humeral strut graft and lateral side-plate and screws. Areas of lucency around the inferior pedicle screws are indicative of loosening (arrowheads). (b) Coronal CT image clearly shows areas of lucency around the inferior pedicle screws (arrows). (c) Coronal CT image in a more posterior plane than b demonstrates the dense, granular appearance of the graft material (arrows), a finding indicative of a lack of graft incorporation into a solid fusion construct at this inferior level. (d) Coronal CT image in a more posterior plane than b and c shows adequate formation of a posterolateral osseous fusion complex at higher levels (arrows).

 

Figure 8B
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  		Figure 8b.  Utility of multidetector CT in evaluation of nonunion. (a) Anteroposterior radiograph demonstrates multilevel pedicle screw and rod instrumentation with a corpectomy at L3 and reconstruction with a humeral strut graft and lateral side-plate and screws. Areas of lucency around the inferior pedicle screws are indicative of loosening (arrowheads). (b) Coronal CT image clearly shows areas of lucency around the inferior pedicle screws (arrows). (c) Coronal CT image in a more posterior plane than b demonstrates the dense, granular appearance of the graft material (arrows), a finding indicative of a lack of graft incorporation into a solid fusion construct at this inferior level. (d) Coronal CT image in a more posterior plane than b and c shows adequate formation of a posterolateral osseous fusion complex at higher levels (arrows).

 

Figure 8C
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  		Figure 8c.  Utility of multidetector CT in evaluation of nonunion. (a) Anteroposterior radiograph demonstrates multilevel pedicle screw and rod instrumentation with a corpectomy at L3 and reconstruction with a humeral strut graft and lateral side-plate and screws. Areas of lucency around the inferior pedicle screws are indicative of loosening (arrowheads). (b) Coronal CT image clearly shows areas of lucency around the inferior pedicle screws (arrows). (c) Coronal CT image in a more posterior plane than b demonstrates the dense, granular appearance of the graft material (arrows), a finding indicative of a lack of graft incorporation into a solid fusion construct at this inferior level. (d) Coronal CT image in a more posterior plane than b and c shows adequate formation of a posterolateral osseous fusion complex at higher levels (arrows).

 

Figure 8D
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  		Figure 8d.  Utility of multidetector CT in evaluation of nonunion. (a) Anteroposterior radiograph demonstrates multilevel pedicle screw and rod instrumentation with a corpectomy at L3 and reconstruction with a humeral strut graft and lateral side-plate and screws. Areas of lucency around the inferior pedicle screws are indicative of loosening (arrowheads). (b) Coronal CT image clearly shows areas of lucency around the inferior pedicle screws (arrows). (c) Coronal CT image in a more posterior plane than b demonstrates the dense, granular appearance of the graft material (arrows), a finding indicative of a lack of graft incorporation into a solid fusion construct at this inferior level. (d) Coronal CT image in a more posterior plane than b and c shows adequate formation of a posterolateral osseous fusion complex at higher levels (arrows).

 

Figure 9
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  		Figure 9.  Mature pseudarthrosis in a symptomatic 54-year-old man who had undergone posterolateral fusion with Harrington rods from L4 through S1. Anteroposterior radiograph demonstrates a corticate linear defect in the posterolateral fusion complex on the left (arrow), a feature indicative of pseudarthrosis.

 

Figure 10A
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  		Figure 10a.  Early pseudarthrosis in a 43-year-old man. (a) Anteroposterior radiograph demonstrates a linear lucency in the posterolateral bone graft material on the right (arrow), a finding indicative of early pseudarthrosis. (b) Technetium 99m methylene diphosphonate bone scan (reversed to correspond to a) shows an area of markedly increased activity at this level (arrow), a feature that helps confirm the diagnosis.

 

Figure 10B
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  		Figure 10b.  Early pseudarthrosis in a 43-year-old man. (a) Anteroposterior radiograph demonstrates a linear lucency in the posterolateral bone graft material on the right (arrow), a finding indicative of early pseudarthrosis. (b) Technetium 99m methylene diphosphonate bone scan (reversed to correspond to a) shows an area of markedly increased activity at this level (arrow), a feature that helps confirm the diagnosis.

 

Figure 11A
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  		Figure 11a.  Medial deviation of a pedicle screw. Axial (a) and coronal (b) CT images show a screw that has traversed the medial cortex of the pedicle and penetrated the thecal sac (arrow), leading to a cerebrospinal fluid leak. The leak was repaired when the errant screw was removed, and a new screw was correctly positioned.

 

Figure 11B
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  		Figure 11b.  Medial deviation of a pedicle screw. Axial (a) and coronal (b) CT images show a screw that has traversed the medial cortex of the pedicle and penetrated the thecal sac (arrow), leading to a cerebrospinal fluid leak. The leak was repaired when the errant screw was removed, and a new screw was correctly positioned.

 

Figure 12
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  		Figure 12.  Lateral pedicle screw deviation in a 71-year-old man with neuropathy at L5. Axial CT image shows deviation of the right pedicle screw, which exits the lateral cortex and traverses the right neural foramen at the L5-S1 level (arrow). Neuropathy resolved after the screw was removed.

 

Figure 13
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  		Figure 13.  Penetration of the anterior sacral cortex in a 46-year-old man after lumbosacral fusion. Sagittal CT image shows that the inferior pedicle screw has exited the anterior cortex of the S1 segment and is impinging on the hypogastric vein (arrow).

 

Figure 14
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  		Figure 14.  Hardware malpositioning. Sagittal T2-weighted MR image demonstrates a magnetic susceptibility artifact produced by an anterior cervical screw that has exited the posterior cortex of the vertebral body and entered the spinal canal (arrow).

 

Figure 15A
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  		Figure 15a.  Dorsal herniation of an intervertebral bone graft cage in a 41-year-old woman with acute neuropathy. (a) Lateral radiograph depicts posterior interbody fusion at L4–5 and L5-S1 and posterolateral displacement of the L5-S1 bone graft cage into the spinal canal (arrow). The patient was experiencing worsening low back pain and a left L5 radiculopathy. (b) T2-weighted MR image demonstrates ventral and lateral effacement of the thecal sac (arrow) by the cage.

 

Figure 15B
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  		Figure 15b.  Dorsal herniation of an intervertebral bone graft cage in a 41-year-old woman with acute neuropathy. (a) Lateral radiograph depicts posterior interbody fusion at L4–5 and L5-S1 and posterolateral displacement of the L5-S1 bone graft cage into the spinal canal (arrow). The patient was experiencing worsening low back pain and a left L5 radiculopathy. (b) T2-weighted MR image demonstrates ventral and lateral effacement of the thecal sac (arrow) by the cage.

 

Figure 16
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  		Figure 16.  Wrong level of surgery. Sagittal T2-weighted MR image of an 80-year-old woman demonstrates an acute burst fracture of the L4 vertebra. The interpretation of the preoperative study (not shown) stated that posterior displacement of fracture fragments caused severe central canal stenosis at this level. However, the narrowest segment is that between the L4 fracture fragments and the posterior elements of L3 (arrow), particularly the thickened ligamentum flavum. Laminectomies were performed at L4 and L5 (*), but central canal stenosis persists between the L4 fracture fragments and the posterior elements of L3.

 

Figure 17
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  		Figure 17.  Acute neurologic compromise (cauda equina syndrome) in an 80-year-old woman after laminectomies at levels L3 through L5 for decompression. Sagittal T2-weighted MR image demonstrates a large hematoma (arrow) in the postoperative bed, with resultant compression of the thecal sac (arrowheads).

 

Figure 18
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  		Figure 18.  Accelerated ligamentous ossification secondary to placement of anterior cervical plates within 5 mm of the adjacent intervertebral disk. Lateral radiograph demonstrates large osteophytes (arrows).

 

Figure 19
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  		Figure 19.  Ligamentous instability following multisegmental cervical fusion. Lateral flexion radiograph demonstrates cervical fusion at C4 through C6 with anterior and posterior instrumentation and marked ligamentous instability at C6–7.

 

Figure 20
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  		Figure 20.  Acute fracture of the spine. Lateral radiograph of a patient who previously underwent a multilevel cervical fusion without instrumentation demonstrates an acute fracture that involves the anterior, middle (*), and posterior (arrow) columns at the C5 level. Underlying osteopenia and long-segment fusion created a predisposition to fracture.

 

Figure 21A
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  		Figure 21a.  Symptomatic disk herniation at a level adjacent to instrumentation. (a) Initial postoperative radiograph demonstrates posterior lumbar interbody fusion with pedicle screw and rod instrumentation at L3 through L5, with two titanium mesh cages in the L4–5 disk space. (b) Follow-up radiograph obtained 21/2 years later demonstrates a severe loss of disk height with a vacuum phenomenon at L2–3, the level above the fusion (arrow). (c) Anteroposterior fluoroscopic image from myelography demonstrates a large extra-dural defect caused by compression of the cauda equina (arrow) with midline herniation of the L2–3 disk.

 

Figure 21B
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  		Figure 21b.  Symptomatic disk herniation at a level adjacent to instrumentation. (a) Initial postoperative radiograph demonstrates posterior lumbar interbody fusion with pedicle screw and rod instrumentation at L3 through L5, with two titanium mesh cages in the L4–5 disk space. (b) Follow-up radiograph obtained 21/2 years later demonstrates a severe loss of disk height with a vacuum phenomenon at L2–3, the level above the fusion (arrow). (c) Anteroposterior fluoroscopic image from myelography demonstrates a large extra-dural defect caused by compression of the cauda equina (arrow) with midline herniation of the L2–3 disk.

 

Figure 21C
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  		Figure 21c.  Symptomatic disk herniation at a level adjacent to instrumentation. (a) Initial postoperative radiograph demonstrates posterior lumbar interbody fusion with pedicle screw and rod instrumentation at L3 through L5, with two titanium mesh cages in the L4–5 disk space. (b) Follow-up radiograph obtained 21/2 years later demonstrates a severe loss of disk height with a vacuum phenomenon at L2–3, the level above the fusion (arrow). (c) Anteroposterior fluoroscopic image from myelography demonstrates a large extra-dural defect caused by compression of the cauda equina (arrow) with midline herniation of the L2–3 disk.

 

Figure 22
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  		Figure 22.  Osteopenia-related insufficiency fractures of the cartilaginous endplates adjacent to a humeral strut graft. Sagittal CT image after an L1 corpectomy and reconstruction with a humeral allograft depicts the collapse of the cartilaginous endplates onto the dense graft material (arrows), which shows no signs of incorporation. Construct failure and a thoracic compression fracture (*) are associated with underlying osteopenia.

 

Figure 23
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  		Figure 23.  Facet fracture-dislocation and partially dislodged C5–6 anterior plate and screws. Sagittal CT image demonstrates a dislodged inferior screw (arrow) and interbody bone graft material. Bilateral locked facets and a facet fracture also were found. The patient, who had dementia, had removed his cervical collar and attempted to ambulate shortly after surgery.

 

Figure 24
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  		Figure 24.  Postoperative abscess and resultant dorsal effacement of the thecal sac. Sagittal T2-weighted fat-saturated MR image demonstrates a large abscess in the postoperative bed, with extensive abnormal T2 hyperintensity and mass effect on the thecal sac.

 

Figure 25A
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  		Figure 25a.  Postoperative diskitis and osteomyelitis. (a, b) Lateral radiographs in a patient who underwent partial diskectomy, laminectomy, and lumbar fusion without instrumentation. Initial postoperative image (a) and 6-month follow-up image (b) show progressive endplate destruction, collapse of the disk space, and osteopenia in the adjacent vertebral bodies (arrow in b), findings indicative of diskitis and osteomyelitis. (c) Sagittal T1-weighted contrast-enhanced MR image demonstrates intense enhancement in the vertebral bodies and remaining disk—a finding that helped confirm the diagnosis—as well as ventral compression of the thecal sac (arrow).

 

Figure 25B
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  		Figure 25b.  Postoperative diskitis and osteomyelitis. (a, b) Lateral radiographs in a patient who underwent partial diskectomy, laminectomy, and lumbar fusion without instrumentation. Initial postoperative image (a) and 6-month follow-up image (b) show progressive endplate destruction, collapse of the disk space, and osteopenia in the adjacent vertebral bodies (arrow in b), findings indicative of diskitis and osteomyelitis. (c) Sagittal T1-weighted contrast-enhanced MR image demonstrates intense enhancement in the vertebral bodies and remaining disk—a finding that helped confirm the diagnosis—as well as ventral compression of the thecal sac (arrow).

 

Figure 25C
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  		Figure 25c.  Postoperative diskitis and osteomyelitis. (a, b) Lateral radiographs in a patient who underwent partial diskectomy, laminectomy, and lumbar fusion without instrumentation. Initial postoperative image (a) and 6-month follow-up image (b) show progressive endplate destruction, collapse of the disk space, and osteopenia in the adjacent vertebral bodies (arrow in b), findings indicative of diskitis and osteomyelitis. (c) Sagittal T1-weighted contrast-enhanced MR image demonstrates intense enhancement in the vertebral bodies and remaining disk—a finding that helped confirm the diagnosis—as well as ventral compression of the thecal sac (arrow).

 

Figure 26A
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  		Figure 26a.  Postoperative diskitis after posterior instrumentation. (a) Scintigram obtained with indium 111–labeled autologous leukocytes demonstrates increased radiotracer activity and acute angulation at the disk space (arrow), a finding suggestive of postoperative diskitis. (b) Anteroposterior fluoroscopic spot image shows a needle inserted in the disk space for aspiration biopsy. The presence of bacterial diskitis was confirmed.

 

Figure 26B
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  		Figure 26b.  Postoperative diskitis after posterior instrumentation. (a) Scintigram obtained with indium 111–labeled autologous leukocytes demonstrates increased radiotracer activity and acute angulation at the disk space (arrow), a finding suggestive of postoperative diskitis. (b) Anteroposterior fluoroscopic spot image shows a needle inserted in the disk space for aspiration biopsy. The presence of bacterial diskitis was confirmed.

 

Figure 27
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  		Figure 27.  Arachnoiditis after L4 and L5 laminectomies. Sagittal T2-weighted MR image demonstrates an abnormal configuration of the lumbar nerve roots (arrow), a finding indicative of arachnoiditis.

 




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