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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6009_Библиотеки_им_академика_М_И_Перельмана.pdf
(Left) Subsidence of the
http://pdf-radiology.com
superior aspect of interbody
cage graft with instability
demonstrates that the initial
sagittal CT shows an
expandable cage position at
the L3 corpectomy site with
the inferior margin engaged
with the posterior-superior L4
body and the superior margin
Devices and Instrumentation
engaged with the anteriorinferior L2 body ſt. (Right)
Four-month follow-up study
shows rotation of the cage
and subsidence of the superior
margin of the cage into the L2
body . The inferior aspect of
the cage has rotated into the
canal st.
(Left) Subsidence of the
superior aspect of interbody
cage graft with instability
demonstrates that initial T1WI
MR shows the extensive signal
loss related to the cage but
suggests abnormal position of
the cage due to a metal
artifact extending into the
spinal canal ſt. (Right)
Sagittal T2WI MR shows the
less extensive signal loss
related to the cage, increasing
confidence that the posterior
position of the cage is
abnormal due to the metal
artifact extending into the
spinal canal at the inferior L3
level .
Cages
(Left) In this sagittal CT after
C5 and C6 corpectomies and
partial C4 and C7
corpectomies for traumatic
burst fractures, note the
titanium mesh cage with
bone graft material ſt, ACDF
from C4-C7 st, and hardware
failure with anterior
displacement . (Right) AP
radiograph displays different
interbody fusion devices:
Allografts with radiodense
markers ſt and interbody
lumbar cage . The latter is
composed of porous titanium
cylinders placed in the disc
space, allowing bone graft to
fuse adjacent vertebral bodies.
70
Cages
http://pdf-radiology.com
Devices and Instrumentation
(Left) Coronal CT
reconstruction demonstrates a
lumbar vertebral replacement
prosthesis with a central
metallic rod ſt and outer
PEEK radiolucent core .
Lateral fusion construct st
provides additional stability
after total vertebrectomy.
(Right) Sagittal CT
reconstruction in the same
patient shows a lumbar
prosthesis with a central rod
ſt and outer PEEK core .
Note the graft position within
the anterior 2/3 of disc space.
The corporal screw of a lateral
fusion construct st provides
additional stability.
(Left) AP plain film shows
paired Pyramesh cages
spanning the L2 level for
vertebral collapse ſt with
bilateral pedicle screw fixation
st. Methylmethacrylate is
noted surrounding the cages
. (Right) Coronal CT
demonstrates paired
Pyramesh cages ſt spanning
the L2 level for vertebral
collapse. The superior aspect
of the cage had subsided into
the endplate st.
Methylmethacrylate is noted
surrounding the cages .
(Left) Anteroposterior
radiograph illustrates an
expandable cage and
posterior instrumentation ſt.
This patient underwent
preoperative embolization of
vertebral lesions at the T9 and
T10 levels and of bilateral T8T12 intercostal arteries st. An
expandable cage allows
restoration and preservation
of vertebral body height and
alignment after anterior
tumor resection. (Right)
Anteroposterior radiograph
exhibits a titanium mesh
cervical cage ſt. ACDF from
C3-C5 is also noted st.
71
Subaxial Posterior Instrumentation
KEY FACTS
http://pdf-radiology.com
TERMINOLOGY
• Methods to stabilize subaxial cervical spine with posterior
element constructs
PROCEDURE
• Interspinous wiring (Rogers 1942)
○ Simple and low risk
• Sublaminar wiring
○ Attach to onlay graft material or rods
• Facet wiring (Callahan 1977)
Devices and Instrumentation
○ Facet capsules opened and holes drilled at each level
• Clamps (Tucker 1975)
○ Narrows spinal canal similar to sublaminar wires
• Lateral mass screws and plates (Roy-Camille)
○ Immediate stability with no need for external halo
fixation
○ Usually oriented in superior and lateral direction to avoid
VA and exiting nerve roots
• Transarticular screws
Lateral Mass Screws Screw Position Relative to Vertebral Artery
○ Used in C1-C2 interspace but also described for subaxial
spine
• Lateral mass screws and rods
○ Very useful for multilevel disease
• Cervical pedicle screws (Abumi 1994)
○ Excellent stability and fixation
○ Resistant to pullout
○ Technically challenging since verterbal artery injury can
occur
OUTCOMES
• Lateral mass screw: Incidence of facet joint violation as high
as 20%
• Pedicle screw: 1.7% neurovascular complications
○ 7% cortical perforation rate for cervical pedicle screws
○ Pedicles should be at least 4.5 mm in diameter for safe
screw placement
• Dural tear: Related to sublaminar wire placement
72
Axial NECT shows laminectomy with bilateral-lateral mass
fixation with polyaxial screws.
Sagittal CT angiogram shows the position of the 4-level
lateral mass screws angled cephalad and the relationship
to the ventral dominant vertebral artery ſt.
Subaxial Posterior Instrumentation
http://pdf-radiology.com
TERMINOLOGY
Abbreviations
• Vertebral artery (VA)
Synonyms
• Posterior cervical fusion
• Posterior cervical stabilization
Definitions
• Methods to stabilize subaxial cervical spine with posterior
element constructs
PROCEDURE
Procedure Steps
• Interspinous wiring (Rogers 1942)
○ Simple and low risk
○ Holes drilled into spinous processes with wires passing
through
○ Single point of fixation
○ Bohlman triple-wire variation used to stabilize 1 or more
levels
• Sublaminar wiring
○ Can be used in subaxial spine
○ Difficulty related to narrowing of spinal canal with wires
at spinal levels with normally small bony canal and
maximum cervical cord size
○ Attach to onlay graft material or rods
• Facet wiring (Callahan 1977)
○ Facet capsules opened and holes drilled at each level
○ Wires passed through drilled holes in superior to inferior
direction
○ Exiting joint space
○ Wires then wrapped around graft material secured to
decorticated articular masses
• Clamps (Tucker 1975)
○ Introduced for C1-C2 arthrodesis
○ Claw-type construct
– Allowing immediate fixation without risk of direct
neural injury of sublaminar wire
○ Bone graft placed into interlaminar spaces bilaterally
○ Utilized for subaxial spine at any single level
○ Requires intact lamina
• Lateral mass screws and plates (Roy-Camille technique)
○ Immediate stability with no need for external halo
fixation
○ Various modifications with slightly different entrance
points and screw direction
○ Usually oriented in superior and lateral direction to avoid
VA and exiting nerve roots
– Magerl method
□ Axial plane: 25° lateral
□ Sagittal plane: Parallel to facet joint
□ Incidence of nerve root injury higher than with Roy-
Camille technique
– Anderson method
□ Axial plane: 10° lateral
□ Sagittal plane: 30-40° rostral
– An method
□ Axial plane: 30° lateral
Devices and Instrumentation
□ Sagittal: 15° rostral
□ Decreased neurovascular injury with this technique
○ Transarticular screws
– Used in C1-C2 interspace but also described for
subaxial spine
– VA location simplifies screw placement relative to
complexity at C1-C2
– Screw direction is anterior and caudal
○ Lateral mass screws and rods
– Various manufacturers including
□ Cervifix™ system (Synthes; Solothurn, Switzerland)
□ Summit™ and Mountaineer™ systems (DePuy;
Raynham, MA)
□ Vertex® system (Medtronic; Fridley, MN)
□ S4® cervical system (Aesculap; Center Valley, PA)
□ Minit™ posterior cervical & upper thoracic fixation
system (Zimmer; Warsaw, IN)
– Allow for precise placement of screws with
realignment
– Very useful for multilevel disease
○ Cervical pedicle screws (Abumi 1994)
– Excellent stability and fixation
– Resistant to pullout
– Technically challenging since VA injury can occur
– Pedicle diameter smaller than thoracolumbar pedicle
– Pedicle axis more inclined in transverse plane
□ Fluoroscopic-assisted pedicle axis view technique
allows high success rate
OUTCOMES
Complications
• Lateral mass screws
○ With long 20-mm bicortical screws
– Higher potential for injury has been documented with
Magerl method than An method
○ Incidence of facet joint violation as high as 20%
• Pedicle screws have been recommended due to problems
with mechanical loosening and avulsions at upper and
lower construct margins
○ 7% perforation rate for cervical pedicle screws
○ 1.7% neurovascular complications
○ Screw perforation highest at C4 and C7
○ Pedicles should be at least 4.5 mm in diameter for safe
screw placement
• Patients with severe cervical spondylotic myelopathy at risk
of postoperative weakness and cord contusion from
posterior decompression
○ Even without intraoperative difficulties and with stable
somatosensory-evoked potentials monitoring
• Dural tear
○ Related to sublaminar wire placement
SELECTED REFERENCES
1. Liu G et al: Anatomical considerations for the placement of cervical
transarticular screws. J Neurosurg Spine. 14(1):114-21, 2011
2. Memtsoudis SG et al: Increased in-hospital complications after primary
posterior versus primary anterior cervical fusion. Clin Orthop Relat Res. 2011
Mar;469(3):649-57. Erratum in: Clin Orthop Relat Res. 469(5):1502-4, 2011
3. Zhao L et al: Comparison of two techniques for transarticular screw
implantation in the subaxial cervical spine. J Spinal Disord Tech. 24(2):126-31,
2011
73
Transpedicular Screw Fixation
KEY FACTS
http://pdf-radiology.com
TERMINOLOGY
• Pedicle screw: Most common implant in spine surgery
○ High rigidity and resistance to pullout
○ Engages all 3 columns of spine
○ Resists motion in all 3 directions
• Used in wide variety of procedures
○ Maintain spine alignment while fusion occurs
○ Maintain reduction after fracture
Devices and Instrumentation
○ Maintain correction of deformity
PROCEDURE
• 3 common techniques
○ Free hand
○ Fluoroscopy based
○ Computer assisted (navigation) either 2D or 3D
– Safe and reproducible
– Incidence of exposed screws outside of pedicle
decreased with 3D navigation from 12% to 7%
(Left) Axial graphic shows the
right pedicle screw is fractured
ſt, loosening, and has
breached the medial pedicle
cortex and torn the dura
with resultant CSF leakage .
The left screw is
malpositioned with the tip
impinging the aorta. (Right)
Pedicle stress fracture
following failed pedicle screw
fixation is shown. Axial CT
post myelography shows
lucency surrounding the left
pedicle screw, indicating
loosening, with fracture
through the left pedicle ſt.
The posterior bone graft
material is not mature.
OUTCOMES
• CT is gold standard for assessment of pedicle screw
position
• Screw malposition rates vary widely (0.5-13%)
• Medial wall penetration
○ Pedicle wall penetration (10-20% overall incidence)
○ Neural injury to root or cord (< 1%)
○ CSF leak if dural laceration
• Anterior or lateral penetration
○ Visceral injury, esophageal perforation
○ Pneumothorax
○ Aortic or segmental vessel penetration
○ Some canal intrusion is asymptomatic (< 2 mm)
• Pedicle fracture
• Pedicle plow
○ Occurs during vertebral rotation in scoliosis surgery
○ May cause aortic abutment of screw
Complication Graphic Stress Fracture
(Left) Screw malposition,
screw loosening, and pedicle
fracture are seen on this axial
post myelogram image
showing a left L5 pedicle
fracture ſt. The right pedicle
screw is malpositioned medial
to and into the region of the
exiting root st. (Right)
Coronal NECT shows L4-5 solid
fusion with intact hardware
ſt. There is loosening of the
pedicle screws at L3 with
lucency about the metal st.
The hardware failure has
allowed instability at L3-4,
causing the progression of disc
degeneration .
74
Screw Malposition and Loosening Screw Loosening
Transpedicular Screw Fixation
http://pdf-radiology.com
TERMINOLOGY
Synonyms
• Pedicle screw
• Pedicle fixation
Pedicle Screw
• Most common implant in spine surgery
○ High rigidity and resistance to pullout
○ Engages all 3 columns of spine
○ Resists motion in all 3 directions
PROCEDURE
Techniques
• 3 common techniques
○ Free hand
○ Fluoroscopy based
○ Computer assisted (navigation)
• Fluoroscopy
○ Not 100% accurate (80-90%)
○ Risk of radiation exposure
• Navigation system theoretically most accurate
○ Safe and reproducible
○ Incidence of exposed screws outside of pedicle
decreased with 3D navigation from 12% to 7%
OUTCOMES
Problems
• Screw malposition rates vary widely (0.5-20%)
• Malpositioned instrumentation may have acute and chronic
morbidity
○ Can cause delayed instability
○ Accelerate degenerative change in adjacent segment
• Perioperative
○ Pedicle wall penetration (10-20% overall incidence)
○ Medial wall penetration
– Neural injury to root or cord (< 1%)
– CSF leak if dural laceration
○ Anterior or lateral penetration
– Visceral injury
– Pneumothorax
– Esophageal perforation
– Aortic or segmental vessel penetration
– Injury can occur due to screw itself; may also be
related to taps and guidewire manipulation
intraoperatively
□ If screw or taps inserted at different angle than
wire, wire can kink and be driven further into body
– Some canal intrusion is asymptomatic
– Medial violation must be > 3 mm to approach same
volumetric intrusion as largest pedicle hook footplate
○ Pedicle fracture
○ Pedicle plow
– Occurs at time of direct vertebral rotation in scoliosis
surgery
– Axial plane plow is medial &/or lateral translation of
pedicle screw through cortical boundaries of pedicle
&/or vertebral body
– May cause aortic abutment of screw
• Delayed postoperative
○ Wound infection
○ Loosening of screw
○ Disconnection of screw from rod
Complications
• Most feared complication(s)
○ Medial cortical penetration by screw with cord injury
• Radiograph evaluation
○ Guidelines for detecting medial or lateral wall violation
on plain films (Kim et al, 2005)
– Violation of harmonious segmental change of tips of
inserted screws with reference to vertebral rotation
using posterior upper spinolaminar junction in PA
radiograph (medial or lateral out)
– No crossing of medial pedicle wall by tip of pedicle
screw inserted with reference to vertebral rotation
using posterior upper spinolaminar junction in PA
radiograph (lateral out)
– Violation of imaginary midline of vertebral body using
posterior upper spinolaminar junction in PA
radiograph by position of tip of inserted pedicle screw
(medial out)
• CT is gold standard for assessment of pedicle screw
position
○ Intraoperative CT can reduce revision rate
○ ↑ radiation dose
○ CT shows 10x more screws violating pedicle cortex than
plain radiographs
• MR evaluation limited due to metal artifact
○ Adjusting direction of frequency encode can minimize
screw artifact
○ Frequency encode in AP direction minimizes right-to-left
artifact for pedicle screws
• EMG
○ Screw malposition can be detected by intraoperative
triggered EMG after screw insertion in lumbar spine
SELECTED REFERENCES
1. Ponnusamy KE et al: Instrumentation of the osteoporotic spine:
biomechanical and clinical considerations. Spine J. 11(1):54-63, 2011
2. Cho W et al: The biomechanics of pedicle screw-based instrumentation. J
Bone Joint Surg Br. 92(8):1061-5, 2010
3. Hicks JM et al: Complications of pedicle screw fixation in scoliosis surgery: a
systematic review. Spine (Phila Pa 1976). 35(11):E465-70, 2010
4. Samdani AF et al: Accuracy of free-hand placement of thoracic pedicle
screws in adolescent idiopathic scoliosis: how much of a difference does
surgeon experience make? Eur Spine J. 19(1):91-5, 2010
5. Samdani AF et al: Learning curve for placement of thoracic pedicle screws in
the deformed spine. Neurosurgery. 66(2):290-4; discussion 294-5, 2010
6. Heary RF et al: Decision making in adult deformity. Neurosurgery. 63(3
Suppl):69-77, 2008
7. Kakkos SK et al: Delayed presentation of aortic injury by pedicle screws:
report of two cases and review of the literature. J Vasc Surg. 47(5):1074-82,
2008
8. Lehman RA Jr et al: Computed tomography evaluation of pedicle screws
placed in the pediatric deformed spine over an 8-year period. Spine (Phila Pa
1976). 32(24):2679-84, 2007
9. Shah SA: Derotation of the spine. Neurosurg Clin N Am. 18(2):339-45, 2007
10. Macagno AE et al: Thoracic and thoracolumbar kyphosis in adults. Spine
(Phila Pa 1976). 31(19 Suppl):S161-70, 2006
11. Foster MR: A functional classification of spinal instrumentation. Spine J.
5(6):682-94, 2005
12. Kim YJ et al: Evaluation of pedicle screw placement in the deformed spine
using intraoperative plain radiographs: a comparison with computerized
tomography. Spine (Phila Pa 1976). 30(18):2084-8, 2005
Devices and Instrumentation
75
Cervical Artificial Disc
KEY FACTS
http://pdf-radiology.com
TERMINOLOGY
• Artificial disc replacement, total cervical disc replacement,
artificial intervertebral disc arthroplasty
• Insertion of prosthetic total disc replacement after anterior
decompression with aim of preserving normal range and
type of intervertebral motion
• Preventing complications associated with rigid arthrodesis
& subsequent segmental loss of motion
IMAGING
Devices and Instrumentation
• Radiographs with flexion and extension views
• CT to assess for adjacent level disease and heterotopic
ossification
• Postoperative MR may be helpful in cases of persistent pain
to assess for inadequate decompression or myelopathy
(Left) Lateral radiograph
illustrates a ProDisc-C cervical
disc . It has cobaltchromium endplates with a
central keel for anchorage to
the vertebral body and a
locking core of ultra high
molecular weight
polyethylene that provides a
ball-and-socket articulation.
(Right) Lateral radiograph
shows a Prestige LP total
cervical disc replacement
(TCDR) . This titanium
ceramic device is composed of
articulating ball and trough
components. Screws attach it
to the cervical vertebrae.
CLINICAL ISSUES
• Ideal patient has soft disc herniation causing neuro
signs/symptoms, motion at involved segment, no evidence
of osteoporosis or infection
• Worldwide indication is 1-2-level radiculopathy or
myelopathy; however, FDA indication is limited to singlelevel disease in levels C3 to C7
• Candidates: Those who failed conservative therapy +
evidence of symptomatic nerve root ± spinal cord
compression
• Complications
○ Device wear, subsidence or displacement, segmental
hypermobility, and excessive disc space distraction to
accommodate prosthesis, consequent facet joint
separation, and screw breakage
○ Facet arthrosis, adjacent level degeneration
○ Paravertebral heterotopic ossification may be prevented
with NSAIDs
(Left) Radiograph shows a
grade 2 heterotopic
ossification st, a complication
of TCDR. Ossification along
the lateral aspect of the
device may result in fusion,
causing reduced movement,
whereas anterior ossification
allows continued mobility.
(Right) Lateral radiograph
shows a Bryan cervical disc
, which is composed of
porous, coated, clamshellshaped, titanium endplates
and a polycarbonate,
polyurethane core. This
prosthesis provides elasticity
and compressibility.
76
Lumbar Artificial Disc
KEY FACTS
http://pdf-radiology.com
Devices and Instrumentation
TERMINOLOGY
• Total lumbar disc replacement, arthroplasty
• Treatment of degenerative disc disease restoring normal
mobility of diseased segments & improving clinical
outcomes by decreasing risk of adjacent-level disease
IMAGING
• Endplate keel, fixation spikes, and inlay may help identify
individual devices
• Radiography helpful to identify midline placement, AP
positioning, and degree of vertebral body penetration or
subsidence
• CT best for evaluating extent of vertebral body penetration
• CT and MR helpful to evaluate adjacent vertebral bodies,
particularly in detecting fractures and degenerative
changes at adjacent disc space and facet levels
CLINICAL ISSUES
• Lumbar disc arthroplasty indicated for 1- or 2-level
discogenic mechanical back pain primarily in absence of
radiculopathy
• Complications
○ Heterotopic ossification incidence in 1.4-15.0%
○ Adjacent level degenerative disease, facet arthrosis
○ Device migration, extrusion of inlay
○ Subsidence: 3-10% incidence
○ Segmental lordosis alterations
○ Vertebral fractures
• Indications
○ Skeletal maturity
○ Degenerative disc disease at 1 level from L4 through S1
○ No relief of pain after 6 months or more of nonsurgical
treatment
(Left) Lateral radiograph
shows Activ-L lumbar artificial
disc ſt. Although arthrodesis
is the gold standard for
surgical treatment of lumbar
degenerative disc disease,
solid fusion can cause
increased motion in adjacent
segments. This may initiate
&/or accelerate the adjacent
segment disease process.
(Right) Activ-L ſt allows for
maintenance/restoration of
physiologic movement at
affected segments. Restoring
and maintaining normal
motion of the segment
reduces stresses and loads on
adjacent levels.
(Left) Lateral radiograph
shows the FlexiCore TLDR .
Current indications for lumbar
disc arthroplasty are young,
nonosteoporotic patients with
1- or 2-level symptomatic disc
degeneration without severe
facet arthropathy, segmental
instability, or neural element
compression requiring a
posterior decompression.
(Right) Extension ſt and
flexion views show
relatively preserved range of
motion. The normal spinal
mobility and biomechanics are
thought to reduce adjacent
spinal deterioration.
77
Interspinous Spacing Devices
KEY FACTS
http://pdf-radiology.com
TERMINOLOGY
• Synonyms: Interspinous posterior decompression,
interspinous distraction device, interspinous spacer device
(ISD), interspinous implant
• Dynamic stabilization alters movement & load transmission
of spinal motion segment without fusion of segment
• Interspinous spacing device places stenotic segment in
slight flexion while preventing extension
IMAGING
Devices and Instrumentation
• Radiographs & CT helpful to evaluate interspinous location
○ Assess for fractures
PATHOLOGY
• Lumbar neurogenic claudication symptoms are
exacerbated during extension, relieved during flexion
○ Dimensions of canal & foramen ↑ in flexion, ↓ in
extension
○ Facet loading ↑ during extension, ↓ during flexion
(Left) X-Stop implants ſt at
L4-L5 & L5-S1 are titanium
alloy devices placed between
spinous processes to reduce
canal & foraminal narrowing
that occurs in extension, thus
reducing the symptoms of
neurogenic intermittent
claudication. (Right) Sagittal
bone CT shows an interspinous
spacing device (ISD) st, which
may increase the foraminal
area & height as well as spinal
canal diameter in extension.
ISDs may improve recurrent
facet joint pain in clinical
short- and midterm settings
but do not exceed outcome of
denervated patients.
CLINICAL ISSUES
• ISD helpful for treatment of spinal stenosis with neurogenic
claudication
○ Causes focal flexion at applied level, resulting in
increased canal & foramen dimensions
• Complications
○ ISD malposition, migration, dislocation, spinous process
fracture
• Indications
○ Lumbar stenosis ± facet joint hypertrophy & subarticular
recess stenosis, foraminal stenosis
○ 1- to 2-level lumbar stenosis from L1-L5 in patients with
at least moderate impairment in function
• Patients anatomy may influence outcomes
○ Decreased accessible distance between laminospinous
plane and tip of spinous process
• Osteoporosis is contraindication
(Left) Sagittal T1WI MR shows
the susceptibility artifact from
the ISDs . X-Stop is the most
commonly used ISD in patients
with neurogenic intermittent
claudication due to lumbar
stenosis. (Right) Axial CT
myelographic image of spinous
process fractures at 2 levels
following placement of X-Stop
devices for canal stenosis
shows fractures through the
L4 spinous processes ſt. Note
the overlap of the wings of the
adjacent level devices .
78
Interspinous Spacing Devices
http://pdf-radiology.com
Devices and Instrumentation
IMAGING
General Features
• Location
○ Interspinous soft tissues of lumbar spine
– Extradural
Radiographic Findings
• Free-floating prosthesis in interspinous region
CT Findings
• Implant is not rigidly attached to bony anatomy
○ Restricted from migrating posteriorly by supraspinous
ligament, anteriorly by laminae, cranially & caudally by
spinous process (SP), & laterally by 2 wings or stops on
implant
MR Findings
• Susceptibility artifact may obscure detailed delineation of
hardware & its appropriate orientation in interspinous soft
tissues
Imaging Recommendations
• Best imaging tool
○ Radiograph helpful for interspinous location (flexion &
extension views useful to detect abnormal motion of
hardware)
○ CT: Assess vertebral bodies & posterior elements for
fractures
PATHOLOGY
Staging, Grading, & Classification
• Static (noncompressible)
○ X-Stop (Medtronic Sofamor Danek; Minneapolis, MN):
Titanium oval spacer with 2 lateral wings to prevent
lateral migration
○ Wallis implant (Abbott Spine; Austin, TX):
Polyetheretherketone (PEEK) spacer placed between
SPs & secured with 2 Dacron ligaments wrapped around
SPs
– Good 13-year clinical outcome in 1 study, obviated
arthrodesis in 80% of patients
– Current indications
□ Following discectomy for large herniated disc in
which there is significant loss of disc material
□ Redo discectomy for recurrent herniation
□ Discectomy for herniation of transitional disc with
sacralization of L5
□ Degenerative disc adjacent to fused segment
□ Isolated Modic 1 lesion attributable to chronic low
back pain
○ Aperius PercLID system (Medtronic Sofamor Danek):
Percutaneous device insertion
○ ExtenSure (NuVasive; San Diego, CA): Cylinder-shaped
allograft device
• Dynamic (compressible)
○ Coflex Interspinous U (Paradigm Spine; New York, NY)
○ Diam (Medtronic Sofamor Danek): Silicone interspinous
spacer covered by polyethylene coat, secured in place
with 2 ligatures around superior & inferior SPs
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Standard surgical treatment of spinal stenosis or lateral
recess stenosis: Laminectomy or bilateral
hemilaminotomies & foraminotomies
– Extensive soft tissue dissection for laminectomy,
longer surgical time, & more blood loss
□ Procedures less attractive for frail elderly patients
○ Osteoporotic fractures may result only in loss of height
or stooped posture
– With spinal stenosis & narrowed lateral recess &
foramina, extension of back from brace & axial loading
from weight of standing causes nerve root
compression
– Extension of lumbar spine shown to decrease cross-
sectional area of neural foramen by ~ 15%
• Complications
○ Postoperative complication rate 10.1% & reoperation
rate 6-7.2%
○ Interspinous distraction device (ISD) malposition
○ Migration: Device remains between SP, function is
preserved, & patient is asymptomatic
○ Dislocation: Device moved outside interspinous area but
contained by detached supraspinous ligament or
associated with ruptured supraspinous ligament
– Nonfunctional with recurring symptoms requiring
revision surgery
○ SP fissures & fractures
○ Rare stress fracture of facet joints
Treatment
• Indications
○ Lumbar stenosis ± facet joint hypertrophy & subarticular
recess stenosis, foraminal stenosis, ± stable grade I
spondylolisthesis or equivalent retrolisthesis
○ Limited to use in 1-2 level lumbar stenosis from L1-L5 in
patients with at least moderate impairment
○ Dynamic stabilization attractive option (compared to
fusion) for younger patients who would bear greater
burden on adjacent segments during their prolonged
follow-up
• Exclusion criteria in some studies
○ Unable to sit for prolonged periods without pain;
unremitting spinal pain in any position; cauda equina
syndrome; pathologic fractures of vertebrae; active
infection; Paget disease at involved segments or spinal
metastases; spinal anatomy, such as ankylosing
spondylitis or fusion, at affected level
• ISD shown to have extremely high failure rate (defined as
surgical reintervention) after short-term follow-up in
patients with spinal stenosis caused by degenerative
spondylolisthesis
• Implants are not favorable or currently recommended for
use at L5-S1
• ISD does not restrict or eliminate any potential future
therapeutic options that are currently being developed,
such as arthroplasty
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