Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6040_Библиотеки_им_академика_М_И_Перельмана.pdf
3 Surgery 21
posteriorly but also in the disk space. Furthermore a spacer is inserted into the disc space
helping to restore normal height and opening up
nerve foramina to take pressure off the nerve
roots. Finally a TLIF procedure allows the surgeon to insert bone graft and spacer into the disk
space from a unilateral approach without having
to retract nerve roots, whit reduction of injury
and scarring around roots respect to PLIF.
Posterolateral Fusion
It is performed as an alternative to PLIF when
there is a severe loss ofdisk space height andwhen
the insertionof a posterior interbody spacer might
cause neurologic compromise. Bone graft material is placed laterally (between transverse
processes) rather than anteriorly (between vertebral bodies). Posterolateral fusion is usually
supplemented by posterior instrumentation.
Lateral Interbody Fusion
It can be performed by two different modalities:
direct lateral interbody fusion and XLIF. These
approaches passes transversely through the retroperitoneal fat and psoas major muscle, allowing access to the disk space from lateral approach
without peritoneal disruption or mobilization.
Diskectomy is performed after obtaining access
to the disk space, leaving intact posterior annulus. An implant and bone graft are then placed in
the disk space and then incisions are closed.
These implants have a characteristic long-rectangular shape, designed to maximize surface
area on which the epiphyseal ring can rest.
XLIF is minimally invasive spine surgery
designed to accomplish spinal fusion with several advantages including minimal tissue damage, minimal blood loss, small incisions and
scars, minimal post-operative discomfort, relatively quick recovery time and return to normal
function. Because of the above factors, it is one
of a number of options for spinal fusion that are
relatively minimally invasive. Several complications have been reported with this technique,
some unique to this approach like thigh paresthesia or dysesthesia, most commonly in the
distribution of the anterior cutaneous branch of
the femoral nerve. Sensory abnormalities are
probably related to neural stretching as a result
of patient positioning.
Trans-Sacral Fusion
AxialLIF aims to perform anterior fusion at
L5-S1 in presence of degenerative disk disease,
degenerative lumbar scoliosis and symptomatic
instability and stenosis. Contraindications for
this procedure include severe degenerative disk
disease with complete collapse of the disk space
and previous retroperitoneal surgery.
AxialLIF is performed by using a series of
guide pins and dilator tubes that are inserted
under fluoroscopic guidance to obtain access to
the L5-S1 disk space. Diskectomy is then performed percutaneously. Bone graft material is
introduced into the disk space, and threaded
titanium pin is placed across the disk space.
Reported complications included pelvic visceral
injury and pseudoarthrosis.
3.2.2 Osteoinductive Bone Graft
Substitutes
Large number of spinal fusion procedures
involve the use of bone graft material. There are a
lot of considerations to evaluate when deciding
which type of bone graft options to use. The main
factors to be taken into account include type of
spinal fusion, number of levels of spine involved,
location of fusion, patient risk factors for nonfusion (e.g., if patient is obese, smoker, poor bone
quality), surgeon experience and preference.
Using patient own bone is considered the gold
standard (autograft). However, this is not the best
option for all patients. In autograft placement, a
bone graft is harvested from the patient, typically
from the iliac crest. While this poses little risk of
infection or rejection, it has been shown conversely increased surgical time, relatively limited
quantities of bone graft material, and frequent
22 T. Scarabino et al.
donor-site pain. In allografting, instead, bone is
harvested from a donor and while this process
decreases surgical time and morbidity at the
harvesting site, there is opportunity for infection.
Allografts moreover, decreases ability to stimulate new bone formation. In an effort to reduce
surgical risks and possible complications with
using patient own bone and to enhance rates of
fusion, the spine medicine community is focusing resources on developing better options like
osteoinductive bone graft substitutes.
Bone morphogenic protein (BMP) is a synthetic osteoinductive material that promotes bone
creation and remodelling. It has been reported to
induce bone growth that is equivalent to or even
greater than that induced by an autograft. BMP is
delivered to the fusion site on an absorbable
collagen sponge with interbody cages or bone
dowels. BMP use has been shown to yield
radiographic fusion rates superior to those
achieved with iliac crest bone grafts [4]. The
normal phases of bone healing include an initial
inflammatory response, a resorptive phase, subperiosteal and endosteal proliferation, bone formation, consolidation, and finally, remodelling
by osteoclast and osteoblast activity.
and posterior element replacement systems) that
may be used alone for stabilization or in combination with fusion devices. It is important to
note that with any type of spine fusion there is a
risk of clinical failure (meaning that patient pain
does not go away) despite achieving a successful
fusion. Obtaining a successful result from a
spine fusion requires a number of factors,
including an accurate preoperative diagnosis, a
technologically adept surgeon, and a patient
with a reasonably healthy lifestyle (non smoker,
non obese) who is motivated to pursue rehabilitation and restoration of his functions.
The three-joint nature of the functional spinal
unit, consisting of disk space and two facet joints,
allows for multiple device categories and
approaches. These can be divided into two main
categories: anterior and posterior motion preservation devices. Anterior motion preservation
devices include total disk replacements and partial disk-nucleus replacements. Posterior motion
preservation devices include interspinous devices, pedicle screw–based dynamic posterior stabilization devices, and facet replacement devices.
Total Disk Replacement
3.2.3 Dynamic Stabilization
Fusion surgery has been shown to alter the
normal biomechanics of the spine, and this is
believed to contribute to the development of
adjacent-level disease. To overcome such disadvantages, an alternative to vertebral fusion
procedures is the dynamic stabilization [3, 4,
16–18]. It has become increasingly popular in
attempt to provide stability while maintaining
near-normal biomechanics and motions, to mitigate negative effects on adjacent segments and
thus to prevent progressive degeneration.
Dynamic stabilization is a not-fusion system
performed in patients with low back pain originating from chronic degeneration of the lumbar
spine. There is a wide variety of dynamic stabilization devices (total or partial disk replacement, interspinous process decompression
devices, pedicle screws and artificial ligaments,
Also known as disk arthroplasty, performed in
cervical and lumbar spine, it was developed as
an alternative to anterior fusion in patients
whose pain probably originates primarily from
disk degeneration without nerve root involvement. The aim is to closely replicate the normal
spine biomechanics in attempt to prevent
development of adjacent-level degeneration and
arthrodesis-related complications like pseudoarthrosis, iliac crest donor site pain.
This procedure include removal of the diseased disk and insertion of a prothesis to alleviate diskogenic pain and to restore normal disk
height. Disckectomy should be performed, with
removal of the native annular fibers and of the
anterior and posterior longitudinal ligaments
There must be at least 4 mm of residual disk
height and lack of significant endplate degeneration to provide satisfactory anchorage for the
replacement device. The presence of facet joint
degeneration is a contraindication to total disk
3 Surgery 23
replacement [19]. Devices are of different types
[20] and all contain radiopaque endplates characteristically located in the disk space. Modern
artificial disks consist of two parallel plates
(usually metallic) with exterior toothlike projections designed to securely anchor itself to the
adjacent vertebrae and so limit migration.
Polyethylene core between the plates allows
motion and provides cushioning. The core is
radiolucent, but it contains a metal wire for
identification on imaging.
Partial Disk Replacement
It replaces the nucleus while restoring the normal biomechanical function of the disk and of
the segment. Currently, there are two general
types of nucleus replacement devices: injectable
and preformed. Injectable nucleus replacement
devices are further subdivided into uncontained
and contained. Preformed implants are further
subdivided into non-articulating and articulating.
Interspinous Devices
Interspinous devices (also known as ‘‘interspinous spacers’’ or ‘‘damping devices’’) are used
for the treatment of low back pain and sciatic
pain in degenerative disease of the lumbar spine
(originating from disck, hernia and facet joints),
but also to treat segmental instability and canal
stenosis. In relation to clinical, leading candidates are patients with neurogenic intermittent
claudication that includes symptoms of radicular
pain on standing and walking, sensation disturbance, and loss of strength in the legs [21–23].
Rational use of interspinous devices, positioned
between the spinous processes is based on the
observationthatinmanypatients with canal stenosis
pain improves with the motions offlexion thanks to
discharge of load on posterior annulus (considered
in many cases the ‘‘pain generator’’). These implants
reduce the load on disk and facet joints, with significant increase in foraminal height, width and
cross-sectional area; in inter-vertebral angle; in disk
space height and with decrease in epidural pressure
and nerve root compression.
As a result, the ideal patients candidates for
dynamic stabilization with interspinous spacers
present position-dependent pain relieved with
flexion.
Placement procedure on the rear wall of the
bodies between spinous processes at the symptomatic or adjacent level to fusion is performed
under general anesthesia, sometimes local in
elderly patients for whom extensive open surgery may present great surgical risk.
The surgery of short duration (about 30 min)
provides a small skin incision of 3–4 cm. The
placement is simple, because it involves only the
posterior surface of the spine without ‘‘opening’’
spinal canal.
This surgery substantially has not any risk;
specific complications are fracture of spinous
process, implant migration, infection and dural
injury
In addition, these devices are relatively easy
to remove and often do not preclude the use of
other devices and therapies. In many cases it can
also be used in combination with foraminal
selective decompression.
Implantation is less invasive than disk
arthroplasty or conventional fusion, and the
procedure leaves both the anterior and posterior
longitudinal ligaments intact. In some devices,
the supraspinous ligament and even portions of
the interspinous ligament are left intact.
Materials mainly used are X-stop, Wallis,
Viking, DIAM, Coflex, Ellipse, In Space.
X-Stop
X-Stop is the most commonly used interspinous
decompression device. It consists of two parallel
lateral wings that prevent itself lateral migration
connected by a titanium rod or spacer. During
implantation, the rod is inserted in transverse
way, penetrating the interspinous ligament. It is
constrained anteriorly by the lamina, craniocaudally by the spinous processes, and posteriorly by the supraspinous ligament. The rod
places the patient in slight flexion, while limiting
extension. The flexion obtained by the insertion
24 T. Scarabino et al.
of the device leads to stretching of yellow ligaments and distracting of nerve foramina.
Results of multi-center trials conducted in US
indicated that in patients with pain arising from
neurogenic claudication (a symptom of spinal
stenosis), X-STOP provided significantly greater
pain relief than epidural steroid injections (the
treatment used as a comparative control) [24].
Wallis
Wallis is polietereterketone (PEEK), with elastic
like-bone characteristics, stabilized with two
strips of Dacron. Although it is not truly compressible, properties of material are very close to
the elastic modulus of the posterior spine. The
two strips of dacron embrace the upper and
lower spinous processes, pulled with a special
tool. Compared to other interspinous systems
also allows to enlarge anterior disk space.
In clinical trial, involving 300 patients treated
for recurrent disk herniation, patients whose
incorporated Wallis in second diskectomy had
significantly better results [25].
Viking
Viking is of cylindrical shape and also made of
PEEK, with two upper and lower wings which
allow the fixing of the spinous processes at the
level above and below. To insert the device it’s
necessary to disconnect the interspinous and
supraspinatus ligament then sutured.
Diam
DIAM consists of a silicon core covered by a
polyester sleeve. The core and sleeve are held in
the interspinous space by three mesh bands. Two
of the bands encircle the adjacent spinous processes, while a third encases the supraspinous
ligament.
Packed with compressible material, is not a
true stabilizer because it lacks its own stabilizing
force. It maintains the rigidity of the rear
compartment of the functional unit formed by
the intervertebral disk and interapophyseal joints
finding indication when the size of the root canal
should be preserved.
The silicon device are radiolucent, but radiopaque markers along the superior edge of the
core allow for radiographic identification. A
group from Italy recently reported that in a series
of 912 patients, there was a significant reduction
in pain and a high rate of patient satisfaction. In
their series, there was a 3.8 % complication rate
including infections, fractures in the spinous
processes, and removal of the device combined
with fusion [26].
Coflex
The Coflex is a U-shaped titanium implant that
is placed into the interspinous space with clips
on the upper and lower margins that allow the
locking. While the height of the device distracts
the foraminal opening, the ‘‘U’’ shape is
designed to allow controlled movement in forward and backward bending. Implantation of
this device is more invasive than others,
involving resection of both interspinous and
supraspinous ligaments. The results, based on
pain and patient satisfaction, are favorable [27].
Ellipse
Ellipse is mixed material, PEEK and titanium,
consisting of a main body and a closure module.
The main body cranially and caudally has two
saddles that facilitate the housing of the spinous
processes. It also has a specially formed groove
to allow the closure module to rotate inside it.
Once placed between the spinous processes, the
device is closed by rotating the closure module
into the special groove. The locking of the closure on the main body is through a ‘‘tab’’
directly formed on this, that prevents slippage.
Its geometry allows a lateral insertion with
minimally invasive surgical technique, avoiding
the excision and removal of the supraspinatus
and interspinous ligaments.
3 Surgery 25
In-Space
In-Space consists of PEEK radiolucent body and
titanium alloy (TAV) screw and wings to allow
radiographic assessment of the correct installation. Turning the screw, the implant closes and
the wings are deployed along the spinous processes. The wings prevent ventral and lateral
migration of the implant while the intact supraspinous ligament prevents dorsal displacement.
The percutaneous lateral approach not allow
stripping of the paraspinal muscles. Moreover
supraspinous ligament is left intact, interspinous
ligament is only pierced to the size of the
implant, no bone needs to be removed to facilitate the insertion of the implant.
3.2.4 Posterior Pedicle Fixation-based
Dynamic Stabilization Devices
Posterior dynamic stabilization, or ‘‘soft stabilization’’, attempts to restore functional stability
while maintaining some or all intersegmental
motions. These devices incorporate radiopaque
posterior pedicle screws, with limited motion
allowed. Primary indications are symptomatic
lumbar spinal stenosis and degenerative spondylolisthesis. The Dynesys device is the most
widely used in the dynamic posterior stabilization [4]. It can be used in up to five contiguous
levels from L1 to S1. It employs two titanium
pedicle screws at each treated level. The screws
at adjacent levels are connected by a radiolucent
polyethylene terephthalate cord surrounded by a
polycarbonate urethane spacer. The cord stretches to allow some motion but limits flexion at
the treated level. The spacer consents for some
compressibility thereby allowing limited flexion.
3.2.5 Facet Replacement Devices
Disease offacet joints leads to narrowing of spine
canal, narrowing of the foramina, and spondylolisthesis. In some patients, there is degeneration
of facets with relative preservation of the disk.
In this setting, it is biomechanically undesirable
to remove the disk. These patients should be
treated with decompression that however, can
lead to instability often making necessary concurrent fusion. Facet replacement devices have
been created in an attempt to replace only the
diseased elements in facet arthropathy and spinal
stenosis while maintaining normal or near-normal biomechanics of the spine [4].
3.2.6 Vertebral Body Replacement
Vertebral body replacement may be necessary
after a resection (corpectomy) because of tumor,
infection, or major trauma [3, 28]. The device
may be an expandable hollow cylinder packed
with bone graft material or cement. Stackable
carbon-fiber-reinforced polymer cages are
radiolucent, and the metallic rods that hold them
together mark their position as do radiopaque
metallic dots. Vertebral body replacement may
involve one or more segments. Lateral, anterior,
or posterior screws with plates or rods are
inserted for additional stability.
Anterior Cervical Diskectomy and Fusion
The anterior cervical diskectomy and fusion
(ACDF) consists of removal cervical disk herniation through an anterior approach to relieve
spinal cord or nerve root pressure and alleviate
corresponding pain, weakness, numbness and
tingling. Fusion is almost always done at the
same time as the diskectomy in order to stabilize
the cervical segment.
The general procedure for ACDF includes the
following steps: (1) anterior surgical approach,
(2) disk removal, (3) canal decompression, (4)
anterior cervical fusion with insertion of bone
graft into the evacuated disk space [29, 30]. This
latter step prevent disk space collapse and promote growing together of the two vertebrae into
a single unit; thereby it avoids local deformity
26 T. Scarabino et al.
(kyphosis) with preservation of right space for
nerve roots and spinal cord.
While this treatment is most commonly performed in symptomatic cervical hernias, it may
also be done for cervical degenerative disk disease and for multiple levels. This approach has
several advantages like better access to the spine
(the anterior approach can provide access to
almost the entire cervical spine, from the C2
segment at the top of the neck down to the
cervical-thoracic junction), less postoperative
pain (spine surgeons often prefer this approach
for the good access to the spine through
uncomplicated pathway; moreover the patient
tends to have less incisional pain from this
approach than posterior).
A skin incision is made in the front of the
neck, only one thin vestigial muscle needs to be
cut to reach the spine. The limited amount of
muscle division or dissection helps to limit postoperative pain following surgery. Patients typically go home the same day or the following.
Patients should discuss activity restrictions and
rehabilitation with their surgeon.
As with any surgery, there are possible risks
and complications in ACDF. The rate of them is
highly variable and dependent mainly from
individual patient risk factors, such as the condition of the disk, physical condition (bone
strength, diabetes). The main potential risks are:
inadequate symptom relief after the surgery,
failure of bone graft healing to create a fusion
(non union or pseudarthrosis), nerve root damage, damage to the spinal cord, bleeding, infection. Sometimes recurrent laryngeal nerve will
not function for several months after neck surgery because of retraction during the procedure.
This complication can cause temporary hoarseness. The possible retraction of the esophagus
can also produce difficulty with swallowing,
which usually resolves within days but can last
weeks to months. Rarely, it can result in permanent difficulty swallowing. Chance of recurrent hernia is little because most of the disk is
removed.
References
1. Antonacci MD, Eismont FJ (2001) Neurologic
complications after lumbar spine surgery. J Am
Acad Orthop Surg 9:137–145
2. Young PM, Berquist TH, Bancroft LW et al (2007)
Complications of spinal instrumentation.
Radiographics 27:775–789
3. Murtagh RD, Quencer RM, Castellvi AE et al (2011)
New techniques in lumbar spinal instrumentation:
what the radiologist needs to know. Radiology
260:317–330
4. Rutherford EE, Tarplett LJ, Davies EM et al (2007)
Lumbar spine fusion and stabilization: hardware,
techniques, and imaging appearances. Radiographics
27:1737–1749
5. Annertz M, Jonsson B, Stromqvist B et al (1995)
Serial MRI in the early postoperative period after
lumbar discectomy. Neuroradiology 37:177
6. Gallucci M, Caulo M, Masciocchi C (2001) il
Rachide operato. In Compendio di Risonanza
magnetica a cura di Dal Pozzo G, Utet Ed,
pp 1047–1071
7. Arts M, Brand R, van der Kallen B et al (2011) Does
minimally invasive lumbar disc surgery result in less
muscle injury than conventional surgery? A
randomized controlled trial. Eur Spine J 20:51–57
8. Bilsky HM (2000) Transpedicular approach for
thoracic disk herniations. Neurosurg Focus 9:E3
9. Celestre PC, Pazmiño PR, Mikhael MM et al (2012)
Minimally invasive approaches to the cervical spine.
Orthop Clin North Am 43:137–147
10. Hirano Y, Mizuno J, Takeda M et al (2012)
Percutaneous endoscopic lumbar discectomy: early
clinical experience. Neurol Med Chir 52:625–630
11. Jho HD (1999) Endoscopic transpedicular thoracic
discectomy. J Neurosurgery Spine 91:151–156
12. Davis AR (1994) A long-term outcome analysis of
984 surgically treated herniated lumbar discs.
J Neurosurg 80:415–421
13. Hauger O, Obeid I, Pelé E (2010) Imaging of the
fused spine. J Radiol 91:1035–1048
14. Hunter TB, Yoshino MT, Dzioba RB et al (2004)
Medical devices oh the head, neck and spine.
Radiographics 24:257–285
15. Nakashima H, Yukawa Y, Ito K et al (2011)
Posterior approach for cervical fracture-dislocations
with traumatic disc herniation. Eur Spine J
20:387–394
16. Lee CK (1993) Accelerated degeneration of the
segment adjacent to a lumbar fusion. Spine
18:2106–2117
17. Lee CS, Hwang CJ, Lee SW et al (2009) Risk factors
for adjacent segment disease after lumbar fusion. Eur
Spine J 18:1637–1643
3 Surgery 27
18. Stoll TM, Dubois G, Schwarzenbach O et al (2002)
The dynamic neutralization system for the spine: a
multicenter study of a novel non-fusion system. Eur
Spine 11:S170–S178
19. van den Erenbeemt KD, Ostelo RW, van Royen BJ et al
(2010) Total disc replacement surgery for symptomatic
degenerative lumbar disc disease: a systematic review
of the literature. Eur Spine J 19:1262–1280
20. Murtagh RD, Quencer RM, Cohen DS et al (2009)
Normal and abnormal imaging findings in lumbar
total disk replacement: devices and complications.
Radiographics 29:105–118
21. Lindsey DP, Swanson KE, Fuchs P et al (2003) The
effects of an interspinous implant on the kinematics
of the instrumented and adjacent levels in the lumbar
spine. Spine 28:2192–2197
22. Sobottke R, Schlüter-Brust K, Kaulhausen T et al
(2009) Interspinous implants (X Stop, Wallis, Diam)
for the treatment of LSS: is there a correlation
between radiological parameters and clinical
outcome? Eur Spine J 18:1494–1503
23. Wilke HJ, Drumm J, Häussler K et al (2008)
Biomechanical effect of different lumbar
interspinous implants on flexibility and intradiscal
pressure. Eur Spine J 17:1049–1056
24. Zucherman JF, Hsu KY, Hartjien CA et al (2005) A
multicenter, prospective, randomized trial evaluating
the X stop interspinous process decompression
system for treatment of neurogenic intermittent
claudicatio: two-year follow-up results. Spine
30:1351–1358
25. Senegas J (2002) Mechanical supplementation by
non-rigid fixation in degenerative intervertebral
lumbar segment: the Wallis system. Eur Spine J
11:S164–S169
26. Guizzardi G, Petrini P, Fabrizi AP (2005) The use of
DIAM (interspinous stress-breaker device) in the
DDD: Italian multicenter clinical experience. Spinal
Arthroplasty Society, New York
27. Eif M, Schenke H (2005) The interspinous-U:
Indications, experience, and results. Spinal
Arthroplasty Society, New York
28. Chacko AG, Joseph M, Turel MK et al (2012)
Multilevel oblique corpectomy for cervical
spondylotic myelopathy preserves segmental
motion. Eur Spine J 21:1360–1367
29. Hernandez R, Neroni M, Fiore C et al (2001)
Cervical arthrodesis with interbody fusion titanium
cages for cervical degenerative disease. Acta Medica
Romana 39:383–394
30. Kim K, Isu T, Morimoto D et al (2012) Cervical
anterior fusion with the Williams-Isu method:
clinical review. J Nippon Med Sch 79:37–45
Imaging Modalities
Saverio Pollice, Michele Maiorano, Angela Lorusso,
Francesco Nemore and Tommaso Scarabino
4
Imaging is important in the pre-surgery as a
‘‘guide’’ for the surgeon or interventional radiologist, both in post-surgery, when the neuroradiologist becomes the ‘‘supervisor’’ of the
therapeutic route. The ‘‘finished product’’ of a
treatment, can be precisely documented with
imaging. In particular, the post-operative imaging examination evaluates position of implants,
adequacy of decompression, fusion status and
potentially complications. The available methods of imaging are the X-rays (XR), computed
tomography (CT) and magnetic resonance (MR).
Modality and protocol used to image the postoperative spine depend on the district, clinical
question, type of disease treated and instrumentation used [1, 2].
4.1 X-ray
XR is the starting point in diagnostic imaging
thanks to its peculiarities: non-invasive, low
cost, wide availability, easy to perform and
interpret, optimum view of the containing, ideal
for check accurate spinal alignment without
S. Pollice M. Maiorano A. Lorusso
T. Scarabino (&)
Department of Radiology—Neuroradiology,
‘‘Lorenzo Bonomo’’ Hospital, Andria, Italy
e-mail: tscarabino@hotmail.com
F. Nemore
Department of Radiology, ‘‘San Nicola Pellegrino’’
Hospital, Trani, BT, Italy
synthetic means artifacts. It should be performed
to assess bone component, exact position of the
devices (for example in the stabilization) or
distribution of used materials (such as cement
post-vertebroplasty) [3]. XR have a few limitations: it can not evaluate soft tissue structures
(such as neural elements, recurrent disk herniations or scar tissue) and it has low value in the
non-instrumented postoperative spine assessment. XR also can not be used to reliably
exclude the presence of bone metastases or of
cauda equina compression, both of which are
common indications for postoperative MR.
During follow-up is essential the comparison
with previous studies in order to detect any
changes in component position, bony alignment,
implant fractures, changes in the bone-implant
interface, which may signify the imminent failure of a device or other complications.
Usually this study is performed in the upright
position in antero-posterior, lateral and obliquelateral proiection and sometimes is associated
with a dynamic study in flexion–extension. In the
latter case, radiographic evidence of instability
includes translation of 3 mm or more in L1–L4
vertebrae, 5 mm at theL5–S1 interspace, or more
10 of angulation between adjacent vertebrae.
4.2 Computed Tomography
CT is considered the modality of choice for
imaging bone detail and assessing osseous formation and implant position. For this reason CT
T. Scarabino and S. Pollice (eds.), Imaging Spine After Treatment,
DOI: 10.1007/978-88-470-5391-5_4, Springer-Verlag Italia 2014
29
30 S. Pollice et al.
has an important role in postoperative assessment
of fusion surgery [4]. CT is useful for detecting
and grading spinal and/or foraminal stenosis and
in follow-up after surgery. Moreover CT after iv
contrast media provides reliable differentiation
between postoperativescarring and recurrent disk
herniation [5].
CT is often used in case of inadequate XR
evaluation and in the study of critical areas. It
provides better evaluation of fusion progression
than XR.
Multiplanar and three-dimensional reconstructions increase CT diagnostic power. Some
authors have also tested the intraoperative 3D
scans after pedicle screw positioning in order to
avoid false placement and primary neurovascular damages.
Immediate correction of misplaced screws
decreases the secondary revision rate of patients
and prevents secondary neurovascular problems,
instability or dislocation of the fixateur [6].
Unfortunately, quality of imaging can sometimes be affected by the presence of artifacts due
to metallic devices that are currently less
noticeable thanks to new materials (titanium), or
by using special projections (perpendicular to
the orthopedic implant so that the beam transverses the metallic cross section with the
smallest diameter) or appropriate imaging algorithms (use of high peak voltage, high tube
current, narrow collimation) and reconstruction
(use of thick sections, lower kernel values) [7].
4.3 Magnetic Resonance
MRI is test of choice in the evaluation of postsurgical procedures in patients with persisting or
recurrence of pain with characteristics similar or
different than previous surgery [8]. MR allows,
by virtue of its known peculiarities (high sensitivity, multi-planarity, multi-parametric, high
and contrast spatial resolution, accurate simultaneous display of containing and contained),
correct diagnosis and therefore precise therapeutic indications. MRI is essential in assessing
the involvement of the nervous tissue in the
pathology to be treated. Compared with XR and
CT, MR imaging is much more accurate in the
evaluation of tissue enhancement (allowing
easier discrimination between herniation versus
epidural fibrosis) [9], bone marrow edema and in
documenting and monitoring complications such
as soft tissue and joint inflammation, nerve root
enhancement, hemorrhage, spinal stenosis.
Artifacts by ferromagnetic material, in the
past often present and able to affecting imaging
quality, are currently less evident thanks to new
synthesis materials (titanium) and to the use of
particular sequences less sensitive to magnetic
susceptibility (Fast SE). Therefore they no
longer represent an obstacle or a contra-indication to MRI examination [10–13].
For an clear interpretation of post-surgery
imaging is necessary to know the technical and
methodological aspects of MRI of the treated
spine, that does not differ significantly from a
basic study including conventional sagittal and
axial images T1 and T2 weighted (FSE), shortly
affected by artifacts caused by metal or any other
surgical material used [14, 15].
In the presence of synthesis means (clips,
prostheses, stabilizers), SE and GE sequences
should be avoided because particularly sensitive
to magnetic susceptibility. Another important
recommendation to be followed is the use, after
the execution of a basic study of TSE T2 with
Fat Saturation (or STIR) to best emphasize
pathology within spinal or epidural adipose tissue [16]. For the same reason it is essential,
especially in the case of inflammation the use of
the contrast agent in TSE T1 Fat Sat [5, 17]. The
use of fat suppression in TSE T2 and TSE T1
after contrast medium increases the sensitivity,
emphasizing the characteristic ‘‘edema pattern’’
index of bone bruising, inflammation or cellular
infiltration [18, 19]. New and advanced methods
of MR imaging, such as diffusion and perfusion,
already tested in the study of the brain, are
recently developed in the study of the column
with not yet definitive results [20–22].
In suspected impaired post-treatment spinal
mobility and staticity is useful specific instrumental study through new open MRI systems,
low and medium intensity magnetic field, which
allows a study even in the upright position.
4 Imaging Modalities 31
Conventional MR imaging has the significant
limitation to study the spine in a position of relative rest because images are acquired with the
patient in supine position and often the pain
occurs orgets worse inthe upright position. Some
CT/MR studies showed 30 % false negatives for
which in 1/3 of cases MR performed only in the
supine position is not able to answer the clinical
question. In these subjects the study of the spine
in the upright position therefore arises as complementary. Until recently, the only practicable
examination in the upright position of the spine
was X-ray. In recent years portable devices for
axial loading of the lumbar spine in CT and MR
were developed in order to assess the amplitude
of the spinal canal in a more physiological state
like in the erect position or by using axial loading
either by flexion–extension [23–26].
It was shown that the space within the canal
is posture dependent because there is a significant reduction of spine cross-sectional area
during axial loading resulting in increased
diagnostic specificity of the spinal stenosis.
Actually dedicated MRI allow to perform
examination in the upright position but they are
not much diffused [27]. Thereby it is possible to
assess in a dynamic manner the various components of the column and its relationship in
different stages of the movement by virtue of the
variation of a number of physiological variables
such as reduction of the lumbosacral angle
(normal value 120–180), increase of the lordosis angle (normal value 50), reduction of the
thickness of the intersomatic disk and the size of
the dural sac. These findings can be detected
precisely in the passage from the supine to
upright position.
It is possible to document also spondylolisthesis and radicular conflicts, not detectable with
a static study or to evidence pathological static
and mobilitysubsequent tohigh invasive surgery,
even if also minimally invasive and conservative
treatment may arise microinstability for the
excision of muscle-ligamentous structures.
These structures, richly innervated, actively
participate in the continuous postural adjustments of the spine, keeping the statics and
dynamics. Moreover the onset of degenerative
processes in the spinal functional unit as a result
of altered load can result in central and lateral
canal stenosis. MR imaging in the upright
position has some limitations such as the use of
low magnetic field intensity with following not
high images quality and the need of considerable
patient cooperation.
In patient with pacemaker, claustrophobic or
not cooperating or in case of not diagnostic
examination because of artefact, conventional
myelography or CT myelography may be performed. However, after instrumentation of the
lumbar spine, puncture of the lumbar thecal sac
may be complicated by distortion of the anatomy
(scarring, removal of posterior elements, addition of bone graft material) or the presence of
metallic implants. Occasionally in this situation
a cervical puncture is necessary. Following the
injection of contrast material into the thecal
sack, the imaging may be acquired with an angle
to avoid obscuration of the relevant nerve roots
by the implanted devices.
References
1. Gallucci M, Bozzao A, Orlandi B et al (1995) Does
postcontrast MR enhancement in lumbar disk
herniation have prognostic value? J Comput Assist
Tomogr 19:34–38
2. Thakkar RS, Malloy JP 4th, Thakkar SC et al (2012)
Imaging the postoperative spine. Radiol Clin North
Am 50:731–747
3. Venu V, Verinsky AT, Malfair D et al (2011) Plain
radiograph assessment of spinal hardware. Semin
Muscoloskelet Radiol 15:151–162
4. Williams AL, Gornet MF, Burkus JK (2005) CT
evaluation of lumbar interbody fusion: current
concepts. AJNR 26:2057–2066
5. Grane P (1998) The post-operative lumbar spine. A
radiological investigation of the lumbar spine after
discectomy using MR imaging and CT. Acta Radiol
39:2–11
6. Beck M, Mittlmeier T, Gierer P et al (2009) Benefit
and accuracy of intraoperative 3D-imaging after
pedicle screw placement: a prospective study in
stabilizing thoracolumbar fractures. Eur Spine J
18:1469–1477
7. Watzke O, Kalender WA (2004) A pragmatic
approach to metal artifact reduction in CT: merging
of metal artifact reduced images. Eur Radiol
14:849–856