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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_583_Библиотеки_им_академика_М_И_Перельмана
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ab
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S. Kroppenstedt and U. Vieweg
Fig. 66.7 Insertion of cancellous bone graft or bone substitute into the
disk space using a funnel
Fig. 66.8 Introduction under interspinous distraction of a boomerang
cage (TLIF Cage) with an implant holder into the disk space.
Alternatively, distraction with an angled distraction forceps over the
ipsilateral side xed on the pedicle screws
Fig. 66.9 X-ray of a patient with a spondylolisthesis L4/L5 (a), postoperative nal construct with bilateral pedicle screws and TLIF cage and
additional bone substitute (anterior, posterior, and inside the cage) (b, c); CT scans: level L4 (d), disk space level L4 (e) and level L5 (f)
66 Transforaminal Lumbar Interbody Fusion
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ef
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Fig. 66.9 (continued)
References
1. Rosenberg WS, Mummaneni PV.Transforaminal lumbar interbody
fusion: technique, complications, and early results. Neurosurgery.
2001;48:569–74.
2. Mummaneni PV, Rodts GE.The mini-open transforaminal lumbar
interbody fusion. Neurosurgery. 2005;57:256–26.
3. Dhall SS, Wang MY, Mummaneni PV.Clinical and radiographic
comparison of mini–open transforaminal lumbar interbody fusion
with open transforaminal lumbar interbody fusion in 42 patients
with long-term follow-up. J Neurosurg Spine. 2008;9:560–5.
4. Hackenberg L, Halm H, Bullmann V.Transforaminal lumbar interbody fusion: a safe technique with satisfactory three to ve year
results. Eur Spine J. 2005;14:551–8.
Cement Augmentation ofPedicle Screw
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Fixation
JürgenNothwang
67
67.1 Introduction and Core Messages
Reduced bone quality is a particular problem of spine
surgery in older elderly people. To force up anchorage
of pedicle screws as well as pull-out strength, greater
stability and fatigue resistance either a bigger diameter
of (augmentable) screws [1] or cement augmentation
[2] are sufcient tools. Different techniques are
described, but under scientic aspects, none could be
determined as obviously superior [3]. In principle,
augmentation of the screw can be achieved using three
different techniques: [4] cement insertion through cannulated pedicle screws with slots (either open or minimally invasive), or [5] vertebroplasty/kyphoplasty
followed by insertion of the pedicle screw into the
cement (either open or minimally invasive). Several
aspects in cemental techniques have to be respected, so
as cement volume, timing of cementing, screw type,
augmentation technique, and cement materials [1, 6].
Knowing about the advantages of cement augmentation, we should always be aware of the cement-related
complications, which may occur in pedicle augmentation techniques [7]. Meanwhile, new cement materials
are introduced [8, 9] to avoid the respectable drawbacks of PMMA cement, for example, tissue damage
due to polymerization temperature of more than
70 °C. For instance calcium phosphate converts into
hydroxyapatite, and has, due to osteoconductivity and
osteoinductivity, a high capability for bone remodeling
and osteointegration [10] and, in the case of biomechanical testing, shows same pull-out strength as
PMMA [11].
J. Nothwang (*)
Rems-Murr-Klinik Schorndorf, Department for Trauma Surgery
and Orthopedics, Schorndorf, Germany
e-mail: juergen.nothwang@rems-murr-kliniken.de
But all new cement materials have the disadvantage of
a lower viscosity during injection compared to PMMA,
which potentially increases the risk of extravasation.
Furthermore, the biggest disadvantage is that they require
24 h for curing and therefore do not provide enhanced
xation at the time of surgery. Whether light activation of
a certain length with the hands on controlled surgeondetermined polymerization opens new and safe opportunities for augmentation is still to be proved in studies.
67.2 Indications
• Osteoporosis or history of osteoporosis treatment
• Past osteoporotic fracture
• Decrease of bone mineral density to ≤80–100mg/cm
• Rarication of trabecular pattern in CT-scan
• Need for multisegmental stabilization in older patient
• Multilevel osteolytic destruction of the vertebral bodies
(i.e. multiple myeloma, plasmocytoma, NHL)
• Revision surgery of a previous implant
• Systemic diseases causing a deterioration in bone quality
(M. Cushing, diabetes type I, rheumatoid arthritis,
anorexia, primary and secondary hyperparathyroidism,
hyperthyroidism, medication)
• Para-tetraplegia
3
67.3 Contraindications
• Reduced general condition of the patient: pulmonary and
cardiac risk factors (ASA≥IV, NYHA IV)
• Allergy to radiopaque cement
• Severe pre-existing deformity with high degree of osteoporosis of the whole vertebral column
• Pulmonary deciencies with severe disturbance of vascularization, ventilation, or pre-existent pulmonary embolisms
© Springer-Verlag GmbH Germany 2023
U. Vieweg, F. Grochulla (eds.), Manual of Spine Surgery, https://doi.org/10.1007/978-3-662-64062-3_67
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J. Nothwang
Fig. 67.1 Augmentable cannulated
monoaxial pedicle screw (SOCON, Aesculap)
67.4 Technical Prerequisites
• Fluoroscopy, radiolucent operating table (In multilevel
stabilization—i.e., de novo scoliotic deformity—a slidable operating table is helpful.).
• Cannulated pedicle screws with slots or holes (see Figs.
67.1 and 67.2a).
• For the minimally invasive technique, cannulated instruments are essential.
• Connection device for cement delivery (see Figs. 67.2b, c
and 67.3) to the pedicle screw (Luer lock connector).
• Radiopaque low viscosity slow setting cement.
• Trocars for cannulation and vertebroplasty augmentation.
• As alternative kyphoplasty set with ballons
67.5 Basic Biomechanical Messages
• The strength of the vertebrae decreases with age with a
denite relationship between failure stress and vertebral
bone quality. Basically, the mean thickness of vertical trabeculae is preserved with age and the mean horizontal
thickness of trabeculae decreases. Additionally, the mean
distance between horizontal trabeculae and between vertical trabeculae increases. Both aspects are leading to a
dramatic loss of bone strength [11].
• In bone matrix, the amount of glycosaminoglycans
(GAGs) with its major subtype chondroitin sulfate
decreases with age and may lead to signicant reduction
in the tissue-level toughness of bone. The loss of bound
water with aging is in great part attributable to the loss of
GAGs in bone matrix with increasing age [12].
• A 25% decrease in bone quality results in a decrease of
more than 50% in the strength of a vertebra.
• There is a high correlation between the risk of screw
loosening and the density of the bone [13, 14]. The quality of the bone is more important than the design of the
pedicle screws. Below a critical bone density (≤80–
100 mg/cm3), early loosening of the screws is to be
expected. Clinical trials conrmed these biomechanical
results [14, 15].
• Reduced bone mineral density must be addressed in early
endplate failure under axial load. Below 40years of age,
the functional spine unit can bear about 8000N (1800lbf)
of compressive load. Between 40 and 60 years, the
strength decreases to 55% of this value, and above
60years, it decreases to 45% [16].
• Compression forces generated by various loading conditions affect the end plates of the vertebral bodies more
than the vertebral walls. Load related fatigue of the end
plate is an important cause of cut out of pedicle screws
and adjacent level disease.
• By using 2–3 cm3 cement to augment a screw, we can
increase the strength to greater than that of larger diameter screws in normal density bone. (~1600N) [1, 17, 18].
• In biomechanical tests, cement augmentation of pedicle
screws in reduced bone quality has been proved to increase
a
67 Cement Augmentation ofPedicle Screw Fixation
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b
c
Fig. 67.2 Cannulated polyaxial pedicle screw for cement augmenta-
tion (a) (S4, Aesculap) with delivery cannula (b) and connected to the
pedicle screw (c)
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the pull-out strength of the pedicle screws [1, 19, 20] as
well as the fatigue strength of augmented screws in fatigue
tests [14, 21]. Erforderliche Parameter fehlen oder sind
falsch.Erforderliche Parameter fehlen oder sind falsch
[22].
• Clinical studies conrm the biomechanical results of
cement augmentation and indicate high levels of reliability and safety [20, 21]. Nevertheless, pedicle screw
augmentation techniques bear similar risks of extravertebral cement dislocation and pulmonary embolism [23,
24] as it is known for vertebro- or kyphoplasty
procedures.
Fig. 67.3 Application set for pedicle screw augmentation (Aesculap)
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J. Nothwang
67.6 Planning, Preparation,
andPositioning
• Knowledge about bone mineral density or veried osteo-
porosis is helpful.
• Preoperative x-rays and CT-scans are analyzed to evaluate
the diameter and direction of the pedicles and the integrity
of the vertebral wall.
• Patient lies in a prone position (Figs. 67.4, 67.5, 67.6,
67.7, 67.8, and 67.9).
Fig 67.4 Positioning of the
patient
• The position of the pedicles should be veried preoperatively by uoroscopy. Especially in higher thoracic spine,
it is mandatory to verify both planes of the spinal column
free from superpositions.
• The peduncular shape is exposed symmetrically with the
spinous processes in the midline. The end plates should
be free from double contours.
• Navigation tools might support the precision of pedicle
screw application (Figs.67.10).
Fig 67.5 Instrumentation in a cannulated technique
Fig 67.6 Adaption of the connector guided by the K-wire instrumenta-
tion in a canulated technique
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Fig. 67.7 Jamshidi-Needles and slot screw with K-wire: schema and X-ray-imaging
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Fig 67.8 Jamshidi-
Augmentation- Technique and
X-ray-Imaging
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Fig 67.9 Slot-Screw-
Augmentation-Technique and
X-ray-Imaging
J. Nothwang
ba
Fig. 67.10 Postoperative x- rays in ap (a) and (b) lateral view after pedicle screw instrumentation and additional pedicle screw augmentation
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67.7 Operating Technique
67.7.1 Approach
The skin incision depends on the surgical technique chosen.
To avoid the risk of higher blood loss especially in older
patients, percutaneous minimally invasive instrumentation
techniques are becoming more and more important. In our
experience, they have also inuenced the assessment of the
risks to the patient arising from the anesthetic and the
operation.
67.7.2 Minimally Invasive Technique
• We use the same technique as for vertebro- or kyphoplasty:
the skin incision is at the lateral border of the pedicle.
• The incision should have a length of 10 mm to provide
enough space for the holding device of the pedicle screws
and later insertion of the rod.
• Blunt dissection of the soft tissue leads to the cross section of transverse process and facet joint.
• For subsequent steps, the soft tissue should be protected
by a sleeve.
67.7.3 Open Procedure
• Under uoroscopic control, we mark the beginning and
end point of the planned extent of instrumentation.
• The midline incision has to respect these endpoints and
should allow the instrumentation of the pedicles without
stressing the skin.
• The preparation then follows the typical steps as already
described in previous chapters.
• A blunt retractor exposes the eld of operation.
67.8 Instrumentation I: Minimally Invasive
Technique
67.8.1 Trocar Technique
• When the trocar has reached the lateral border of the pedicle, the lateral cortex is opened.
• The trocar is inserted toward the medial border of the
pedicle using a.p. imaging.
• To conrm the ideal positioning of the trocar within the
pedicle, we recommend a “Scottie dog projection” to the
facet joints when a.p. instrumentation has nished.
• In the lateral plane, the trocar should penetrate a little way
past the posterior margin of the vertebral body.
• Preferring a ballon kyphoplasty-technique, the ballon is
expanded and than removed, comparable to typical
kyphoplasty.
• Having ensured the correct position, the trocar can be
replaced with a long-threaded wire.
• With a soft tissue dilator, the access to the pedicle should
be expanded.
• The pedicle is opened toward its entrance into the vertebral body with a tap. In self-taping screws, this step is not
mandatory. In facet joint hypertrophy, taping supports
easy screw application.
• The tap is removed and the trocar is again inserted at least
into the rst third of the vertebral body.
• The length of the screws (i.g. 45–50mm) should be measured and prepared by the operating nurse.
• The low viscosity cement is prepared. The right moment
for application of the cement is comparable to the viscosity characteristics for vertebro- or kyphoplastic cement
application.
• The trocar is lled with cement. The cement is then
injected into the vertebral body under controlled conditions using the inserter. Usually at most 2–3 cm3 is
required for each side.
• Attention: Avoid cement extrusion into the disK and
spinal canal. Stop cement insertion if cement ow into
a vessel is observed.
• The threaded wire is inserted through the trocar and the
trocar can be removed.
• Then the prepared screws can be inserted along the
threaded wires.
67.8.2 Direct Screw Augmentation
• New pedicle screw designs allow cement to be delivered
after the cannulated and perforated pedicle screws have
been positioned.
• (Advantage: more stable connection between the cement
and the pedicle screws through the side opening holes or
slots of the screw.) [6]
• After insertion of the screws, a connector is xed to the
pedicle screw and the cement is injected into the screw.
• The cement ow and anchorage must be observed using
uoroscopy.
• Attention: Do not perforate the anterior cortex of the vertebral body. Do not allow cement to enter the central vertebral vein, which leads directly into the spinal canal.
Because of reduced bending stability, polyaxial screws
are not suitable for bisegmental four-point xation. If
polyaxial screws are preferred in bisegmental stabilization, we recommend a 6-point anchorage to increase rotatory stability and reduce the bearing loads for each screw.
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67.8.3 Open Procedure
• The entrance point on the pedicle is identied and the
pedicle is then opened and penetrated using an awl or trocar. Correct positioning must be checked with
uoroscopy.
• The integrity of the pedicle must be conrmed using the
ball tip probe.
• The subsequent steps are as for the trocar or direct screw
application technique described above.
• Noncannulated screws can be inserted into the tapped
pedicle canal.
• In open approaches, cannulated pedicle screws allowing
direct cement injection are preferred. The screws must not
perforate the anterior cortex.
• The low viscosity cement can be inserted with an adapter
device and a Luer lock connection. A cement gun is
helpful.
• Attention: Following the line of least resistance, the
cement leaves the screw rst through the most proximal
lateral holes (beware: central vein and posterior venous
sinusoids). If there is a slot in the screw, the valve effect is
lower. The distribution of the cement seems to be better, but
the risk of central cement leakage still remains. In our
experience, the safest position of the screws is close to the
anterior wall. The cement distribution and positioning are
quite different between the cementing in a Jamshidi punch
technique and pedicle screw augmentation through slots.
Keep in mind that even under high caution [25] cement
augmentation techniques includes a respectable rate of
complications. In an own one year investigation of 39 cases
with 100 augmented pedicle instrumentations, the rate of
complications due to cement application reached 15% and
included paravertebral cement extrusion, lung embolism,
and, in 2 cases, temporary radicular deciency.
67.9 Tips andtricks
• For cement application, the pedicle screws must be perfectly seated. For instrumentation and cement insertion,
uoroscopic control is essential. If possible, simultaneous uoroscopy in both planes provides maximum
safety.
• In simultaneous instrumentation, we choose a more lateral skin incision to the lateral border of the peduncular
shape (i.a. 2 cm more lateral) to compensate traction
effects of the skin and to achieve a higher degree of
convergence.
• Tapping should only extend as far as the pedicle root and
should not be continued into the vertebral body. The trocar for cement delivery should then be anchored in the
cancellous bone of the anterior vertebral body. This prevents the cement from owing along the tapped canal
toward the pedicle [19].
• The time of cement application often depends on individual experience and special knowledge of the cement
being used. It is likely that this problem can be solved in
future with the help of a viscometer, which is provided by
several companies. It must, of course, be remembered that
these viscometers are normally calibrated to the cement
of the particular company.
• Looking at the failure mode of screw anchoring, the failure is more likely to be at the bone-cement interface in
“soft” cement and the screw-cement interface for “hard”
cement. This indicates that integration of the screw
threads and surrounding trabecular bone is superior in
“soft” PMMA cement [1, 5].
• In our experience, the trocar insertion technique is the safest method of controlling the ow of cement. After pushing the inserter into the trocar, the distribution of the
cement can be followed under uoroscopy. Nevertheless,
some authors reported higher pull-out and fatigue strength
for in situ screw technique than for prelled technique
[19, 21] and described lower risks of cement leakage [26]
• If there are any doubts concerning the precise position of
the trocar, it can be checked in relation to the 45° “Scottie
dog projection.” Especially in L5 with a very lateral pedicle entrance, this uoroscopic control is helpful to conrm correct pedicle penetration.
• In cases of generalized decrease of bone mineral density
due to osteoporosis or tumor diseases (plasmocytoma,
multiple myeloma, NHL), the spine surgeon should consider prophylactic adjacent level vertebroplasty.
• In accordance with the traditional rules governing the
treatment of spinal deformities, instrumentation should
not terminate within the apex of the kyphotic or scoliotic
deformity to avoid progression of the deformity and adjacent level collapse. This so-called windshield-wiper effect
(cutting-out of the screws through the cranial endplate) is
typically observed in clinical practice and due to cranialcaudal cyclic loading of the screws.
• The design of the pedicle screw fenestrations (number
and position of fenestration) seems to inuence xation
strength [26].
References
1. Bostelmann R, Keiler A, Steiger HJ, etal. Effect of augmentation
techniques on the failure of pedicle screws under cranio-caudal
cyclic loading. Eur Spine J. 2017;26:181–8.
2. Kiner DW, Wybo CD, Sterba W, et al. Biomechanical analy-
sis of different techniques in revision spinal instrumentation:
larger diameter screws versus cement augmentation. Spine.
2008;33(24):2618–22.
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