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T. Bräuer
Fig.50.11 Left and right: X-ray bending pictures conrming rigidity in all three curves/ the center: X-ray supine position depicting the real exist-
ing curvatures intraoperatively in a prone position
Fig. 50.12 ALLEN operating table
and if it exceeds 40° (hyperkyphotic), the modier + is assigned. The Lenke classication can be of great help to
Fig. 50.13 Yellow arrow: gear shift positioned prior to penetration of
the pedicle
plan the numbers of vertebrae to fuse (mostly COBB-to­COBB angle in structural curves to conserve motion in the non-structural curve/s also described as “selective fusion”),
50.6 Positioning
however even with optimal pre-operatively planning, reality can show in some cases postoperatively—the need to extend the xation in order for the patient to have proper balanced three-dimensionally.
The patient is supported in a prone position on a radiolucent operating table (e.g., Jackson table or Allen table) (see Fig. 50.13). Positioning of the patient should assure least
50 Posterior Correction ofAdolescent Idiopathic Scoliosis (AIS)
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possible pressure upon the vena cava with the intention of minimalizing intraoperative loss of blood and preventing possible skin lesions due to extensive duration of the opera­tive procedure.
50.7 Surgical Technique
Surgical technique benets a great deal by better understand­ing the pathogenesis of AIS: when reaching puberty, the growth in the anterior wall of the corpus vertebrae in patients with AIS is “outrunning” the growth of the posterior wall resulting in a at thoracic spine with an apical lordosis/ hypokyphosis. The plumb line from C7 falls eventually behind/posteriorly to L5 with a concurrently introduction of an unnatural rotation in the main (structural) curve/s which induces the growth of a hunchback. Nature’s solution to deal with the anteriorly gain in anterior height of the vertebrae in order to prevent imbalance in the sagittal plane appears to give way by emerging a rotation as the minor biomechanical drawback in contrast to sagittal imbalance. The consistent analysis of the origin of AIS (and basically all deformities of the spine) may be a good help in correcting them: the derota­tion of the scoliotic spine removes the hump but at the same time brings back to light the original pathogenesis of AIS, which is the relative, anterior space requirement causing the rotation in the scoliotic spine, so that sagittal balance can be sustained. At the same time, anatomical derotation of the scoliotic spine produces an undesirable hypokyphosis. To avoid this, it is recommended to elongate the posterior struc­tures of the spine starting from the apex of the primary curve, which can be achieved by transporting the pedicle screws on the rods using distraction forceps—closely controlled by intraoperative neuromonitoring.
50.7.1 Approach
A midline incision is performed with the customary subperi­osteal exposure of the posterior bony elements. Scrupulous dissection will be benecial concerning minimizing tissue damage, blood loss, and ultimately providing best possible fusion rate. Blunt dissection with gauze compresses instead of exceedingly usage of wound retractors may be supportive to complete optimal access and walking the thin line between hemostasis and preventable in situ rhabdomyolysis.
50.7.2 Instrumentation
The use of pedicle screws in correction of deformities also in the thoracic spine has become the gold standard in line for reported three column control of the vertebra, improved cor-
onal, sagittal and rotational correction, minimal loss of cor­rection over time, lower pseud arthrosis rates, lower implant failures, and earlier return to activities. Several screw inser­tion techniques are described in the literature, for example, uoroscopic assisted, Funnel technique, intraoperative navi­gation, electronic conductivity device, and freehand place­ment. The choice of the screw insertion technique is up to the personal preference of the surgeon. In the current selected operative case, the freehand technique was chosen which is also a topic of this book and is described in detail. In the fol­lowing gure, the yellow arrow shows the gear shift before the penetration of the pedicle. At the given entry point for the pedicle screw, the cortical part of the lamina dorsalis has been removed beforehand in order to better haptically grasp the cancellous part of the pedicle. The gear shift illustrated here is pointed and bent. The tip points laterally in order to guarantee the integrity of the medial pedicle wall in the best possible way, which assures approx. 65% of the stability of the pedicle screw inserted later, while an intact lateral pedi­cle wall stands for approx. 35% of the stability of the pedicle screw. The gear shift is pushed approx. 10–15mm into the pedicle with alternating rotations of the gear shift to the right and left. Experience shows that light, alternating rotations can facilitate safe and precise penetration, especially in the usually thin, narrow pedicels on the concave side of the sco­liosis. After approximately 10–5mm penetration of the ped­icle with the gear shift, the tip of the gear shift is in the immediate vicinity where the pedicle merges into the verte­bral body. It is recommended to pull the gear shift directly out of the pedicle at this point without any rotational move­ments. The gear shift is turned outside the pedicle with 180° and then inserted into the preformed pedicle screw channel with the tip pointing medially. Continue with the same pres­sure and rotation movements as before to the desired length of the pedicle screw channel. Although modern pedicle screw designs have self-tapping threads, it is preferable to use a pre-tap with a diameter 1 millimeter minor than that of the intended pedicle screw diameter to achieve a press-t situation, and thus optimum stability of the pedicle screw (Figs.50.14, 50.15, 50.16, 50.17, 50.18, 50.19, and 50.20).
The red arrow points to another gear shift that palpates the lateral boundary of the superior articular process and is then inserted from proximally to distally into the costo- transversal joint and then further pushed with nimble pressure approx. 10mm. A slight movement of the gear shift from lateral to medial allows the haptic as well as optical representation of the lateral pedicle wall. Usually it is recommended to select the entry point for the pedicle screw approx. 2mm medial from the lateral pedicle wall displayed with the gear shift. After thorough probing and integrity testing of the ve walls that dene the screw channel (oor-superior-inferior-lateral­medial), the pedicle screw is inserted (for FAS up to the resulting stop, i.e., when the oor of the screw head lies per-
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Fig. 50.14 Yellow arrow: gear shift positioned prior to penetration of
the pedicle. Red arrow: indicating gear shift palpating the lateral boundary of the superior articular process unveiling the lateral border of the pedicle
T. Bräuer
Fig. 50.17 Ideally, the appropriate rod can be placed on the spinal pro-
cesses in the given surgical case indicating a proper t
Fig. 50.15 After thoroughly palpating of the preformed pedicle screw
channel with a probe follows the introduction of the pedicle screw
Fig. 50.16 The ttingly adjusted rod should compare to the given
anatomy in the surgical site
Fig. 50.18 Mount the rod reducer on the screw heads and insert
therod
Fig. 50.19 With the help of rod reducers, the rod is consistently and
without substantial force transfer brought into the screw heads and secured with the set screws
pendicular to the dorsal lamina and stops). When all planned pedicle screws are set, the rod is adjusted. For practical rea­sons, it may be helpful to adjust the rod at rst for the side on which the concavity of the primary curve is found. The spi­nal processes are an additional aid in modifying the rod, as can be seen in the gure, the adjusted rod follows its course. Several rod reducers are placed on the screw heads to
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Fig. 50.20 90° rotation of the rod with the rod holder clamps from
medial to lateral
minimize the load on the screws and their corresponding mobility segments. The rod is then inserted into the rod reducer. With the help of the rod reducers, the rod can be guided consistently and without signicant effort into the heads of the pedicle screws. The rod holder forceps are used to rotate the rod by 90°. The rod is secured in the pedicle screw heads during rotation with set screws on top. The last plastic shape change of the rod is performed with the coronal benders to achieve further correction in the coronal plane. The other rod is applied in the same way on the contralateral side and ttingly adapted in its shape. The consecutive dero­tation takes place directly at the motion segment which is dened by two vertebrae with the vertebral disc between them. Four counter- torques are placed on each of the four attached pedicle screws in the motion segment. The exten­sion of the relatively shortened posterior structures of the scoliotic spine is done bilaterally with distraction forceps between the proximal and distal pedicle screw pairs, while the set screws are loosely attached to the pedicle screw heads. After the distance between all four pedicle screws have been elongated on the rods to the matching height, the two counter torques on the convex side are carefully moved in the direc­tion of the anterior spine, while the two counter torques on the concave side are guided in the direction of the spinal pro­cess at the same time. The inclination angle of all four pedi­cle screws in the motion segment in relation to the midline structures can be clearly seen from the long counter-torques. Ideally, with the same inclination angle, the pedicle screws are on the identical level in sagittal direction; in coronal level, the screws point with the tip toward the center of the anterior vertebral body. In this way, the achieved derotation can be visualized before the intraoperative X-ray control. Within the instrumented spine, all other motion segments are derotated in the same manner. The technique with four coun­ter torques, compared with similar derotation techniques, may allow also a turning force within the intervertebral disc of the motion segment, which could optimize the derotation even more if desired. Once the three-dimensional correction has been completed, an X-ray inspection can be carried out (Figs.50.21, 50.22, 50.23, 50.24, 50.25, 50.26, and 50.27).
Fig. 50.21 It follows both the denite prole adjustment of the rod
and simultaneous an additional correction of the spinal deformity by using the coronal benders
Fig. 50.22 Customized DVR technique with four counter torques
mounted on four screw heads in the motion segment
Fig. 50.23 Elongation of the motion segment by enlarging the dis-
tance of the screw heads on the rods performed with distraction forceps
Fig. 50.24 Final check of the performed deformity correction (visual
and with x-ray)
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Fig. 50.25 Decortication and autologous bone transplantation inside
the performed instrumentation
T. Bräuer
Operation is concluded by a consistent bilateral decorti­cation of the lamina dorsalis within the instrumented spinal column in order to achieve optimal spondylodesis.
50.7.3 Postoperative Treatment
The postoperative therapy involves an effective pain treat­ment which in turn enables an early and optimal mobiliza­tion of the patient. The intrathecal morphine instillation carried out by the surgeon at the start of the operation and/or the introduction of two EDAs in the spinal canal after per­formed decortication of the instrumented spine can provide
Fig. 50.26 Preop. X-rays showing LENKE type 4CN Triple Major
50 Posterior Correction ofAdolescent Idiopathic Scoliosis (AIS)
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Fig. 50.27 2year postop. X-ray
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T. Bräuer
satisfactorily postoperative pain treatment accompanied by Paracetamol, morphine, and morphine-like drugs, as well as short-term use of NSAIDs. Total postoperative admission time is usually expected to be 4–7days.
50.8 Tips andTricks
• Operative 3D corrections of spinal deformities pose highly complex challenges to the surgeon. The acquisi­tion of the necessary skills may require a correspondingly longer period of time and is undoubtedly made easier by a targeted training at institutions with a sufciently high volume of deformity interventions to be performed.
• As is so often the case in surgical disciplines, a both well­designed and performed approach pays off in the correc­tion of spinal deformities as well: the overview of the surgical site considerably facilitates more precise and easier placement of the pedicle screws, enables more atraumatic surgery by taking into account the anatomical structures, which in turn decreases signicantly tissue damage— hence take down intraoperative blood loss— and benets the patient in recovering faster.
• When placing the pedicle screw at the respective level, it may be recommended to consider the potential entry point of the pedicle screw on the contralateral side while simultaneously adjusting the intended direction of the pedicle screw channel on the ipsilateral side; ideally, the “virtual” pedicle screw channel on the contralateral side and the real one on the ipsilateral side should point toward each other. This procedure deems effective in preventing misplacement of the pedicle screw with either undesirable proximal penetration of the pedicle into the intervertebral disc or distal penetration which may compromise the nerve root.
• Considering the potential entry points of the pedicle screws before preparing the actual screw channel allows a smoother placement of the pedicle screws in line to each other. The subsequent insertion of the rod is then made considerably more convenient.
• Both of the above mentioned advices for placing the ped­icle screws from S1 to Th1 may be of assistance to use
polyaxial screws (MAS), as well as exclusively monoax­ial screws (FAS) in extensive constructs.
• The mutually mixing of MAS and FAS in longer con­structs should be carefully considered, as the signicantly greater distance between the MAS-screw head (measured from the lamina dorsalis to the lower border of the inserted rod) compared to the FAS-screw head causes a hypo­mochlion (center of rotation of a joint) in the MAS-screw head which may give rise to the risk of pull-out moment in FAS.
• Self-image and self-understanding of the adolescent patients is—at a time when physical perfection is openly favored—far more negatively inuenced by the observ­able hump than by the scoliosis/spinal curvature itself. The trade-off in the successful de-rotation of the hump can lead to a concurrent undesired intensication of the already preoperatively existing hypokyphosis. The exten­sion of the spinal posterior structures with pedicle screw transport on rigid CoCr rods can counteract the formation of hypokyphosis but cannot completely protect against it. An optimal and patient satisfactory derotation of the hump has probably been achieved at the point where fur­ther derotation would fall short of the preoperative exist­ing kyphosis, and thus threatening a stable sagittal balance of the spine.
References
1. Akbarnia Y. Thompson: the growing spine. Berlin Heidelberg: Springer-Verlag; 2011.
2. Danielsson AJ.Natural history of adolescent idiopathic scoliosis: a tool for guidance in decision of surgery of curves above 50°. J Child Orthop. 2013;7:37–41.
3. Dunn J, Henrikson NB, Morrison CC, etal. Screening for adoles­cent idiopathic scoliosis evidence report and systematic review for the US preventive services task force. JAMA. 2018;319(2):173–87.
4. Konieczny MR, Senyurt H, Krauspe R.Epidemiology of adolescent idiopathic scoliosis. J Child Orthop. 2013;7:3–9.
5. Weiss HR, Karavidas N, Moramarco M, Moramarco K.Long-term effects of untreated adolescent idiopathic scoliosis: a review of the literature. Asian Spine J. 2016;10(6):1163–9.
6. Wong HK, Tan KJ.The natural history of adolescent idiopathic sco­liosis. Indian J Orthop. 2010;44(1):9–13.
Thoracic Vertebrectomy andSpinal
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Reconstruction Via Posterior orCombined Approaches
M.Ruf, J.Petrovics, G.Ostrowski, andT.Pitzen
51
51.1 Introduction and Core Message
Thoracic vertebrectomy and spinal reconstruction via posterior or combined approaches is a demanding tech­nique for surgical treatment of spinal tumors that require a complete resection of the entire vertebra, including the posterior structures (lamina, facet joints, transverse pro­cesses, pedicles) as well as the anterior structures (verte­bral body). This entire en bloc vertebrectomy or spondylectomy entails a complete disruption of the con­tinuity of the spine with severe instability. Depending on the extension of the underlying pathology, the resection comprises one or more vertebrae, usually with resection of the adjacent ribs within their proximal part. This tech­nique allows for resection of tumors in one piece includ­ing a healthy layer (marginal or wide resection). There is some evidence that local recurrence is reduced and long-term survival is more probable [13]. However, the technique creates a relevant instability necessitating a biomechanically sound reconstruction that is able to take loads and to withstand exion/extension, lateral bending, and left- right axial rotation.
51.2 Indication
• Primary malignant tumors.
• Semimalignant tumors.
• Isolated spinal metastasis with long life expectancy.
M. Ruf (*) · G. Ostrowski Center for Spine Surgery, SRH Klinikum Karlsbad­Langensteinbach, Karlsbad, Germany e-mail: michael.ruf@srh.de
J. Petrovics · T. Pitzen Center for Spine Surgery, Orthopedics, and Traumatology, SRH Klinikum Karlsbad- Langensteinbach, Karlsbad, Germany
51.3 Contraindication
• Tumor inltration of the spinal cord.
• Tumor inltration in essential adjacent organs.
• Multiple metastasis (relative).
• Prognosis infausta.
51.4 Technical Prerequisites
Fluoroscopy, radiolucent operating table, thoracotomy resp. laparotomy equipment, intraoperative electrophysiological monitoring (SSEP/MEP), vertebral body replacement devices, adaptable to every size of defect (titanium mesh cages (Harms), expandable cages), posterior instrumentation with different diameters, transition rods if necessary at the cervicothoracic region.
51.5 Planning
Conventional radiographs, computed tomography, and MRI are essential to assess localization and extension of the tumor. Computed tomography of brain, thoracic chest, and abdominal cavity as well as bone scintigraphy are necessary to exclude further tumor and metastases, so widespread dis­ease. Using all radiographic information, the border of the tumor is exactly identied. Every vertebra that is involved has to be included completely into the intended resection, also including affected ribs and surrounding soft tissue with a wide safety distance. As the vertebra contains the spinal cord, the area has to be dened where the bony ring can be opened with sufcient distance to the tumor (Fig. 51.1). Then an appropriate approach is chosen to remove the tumor in one piece (posterior or combined). In tumors with a pro­nounced perfusion, segmental arteries above and below the feeding artery, as well as the feeding artery itself, should be embolized preoperatively. Pre- and intraoperative neuro­monitoring (SSEP, MEP) is strongly recommended.
© Springer-Verlag GmbH Germany 2023 U. Vieweg, F. Grochulla (eds.), Manual of Spine Surgery, https://doi.org/10.1007/978-3-662-64062-3_51
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A score is proposed as a tool for surgical strategy for metastatic spine tumor, including grade of malignancy, visceral metastases, and bone metastases. Tomita et al. advised the surgical classication of spinal tumor (Figs.51.2 and 51.3) based on the pattern of local vertebral tumor progression [4].
The Spinal Instability Neoplastic Score (SINS) was developed for assessing patients with spinal neoplasia. It identies patients who may benet from surgical consulta­tion or intervention. It also acts as a prognostic tool for surgi­cal decision making [5].
Fig. 51.1 Artist’s view to illustrate preoperative planning of the open-
ing of the spinal canal with sufcient distance to the tumor. The canal is opened at the position of the gaps, thus giving a safety margin around the tumor mass
51.6 Surgical Technique
Total en bloc vertebrectomy is the most aggressive surgi­cal treatment for spinal tumors. It comprises a complete resection of the posterior structures and stabilization by a posterior approach, as well as the resection of the verte­bral body via costotransversectomy or an additional ante­rior approach.
51.6.1 Posterior Approach
Tumor lesions that do not exceed to adjacent structures can be resected by a posterior approach with costotransversec­tomy [6]. This technique provides an adequate exposure of all three columns through a single posterior approach. It allows for en bloc corpectomy and sufcient stabilization with anterior support. The spinal cord can be observed dur­ing the whole resection maneuver. A clear disadvantage of the procedure is the limited visualization and control of the great vessels especially when the tumor exceeds the border of the vertebral body.
• Patient in prone position on radiolucent table under gen­eral anesthesia.
• Midline skin incision and subperiostal dissection of mus­cles far lateral to expose the proximal ribs. In case of tumor expansion to the posterior muscles, dissection leaves the muscles at the resectate.
• Placement of pedicle screws typically two levels below and above affected vertebra/vertebrae.
Fig. 51.2 Tomita’s surgical
classication of spinal tumors [4]
Type 1
vertebral body
Type 2
pedicle extension
Type 3
body-lamina ext.
Intra-
Compartmental
Type 4
epidural ext.
Type 5
paravertebral ext.
Type 6
2-3 vertebrae
Extra-
Compartmental
Multiple
Type 7
51 Thoracic Vertebrectomy andSpinal Reconstruction Via Posterior orCombined Approaches
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Minimum requirement :
Prognostic Scoring System
Factor
Point
Fig. 51.3 Surgical strategy for spinal metastasis [4]
1
2
3
Primary
tumor
slow
growth
moderate
growth
rapid
growth
Mets. to vital
organ
no met : 0
controllable
uncontrollable
Bone
mets.
isolated
multiple
ECOG Performance Status
Karnofsky Performance Scale:
Total
P. Score
2
3
4
5
6
7
8
9
10
or
LifeTreatment
ExpentacyAim
2y <
1−2y
6−12m
< 3m
0
0
Long-term
local control
Middle-term local control
Short-term
palliation
Terminal
care
3
30
5
0%
Surgery
En bloc exc.
Debulking
Palliative
decomposition
No surgical
treatment
Fig. 51.4 Artist`s view for blunt dissection around the vertebral body
• The ribs on the affected level are transected lateral to the costotransverse joints with sufcient distance to an even­tual tumor inltration.
• The pleura is bluntly separated from the ribs and the ver­tebra. The aorta is carefully dissected from the anterior aspect of the vertebral body (Fig.51.4). The segmental vessels are ligated if necessary.
• Blunt spatulae are inserted to protect the anterior lying vessels (Fig.51.5).
• The lamina, facet joints, and pedicle are now cut and removed according to the preoperative planning (Fig. 51.1). The spinal cord and the nerve roots are visualized.
Fig. 51.5 Artist`s view of how the spatula protects the anterior
structures
• The nerve roots at the affected level(s) are ligated and cut.
• The disks above and below the tumor-inltrated vertebra/ ae are incised and removed from both sides including the posterior longitudinal ligament. A temporary rod is inserted for stabilization alternatingly at the contralateral side.
• The spinal cord is carefully dissected from the posterior wall.
• When the resection of the vertebral body is intended by the posterior approach, it is now carefully rotated around the dural sac and removed en bloc (Fig.51.6).
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