Scoliosis: surgery

Scoliosis: Harrington Endocorrector Operation (1st generation)

Harrington began work on creating his endocorrector in 1947 by studying the anatomy and deformations of the spine. The author concluded that it was fundamentally possible to obtain and maintain correction of the scoliotic spine using a metal structure and used it in 16 patients from 1947 to 1954. Over 5 years, Harrington created 35 (!) modifications of his endocorrector. In 1955-1960, another 46 patients were operated on and an additional 12 modifications of the instrumentation were developed.

The device consists of several components made of stainless steel. It is designed to apply a corrective force to the scoliotic spine using a distractor on the concave side and a contractor on the convex side, as well as, when necessary, a stabilizing system fixed to the iliac crests. At the lower end of the distractor there is a 3/4 inch long section narrowed in accordance with the diameter of the hole of the lower hook, at the upper end there are several circular grooves of such a shape that the upper distraction hook slightly tilts and hooks into one of the grooves, as a result of which it cannot slide down the rod when a distracting axial load acts on the hook. The contractor consists of a threaded rod, hooks with axial holes and hexagonal nuts. The sacral support is a threaded rod, one end of which is sharpened for drilling.

Harrington Operation Technique

Anesthesia is endotracheal. The patient is placed on his stomach. The spine is subperiosteally exposed to the tops of the transverse processes. The places for installing the distractor hooks are specified. For the upper hook, a notch is made in the lower articular process of the selected vertebra. The lower hook is always placed in the lumbar region. Then, places are prepared for installing the contractor hooks. Each hook is grasped with a special instrument and “cut in” at the base of the corresponding transverse process as close as possible to the root of the arch. The lower hooks (usually in the lumbar region) are inserted under the arch or under the top of the lower articular process of the selected vertebra. Then the contractor rod is inserted and the hexagonal nuts are tightened.

The distraction rod is passed through the hole in the upper hook and cephalad until the lower edge of the rod rests against the lower hook. Then the lower end of the rod is inserted into the hole of the caudal hook and distraction is started with the spreader. After distraction, the position of the hooks should be checked. The surgeon works with the distractor and cantractor sequentially until both instruments are in a state of tension. Then a posterior spondylodesis is performed, the wound is sutured layer by layer.

In some cases, it is necessary to stabilize the position of the lower vertebral segments. For this purpose, a lower transverse support rod is used. The access is extended to the sacrum: the sharp end of the transverse rod allows it to be passed through the posterior sections of the iliac bones, and the notch makes it possible to maintain the correct direction of conduction. On one side of the rod, there is a flat platform to prevent torsional displacement caused by the hook of the distractor, which rests on this rod.

After 10-14 days, the stitches are removed and a well-modeled plaster corset is made for 4-5 months.

One of the most famous modifications of the broom was developed by V. Cotrel. The system is a short rod-contractor, which is fixed on the convex side of the deformation, in the area of its apex, and is attached to the transverse processes of the vertebrae. The contractor is connected to the distractor by a transverse traction with a thread, allowing both rods to be brought together, bringing the apex of the deformation closer to the midline of the body. In addition, the use of the Y. Cotrel modification allows the formation of a rigid rectangular frame structure, significantly increasing the degree of fixation of the achieved corrective effect,

Complications after scoliosis surgery

Fractures and displacements of the endocorrector. The frequency of this complication varies from 1.5 to 46%. The main causes of the complication are considered to be a lack of autobone when performing spondylodesis, age over 20 years, and a deformation value over 90°.

False joints. This concept, brought to vertebrology from classical traumatology, means the absence of a single continuous bone block in one or more places along the spondylodesis zone. The causes of this complication are varied: errors in surgical technique, small amount of autobone, general condition of the patient, etiology of spinal deformity. Analysis of literary material showed that the purity of this complication is 1.6%,

Neurological complications are the most severe complications. The frequency of their development when using the Harrington method is 0.7-1.2%.

Postoperative pain syndrome and flat back syndrome. The problem of the condition of the spinal segment located caudally to the lower hook of the distractor arose in the 80s, when patients who had been operated on 10-15 years ago reached adulthood. Many of them again turned to an orthopedist complaining of pain in the lower back. Clinical and radiological examination revealed a picture of lumbar osteochondrosis.

The use of the Harrington distractor in the scissor section can lead to another, very undesirable effect - the symptom complex of a flat back. It is a consequence of the installation of a caudal hook at the levels of L5 or S1 and consists of smoothing, up to the complete disappearance of the lumbar lordosis. Clinically, this is manifested by back pain and the inability to stand, since the patient's body leans forward.

Cast syndrome. The term was introduced into circulation in 1950 by Darph. It is the result of mechanical compression of the third portion of the duodenum by the trunk of the a. mesenterica superior. The term is not entirely accurate, since the development of the described symptom complex can be caused not only by corrective corsets, but also by distraction according to Harrington.

Normally, the third horizontal portion of the duodenum begins at the level of the L4 body, goes to the left and at the level of the L2 vertebral body it becomes the fourth part. The superior mesenteric artery departs from the aorta at an angle, the value of which is on average 41°. The horizontal portion of the duodenum passes between the aorta and the vertebral body from behind and a. mesenterka superior - from the front. Thus, conditions are created for compression of the duodenum in any situation when the angle of departure of a. mesenterica superior narrows, the duodenum shifts or the space between these formations narrows.

The main symptom is persistent nausea and vomiting in the early postoperative period, abdominal distension. Acute metabolic alkalosis may develop. Oliguria and rupture of the stomach wall are possible. X-ray contrast examination reveals dilation of the stomach and duodenum.

Treatment of scoliosis is conservative. Oral nutrition is stopped, a gastric tube and intravenous fluids are used. The patient's position is on the left side or on the stomach, sometimes this is enough to eliminate pathological symptoms. If symptoms increase, the corset should be removed, traction should be stopped, and glucocorticoids should be administered. If these measures are ineffective, duodenojejunostomy is indicated. The complication rate is 0.17%,

General surgical complications. Suppuration of the surgical wound develops in 1.1% of cases and does not always become a reason for removing endocorrectors. Timely established flow drainage allows to save the instrumentation and maintain the achieved correction.

[ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ]

Two-stage method of scoliosis correction according to Ya.L. Tsivyan

A significant loss of correction is observed after Harrington distraction almost always. Analysis of the situation led to the conclusion that such a loss of correction is quite natural. The Harrington distractor (most surgeons do not use a contractor) is fixed to the spine only at two points, with a posterior spondylodesis performed in the space between the hooks. The works of the school of Ya. L. Tsivyan convincingly showed that this operation on scoliosis is not able to resist the progression of spinal deformity. The etiology of idiopathic scoliosis still remains unknown, but it is obvious that the causes of the progression of the deformity continue to have an effect in the postoperative period. An increase in the scoliotic arc is primarily an increase in the torsion of the vertebral bodies. It is the progression of the torsional component of the deformity that is regarded as a loss of correction, although it would probably be more correct to talk about the progression of the pathological process under new conditions.

The need to interrupt this process was recognized by Ya.L. Tsivyan back in the early 60s, when he did not have such an effective tool as the Harrington instrumentation. In the mid-70s, Ya.L. Tsivyan developed a two-stage method of surgical treatment of scoliosis, which included distraction according to Harrington and anterior spondylodesis of the main arc of curvature. A later analysis of the results showed that anterior spondylodesis reduces postoperative loss of correction by more than three times.

Scoliosis: Luque Endocorrector Operation (2nd generation)

This endocorrector was created by the Mexican orthopedist Edwardo Luque in 1973. The method provides correction and rigid segmental fixation of the spine using two rods and sublaminar wire loops.

Technique of operation

The patient is positioned on his stomach, with the spine bent towards the convex side of the deformity (this achieves passive correction).

The posterior sections of the vertebrae are skeletonized throughout the entire deformation. The articular facets are removed on both sides, and the yellow ligaments are excised. The spinous processes are resected in the thoracic spine. The required length of spondylodesis is determined, and then the rods are prepared depending on the patient's dimensions. It is recommended to bend the rod to an angle 10° less than the deformation value on the spondylogram in the lateral tilt position. In the same way, the rod should repeat the shape of the kyphosis or lordosis. The normal values of these physiological curves should be preserved or restored if they were initially smoothed. Each rod should have an L-shaped bend at the end, with which it will be fixed to the base of the spinous process of the terminal vertebra through a transverse opening to prevent longitudinal displacement of the rod.

Wire loops are passed under the arches at all levels of the spondylodesis zone in the cranial direction. To reduce the depth of penetration of the loop into the spinal canal, the wire should be bent so that the bending radius is approximately equal to the sum of the width of the arch and both adjacent interarch spaces. When the loop appears in the upper interarch space, it is firmly grasped with an instrument and dissected. Two pieces of wire are obtained, one to the right and one to the left of the midline. The placement of the rod begins with the introduction of its end bend into the opening in the base of the spinous process. Then it is fixed to the half-arch of the same vertebra with the first wire. The second rod is fixed similarly on the other coine of the spondylodesis zone, on the opposite side. The rods are placed on the half-arches, each on the wire is tied above them and partially tightened. As the wire is tightened, the rods are pressed against the meadows, the deformation is gradually corrected. The rods are then tied together at several levels with additional transverse wire loops, and the sublaminar wire loops are tightened to the maximum. A dorsal spondylodesis is performed.

In 1989, the author of the method reported a significant improvement: hooks that are fixed on rods and take on compressive and tensile loads. The method does not require external immobilization, and the period of bed rest is only 1-2 weeks.

Complications after surgery

The introduction of multiple wire loops into the spinal canal increases the risk of neurological complications to 2.92%. Suppurations with the Luque method were noted in 3.27% of cases, pseudoarthrosis of the block - in 3.0%, and violation of the integrity of the system - in 6.8%.

Segmental correction using the bases of the spinous processes (J. Resina. A. Ferreira-Alves)

The first report on the correction of scoliotic deformities using the bases of the spinous processes as supporting structures dates back to 1977. The method was later refined and modified by Drumraond et al. The calculations of Druminond et a served as a serious justification for the method, showing that the thickness of the base of the spinous process exceeds the thickness of adjacent sections of the arch in the thoracic spine by 2.2 times, and in the lumbar spine by 1.7 times.

The technique of the Resina and Ferreira-Alves operation, modified by Drummond. The posterior sections of the vertebrae are exposed to the required extent similar to the manipulations in the Harrington operation. The hooks of the Harrington distractor are installed and the passage of wire loops through the bases of the spinous processes begins. Microarthrodesis of the true joints is performed beforehand. To implant the wire loops, transverse channels are first formed in the bases of the spinous processes using a special curved awl.

At the level of the upper and lower hooks, wire loops are passed only from the concave side to the convex side. At the other levels, two loops are passed so that one comes out on the concave side of the deformity, and the other on the convex side. Each wire loop is preliminarily passed through a round metal "button" that fits tightly on the lateral surface of the spinous process. In this case, the ends of each loop must pass through both "buttons". Then distraction is performed with the Harrington apparatus. A Luque rod is installed on the convex side. Wire loops are first tightened over the Luque rod, then over the Harrington rod. Both rods are additionally pulled together by transverse wire loops. Autografts are placed in the previously formed bone bed, the wound is sutured layer by layer. External immobilization is not used in most cases.

[ 6 ], [ 7 ], [ 8 ], [ 9 ], [ 10 ]

Cotrel Dubousset Toolkit (3rd generation)

The instrumentation was developed and first used in 1983 by French orthopedists Yves Cotrel and Jean Duboussel. The instrumentation contains the following elements:

Rods of uniform diameter, without weak points and capable of bending at any point without loss of mechanical strength, to which hooks can be fixed at any point;

Hooks for various purposes (laminar, pedicular, transverse), providing corrective force in the required direction,
Devices for transverse traction, connecting two rods and a rigid frame structure.

The basis of the theoretical concept of Cotrel-Duboussel Instrumentation (CDI) is as follows: scoliosis is a three-dimensional deformation of the spine, therefore, its correction must be carried out in three planes.

Technique of using CD HORIZON in a typical case of thoracic lordoscoliosis with lumbar counter-curvature

Principles of preoperative planning

The goal of surgical treatment of adolescent idiopathic scoliosis is to prevent progression in combination with safe and optimal correction in the frontal and sagittal planes and axial derotation. At the same time, it is necessary to preserve the maximum number of free motion segments above and below the spondylodesis zone.

Upper border of the spondylodesis zone

The most common type of scoliotic thoracic arc is a single thoracic arc with an upper thoracic countercurve. In such deformities, the cranial end vertebra becomes the upper boundary of the spondylodesis zone. The mobility of the upper thoracic spine is determined in the position of lateral tilt towards the convexity of the upper thoracic countercurve - the Cobb angle between the caudal end plate of the upper vertebra of the arc and the cranial end plate Th1 is measured. Then, the mobility of the cranial part of the primary arc of curvature is examined - on a spondylogram in the position of lateral tilt towards its convexity. Here, the angle formed by the caudal end plate of the apical vertebra and the cranial end plate of the upper end vertebra of the primary arc is measured. To maintain the balance of the shoulders after surgery, the difference between the two above-mentioned angles should not exceed 17°. When determining the cranial border of the spondylodesis zone, it is necessary to carefully examine the profile spondylogram - the upper hooks of the structure should not be located at this level or 1-2 segments and distal.

Lower border of the spondylodesis zone

Determining this boundary is one of the most difficult tasks in scoliosis surgery. The need to preserve the maximum possible number of free motion segments in the lower lumbar spine is dictated by two circumstances.

The shorter the block zone, the easier it is for the patient to adapt to new static and dynamic conditions in the postoperative period.

The shorter the block-free zone, the greater the likelihood of early degenerative changes developing in overloaded lumbar intervertebral discs.

The most cranial of the remaining free segments must be balanced in three planes. To balance in the frontal plane, the most cranial disc of those located caudally to the block must symmetrically "open" to the right and left.

For sagittal plane equilibration, the cranial disc from those located under the block area must be included in the correct gentle
sagittal curvature of the spine in the standing position. In addition, the disc must be equilibrated in flexion and extension compared to the standing position at rest

For this disk to be balanced in the horizontal plane, it must theoretically be free of any residual permanent torsional loads.

To determine the extent of the instrumental spondylodesis zone, several classifications of idiopathic scoliosis have been created, the most complete of which was developed by Lenke el al.

According to the classification of Lenke et al., six types of deformation are distinguished, and two modifiers are introduced to characterize the lumbar arch and the sagittal profile of the thoracic spine. The lumbar modifier is designated as A, B, or C, and the thoracic modifier as (-), N, or (+).

The type of deformation (from I to VI) is determined in accordance with the recommendations of the Scoliosis Research Society.

• Thoracic scoliosis (apex between body Th2 and disc Th11-12) includes proximal, or upper thoracic (apex at the level of Th3, Th4, Th5), and primary (apex between body Th6 and disc Th11-12).
• The apex of the thoracolumbar scoliosis is located between the cranial endplate of Th2 and the caudal endplate of L1.
• Lumbar scoliosis has its apex between the LI-2 disc and the caudal endplate of the L4 body.

A scoliotic arc is considered structural when normal mobility is lost and, depending on the value of the Cobb angle, is called major or minor. The secondary arc can be either structural or non-structural. For ease of use, the classification was introduced with specific characteristics of structural arcs.

• Structural upper thoracic curvature in the lateral tilt position has a Cobb angle of at least 25° and/or a kyphosis of at least 20° along the length from Th1 to Th5.
• The primary thoracic structural curve also maintains a minimum of 25° Cobb angle in lateral tilt and/or a thoracolumbar kyphosis of at least 20° at the Th10-L2 level.
• The structural lumbar (thoracolumbar) arch is characterized by the same mobility parameters in the lateral tilt position and/or the presence of kyphosis of at least 20° at the Tр10-L2 level.

Any secondary arch is considered structural if it has the listed characteristics. Lenke et al. suggest that when planning an operation, only primary and structural secondary arches should be included in the block area. The following six types of deformations are distinguished:

• Type I deformity; the main thoracic curve is structural, and the upper thoracic or lumbar (thoracolumbar) countercurves are nonstructural.
• Type II deformity: two thoracic structural curves, and the lumbar (thoracolumbar) countercurvature is non-structural.
• Deformity type III: two structural curves - primary thoracic and lumbar (thoracolumbar), upper thoracic countercurvature - non-structural. The thoracic curve is greater than, equal to or less than the lumbar (thoracolumbar) curve by no more than 5°.
• Deformity type IV: three structural arches - two thoracic and lumbar (thoracolumbar), with any of the latter two being primary.
• Type V deformities: structural lumbar (thoracolumbar), more proximally located arches - non-structural.
• Deformity type VI: the main lumbar curve (thoracolumbar) is at least 5° greater than the thoracic curve, and both structural curves are

Proximal upper thoracic countercurve is nonstructural.

If the difference between the thoracic and lumbar curves is less than 5°, scoliosis is classified as type III, IV or V based on structural characteristics. It is always necessary to distinguish between types III (primary curve is thoracic) and VI (primary curve is lumbar or thoracolumbar). If the magnitude of these two curves is equal, the thoracic curve is considered primary.

Using the Lumbar Modifier (A, B, C)

When planning surgery, it is necessary to evaluate the lumbar curvature, as it affects both the spinal balance and the proximally located curves. Depending on the relationship of the central sacral line (CSL) to the lumbar curve on a direct spondylogram, Lenke et al. identified three types of lumbar scoliotic deformities.

The CCL divides the cranial surface of the sacrum strictly in half and is perpendicular to the horizontal.

The CCL continues in a cranial direction, and the lumbar or lower thoracic vertebra that is most accurately divided in half by this line is considered stable.

If the intervertebral disc is divided into two equal parts, the vertebra located caudal to this disc is considered stable.

The apex of the lumbar (thoracolumbar) arch is considered to be the vertebra or disc that is located most horizontally and most displaced laterally.

Depending on the relationship of the CCL to the lumbar arch, different modifiers are used.

Modifier A is used when the CCL passes between the roots of the lumbar vertebral arches to the level of the stable vertebra. Such scoliosis should have an apex at the level of the Th11-12 disc or more cranial, i.e. modifier A is used only for thoracic scoliosis (I-IV types), but not for lumbar and thoracolumbar (V-VI types). Likewise, it is not used when the CCL passes through the medial edge of the root shadow of the apical vertebral arch.

Modifier B is used when, due to deviation of the lumbar spine from the midline, the CCL touches the apex of the lumbar arch between the medial edge of the shadow of the root of the arch of the apical vertebra and the lateral edge of its body (or bodies, if the apex is at the level of the disk). Such scoliosis, as in the case of modifier A, is classified as types II-V.

Modifier C is used when the CCL lies completely medial to the lateral surface of the apical vertebral body of the lumbar (thoracolumbar) curve. Such scoliosis may have a primary curve of thoracic, lumbar or thoracolumbar localization. Modifier C can be used for any thoracic scoliosis (types II-V) and must be used for types V and VI (lumbar and thoracolumbar scoliosis).

Sagittal thoracic modifiers (-, N, +)

The sagittal contour of the thoracic spine must be taken into account when planning surgical intervention. The type of modifier is determined by measuring the sagittal contour of Th5-Thl2 with the patient standing. If there is a kyphosis of less than 10° (hypokyphosis), the modifier (-) is used, from 10 to 40° the modifier N, with a deformation of more than 40° (hyperkyphosis) - the modifier (+).

Thus, by classifying scoliotic deformation into one of six types and determining the lumbar and thoracic modifiers necessary in this case, it is possible to classify scoliosis in a compressed form, for example IA-, IAN, 6CN, etc.

The structural characteristics of the deformation in the sagittal plane play an important role in the system of Lenke et al., since they determine the extent of the spondylodesis zone, the hyperkyphosis of the upper thoracic and thoracolumbar regions, and the rigidity demonstrated in the lateral tilt position - important characteristics of the so-called secondary deformations. The extent of the thoracic spine spondylodesis in deformities of types I-IV depends on the increase in kyphosis in the upper thoracic or thoracolumbar regions. In types V and VI scoliosis, the brick arc is lumbar (thoracolumbar), the thoracic countercurvature in type V is non-structural, and in type VI - structural.

Lumbar modifier A indicates that there is minimal or no lumbar curve, while modifier B indicates that there is a mild to moderate lumbar curve.

Lenke et al. suggest that in the presence of A or B modifiers, the lumbar curve should not be blocked unless there is more than 20° of kyphosis in the thoracolumbar spine. In patients with type 1C or 2C deformities, selective thoracic fusion may be performed, the length of which allows maintaining the balance of the lumbar spine.

Selective thoracic spondylodesis for type I deformities with any lumbar modifier using segmental instrumentation often leads to the development of trunk imbalance. However, this operation on scoliosis is possible if the following conditions are met: the lumbar arch in the lateral tilt position is less than 25°, there is no kyphosis in the thoracolumbar region, the thoracic spine is rotated more than the lumbar spine.

Deformations of type IIA (with any thoracic modifiers) include, in addition to the main thoracic curve, structural upper thoracic and non-structural lumbar (thoracolumbar) counter-curves. Any structural thoracic or lumbar curve may have a structural upper thoracic counter-curve. Structural upper thoracic curves in type IV scoliosis have the same characteristics. Identification of type IIC allows us to consider the upper thoracic and lumbar components of the deformation separately.

Deformations of types IIIA and IIIB (with any thoracic modifiers) are relatively rare and contain two primary curves - thoracic and lumbar (thoracolumbar). The lumbar component of such a deformation is always structural in the frontal and sagittal planes, even if the curve deviates slightly from the midline. In scoliosis of the type SS, such a deviation is always significant, so both curves should be included in the block.

Triple scoliosis types IVA and IVB (with any thoracic modifiers) contain three structural arcs: upper thoracic, thoracic and lumbar (thoracolumbar), with the last two being larger than the first. The lumbar arc does not shift completely from the midline, but if the thoracic arc is expressed roughly, the lumbar curvature has signs of structurality. With deformities of type IVC, the deviation of the lumbar arc from the midline is significant, as one would expect.

Lumbar (thoracolumbar) scoliosis is classified as type VC if it has a non-structural thoracic counter-curve, and as type VIC if the thoracic counter-arc has structural features. In any case, only structural curvatures are subject to blocking.

Technique of surgical intervention

Preparation and positioning of the patient

To facilitate manipulations during the intervention, it is advisable to use traction. In fact, it helps to stabilize the spine, and also to "weaken" it somewhat due to its own elasticity. In addition, traction facilitates the installation of hooks and rods. Traction should not exceed 25% of the patient's body weight. When placing in the surgical position, the abdominal wall should be completely freed to avoid compression of the inferior vena cava.

The skin incision is linear median. Preparation of the posterior vertebrae includes careful removal of soft tissues throughout the future area of the spinous process, semi-arches, articular and transverse processes.

Hook installations

Lower limit of the design. Experience shows that when forming the caudal part of the design, in all possible cases it is desirable to use a configuration called reverse (reverse) capture. This option provides several advantages: reliable fixation, provision of lordosis affect during rotation of the rod, cosmetic effect, expressed in the normalization of the shape of the waist triangles.

When forming a reverse capture, only laminar hooks of various types are used. First, two hooks are implanted on the side of the corrective rod (for right-sided scoliosis - on the left). The installation of an infralaminar hook on the end vertebra is quite simple. The yellow ligament is separated from the arch with a sharp thin scalpel to expose its lower edge. In some cases, especially in the lower lumbar spine, the semi-arch is located very vertically, which increases the risk of the hook slipping. In these situations, it is better to use an oblique laminar hook. The shape of its tongue better corresponds to the anatomy of the arch.

The second hook (supralaminar) is installed one or two segments cranially. The installation of a supralaminar hook (usually a hook with a wide tongue) is technically not much different from the infralaminar hook.

On the opposite side of the lower end of the structure, two hooks of opposite orientation are used in the reverse grip - supra- and infralaminar. This makes it possible to more effectively normalize the position and shape of the most caudal of the intervertebral discs included in the spondylodesis zone. The supralaminar hook on the right half of the reverse grip, due to the torsion of the lumbar vertebrae, often ends up standing very deep, which subsequently complicates the introduction of the lower end of the rod into its lumen. In this regard, it is recommended to use a hook with an elongated body.

Apical and intermediate hooks

The vertebrae on which these hooks are installed are strategic along with the terminal ones. The usual sequence of hook implantation involves the initial formation of a reverse causal grip, and then the part of the structure that plays a decisive role in the course of the derotating maneuver, the so-called intermediate intestines located between the apical and terminal vertebrae. A spondylogram performed before the operation and the position of the tilt of the main ray and the side of its convexity shows, among other things, the least mobile vertebral segments in the region of the apex of the arch. These segments become the place of implantation of the intermediate hooks, which work in the distraction mode and therefore are multidirectional. The lower of these hooks is supralaminar, the upper one is pedicular. The installation of a supralaminar hook in the thoracic spine requires great care and, since it can occupy quite a large space, its installation is performed without any force. In some cases, it is advisable to use a hook with an offset body as a lower intermediate hook, which makes it easier to subsequently insert a curved rod into its lumen.

The upper intermediate hook of the concave side and the apical hook cited by them on the convex side are the apex of the deformation - pedicular. When installing a pedicular hook, it is necessary to remove the caudal part of the lower articular process of the corresponding vertebra.

The line of the inferior margin of the semi-arch curves quite noticeably, showing the internal hook of the articular process. With an osteotome, a longitudinal section is first made along the medial margin of the inferior articular process, then a second section is made parallel to the transverse axis of the vertebral body. This section must be complete, otherwise the hook may migrate and take an infralaminar position.

A special instrument is used to widen the entrance to the joint, while the surgeon ensures that the instrument is in the joint cavity and does not dissect the remainder of the resected articular process. A pedicle finder is used to localize the root of the arch by inserting it into the joint without excessive force. Then the hook is inserted using a gripper and a pusher. For insertion, the hook is held in a slightly inclined position relative to the articular process. With a slight flexion movement of the wrist, the hook is inserted into the joint cavity, which is more or less parallel to the general inclination of the vertebral body. This manipulation is performed without force. A correctly installed hook "sits on top" of the dorsal part of the root of the arch and cuts into it.

[ 11 ], [ 12 ], [ 13 ], [ 14 ]

Upper limit of the design

To achieve maximum stability, it is advisable to complete the structure with bilateral upper grips. Up to the Th4 level, a pedicular-transverse grip is used on one vertebra. More cranial than Th4, a pedicular-laminar grip is recommended, formed not on one, but on two adjacent vertebrae. Resection of the facet joints and spondylodesis are mandatory. To reduce blood loss, it is advisable to split this manipulation into two stages and precede each of them with implantation of the next rod.

Bending of rods

The technique of this most important manipulation depends on the shape of the spine that needs to be achieved as a result of the intervention. The main part of the operation is a derotation maneuver designed to ensure harmonious correction when the correcting force acts on the entire instrumentation zone at one time. The purpose of the manipulation is to restore the balance of the spine. When bending the rod, its axis should be constantly monitored so that the bend occurs only in the required plane. Technically, the contouring of the rod is carried out using the so-called French bender.

[ 15 ], [ 16 ]

Installing the rod on the concave side of the arch

This rod is inserted first to correct the thoracic curve by automatic distraction that occurs during rod rotation and to restore thoracic kyphosis. In the lumbar region, acting on the same principle, the rod restores lumbar lordosis. The introduction of the rod is facilitated by the presence of open hooks. The correction of the spine begins with longitudinal traction during the operation, then a curved rod is implanted on the concave side and a derotation maneuver is performed.

The standard procedure for inserting the rod begins at the upper thoracic level. First, the rod enters the slot of the pedicle hook, then the corresponding transverse hook from the common grip. The locking sleeve is screwed into the transverse and pedicle hooks with the free hand using the sleeve grip. The sleeves are slightly tightened to fix the hooks of the upper grip on the rod. Then the rod is inserted into the most distal hooks. This manipulation (insertion of the rod into the intermediate hooks) is the first stage of deformity correction.

The rotation of the rod is carried out with special grips - slowly and gradually, so that the viscoelastic properties of the spine contribute to the reduction of deformation. It is always necessary to remember that the pedicular hook can potentially shift into the spinal canal and turn into a sublaminar hook, and the lowest
sublaminar hook can shift dorsally during the rotation of the rod. Particular attention should be paid to the position of the intermediate hooks, since during derotation they are subject to a particularly pronounced effect, which can actually lead to damage to bone structures and displacement of the implants. At the end of the rotation, all bushings are tightened. In fact, derotation using the first rod is the main corrective manipulation.

Installing a rod on the convex side of the arch. The role of this rod is to increase the stability of the system and maintain the achieved correction. There are no special differences from installing the first rod.

Installation of devices for transverse traction (Device for Transverse Traction - DTT). These devices are installed between the rods in the direction of distraction at the upper and lower ends of the structure, and if the length of the structure is more than 30 cm, additionally in its middle part.

Final tensioning and cutting of bushing heads. During cutting of bushing heads, hooks are fixed with a special device (counter torque), which eliminates the impact of torsional force on hooks and underlying bone structures.

Bone spondylodesis

All accessible bone surfaces of the planned spondylodesis zone should be decorticated and included in the block. Instead of removing the articular processes, it is advisable to decorticate them to increase the area of the bone bed. Experience shows that an economical attitude to local autogenous bone with the preservation of its smallest fragments when forming the bed of hooks and decortication allows you to form a bank sufficient for performing spondylodesis in a patient. Muscles and fascia are sutured with interrupted sutures, a tubular drainage is installed under the muscles for 48 hours

[ 17 ], [ 18 ], [ 19 ]

Postoperative management

The patient is raised and allowed to walk early - on the 3rd day. The patient must learn to control his new state in front of a mirror in order to develop new proprioceptive mechanisms. It was noted that after the operation almost all patients experience a feeling of curvature. Therefore, they have a desire to return to their pre-operative state. Using a mirror in this regard is very useful for adapting to the new state.