RU2620355C1 - Method for installation of screws for spine transpedicular stabilization - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: preoperative planning is performed based on computer tomography. Based on the computer tomography performed, a markup map is created by creating a multiplanar reconstruction, on its basis an image is formed, where the trajectories of screws insertion, the distance between the points of screws insertion, the distance between the supraspinal ligament and the point on the screw trajectory at the same level are marked. On the formed markup map, the insertion points are determined intraoperatively, the deflection angle in the sagittal plane is determined from the side x-ray image and controlled by fixing the direction by installation of an additional spoke, and the deflection angle in the axial plane is determined indirectly, based on the distance from the apex of the spinous process - the supraspinal ligament determined on the markup map, the deflection angle in the axial plane is controlled by the distance to the apex of the spinous process - the supraspinal ligament, using a marking compass with a ruler, or a caliper.

EFFECT: method allows to reduce the radiation load, ensure the accuracy of the screw introduction.

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Description

The invention relates to medicine, namely to traumatology, orthopedics, neurosurgery, and can be used to conduct transpedicular fixation of the vertebrae in an open way in the surgical treatment of injuries, diseases and deformations of the spine.

The method includes preoperative planning of the trajectory of the introduction of transpedicular screws based on computed tomography of the spine and the installation of screws along planned trajectories. For planning, any program can be used to view medical images in the DICOM format, capable of building multi-planar reconstruction (MPR) in an arbitrary plane (there are many such programs in open sources, including free and shareware, for example: "Onis 2.4 Free Edition "," Inobitec DICOM Viewer "," E-Film ", etc.). On a multiplanar reconstruction in the plane of screw insertion, the most optimal paths of passage (through the arc legs into the vertebral bodies) for each screw are selected. A markup map is formed for each vertebra, including slices in three planes and display on the screw insertion plane of their entry paths, the distance between the screw insertion points, the distance between the supraspinatus ligament and the point on the screw path at the same level. Intraoperatively, screw insertion points are determined based on the created markup map, the angle of entry in the sagittal plane is determined by x-ray in the lateral projection, the angle of convergence in the axial plane is determined indirectly by measuring the distance between the apex of the spinous process (supraspinatus ligament) and the tool used to install the screw. The technique allows for accurate insertion of transpedicular screws, does not require the use of expensive navigation systems, allows X-ray control only in the lateral projection, which reduces the radiation load on the patient and staff and makes it possible to use a conventional (non-X-ray transparent) operating table.

Transpedicular stabilization of the spine has been used since the 70s of the last century (Roy-Camille R et al., 1976) and has now become the "gold standard" in the treatment of traumatic injuries of the spine, primary and metastatic spinal tumors, scoliotic disease, hematogenous osteomyelitis, tuberculosis spondylitis, degenerative lesions, etc. Despite the variety of existing transpedicular systems of various manufacturers, the technique of direct insertion of screws in an open way is similar. An opening is made in the cortical layer at the intended insertion point, then a pin channel in the cancellous bone is created with the instrument, the walls of which are evaluated by the button probe. A screw is inserted through the formed pin channel. In this case, the screw should not go beyond the boundaries of the cortical bone layer, which guarantees the safety of adjacent nerve and vascular formations. The key points for the correct location of the screw inside the vertebra is the choice of insertion points and deviation angles of the screw insertion path in the axial and sagittal planes.

The first known methods of installing transpedicular screws implied identifying “typical” insertion points using anatomical landmarks. Many methods have been proposed for determining such points. The earliest description was provided by R. Roy-Camille, indicating it as located 1 mm from the lateral edge of the arched joint, caudal to its lower edge by 1 mm. Weinstein also proposed the use of an accessory processus (processus accessorius) as a guideline in the lumbar spine. The most popular is the more laterally located point of injection according to F.P. Magerl, located along the midline of the transverse process at the level of the lateral edge of the superior articular process of the corresponding vertebra. The deviation angles in the sagittal and axial planes were determined for each vertebra using special tables (Zindrick, M.R. et al., 1987). However, significant anatomy variability, especially in pathological conditions, leads to errors. So, in the given example (Fig. 1 and Fig. 2) L4 vertebra is shown in two patients. In the first case (Fig. 1), the injection point and the deviation angles correspond to the “typical” ones, and in the second case (Fig. 2), either a significant increase in the convergence angle in the axial plane (Fig. 2C) or a change in the screw insertion points are required (Fig. .2d).

To increase the accuracy of screw installation, intraoperative fluoroscopy is used. The points of insertion of the screws and their installation are controlled by the sequential implementation of x-rays in the front and side projections. At the same time, the location of the screws in the sagittal plane is controlled directly on the side image, and indirectly in the axial projection. For this, several pictures are taken in a direct and lateral projection as the instrument passes the vertebral leg, which increases the radiation load on the patient and the operating team. In addition, repeated turns of the X-ray unit around the patient significantly increase the risk of sterility disorders and, accordingly, the risk of infectious complications. Also a prerequisite is the presence of an X-ray transparent operating table for taking a picture in direct projection.

Modern x-ray systems, such as O-arm or intraoperative computed tomography, make it possible to obtain images directly in axial projection. Also, navigation systems have been developed and are used to significantly increase the accuracy of screw installation. A significant drawback of these methods is the high price, which limits their widespread use.

For this reason, alternative methods and techniques continue to be published for determining screw insertion points and axial deflection angles.

So, there is a method of introducing screws for transpedicular fixation of the vertebrae (Patent RU 2187978), according to which the patient is subjected to x-ray of the spine lying in two projections before surgery, according to which preoperative planning is performed. The points and directions of the introduction of transpedicular screws are determined. Radiographs are plotted indicating the angles of insertion of the screws in two planes. Intraoperatively, control spokes are introduced into the target points into the vertebral bodies through the arches, the direction of the channel in two planes is checked using an angle meter. A control x-ray is carried out in two planes, if necessary, a correction of the position of the spokes. An awl is introduced along the spoke, a channel is formed for introducing the screw. Screws are screwed into the channels formed in this way for transpedicular fixation of the spine.

The disadvantage of this method is the already indicated need for x-ray control in 2 projections, as well as the assessment of the angle of convergence of the goniometer. The use of the goniometer is complicated by the fact that quite often, due to pathological changes, it is difficult to determine the middle line from which the deviation angle is counted. So, the figure (Fig. 3) shows examples when the sagittal plane of the vertebra does not correspond to the sagittal plane of the body, sometimes up to tens of degrees.

Also known is a method for determining the direction of insertion of transpedicular screws in pediculocorporeal osteosynthesis of lower thoracic and lumbar vertebrae (Patent RU 2204341). The method consists in determining the "surplus processes" of the vertebrae and, based on the average deviation angles and the minimum transverse dimensions of the legs of the vertebral arches, transpedicular screws are inserted through the surplus processes.

The disadvantage of this method is the detection of "incremental processes", which are not always determined even with normal anatomy, and even more so with pathology. In addition, the use of average angles and distances limits the application of the technique in the same way as with the classical method.

Known devices for introducing transpedicular screws. For example, a device for inserting screws for transpedicular fixation of the vertebrae (Patent for utility model 84212), a device for holding threaded screws for transpedicular fixation of the vertebrae (Patent for utility model 92611). Device for holding transpedicular screws (Patent for utility model 107035). A device for conducting spoke-guides in vertebroplasty and transpedicular osteosynthesis (Utility Model Patent No .: 107039). Navigator for transpedicular fixation (Utility Model Patent No .: 137191). Guide for holding screws for transpedicular fixation of the spine (Utility Model Patent No: 142584). All of these devices are used to maintain the specified angles of the direction of insertion of the screws, which are calculated before the operation on the basis of x-ray research methods (computed tomography). A significant drawback of these devices is the need for their reliable fixation on the spinous process, which can be difficult to perform due to the small thickness of the process or its inclined location.

According to the technical nature, the closest way to the proposed one is to determine the direction of insertion of transpedicular screws in patients with overweight (Patent RU 2321349, 2007), according to which, based on computed tomography, the deviation angle of the insertion path in the axial plane for each screw is determined.

The disadvantages of this method are the lack of a clear indication of the need for calculations based on multiplanar reconstruction, since the plane of the introduction of screws, in most cases, does not coincide with the axial plane of the body. Also, the method for determining the screw insertion points is not decrypted. The disadvantage of using a protractor, as mentioned above, is that quite often due to pathological changes, it is difficult to determine the middle line, from which it is assumed to count the angle of deviation in the axial plane.

The technical result of the proposed method of installing screws for transpedicular stabilization of the spine is the exact introduction of the planned path, the absence of the need to use additional devices and expensive navigation systems in the operating room, the ability to perform intraoperative x-ray control only in the lateral projection, which reduces radiation exposure to staff and does not require X-ray transparent operating table.

The specified technical result is achieved by the fact that on the basis of computed tomography a marking map is created, by creating a multiplanar reconstruction in the plane of screw insertion and on its basis an image is formed on which the paths of screw insertion, the distance between the points of screw insertion, the distance between the supraspinatus and the point on the trajectory of the screw at the same level, according to the formed markup map intraoperatively, the points of insertion of the screws are determined individually, the angle of deviation in the sag the ottal plane is determined by the lateral x-ray, and the angle of deviation in the axial plane is determined indirectly, based on the distance from the apex of the spinous process defined on the markup map.

Method description

The proposed method is as follows.

The patient undergoes computed tomography of the intended area of operation with a slice thickness of 1 mm. The result is recorded in DICOM format (the main format for transmitting medical images). To create a markup map, programs are used to view the DICOM format with the ability to build multi-planar reconstructions and take measurements. Such programs include - "Inobitec DICOM Viewer", "E-Film", "Onis", "RadiAnt" and others.

Multiplanar reconstruction is performed in the plane of the proposed screw insertion, which passes through the middle (or the widest part) of the arc legs into the vertebral body (Fig. 4A and B).

Then, using the program tools, draw lines of the screw insertion path and note the screw lengths (segments ac and bd), the distance between the screw insertion points (cd), the distance from the apex of the spinous process to the point on the trajectory at this level (ef and gf). Images are formed in the sagittal and frontal projections, with the introduction plane of the screws displayed on them, while projections along the midline and through both legs of the vertebra are formed in the sagittal plane. Images are also formed parallel to the installation plane above and below with an interval of 2 mm (Fig. 5), and marker lines (projection of the insertion points onto anatomical landmarks) are drawn through the screw insertion points. The resulting images are printed (if there is no image upload function in the program, a screenshot is taken [PrintScreen], the received images can be edited and combined into a single card in any graphics editor). A fully formed markup map for one level is shown in Fig. 6.

During the operation, with the patient's position on the abdomen, a typical posterior access is made through a longitudinal section along the spinous processes. After dissection of the subcutaneous tissue, own fascia, the spinous processes, arched joints and vertebral arches skeletonize. Regardless of the pathology, the first step is the installation of screws (on unchanged anatomy). On the basis of the marking map, the points of insertion of the screws are determined (by the relationship to the surrounding bone structures, including above and below the points of insertion). An additional accuracy factor is the measurement of the distance between the points of introduction. The needles are installed at the selected points, the angle of deviation in the sagittal plane is controlled by a lateral x-ray. The direction is fixed by installing an additional spoke (usually in the spinous process).

A tool is introduced to form the pin channel, while the deflection angle in the sagittal plane is controlled by the installed additional needle, and the deflection angle in the axial plane is controlled by the distance to the apex of the spinous process (supraspinatus), for which a marking compass with a ruler or a caliper is used (Fig. . 7). After evaluating the channel walls, a screw is screwed in with a probe. When installing the screw, the angles in the axial plane along the distance to the apex of the spinous process (supraspinatus ligament) and in the sagittal plane along the installed additional spoke are also controlled.

Clinical example 1.

Patient Sh., 61 years old.

Upon receipt of a complaint: back pain, aggravated by a change in body position, increased fatigue and sweating, weakness in the legs, difficulty walking. Case history: From the beginning of the year, I began to notice a general weakness. During the same time, pain in the thoracic spine was disturbing. He was treated at the place of residence by a neurologist. Non-steroidal anti-inflammatory drugs were prescribed, which gave insufficient analgesic effect. Since August, notes an increase in general weakness, the appearance of sweating with slight physical exertion, increased pain. On the day of hospitalization, the patient noted urinary retention and weakness in the legs.

General condition upon receipt of moderate severity. Forced situation. Somatically stable. In neurological status, lower paraparesis up to 3 points with the revival of deep reflexes, pathological expansion of reflexogenic zones and pathological stop signs on both sides. Urinary retention is noted. Pain on palpation in the thoracic spine is noted.

On a CT scan of the organs of the thoracic, abdominal cavities and pelvis, the CT picture corresponds to destructive spondylitis in the Th11-Th12 segment with paravertebral infiltration at this level.

On MRI of the thoracolumbar spine there are signs of spondylodiscitis at the level of Th11-12, with narrowing of the spinal canal and reactive changes in paravertebral tissues and involvement of the intracanal ligamentous apparatus. Compression fracture Th12.

Diagnosed with suppurative spondylodiscitis Th11-12, epidural abscess at the level of Th10-12. Lower paraparesis. Violation of the function of the pelvic organs as a delay.

Based on the CT scan performed according to the indicated technique, markup maps for the Th10 and L1 vertebra are formed.

According to emergency indications, the operation was performed: Extra-focal transpedicular metal osteosynthesis of Th10-L1 by a non-magnetic system. Decompression laminectomy Th11, partially Th10 and 12. Removal of epidural abscess. Diskectomy Th11-12 with resection of the adjacent parts of the vertebral bodies. Drainage of the Th11-12 disc cavity and epidural space.

During the operation, screws were initially installed, and only after that a laminectomy was performed (preservation of the anatomical landmarks for installing screws). On the marking maps, points of screw insertion for each vertebra were found, in relation to the surrounding anatomical structures. The correct choice of points was controlled by measuring the distance between them. Knitting needles were installed at the found points, their deflection angle in the sagittal plane was checked by the side x-ray, the found path was marked by installing an additional spoke, then sequentially to the right and left, controlling the deflection angle in the sagittal plane using the installed additional needle, and the deflection angle in the axial plane was measured the distance to the apex of the spinous process, a tool was introduced to form the pin channel. One of the signs of the correct installation was the determination of the anterior cortical layer at the calculated depth. After the formation of the channel, the walls were evaluated using a button probe. Further, by controlling the deflection angle in the sagittal and axial planes, a screw of the calculated length was introduced. After installing all the screws, the main stage of the operation was performed - laminectomy, removal of the epidural abscess, discectomy.

In the postoperative period, the patient received massive antibacterial therapy, adjusted according to the results of intraoperative cultures (St. Aureus growth was obtained). Against the background of the treatment, almost complete regression of neurological deficit was noted (restoration of movements in n / a and control over the function of the pelvic organs), relief of pain, relief of the phenomena of a systemic inflammatory reaction.

On the control computed tomography of the thoracic spine - the screws are installed correctly, do not go beyond the boundaries of the cortical layer.

Clinical example 2.

Patient B., 20 years old.

Upon receipt of a complaint: Pain in the lumbar spine with radiation to the right leg. Case history: Over the past 2 years, pain in the lumbar spine has been troubling. Later, pain began to radiate to the right buttock. Treated conservatively, without significant improvement. Examination revealed spondylolysis leafesis L5. Received for surgical treatment. Objective status: satisfactory condition. Forced situation. Regular food. The skin is of normal color, dry. Somatically stable.

In the neurological status, a decreased Achilles reflex to the right was noted, a slight hypesthesia along S1 to the right. The forced position in the lumbar spine, tension of the paravertebral muscles, movements in the lumbar spine are painful, limited, smoothness of the lumbar lordosis. A positive symptom of Lassega on the right is up to 45 °.

On MRI - a picture of the spinal fusion of L5 vertebral vertebral l5 (2 tbsp.) L5-S1 intervertebral disc herniation with compression of nerve structures.

Diagnosed with Spondylolysis spondylolisthesis of L5 vertebra (2 tbsp.). Intervertebral hernia L5-S1. Pain vertebrogenic and radicular syndrome.

A CT scan of the lumbosacral spine was performed, bilateral L5 spodilolysis was confirmed. According to this technique, markup maps for the L5 and S1 vertebra are formed.

Operation performed: Laminectomy L5. Diskectomy and disc herniation L5-S1. Leaf reduction L5. Interbody fusion with a non-magnetic cage filled with an osteoconductive drug and transpedicular fixation in L5 and S1 bodies by a non-magnetic system. (Anesthesia: Combined endotracheal anesthesia.)

During the operation, screws were initially installed, and only after that a laminectomy was performed (preservation of the anatomical landmarks for installing screws). On the marking maps, points of screw insertion for each vertebra were found, in relation to the surrounding anatomical structures. The correct choice of points was controlled by measuring the distance between them. Knitting needles were installed at the found points, their deflection angle in the sagittal plane was checked by the side x-ray, the found path was marked by installing an additional spoke, then sequentially to the right and left, controlling the deflection angle in the sagittal plane using the installed additional needle, and the deflection angle in the axial plane was measured the distance to the apex of the spinous process, a tool was introduced to form the pin channel. One of the signs of the correct installation was the determination of the anterior cortical layer at the calculated depth. After the formation of the channel, the walls were evaluated using a button probe. Further, also controlling the deflection angle in the sagittal and axial planes, a screw of the calculated length was introduced. After installing all the screws, the main stage of the operation was carried out - laminectomy, discectomy, reduction of leafesis, installation of a cage.

The postoperative period without complications. The wound healed first. The seams are removed. Pain radicular syndrome regressed. In neurological status, moderate positive dynamics.

On the control CT scan of the lumbar spine, the position of the implants and the fixation system is correct, the screws do not extend beyond the borders of the cortical layer, the leaf is removed.

In total, using this technique since 2010, more than 250 operations were performed. The correct installation of the screws was monitored on a postoperative CT scan. In this case, the accuracy was evaluated on a scale based on the measurement of a fragment of a screw extending beyond the cortical layer, divided into 2 mm intervals (Gertzbein SD, 1990). The overall accuracy was more than 97%, which according to the literature (Aoude AA et al., 2015) corresponds to the accuracy achieved with the use of navigation systems.

Thus, the use of the proposed method allows to achieve high accuracy of installation (comparable to navigation equipment), does not require expensive or rare equipment, allows you to perform radiography only in the lateral projection, which reduces radiation exposure to the patient and staff and allows you to perform operations on a normal (not radiolucent ) table.

List of references

1. Aoude AA, Fortin M, Figueiredo R, Jarzem P, Ouellet J, Weber MH. Methods to determine pedicle screw placement accuracy in spine surgery: a systematic review. Eur Spine J. 2015 May; 24 (5): 990-1004.

2. Gertzbein SD, Robbins SE. Accuracy of pedicular screw placement in vivo. Spine, 1990; 15: 11-4.

3. Roy-Camille R., Saillant G., Berteaux D., Salgado V. Osteosyndrosynthesis of thoraco-lumbar spine fractures with vertebral pedicles. Reconstr. Surg, and Traum., 1976: 15 P. 2-17.

4. Zindrick, M.R. et al. Analysis of the morphometric characteristics of the thoracic and lumbar pedicles. Spine, 1987; 12: 160-166.

Claims (1)

A method of installing screws for transpedicular stabilization of the spine, including preoperative planning based on computed tomography, characterized in that on the basis of computed tomography a markup map is created by creating a multiplanar reconstruction, an image is formed on it based on which the insertion paths of the screws are marked, the distance between the points of insertion screws, the distance between the supraspinatus ligament and the point on the screw trajectory at the same level, according to the formed intra marking map the insertion points of the screws are operatively determined, the deflection angle in the sagittal plane is determined by the lateral x-ray and control, fixing the direction with the installation of an additional spoke, and the deflection angle in the axial plane is determined indirectly, based on the distance from the apex of the spinous process - supraspinatus ligament defined on the markup map, the deviation angle in the axial plane is controlled by the distance to the top of the spinous process - supraspinatus ligament using a marking compass with a ruler oh or caliper.

Images