RU211140U1 - Navigation device for screw insertion during transpedicular fixation on the thoracic and lumbar spine - Google Patents

Abstract

The utility model relates to medicine, namely to traumatology, and is intended for use in the installation of fixing transpedicular screws on the thoracic and lumbar regions in case of injuries and diseases of the spine.

The navigation device contains a guide in the form of two vertical bars with spacers along the edges, in which movable sliders are installed, which can change the distance from the center of the device and rotate around the axis. The device is equipped with a U-shaped base with a ruler for moving along the vertebral arches with the possibility of fixing with rods at the base of the spinous vertebrae. The base is rigidly connected to additional vertical bars, which end with a handle for easy positioning relative to the axis of the vertebra. To change the inclination in the sagittal plane, the base and the guide are connected by a movable axis at the bottom of the bars and an adjusting screw at the top of the bars.

The navigation device ensures the accuracy of screw insertion and reduces the operation time. 10 ill.

Description

The utility model relates to medicine, namely to traumatology, orthopedics, neurosurgery. It can be used as a mechanical navigation system in surgery for transpedicular fixation in the treatment of injuries and diseases of the thoracic and lumbar spine.

The remaining technical errors associated with the passage of pedicle screws past anatomical landmarks are up to 5% (Usikov V.V., Usikov V.D., 2006; Bublik L.A. et al., 2007; Berdyugin K.A., Karenin M.S., 2010; Schwab F.J., Nazarian D.G., Mahnmud F. et al, 1995; Davne S.H., 1999), which leads to the search for solutions to reduce these complications.

To insert a pedicle screw, it is necessary to clearly know the point of insertion and the angles of inclination in the sagittal and axial planes, taking into account the anatomy of each vertebra. Modern x-ray systems, such as O-arm or intraoperative computed tomography, allow you to obtain images directly in the axial projection. Navigation systems have also been developed and are being used to significantly improve the accuracy of screw installation. Significant disadvantages of these methods are complexity and high price, which limits their wide application. For this reason, alternative methods and techniques for determining the points and angles of screw insertion continue to be published. The first known methods for placing pedicle screws involved identifying "typical" insertion points from anatomical landmarks. Many methods have been proposed for determining such points.

A known method for determining the direction of insertion of transpedicular screws in pediculocorporal osteosynthesis of the lower thoracic and lumbar vertebrae, RF patent No. 2204341, IPC A61B 17/56. The screws are inserted through the accessory processes of the vertebrae, taking into account the given angles of deviation, the minimum transverse dimensions of the pedicles of the vertebral arches, and the distance between the accessory processes of the vertebrae. After the exposure of the posterior bone structures of the lower thoracic or lumbar spine, based on the given positions and distances between the accessory processes of the vertebrae, the location of the latter is determined. Taking into account the known values of the deviation angles of the minimum transverse dimensions of the pedicles of the vertebral arches, transpedicular screws are inserted into the accessory processes.

With this method, damage to the cortical layer of the pedicles of the vertebrae is excluded. The disadvantages of this method are:

- the use of averaged tabular data: deviation angles, minimum transverse dimensions of the pedicles of the vertebral arches and the distance between the accessory processes;

- difficulties in detecting accessory processes, especially in violation of the anatomy of the spine.

A known method of installing screws for transpedicular stabilization of the spine, RF patent No. 2620355, IPC A61V 17/56. On the basis of the performed 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 in DICOM format, on which the screw insertion trajectories, the distance between the supraspinous ligament and a point on the screw trajectory at the same level are marked. Based on the marking map generated intraoperatively, the points of screw insertion are determined individually. The angle of deflection in the sagittal plane is determined from the lateral x-ray, and the angle of deflection in the axial plane is determined indirectly based on the distance from the apex of the spinous process, determined on the markup map. Technically, during the operation, regardless of the pathology, the first stage is the installation of screws (on unchanged anatomy). Based on the markup map, the screw insertion points are determined in relation to the surrounding bone structures, including above and below the insertion points. An additional factor of accuracy is the measurement of the distance between injection points. Knitting needles are installed at the selected points, the deviation angle in the sagittal plane is controlled by the lateral x-ray image. The direction is fixed by installing an additional needle (usually in the spinous process). A tool is introduced to form a pin channel, while the angle of deviation in the sagittal plane is controlled by the installed additional needle, and the angle of deviation in the axial plane is controlled by the distance to the top of the spinous process (supraspinous ligament), for which a marking compass with a ruler or a caliper is used. When installing the screw, the angles in the axial plane are also controlled by the distance to the top of the spinous process (supraspinous ligament) and in the sagittal plane by the installed additional needle.

The advantages of the method are:

- more precise insertion of pedicle screws;

- does not require the use of expensive devices and navigation systems;

- allows X-ray control only in the lateral projection, which reduces the radiation exposure to the patient and staff and makes it possible to use a conventional operating table.

The disadvantages of the method include:

- the search for screw insertion points in case of impaired anatomy is difficult: incorrect determination of one insertion point can lead to an error on the opposite side based on the measured distance between the insertion points;

- the angle of inclination in the sagittal plane is controlled intraoperatively using an additional needle in the spinous process; in this regard, the meaning of calculating the angle of inclination in the sagittal plane is unclear if it cannot be set intraoperatively;

- the deflection angle in the axial plane may be inaccurate if the position of the marking compass with a ruler or vernier caliper does not coincide with a plane parallel to the plane of screw insertion.

As a prototype, we took a navigator for transpedicular fixation, RF patent No. 137191, IPC A61V 17/90, characterized in that it contains a guide consisting of two bars rigidly interconnected in the center by an insert with screws and two spacers along the edges, with two movable nodes in the form of sliders, and the sliders are installed with the possibility of determining the angle of convergence, changing the distance from the center of the navigator, the angles of rotation around the axis and are fixed with nuts. In addition, the latch is equipped with a clamp with nuts and washers, with the help of which the navigator is fixed, a threaded rod for moving the insert along it with nuts and washers for fixing the insert, as well as a bracket and a node that provides changes in the angle of the navigator in the sagittal plane and rigid perpendicular position of the navigator relative to the axis of the vertebra. The main parameters of the navigator installation are: the distance from the top of the spinous process to the center of the horizontal part of the navigator; the position of the optimal point of insertion of the rod (according to the methodological recommendations, the applied technology or anatomical features); the position of the point of convergence of the rods; position of the line of insertion of the rod; magnitude of the minor leg and the angle of convergence a.

The benefits of using this navigator include:

- low cost when using a three-dimensional navigation model;

- declared accurate insertion of pedicle screws;

- assembly, adjustment of a mechanical navigator and installation of rods outside the vertebra, which reduces the time of the operation itself;

- rigid fastening by the spinous processes from the sides makes it possible to move the navigator along the spine and fasten it in the right place.

The disadvantages of this useful navigation model include the lack of explanations:

- on the collection of data on the parameters of the installation of the navigator;

- about how the introduction planes are set on the navigator;

- about how the position of the navigator is controlled in the sagittal plane, if the direction of insertion of the screw in the sagittal plane is not included in the main parameters of the navigator installation;

- about the practical application of the navigation model.

The objectives of the utility model are to improve the accuracy of transpedicular screws in the thoracic and lumbar regions in case of injuries and diseases of the spine and to reduce the time of surgical intervention with a decrease in radiation exposure.

The problem was solved by the fact that the well-known navigation device, containing a guide in the form of two vertical bars with spacers and movable sliders and a node for changing the inclination in the sagittal plane, is equipped with a U-shaped base with a ruler for moving along the vertebral arches with the possibility of fixing with rods at the base of the spinous processes. The base is rigidly connected in the center with additional vertical bars, which end with a handle for convenient positioning of the device relative to the axis of the vertebra and keeping it in the wound. The base and the guide are movably connected by an axis in the lower part of the additional bars and an adjusting screw in the upper part of the additional bars to change the inclination of the insertion of taps and pedicle screws in the sagittal plane.

The essence of the proposed solution is illustrated by figures:

Fig. 1. Schematic representation of the navigation device in the sagittal projection.

Fig. 2. Schematic representation of the device in axial projection.

Fig. 3. Schematic representation of the device, top view.

Fig. 4. Photo. Appearance of the device.

The navigation device contains a U-shaped base (1) with a ruler for moving along the vertebral arches, 15 mm wide, which is fixed by rods (2) at the base of the spinous processes. The base (1) is rigidly connected in the center with additional vertical bars (3) and a handle (4) for convenience of positioning the device relative to the axis of the vertebra and keeping it in the wound. The movable part of the device (guide) is represented by two vertical bars (5) placed between additional bars (3). Vertical strips (5) are perpendicularly connected at the edges with spacers (6) (two spacers on each side), the centers of which are at a distance of 70 and 120 mm from the lower plane of the device. In spacers (6) there are movable units in the form of sliders (7) with the possibility of changing the distance from the center of the navigator, which sets the slope in the axial plane. The sliders (7) are fixed to the spacers with screws (8). In the centers of the sliders (7) there are round holes (9), in which the screws (10) are fixed first with the taps (11), and then the central rods of the pedicle screws. Additional vertical bars (3) of the U-shaped base (1) and vertical bars (5) of the guide at the bottom are movably connected by an axis (12), and in the upper part these vertical bars are connected by an adjusting screw (13) with nuts (14) to set the inclination to sagittal plane.

The navigation device is used after preoperative planning based on the results of computed tomography, which consists in multiplanar reconstruction and the creation of a marking map for each pedicle screw. The stages of reconstruction are shown in the illustrations:

Fig. 5. Multiplanar reconstruction, determination of distances A and B.

Fig. 6. Multiplanar reconstruction, determination of distances K _R , K _L .

Fig. 7. Multiplanar reconstruction, determination of distances C _R , C _L , D _R , D _L .

Fig. 8. Multiplanar reconstruction, determination of distance E.

Fig. 9. Multiplanar reconstruction, determination of distance F.

Fig. 10. Summary table of distances after multiplanar reconstruction.

Let us consider the use of a navigation device on the example of a patient with a compression-comminuted fracture of the ThVIII vertebral body.

For each pedicle screw, an image is formed and the insertion trajectory is determined, and a marking map is created. The map shows: A - the distance between the points of insertion of screws (Fig. 5); by distances K _R and K _L select the length of the screw (Fig. 6); B - distance from the horizontal line in the axial projection passing through the arch of the inserted vertebra (with a cross section of the arch 15 mm) to a parallel line passing through the points of screw insertion in the axial projection (Fig. 5); C _R and C _L - the distance from the point located on the midline passing through the center of the vertebral body and the center of the arch (with a section of the arch of 15 mm) at a height of 70 mm to the points located on the perpendicular line at the intersection with the trajectory of the introduction of screws from two sides in axial projection (Fig. 7); D _R and D _L - distance from a point located on the midline passing through the center of the vertebral body and the center of the arch (with a section of the arch of 15 mm) at a height of 120 mm from the center of the arch to points located on a perpendicular line at the intersection with the insertion trajectory screws on both sides in axial projection (Fig. 7); E - distance from a point located at a height of 150 mm from a perpendicular line drawn through the arches of the injected and adjacent vertebrae (with a cross section of the arch of 15 mm) to a point located on the line of screw insertion at the same height in the sagittal projection (screw deviation in the sagittal projection ) (Fig. 8); F is the distance from the point on the arch of the inserted vertebra, located on the line drawn through the arches of the inserted and neighboring vertebrae (with a cross section of the arch of 15 mm) to the point of screw insertion on the same line in the sagittal projection (additionally for the lumbar region, since the arches in the lumbar section have a protruding sharp edge, where this point can be more clearly marked) (F) (Fig. 9). Based on the performed multiplanar reconstruction, a summary table with distances is created using the example of the ThVII vertebra (Fig. 10). According to the generated markup map, data from the table is transferred to the navigation device. The screws (8) loosen the sliders (7) on the spacers (6). The distances C _R and C _L on the bottom spacer, D _R and D _L on the top spacer are set and the screws (8) are tightened, thus forming the angle of convergence. Using the nuts (14) on the adjusting screw (13), the distance (E) is set (from the center of the connection of the adjusting screw to the center of the nearest adjusting nut), and thus we obtain the angle of inclination in the sagittal plane. According to the set distances (C _R , C _L , D _R , D _L , E), taps (11) are inserted into the holes (9) in the sliders (7), then the device is placed on a horizontal plane to set distances A and B. Moreover, when precise setting of the angle of convergence, setting the distance A, should get the distance B and vice versa. Using screws (10) at the set distances (A, B, C _R , C _L , D _R , D _L , E) the taps (11) are fixed on the sliders. When assembled, the navigation device is applied to the arches of two adjacent vertebrae (ThVI, ThVII), placing it strictly in the center of these vertebrae (as the marking was carried out), so that the markers are freely located between the arches (in this case, ThVI-ThVII) (Fig. 1) . In the lumbar region, in places where the device base is pressed against the vertebral arches, conditional points of contact will appear on the arches. When the device is moved along the spine from the ThVI arch to the ThVII arch, the taps will hit the bone obstruction of the ThVII arch, i.e. the markers will indicate the calculated screw insertion points on the pedicles of the ThVII vertebra. For stability, the device is pressed against the spine and fixed with rods to the base of the spinous processes. The rods are threaded and limited to the midline of the vertebrae. The screws (10) on the sliders are loosened, and the taps are inserted into the ThVII body by 10-15 mm along the given navigation trajectory from both sides. To ensure the position of the taps, X-ray control is carried out once in two projections. Taps thicken sharply after 45 mm to prevent accidental iatrogenic penetration deeper. While maintaining the navigation trajectories, the formation of channels for the propellers continues, focusing on the length of the channels in terms of distances K _R and K _L (Fig. 5); if necessary, the formed channels are examined with a probe. Then screws are inserted into the device on the central rods of the required length (taking into account the distances K _R and K _L ) and screwed into the prepared channels.

Thus, the navigation device allows: to ensure the accuracy of the introduction of screws due to the fact that their trajectory can be accurately set in the axial projection along the distances C _R , C _L , D _R , D _L on the spacers, rather than setting the angle of convergence on the sliders; in the sagittal projection, using the ruler, it is also easier to set the distance E than to set the angle of the navigator using the bracket and the knot; there is no connection with the apex of the spinous process or the interspinous ligament, slight deviations of which will lead to a deviation from the calculated insertion trajectories; the closer the main base of the device to the injection points, the less errors in determining the injection points; reduce radiation exposure to the patient by reducing the number of images (no more than 8 images per installation of 6 screws, taking into account the final X-ray control of the structure); reduce the time of the operation due to the fact that the marking and insertion of the screws are carried out simultaneously on both sides and the number of images is reduced.

Clinical example: Patient C., aged 35, was admitted for treatment in the neurosurgical department after an accident with a diagnosis of OPSI. Comminuted fracture of the LII vertebral body with contusion and compression of the epiconus of the spinal cord. lower paraparesis.

After the CT scan, a multiplanar reconstruction of the spine was performed with the data entered into the markup map. Anesthesia - endotracheal anesthesia. Layered posterior approach to the damaged spine. For screws in the LI and LIII vertebrae, the data from the layout map were sequentially transferred to the navigation device. The navigation device with fixed data for the LI vertebra was lowered into the wound on the arches of the LI, LII vertebrae, moved towards the LI vertebra, until the taps rested against the bone obstacle of the arch of the LI vertebra; the rods on the U-shaped base were screwed from both sides into the base of the spinous process of the LI vertebra; the screws on the spacers that fix the taps were loosened, and at the same time, the taps sank from both sides to a depth of up to 2 cm; image intensifier tube control was performed in 2 projections and made sure that the trajectories of the taps coincide with the calculated ones; further formation of channels with 45 mm taps (before taps expand); the taps are removed and a thread is cut along the same trajectory through the navigation device along the formed channels; the rods on the U-shaped base are unscrewed and 50 mm screws on the central rods are inserted into the navigation device; with the same parameters, the navigation device is returned to the wound with screws, where the tips of the screws are oriented into the formed channels, and the rods are screwed into the previous holes; screws are screwed along a given trajectory; the screws on the spacers are loosened and the navigation device is removed. Then the data from the markup map is transferred to the navigation system for the LIII propeller; the device is placed in the interarticular space LIII-LIV, and the manipulations are repeated as for the LI vertebra. After the introduction of the screws, an image intensifier tube control was performed (3rd in a row). A repositioning system was applied, axial traction of the spine was performed, and a significant straightening of the body of the LII vertebra and correction of kyphotic deformity of the spine were obtained. Through pre-assembled couplings on the outer longitudinal rods of the repositioning system, under image intensifier tube control, reduction screws were introduced, and further manipulations with the nuts on the central rods completely eliminated the deformation of the anterior wall of the spinal canal. Transpedicular screws are interconnected on both sides by modeled fixing rods. The repositioning system was dismantled, and the wound was sutured in layers with drains. Aseptic bandage. By the end of the first week there was a regression of neurological disorders. The wound healed by first intention, and after 11 days the patient was transferred to the medical rehabilitation department.

Claims (1)

A navigation device for inserting screws during transpedicular fixation on the thoracic and lumbar spine, containing a guide in the form of two vertical bars, between which spacers with movable sliders are placed at the edges, installed with the possibility of changing the distance from the center of the device and with the possibility of rotation around the axis and fixation in spacers, a unit for changing the inclination of the screws in the sagittal plane, characterized in that the device is equipped with a U-shaped base with a ruler for moving along the vertebral arches with the possibility of fixing with rods at the base of the spinous processes, while the base is rigidly connected in the center with additional vertical bars, which end with a handle for positioning the device relative to the axis of the vertebra and holding it in the wound, in addition, round holes are made in the centers of the movable sliders for fixing the taps with screws first, and then the central rods of the pedicle screws, and the guide I and the base are connected by a movable axis at the bottom of the bars and an adjusting screw at the top of the bars to change the inclination of the screws in the sagittal plane.

Images