RU2852469C1 - Spinal fixation system with submergible structures - Google Patents

Abstract

FIELD: veterinary medicine.

SUBSTANCE: invention can be used for submersible fixation of the spine, mainly in cats and dogs, in cases of cervical, thoracic and lumbar injuries. The system for fixing the spine with submersible structures includes longitudinal cylindrical beams, screws for insertion into pre-prepared channels in the vertebral body, and fixing units in the form of a housing with holes for installing beams, screws and clamping pins. Spinal fixation is performed using monoaxial fixation units with headless vertebral screws and polyaxial fixation units with spherical-headed vertebral screws. The fixation units are installed using an installation rod, an installation screw and a mounting device.

EFFECT: expansion of the arsenal of existing means for spinal osteosynthesis, stability of fixation of the injured spine, and a reduction in the time required to install the structure due to the simplicity of assembly.

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Description

The invention relates to veterinary traumatology and orthopedics of the spine, more precisely to structures for the immersion fixation of the spine of animals, primarily cats and dogs, in case of injuries to the cervical, thoracic and lumbar regions.

In veterinary traumatology and orthopedics, the search for new, more advanced methods of treating animals with spinal instability is relevant, but the successful implementation of reconstructive surgeries requires reliable fixation and improvement of osteofixators that prevent unstable fixation of the vertebrae, as well as the development of destructive changes in the bone-articular joints of the injured segments.

A dynamic internal spinal fixator (Patent 194566 U1, RU, IPC A61B 17/70 (2006), 2019) is known. It contains transpedicular screws mounted on a rigid longitudinal rod via attachment points. The screws are designed to be inserted into the pedicle or sacrum of the spine to a predetermined depth and angle. The attachment points are designed as tuning fork-type heads equipped with a hole for the transpedicular screw, a groove for the longitudinal rod, and a thread for a clamping screw. Designing the attachment points as tuning fork-type heads equipped with a hole leads to mechanical weakening of the attachment points, increases the risk of screw failure under load, and does not provide reliable and stable fixation.

A device for transosseous osteosynthesis of the spine for stabilizing spinal segments in animals with injuries is known (patent 163458 U1 RU, IPC A61D 1/00, 2016). The device comprises rods, transverse rods for insertion into the vertebral body, located on the rods, locking nuts, and pressure washers. One end of the transverse rod is made with a wedge-shaped expansion, the second - with a thread and a groove for the rod. Three interconnected plates are mounted on the transverse rod. The rods are made of nitinol. Holes are drilled in the vertebral bodies adjacent to the damaged ones at an acute angle to the spinous processes. The transverse rod, equipped with three interconnected plates, is inserted with the wedge-shaped part into the resulting hole, a pressure washer is placed on the rod, and a locking nut is screwed on. The rods inserted into the vertebral bodies are connected by two longitudinal rods. Fixing nuts are then sequentially tightened over the rods. Disadvantages include limited variability in the angle of each individual screw during repositioning and insufficient fixation of the vertebral bodies.

A device for transpedicular fixation of vertebrae in lumbar spondylolisthesis (Patent 117799 U1 RU, IPC A61B 17/70, 2012) is known. It comprises two beams rigidly fixed with screws and connected by a cross beam, with both beams secured with four mono- or polyaxial screws. A disadvantage of this device is the inability to insert screws at an angle and insufficient fixation rigidity.

The closest in technical essence is the spinal fixator (patent 2197915 C1, RU, IPC A61B 17/70, 2001), used as a structure for fixing damaged spinal segments. The device consists of at least two transpedicular screws, attachment units, and a longitudinal beam. The screws are designed for installation in the pedicles of two adjacent vertebrae and provide a mechanical connection between the two vertebrae, and are rigidly connected to the longitudinal beam by an attachment unit. Each attachment unit consists of a housing with two mutually perpendicular holes, one for the longitudinal rod, the other for the screw, as well as threaded holes for clamping screws to fix the position of the attachment unit on the longitudinal rod and the position of the transpedicular screw. The attachment unit is connected to the screw through a split spherical sleeve installed in the hole. The fixation unit housing has a flat slot intersecting the holes intended for the longitudinal rod and transpedicular screw, ensuring clamping in a direction perpendicular to their axis. During surgery, screws are inserted into the vertebral bodies. A fixation unit is placed on each screw, which is then mounted on the longitudinal rod. Two clamping screws are then used to compress the flat slot, simultaneously securing the inserted screw and the fixation unit on the longitudinal rod. A disadvantage of this fixation unit is its unreliable fixation on the longitudinal rod, which depends on the degree of compression of the flat slot. For this reason, the installed screw may slip, affecting the stability of the fixation. Another disadvantage is the large number of clamping screws, which increases the duration of the surgery.

The objective of the invention is to improve the existing design.

The technical result of using the invention is that the proposed design ensures stable fixation of the injured spine and reduces installation time due to its ease of installation. This technical result expands the range of existing spinal osteosynthesis tools.

The claimed technical result is achieved by modifications to the device, which includes longitudinal cylindrical beams, screws for insertion into pre-prepared channels in the vertebral body, and fixation units in the form of a housing with holes for installing the beam, screws, and clamping screws. The system utilizes monoaxial fixation units with headless screws and polyaxial fixation units with spherical-head screws. The fixation unit housing is designed as a tetrahedral elongated prism with a through oval hole for the longitudinal beam, a hole for a clamping pin on one of the two end surfaces of the housing, and a through smooth channel for a screw, which is angled to the longitudinal axis of the housing and located on the adjacent face relative to the hole for the longitudinal beam. In the housing, the openings for the longitudinal beam, the clamping pin, and the screw channel intersect within the housing. The channel for the spherical-head screw has an inlet diameter corresponding to the diameter of the spherical head of the screw, and the outlet diameter corresponds to the diameter of the threaded portion of the screw. The fixation units are installed using a mounting rod, a mounting screw, and a mounting fixture. Furthermore, the longitudinal axis of the through-hole oval hole for the beam is parallel to the longitudinal axis of the housing. To pre-prepare the channels in the vertebral bodies, a pilot drill is used. This drill consists of a cylindrical guide with a drill bit whose diameter corresponds to the diameter of the screw for insertion into the spine. The drill is secured in the guide with adhesive. To install the monoaxial fixation unit, a pilot screw is used. This screw consists of a cylindrical guide and a headless vertebral screw, which is installed in a blind hole in the end of the guide with adhesive. To install a polyaxial fixation unit, a mounting device is used that is designed to accommodate a spherical head screw in the body of the mounting device.

The essential distinctive features of the claimed invention, which ensure the achievement of the stated technical result, are that:

The use of monoaxial and polyaxial fixation nodes for fixing damaged spinal segments makes the system more variable and versatile compared to the prototype. Complex, stable fixation is possible through the simultaneous use of polyaxial fixation nodes on the sacral spine and monoaxial nodes on the lumbar spine.

- the design of the fixation unit housing in the form of a tetrahedral elongated prism with a through oval hole for the beam, with a hole for the clamping pin on one of the two end surfaces of the housing, with a through smooth channel for fixing the screw, made at an angle to the longitudinal axis of the housing and located on the adjacent face in relation to the hole for the beam, allows for the fixation of screws of various diameters, insertion into the vertebrae to a given depth and angle, taking into account the individual characteristics of the vertebra, the angle of inclination of the vertebral pedicle;

- The use of a longitudinal beam hole, a clamping pin hole, and a channel intersecting within the housing for monoaxial or polyaxial fixation units allows for simultaneous fixation of the longitudinal beam and screw (monoaxial or polyaxial) with a single clamping pin. This ensures stable and rigid fixation, promotes favorable conditions for vertebral fusion, and speeds up system assembly/disassembly during operation.

These significant differences indicate compliance with the inventive step criterion. Patent research conducted under IPC subclass A61B 17/70, as well as a review of available scientific publications related to transpedicular osteosynthesis in the treatment of dogs and cats with spinal instability, revealed no technical solutions with features consistent with the claimed invention, allowing us to conclude that the proposed technical solution is novel. Manufacturing the proposed system components does not require complex or expensive equipment, and the cost will not be an obstacle to widespread use.

The invention is explained by description and figures:

Fig. 1 - general view of the structure;

Fig. 2 - screw without head;

Fig. 3 - screw with spherical head;

Fig. 4 - housing for fixing a headless screw;

Fig. 5 - assembly diagram of the monoaxial fixation unit;

Fig. 6 - assembled monoaxial fixation unit;

Fig. 7 - housing for fixing a screw with a spherical head;

Fig. 8 - assembly diagram of the polyaxial fixation unit;

Fig. 9 - installation drill;

Fig. 10 - set screw;

Fig. 11 - device for mounting a polyaxial fixation unit, general view;

Fig. 12 - device for mounting a polyaxial fixation unit;

The spinal fixation system using immersion structures (Fig. 1) consists of cylindrical longitudinal beams 1 and monoaxial and polyaxial fixation units. Each fixation unit contains a housing and a screw for insertion into the vertebral bodies. Screw 2 (Fig. 2) is intended for use in monoaxial fixation units, and screw 3 (Fig. 3) is intended for use in polyaxial fixation units. Screw 2 is a headless rod with an external thread, while screw 3 has a spherical head with a recess for a mounting device.

For each type of the fixation unit, the body of the fixation unit, made in the form of a tetrahedral elongated prism, has design features. The body 4 (Fig. 4) is intended for fixing the screws 2 without heads. In the body 4, a through hole 5 of an oval shape is provided, the longitudinal axis of which is parallel to the longitudinal axis of the body 4, intended for insertion of the beam 1. The body 4 has a through channel 6 without threads, located on the face adjacent to the hole 5, made at an angle to the longitudinal axis of the body, intended for installation of the screw 2. The diameter of the channel 6 corresponds to the diameter of the screw 2. On the end surface of the body 4, a threaded hole 7 is made up to the intersection with the hole 5, intended for installation of the clamping threaded stud. Opening 5 and channel 6 intersect within housing 4, allowing beam 1 and screw 2, inserted into housing 4, to be clamped simultaneously by clamping pin 8 (Fig. 5) in a rigid and secure manner. To disassemble the clamping unit, simply loosen clamping pin 8. Loosening clamping pin 8 allows for adjustment of housing 4's position on beam 1 by performing linear movement and rotation.

The assembly of the monoaxial fixation unit is carried out as follows. Fig. 6 shows the monoaxial unit for fixing the screw 2 on the longitudinal beam 1 with the housing 4. To mount the structure as part of an operation to immobilize the spine, a channel for the screw is pre-drilled to a certain depth in the vertebral bodies adjacent to the damaged ones, using the installation drill 13 (Fig. 9). Then, a pre-prepared installation screw 14 (Fig. 10) is inserted into the channel and the conductor part is cut off with nippers, leaving the screw 2 of the required length in the vertebra, which is used to form the monoaxial fixation unit. The housing 4 is installed through the channel 6 on the screw 2 (Fig. 5) and the longitudinal beam 1 is inserted into the housing 4 through the oval-shaped through hole 5. A clamping pin 8 is inserted into the end hole 7 and, without tightening the fixation unit with the pin, the optimal position of the fixation unit is selected. In this position, body 4 is capable of linear movement along longitudinal beam 1. Body 4 is also capable of changing its position relative to screw 2 in the radial direction, allowing the screw to be secured in the optimal position. Once the fixation unit is assembled, the unit is clamped with a clamping pin. This simplifies manipulation during surgery and reduces the time required to install the unit. Fixation units are installed on the remaining vertebrae in a similar manner.

The body 9 (Fig. 7) is intended for forming polyaxial fixation units and, similar to the body 4, has a through hole 10 of oval shape, intended for inserting the beam 1, the longitudinal axis of which is parallel to the longitudinal axis of the body 9. The body 9 has a through channel 11 without threads, located on the adjacent face with respect to the hole 10, made at an angle to the longitudinal axis of the body 9, intended for installing the screw 3. The diameter of the inlet hole of the channel 11 corresponds to the diameter of the spherical head of the screw 3, the diameter of the outlet hole corresponds to the diameter of the threaded part of the screw 3. On the end surface of the body 9 there is a threaded hole 12 up to the intersection with the hole 10, intended for installing the clamping threaded stud. Opening 10 and channel 11 intersect within housing 9, allowing beam 1 and screw 2, inserted into housing 4, to be clamped simultaneously by clamping pin 8 (Fig. 8) in a rigid and secure manner. To disassemble the clamping unit, simply loosen clamping pin 8. Loosening clamping pin 8 allows for adjustment of housing 9's position on beam 1 through linear and circular movement. Furthermore, the spherical head of screw 3 allows for adjustment of screw 3's angle and selection of the optimal position.

The assembly of the polyaxial fixation unit is carried out as follows. As part of the spine stabilization operation, a channel is drilled in the vertebral body at the required angle for mounting the immersion structure using installation drill 13 (Fig. 9). Then, the housing 9 is installed on the longitudinal beam 1 and the clamping pin 8 is inserted into the housing 9, leaving it in a loose position. Screw 3, located in the mounting fixture 15, is inserted into the housing 9 and then inserted into the channel in the vertebral body prepared by the installation drill 13. By rotating the fixture 15, screw 3 is immersed to the required depth, after which the fixture 15 is removed. The housing 9 with the loosened clamping pin is capable of moving along the longitudinal beam 1, and, thanks to the spherical head of the screw 3, it can deviate from the axis, and after the required position is selected, the clamping pin 8 is tightened tightly.

The system for fixing the spine using immersion structures provides for the use of a mounting drill 13 (Fig. 9), a mounting screw 14 (Fig. 10) and a mounting device 15 (Fig. 11).

The installation drill 13 (Fig. 9) is used for preliminary preparation of the channels intended for installation of screws 2, 3 in the vertebral body. The installation drill 13 consists of a cylindrical rod (guide) and a short drill, the diameter of which corresponds to the diameter of the screw for insertion into the spine, i.e., a headless screw or a screw with a spherical head. A blind hole is made in the end of the guide, into which the drill is installed using glue. After drilling a channel through the thickness of the skin and muscles at the required angle to the vertebra, the installation drill 13 is removed, and the installation screw 14 or mounting device 15 is inserted into the prepared channel.

Set screw 14 (Fig. 10) is designed to install headless screw 2 and form a monoaxial fixation unit and consists of a rod portion (conductor) and screw 2. The conductor, of a specified length and diameter, is made of stainless steel or titanium alloy. At one end of the conductor there is a blind channel for installing screw 2. A quick-hardening adhesive mass is introduced into the channel and screw 2 is inserted. After the adhesive mass has hardened, set screw 14 is ready for use in the surgery. The prepared set screw 14 (Fig. 10) is inserted to the required length into the canal in the vertebra and the conductor portion is cut off with nippers, and screw 2 remaining in the vertebra is used to form the monoaxial unit.

The mounting device 15 (Fig. 11) within the framework of the present invention is used for inserting the screw 3 with a spherical head into the canal in the vertebral body and for forming a polyaxial fixation unit. The mounting device 15 consists of a sleeve 16 with internal thread, a lateral groove 17 and a threaded rod 18. Before the operation, the spherical head of the screw 3 is installed in the sleeve 16 through the lateral groove 17, then pressed by the threaded rod 18. The device 15 with the installed screw 3 is inserted into the housing 9, and then the threaded end of the screw 3 is immersed in the canal in the vertebra. After installing the screw 3, the device is removed.

Example

A mongrel dog, weighing 22 kg and approximately 5 years old, was admitted to the BION+ veterinary clinic in Sevastopol after a traffic accident with signs of numbness in the pelvic limbs. X-ray examination revealed a displacement between the 6th and 7th lumbar vertebrae and a crack in the 6th lumbar vertebra. The animal was diagnosed with a lumbar spinal fracture-dislocation. After anesthetizing the animal and preparing the surgical field, an incision was made in the skin and muscles over the spinous processes of the fracture area toward the 5th lumbar and sacral vertebrae, and the vertebral arches in the fracture area were scalped. A laminectomy was then performed on the 6th and 7th lumbar vertebrae. The external condition of the spinal cord was assessed. Next, using a 13-mm drill bit at a 45° angle to the 5th lumbar vertebra on the right, the 13-mm drill bit was inserted through a small skin incision, progressively perforating the muscles, and then directly toward the vertebra. A preparatory channel was then created in the vertebral body. A pre-prepared 14-mm drill bit was then inserted into the pre-prepared musculocutaneous channel and screwed into the vertebral body. A portion of the 14-mm drill bit was then cut off from the side of the surgical wound, leaving 2-mm drill bit of the required length to form a monoaxial fixation node. A guidewire was prepared for each screw. A similar procedure was performed on the left side, and screws were inserted into the prepared channels into the 6th and 7th lumbar vertebrae on each side.

After preliminary drilling of the vertebrae using mounting device 15, a polyaxial fixation unit was installed into the sacrum on each side using screw 3 with a spherical head.

Next, cylindrical longitudinal beams 1 were inserted into all monoaxial fixation nodes, starting from the 5th lumbar vertebra and ending with the insertion of cylindrical longitudinal beams on both sides in the polyaxial fixation nodes installed on the sacrum.

The vertebrae were then positioned in their natural position, and cylindrical beams 1 were secured in housings 4 of the monoaxial fixation units and housings 9 of the polyaxial fixation units using clamping pins 8 (Fig. 1). The remaining fragments of screws 2 and 3 were cut off with pliers. The surgical wound was then closed tightly. Antibiotic therapy was administered postoperatively. The structure is non-removable. The animal had an unsteady gait on the 7th day after surgery. The skin sutures were removed on the 16th day. On the 16th day, the animal was able to move fairly well.

The proposed device demonstrated stability of fixation of the injured spine, ease of installation, and the absence of complications.

Claims (5)

1. A system for fixing the spine using immersion structures, including longitudinal cylindrical beams, screws for insertion into pre-prepared channels in the vertebral body, fixation units in the form of a housing with holes for installing the beam, screws and clamping pins, characterized in that the system contains monoaxial fixation units with screws for vertebrae without a head and polyaxial fixation units with screws for vertebrae with a spherical head, the housing of the fixation unit is made in the form of a tetrahedral elongated prism with a through oval hole for the longitudinal beam, with a hole for the clamping pin on one of the two end surfaces of the housing, with a through smooth channel for the screw for the vertebrae, made at an angle to the longitudinal axis of the housing and located on an adjacent face with respect to the hole for the longitudinal beam, and the holes for the longitudinal beam, for the clamping pin and the channel for the screw for the vertebrae mutually intersect inside the housing, while the channel for the screw with a spherical head has a diameter the inlet hole corresponding to the diameter of the spherical head of the screw, and the diameter of the outlet hole of the channel corresponds to the diameter of the threaded part of the screw, and the installation of the fixing units is carried out using a set drill, a set screw and a mounting device. 2. A system for fixing the spine using immersion structures according to paragraph 1, characterized in that in the housing of the fixation unit the longitudinal axis of the through oval hole for the longitudinal beam is parallel to the longitudinal axis of the housing. 3. A system for fixing the spine using immersion structures according to paragraph 1, characterized in that the installation drill for preliminary preparation of canals in the vertebral body consists of a cylindrical conductor with a drill, the diameter of which corresponds to the diameter of the screw for insertion into the spine, and the drill is fixed in the conductor using glue in a blind hole located in the end of the conductor. 4. A system for fixing the spine using immersion structures according to paragraph 1, characterized in that the mounting screw for mounting the monoaxial fixation unit consists of a cylindrical conductor and a headless vertebral screw installed in a blind hole in the end of the conductor using glue. 5. A system for fixing the spine using immersion structures according to paragraph 1, characterized in that the mounting device for mounting the polyaxial fixation unit is designed with the possibility of installing a screw with a spherical head in the body of the mounting device.