RU226941U1 - SCREW ROD FOR TRANSOSNEY OSTEOSYNTHESIS, SELF-DRILLING - Google Patents

Abstract

The utility model relates to medical equipment, to products used in traumatology and orthopedics for fixation of bones and bone fragments, in the treatment of fractures, bone pathologies of the musculoskeletal system, using transosseous osteosynthesis, external fixation. The self-drilling rod-screw for transosseous osteosynthesis is made in the form of a smooth cylindrical rod, contains a working end with a screw thread 1 and a fastening end with a triangular shank 2. In the area of the screw thread at the working end, a drill-type sharpening is made, containing a cone 3, from the surface of which, along the longitudinal axis of the rod, with entry at the level of the top of the cone, two symmetrical grooves 4 and 5 are made, located on opposite sides, the groove 4 and 5 is formed by two surfaces 6 and 7, located perpendicularly, with one surface 6 radius, the second surface 7 flat, the flat surfaces 7 of the grooves are spaced apart to form a bridge 8 at the top of the cone, and the screw thread is made over 12 mm and has a rung 9 2 mm long, and the grooves are made over 10 mm, the length of the screw shaft is from 120 mm to 250 mm. The technical result consists in reducing the risk of complications caused by the design of the fixation rod, associated with the installation of a rod-screw into the bone during the treatment of fractures, bone pathologies of the musculoskeletal system, using transosseous osteosynthesis and an external fixation device. 3 ill.

Description

Technical field

The technical solution relates to medical equipment, to products used in traumatology and orthopedics for fixation of bones and bone fragments, in the treatment of fractures, bone pathologies of the musculoskeletal system, using transosseous osteosynthesis, external fixation.

State of the art

A minimally invasive method of extrafocal transosseous osteosynthesis, which involves the use of external fixation devices that fix bones and fragments with bone anchors passing through soft tissue, is quite popular in the surgical practice of orthopedic traumatologists, both in the treatment of fractures and in the correction of deformities in different segments.

It is known to use Schanz screws in external fixation devices for attaching the supports of the device to the bone and fixing bone fragments. This is a round rod with a screw thread for insertion into the bone at one end and a metric thread for fastening in the apparatus at the other end, separated by a smooth section (Müller M., Algover M., Schneider R., Willinger X. Guide to internal osteosynthesis. M., 1996. P. 368).

A known rod-screw (patent RU 14826; Published: 09/10/2000) containing a working part limited by a thrust platform and a fastening part with a metric thread, separated by a smooth section. The working part is made pointed and equipped with a screw thread.

A rod-screw for a device for transosseous osteosynthesis is known (patent RU 19638; Published: 09/20/2001). The screw rod for the device for transosseous osteosynthesis contains a rod that is equipped with a conical pointed working end and a fastening end, separated by a smooth section. The working end has a point made at an angle in the range from 30° to 35°, and a cone-shaped section on which a persistent trapezoidal thread is made, in addition, a smooth cylindrical section. The fastening end has a thread and a section with edges. The maximum diameter of the conical section and the diameter of the smooth cylindrical section is 4 mm or 5 mm.

A rod-screw for an external fixation device is known (patent RU 143507; Published: 07/27/2014). A screw rod for an external fixation device, including a self-tapping and thread-forming part on one side, a threaded part on the other side, and a threadless section between them.

The disadvantages of known analogues are as follows

The screw rods are inserted using a drill. First, a channel is drilled into the bone, then a rod-screw is screwed into the bone with the working end with a screw thread. The working end of the screw rod passes through the bone or is immersed to a certain depth. Moreover, the working end of the screw rod, as a rule, passes through the first cortical layer of the bone, and exits through the second cortical layer, or rests against it.

When using these screw rods, in the process of inserting the working end into the bone, sometimes, unintentionally, the opposite cortical layer of the bone is split by the working end. Since the ratio of the length of the working end, the length of the smooth section of the rod and their diameters does not allow tactile control of the moment of through passage of the working end through the second cortical layer.

When using these screw rods, during the process of inserting the working end into the bone, the working end heats up due to friction, which can lead to burns of soft tissue and bone; after installing the screw rod, it becomes loose as a result of necrosis of bone tissue in the burn area.

Screw rods sometimes break in the area where the screw thread of the working part transitions to the smooth area. The transition between the screw thread of the working end and the smooth part of the screw rod is structurally a vulnerable area due to local weakening and concentration of mechanical stresses, which leads to fracture of the rod under destructive loads.

Insertion of rod-screws requires preliminary drilling of a channel in the bone, which increases the complexity of installing the external fixation device.

The design disadvantages of known rod-screws appear, for example, when used for osteosynthesis on the foot and ankle joint. Also, in elderly patients, with edocrine disorders, systemic osteoporosis, bone tissue has low density and instability of external fixation devices often occurs, most often due to angular displacement and loosening of the screw rods in the bone tissue. The effectiveness of extrafocal transosseous osteosynthesis increases with increasing stability of the external fixation apparatus and the rigidity of fixation of bone fragments, as the risk of secondary displacement of bone fragments decreases. In addition, the installation of bone fixators with minimal trauma to the bone and soft tissues, without preliminary drilling, also reduces the risks and increases the effectiveness of treatment using extrafocal transosseous osteosynthesis.

The threaded thread on the fastening end of the screw rod is a place for the accumulation of contaminants and bacteria from the environment, which are more difficult to remove than from a smooth area. In this case, the skin comes into contact with the fastening end and the risk of infection and the penetration of bacteria through the body of the screw rod into the wound increases.

Thus, the problem with known rod-screws is that they have design flaws that cause weakening of the connection between the rod-screw and the bone and, as a result, reduce the rigidity of fixation with the device. Unstable fixation is caused by the risk of the following complications: unintentional splitting of the second cortical layer, tissue burn, infection of the wound at the site of passage of the screw rods through the tissue, fracture of the screw rod at the transition of the working part to the smooth area.

The technical result consists in reducing the risk of complications caused by the design of the fixation rod, associated with the installation of a rod-screw into the bone during the treatment of fractures, bone pathologies of the musculoskeletal system, using transosseous osteosynthesis and an external fixation device.

The technical result is achieved by the fact that the self-drilling rod-screw for transosseous osteosynthesis is made in the form of a smooth cylindrical rod, contains a working end with a screw thread and a fastening end with a triangular shank. In the area of the screw thread at the working end, a sharpening is made, similar to a drill, containing a cone from the surface of which, along the longitudinal axis of the rod, starting at the level of the top of the cone, two symmetrical grooves are made, located on opposite sides, the groove is formed by two surfaces located perpendicularly, wherein one surface is radius, the second surface is flat, the flat surfaces of the grooves are spaced apart to form a bridge at the apex of the cone, and the screw thread is made over 12 mm and has a run-out length of 2 mm, and the grooves are made over 10 mm, the length of the screw shaft is from 120 mm to 250 mm.

The device is illustrated by drawings:

fig. 1 - screw rod, side view,

where A is a rear view of the fastening end; B - front view of the working end; Г - Г - cross-section of the working end in the area of the grooves;

fig. 2 - photograph, two screw rods of different lengths, 120 mm and 250 mm;

fig. 3- radiographs of an external fixation device on a limb with rods and screws.

Implementation of the device (Fig. 1, 2).

Example 1. A self-drilling rod-screw for transosseous osteosynthesis is made in the form of a smooth cylindrical rod 120 mm long, made of stainless steel. Contains a pointed working end with a screw thread 1 and a fastening end with a triangular shank 2. In the area of the screw thread at the working end, a sharpening is made, similar to a drill, containing a cone 3 from the surface of which, along the longitudinal axis of the rod, with entry at the level of the apex of the cone, two symmetrical grooves 4 and 5 located on opposite sides, the groove (4 and 5) is formed by two surfaces 6 and 7 located perpendicularly, with one surface 6 radial, the second surface 7 - flat, the flat surfaces 7 of grooves 4 and 5 are spaced apart to form jumpers 8 at the top of the cone, and the screw thread is made over a length of 12 mm, and has a runoff 9 2 mm long, and the grooves are made over a length of 10 mm.

Example 2. A self-drilling rod-screw for transosseous osteosynthesis is made in the form of a smooth cylindrical rod 250 mm long, made of VT6 titanium alloy. Contains a pointed working end, with a screw thread 1, a drilling end, and a fastening end with a triangular shank 2. The shank has a triangular cross-section with rounded corners. In the area of the screw thread at the working end, a sharpening is made, similar to a drill, containing a cone 3 from the surface of which, along the longitudinal axis of the rod, with entry at the level of the top of the cone, two symmetrical grooves 4 and 5 are made, located on opposite sides, a groove (4 and 5) is formed by two surfaces 6 and 7, located perpendicularly, with one surface 6 radial, the second surface 7 - flat, the flat surfaces 7 of the grooves 4 and 5 are spaced to form a jumper 8 at the top of the cone, and the screw thread is made over 12 mm, and has a run-out 9 with a length of 2 mm, and the grooves are made over a length of 10 mm.

A self-drilling rod-screw is a transosseous fixation element, consisting of a working part for screwing into bone or bone fragments for fixation in the Ilizarov apparatus. The working part of the screw rod, with a screw thread 1, intended for direct contact with the bone, is made with a conical thread 12 mm long with a drilling tip. This design allows you to install the rod-screw at the minimum speed of a surgical drill, without preliminary drilling of the canal, and due to the shortened screw thread 1, the passage of the rod through the cortical layers of the bone is accompanied by a characteristic short-term increase in resistance to the drill, which in turn eliminates the “splitting effect” the opposite cortical wall of the bone known when using conventional Schanz rods with standard cutting. In addition, the use of the described working part evenly distributes the load on the rod in the transition zone to the smooth part, this helps reduce the risk of fracture of the screw rod in the bone and minimizes the need to remove fragments when dismantling the apparatus system.

The self-drilling screw rod allows it to be fixed to the Ilizarov apparatus support using parts from the standard apparatus kit.

Use the device as follows.

The insertion of the screw shaft begins after the skin has been pre-treated with an antiseptic and a linear incision of 7 mm in length has been made. The rod is inserted using an orthopedic drill; the cortical plate is drilled at low speeds until light resistance appears on the drill, after which the insertion is stopped for a short time in order to avoid bone burns. Using a drill, having installed the fastening part of the screw rod, screw the latter with its working part into the bone or bone fragment to the smooth part (for example, the bones of the foot or lower leg (Fig. 3)). After the rod has cooled, continue inserting the rod into the opposite cortical layer of the bone until there is resistance to the drill, this indicates that the rod is jammed in the bone. The operation is continued by installing the screw rod in the support of the external fixation device using parts from the standard set.

The length of the screw thread is 12 mm, which allows you to fix the working end of the screw rod in the first cortical layer of the bone without crossing the second cortical layer (the cortical layer has a thickness of 3 to 6 mm) and eliminates unintentional splitting of the second cortical layer. Sharpening allows you to form cutting edges like a drill. Due to the presence of two extended grooves 10 mm long, almost the entire length of the screw thread, the conditions for heat dissipation when drilling bone are improved. The radial surface of the grooves ensures removal of chips from the cutting zone; taking into account the thickness of the cortical layer (3-6 mm), circulation of liquid and chips along the screw thread is ensured, which reduces tissue heating. The working end is completely immersed into the bone using a screw thread until it touches the smooth section of the rod. There is a smooth section in the soft tissues and a smooth fastening end comes out, which is easily treated with an antiseptic and is less contaminated than threaded ends, thus reducing the risk of wound infection at the site where the screw rods pass through the tissue. The screw thread is short (12 mm, with a total length of 120 mm to 250 mm) and extends into a smooth section with a runoff of 2 mm, which reduces the concentration of mechanical stress, and the transition point is not a dangerous section, and the smooth section of the rod rests on the bone, so that it eliminates the risk of fracture of the screw rod at the point where the working part transitions to the smooth section.

Due to the conical threaded part 12 mm long with a drilling tip, it is possible to install it at minimal speeds of a surgical drill, without preliminary drilling of the canal, minimizing the “splitting effect”, which is opposite to the beginning of the introduction of the cortical wall of the bone and reducing the risk of fracture of the rod-screw in the bone at the stage fixation in the Ilizarov apparatus.

Thus, eliminating the possibility of unintentional splitting of the second cortical layer, reducing the risk of tissue burns, wound infection at the site of passage of the screw rods through the tissue, fracture of the screw rod at the point of transition of the working part into the smooth area, the reasons for the weakening of the connection of the screw rods with the bone are eliminated and fragments, resulting in increased rigidity of fixation by the device and stability of fixation.

This reduces the risk of complications associated with the installation of a rod-screw into the bone during the treatment of fractures, bone pathologies of the musculoskeletal system, using transosseous osteosynthesis and an external fixation device.

Claims (1)

The screw rod for transosseous osteosynthesis is self-drilling, made in the form of a smooth cylindrical rod, containing a working end with a screw thread and a fastening end with a triangular shank, characterized in that in the area of the screw thread at the working end there is a sharpening containing a cone, from the surface of which, along longitudinal axis of the rod, with entry at the level of the apex of the cone, two symmetrical grooves are made, located on opposite sides, the groove is formed by two surfaces located perpendicularly, with one surface being radius, the second surface being flat, the flat surfaces of the grooves are spaced apart to form a bridge at the apex of the cone, and the screw thread is made over a length of 12 mm and has a run-out length of 2 mm, and the grooves are made over a length of 10 mm, the length of the screw shaft is from 120 mm to 250 mm.