RU193941U1 - STEM SCREW FOR OSTEOSYNTHESIS - Google Patents

Abstract

The utility model relates to medicine, to devices fixed to an external support, designed to ensure fixation of bone fragments. A screw rod for osteosynthesis is made in the form of a rod with a working end (1) and a fixing end (2), between which there is a cylindrical section (3 ) The working end (1) is equipped with a screw thread (4) and a cutting tip (5). The fixing end (2) is provided with a metric thread (6). In the cylindrical section (3), between the working (1) and fastening (2) ends, two symmetrical parallel flats (7) with round edges (8) are made. The technical result consists in reducing the width of the scar on the skin at the place of installation of the screw-shaft with maintaining a sufficient moment of resistance of the rod-screw to bending during distraction. 5 cp f-ly, 9 ill.

Description

Technical field

The utility model relates to medicine, traumatology and orthopedics, to devices fixed to an external support, designed to ensure fixation of bone fragments.

External fixation devices (AVF) are widely known and are used in clinical practice for bone osteosynthesis. The prior art apparatus G.A. Ilizarova for transosseous osteosynthesis (source [1]: SU 1055499; source [2]: SU 538710). Ilizarov’s apparatus is a set of standard parts (flat rings, half rings, spokes, threaded rods, bolts, nuts, brackets, special fixators, spoke holders) of various sizes, made in the form of a set of parts from which you can assemble many different, simple and complex AVFs. To fix the bone fragments in the AVF, screws (Shants screw, shaft-screw) and spokes (Kirchner spokes, flexible elastic metal rods) made of cylindrical shape are used. Knitting needles and screws are secured in the AVF to supports and other parts. With knitting needles and / or screw rods drawn through the bone fragments, the forces are transferred to the bone fragments and their fixation. Screw rods, as a rule, have a cylindrical shape and a diameter of 4 to 6 mm, are quite rigid and are cantilevered to the supports. The spokes, as a rule, have a diameter of 1 to 2 mm, the cap is usually 1.5 and 1.8 mm, are fixed on a support from two ends, i.e. typically a spoke has two attachment points.

Known needles for osteosynthesis (source [3]: patent RU 135252). A spokes for osteosynthesis contains a cylindrical rod made of a metal material having inert properties to the biological medium. The pointed end of the spoke has cutting edges.

With distraction osteosynthesis, for example, with lengthening of the lower leg (see Fig. 1), knitting needles [1; 2; 3] (pos. 8 in Fig. 1) is carried through through the limb and fix the bone. The needle is fixed at two points and stretched, this ensures its ability to withstand the load and fix the bone. In this case, two punctures with a diameter of up to 2 mm are formed in the soft tissues. Each puncture is a “window” for infection to penetrate, and the larger the diameter of the spoke, the larger this “window” and the higher the likelihood of infection. When installing one spoke, two wounds are formed on the limbs. During distraction, the needles move together with the support and pull, cut the skin, and a scar or scar forms on the skin (pos. 9 in Fig. 1). The width of the scar depends on the diameter of the spoke, the larger the diameter, the wider the wound and the larger the scar. From one needle, after distraction, two scars form on the skin of the limb. Therefore, screw rods are often used for distraction support.

A known rod-screw to the apparatus for transosseous osteosynthesis (source [4]: patent RU 19638). The screw rod will have a cylindrical rod, which is equipped with a conical pointed working end and a fixing end. The working end has a sharpening made at an angle, and a cone-shaped section on which a resistant trapezoidal thread is made, in addition, contains a smooth cylindrical section. At the mounting end, a thread and a portion having faces are made. The maximum diameter of the conical section and the diameter of the smooth cylindrical section is from 4 mm to 5 mm.

The use of a rod-screw [4] allows to reduce the number of punctures in soft tissues, since only one puncture is required (Fig. 2). However, in order to withstand the bending forces arising in the process of distraction from the side of the bone, it must be rigid and have the required diameter, as a rule, the cylindrical section has a diameter of 4 mm to 6 mm, providing the necessary moment of resistance to the bending moment arising from distraction from efforts transmitted from the side of the bone. Screw rods [4] with a diameter of 4 or 5 mm (pos. 10 in Fig. 2; 3), during distraction, also form a wide scar on the skin (pos. 9 in Fig. 2; 3) up to 6 mm wide, even wider than knitting needles.

Known rod-screw (source [5]: patent RU 14826;) containing a working part with a screw thread, limited by a thrust pad, a cylindrical mounting part. On the fastening part, a stress concentrator is made, located in a plane perpendicular to the axis of the screw rod and located between the thrust pad and the fastening end.

The screw-rod [5] is intended for installation in vertebral bodies, and is not intended for the distraction of tubular bones. The diameter of the cylindrical part is from 4 to 6 mm. Moreover, when it is used for distraction of the tubular bone, a scar and a wide scar form on the skin.

Known rod-screw for transpedicular fixation of the spine (source [6]: patent RU 40003). The screw rod [5] is made in the form of a rod, one end of which is equipped with a screw thread, limited by a thrust pad, and the other with a metric thread. At the end with a metric thread, a flat is made, at the last there are strokes of the scale, the distance between which is 1 mm, at the end with a metric thread a turn-key place is made.

A screw-rod [6] is intended for installation in vertebral bodies, and is not intended for distraction of tubular bones. The diameter of the cylindrical part is from 4 to 6 mm. Moreover, when it is used for distraction of the tubular bone, a scar and a wide scar form on the skin.

Thus, the problem is that the use of knitting needles in AVF during distraction osteosynthesis of the tubular bone leads to the formation of two scars up to 2 mm wide (Fig. 1). The use of a screw rod (pos. 10 of Fig. 2; 3) leads to the formation of one wide scar (pos. 9 of Fig. 2; 3) with a width of 4 to 6 mm. Reducing the diameter of the cylindrical part of the screw-rod, less than 4 mm, in order to reduce the width of the scar leads to the fact that it becomes unable to withstand the distraction forces and bends, since when the diameter decreases, the moment of resistance of the cross section also decreases.

The essence of the technical solution

The objective of this utility model is to improve the shaft-screw for osteosynthesis of tubular bones, in order to reduce the traumatic effect of the shaft-screw on the skin during distraction.

The technical result consists in reducing the width of the scar (scar) on the skin, at the place of installation of the screw rod, while maintaining a sufficient moment of resistance of the rod screw to bending during distraction.

The technical result is achieved by the fact that the shaft-screw for osteosynthesis is made in the form of a rod with a working end and a fixing end, between which there is a cylindrical section, the working end is equipped with a screw thread and a cutting tip, the fixing end is equipped with a metric thread. On the cylindrical section, between the working and fixing ends, two symmetrical flats with round edges are made.

The specified essence allows you to fix the bone fragment with two rods, screws, to carry out distraction and at the same time reduce skin injury and the width of the scar on the skin after treatment. The bending strength of the rod-screw does not significantly suffer and allows it to withstand the applied bending loads acting in the distraction plane.

The technical solution is illustrated by the following graphic materials:

FIG. 1 is a knitting distraction diagram;

FIG. 2 is a diagram of the distraction of the rods, screws;

FIG. 3 - a scar on the skin from the shaft-screw;

FIG. 4 - screw rod for osteosynthesis, general view;

FIG. 5 - a screw rod for osteosynthesis, with a cut off part, a cross section of a cylindrical part is shown;

FIG. 6 - a scar on the skin from the shaft-screw for osteosynthesis;

FIG. 7 - screw rods screwed during distraction;

FIG. 8 - rod-screw, longitudinal section;

FIG. 9 - shows bending forces acting on the rod-screw.

1 - working end;

2 - fixing end;

3 - cylindrical section;

4 - screw thread;

5 - cutting tip;

6 - metric thread;

7 - flats;

8 - scraping;

9 - a scar (scar);

10 - a spoke;

11 - rod-screw (analog).

12 - screw rod.

Implementation of a utility model.

Example. 1 The screw rod 12 (shown in Fig. 4; 5; 8) for osteosynthesis is made in the form of a rod with a working end 1 (Fig. 4; 5; 8) and a fixing end 2 (Fig. 4; 8) between which there is a cylindrical section 3 (Fig. 4; 5; 8). The working end 1 is equipped with a screw thread 4 (Fig. 4; 5; 8) and a cutting tip 5 (Fig. 4; 5; 8). The fixing end 2 is provided with a metric thread 6 (Fig. 4; 8). On the cylindrical section 3, between the working 1 and the fixing 2 ends, two symmetrical parallel flats 7 (Fig. 4; 5; 6; 8) with rounded edges 8 (Fig. 4; 5; 8) are made.

Example. 2 The rod-screw 12 (shown in Fig. 6; 7) for osteosynthesis is made in the form of a rod, with a working end 1 (Fig. 4; 5) and a fastening end 2 (Fig. 4;) between which there is a cylindrical section 3 (Fig. 4; 5) with a diameter of 6 mm. The material for the manufacture of the rod-screw is titanium alloy. The screw rod 12 has an anodic oxide coating. The working end 1 is equipped with a screw thread 4 (Fig. 4; 5) and a cutting tip 5 (Fig. 4; 5). The fixing end 2 is provided with a metric thread 6 (Fig. 4). On the cylindrical section 3, between the working 1 and the fixing 2 ends, two symmetrical parallel flats 7 (Fig. 4; 5; 6) with round edges 8 (Fig. 4; 5) are made. The depth of flats is from 1.5 mm, i.e. the minimum width of the cross section of the cylindrical section 3 is 3 mm, which leads to the formation of a scar 3 mm wide (Fig. 6). The length of the flats 7 is 10 mm. Screw cutting is performed with a pitch of 2.75 mm, a depth of 1.25 mm.

Example. 3 The rod-screw 12 (Fig. 4; 5) for osteosynthesis is made in the form of a rod, with a working end 1 (Fig. 4; 5) and a fixing end 2 (Fig. 4;) between which there is a cylindrical section 3 (Fig. 4 ; 5) with a diameter of 6 mm. The material for the manufacture of the stem-screw is stainless steel. The screw-rod 12 has a polymer coating of the cylindrical part. The working end 1 is equipped with a screw thread 4 (figure 4; 5) and a cutting tip 5 (figure 4; 5). The fixing end 2 is provided with a metric thread 6 (figure 4). On the cylindrical section 3, between the working 1 and the fixing 2 ends, two symmetrical parallel flats 7 (Fig. 4; 5) with rounded edges 8 (Fig. 4; 5) are made. The depth of flats is from 1 mm, i.e. the minimum width of the cross section of the cylindrical section 3 is 4 mm, which leads to the formation of a scar 4 mm wide (Fig. 6). The length of the flats 7 is 15mm. Screw cutting is performed with a pitch of 0.7 mm, a depth of 0.7 mm.

Example. 4 The rod-screw 12 (Fig. 4; 5; 8) for osteosynthesis is made in the form of a rod, with a working end 1 (Fig. 4; 5; 8) and a fixing end 2 (Fig. 4; 8) between which there is a cylindrical section 3 (Fig. 4; 5; 8) with a diameter of 4 mm. The material for the manufacture of the rod-screw is titanium alloy. The working end 1 is equipped with a screw thread 4 (figure 4; 5; 8) and a cutting tip 5 (figure 4; 5; 8). The fixing end 2 is provided with a metric thread 6 (Fig. 4; 8). On the cylindrical section 3, between the working 1 and the fixing 2 ends, two symmetrical parallel flats 7 (Fig. 4; 5; 8) with round edges 8 (Fig. 4; 5; 8) are made. The depth of flats is from 1 mm, i.e. the minimum width of the cross section of the cylindrical section 3 is 2 mm, which leads to the formation of a scar 2 mm wide. The length of the flats 7 is 15 mm. Screw cutting is performed with a pitch of 0.7 mm, a depth of 1.25 mm.

Example. 5 The rod-screw 12 (shown in Fig.6; 7) for osteosynthesis is made in the form of a rod, with a working end 1 (Fig.4; 5) and a fixing end 2 (Fig.4;) between which there is a cylindrical section 3 (Fig .4; 5) with a diameter of 6 mm. The material for the manufacture of the rod-screw is titanium alloy. The working end 1 is equipped with a screw thread 4 (figure 4; 5) and a cutting tip 5 (figure 4; 5). The fixing end 2 is provided with a metric thread 6 (figure 4). On the cylindrical section 3, between the working 1 and the fixing 2 ends, two symmetrical parallel flats 7 (Fig. 4; 5; 6) with rounded edges 8 (Fig. 4; 5) are made. The depth of flats is 2 mm, i.e. the minimum width of the cross section of the cylindrical section 3 is 2 mm, which leads to the formation of a scar 2 mm wide (Fig. 6). The length of the flats 7 is 20 mm. Screw cutting is performed with a pitch of 2.5 mm, a depth of 1 mm.

To measure the magnitude of parameters, expressed in the form of ranges of continuously changing values, the depth of the flats, the pitch and the depth of the screw thread, it is assumed to use known measuring tools. Use measuring tools used to control the size of parts, vernier calipers, threaded templates. Vernier caliper is a universal tool designed for highly accurate measurements of external and internal dimensions, as well as hole depths. The caliper serves to measure the depths of grooves, grooves, ledges, etc. It differs from the caliper in that it does not have movable jaws on the bar. Threaded patterns are used to determine the pitch and angle of the thread profile.

 Use of utility model.

A screw rod for osteosynthesis is used in AVF for osteosynthesis of tubular bones, such as the lower leg or shoulder. The screw-rod is installed on the distraction support of the AVF (the support that moves with the bone fragment fixed in it to lengthen the bone or replace the defect). The screw-rod 12 with a working end 1 with a screw thread 4 and a cutting tip 5 is screwed into a bone (bone fragment) so that the flats 7 of the cylindrical section 3 are located in the contact area of the screw-rod 12 with the skin. The flats 7 planes are set parallel to the direction of distraction (as a rule, this direction coincides with the longitudinal axis of the elongated bone). The fastening end 2 with a metric thread 4, the rod-screw 12 is mounted on the support of the AVF, fasten it to the support with fasteners (bolts, nuts, brackets). To fix the bone fragment, two screw rods 12 are used. The flatter planes 7 of each screw rod 12 are oriented parallel to the direction of distraction. With this installation, the front edge of the cylindrical section 3 with flats 7 in contact with the skin when moving the screw rod has the smallest transverse dimension than the main part of the cylindrical section 3. The width of the cylindrical section 3 with flats 7 acting on the skin will be the smallest. In this case, the bending moment M (Fig. 9) from the distraction forces F (Fig. 9) acts in the flange of the flats 7, and the maximum moment of resistance created by the cross section of the cylindrical section 3 is provided in the same plane (in the plane of the main bending moment M). Due to what, the rod-screw 12 is able to withstand distraction efforts, while minimizing skin injury and reducing the width of the scar and the forming scar. The rounded edges of the 8 flats 7 reduce the mechanical stress in the contact area of the flats 7 with the skin and reduce its injury.

The screw rod for osteosynthesis can be manufactured at modern industrial enterprises and used in conjunction with parts Ilizarov apparatus.

Claims (6)

1. A screw rod for osteosynthesis, made in the form of a rod with a working end and a fixing end, between which a cylindrical section is located, the working end is provided with a screw thread and a cutting tip, the fixing end is provided with a metric thread, characterized in that between the working section is a cylindrical section and fixing ends, made two symmetrical parallel flats with round edges. 2. The screw rod according to claim 1, characterized in that the diameter of the cylindrical section is 6 mm 3. The screw rod according to claim 1, characterized in that the depth of the flats is from 1 mm to 2 mm. 4. The screw rod according to claim 1, characterized in that the screw cutting is performed in increments of 0.7 mm to 2.75 mm and a depth of 0.7 mm to 1.25 mm. 5. The screw rod according to claim 1, characterized in that it is made of steel. 6. The screw rod according to claim 1, characterized in that it is made of titanium with an anodized coating.

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