RU219431U1 - COMPRESSION SCREW FOR FOOT BONE OSTEOSYNTHESIS - Google Patents

Abstract

The utility model relates to the field of medicine, namely to foot surgery, and can be used in traumatology and orthopedics in the treatment of diabetic foot syndrome, Charcot foot, Charcot-Marie-Tooth disease, post-traumatic multicomponent deformity of the foot, arthropathy of the Chopard, Lisfranc, ankle joint. The compression screw for osteosynthesis of the foot bones is made in the form of a cylindrical rod with a through axial channel 4 with a diameter of 2 mm, with an external screw thread at both ends. The thread at the ends 1 and 2 of the rod is multi-pitch unidirectional. At the first end 1 there is a socket 5 for torque transmission. The outer diameter of the thread of the first end 1 exceeds the outer diameter of the screw body in the thread-free section 3. The diameter of the screw body in section 3, free from threads, is from 5.5 to 7.5 mm. EFFECT: improved reliability of fixation of bone fragments during osteosynthesis of foot bones while providing ease of installation and compression at the junction of bones and/or bone fragments. 4 w.p. f-ly, 7 ill.

Description

The field of technology.

The utility model relates to the field of medicine, namely to foot surgery, and can be used in traumatology and orthopedics in the treatment of diabetic foot syndrome, Charcot foot, Charcot-Marie-Tooth disease, post-traumatic multicomponent deformity of the foot, arthropathy of the Chopard, Lisfranc, ankle joints.

The level of technology.

In osteosynthesis of the foot for fixation of bone fragments, it is known to use external fixation devices with transosseous wires or screws, extraosseous plates fixed with screws, intraosseous screws.

There are various designs of osteosynthesis screws designed to fix certain bones of the skeleton. However, most of them are not suitable, for various reasons, for fixing the bones of the foot in the treatment of diabetic foot, Charcot foot, Charcot-Marie-Tooth disease, post-traumatic multicomponent deformity of the foot, arthropathy of the foot joints. Features of fixation of the bones of the foot are associated with the geometric shape and size of the bones, with a high load on the foot, acting from the weight of the whole body, with the cyclic load when walking and dynamic impact, with bone density, with the thickness of the soft tissues covering the bones. The screws are subjected to considerable stress, with the foot particularly at risk of unintentional impact loads and screw failure. Cyclic loads can lead to micromovement of the screw, which requires reliable fixation of the screw in the bone and provision of compression at the junction of the bones fixed by the screw.

Known screw cannulated for osteosynthesis (source [1]: patent RU 81427), the screw contains a cannulated rod with a screw thread at the distal end and a head at the proximal end, the head has a turnkey socket.

The screw [1] is not suitable for fixing the bones of the foot, since the transverse dimension of the screw body, between the head and the screw thread, is significantly smaller than the transverse dimension of the screw thread, the dimensions of the screw are not suitable for fixing the bones of the foot of an adult. The body of the screw, located at the junction of bone fragments, is prone to bending and shearing. When a screw is inserted into bone fragments, the screw thread forms a channel in the bone that is larger in diameter than the transverse size of the screw body. The body of the screw, located between the head and the screw thread, does not rest on the bone and moves freely in the channel formed during the installation of the screw, and the head does not provide stabilization of the screw. The screw does not provide long-term compression at the junction of the bones, since the proximal end is not fixed in the bone and the screw quickly becomes loose.

Known screw for osteosynthesis (source [2]: patent RU 2661758). The screw is made in the form of a cylindrical rod with a head at one end and an external screw thread at the other. The head is equipped with a cone-shaped screw thread, and a socket for transmitting torque. It is characterized by a relatively thin body of the screw and a large head.

The screw [2] is not suitable for fixing the bones of the foot, since the diameter of the screw body is significantly smaller than the transverse size of the head, the head does not completely sink into the bone and does not provide stabilization, and there is no compressive force associated with the stretching of the screw body due to the difference in thread travel. The ratio of the length of the smooth section of the screw body and the threaded section does not allow placing the junction of bone fragments in the area of the smooth section and creating compression at the junction due to screw rotation. The body of the screw between the thread and the head, located at the junction of bone fragments, is prone to bending and shearing. When the screw is inserted into the bone fragments, the screw thread forms a channel in the bone, which is larger in diameter than the transverse size of the screw body. The body of the screw, located between the head and the screw thread, does not rest on the bone and moves freely in the channel formed during the installation of the screw, and the head does not provide stabilization of the screw, since it is not completely immersed in the bone. The screw does not provide long-term compression at the junction of the bones, since the proximal end is not fixed in the bone and the screw quickly becomes loose. In addition, the screw does not contain a channel for installing the guide pin, which complicates the technique of the operation and makes it difficult to position the screw. The dimensions of the screw do not allow it to be used for fixing the bones of the foot.

Known screw for osteosynthesis (source [3] patent: RU 2128222). The screw is made in the form of a cylindrical rod with a head at one end and an external screw thread at the other. The head is equipped with a socket for transmitting torque. It is characterized by a relatively thin screw body with a neck and a large head. The threaded part is made with an outer diameter of 3.5 mm, an inner diameter of 3 mm.

The screw [3] is not suitable for fixing the bones of the foot due to its geometric parameters, the screw neck is significantly smaller than the transverse size of the head, the head does not completely sink into the bone and does not provide stabilization, and there is no compressive force associated with the screw body stretching due to the difference in thread travel. The ratio of the length of the screw thread and the length of the neck does not allow placing the junction of bone fragments in the neck area and creating compression at the junction due to the rotation of the screw. The neck of the screw, located at the junction of bone fragments, is prone to bending and shearing. The screw does not provide long-term compression at the junction of the bones, since the proximal end is not fixed in the bone and the screw quickly becomes loose. In addition, the screw does not contain a channel for installing the guide pin, which complicates the technique of the operation and makes it difficult to position the screw. The dimensions of the screw do not allow it to be used for fixing the bones of the foot.

Known screw for osteosynthesis (source [4]: patent RU 2585735). The screw is made in the form of a cylindrical rod with an elongated head at one end and an external screw thread at the other. The head is equipped with a socket for transmitting torque. Characterized by a long threaded end and an elongated head with threaded and smooth areas.

The screw [4] is not suitable for fixing the foot bones, as the size of the screw does not allow it to be used for fixing the foot bones. The ratio of the length of the screw thread, made almost the entire length of the screw, and the length of the smooth section, do not allow to place the junction of bone fragments in the area of the smooth area and create compression at the junction due to screw rotation. In addition, the screw does not contain a channel for installing the guide pin, which complicates the technique of the operation and makes it difficult to position the screw.

Known fenestrated cannulated compression screw for osteosynthesis of fractures of the bones of the extremities (source [5]: patent RU 147760). The compression screw is made in the form of a cylindrical rod with a through axial channel, with an external screw thread at both ends. The outer diameter of the thread is 4 to 8 mm at one end and 9 to 11 mm at the other end, the outer diameter of the thread at both ends is greater than the outer diameter of the screw body.

The screw [5] is not suitable for fixing the bones of the foot, since the transverse size of the screw body, between the ends with a screw thread, is significantly less than the outer diameter of the thread. When a screw is inserted into bone fragments, the screw thread forms a channel in the bone that is larger in diameter than the transverse size of the screw body. The body of the screw, located between the head and the screw thread, does not rest on the bone, does not provide stabilization of the screw and fixation in the bone. The outer diameter of the thread of one end is from 9 to 11 mm, which will not allow it to be installed in the foot bones of most patients due to its size. There is no torque socket needed to drive the screw into the bone, the cylindrical end prevents the screw from cutting into the bone. The screw requires pre-drilling an auxiliary hole and cutting the thread with a tap, the thread of which exactly matches the thread profile of the screw, which complicates the operation technique.

A disadvantage of the known designs of screws is their unsuitability for osteosynthesis of the bones of the foot, especially with low bone density (osteoporosis).

The screws, subjected to normal foot loads, do not withstand the loads that occur when resting on the foot and / or walking, resulting in mobility at the junction of bone fragments and instability of their fixation, the screws break and bend. At the same time, the geometric characteristics, the ratio of the length and length of the threaded and smooth sections, the ratio of the diameters of the threaded and smooth sections, do not allow for a tight fit of the screw in the bone and compression at the junction of fragments. For prior art screws with a short thread-free region (smooth region), it is difficult to position the screw so that the bone junction is located in the thread-free region, but this is a necessary condition to ensure compression at the junction.

The technical problem to be solved by the claimed utility model is to ensure reliable fixation of bone fragments and / or bones of the foot, with a screw capable of withstanding the loads arising in the foot, providing a tight fit into the bone, and the ability to insert the screw along the guide pin and locate the junction of fragments in the screw section free from threads.

The essence of the utility model.

The technical result consists in increasing the reliability of fixation of bone fragments during osteosynthesis of the foot bones while providing ease of installation and compression at the junction of bones and/or bone fragments.

The technical result is achieved by the fact that the compression screw for osteosynthesis of the foot bones is made in the form of a cylindrical rod with a through axial channel for the guide pin, with external screw threads at both ends. The thread at the ends of the rod is made unidirectional, but of different pitch, at the first end there is a socket for transmitting torque, the outer diameter of the thread of the first end exceeds the outer diameter of the screw body free from the thread, the diameter of the screw body is from 5.5 to 7.5 mm, the thread of the second end along the line of depressions is made in the form of a cone, the length of the section free from the thread exceeds the length of each of the ends made with thread.

The compression screw is characterized in that the thread length of the first end is 15 mm and its pitch is 1.5 mm, the thread length of the second end is 30 mm, and its pitch is 3 mm.

The compression screw is characterized by having a length of 50 mm to 160 mm.

The compression screw is characterized by the fact that it is made of medical steel.

The compression screw is characterized by being made of titanium alloy.

The ratio of the diameters of the threaded sections and the section free from the thread ensures a tight fit of the screw in the bone, throughout the entire length of the screw it is compressed by the bone tissue and completely sinks into the bone. The extended first threaded end with the largest outer diameter of the thread provides stability due to fixation in the cortical layer of the bone.

The use of a socket and an axial channel enable precise insertion and screwing of the screw in the proper place.

Together with the diameter of the screw body from 5.5 to 7.5 mm (taking into account the permissible deviations inevitable during manufacture), which provides the necessary bending strength, these features achieve reliable fixation of bone fragments during osteosynthesis of the foot bones.

The utility model is illustrated by graphic materials:

fig. 1 - compression screw for osteosynthesis of the bones of the foot;

fig. 2 - compression screw for osteosynthesis of the foot bones; length 50 mm, screw body diameter 5.5 mm;

fig. 3 - compression screw for osteosynthesis of the bones of the foot; length 160 mm, screw body diameter 6 mm;

fig. 4 - compression screw for osteosynthesis of the foot bones; length 90 mm, screw body diameter 7 mm;

fig. 5 - photograph of screws of different lengths;

fig. 6 - radiograph of the foot before treatment

fig. 7 - radiograph of the foot after treatment, the installed screws are visible.

Graphic materials indicate:

1 - first end;

2 - second end;

3 - section free from threads;

4 - through axial channel;

5 - nest.

The implementation of the utility model (Fig. 1).

The compression screw for osteosynthesis of the foot bones is made in the form of a cylindrical rod with a through axial channel 4 with a diameter of 2 mm, with an external screw thread at both ends. The thread at the ends of rods 1 and 2 is unidirectional, but with different pitches. At the first end 1 there is a socket 5 for torque transmission. The outer diameter of the thread of the first end 1 exceeds the outer diameter of the screw body in the section 3 free from the thread. The diameter of the screw body in section 3 free from threads is from 5.5 to 7.5 mm. The length of the section 3 free from the thread exceeds the length of each of the threaded ends 1 and 2. At the second end 2, the thread along the line of depressions is made in the form of a tapering cone, with cutting edges, which allows the thread to cut into the bone and screw the screw into the bone without pre-threading the bone.

Example 1 (Fig. 2).

The compression screw for osteosynthesis of the foot bones is made of a titanium alloy in the form of a cylindrical rod, with an external screw thread, with the first end 1 and the second end 2 equipped with a thread, between which there is a thread-free section 3. The thread at the ends of the 1 and 2 rods is made unidirectional, but of different pitch, which is necessary to create a different course in the bone during the rotation of the screw and tighten the fragments. The diameter of the screw body in section 3 free from threads is 5.5 mm. The screw contains a through axial channel 4 for the guide spokes. At the first end 1 there is a socket 5 for transmitting torque from a tool, such as a wrench or a screwdriver. The outer diameter of the thread of the first end 1 exceeds the outer diameter of the screw body in the thread-free section 3 and is 6 mm. The thread along the line of depressions at the second end 2 is made in the form of a tapering cone. Thread with cutting edges, which allows the thread to cut into the bone and drive the screw into the bone without first cutting the thread into the bone. The self-tapping thread at the end 2 is made with a cone, which, after drilling the auxiliary channel in the bone, allows the screw to be inserted by simply twisting. The screw length is 50 mm. The length of the thread-free section is 25 mm, the length of the first end 1 is 8 mm, the length of the second end 2 is 17 mm.

Example 2 (Fig. 3).

The compression screw for osteosynthesis of the foot bones is made of a titanium alloy in the form of a cylindrical rod, with an external screw thread, with the first end 1 and the second end 2 equipped with a thread, between which there is a thread-free section 3. The thread at the ends of the 1 and 2 rods is made unidirectional, but of different pitch, which is necessary to create a different course in the bone during the rotation of the screw and tighten the fragments. The diameter of the screw body in section 3 free from threads is 6 mm. The screw contains a through axial channel 4 for the guide spokes. At the first end 1 there is a socket 5 for transmitting torque from a tool, such as a wrench or a screwdriver. The outer diameter of the thread of the first end 1 exceeds the outer diameter of the screw body in the thread-free section 3 and is 7 mm. The thread along the line of depressions at the second end 2 is made in the form of a tapering cone. The self-tapping thread at the end 2 is made with a cone, which, after drilling the auxiliary channel in the bone, allows the screw to be inserted by simply twisting. The length of the screw is 160 mm. The length of the thread-free section is 90 mm, the length of the first end 1 is 45 mm, the length of the second end 2 is 15 mm.

Example 3 (Fig. 4).

The compression screw for osteosynthesis of the foot bones is made of steel in the form of a cylindrical rod, with an external screw thread, with the first end 1 and the second end 2 equipped with a thread, between which there is a section 3 free from the thread. The thread at the ends of the 1 and 2 rods is made unidirectional, but of different pitch, which is necessary to create a different course in the bone during the rotation of the screw and tighten the fragments. The diameter of the screw body in section 3 free from threads is 7 mm. The screw contains a through axial channel 4 for the guide spokes. At the first end 1 there is a socket 5 for transmitting torque from a tool, such as a wrench or a screwdriver. The outer diameter of the thread of the first end 1 exceeds the outer diameter of the screw body in the thread-free section 3 and is 8 mm. The thread along the line of depressions at the second end 2 is made in the form of a tapering cone. The screw length is 90 mm. The length of the thread-free section is 45 mm, the length of the first end 1 is 15 mm, and its linear pitch is 1.5, the length of the second end 2 is 30 mm, and its pitch is 3 mm.

The compression screw (Fig. 5) for osteosynthesis of the foot bones can be made of medical steel 12X18H10T, approved for use as implants for humans, does not cause rejection of the body, provides sufficient strength and rigidity of fixation, and is resistant to angular and axial loads. The size range of screws is presented in sizes from 50 mm to 160 mm, which allows performing osteosynthesis of damaged foot bones regardless of the size of the segment. The compression screw can be used for deformities of the navicular, sphenoid, cuboid bones, for subluxations in the talonavicular joint, for defects in the talus and calcaneus.

Compression screw for osteosynthesis of foot bones is made of titanium alloy VT6, approved for use as implants for humans, does not cause rejection of the body, provides sufficient strength and rigidity of fixation, is resistant to angular and axial loads. The combination of structural elements (the presence of a compression screw with unidirectional multi-pitch threads at both ends) and the geometric dimensions of the screw (the ratio of the screw body diameter and the outer diameter of the first end 1) provide a strong fixation of the foot bones during osteosynthesis, help to withstand the load associated with body weight when resting on the foot. The compression screw can be used for defects of the tibia and fibula.

The compression screw for osteosynthesis of the foot bones is installed as follows.

With damage to the bones of the middle part of the foot.

After antiseptic treatment of the surgical field, the patient is placed on the operating table, an open corrective intervention is performed on the affected area of the foot skeleton, namely: all existing components of the deformation and displacement of individual bones are eliminated to a radiologically confirmed satisfactory position. After manual removal of the first toe to the position of dorsal flexion, a linear incision of 2 cm is made from the plantar surface of the head of the first metatarsal bone. In the direction from the head of the first metatarsal bone to the talus, a conductor wire is inserted intramedullarily. A cannulated drill is used to ream the bone canal. After reaming the bone, the guide determines the depth of the bone canal and the required length of the compression screw for osteosynthesis. After determining the length, the compression screw for osteosynthesis is implanted into the prepared bone canal. Produce X-ray control of the correctness of the position of the implanted compression screw. The wound is sutured tightly. In order to stabilize the lateral column of the foot, radiographically optimal point for implantation of the screw (3-4 metatarsal bones) is determined. From the plantar surface in the projection of the head of ¾ of the metatarsal bone, after a linear incision of 1 cm, a guide wire is inserted towards the calcaneus, the bone canal is reamed and the length of the screw is determined. Without removing the conductor, a compression screw of the required length with a diameter of 5.5 mm is inserted. Produce X-ray control of the correct implantation of the compression screw. If necessary, increase the rigidity of fixation of the midfoot bones by introducing two compression screws through the bones of the lateral column.

With damage to the bones of the hindfoot and ankle joint

After antiseptic treatment of the surgical field, the patient is placed on the operating table, an open corrective intervention is performed on the affected ankle joint, namely, all existing components of the deformation and displacement of individual bones are eliminated to a radiologically confirmed satisfactory position. From the plantar surface in the region of the hindfoot towards the distal metaepiphysis of the tibia, two conductor wires are carried out. Perform x-ray control of the correctness of the position of the spokes. A cannulated drill drills the bone channels along each of the conductors. After reaming the bone, the guide determines the depth of the bone canal and the required length of the compression screw for osteosynthesis. After determining the length, the compression screw is implanted into the prepared bone canal. Produce X-ray control of the correctness of the position of the implanted screw. The wound is sutured tightly. In order to provide additional rigidity, an additional compression screw can be implanted in the direction from the outer/inner malleolus towards the talus.

Clinical example (Fig. 6; 7).

Patient T., 65 years old. Diagnosis: Diabetic foot syndrome. Bilateral DNOAP. Chronic osteomyelitis of the right ankle joint in remission. Shortening of the right lower limb 5 cm. Chronic fracture-dislocation of the left Choparov joint. Concomitant diagnosis: Hypertension II stage, AH2 R 3 CHF1 dyslipidemia FK2, type 2 diabetes mellitus with a glycated Hb level of 10%, retinopathy, angiopathy of the vessels of the n / extremities, diabetic nephropathy CKD C2 A3, obliterating atherosclerosis of the vessels of the n / extremities. HAN 1 st, secondary iron deficiency anemia of mild degree.

On radiographs of the left foot in 3 projections is determined: deformation, heterogeneous structure of the scaphoid, sphenoid, cuboid bones. Subluxation in the talonavicular joint upwards. The site of cystic restructuring in the projection of the base of the proximal phalanx of the 2nd finger, 5 mm by 7 mm in size, with clear, sclerotic contours. Narrowing of the joint space, sclerosis of the articular surfaces of the 1st metatarsophalangeal, subtalar joints.

On radiographs of the right foot in 3 projections is determined: a defect in the distal tibia, fibula. Total defect of the talus. Heel defect. Fringed periostitis of the fibula, tibia. Hyperostosis, osteosclerosis of the tibia, fibula. Osteosclerosis of the calcaneus, bones of the tarsus, metatarsus. Extended spoke passages in the projection of the tibia with a shadow suspicious of a sequester. Tibiocalcaneal diastasis up to 13 mm.

Taking into account the clinical and radiological picture, the patient underwent surgical intervention: elimination of deformities of the left and right feet. Metal osteosynthesis of the bones of the left and right feet with screws.

In the long-term period, 8 months after osteosynthesis, no complications were noted in the patient.

Claims (5)

1. A compression screw for osteosynthesis of the foot bones, made in the form of a cylindrical rod with a through axial channel for the guide pin, with external screw threads at both ends, characterized in that the thread at the ends of the rod is unidirectional, but of different pitch, at the first end there is a socket for transmitting torque, the outer diameter of the thread of the first end exceeds the outer diameter of the screw body, free from thread, the diameter of the screw body is from 5.5 up to 7.5 mm, the thread of the second end along the line of the depressions is made in the form of a cone, the length of the section free from the thread exceeds the length of each of the threaded ends. 2. Compression screw according to claim 1, characterized in that the length of the thread of the first end is 15 mm, and its pitch is 1.5 mm, the length of the thread of the second end is 30 mm, and its pitch is 3 mm. 3. Compression screw according to claim 1, characterized in that it has a length of 50 mm to 160 mm. 4. Compression screw according to claim 1, characterized in that it is made of medical steel. 5. Compression screw according to claim 1, characterized in that it is made of a titanium alloy.