Device for assisting in repairing and reconstructing mandible

Abstract

The invention aims to provide a device for assisting in repairing and reconstructing a mandible, and relates to the technical field of medical instruments, during an operation, the head of a patient leans against a pillow seat, limiting plates on the two inner sides of the rear end of the pillow seat are rotated to slide oppositely to clamp and limit the head of the patient, and then the angle between the pillow seat and a deflection plate is adjusted, so that the patient can repair and reconstruct the mandible. By rotating the deflection plate, the deflection angle, fixed by the limiting plate, of the head of the patient is adjusted, one side of the mandible is exposed, and surgical operation is facilitated; the retainer can be fixed through the movable arm without being held by hands, so that manpower is liberated, and the retainer and the mandible can be fixed conveniently; fixing nails are nailed into the fixing holes in the retaining rod of the retainer, the retaining rod and the mandible are fixedly connected together, the situation that the position of the mandible condylar process is changed when a mandible bone block is cut off is prevented, and the mandible retainer can adapt to mandible shapes of people with different body types through stretching and retracting of the retaining rod and sliding of the retaining rod.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to a device for assisting mandibular repair and reconstruction. Background Art

[0002] The repair and reconstruction of mandibular bone defects is a hot topic in oral and maxillofacial surgery. The mandibular condylar joint is the only bilateral linkage joint in the body, and the bilateral condyles need to move together to complete the mouth opening movement. Mandibular bone defect is a defect in the bony structure of the mandible. Clinically, free bone reconstruction is usually required for bony structure defects, and the reconstruction method is commonly known as "taking money from one pocket to fill another". During the operation, the bony structure of the mandible is defective, so the doctor will take bones from other parts of the patient's body and then implant them into the mandible to repair the mandibular defect and restore the continuity of the patient's mandible. It is necessary not only to restore the morphology and facial contour of the mandible, but more importantly, to restore the physiological occlusal function of the mandible. However, in the clinical repair and reconstruction of mandibular bone defects, the following problems are often encountered:

[0003] 1. The position of the condyle is easy to change after the mandibular bone is cut. In clinical practice, it is generally necessary to rely on physician experience or 3D personalized printing technology to help restore the original position. Relying on clinical experience generally results in large errors and is related to the level of clinical physicians. 3D personalized printing technology brings convenience while also bringing high costs, which is inconsistent with the current DRG medical payment and people's pursuit of high-quality and low-cost medical services;

[0004] 2. Currently, in the repair and reconstruction surgery after mandibular defects, there is a lack of head fixation devices for patients. In order to facilitate the operation during the operation, the patient's head needs to be adjusted to adjust the patient's mandible to a position that is convenient for surgical operations. Due to the lack of special head fixation devices, doctors are often required to hold the patient's head by hand, which increases human resources. In addition, since doctors hold the patient's head by hand for a long time, they are prone to fatigue and there is a risk of the patient's head moving, which increases the risk of surgery. Summary of the invention

[0005] In view of the deficiencies of the prior art, the present invention provides the following technical solutions:

[0006] A device for assisting mandibular repair and reconstruction comprises a head fixing device and a retainer, wherein the head fixing device comprises a base, a deflection plate and a pillow seat, wherein the middle portion of the deflection plate is connected to a base rotating shaft, and a base sleeve is slidably arranged on the base, and a one-way screw rod is rotated on the base to drive the base sleeve to slide, thereby driving the deflection plate to rotate;

[0007] The rear end of the pillow seat is connected to the rear end rotating shaft of the deflection plate, and a deflection sleeve is slidably arranged on the deflection plate. The deflection sleeve is driven to slide by rotating a one-way screw rod 2 installed on the deflection plate, thereby controlling the rotation of the pillow seat;

[0008] Limiting plates are slidably provided on both sides of the rear end of the pillow seat, and a bidirectional screw rod is rotatably installed in the pillow seat to control the limiting plates on both sides to slide towards or away from each other on the pillow seat;

[0009] The retainer is detachably mounted on the pillow seat, and the retainer and the pillow seat are movably connected via a movable arm. The retainer comprises a T-shaped seat, two bidirectional screw rods, and retaining rods slidably mounted on both sides of the T-shaped seat. The retaining rods are telescopic structures, and a plurality of fixing holes are provided on the extended ends of the retaining rods. The upper portion of the extended end of the retaining rod on one side of the T-shaped seat is an arc-shaped structure that fits the position of the condyle of the mandibular bone. The two bidirectional screw rods are rotatably mounted in the T-shaped seat, and the retaining rods on both sides of the T-shaped seat are driven to slide toward or away from each other by rotating the two bidirectional screw rods.

[0010] Furthermore, a groove is provided on the base, the deflection plate is located above the groove, a transmission shaft is fixedly arranged at the lower middle part of the deflection plate, the transmission shaft is rotatably connected to the bottom of the groove, a gear is fixedly arranged at the tail end of the transmission shaft, the base sleeve is slidably installed inside the rear end of the base, and a serrated structure is provided on the base sleeve to mesh with the gear on the transmission shaft, the one-way screw rod 1 is rotatably installed inside the rear end of the base, the base sleeve is threadedly sleeved on the one-way screw rod 1, and the base sleeve is driven to slide by rotating the one-way screw rod 1, thereby driving the gear to rotate, so that the deflection plate and the transmission shaft rotate around the axis of the transmission shaft.

[0011] Furthermore, the deflection sleeve is slidably installed on the front end of the deflection plate, and the deflection sleeve is threadedly sleeved on the one-way screw rod 2. A push rod is arranged below the front end of the pillow seat. One end of the push rod is rotatably connected to the pillow seat, and the other end is rotatably connected to the deflection sleeve. There is a certain angle between the push rod and the deflection plate. The deflection sleeve is driven to slide by rotating the one-way screw rod 2, and the push rod is driven to rotate to lift the front end of the pillow seat, thereby adjusting the angle between the pillow seat and the deflection plate.

[0012] Furthermore, a pillow seat slide groove 1 is provided at the rear end of the pillow seat, and the bidirectional screw rod 1 is rotatably installed in the pillow seat slide groove 1. The limit plates on both sides of the pillow seat are respectively threadedly connected to the two ends of the bidirectional screw rod 1, and the bidirectional screw rod 1 is rotated to drive the limit plates on both sides to slide toward or away from each other along the pillow seat slide groove 1.

[0013] Furthermore, sliding grooves are provided on both sides of the cross bar of the T-shaped seat, and the two-way screw rod 2 is rotatably installed in the sliding groove. The lower end of the retaining rod is threadedly connected with the two-way screw rod 2, and the retaining rods on both sides of the cross bar of the T-shaped seat are driven to move toward or away from each other by rotating the two-way screw rod 2.

[0014] Furthermore, the movable arm includes a slider, a telescopic vertical rod, a telescopic cross rod and a mounting tube. The slider slides in a pillow seat slide groove 2 opened on the side of the pillow seat. The lower end of the telescopic vertical rod is fixedly connected to the slider, and the upper end is fixedly connected to the tail end of the telescopic cross rod. A ball head mechanism is arranged at the front end of the telescopic cross rod. The ball head mechanism includes a ball core and an outer shell fixedly connected to the telescopic cross rod. The ball core is movably installed inside the outer shell. A notch is opened on the outer shell. The mounting tube passes through the ball core from the notch of the outer shell and is fixedly connected to the ball core. The retainer is inserted into the mounting tube through the vertical rod of the T-shaped seat and is detachably connected to the mounting tube.

[0015] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0016] 1. The present invention rotatably connects the middle part of the deflection plate with the bottom of the groove of the base, and the rear end of the deflection plate is rotatably connected with the pillow seat, and limit plates are slidably arranged on both sides of the rear end of the pillow seat. During surgery, the patient's head rests on the pillow seat, and the limit plates on both sides of the pillow seat are driven to slide toward each other along the pillow seat slide groove 1 by rotating the two-way screw rod 1 inside the rear end of the pillow seat to clamp and limit the patient's head, and then the deflection sleeve is driven to slide by rotating the one-way screw rod 2 in the deflection plate, and the top rod is driven to rotate to lift the front end of the pillow seat, thereby adjusting the angle between the pillow seat and the deflection plate, so that the patient can keep the head slightly tilted back, and the one-way screw rod 1 in the rotating base is driven to drive the base sleeve to slide, thereby driving the gear on the transmission shaft under the deflection plate to rotate, and driving the deflection plate to rotate around the axis of the transmission shaft, thereby adjusting the deflection angle of the patient's head fixed by the limit plate, exposing one side of the mandible, and facilitating surgical operations;

[0017] 2. The present invention slides and installs a movable arm on one side of the pillow seat, and movably connects the installation tube with the telescopic cross bar of the movable arm through a ball head mechanism. During surgery, the retainer is fixedly installed in the installation tube, the movable arm is slid to the position of the patient's mandible, and the position of the retainer is adjusted to align with the mandible by telescopic adjustment of the telescopic vertical rod and the telescopic cross bar of the movable arm. The retainer can be fixed by the movable arm without hand support, which frees up manpower and facilitates the fixation of the retainer and the mandible, and facilitates the subsequent implantation of bones to repair and reconstruct the mandible.

[0018] 3. The retainer of the present invention comprises a T-shaped seat detachably connected to the mounting tube, and retractable retaining rods are slidably arranged on both sides of the T-shaped seat. The retaining rods on both sides are driven to move toward each other and closely fit the mandible by rotating the two-way screw rods in the T-shaped seat. The arc structure of the extended end of the retaining rod on one side can well fit the position of the mandibular condyle, and the extended end of the retaining rod on the other side is closely fit to the front end of the mandible. A fixing nail is nailed into the fixing hole on the retaining rod to fix the retaining rod and the mandible together to prevent the position of the mandibular condyle from changing when the mandibular bone block is removed. The retaining rod can adapt to the mandibular shape of people of different body shapes through the extension and extension and sliding of the retaining rod, better fix the mandible, and effectively avoid the change of the position of the condyle after the mandible is cut off. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention;

[0020] Figure 2 It is a schematic diagram of the cross-sectional structure of the deflection plate of the present invention;

[0021] Figure 3 This is a schematic diagram of the cross-sectional structure of the rear end of the bottom plate of the present invention;

[0022] Figure 4 It is a schematic diagram of the structure below the deflection plate of the present invention;

[0023] Figure 5 It is a schematic diagram of the structure of the movable arm of the present invention;

[0024] Figure 6 Schematic diagram of the retainer structure of the present invention.

[0025] In the figure: base-1, base sleeve-101, deflection plate-2, deflection sleeve-201, transmission shaft-202, pillow seat-3, pillow seat slide groove 1-301, pillow seat slide groove 2-302, top rod-303, movable arm-4, slider-401, telescopic vertical rod-402, telescopic horizontal rod-403, ball head mechanism-404, mounting tube-405, retainer-5, T-type seat-501, sliding groove-5011, two-way screw rod 2-502, retaining rod 503, fixing hole-5031, limit plate-6, two-way screw rod 1-7, unidirectional screw rod 1-8, unidirectional screw rod 2-9. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Embodiment 1:

[0028] See also Figure 1-6 A device for assisting mandibular repair and reconstruction includes a head fixing device and a retainer 5, wherein the head fixing device includes a base 1, a deflection plate 2 and a pillow seat 3, wherein the middle portion of the deflection plate 2 is connected to the rotating shaft of the base 1, and a base sleeve 101 is slidably arranged on the base 1, and the base sleeve 101 is driven to slide by rotating a one-way screw rod 8 arranged on the base 1, thereby driving the deflection plate 2 to rotate;

[0029] In this embodiment, a groove is provided on the base 1, the deflection plate 2 is located above the groove, a transmission shaft 202 is fixedly arranged at the lower middle part of the deflection plate 2, the transmission shaft 202 is rotatably connected to the bottom of the groove, a gear is fixedly arranged at the tail end of the transmission shaft 202, the base sleeve 101 is slidably installed inside the rear end of the base 1, and a serrated structure is arranged on the base sleeve 101 to mesh with the gear on the transmission shaft 202, the one-way screw rod 101 is rotatably installed inside the rear end of the base 1, the base sleeve 101 is threadedly sleeved on the one-way screw rod 101, the one-way screw rod 101 is rotated to drive the base sleeve 101 to slide, thereby driving the gear to rotate, and driving the deflection plate 2 to rotate around the axis of the transmission shaft 202, thereby adjusting the deflection angle of the patient's head, exposing one side of the mandible, and facilitating surgical operations;

[0030] In this embodiment, the base sleeve 101 is a rectangular structure, and a stop groove matching the base sleeve 101 of the rectangular structure is provided in the base 1. The base sleeve 101 slides in the stop groove and the rotation of the base sleeve 101 is limited by the stop groove.

[0031] Embodiment 2:

[0032] See also Figure 1-6 According to Embodiment 1, the rear end of the pillow seat 3 is connected to the rear end rotation shaft of the deflection plate 2, and a deflection sleeve 201 is slidably arranged on the deflection plate 2, and the deflection sleeve 201 is driven to slide by rotating the one-way screw 29 installed on the deflection plate 2, thereby controlling the rotation of the pillow seat 3;

[0033] In this embodiment, the deflection sleeve 201 is slidably mounted on the front end of the deflection plate 2, and the deflection sleeve 201 is threadedly sleeved on the one-way screw rod 29. A push rod 303 is arranged below the front end of the pillow seat 3. One end of the push rod 303 is rotatably connected to the pillow seat 3, and the other end is rotatably connected to the deflection sleeve 201. There is a certain angle between the push rod 303 and the deflection plate 2, and the angle is between 15-70°. By rotating the one-way screw rod 29 to drive the deflection sleeve 201 to slide, the push rod 303 is driven to rotate to lift the front end of the pillow seat 3, thereby adjusting the angle between the pillow seat 3 and the deflection plate 2, so that the patient can keep the head slightly tilted back.

[0034] In this embodiment, the deflection sleeve 201 is a rectangular parallelepiped structure, and a stop groove cooperating with the deflection sleeve 201 of the rectangular parallelepiped structure is provided in the pillow seat 3. The deflection sleeve 201 slides in the stop groove and the rotation of the deflection sleeve 201 is limited by the stop groove.

[0035] Embodiment 3:

[0036] See also Figure 1-6 According to Embodiment 1-2, the two sides of the rear end of the pillow seat 3 are slidably provided with limit plates 6, and a bidirectional screw rod 7 is rotatably installed in the pillow seat 3 to control the limit plates 6 on both sides to slide toward or away from each other on the pillow seat 3;

[0037] In this embodiment, a pillow seat slide groove 301 is provided at the rear end of the pillow seat 3, and the bidirectional screw rod 7 is rotatably installed in the pillow seat slide groove 301. The limiting plates 6 on both sides of the pillow seat 3 are respectively threadedly connected to the two ends of the bidirectional screw rod 7. By rotating the bidirectional screw rod 7, the limiting plates 6 on both sides are driven to slide toward each other along the pillow seat slide groove 301, thereby clamping and limiting the patient's head.

[0038] Embodiment 4:

[0039] See also Figure 1-6 According to embodiments 1-3, the retainer 5 is detachably mounted on the pillow seat 3, and the retainer 5 is movably connected to the pillow seat 3 through a movable arm 4. The retainer 5 includes a T-shaped seat 501, a two-way screw rod 502, and a retaining rod 503 slidably mounted on both sides of the T-shaped seat 501. The retaining rod 503 is a telescopic structure, and a bolt is arranged on the retaining rod 503 to limit the telescopic movement of the retaining rod 503. A plurality of fixing holes 5031 are provided on the extended end of the retaining rod 503. The upper part of the extended end of the retaining rod 503 on one side of the T-shaped seat 501 is an arc-shaped structure that fits the position of the mandibular condyle. The two-way screw rod 502 is rotatably mounted in the T-shaped seat 501, and the two-way screw rod 502 is rotated to drive the retaining rods 503 on both sides of the T-shaped seat 501 to slide toward or away from each other;

[0040] In this embodiment, sliding grooves 5011 are provided on both sides of the crossbar of the T-shaped seat 501, the bidirectional screw rod 502 is rotatably installed in the sliding groove 5011, and the lower end of the retaining rod 503 is threadedly connected with the bidirectional screw rod 502, and the retaining rods 503 on both sides of the crossbar of the T-shaped seat 501 are driven to move toward or away from each other by rotating the bidirectional screw rod 502;

[0041] In this embodiment, the retainer 5 includes a T-shaped seat 501 detachably connected to the mounting tube 405 of the movable arm 4, and a retractable retaining rod 503 is slidably arranged on both sides of the T-shaped seat 501. The two-way screw rod 502 in the T-shaped seat 501 is rotated to drive the retaining rods 503 on both sides to move towards each other and tightly against the mandible. The arc structure of the protruding end of the retaining rod 503 on one side can well fit the position of the mandibular condyle, and the protruding end of the retaining rod 503 on the other side is tightly against the front end of the mandible. A fixing nail is nailed into the fixing hole 5031 on the retaining rod 503 to fix the retaining rod 503 to the mandible. The position of the mandibular condyle is prevented from changing when the mandibular bone block is removed. The retaining rod 503 can adapt to the mandibular shape of people of different body shapes through the telescopic and sliding of the retaining rod 503, and the mandible is better fixed, effectively avoiding the change of the position of the condyle after the mandible is cut off.

[0042] Embodiment 5:

[0043] See also Figure 1-6 According to embodiments 1-4, the movable arm 4 includes a slider 401, a telescopic vertical rod 402, a telescopic horizontal rod 403 and a mounting tube 405. The slider 401 slides in the pillow seat slide groove 2 302 opened on the side of the pillow seat 3, and a bolt is set on the slider 401 to limit the sliding of the slider 401. The lower end of the telescopic vertical rod 402 is fixedly connected to the slider 401, and the upper end is fixedly connected to the tail end of the telescopic horizontal rod 403. A ball head mechanism 404 is set at the front end of the telescopic horizontal rod 403. The ball head mechanism 404 includes a ball core and a ball head mechanism connected to the telescopic horizontal rod 403. The shell is fixedly connected, the ball core is movably installed inside the shell, and bolts are set on the shell to limit the movement of the ball core. A notch is set on the shell, and the mounting tube 405 passes through the ball core from the notch of the shell and is fixedly connected to the ball core. The retainer 5 is inserted into the mounting tube 405 through the vertical rod of the T-shaped seat 501, and is detachably connected to the mounting tube 405. Bolts are set on the outer wall of the mounting tube 405 to fix the vertical rod of the T-shaped seat 501 in the mounting tube 405. The telescopic vertical rod 402 and the telescopic horizontal rod 403 are both limited by bolts to limit telescopic rotation;

[0044] In this embodiment, the movable arm 4 is slidably installed on one side of the pillow seat 3, and the installation tube 405 is movably connected to the telescopic cross bar 403 of the movable arm 4 through the ball head mechanism 404. During the operation, the retainer 5 is fixedly installed in the installation tube 405, the movable arm 4 is slid to the patient's mandibular position, and the position of the retainer 5 is adjusted to align with the mandible by telescopic adjustment of the telescopic vertical rod 402 and the telescopic cross bar 403 of the movable arm 4. The retainer 5 can be fixed by the movable arm 4 without hand support, freeing up manpower, facilitating the fixation of the retainer 5 to the mandible, and facilitating the subsequent implantation of bones to repair and reconstruct the mandible.

[0045] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A device for assisting mandibular repair and reconstruction, comprising a head fixation device and a retainer, It is characterized in that The head fixing device comprises a base, a deflection plate and a pillow seat, wherein the middle portion of the deflection plate is connected to the base rotating shaft, and a base sleeve is slidably arranged on the base, and the base sleeve is driven to slide by rotating a one-way screw rod arranged on the base, thereby driving the deflection plate to rotate; The rear end of the pillow seat is connected to the rear end rotating shaft of the deflection plate, and a deflection sleeve is slidably arranged on the deflection plate. The deflection sleeve is driven to slide by rotating a one-way screw rod 2 installed on the deflection plate, thereby controlling the rotation of the pillow seat; Limiting plates are slidably provided on both sides of the rear end of the pillow seat, and a bidirectional screw rod is rotatably installed in the pillow seat to control the limiting plates on both sides to slide towards or away from each other on the pillow seat; The retainer is detachably mounted on the pillow seat, and the retainer and the pillow seat are movably connected via a movable arm. The retainer comprises a T-shaped seat, two bidirectional screw rods, and retaining rods slidably mounted on both sides of the T-shaped seat. The retaining rods are telescopic structures, and a plurality of fixing holes are provided on the extended ends of the retaining rods. The upper portion of the extended end of the retaining rod on one side of the T-shaped seat is an arc-shaped structure that fits the position of the condyle of the mandibular bone. The two bidirectional screw rods are rotatably mounted in the T-shaped seat, and the retaining rods on both sides of the T-shaped seat are driven to slide toward or away from each other by rotating the two bidirectional screw rods.

2. A device for assisting mandibular repair and reconstruction according to claim 1, It is characterized in that A groove is provided on the base, the deflection plate is located above the groove, a transmission shaft is fixedly arranged at the lower middle part of the deflection plate, the transmission shaft is rotatably connected to the bottom of the groove, a gear is fixedly arranged at the tail end of the transmission shaft, the base sleeve is slidably installed inside the rear end of the base, and a serrated structure is provided on the base sleeve to mesh with the gear on the transmission shaft, the one-way screw rod 1 is rotatably installed inside the rear end of the base, the base sleeve is threadedly sleeved on the one-way screw rod 1, and the base sleeve is driven to slide by rotating the one-way screw rod 1, thereby driving the gear to rotate, so that the deflection plate and the transmission shaft rotate around the axis of the transmission shaft.

3. A device for assisting mandibular repair and reconstruction according to claim 1, It is characterized in that The deflection sleeve is slidably installed at the front end of the deflection plate, and the deflection sleeve is threadedly sleeved on the second one-way screw rod. A push rod is arranged below the front end of the pillow seat. One end of the push rod is rotatably connected to the pillow seat, and the other end is rotatably connected to the deflection sleeve. There is a certain angle between the push rod and the deflection plate. The deflection sleeve is driven to slide by rotating the second one-way screw rod, and the push rod is driven to rotate to lift the front end of the pillow seat, thereby adjusting the angle between the pillow seat and the deflection plate.

4. A device for assisting mandibular repair and reconstruction according to claim 1, It is characterized in that A pillow seat slide groove 1 is provided at the rear end of the pillow seat, and the bidirectional screw rod 1 is rotatably installed in the pillow seat slide groove 1. The limit plates on both sides of the pillow seat are respectively threadedly connected to the two ends of the bidirectional screw rod 1, and the bidirectional screw rod 1 is rotated to drive the limit plates on both sides to slide toward or away from each other along the pillow seat slide groove 1.

5. A device for assisting mandibular repair and reconstruction according to claim 1, It is characterized in that Sliding grooves are provided on both sides of the cross bar of the T-shaped seat, and the two-way screw rod is rotatably installed in the sliding groove. The lower end of the retaining rod is threadedly connected with the two-way screw rod. The two-way screw rod is rotated to drive the retaining rods on both sides of the cross bar of the T-shaped seat to move toward or away from each other.

6. A device for assisting mandibular repair and reconstruction according to claim 1, It is characterized in that The movable arm includes a slider, a telescopic vertical rod, a telescopic cross rod and a mounting tube. The slider slides in a pillow seat slide groove 2 opened on the side of the pillow seat. The lower end of the telescopic vertical rod is fixedly connected to the slider, and the upper end is fixedly connected to the tail end of the telescopic cross rod. A ball head mechanism is arranged at the front end of the telescopic cross rod. The ball head mechanism includes a ball core and an outer shell fixedly connected to the telescopic cross rod. The ball core is movably installed inside the outer shell. A notch is opened on the outer shell. The mounting tube passes through the ball core from the notch of the outer shell and is fixedly connected to the ball core. The retainer is inserted into the mounting tube through the vertical rod of the T-shaped seat and is detachably connected to the mounting tube.

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