Reciprocating feeding unit, orthopedic nail placement mechanism, device and orthopedic nail placement method

Abstract

The present invention provides a reciprocating feeding unit, an orthopedic nail placement mechanism, an apparatus and an orthopedic nail placement method, comprising a fixing clamp structure, a movable arm structure and an orthopedic nail placement mechanism, the orthopedic nail placement mechanism comprising a slide mechanism, a telescopic mechanism, a probe swing mechanism and a reciprocating feeding unit, the reciprocating feeding unit comprising a driving mechanism, a first roller, a second roller and a clamping mechanism. The reciprocating feeding unit, the orthopedic nail placement mechanism, the apparatus and the orthopedic nail placement method of the present invention solve the technical problem that doctors in the prior art manually punch holes on the pedicles using hand awls and Kirschner wires based on their experience, thereby causing various uncertainties in the process of pedicle screw placement.

Description

Technical Field

[0001] The present invention belongs to the technical field of medical devices, and in particular relates to a reciprocating feeding unit, an orthopedic nail placement mechanism, a device and an orthopedic nail placement method. Background Art

[0002] Congenital scoliosis is a serious congenital deformity in children. Congenital scoliosis is divided into three types: malformation of the vertebrae, malsegmentation, and mixed types. The deformity of the vertebrae causes the spine to bulge and rotate to the side or front and back, and gradually worsens with the growth of the spine. In addition to body deformities, the deformity of the spine affects the child's cardiopulmonary function, organ function, and spinal cord function, seriously hindering the child's growth and development. Congenital scoliosis is often accompanied by deformities of other systems, such as spinal canal and spinal cord abnormalities, urinary system malformations, congenital heart disease, rib fusion or absence, etc., which aggravates the degree of spinal and thoracic dysplasia in children, leading to cardiopulmonary development disorders, abdominal organ development disorders, and spinal cord dysfunction.

[0003] The treatment of congenital scoliosis is divided into two categories: conservative treatment and surgical treatment. Conservative treatment methods, such as Mehta series plaster correction, can sometimes delay the aggravation of spinal deformity. For those with rapidly progressing deformities, surgical treatment is the main treatment. Common surgical procedures for congenital scoliosis in clinical practice include hemivertebral resection, growth rod distraction, spinal osteotomy correction fixation fusion, etc. The key points and difficulties of different surgical methods are the placement of pedicle screws. The traditional manual screw placement method is that the surgeon selects the needle point and direction based on preoperative and intraoperative imaging data, anatomical position, and experience, and inserts the screw from the pedicle to the front vertebral body, and combines intraoperative imaging data to evaluate the satisfaction of screw placement; throughout the process, whether it is the surgeon's judgment, the child's body position change, or even the surgeon's technique, none of them can be missing. Abnormalities in any link can result in poor fixation and unsatisfactory correction effects, or even damage to important peripheral blood vessels and nerves, which will bring serious consequences to the child. It can be seen that the manual screw placement method that relies too much on experience and touch has unavoidable disadvantages. In recent years, the method of intelligent robot-assisted screw placement has gradually entered people's field of vision. Since robots can overcome the physiological limits of humans and have the advantages of accuracy, stability, controllability, and repeatability, intelligent robots have become a hot trend in the development of orthopedics.

[0004] Foreign orthopedic artificial intelligence can be traced back to the artificial hip replacement robot developed in the United States in 1988; the world's first orthopedic surgical robot is the RoboDoc robot developed by Integrated Surgical Systems; the more mature spinal robots currently include Spine Assist / Renaissance developed by Israel, ROSASpine developed by France, and CORA, SOINEBOT, VectorBot / Kinemedic / LWR, etc., which are still under development and improvement; clinical applications are relatively mature and extensive. my country's research on orthopedic intelligent robots started relatively late and is still in its infancy overall. The main research and development units include Beijing University of Aeronautics and Astronautics, Harbin Institute of Technology, etc.; the main users include Beijing Jishuitan Hospital, the General Hospital of the Chinese People's Liberation Army, and the Xinqiao Hospital of the Third Military Medical University, etc.; among them, Beijing Children's Hospital is the first children's specialty hospital in China to use orthopedic robot-assisted surgery. The Tianji orthopedic robot developed by Beijing Jishuitan Hospital represents the top level in China in this field, and has broken through the limitations of cervical spine surgery and reached the international leading level.

[0005] A number of research analyses at home and abroad have shown that compared with traditional manual screw placement, the accuracy, success rate, satisfaction and other aspects of screw placement are significantly improved by intelligent robot-assisted screw placement in spinal surgery, and the postoperative complications caused by screw placement are also reduced accordingly; however, due to the particularity of congenital scoliosis in children - vertebral deformities are diverse and complex, individual differences in deformities are obvious, the age is young, and the vertebral body and pedicle development are poor - the probability of intraoperative screw placement failure is still relatively high.

[0006] In the field of spinal surgery, X-ray monitoring of pedicle screw implantation technology often requires C-arm X-ray fluoroscopy to monitor whether the screw is correctly placed. However, due to the inclination angle of the pedicle central axis in the horizontal and sagittal planes, and the cylindrical vertebral body, it is difficult to monitor the position and depth of the screw by relying solely on ordinary X-ray imaging. The position of the pedicle screws inserted in this way has a high false positive rate and false negative rate, and X-ray fluoroscopy cannot achieve continuous monitoring, and the radiation damage is relatively high.

[0007] At present, in pedicle screw placement surgery, most doctors can only perform the surgery based on years of experience. Generally, they always use a hand awl to ensure a certain sinking force. First, the bone cortex at the screw entry point is broken, and then the blunt head of a 2mm Kirschner wire is used to slowly push down the cancellous bone in the pedicle with both hands. You can hear a unique "squeaking" sound and feel a special touch until the anterior cortex of the vertebral body. You can hear a harder snapping sound, remove the Kirschner wire, and measure the length of the pedicle screw. This method of inserting the pedicle screw can generally ensure that the screw is located in the center of the pedicle. The "squeaking" sound and special feel of this empirical method are not uniformly standardized, and there will be differences between each doctor, so this leads to various uncertainties in the process of pedicle screw placement, which poses a great safety hazard to patients.

[0008] Near-infrared spectroscopy is used to monitor the placement of pedicle screws. Although it has a certain effect on improving the accuracy of screw placement, it currently does not have a more effective feature recognition factor, and cannot directly reflect the changes in feature recognition factors. It also lacks functions such as deviation correction and early warning. Therefore, near-infrared spectroscopy technology needs to be further optimized and improved in the monitoring of pedicle screw placement before it can be better used in clinical surgery.

[0009] In the existing pedicle screw fixation technology, computer-assisted navigation technology is currently the most accurate monitoring method, but it requires the use of expensive equipment and special instruments, and the operation is relatively complicated. Summary of the invention

[0010] In view of this, the present invention aims to provide a reciprocating feeding unit, an orthopedic screw placement mechanism, a device and an orthopedic screw placement method, which solves the technical problem in the prior art that doctors use hand awls and Kirschner wires to manually drill holes on the pedicles based on their experience, thereby causing various uncertainties in the process of pedicle screw placement;

[0011] This further solves the technical problem that the pedicle screw internal fixation in the prior art requires expensive equipment and special instruments, and the operation is relatively complicated;

[0012] It also solves the technical problems of traditional manual nail placement, which leads to poor fixation effect, unsatisfactory correction effect, and damage to important surrounding blood vessels and nerves.

[0013] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0014] A reciprocating feeding unit comprises a driving mechanism, a first roller, a second roller and a clamping mechanism;

[0015] The driving mechanism is used to drive the first roller and the second roller to rotate, the clamping mechanism is used to achieve clamping between the first roller and the second roller, and the first roller and the second roller are used to drive a probe or a screwdriver head that can cooperate with a pedicle screw to perform linear reciprocating motion.

[0016] Furthermore, the driving mechanism includes a third motor and a fourth motor, the second roller is arranged at the output end of the third motor, and the first roller is arranged at the output end of the fourth motor.

[0017] Furthermore, the first roller and the second roller are both provided with an annular groove capable of cooperating with the probe.

[0018] Furthermore, the clamping mechanism includes a guide rail structure, a fifth motor, a second lead screw, a first movable clamp, a second movable clamp, a first roller bracket and a second roller bracket, the first roller bracket and the second roller bracket are both slidably arranged on the guide rail structure, the second roller is rotatably arranged on the second roller bracket, the first roller is rotatably arranged on the first roller bracket, the first roller bracket and the second roller bracket are arranged between the first movable clamp and the second movable clamp, the fifth motor is used to drive the second lead screw to rotate, and when the second lead screw rotates, the first movable clamp and the second movable clamp clamp the first roller bracket and the second roller bracket.

[0019] Furthermore, a first pressure sensor is provided at a contact position between the first movable clamp and the second roller bracket, and a second pressure sensor is provided at a contact position between the second movable clamp and the first roller bracket.

[0020] Furthermore, the first movable clamp and the second movable clamp are both engaged with the second lead screw via self-locking trapezoidal threads.

[0021] Furthermore, the guide rail structure includes a first guide rail and a second guide rail, the first roller bracket is slidably connected to the first guide rail and the second guide rail, and the second roller bracket is slidably connected to the first guide rail and the second guide rail.

[0022] An orthopedic nail placement mechanism, comprising a slide mechanism, a telescopic mechanism, a probe swing mechanism and the above-mentioned reciprocating feeding unit;

[0023] The slide mechanism includes a slide rail and a slide, the slide is slidably connected to the slide rail, the telescopic mechanism is used to achieve sliding between the slide and the slide rail, the reciprocating feed unit is arranged on the slide through a torsion mechanism, and the probe swing mechanism is used to achieve rotation of the reciprocating feed unit.

[0024] Furthermore, the twisting mechanism includes a first support frame and a twisting disk, the twisting disk is rotatably connected to the first support frame via a first bearing, the clamping mechanism is arranged on the twisting disk, the output end of the probe swing mechanism is fixedly connected to the twisting disk, and the probe swing mechanism is arranged on the slide.

[0025] Furthermore, the probe swinging mechanism is a first motor.

[0026] Furthermore, the telescopic mechanism includes a second motor, a first lead screw, a second support frame and a third support frame, the third support frame is arranged on the slide rail, the second motor and the second support frame are both arranged on the slide, the first lead screw is rotatably connected to the second support frame through a second bearing, the third support frame is provided with a threaded hole, the first lead screw is connected to the threaded hole, and the second motor is used to drive the first lead screw to rotate.

[0027] Furthermore, the output shaft of the second motor is connected to the first lead screw via a first torque sensor, and the output end of the probe swing mechanism is connected to the torsion disk via a second torque sensor.

[0028] Furthermore, the thread of the first screw and the threaded hole are both self-locking trapezoidal threads.

[0029] Furthermore, the first lead screw, the probe swing mechanism, the second motor and the torsion disk are all located on the same axial line, and the axial positions of the output shaft of the probe swing mechanism, the output shaft of the second motor, the first lead screw and the torsion disk are all provided with through holes through which the probe can pass, and the through hole of the torsion disk is located between the first roller and the second roller.

[0030] Furthermore, the orthopedic nail placement mechanism also includes a first protective cover and a second protective cover, the first protective cover is used to cover the second motor and the moving stroke of the second motor, and the second protective cover is used to cover the probe swing mechanism and the reciprocating feeding unit.

[0031] Furthermore, the orthopedic nail placement mechanism also includes a guide head and a guide conical tube for guiding the probe, the guide head is arranged at the end of the second protective cover close to the reciprocating feeding unit, and the guide conical tube is detachably connected to the guide head.

[0032] Furthermore, the orthopedic nail placement mechanism also includes a ruler for measuring the travel distance of the probe, and the ruler is arranged at the outer end of the first screw.

[0033] Furthermore, a circular plate is provided at the end of the ruler away from the first screw, the circular plate is provided with a circular hole that can pass through the probe, the ruler is provided with a hollow groove that can cooperate with the probe, the circular hole is connected to the hollow groove, and the ruler is provided with two scale lines, which are symmetrically arranged on both sides of the hollow groove.

[0034] An orthopedic nail placement device comprises a fixing clamp structure, a movable arm structure and the above-mentioned orthopedic nail placement mechanism;

[0035] The fixed frame structure is connected to the slide rail through the movable arm structure.

[0036] Furthermore, the fixing clamp structure includes a fixing clamp and four hand-tightening bolts. The cross-section of the fixing clamp is C-shaped. The four hand-tightening bolts are all arranged at the bottom of the fixing clamp. A non-slip rubber pad is provided on the top of each hand-tightening bolt. The fixing clamp is connected to the movable arm structure.

[0037] An orthopedic nail placement method comprises the following steps:

[0038] Step 1: Select a pointed probe from the probe category, set the torque threshold of the first torque sensor and the torque threshold of the second torque sensor to the torque threshold that the pointed probe can pass through the skin and flesh, set the pressure thresholds of the first pressure sensor and the second pressure sensor to the pressure threshold that can clamp the pointed probe, install the fixing clamp structure next to the operating table, adjust the position of the orthopedic nail placement mechanism by adjusting the movable arm structure, insert the pointed probe into the orthopedic nail placement mechanism and make the bottom of the pointed probe flush with the top of the ruler, and the tip of the pointed probe is exposed from the guide cone tube;

[0039] Step 2: Adjust the position of the orthopedic nail placement mechanism again so that the pointed probe contacts the skin to be pierced;

[0040] Step 3: The pointed probe is slowly twisted and pressed into the deep flesh through the orthopedic nail placement mechanism. When the torque threshold of the first torque sensor and the torque threshold of the second torque sensor reach the set torque threshold, the first motor and the second motor stop automatically. After the first motor and the second motor stop, X-ray fluoroscopy is used to confirm whether the pointed probe has hit the pedicle cortical bone drilling position; if the position of the pointed probe is inconsistent, the direction of movement of the pointed probe is adjusted by adjusting the position of the movable arm structure and the orthopedic nail placement mechanism; Step 4: After confirming that there is no abnormality in step 3, the torque threshold of the first torque sensor and the torque threshold of the second torque sensor are both set to the torque threshold that the pointed probe can be pressed into the deep cortical bone, and the pressure thresholds of the first pressure sensor and the second pressure sensor are set to the pressure threshold that can clamp the pointed probe, and the orthopedic nail placement mechanism slowly twists and presses the pointed probe into the deep cortical bone until it stops automatically;

[0041] Step 5: After confirming that there is no abnormality in step 4, close the orthopedic nail placement mechanism and replace the pointed probe with a dotted probe. At the same time, ensure that the position displayed on the scale after the dotted probe is inserted is consistent with the scale position before the pointed probe was replaced. The torque threshold of the first torque sensor and the torque threshold of the second torque sensor are both set to the torque threshold for the dotted probe to pass through the cancellous bone. The pressure thresholds of the first pressure sensor and the second pressure sensor are both set to the pressure thresholds that can clamp the dotted probe. Set the second motor to the maximum insertion size value of the dotted probe. The orthopedic nail placement mechanism slowly twists and presses the dotted probe deep into the cancellous bone until it stops.

[0042] Further, after the step 5 is completed, the following steps are also included:

[0043] Step 6: Do not move the inserted probe, adjust the movable arm structure and move the orthopedic nail placement mechanism away from the probe;

[0044] Step 7: Replace the guide head and the guide conical tube of the orthopedic screw placement mechanism with a guide head and a guide conical tube with an inner diameter suitable for the passage of the pedicle screw;

[0045] Step 8: Use a scalpel to expand the cuts on both sides of the probe for a certain distance, adjust the movable arm structure to insert the blunt-head probe into the orthopedic nail placement mechanism until the guide cone tube hits the expanded cut of the scalpel;

[0046] Step 9: Setting the torque threshold of the first torque sensor so that the pressure thresholds of the first pressure sensor and the second pressure sensor are both 0, the orthopedic screw placement mechanism presses in the guide tapered tube suitable for the pedicle screw to pass through, and when the torque threshold of the first torque sensor reaches the set torque threshold, the second motor automatically stops;

[0047] Step 10: Adjust the movable arm structure, keep the position of the guide cone tube unchanged, and disassemble and separate the guide cone tube from the guide head;

[0048] Step 11: Hold the hollow long rod pedicle screwdriver head between the first roller and the second roller, and install the pedicle self-tapping screw on the hollow long rod pedicle screwdriver head; adjust the movable arm structure, insert the orthopedic screw placement mechanism for installing the pedicle self-tapping screw along the head probe into the guide tapered tube suitable for the pedicle to pass through, and directly contact the pedicle;

[0049] Step 12: Set the torque threshold of the first torque sensor and the torque threshold of the second torque sensor so that the pressure thresholds of the first pressure sensor and the second pressure sensor are both pressure thresholds that can clamp the hollow long rod pedicle screwdriver head, and adjust the movement mode of the first motor from twisting to rotation; the orthopedic screw placement mechanism screws the pedicle self-tapping screw into the pedicle, and when the torque threshold of the first torque sensor and the torque threshold of the second torque sensor reach the set torque threshold, the first motor and the second motor stop automatically.

[0050] Compared with the prior art, the reciprocating feeding unit, orthopedic nail placement mechanism, device and orthopedic nail placement method of the present invention have the following advantages:

[0051] The reciprocating feeding unit, orthopedic nail placement mechanism, device and orthopedic nail placement method of the present invention can be used in combination with an orthopedic intelligent robot, and the orthopedic nail placement mechanism can be used as an independent medical device. The orthopedic nail placement device has significant progress in improving the safety of children's congenital scoliosis correction surgery, reducing the pain of children and the incidence of surgical complications, reducing medical costs, and promoting the healthy development of doctor-patient relationship.

[0052] The orthopedic screw placement device can sense the screw placement position in real time through mechanical conduction to avoid the screw from penetrating the cortical bone surface of the anterior vertebral body, ensure the normal movement of the screw in the pedicle, thereby avoiding the occurrence of complications and greatly improving the safety of pedicle screw placement. The orthopedic screw placement device can be used in combination with the orthopedic intelligent robot to become the last "safety lock" in the screw placement process; the orthopedic screw placement mechanism can be used as an independent medical device to replace the traditional screw placement tool as an auxiliary device, greatly improving the safety and accuracy of the clinician's manual screw placement; the former, as a component of the orthopedic intelligent robot, improves and enriches the function of the robot; the latter, as a separate surgical instrument, is not limited to the huge space occupation and high cost of the robot. As a supplementary means for the surgeon, it can give full play to the experience and skills of the clinician. Regardless of the form, it provides safety guarantee for the successful operation of children with congenital scoliosis, reduces the incidence of intraoperative and postoperative complications, and reasonably saves my country's medical resources on the premise of meeting the needs of children, and also promotes the healthy development of the doctor-patient relationship. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0054] Figure 1 This is a schematic diagram of an orthopedic nail placement device according to an embodiment of the present invention;

[0055] Figure 2 This is a schematic diagram of the working structure of an orthopedic nail placement device according to an embodiment of the present invention;

[0056] Figure 3 This is a schematic structural diagram of an orthopedic nail placement mechanism according to an embodiment of the present invention;

[0057] Figure 4 This is a schematic diagram of the combined structure of a reciprocating feeding unit and a twisting mechanism in an orthopedic nail placement mechanism according to an embodiment of the present invention;

[0058] Figure 5 A schematic diagram of the structure of a reciprocating feeding unit according to an embodiment of the present invention;

[0059] Figure 6 A schematic diagram of the structure of a head-dotted probe in an orthopedic nail placement method according to an embodiment of the present invention;

[0060] Figure 7 A schematic diagram of the structure of a pointed probe in an orthopedic nail placement method according to an embodiment of the present invention;

[0061] Figure 8 The figure is a schematic diagram of the electrical control when an orthopedic nail placement device according to an embodiment of the present invention is in use.

[0062] Description of reference numerals:

[0063] 1. Fixed clamp; 2. Movable arm; 4. Ruler; 5. First protective cover; 6. Second protective cover; 7. Guide cone tube; 8. Probe; 9. Guide head; 10. First support frame; 11. First motor; 12. Second support frame; 13. Second motor; 14. First lead screw; 15. Third support frame; 16. Slide rail; 17. Slide table; 18. Twisting disk; 19. Third motor; 20. Fourth motor; 21. Fifth motor; 22. First movable clamp; 23. First guide rail; 24. Second guide rail; 25. Second movable clamp; 26. Second lead screw; 27. First roller; 28. Second roller; 29. ​​First roller bracket; 30. Second roller bracket. DETAILED DESCRIPTION

[0064] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0065] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0066] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0067] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0068] A reciprocating feed unit, such as Figure 5 As shown, it includes a driving mechanism, a first roller 27, a second roller 28 and a clamping mechanism;

[0069] The driving mechanism is used to drive the first roller 27 and the second roller 28 to rotate, and the clamping mechanism is used to achieve clamping between the first roller 27 and the second roller 28. The first roller 27 and the second roller 28 are used to drive the probe 8 or the screwdriver head that can cooperate with the pedicle screw to perform linear reciprocating motion. In this embodiment, the driving mechanism includes a third motor 19 and a fourth motor 20, the second roller 28 is arranged at the output end of the third motor 19, and the first roller 27 is arranged at the output end of the fourth motor 20. The third motor 19 and the fourth motor 20 rotate in opposite directions and ensure start-stop synchronization. In this embodiment, the first roller 27 and the second roller 28 are both provided with an annular groove that can cooperate with the probe 8. The axis center lines of the first roller 27 and the second roller 28 are parallel. The parallel state is conducive to tightening the probe 8 and also prevents the first roller 27 and the second roller 28 from interfering with the feeding.

[0070] The clamping mechanism includes a guide rail structure, a fifth motor 21, a second lead screw 26, a first movable clamp 22, a second movable clamp 25, a first roller bracket 29 and a second roller bracket 30. The first roller bracket 29 and the second roller bracket 30 are both slidably arranged on the guide rail structure. The second roller 28 is rotatably arranged on the second roller bracket 30. The first roller 27 is rotatably arranged on the first roller bracket 29. The first roller bracket 29 and the second roller bracket 30 are arranged between the first movable clamp 22 and the second movable clamp 25. The fifth motor 21 is used to drive the second lead screw 26 to rotate. When the second lead screw 26 rotates, the first movable clamp 22 and the second movable clamp 25 clamp the first roller bracket 29 and the second roller bracket 30. In this embodiment, the first movable clamp 22 and the second movable clamp 25 are both engaged with the second lead screw 26 through a self-locking trapezoidal thread.

[0071] A first pressure sensor is provided at a contact position between the first movable clamp 22 and the second roller bracket 30 , and a second pressure sensor is provided at a contact position between the second movable clamp 25 and the first roller bracket 29 .

[0072] In this embodiment, the guide rail structure includes a first guide rail 23 and a second guide rail 24 , a first roller bracket 29 is slidably connected to the first guide rail 23 and the second guide rail 24 , and a second roller bracket 30 is slidably connected to the first guide rail 23 and the second guide rail 24 .

[0073] An orthopedic nail placement mechanism, such as Figure 3-4 As shown, it includes a slide mechanism, a telescopic mechanism, a probe swing mechanism and the above-mentioned reciprocating feeding unit;

[0074] The slide mechanism includes a slide rail 16 and a slide 17. The slide 17 is slidably connected to the slide rail 16. The telescopic mechanism is used to realize the sliding between the slide 17 and the slide rail 16. The reciprocating feed unit is arranged on the slide 17 through a twisting mechanism. The probe swing mechanism is used to realize the rotation of the reciprocating feed unit.

[0075] The twisting mechanism includes a first support frame 10 and a twisting disk 18, the twisting disk 18 is rotatably connected to the first support frame 10 through a first bearing, the clamping mechanism is arranged on the twisting disk 18, the output end of the probe swinging mechanism is welded to the twisting disk 18, the fifth motor 21 is fixed on the twisting disk 18, and the probe swinging mechanism is arranged on the slide 17. In this embodiment, the probe swinging mechanism is the first motor 11, and the feedback of the first pressure sensor and the second pressure sensor can automatically adjust the clamping force between the first roller 27 and the second roller 28 in real time. At the same time, the first roller 27 and the second roller 28 are located in the center of the twisting disk 18, so that the first motor 11 can drive the first roller 27 and the second roller 28 to clamp the probe 8 through the twisting disk 18 for reciprocating twisting, thereby reducing the occurrence of blockage and promoting smoother movement of the probe. The clamping force of the first roller 27 and the second roller 28 on the probe 8 is adjusted by a preset pressure threshold. When the resistance is too large, the probe may slip between the first roller 27 and the second roller 28 instead of following the twisting of the twisting disk 18 and the movement of the second motor 13 along the slide rail. This adds a protective measure to avoid medical accidents.

[0076] A bearing hole is provided at the center of the first support frame 10, and the first bearing is installed in the bearing hole. The inner ring of the first bearing is connected to the torsion disk 18 and is coaxial with the first motor 11 and the second motor 13. The first bearing and the second bearing are both cylindrical roller bearings, and a spacer is installed between the rollers of the bearings to prevent the rollers from tilting or the rollers from rubbing against each other, thereby effectively preventing the increase of the rotation torque. The torsion disk 18 and the bearing hole are separable, which is convenient for installation and disassembly. The outer ring of the torsion disk 18 adopts an NJ-type bearing design, and there are ribs on both sides of the outer ring that can cooperate with the first bearing. The torsion disk 18 is provided with a rib on the side close to the first motor 11. When the resistance of the probe 8 is too large, the torsion disk 18 can be driven by the first roller 27 and the second roller 28 to move in a buffering manner toward the direction of the first motor 11, thereby combining the sliding effect of the probe 8 between the first roller 27 and the second roller 28 under large resistance, and under the dual effect, the pedicle is protected.

[0077] The telescopic mechanism includes a second motor 13, a first lead screw 14, a second support frame 12 and a third support frame 15. The third support frame 15 is arranged on a slide rail 16. The second motor 13 and the second support frame 12 are both arranged on a slide 17. The first lead screw 14 is rotatably connected to the second support frame 12 through a second bearing. The third support frame 15 is provided with a threaded hole, and the first lead screw 14 is connected to the threaded hole. The second motor 13 is used to drive the first lead screw 14 to rotate. In this embodiment, the thread and the threaded hole of the first lead screw 14 are both self-locking trapezoidal threads.

[0078] In this embodiment, the internal output shaft of the second motor 13 is connected to the first torque sensor and then to the first lead screw; the internal output shaft of the first motor 11 is connected to the second torque sensor and then to the torsion disk 18; the torque sensors provided inside the first motor 11 and the second motor 13 need to have hollow shafts, and the first torque sensor and the second torque sensor are both hollow disk-type dynamic torque sensors. The second torque sensor inside the first motor 11 uses the torque transmitted by the torsion disk 18 to monitor the torque change caused by the resistance change of the probe 8 during its movement in real time, thereby reflecting the tissue in which the probe 8 moves through the torque change; and then the first torque sensor inside the second motor 13 is connected to the resistance transmitted by the first motor 11 through the slide 17, which is reflected in the first torque sensor inside the second motor. The two torque sensors provided inside the first motor 11 and the second motor 13 comprehensively detect the resistance of the probe, which more accurately reflects the tissue in which the probe moves.

[0079] The first lead screw 14, the probe swing mechanism, the second motor 13 and the twisting disk 18 are all located on the same axis. The output shaft of the probe swing mechanism, the output shaft of the second motor 13, the first lead screw 14 and the twisting disk 18 are all provided with a through hole that can pass the probe 8. The through hole of the twisting disk 18 is located between the first roller 27 and the second roller 28. The first motor 11, the second motor 13, the first lead screw 14 and the twisting disk 18 all adopt a coaxial hollow design, which is convenient for clinical physicians to operate, reduces unnecessary operation steps, and performs the operation more efficiently and accurately, thereby improving the quality of the operation and the safety of the patient. The coaxial hollow design further reduces the volume of the device, saves most of the operating space for clinical operators, makes the operation more comfortable, and reduces the pressure of clinical surgeons. At the same time, the small volume design avoids the formation of light-shielding shadows that hinder the smooth progress of the operation. The probe 8, the first motor 11, the second motor 13, the first lead screw 14 and the twisting disk 18 are all located on the same axis, which is more conducive to the transmission monitoring of parameters such as resistance, making the data more accurate, and making the monitoring more sensitive and reliable.

[0080] The orthopedic nail placement mechanism also includes a first protective cover 5 and a second protective cover 6. The first protective cover 5 is used to cover the second motor 13 and the movement stroke of the second motor 13. The second protective cover 6 is used to cover the probe swing mechanism and the reciprocating feed unit. The orthopedic nail placement mechanism also includes a guide head 9 and a guide conical tube 7 for guiding the probe 8. The guide head 9 is arranged at the end of the second protective cover 6 close to the reciprocating feed unit. The guide head 9 is connected to the second protective cover 6 by a thread. The guide conical tube 7 is detachably connected to the guide head 9. The guide head 9 and the guide conical tube 7 are connected in a plug-in manner.

[0081] In this embodiment, the orthopedic nail placement mechanism also includes a scale 4 for measuring the travel distance of the probe 8. The scale 4 is arranged at the outer end of the first screw 14. The end of the scale 4 away from the first screw 14 is provided with a circular plate. The circular plate is provided with a circular hole that can pass through the probe 8. The scale 4 is provided with a hollow groove that can cooperate with the probe 8. The circular hole is connected to the hollow groove, and the hollow groove can accommodate the probe 8 to pass through. Two scale lines are provided on the scale 4, and the two scale lines are symmetrically arranged on both sides of the hollow groove. The minimum spacing between adjacent short lines on a scale line is 1 mm, and the minimum spacing between adjacent long lines is 5 mm. The total length of the scale 4 is 10 cm to 15 cm.

[0082] An orthopedic nail placement device, such as Figure 1-2 As shown, it includes a fixing clamp structure, a movable arm structure and the above-mentioned orthopedic nail placement mechanism;

[0083] like Figure 8 As shown, the first motor 11, the second motor 13, the third motor 19, the fourth motor 20, the fifth motor 21, the first torque sensor, the second torque sensor, the first pressure sensor, and the second pressure sensor are all connected to the control device. In this embodiment, the control device is an MCU STM32F407IGT6 industrial control, hereinafter referred to as MCU.

[0084] The fixed frame structure is connected to the slide rail 16 through a movable arm structure. In this embodiment, the fixed clamp structure includes a fixed clamp 1 and four hand-tightened bolts. The cross-section of the fixed clamp 1 is C-shaped. The four hand-tightened bolts are all arranged at the bottom of the fixed clamp 1. Each hand-tightened bolt is provided with an anti-slip rubber pad on the top. The anti-slip rubber pad has the function of clamping, fixing and anti-slip. The fixed clamp 1 is connected to the movable arm structure. In this embodiment, the movable arm structure includes two movable arms 2. The two movable arms 2 are connected through a universal joint. One movable arm 2 is connected to the top of the fixed clamp 1 through a universal joint, and the other movable arm 2 is connected to the slide rail 16 through a universal joint. The universal joint facilitates the movable arm 2 to change its position in multiple directions.

[0085] The pointed probe is mainly used for drilling holes in the skin and cortical bone of the pedicle of the orthopedic screw placement mechanism in the early stage, and the blunt-head probe is mainly used for detection and drilling inside the pedicle in the later stage.

[0086] An orthopedic nail placement method comprises the following steps:

[0087] Step 1: Select a pointed probe from the probe category 8, set the torque threshold of the first torque sensor and the torque threshold of the second torque sensor to the torque threshold that the pointed probe can pass through the skin and flesh, set the pressure thresholds of the first pressure sensor and the second pressure sensor to the pressure threshold that can clamp the pointed probe, install the fixing clamp structure next to the operating table, adjust the position of the orthopedic nail placement mechanism by adjusting the movable arm structure, insert the pointed probe into the orthopedic nail placement mechanism and make the bottom of the pointed probe flush with the top of the ruler 4, and the tip of the pointed probe is exposed from the guide conical tube 7;

[0088] Step 2: Adjust the position of the orthopedic nail placement mechanism again so that the pointed probe contacts the skin to be pierced;

[0089] Step 3: The first motor 11 drives the pointed probe to repeatedly twist in a forward 90° and reverse 90° manner, and the pointed probe is slowly twisted and pressed deep into the skin and flesh by the second motor 13. When the torque threshold of the first torque sensor and the torque threshold of the second torque sensor reach the set torque threshold, the first motor 11 and the second motor 13 automatically stop. After the first motor 11 and the second motor 13 stop, use X-ray fluoroscopy to confirm whether the pointed probe has hit the pedicle cortical bone drilling position; if the position of the pointed probe is inconsistent, the direction of movement of the pointed probe is adjusted by adjusting the position of the movable arm structure and the orthopedic nail placement mechanism;

[0090] Step 4: After confirming that there is no abnormality in step 3, the torque threshold of the first torque sensor and the torque threshold of the second torque sensor are both set to the torque threshold at which the pointed probe can be pressed deep into the cortical bone, and the pressure thresholds of the first pressure sensor and the second pressure sensor are both set to the pressure threshold at which the pointed probe can be clamped, and the orthopedic nail placement mechanism slowly twists and presses the pointed probe deep into the cortical bone until it stops automatically;

[0091] Step 5: After confirming that there is no abnormality in step 4, close the orthopedic nail placement mechanism and replace the pointed probe with a blunt probe. At the same time, ensure that the position displayed on the scale 4 after the blunt probe is inserted is consistent with the position of the scale 4 before the pointed probe was replaced. The torque threshold of the first torque sensor and the torque threshold of the second torque sensor are both set to the torque threshold for the blunt probe to pass through the cancellous bone. The pressure thresholds of the first pressure sensor and the second pressure sensor are both set to the pressure thresholds that can clamp the blunt probe. The second motor 13 is set to the maximum insertion size value of the blunt probe. The orthopedic nail placement mechanism slowly twists and presses the blunt probe into the deep of the cancellous bone until it stops.

[0092] Step 6: Do not move the inserted probe, adjust the movable arm structure and move the orthopedic nail placement mechanism away from the probe;

[0093] Step 7: Replace the guide head 9 and the guide conical tube 7 of the orthopedic screw placement mechanism with a guide head 9 and a guide conical tube 7 whose inner diameter is suitable for the passage of the pedicle screw;

[0094] Step 8: Use a scalpel to expand the cuts on both sides of the probe 8 by a certain distance, adjust the movable arm structure to insert the head probe into the orthopedic nail placement mechanism until the guide conical tube 7 hits the expanded cut of the scalpel;

[0095] Step nine: setting a torque threshold of the first torque sensor, when the resistance of the guide tapered tube 7 when it hits the pedicle along the head probe is converted into the torque value of the second motor 13, so that the pressure thresholds of the first pressure sensor and the second pressure sensor are both 0, so that the head probe can pass through the orthopedic screw placement mechanism without resistance, and the orthopedic screw placement mechanism presses the guide tapered tube 7 suitable for the pedicle screw to pass through, when the torque threshold of the first torque sensor reaches the set torque threshold, the second motor 13 automatically stops;

[0096] Step 10: Adjust the movable arm structure, keep the position of the guide cone tube 7 unchanged, and disassemble and separate the guide cone tube 7 from the guide head 9;

[0097] Step 11: Hold the hollow long rod pedicle screwdriver head between the first roller 27 and the second roller 28, and install the pedicle self-tapping screw on the hollow long rod pedicle screwdriver head; adjust the movable arm structure, insert the orthopedic screw placement mechanism for installing the pedicle self-tapping screw along the head probe into the guide tapered tube 7 suitable for the pedicle to pass through, directly contact the pedicle, and the long rod pedicle screwdriver head is an existing device; Step 12: Set the torque threshold of the first torque sensor and the torque threshold of the second torque sensor, so that the pressure thresholds of the first pressure sensor and the second pressure sensor are both capable of clamping the hollow long rod The pressure threshold of the pedicle screwdriver head is set, and the movement mode of the first motor 11 is adjusted from twisting to rotation. The first roller 27 and the second roller 28 clamp the hollow long rod pedicle screwdriver head, and the first motor 11 drives the twisting disk 18 to rotate, and then drives the hollow long rod pedicle screwdriver head through the first roller 27 and the second roller 28 to screw the pedicle self-tapping screw into the pedicle; the orthopedic screw placement mechanism screws the pedicle self-tapping screw into the pedicle, and when the torque threshold of the first torque sensor and the torque threshold of the second torque sensor reach the set torque threshold, the first motor 11 and the second motor 13 stop automatically.

[0098] Embodiment 1

[0099] Before using the orthopedic nail placement device, the torque threshold and pressure threshold corresponding to each type of tissue to be perforated are specifically formulated according to the characteristics of the patient's skin, cortical bone and cancellous bone. The first pressure sensor, the second pressure sensor, the first torque sensor and the second torque sensor have all been set with the pressure threshold and torque threshold for penetrating the skin, the pressure threshold and torque threshold for penetrating the cortical bone, and the pressure threshold and torque threshold for penetrating the cancellous bone. The above thresholds need to be set one-to-one according to the type of probe 8.

[0100] When using the orthopedic nail placement device, first fix the fixing clamp 1 beside the operating table, adjust the position of the orthopedic nail placement mechanism by adjusting the movable arm 2, and then insert the pointed probe into the orthopedic nail placement mechanism in turn so that the bottom of the probe 8 is flush with the top of the ruler, and the pointed tip is exposed from the guide conical tube 7. The position of the orthopedic nail placement mechanism is adjusted again so that the pointed probe touches the skin to be punched. Start the orthopedic nail placement device, the second motor 13 drives the first lead screw 14 to engage with the trapezoidal thread on the third support frame 15 to push the slide 17 to drive the pointed probe to be pressed deep into the skin along the slide rail 16, and at the same time, the fifth motor 21 drives the first movable clamp 22 and the second movable clamp 25 to clamp the first roller bracket 29 and the second roller bracket 30, thereby driving the first roller 27 and the second roller 28 to clamp the pointed probe, and then the first motor 11 drives the first roller 27 and the second roller 28 through the twisting plate 18, and then drives the pointed probe to twist repeatedly in a forward 90° and reverse 90° manner. The first and second pressure sensors provided at the first movable clamp 22 and the second movable clamp 25 clamping the first roller bracket 29 and the second roller bracket 30 can transmit real-time pressure values ​​to the MCU and the display device, and the MCU controls the pressure applied to the probe 8 through a set pressure threshold.

[0101] When the guide conical tube 7 and the pointed probe pass through the skin and flesh, the first torque sensor arranged inside the second motor 13 detects the torque change in this process in real time, and transmits the real-time torque value to the MCU and the display device. The MCU determines whether the guide conical tube 7 and the pointed probe pass through the skin and flesh through a set torque threshold. If the torque value suddenly increases to exceed or decreases to below the threshold range during the passage, all motors stop moving instantly. When the torque value suddenly increases and exceeds the threshold value during the penetration, the parameters displayed on the display device are further used to determine whether the pointed probe has hit the pedicle cortical bone, and then an X-ray is performed to further confirm the position of the pointed probe; when the torque value suddenly decreases and falls below the threshold value during the penetration, the parameters displayed on the display device are further used to determine whether the pointed probe has penetrated the skin but failed to hit the pedicle cortical bone, and then an X-ray is performed to further confirm the position of the pointed probe; when it is confirmed that the pointed probe has hit the corresponding position of the pedicle cortical bone, the device of the present invention is restarted, and the second motor 13 continues to move to drive the pointed probe to press into the cortical bone, while the first motor 11 drives the pointed probe to repeatedly twist in a forward 90° and reverse 90° manner. When the pointed probe breaks through the pedicle cortical bone, the torque sensor inside the first motor 1 and the torque sensor inside the second motor simultaneously transmit the real-time torque to the MCU and the display, and all motors stop moving.

[0102] At this time, perform X-ray fluoroscopy to further confirm the position of the pointed probe. After confirming that the probe position is correct, replace the pointed probe with a blunt probe to ensure that the blunt probe is in the original position of the replaced pointed probe. Restart the device of the present invention. At this time, the second motor 13 is in a stationary state, and the first motor 11, the third motor 19, the fourth motor 20, and the fifth motor 21 are all in a working state. Among them, the third motor 19 and the fourth motor 20 perform forward and reverse repetitive motions, driving the blunt probe to move in the cancellous bone with a specific impact force. At the same time, the first motor 11 drives the blunt probe to repeatedly twist in a forward 90° and reverse 90° manner. According to the travel size of the blunt probe at 4 positions of the ruler and the X-ray fluoroscopy, the position of the pointed probe is further confirmed. When the desired position is reached, the device of the present invention can be stopped, or the device of the present invention can be automatically stopped according to the preset travel size parameters of the ruler.

[0103] If the stop probe cannot move forward, but the parameters displayed by each motor do not exceed the preset threshold range, replace the stop probe with a pointed probe, and reset the threshold ranges corresponding to the pointed probe, and then proceed to the next step until the probe reaches the desired position.

[0104] Embodiment 2

[0105] The orthopedic nail placement device is installed on the existing medical robot arm for fully automatic operation, reducing manual operation and performing difficult surgeries more accurately and safely.

[0106] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A reciprocating feeding unit, characterized in that: It comprises a driving mechanism, a first roller (27), a second roller (28) and a clamping mechanism; The driving mechanism is used to drive the first roller (27) and the second roller (28) to rotate, the clamping mechanism is used to achieve clamping between the first roller (27) and the second roller (28), and the first roller (27) and the second roller (28) are used to drive the probe (8) or a screwdriver head capable of cooperating with the pedicle screw to perform linear reciprocating motion; The driving mechanism comprises a third motor (19) and a fourth motor (20), the second roller (28) is arranged at an output end of the third motor (19), and the first roller (27) is arranged at an output end of the fourth motor (20); The first roller (27) and the second roller (28) are both provided with an annular groove capable of cooperating with the probe (8); The clamping mechanism comprises a guide rail structure, a fifth motor (21), a second lead screw (26), a first movable clamp (22), a second movable clamp (25), a first roller bracket (29) and a second roller bracket (30); the first roller bracket (29) and the second roller bracket (30) are both slidably arranged on the guide rail structure; the second roller (28) is rotatably arranged on the second roller bracket (30); the first roller (27) is rotatably arranged on the first roller bracket (29); the first roller bracket (29) and the second roller bracket (30) are arranged between the first movable clamp (22) and the second movable clamp (25); the fifth motor (21) is used for driving the second lead screw (26) to rotate; when the second lead screw (26) rotates, the first movable clamp (22) and the second movable clamp (25) clamp the first roller bracket (29) and the second roller bracket (30).

2. A reciprocating feeding unit according to claim 1, characterized in that: A first pressure sensor is provided at the contact position between the first movable clamp (22) and the second roller bracket (30), and a second pressure sensor is provided at the contact position between the second movable clamp (25) and the first roller bracket (29).

3. A reciprocating feeding unit according to claim 1, characterized in that: The first movable clamp (22) and the second movable clamp (25) are both engaged with the second lead screw (26) via self-locking trapezoidal threads.

4. A reciprocating feeding unit according to claim 1, characterized in that: The guide rail structure comprises a first guide rail (23) and a second guide rail (24); the first roller bracket (29) is slidably connected to the first guide rail (23) and the second guide rail (24); and the second roller bracket (30) is slidably connected to the first guide rail (23) and the second guide rail (24).

5. An orthopedic nail placement mechanism, characterized in that: It comprises a slide mechanism, a telescopic mechanism, a probe swing mechanism and a reciprocating feed unit as described in any one of claims 2 to 4; The slide mechanism comprises a slide rail (16) and a slide (17); the slide (17) is slidably connected to the slide rail (16); the telescopic mechanism is used to realize sliding between the slide (17) and the slide rail (16); the reciprocating feeding unit is arranged on the slide (17) through a twisting mechanism; and the probe swinging mechanism is used to realize the rotation of the reciprocating feeding unit.

6. The orthopedic nail placement mechanism according to claim 5, characterized in that: The twisting mechanism comprises a first support frame (10) and a twisting disk (18), the twisting disk (18) is rotatably connected to the first support frame (10) via a first bearing, the clamping mechanism is arranged on the twisting disk (18), the output end of the probe swing mechanism is fixedly connected to the twisting disk (18), and the probe swing mechanism is arranged on the slide (17).

7. The orthopedic nail placement mechanism according to claim 5, characterized in that: The probe swing mechanism is a first motor (11).

8. The orthopedic nail placement mechanism according to claim 5, characterized in that: The telescopic mechanism comprises a second motor (13), a first lead screw (14), a second support frame (12) and a third support frame (15); the third support frame (15) is arranged on the slide rail (16); the second motor (13) and the second support frame (12) are both arranged on the slide table (17); the first lead screw (14) is rotatably connected to the second support frame (12) via a second bearing; a threaded hole is provided on the third support frame (15); the first lead screw (14) is connected to the threaded hole; the second motor (13) is used to drive the first lead screw (14) to rotate.

9. The orthopedic nail placement mechanism according to claim 8, characterized in that: The output shaft of the second motor (13) is connected to the first lead screw (14) via a first torque sensor, and the output end of the probe swing mechanism is connected to the torsion disk (18) via a second torque sensor.

10. The orthopedic nail placement mechanism according to claim 8, characterized in that: The thread of the first screw (14) and the threaded hole are both self-locking trapezoidal threads.

11. The orthopedic nail placement mechanism according to claim 8, characterized in that: The first lead screw (14), the probe swing mechanism, the second motor (13) and the torsion disk (18) are all located on the same axial line; the output shaft of the probe swing mechanism, the output shaft of the second motor (13), the first lead screw (14) and the torsion disk (18) are all provided with through holes capable of passing the probe (8) at their axial positions; the through hole of the torsion disk (18) is located between the first roller (27) and the second roller (28).

12. An orthopedic nail placement mechanism according to any one of claims 9 to 11, characterized in that: The orthopedic nail placement mechanism further comprises a first protective cover (5) and a second protective cover (6), wherein the first protective cover (5) is used to cover the second motor (13) and the movement stroke of the second motor (13), and the second protective cover (6) is used to cover the probe swing mechanism and the reciprocating feeding unit.

13. The orthopedic nail placement mechanism according to claim 12, characterized in that: The orthopedic nail placement mechanism also includes a guide head (9) and a guide conical tube (7) for guiding a probe (8); the guide head (9) is arranged at the end of the second protective cover (6) close to the reciprocating feeding unit; the guide conical tube (7) is detachably connected to the guide head (9).

14. An orthopedic nail placement mechanism according to claim 13, characterized in that: The orthopedic nail placement mechanism also includes a ruler (4) for measuring the travel distance of the probe (8), and the ruler (4) is arranged at the outer end of the first lead screw (14).

15. An orthopedic nail placement mechanism according to claim 14, characterized in that: A circular plate is provided at the end of the ruler (4) away from the first lead screw (14), the circular plate is provided with a circular hole capable of passing a probe (8), the ruler (4) is provided with a hollow groove capable of cooperating with the probe (8), the circular hole is connected to the hollow groove, and the ruler (4) is provided with two scale lines, which are symmetrically arranged on both sides of the hollow groove.

16. An orthopedic nail placement device, characterized in that: It comprises a fixing clamp structure, a movable arm structure and an orthopedic nail placement mechanism as claimed in claim 15; The fixing clamp structure is connected to the slide rail (16) via the movable arm structure.

17. An orthopedic nail placement device according to claim 16, characterized in that: The fixing clamp structure comprises a fixing clamp (1) and four hand-tightening bolts. The fixing clamp (1) has a C-shaped cross section. The four hand-tightening bolts are arranged at the bottom of the fixing clamp (1). A non-slip rubber pad is arranged on the top of each hand-tightening bolt. The fixing clamp (1) is connected to the movable arm structure.

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