Artificial acetabulum angle measuring instrument in hip joint operation

Abstract

The invention relates to the technical field of iron piece processing, in particular to an artificial acetabulum angle measuring instrument in hip joint operation, which comprises an operating table, a measuring part and a placing frame, the placing frame comprises a longitudinal frame and a transverse frame, the inner side of the measuring part is provided with a sliding groove, the longitudinal frame is fixedly provided with a fixing block, one end of the fixing block is provided with a sliding block, and the transverse frame slides in the sliding process. The fixing blocks are arranged in the sliding grooves in a sliding mode through the sliding blocks. The operating table is used for a patient to lie on the back, the knee sheath is adjusted through the first telescopic rod to fix the knee of the patient, meanwhile, the ankle fixing block is adjusted through the second telescopic rod to fix the shank of the patient, and at the moment, the shank of the patient can be bent to be perpendicular to the operating table and swing left and right to the maximum angle; therefore, the rotation angle of the acetabulum can be observed through the first measuring disc, and meanwhile, the acetabulum angle can be compared with the second measuring disc, so that more accurate acetabulum angle data can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of medical instruments, and in particular to an instrument for measuring the angle of an artificial acetabulum during hip joint surgery. Background Art

[0002] Measuring the angle of the artificial acetabulum during hip surgery is one of the important steps to ensure the success of artificial hip replacement. The accuracy of this process is crucial to maintaining the stability and range of motion of the hip joint and reducing the long-term revision rate. It can accurately measure the anteversion and abduction angles of the artificial acetabulum to ensure that the acetabular prosthesis is installed in the appropriate position, thereby improving the success rate of hip replacement surgery. The appropriate acetabular angle can optimize the biomechanical properties of the hip joint and reduce the probability of postoperative complications such as prosthesis wear and dislocation.

[0003] In hip replacement surgery, acetabular angle measuring instruments are usually of two types: mechanical and electronic. The mechanical type is often used for intraoperative measurement due to its greater flexibility. The mechanical acetabular angle measuring instrument is usually a simple and sturdy tool made of metal and other materials. It has an intuitive angle scale, just like an ordinary protractor. During surgery, the doctor can place it on the anatomical landmarks or surgical instruments around the acetabulum and directly read the angle value. Its advantages are simple structure, low cost, and no need for additional electronic equipment or energy supply.

[0004] In the prior art, patients generally adopt a supine position and swing their legs to measure the acetabulum angle. Since the linkage between the acetabulum and the calf needs to be considered during hip replacement, the hip joint will produce a certain rotation angle when the patient's calf is bent and swung. Due to the differences in the body structure of patients, a dedicated medical plan needs to be formulated based on the patient's clinical measurement data. At this time, electronic measuring instruments are not convenient for intraoperative measurement, and are lacking in mechanical measurement of the calf swing and hip joint rotation angle. Therefore, certain measurement errors may occur, which will increase the risk of prosthesis wear and increase the probability of complications.

[0005] Therefore, there is an urgent need to improve the artificial acetabulum angle measuring instrument during hip joint surgery to solve the above-mentioned problems. Summary of the invention

[0006] The invention provides an artificial acetabulum angle measuring instrument during hip joint surgery, which is used to solve the defect of incomplete grinding in the prior art.

[0007] A hip joint intraoperative artificial acetabulum angle measuring instrument, comprising an operating table and a measuring part. A placement rack is slidably arranged on the bottom side of the operating table. The placement rack includes a longitudinal rack and a transverse rack fixedly connected to the longitudinal rack. The transverse rack is slidably arranged on the bottom side of the operating table. A chute is opened inside the measuring part. A fixing block is fixedly installed on the longitudinal rack. One end of the fixing block is provided with a slider. During the sliding process of the transverse rack, the fixing block is slidably arranged inside the chute through the slider;

[0008] One side of the fixing block away from the slider is rotatably connected with a bidirectional convex shaft. One side of the bidirectional convex shaft away from the fixing block is fixedly connected with a first telescopic rod. A knee sheath is fixedly connected to the first telescopic rod. One end of the knee sheath away from the first telescopic rod is rotatably connected with a second measuring disc. A push block is rotatably arranged on the longitudinal rack corresponding to the second measuring disc. The second measuring disc is slidably arranged on the upper side of the push block. One end of the second measuring disc away from the knee sheath is fixedly connected with a second telescopic rod. One end of the second telescopic rod away from the second measuring disc is fixedly connected with an ankle fixing block.

[0009] Preferably, a first measuring disc is fixedly arranged on one side of the fixing block close to the bidirectional convex shaft. A first pointer is fixedly arranged on the side surface of the bidirectional convex shaft. The first pointer corresponds to the first measuring disc.

[0010] Preferably, the first telescopic rod and the knee sheath are rotatably arranged on the upper side of the longitudinal rack through the bidirectional convex shaft. A limiting clip is fixedly arranged on the transverse rack corresponding to the first telescopic rod. The first telescopic rod is rotatably arranged inside the limiting clip.

[0011] Preferably, a limiting nut is fixedly installed on the first telescopic rod. The limiting nut is used for limiting the knee sheath. The knee sheath is slidably arranged between the two transverse racks.

[0012] Preferably, a convex rib is fixedly installed on the longitudinal rack. The bottom side of the knee sheath is in contact with the upper end of the convex rib.

[0013] Preferably, a straight groove is opened on the convex rib. A notch is opened in the middle of the second measuring disc. A shaft rod is fixedly installed inside the notch. The second telescopic rod is rotatably arranged on the placement rack through the shaft rod. And during the rotation of the second measuring disc, the shaft rod slides inside the straight groove.

[0014] Preferably, thigh tightening straps are fixedly installed on both sides of the knee sheath. Calf tightening straps are fixedly installed on both sides of the ankle fixing block. Magic tapes are fixedly installed on the side surfaces of the thigh tightening straps and the calf tightening straps.

[0015] Preferably, a plurality of uniformly distributed U-shaped fixing plates are fixedly installed on the bottom side of the operating table through bolts, and the cross frame is slidably arranged inside the U-shaped fixing plates.

[0016] Preferably, a chest restraint strap is fixedly installed on the upper side of the operating table, a buckle is fixedly installed at the position of the operating table corresponding to the chest restraint strap, and the upper end of the chest restraint strap corresponds to the buckle.

[0017] Preferably, a second pointer is fixedly installed on the bottom side of the second telescopic rod, and one end of the second pointer away from the second telescopic rod corresponds to the scale on the bottom side of the second measuring disk.

[0018] For a hip joint intraoperative artificial acetabular angle measuring instrument provided by the present invention, a patient can lie on the operating table on his back. The knee sheath is adjusted through the first telescopic rod to fix the patient's knee, and at the same time, the ankle fixing block is adjusted through the second telescopic rod to fix the patient's calf. At this time, the patient's calf can be bent to be perpendicular to the operating table and swung left and right to the maximum angle. Furthermore, the angle of acetabular rotation can be observed through the first measuring disk, and at the same time, it can be compared with the second measuring disk to obtain more accurate acetabular angle data. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 is an overall elevation view of a hip joint intraoperative artificial acetabular angle measuring instrument provided by an embodiment of the present invention;

[0021] Figure 2 is a hip joint intraoperative artificial acetabular angle measuring instrument provided by an embodiment of the present invention Figure 1 magnified schematic view at position A;

[0022] Figure 3 is a schematic structural view of a placement rack of a hip joint intraoperative artificial acetabular angle measuring instrument provided by an embodiment of the present invention;

[0023] Figure 4 is a schematic structural view of a second telescopic rod of a hip joint intraoperative artificial acetabular angle measuring instrument provided by an embodiment of the present invention;

[0024] Figure 5 is a hip joint intraoperative artificial acetabular angle measuring instrument provided by an embodiment of the present invention Figure 4 magnified schematic view at position B;

[0025] Figure 6 It is a schematic structural view of the knee sheath of an artificial acetabular angle measuring instrument during hip joint surgery provided by an embodiment of the present invention;

[0026] Figure 7 It is a schematic structural view of the push block and the second measuring disc of an artificial acetabular angle measuring instrument during hip joint surgery provided by an embodiment of the present invention.

[0027] Reference numerals:

[0028] 1. Operating table; 2. Measuring part; 21. Slide groove; 3. Placing rack; 31. Vertical rack; 32. Horizontal rack; 33. Fixed block; 34. Slide block; 35. First measuring disc; 36. Limit clip; 37. Convex rib; 38. Straight notch; 5. Bi-directional convex shaft; 51. First pointer; 6. First telescopic rod; 61. Limit nut; 7. Knee sheath; 8. Second measuring disc; 81. Notch; 82. Shaft rod; 9. Push block; 10. Second telescopic rod; 11. Ankle fixing block; 12. Thigh tightening belt; 13. Calf tightening belt; 14. Magic tape; 15. U-shaped fixing plate; 16. Chest restraint belt; 17. Buckle; 18. Second pointer. Detailed implementation manners

[0029] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] The following will be combined with Figure 1 - Figure 7 Describe the present invention.

[0031] As Figure 1 、 Figure 2 And Figure 3 shown, the artificial acetabular angle measuring instrument during hip joint surgery provided in this embodiment includes an operating table 1 and a measuring part 2. A placing rack 3 is slidably arranged on the bottom side of the operating table 1. The placing rack 3 includes a vertical rack 31 and a horizontal rack 32 fixedly connected to the vertical rack 31. The horizontal rack 32 is slidably arranged on the bottom side of the operating table 1. A slide groove 21 is opened inside the measuring part 2. A fixed block 33 is fixedly installed on the vertical rack 31. One end of the fixed block 33 is provided with a slide block 34. During the sliding of the horizontal rack 32, the fixed block 33 is slidably arranged inside the slide groove 21 through the slide block 34. The measuring part 2 can keep the operating table 1 flat through a cover plate, so as to meet the basic surgical requirements.

[0032] On one side of the fixed block 33 away from the slider 34, a bidirectional convex shaft 5 is rotatably connected. On the side of the bidirectional convex shaft 5 away from the fixed block 33, a first telescopic rod 6 is fixedly connected. A knee sheath 7 is fixedly connected to the first telescopic rod 6. One end of the knee sheath 7 away from the first telescopic rod 6 is rotatably connected to a second measuring disc 8. A push block 9 is rotatably arranged at the position of the longitudinal frame 31 corresponding to the second measuring disc 8. The second measuring disc 8 is slidably arranged on the upper side of the push block 9. One end of the second measuring disc 8 away from the knee sheath 7 is fixedly connected to a second telescopic rod 10. One end of the second telescopic rod 10 away from the second measuring disc 8 is fixedly connected to an ankle fixing block 11.

[0033] Among them, the patient can lie supine on the operating table 1. First, by adjusting the position of the placement frame 3, one of the acetabulum positions of the patient is made corresponding. The knee of the patient is fixed by adjusting the knee sheath 7 through the first telescopic rod 6. At the same time, the lower leg part of the patient is fixed by adjusting the ankle fixing block 11 through the second telescopic rod 10. At this time, the patient's lower leg can be bent to be perpendicular to the operating table 1 and swung left and right to the maximum angle. Furthermore, the rotation angle of the acetabulum can be observed through the first measuring disc 35. At the same time, it can be compared with the second measuring disc 8 to obtain more accurate acetabulum angle data.

[0034] To solve the problem of the patient's lower leg bending downward:

[0035] As Figure 1 shown, there are support legs at the bottom of the placement frame 3. Articulated rods can be arranged on the support legs. One end of the articulated rod is rotatably connected to the support leg through a universal joint. The other end of the articulated rod is rotatably connected to the bottom side of the ankle fixing block 11. When it is necessary to bend the patient's lower leg, the ankle fixing block 11 is rotated to the bottom side of the operating table 1 by folding the articulated rod. The joint of the articulated rod shrinks towards the bottom side of the knee sheath 7. At this time, the rotation angle of the acetabulum can be measured through the swing of the second telescopic rod 10.

[0036] Specifically, when the patient's lower leg is bent, the second telescopic rod 10 rotates clockwise, and the ankle fixing block 11 moves downward (not shown in the figure for showing the structure).

[0037] Figure 2 is an enlarged schematic view of part A in a hip joint intraoperative artificial acetabulum angle measuring instrument provided by an embodiment of the present invention. Figure 1 In the figure.

[0038] Figure 3 is a structural diagram of the placement frame of a hip joint intraoperative artificial acetabulum angle measuring instrument provided by an embodiment of the present invention.

[0039] As Figure 2 and Figure 3As shown in the figure, a first measuring disc 35 is fixedly arranged on one side of the fixed block 33 close to the double-sided convex shaft 5. A first pointer 51 is fixedly arranged on the side surface of the double-sided convex shaft 5. The first pointer 51 corresponds to the first measuring disc 35. The first telescopic rod 6 and the knee sheath 7 are rotatably arranged on the upper side of the longitudinal frame 31 through the double-sided convex shaft 5. A limit clip 36 is fixedly arranged at the position of the transverse frame 32 corresponding to the first telescopic rod 6. The first telescopic rod 6 is rotatably arranged inside the limit clip 36. A limit nut 61 is fixedly installed on the first telescopic rod 6. The limit nut 61 is used to limit the knee sheath 7. The knee sheath 7 is slidably arranged between the two transverse frames 32.

[0040] Among them, during the sliding process of the placement rack 3, the fixed block 33 can slide along with the longitudinal frame 31, so as to align it with the acetabulum of the patient. During the left and right swaying of the patient's calf, the knee sheath 7 drives the first telescopic rod 6 to rotate. The first telescopic rod 6 drives the double-sided convex shaft 5 to rotate, so that the first pointers 51 at both ends thereof swing up and down, and thus the rotation angle of the acetabulum can be easily measured.

[0041] The limit nut 61 is used to limit the first telescopic rod 6, which can meet the measurements of patients with different heights. Similarly, the second telescopic rod 10 can be used to adapt to patients with different calf lengths, thereby improving the applicability of the artificial acetabulum angle measuring instrument during hip joint surgery.

[0042] Figure 4 It is a schematic diagram of the rotation of the second telescopic rod of an artificial acetabulum angle measuring instrument during hip joint surgery provided by an embodiment of the present invention.

[0043] Figure 5 It is an artificial acetabulum angle measuring instrument during hip joint surgery provided by an embodiment of the present invention Figure 4 The enlarged schematic diagram at position B in the figure.

[0044] Figure 6 It is a schematic diagram of the double-sided convex shaft, the first telescopic rod, the knee sheath and the second measuring disc structure of an artificial acetabulum angle measuring instrument during hip joint surgery provided by an embodiment of the present invention.

[0045] Figure 7 It is a schematic diagram of the push block and the second measuring disc structure of an artificial acetabulum angle measuring instrument during hip joint surgery provided by an embodiment of the present invention.

[0046] Such as Figure 4 、 Figure 5 、 Figure 6 And Figure 7As shown, a rib 37 is fixedly installed on the longitudinal frame 31, and the bottom side of the knee sheath 7 is in contact with the upper end of the rib 37; a straight notch 38 is formed on the rib 37, a notch 81 is formed in the middle of the second measuring disc 8, and a shaft rod 82 is fixedly installed inside the notch 81. The second telescopic rod 10 is rotatably arranged on the placement rack 3 through the shaft rod 82. During the rotation of the second measuring disc 8, the shaft rod 82 slides inside the straight notch 38. The bottom side of the second telescopic rod 10 is fixedly installed with a second pointer 18, and the end of the second pointer 18 away from the second telescopic rod 10 corresponds to the scale on the bottom side of the second measuring disc 8.

[0047] Among them, during the process of the patient's calf being lifted, the position where the knee sheath 7 is connected to the push block 9 is bent by the spring. At this time, the push block 9 rotates upward, and at the same time, the transmission second measuring disc 8 is in a vertical state. At this time, the scale on the side of the second measuring disc 8 can be clearly observed through the second pointer 18, which is convenient for comparing the associated angle between the calf movement of the patient and the acetabulum. Furthermore, the measurement accuracy is greatly improved, the risk of prosthesis wear is reduced, and thus the probability of complications is reduced.

[0048] Meanwhile, as Figure 3 and Figure 4 shown, thigh tightening straps 12 are fixedly installed on both sides of the knee sheath 7, and calf tightening straps 13 are fixedly installed on both sides of the ankle fixing block 11. Magic tapes 14 are fixedly installed on the sides of the thigh tightening straps 12 and the calf tightening straps 13.

[0049] The thigh tightening straps 12 and the calf tightening straps 13 cooperate with the magic tapes 14 to firmly fix the knee sheath 7 on the leg. For the knee sheath, a stable fixing position is crucial. During the movement of the calf, the leg muscles will contract and relax, and the joints will move. If the knee sheath 7 is not well fixed, it is easy to shift.

[0050] Moreover, the design of the magic tape 14 enables the tightening straps to adapt to thighs and calves of different thicknesses. Because the leg shapes and leg sizes of different people vary greatly, it is difficult for fixed straps with a single fixed size to meet the needs of everyone.

[0051] Furthermore, as Figure 3 shown, a number of uniformly distributed U-shaped fixing plates 15 are fixedly installed on the bottom side of the operating table 1 through bolts, and the cross frame 32 is slidably arranged inside the U-shaped fixing plates 15. The cross frame 32 can slide inside the U-shaped fixing plates 15. This design increases the flexibility of the structure. In the acetabulum surgery scenario, it is necessary to adjust the position of the cross frame 32 according to the specific requirements of the surgical operation, the acetabulum of the patient, or the layout of the medical devices.

[0052] This design also helps to optimize the space utilization in the operating room. Since the crossbeam 32 can slide, when certain equipment is not needed or the space around the operating table needs to be cleaned, the crossbeam 32 can be slid to a suitable position to avoid interfering with surgical operations or personnel movement.

[0053] In addition, as Figure 1 shown, a chest restraint strap 16 is fixedly installed on the upper side of the operating table 1, and a buckle 17 is fixedly installed at the position of the operating table 1 corresponding to the chest restraint strap 16. The upper end of the chest restraint strap 16 corresponds to the buckle 17. The chest restraint strap 16 and the buckle 17 cooperate to mainly fix the chest position of the patient. During the operation, the patient may move their body position due to unconscious movements under anesthesia, reactions to surgical stimuli, or surgical operations. During the hip replacement operation, even a slight body shake may affect the accuracy of the operation. The chest restraint strap 16 can effectively limit the movement of the patient's chest, thereby reducing the overall body shake and ensuring the smooth progress of the operation.

[0054] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative efforts.

[0055] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on such an understanding, the above technical solution, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disc, etc., and includes several instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An instrument for measuring the angle of artificial acetabulum during hip joint surgery, comprising an operating table (1) and a measuring unit (2), characterized in that: A placing frame (3) is slidably provided on the bottom side of the operating table (1), a fixing block (33) is fixedly installed on the placing frame (3), a bidirectional convex shaft (5) is rotatably connected to one side of the fixing block (33), a first telescopic rod (6) is fixedly connected to the side of the bidirectional convex shaft (5) away from the fixing block (33), and a knee sheath (7) is fixedly connected to the first telescopic rod (6); The end of the knee guard (7) away from the first telescopic rod (6) is rotatably connected to a second measuring disc (8); the vertical frame (31) is rotatably provided with a push block (9) corresponding to the position of the second measuring disc (8); the second measuring disc (8) is slidably provided on the upper side of the push block (9); the end of the second measuring disc (8) away from the knee guard (7) is fixedly connected to a second telescopic rod (10); and the end of the second telescopic rod (10) away from the second measuring disc (8) is fixedly connected to an ankle fixing block (11).

2. The artificial acetabulum angle measuring instrument for hip joint surgery according to claim 1, characterized in that: The placement frame (3) comprises a longitudinal frame (31) and a transverse frame (32) fixedly connected to the longitudinal frame (31); the transverse frame (32) is slidably arranged on the bottom side of the operating table (1); a slide groove (21) is provided on the inner side of the measuring part (2); the fixed block (33) is fixedly installed on the longitudinal frame (31); a slider (34) is provided at one end of the fixed block (33); during the sliding process of the transverse frame (32), the fixed block (33) is slidably arranged inside the slide groove (21) via the slider (34); A first measuring disk (35) is fixedly arranged on one side of the fixed block (33) close to the bidirectional convex shaft (5), and a first pointer (51) is fixedly arranged on the side of the bidirectional convex shaft (5), wherein the first pointer (51) corresponds to the first measuring disk (35).

3. The artificial acetabulum angle measuring instrument for hip joint surgery according to claim 2, characterized in that: The first telescopic rod (6) and the knee guard (7) are rotatably arranged on the upper side of the longitudinal frame (31) via the bidirectional convex shaft (5); a limit clamp (36) is fixedly arranged on the transverse frame (32) corresponding to the position of the first telescopic rod (6); and the first telescopic rod (6) is rotatably arranged inside the limit clamp (36).

4. The artificial acetabulum angle measuring instrument for hip joint surgery according to claim 2, characterized in that: A limit nut (61) is fixedly mounted on the first telescopic rod (6), and the limit nut (61) is used to limit the position of the knee guard (7). The knee guard (7) is slidably arranged between the two cross frames (32).

5. The instrument for measuring artificial acetabulum angle during hip joint surgery according to claim 2, characterized in that: A convex rib (37) is fixedly mounted on the longitudinal frame (31), and the bottom side of the knee protector (7) is in contact with the upper end of the convex rib (37).

6. The instrument for measuring artificial acetabulum angle during hip joint surgery according to claim 5, characterized in that: A straight slot (38) is provided on the convex rib (37), a notch (81) is provided in the middle of the second measuring disk (8), a shaft (82) is fixedly installed inside the notch (81), the second telescopic rod (10) is rotatably arranged on the placement frame (3) via the shaft (82), and during the rotation of the second measuring disk (8), the shaft (82) slides inside the straight slot (38).

7. The instrument for measuring artificial acetabulum angle during hip joint surgery according to claim 1, characterized in that: Thigh binding belts (12) are fixedly mounted on both sides of the knee sleeve (7), calf binding belts (13) are fixedly mounted on both sides of the ankle fixing block (11), and Velcro (14) is fixedly mounted on the sides of the thigh binding belt (12) and the calf binding belt (13).

8. The instrument for measuring artificial acetabulum angle during hip joint surgery according to claim 2, characterized in that: A plurality of evenly distributed U-shaped fixing plates (15) are fixedly mounted on the bottom side of the operating table (1) by means of bolts, and the cross frame (32) is slidably arranged inside the U-shaped fixing plates (15).

9. The instrument for measuring artificial acetabulum angle during hip joint surgery according to claim 1, characterized in that: A chest restraint belt (16) is fixedly mounted on the upper side of the operating table (1), and a buckle (17) is fixedly mounted on the operating table (1) at a position corresponding to the chest restraint belt (16), and the upper end of the chest restraint belt (16) corresponds to the buckle (17).

10. The instrument for measuring artificial acetabulum angle during hip joint surgery according to claim 1, characterized in that: A second pointer (18) is fixedly mounted on the bottom side of the second telescopic rod (10), and an end of the second pointer (18) away from the second telescopic rod (10) corresponds to the scale on the bottom side of the second measuring disk (8).

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