Total hip arthroplasty lower extremity isometric calibrator

Abstract

The application relates to a medical auxiliary tool, in particular to a full hip joint replacement lower limb equal length calibrator, which has the technical scheme as follows: a main ruler plate, a sub-ruler plate and two positioning rods, the two positioning rods are fixed on the main ruler plate and the sub-ruler plate respectively, the sub-ruler plate is slidably connected with the main ruler plate, the main ruler plate and the sub-ruler plate are both provided with scale lines, the arrangement direction of the scale lines is the same as the sliding direction of the sub-ruler plate on the main ruler plate, and the scale lines can reflect the total length of the main ruler plate and the sub-ruler plate; the purpose of improving the consistency of the lengths of the two lower limbs is achieved.

Description

Technical Field

[0001] This application relates to a medical assistive device, and more particularly to an isometric calibrator for lower limbs after total hip replacement. Background Technology

[0002] Hip replacement surgery is one of the effective means to treat diseases such as femoral head necrosis, femoral neck fracture, and hip osteoarthritis. There are many reference indicators for the success of hip replacement surgery, such as equal length of both lower limbs. If the length difference between the two lower limbs exceeds 5mm, the patient may feel discomfort; if the length difference between the two lower limbs exceeds 10mm, it will cause obvious discomfort to the patient, and may even lead to pelvic tilt and affect the patient's recovery.

[0003] Currently, the common method for maintaining the balance of surrounding soft tissues and equal length of both lower limbs after total hip arthroplasty is to take standard radiographs and perform preoperative template measurements. While this method can roughly determine the size of the prosthesis, femoral distance, femoral offset, and femoral neck length required during surgery, it is easily affected by the patient's weight, the magnification of the X-ray, and some specific conditions during surgery, resulting in limited accuracy in measuring the length of both lower limbs and further leading to differences in the length of the two lower limbs after surgery. Summary of the Invention

[0004] To improve the consistency of lower limb length after surgery, this application provides a lower limb length calibrator for total hip arthroplasty.

[0005] The lower limb isometric calibrator provided in this application adopts the following technical solution: A lower limb isometric calibrator for total hip replacement includes a main scale plate, a secondary scale plate, and two positioning rods. The two positioning rods are fixed to the main scale plate and the secondary scale plate respectively. The secondary scale plate is slidably connected to the main scale plate. Both the main scale plate and the secondary scale plate are provided with scale lines. The arrangement direction of the scale lines is the same as the sliding direction of the secondary scale plate on the main scale plate. The scale lines can reflect the total length of the main scale plate and the secondary scale plate.

[0006] By employing the above-mentioned technical solution, for patients with naturally symmetrical lower limb lengths, before dislocation of the hip joint during total hip arthroplasty, an entry point is determined on the iliac bone and the greater trochanter of the femur, respectively. Two positioning rods are fixed at the corresponding entry points, and the positional relationship between the main and auxiliary rulers is adjusted to accommodate the distance between the two entry points. The total length of the main and auxiliary rulers at this time is obtained through the scale lines. This total length directly or indirectly reflects the distance between the two entry points, and the value reflected by the scale lines at this time is recorded. Next, the hip joint is dislocated, and a trial model of the hip joint prosthesis is installed. If the lower limb length changes at this time, one of the positioning rods will inevitably be unable to be inserted into the corresponding entry point. The lengths of the main and auxiliary rulers are adjusted until both positioning rods can be fixed at their original corresponding entry points. The difference between the verticality reflected by the scale lines at this time and the verticality reflected before surgery can be used to assess the required femoral prosthesis neck length and femoral head prosthesis size, thereby ensuring that the postoperative lower limb length is consistent with the preoperative design, thus achieving the effect of improving the consistency of lower limb length after surgery.

[0007] Optionally, the positioning rod on the main ruler plate is rotatably connected to the main ruler plate and can be fixed on the main ruler plate, and the positioning rod on the secondary ruler plate is rotatably connected to the secondary ruler plate and can be fixed on the secondary ruler plate.

[0008] Based on differences in patient weight and the thickness of subcutaneous tissue at the hip joint, a suitable incision position can be selected on the human body to expose the iliac bone and the greater trochanter of the femur. Since there will inevitably be an angle between the exposed surfaces of the iliac bone and the greater trochanter of the femur, the above-mentioned technical solution allows for easy adjustment of the angle between the positioning rod and the main scale plate according to the inclination of the corresponding exposed surfaces. Furthermore, it ensures the consistency of the length direction of the main scale plate with the extension direction of both lower limbs under these conditions, thereby improving measurement accuracy. It also facilitates the consistency of the length direction of the main scale plate during preoperative and postoperative measurements, thus improving the accuracy of estimating the required femoral prosthesis neck length and femoral head prosthesis size.

[0009] Optionally, a fixed plate is fixed on both the main scale plate and the secondary scale plate. A rotating plate is set on the fixed plate. A positioning screw is threaded onto the positioning rod. The positioning screw passes through both the fixed plate and the rotating plate. The head of the positioning screw and the positioning rod are located on opposite sides of the rotating plate and the fixed plate, respectively.

[0010] By adopting the above technical solution, once the angle between the positioning rod and the main ruler plate or the secondary ruler plate is determined, the positioning screw is tightened until the fixed plate and the rotating plate are pressed between the head of the positioning screw and the positioning rod, thereby achieving positional fixation between the positioning rod, the rotating plate, the fixed plate and the corresponding ruler plate.

[0011] Optionally, a compressed return spring is provided between the rotating disk and the fixed disk.

[0012] By adopting the above technical solution, during the process of turning the positioning screw to separate the fixed disk from the rotating disk, the return spring can provide elastic force to separate the rotating disk from the fixed disk, thereby facilitating one-handed operation to separate the rotating disk from the fixed disk.

[0013] Optionally, the rotating disk and the fixed disk are coaxially arranged, and a connecting part is formed on the side of the rotating disk away from the fixed disk. The positioning rod can drive the connecting part to rotate around the axis of the rotating disk. The fixed disk has multiple toothed grooves distributed at intervals along the circumference of the fixed disk on the side close to the rotating disk, and multiple positioning teeth are formed on the side of the rotating disk close to the fixed disk, which can be inserted into the corresponding toothed grooves at the same time.

[0014] By adopting the above technical solution, when the positioning screw is tightened, the rotating disk and the fixed disk fit together, and each positioning tooth is adapted to be inserted into the corresponding tooth groove. This effectively prevents the rotating disk and the fixed disk from rotating relative to each other during the measurement process, thus preventing the positioning screw from loosening.

[0015] Optionally, multiple positioning marks are marked on the circumference of both the rotating disk and the fixed disk. The positioning marks on the fixed disk are set between two adjacent tooth grooves, and the positioning marks on the rotating disk are set between two adjacent positioning teeth.

[0016] By adopting the above technical solution, the angle between the positioning rod and the main or secondary ruler plate can be determined based on the positioning marks during the measurement process before hip dislocation. In this way, after hip dislocation, during the process of fixing the positioning rod and the main or secondary ruler plate together before measurement, the angle between the positioning rod and the main or secondary ruler plate required for this measurement can be determined according to the previous positioning mark sequence. This facilitates the consistency of the tilt angle of the positioning rod before and after hip dislocation, thereby improving the accuracy of estimating the required femoral prosthesis neck length and femoral head prosthesis size based on the measurement results before and after hip dislocation.

[0017] Optionally, one of the positioning rods is a Kirschner wire, and the other positioning rod is a screw-in rod with threads on its circumference.

[0018] By adopting the above technical solution, the Kirschner wire is fixed on the greater trochanter of the femur and the screw-in rod is screwed into the iliac bone to adapt to the situation where the greater trochanter of the femur is thin and has an irregular surface, making it difficult to achieve threaded fit. The screw-in rod is screwed into the iliac bone in order to improve the stability of the entire calibrator during the measurement process.

[0019] Optionally, the length direction of the main ruler plate is the same as that of the secondary ruler plate. The main ruler plate has an adjustment groove for inserting the secondary ruler plate, which can slide inside the adjustment groove. The main ruler plate is provided with fixing screws for fixing the secondary ruler plate to the main ruler plate.

[0020] By adopting the above technical solution, when the rotation angles of the two positioning rods are different, the total length formed by the main scale plate and the secondary scale plate can be adjusted so that the length direction of the main scale plate and the secondary scale plate is as parallel as possible to the measurement direction of the two lower limbs, that is, the vertical axis direction of the human body. This ensures the consistency of the measurement direction before and after hip dislocation, thereby improving the accuracy of estimating the required femoral prosthesis neck length and femoral head prosthesis size.

[0021] Optionally, both the main scale and the secondary scale are marked with scale values. The numbers corresponding to the scale values ​​on the main scale gradually increase as they approach the secondary scale, and the numbers corresponding to the scale values ​​on the secondary scale gradually increase as they approach the main scale. The maximum number corresponding to the scale value on the main scale is less than the minimum number corresponding to the scale value on the secondary scale.

[0022] By adopting the above technical solution, once the total length of the main ruler and the secondary ruler is adjusted, the number corresponding to the scale line on the secondary ruler that is aligned with the edge of the main ruler is the total length of the main ruler and the secondary ruler.

[0023] In summary, this application has the following technical effects: 1. By setting up a main ruler plate, a secondary ruler plate, and two positioning rods, the accuracy of assessing the required femoral side prosthesis neck length and femoral head prosthesis size is improved, thereby achieving the effect of improving the consistency of the length of both lower limbs after surgery; 2. By rotating the positioning rod to connect it with the main and secondary scale plates, it is easy to select the appropriate incision position based on the patient's weight and the difference in the thickness of the subcutaneous tissue at the hip joint. It is also convenient to adjust the angle between the positioning rod and the main scale plate according to the inclination of the corresponding exposed surface, ensuring the consistency of the length direction of the main scale plate with the extension direction of both lower limbs to improve measurement accuracy, thereby improving the accuracy of estimating the required femoral prosthesis neck length and femoral head prosthesis size. 3. By setting up a rotating disc, a fixed disc, positioning teeth, tooth grooves, and positioning marks, it is easy to ensure the consistency of the tilt angle of the positioning rod before and after hip dislocation, thereby improving the accuracy of estimating the required femoral prosthesis neck length and femoral head prosthesis size based on the measurement results before and after hip dislocation. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the calibrator in the embodiments of this application; Figure 2 This is a front view of the main ruler and the secondary ruler in the embodiments of this application; Figure 3 This is a schematic diagram of the structure between the fixed disk and the rotating disk in an embodiment of this application. In the figure, the positioning screws do not fix the fixed disk to the driving disk. Figure 4This is a schematic diagram of the structure between the fixed disk and the rotating disk in an embodiment of this application, in which each positioning tooth is inserted into the corresponding tooth groove.

[0025] In the diagram, 1. Main scale plate; 2. Secondary scale plate; 3. Scale line; 4. Kirschner wire; 5. Screw-in rod; 6. Fixed plate; 7. Rotating plate; 8. Positioning screw; 9. Return spring; 10. Connecting part; 11. Threaded hole; 12. Gear groove; 13. Positioning tooth; 14. Positioning mark; 15. Adjustment groove; 16. Fixed screw; 17. Scale value. Detailed Implementation

[0026] In the description of this application, it should be noted that the terms "near", "away", etc. are based on the relative relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the process or module referred to must have a specific orientation, state and operation, and therefore should not be construed as a limitation of the present invention.

[0027] The present application will be further described in detail below with reference to the accompanying drawings.

[0028] Reference Figure 1 and Figure 2 This application provides a lower limb isometric calibrator for total hip arthroplasty, including a main ruler plate 1 and a secondary ruler plate 2 that overlap in the length direction. The main ruler plate 1 and the secondary ruler plate 2 are slidably connected along their respective length directions. The main ruler plate 1 and the secondary ruler plate 2 are provided with scale lines 3 that are spaced apart along the length direction. The scale lines 3 are used to reflect the total length formed by the main ruler plate 1 and the secondary ruler plate 2. Each of the opposite ends of the main ruler plate 1 and the secondary ruler plate 2 is provided with a positioning rod. The two positioning rods can be fixed on the iliac bone and the greater trochanter of the femur, respectively. Furthermore, the corresponding positioning rod is rotatably connected to the end of the main ruler plate 1 opposite to the secondary ruler plate 2, and the other positioning rod is rotatably connected to the end of the secondary ruler plate 2 opposite to the main ruler plate 1. The positioning rods are detachably connected to the main ruler plate 1 and to the secondary ruler plate 2 to fix the included angle between the positioning rod and the main ruler plate 1 and between the positioning rod and the secondary ruler plate 2 during the measurement process.

[0029] Hip replacement surgery requires dislocation of the hip joint and placement of a trial model at the dislocation site to estimate the required femoral prosthesis neck length and femoral head prosthesis size. For patients with naturally symmetrical lower limb lengths, ensuring postoperative consistency only requires maintaining the preoperative and postoperative length of each limb. However, for patients with congenital or acquired differences in lower limb length, such as those with limp, ensuring postoperative consistency requires careful intraoperative monitoring to ensure both lower limb lengths match the patient's pre-designed length, or to ensure the shorter limb matches the longer limb postoperatively. Both approaches rely on precise measurement of lower limb length. The difference between the preoperative and postoperative measurements (with trial model placement) is used to assess the required femoral prosthesis neck length and femoral head prosthesis size, ensuring postoperative lower limb length matches the preoperative design and improving overall lower limb length consistency.

[0030] The surgical procedure will now be explained using a patient who was born with symmetrical lower limb lengths as an example. Another similar case will not be described here.

[0031] Preoperatively, imaging measurements are used to estimate the distance the affected limb needs to be lengthened or shortened, in order to pre-determine the size of the trial mold to be used. Before hip dislocation, the corresponding positioning rod fixation positions, i.e., needle insertion points, are pre-determined, marked, or drilled on the patient's iliac bone and greater trochanter of the femur. Before or after the positioning rod is fixed to the human bone, the total length formed by the main scale plate 1 and the secondary scale plate 2 is adjusted so that after the positioning rod is fixed, it is easy to make the length direction of the main scale plate 1 and the secondary scale plate 2 parallel to the measurement direction of the two lower limbs, i.e., the vertical axis of the human body. At this time, the total length value formed by the main scale plate 1 and the secondary scale plate 2 is recorded.

[0032] Dislocate the hip joint and install the test mold at the dislocation site. Keep the positioning rod fixed at the needle insertion point determined before the hip joint dislocation. Readjust the total length formed by the main ruler 1 and the auxiliary ruler 2 until the length direction of the main ruler 1 and the auxiliary ruler 2 is parallel to the measurement direction of the two lower limbs, that is, the vertical axis of the human body. At this time, record the total length value formed by the main ruler 1 and the auxiliary ruler 2.

[0033] The suitability of the trial mold can be determined by subtracting the total length values ​​recorded before and after. If the total length value of the previous record is greater than that of the subsequent record, the difference is the amount by which the trial mold should be increased in size. If the total length value of the previous record is less than that of the subsequent record, the difference is the amount by which the trial mold should be decreased in size. If the total length values ​​of the two records are equal, i.e., the difference is 0, it proves that the selection of the trial mold is appropriate.

[0034] Furthermore, to facilitate surgical entry and shorten operation time, the appropriate entry point should be selected based on the patient's body size and the thickness of subcutaneous tissue at the hip joint. This entry point should be located where the subcutaneous tissue is thinner, exposing the iliac bone and greater trochanter of the femur. The iliac bone or greater trochanter of the femur at the entry point often forms an angle with the vertical axis. If this angle is too large, it will inevitably cause difficulties in fixing the positioning rod. In addition, a bone hole must be drilled at the entry point. If the angle is too large and the positioning rod is still fixed to the bone along the coronal axis, the angle between the direction of the bone hole at the entry point and the corresponding bone surface will be too small. This can lead to fragmentation or fracture of the iliac bone or greater trochanter of the femur at the entry point during measurement.

[0035] This application allows for adjustable angles between the positioning rod and the main ruler plate 1 or the secondary ruler plate 2, enabling the positioning rod to be as perpendicular as possible to the iliac bone surface or the greater trochanteric surface of the femur corresponding to the incision position, or to maximize the perpendicularity between the positioning rod and the iliac bone surface or the greater trochanteric surface of the femur corresponding to the incision position. This facilitates the arbitrary selection of the incision position before surgery. Simultaneously, it ensures the consistency of the length direction of the main ruler plate 1 and the secondary ruler plate 2 with the human coronal axis. Using the human coronal axis as a reference, this application facilitates ensuring the consistency of the length direction of the main ruler plate 1 during measurements before and after hip dislocation, thereby improving the accuracy of estimating the required femoral prosthesis neck length and femoral head prosthesis size. The direction of the human coronal axis can be determined visually or empirically.

[0036] Taking the example that there is a large deviation between the length direction of the main ruler plate 1 and the direction of the human coronal axis during the measurement process before hip dislocation, and another deviation between the main ruler plate 1 and the direction of the human coronal axis during the measurement process after hip dislocation, it will inevitably lead to the total length value formed by the main ruler plate 1 and the auxiliary ruler plate 2 being larger than the actual length value, and the deviation values ​​of the two total length values ​​are different. This will affect the accuracy of the trial mold size adjustment, and thus affect the consistency of the length of the two lower limbs after surgery.

[0037] Specifically, the main ruler plate 1 has an adjustment groove 15 extending along its own length direction. The adjustment groove 15 passes through at least one end of the main ruler plate 1 near the secondary ruler plate 2. The cross-sectional shape of the main ruler plate 1 perpendicular to its own length direction is C-shaped. The secondary ruler plate 2 is inserted into the adjustment groove 15 and can slide inside the adjustment groove 15. At least one fixing screw 16 is threadedly connected to one side of the main ruler plate 1. The end of the fixing screw 16 can be pressed against the secondary ruler plate 2 to fix the position between the secondary ruler plate 2 and the main ruler plate 1.

[0038] Reference Figure 2To facilitate doctors in reading the total length formed by the main ruler 1 and the auxiliary ruler 2, multiple scale values ​​17 are set on both the main ruler 1 and the auxiliary ruler 2. The unit of each scale value 17 is mm. These scale values ​​17 are spaced apart along the length of the main ruler 1, with the difference between adjacent scale values ​​17 being 1. The scale value 17 on the main ruler 1 gradually increases from "0" to "7" as it approaches the auxiliary ruler 2; the scale value 17 on the auxiliary ruler 2 gradually increases from "8" to "15" as it approaches the main ruler 1. When the main ruler 1 and the auxiliary ruler 2 slide to their maximum length of 15 mm, the edge of the main ruler 1 closest to the auxiliary ruler 2 aligns with the scale line 3 and the corresponding scale value 17 – "15". The total length formed by the main ruler 1 and the auxiliary ruler 2 in this state can be determined by the scale line 3 aligned with the edge of the main ruler 1 at this point and the corresponding scale value 17. Figure 2 At this point, the total length formed by the main ruler plate 1 and the secondary ruler plate 2 is approximately 12.6 mm.

[0039] Reference Figure 3 and Figure 4 Each of the main ruler plate 1 and the secondary ruler plate 2 has a fixed plate 6 at one of its opposite ends. The axis of the fixed plate 6 is perpendicular to the length of the main ruler plate 1 or the secondary ruler plate 2. The fixed plate 6 is fixed to the main ruler plate 1 or the secondary ruler plate 2 by welding, bonding or snapping, or it can be integrally formed with the main ruler plate 1 or the secondary ruler plate 2. A rotating plate 7 is set on the positioning rod and is coaxial with the fixed plate 6. A connecting part 10 is formed on the side of the rotating plate 7 opposite to the fixed plate 6. The positioning rod passes through the connecting part 10 and can drive the rotating plate 7 to rotate around the axis of the rotating plate 7 on one side of the fixed plate 6. A positioning screw 8 is coaxially set on the fixed plate 6. The positioning screw 8 passes through both the fixed plate 6 and the rotating plate 7. The head of the positioning screw 8 is located on the side of the fixed plate 6 opposite to the rotating plate 7. A threaded hole 11 is opened on the positioning rod for the positioning screw 8 to be screwed into. The axis of the threaded hole 11 is perpendicular to the axis of the positioning rod.

[0040] During the process of fixing the positioning rod to the iliac bone or the greater trochanter of the femur, the positioning rod and positioning screw 8, and the positioning rod and rotating disk 7 are disassembled from each other until the positioning rod is fixed to the human bone; then the rotating disk 7 is installed on the positioning rod, and the positioning screw 8 is screwed into the threaded hole 11 until the rotating disk 7 and the fixed disk 6 are pressed between the positioning rod and the head of the positioning screw 8; during this process, the length of the main ruler plate 1 and the auxiliary ruler plate 2 needs to be adjusted so that after the main ruler plate 1 and the auxiliary ruler plate 2 are fixed on the corresponding positioning rods, the length direction of the main ruler plate 1 is consistent with the vertical axis of the human body.

[0041] Furthermore, the fixed disk 6 has multiple toothed grooves 12 spaced apart along the circumference of the fixed disk 6 on the side near the rotating disk 7, and the rotating disk 7 has multiple positioning teeth 13 spaced apart along the circumference of the rotating disk 7 on the side near the fixed disk 6. The multiple positioning teeth 13 can be simultaneously inserted into the corresponding toothed grooves 12 to prevent rotation between the rotating disk 7 and the fixed disk 6 during the measurement process. In addition, multiple positioning marks 14 are marked on the circumference of both the rotating disk 7 and the fixed disk 6. The positioning marks 14 on the fixed disk 6 are set between two adjacent toothed grooves 12, and the positioning marks 14 on the rotating disk 7 are set between two adjacent positioning teeth 13. In this embodiment, the positioning marks 14 are in the form of numbers, that is, the numbers corresponding to the positioning marks 14 on the rotating disk 7 increase or decrease along the circumference of the rotating disk 7, and the numbers corresponding to the positioning marks 14 on the rotating disk 7 increase or decrease along the circumference of the rotating disk 7.

[0042] This facilitates knowing which tooth groove 12 each positioning tooth 13 corresponds to during measurements before hip dislocation. During measurements after hip dislocation, the sequence of previously recorded positioning marks 14 can be used to determine which tooth groove 12 each positioning tooth 13 should correspond to in this measurement. This ensures consistency in the rotation angle of the positioning rod between measurements before and after hip dislocation, and further ensures consistency between the length direction of the main ruler 1 and the vertical axis of the human body before and after hip dislocation; for example, in Figure 4 In the diagram, the positioning marks 14 on the rotating disk 7 and the fixed disk 6 are sequentially “…2-1-3-2-4-3-5…”. It is important to note that during measurements on both sides before and after hip dislocation, the positioning rod should be inserted to the bottom of the bone hole at the corresponding needle insertion point to ensure consistency in the length of the positioning rod extending beyond the bone surface during both measurements. Furthermore, the rotation angle of the positioning rod can be increased by adding more positioning teeth 13 and corresponding grooves 12.

[0043] A compressible return spring 9 is provided between the fixed disk 6 and the rotating disk 7. Both the fixed disk 6 and the rotating disk 7 have coaxially formed spring receiving grooves on their adjacent sides for the end of the return spring 9 to be inserted. During the process of tightening the positioning screw 8 to separate the fixed disk 6 and the rotating disk 7, the return spring 9 provides a spring force to separate the rotating disk 7 and the fixed disk 6, thus facilitating one-handed operation to separate the rotating disk 7 and the fixed disk 6. Furthermore, when the return spring 9 is compressed between the rotating disk 7 and the fixed disk 6, it provides preload to the threaded connection between the positioning screw 8 and the positioning rod, thereby preventing rotation during measurement.

[0044] Reference Figure 1Because the cortical bone at the greater trochanter of the femur is thin and has an irregular surface, in this embodiment, the positioning rod connected to the main scale plate 1 is a screw-in rod 5, while the positioning rod connected to the secondary scale plate 2 is a Kirschner wire 4. The end circumferential surface of the positioning rod has threads for screwing into bone holes. The Kirschner wire 4 is fixed to the greater trochanter of the femur, while the positioning rod is screwed into the iliac bone. The screw-in rod 5's insertion into the iliac bone improves the stability of the entire calibrator relative to human bone during measurement. In other embodiments, both positioning rods may be Kirschner wires 4 or both may be screw-in rods 5.

[0045] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A lower limb isometric calibrator for total hip arthroplasty, characterized in that: It includes a main ruler plate (1), a secondary ruler plate (2) and two positioning rods. The two positioning rods are fixed on the main ruler plate (1) and the secondary ruler plate (2) respectively. The secondary ruler plate (2) is slidably connected to the main ruler plate (1). Both the main ruler plate (1) and the secondary ruler plate (2) are provided with scale lines (3). The arrangement direction of the scale lines (3) is the same as the sliding direction of the secondary ruler plate (2) on the main ruler plate (1). The scale lines (3) can reflect the total length of the main ruler plate (1) and the secondary ruler plate (2). The positioning rod on the main ruler plate (1) is rotatably connected to the main ruler plate (1) and can be fixed on the main ruler plate (1). The positioning rod on the secondary ruler plate (2) is rotatably connected to the secondary ruler plate (2) and can be fixed on the secondary ruler plate (2). A fixed plate (6) is fixed on both the main ruler plate (1) and the secondary ruler plate (2). A rotating plate (7) is set on the fixed plate (6). A positioning screw (8) is threaded on the positioning rod. The positioning screw (8) passes through both the fixed plate (6) and the rotating plate (7). The head of the positioning screw (8) and the positioning rod are located on opposite sides of the rotating plate (7) and the fixed plate (6), respectively. The rotating disk (7) and the fixed disk (6) are coaxially arranged. A connecting part (10) is formed on the side of the rotating disk (7) away from the fixed disk (6). The positioning rod can drive the connecting part (10) to rotate around the axis of the rotating disk (7). The fixed disk (6) has multiple tooth grooves (12) that are spaced apart along the circumference of the fixed disk (6) on the side close to the rotating disk (7). The rotating disk (7) has multiple positioning teeth (13) that are spaced apart along the circumference of the rotating disk (7) on the side close to the fixed disk (6). Multiple positioning teeth (13) can be inserted into the corresponding tooth grooves (12) at the same time. Multiple positioning marks (14) are marked on the circumference of both the rotating disk (7) and the fixed disk (6). The positioning marks (14) on the fixed disk (6) are set between two adjacent tooth grooves (12), and the positioning marks (14) on the rotating disk (7) are set between two adjacent positioning teeth (13).

2. The lower limb isometric calibrator according to claim 1, characterized in that: A compressed return spring (9) is provided between the rotating disk (7) and the fixed disk (6).

3. The lower limb isometric calibrator according to claim 1, characterized in that: One of the positioning rods uses a Kirschner wire (4), and the other positioning rod uses a screw rod (5). The screw rod (5) has threads on its circumference.

4. The lower limb isometric calibrator according to claim 1, characterized in that: The length direction of the main ruler plate (1) is the same as that of the secondary ruler plate (2). The main ruler plate (1) has an adjustment groove (15) for the secondary ruler plate (2) to be inserted. The secondary ruler plate (2) can slide inside the adjustment groove (15). The main ruler plate (1) is provided with fixing screws (16) for fixing the secondary ruler plate (2) to the main ruler plate (1).

5. The lower limb isometric calibrator according to claim 4, characterized in that: Both the main ruler (1) and the secondary ruler (2) are marked with scale values ​​(17). The numbers corresponding to the scale values ​​(17) on the main ruler (1) gradually increase as they approach the secondary ruler (2), and the numbers corresponding to the scale values ​​(17) on the secondary ruler (2) gradually increase as they approach the main ruler (1). The largest number corresponding to the scale values ​​(17) on the main ruler (1) is smaller than the smallest number corresponding to the scale values ​​(17) on the secondary ruler (2).

Images