Lower limb length measuring method and system in hip replacement

Abstract

The invention discloses a lower limb length measuring method in hip replacement, which comprises the following steps: S1, respectively fixing reflective structures on one side of a pelvis and one side of a femur of an affected limb, and adjusting the position of a camera; s2, the affected limb is adjusted according to the spherical motion, and dynamic space coordinates of all the mark points under the world coordinate system at different moments are obtained; s3, establishing a reference coordinate system by adopting the spatial position information of the mark points on one side of the pelvis, and acquiring a sphere center coordinate and a sphere radius which are fitted before an operation; s4, after the prosthesis is replaced in the operation, the affected limb is adjusted, the rotation center of the prosthesis is determined, and the prosthesis is adjusted according to the sphere center coordinate fitted before the operation, so that the prosthesis and the prosthesis are aligned until the rotation center of the prosthesis coincides with the rotation center of the hip before the operation; s5, the length from the mark point on one side of the femur to the rotation center of the prosthesis is calculated and serves as a new spherical radius, the difference value of the new spherical radius and the spherical radius fitted before the operation serves as the lower limb length variation, and the lower limb length variation is dynamically adjusted.

Description

Technical Field

[0001] The present invention relates to the technical field of hip replacement, and in particular to a method and system for measuring the length of lower limbs in hip replacement. Background Art

[0002] Hip replacement is one of the most common orthopedic surgeries. It uses an artificial hip prosthesis to replace the hip joint with terminal disease or damage. Total hip replacement has the characteristics of high incidence, high disability rate and difficult judgment during surgery for unequal length of lower limbs.

[0003] During surgery, doctors usually use empirical estimates, tape measure or laser distance measurement to determine the length of the affected limb to avoid complications of unequal length of the lower limbs. However, due to the uncertainty of the measurement point, changes in the position of the hip joint and poor repeatability of the method, these measurement methods have large measurement errors, making it difficult for doctors to make accurate assessments based on the measurement results. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned background technical problems and to provide a method and system for measuring the length of lower limbs in hip replacement surgery.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for measuring the length of lower limbs in hip replacement surgery, comprising:

[0007] S1. Fix reflective structures on the pelvic side and femoral side of the affected limb to form multiple marking points, and adjust the position of the camera so that the reflective structure is within the field of view of the camera;

[0008] S2, presetting a spherical motion of the thigh around the femoral head, adjusting the affected limb according to the spherical motion, and collecting spatial position information of all the marking points during the entire motion time through a camera to obtain dynamic spatial coordinates of all the marking points at different times in a world coordinate system;

[0009] S3, analyzing the spatial position information of the marker points collected by the camera, and using the spatial position information of the marker points on one side of the pelvis to establish a reference coordinate system;

[0010] According to the conversion relationship from the world coordinate system to the reference coordinate system, the spatial coordinates of the marking points on one side of the femur are converted to the reference coordinate system, and the spherical trajectory of the movement of the marking points is fitted using the least squares method to obtain the fitted spherical center coordinates and spherical radius, and the spherical center coordinates are approximately the hip rotation center coordinates;

[0011] Record the coordinates of the sphere center and the sphere radius fitted before surgery;

[0012] S4. After replacing the prosthesis during surgery, adjust the affected limb, determine the prosthesis rotation center, and adjust the prosthesis according to the preoperative fitted spherical center coordinates to align the two until the prosthesis rotation center coincides with the preoperative hip rotation center;

[0013] S5. After the rotation center of the prosthesis is determined, the length from the marked point on one side of the femur to the rotation center of the prosthesis is calculated. This length is used as the new spherical radius of the spherical motion of the lower limb after the prosthesis is replaced. The difference between the new spherical radius and the preoperative fitted spherical radius is the change in the length of the lower limb.

[0014] Adjust the length of the femoral stem and calculate the length from the marked point on one side of the femur to the rotation center of the prosthesis in real time to dynamically adjust the change in the length of the lower limb.

[0015] As a further scheme of the present invention: in S2, the method for adjusting the affected limb includes: presetting an angle range, an abduction angle range, and an adduction angle range, and in a lying state, lifting the sole of the affected limb in a vertical direction to flex the lower limb forward until the angle between the lower limb and the horizontal plane is within the angle range, forming a flexion angle, maintaining the flexion angle, adjusting the lower limb so that it is within the abduction angle range and the adduction angle range, abducting and adducting, and finally straightening the lower limb.

[0016] As a further solution of the present invention: in S1, the spatial arrangement of the multiple marking points on one side of the pelvis and the multiple marking points on one side of the femur are different, and preoperative registration can be used to distinguish the marking points formed by different reflective structures during surgery.

[0017] As a further solution of the present invention: in S2, when adjusting the affected limb, the dynamic spatial coordinates of the marking point are the data points of the movement of the pelvis being displaced by the movement of the thigh, and the data points of the spherical movement of the thigh around the femoral head.

[0018] A lower limb length difference measurement system in hip replacement surgery is suitable for the measurement method, comprising: a reflective structure and a calculation unit; the reflective structure is provided with two, namely a first reflective member and a second reflective member, the reflective structure comprises a plurality of reflective marker balls, and the reflective marker balls are used to uniformly reflect visible light and near-infrared light; the calculation unit comprises an acquisition module, the acquisition module is used to acquire real-time video image data of the lower limbs and collect the spatial position coordinates of the reflective marker balls on the affected limb; the acquisition module is connected to a data processing module, the data processing module receives the spatial position coordinates transmitted from the acquisition module, and performs analysis and processing to generate processing data; the data processing module is connected to a display module, the display module receives the processing data transmitted from the data processing module and the video image data transmitted from the acquisition module, and visualizes them.

[0019] As a further solution of the present invention: the sizes of the plurality of reflective marking balls are the same, and the centers of the plurality of reflective marking balls in the same reflective structure are located in the same plane and are not collinear.

[0020] As a further solution of the present invention: the reflective structure includes a fixing frame, the fixing frame is detachably connected to a plurality of reflective marking balls, and the fixing frame is connected to the bone screws.

[0021] As a further solution of the present invention: the reflective marker balls on the first reflective member and the reflective marker balls on the second reflective member are arranged differently in space.

[0022] Beneficial effects of the present invention:

[0023] (1) In the present invention, a method for measuring the length of the lower limbs during hip replacement surgery is used, which can detect changes in the hip rotation center and the length of the affected limb of the patient before and during the hip replacement surgery, thereby reducing measurement errors and facilitating doctors to make better evaluations during the debugging stage after the implantation of the biological femoral prosthesis.

[0024] (2) In the present invention, the pelvis and the femoral head may be displaced due to the movement of the femur. The reference coordinate system is established based on the spatial position information of the marking points on one side of the pelvis. The spherical fitting of all spherical motion trajectory points is in the reference coordinate system, thus shielding the influence of pelvic displacement. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below in conjunction with the accompanying drawings.

[0026] Figure 1 is a flow chart of a method for measuring the length of lower limbs in hip replacement surgery of the present invention;

[0027] Figure 2 It is a flow chart of the lower limb length difference measurement system in hip replacement surgery of the present invention during a specific application process;

[0028] Figure 3 is a schematic diagram of a calculation unit in a lower limb length difference measurement system in hip replacement surgery of the present invention;

[0029] Figure 4 is a schematic diagram of a reflective structure in a lower limb length difference measurement system in hip replacement surgery of the present invention;

[0030] Figure 5 This is a top view of the lower limb length difference measurement performed using the lower limb length difference measurement system in hip replacement surgery.

[0031] In the figure:

[0032] 1. First reflector; 2. Second reflector; 3. Binocular camera; 4. Fixing bracket; 5. Reflective marker ball; 6. Bone screw. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] See also Figure 3-Figure 5 As shown, the present invention is a lower limb length difference measurement system in hip replacement surgery, including: a reflective structure and a calculation unit.

[0035] For details, please refer to Figure 4-Figure 5 As shown, there are two reflective structures, namely a first reflective member 1 and a second reflective member 2. The reflective structure includes a fixing frame 4, and the fixing frame 4 is detachably connected with a plurality of reflective marker balls 5, and the reflective marker balls 5 are used to uniformly reflect visible light and near-infrared light. The detachable connection mode facilitates the operator to replace the reflective marker balls 5 according to actual needs.

[0036] The fixing frame 4 is also connected to a bone screw 6, which is fixed to the fixing frame 4. By rigidly connecting the bone screw 6 to the pelvic side and the femur side of the affected limb, the first reflector 1 is installed on the pelvis and the second reflector 2 is installed on the femur.

[0037] The reflective marker balls 5 on the first reflector 1 and the reflective marker balls 5 on the second reflector 2 are arranged differently in space. The reflective marker balls 5 have the same size, and the centers of the reflective marker balls 5 in the same reflective structure (the first reflector 1 or the second reflector 2) are located in the same plane and are not collinear.

[0038] See also Figure 3 , Figure 5 As shown, the computing unit includes a collection module, and the collection module includes a camera, and the camera is a binocular camera 3. The collection module collects real-time video image data of the lower limbs and collects the spatial position coordinates of the reflective marker ball 5 on the affected limb through the binocular camera 3.

[0039] The acquisition module is connected to the data processing module, and the data processing module receives the spatial position coordinates transmitted from the acquisition module, performs analysis and processing, and generates processed data.

[0040] The data processing module is connected to the display module. The display module receives the processed data transmitted from the data processing module and the video image data transmitted from the acquisition module, and visualizes them.

[0041] See also Figure 5 As shown, in this embodiment, when in use, the first reflector 1 and the second reflector 2 are respectively mounted on the pelvis and the femur of the affected limb of the patient, and are rigidly connected by the bone screw 6. After the bone screw 6 is fixed, the patient lies flat, so that all the reflective marker balls 5 on the first reflector 1 and the second reflector 2 are facing the side of the binocular camera 3 and are always kept in the field of view of the binocular camera 3.

[0042] See also Figure 1-Figure 2 As shown, the present invention is a method for measuring the length of lower limbs in hip replacement surgery, comprising:

[0043] S1. Fix reflective structures on the pelvis side and the femur side of the affected limb to form multiple marking points, and adjust the position of the binocular camera 3 so that the reflective structure is within the field of view of the camera.

[0044] Specifically, the first reflector 1 and the second reflector 2 are fixed to the pelvis and femur of the affected limb, respectively, and each reflective marker ball 5 is used as a marking point, and the reflective marker balls 5 on the first reflector 1 and the second reflector 2 form a plurality of marking points. When the spatial positions of the reflective marker balls 5 on the first reflector 1 and the second reflector 2 are determined, the position of the binocular camera 3 is adjusted to ensure that all the reflective marker balls 5 are always within the field of view of the binocular camera 3.

[0045] Generally, the first reflector 1 is installed on the pelvis, close to the affected limb, the reflective marker ball 5 on the first reflector 1 faces the binocular camera 3 and away from the surgical access area, and the second reflector 2 is installed on the femur of the affected limb, and the reflective marker ball 5 on the second reflector 2 faces the binocular camera 3.

[0046] Since the spatial arrangement of the reflective marking balls 5 on the first reflective element 1 and the second reflective element 2 is different, the spatial arrangement of the multiple marking points on the pelvis side and the multiple marking points on the femur side is also different. Preoperative registration can be used to distinguish the marking points formed by different reflective structures during surgery.

[0047] S2. Preset a spherical motion of the thigh around the femoral head, adjust the affected limb according to the spherical motion, and collect the spatial position information of all marking points during the entire motion time through the binocular camera 3 to obtain the dynamic spatial coordinates of all marking points at different times in the world coordinate system and record them.

[0048] When the patient lies flat, the thigh moves around the femoral head, so that the movement trajectory of the second reflective element 2 on the femoral head is a spatial sphere rather than a plane. This movement process is a spherical movement.

[0049] The method for adjusting the affected limb includes: first presetting the angle range, the abduction angle range, and the adduction angle range. In the present embodiment, the preset angle range is greater than or equal to 40°, and the abduction angle range and the adduction angle range are both greater than or equal to 20°. Then, when the patient is lying flat, the doctor or the operator in the operation holds the sole of the patient's affected limb and slowly lifts it in the vertical direction to flex the lower limb until the angle between the lower limb and the horizontal plane is within the angle range, forming a flexion angle. Then maintain the flexion angle, abduct and adduct the lower limb, and the abduction and adduction angles are not less than 20°, and finally return the lower limb to the correct position. It should be noted that during the process of returning the lower limb to the correct position, the lower limb can be operated so that it descends while abducting and then adducting. The spatial position of the reflective marker ball 5 during the entire movement of the lower limb is acquired by the binocular camera 3.

[0050] When adjusting the affected limb, the dynamic spatial coordinates of the marking points are the data points of the movement of the pelvis being displaced by the thigh movement and the data points of the thigh making a spherical movement around the femoral head. These data points are represented by the coordinate points of the reflective marking balls 5 on the first reflector 1 and the second reflector 2, respectively.

[0051] S3. Analyze the spatial position information of the marking points collected by the binocular camera 3, and use the spatial position information of the marking points on one side of the pelvis to establish a reference coordinate system (i.e., use the marking points of the reflective marking ball 5 on the first reflector 1 as a reference to establish a new coordinate system). According to the conversion relationship from the world coordinate system to the reference coordinate system, convert the spatial coordinates of the marking points on one side of the femur to the reference coordinate system, and use the least squares method to fit the spherical trajectory of the marking point movement to obtain the fitted spherical center coordinates and spherical radius, which are approximately the coordinates of the hip rotation center. Record the preoperative fitted spherical center coordinates and spherical radius.

[0052] Specifically, the spatial positions of all the acquired marking points are analyzed, that is, the height h of the hip rotation center is obtained through the spatial position coordinates of all the reflective marking balls 5. i The straight-line distance from the marked point on the femur to the femoral head is l i .

[0053] The following steps are also included:

[0054] S301 , distinguishing two reflective elements, namely the first reflective element 1 and the second reflective element 2 , according to the spatial distribution characteristics of the reflective marker ball 5 .

[0055] S302: The binocular camera 3 of the acquisition module calculates the number N of the identified reflective elements in real time.

[0056] S303: Determine whether the number N of reflective elements is equal to 2.

[0057] S304: If N is not equal to 2, an error needs to be reported, that is, the reflective element has lost tracking, and the process returns to S302.

[0058] S305. If N is equal to 2, obtain data through the data processing module to record the spatial dynamic coordinate data (in the world coordinate system O0) of all reflective marker balls 5 on the first reflective element 1 and the second reflective element 2 at different times t during the entire time of lower limb adjustment.

[0059] Specifically, the reflective marking balls 5 on the first reflective element 1 are marked as group A, and the reflective marking balls 5 on the second reflective element 2 are marked as group B.

[0060] When the second reflective member 2 on the femur moves with the thigh, its movement trajectory is a spherical surface with the femoral head as the sphere center. The theoretical sphere center S of the femoral head can be obtained by performing spatial spherical fitting on the spatial position data (no less than 4 data and not coplanar) of a reflective marker ball 5 on the second reflective member 2. t In fact, the movement of the thigh will inevitably cause the pelvis to move. Since the pelvis and femoral head are closely connected, the theoretical center of the femoral head S t will change, thus affecting the fitting results of spatial spherical data.

[0061] In order to reduce the error, a reference coordinate system O is established on the pelvis. R In this coordinate system, the position of the femoral head remains unchanged. Reference coordinate system O R The reflective marker ball 5 near the ilium is used as the basis to ensure that the reference coordinate system O R The number of available marker points in group A should be ≥ 3. Theoretically, only one reflective marker ball 5 is needed on the thigh to fit the theoretical sphere center S t .

[0062] S306, randomly extract the coordinate data of the reflective marker ball 5 in group A, record them as A1, A2 and A3 respectively, and use these three coordinate points to establish a new reference coordinate system. R , calculate the new reference coordinate system O at all times R The transformation matrix T between the world coordinate system O0 OR . New reference coordinate system O R Always take A1 as the origin and the direction of vector A1 A2 as x OR Axis, the direction of the plane normal vector formed by A1, A2 and A3 is z OR Axis, according to the right-hand rule, for x OR Axis and z OR Axis cross product to get y OR Axis. As shown below:

[0063]

[0064] S307, randomly select a coordinate point B1 of a reflective marker ball 5 in group B. At time t, the coordinate of point B1 in the world coordinate system O0 is b t1-oxyz , through the transformation matrix T OR Convert the coordinates of point B1 at the corresponding time to the new reference coordinate system O R , get the new coordinate b t1-rxyz , that is: b t1-rxyz =T OR -1 ·(P O0 -A1).

[0065] S308, setting fitting threshold E s and E L The size of the threshold determines the size of the final fitting error, and then the least squares method is used to fit all points b t1-rxyz The center S of the sphere 1-rxyz , and calculate the sphere center fitting error E1, and then obtain the sphere radius L1 and the sphere radius error E2.

[0066] Assume point b t1-rxyz There are N spheres, namely rxyzi, and we need to find a sphere center S 1-rxyz Minimize the sum of the squares of the distances from all points to the center of the sphere. At this time, the goal of the least squares method is to minimize the residual sum of squares, that is:

[0067] The sphere center S is obtained by fitting 1-rxyz Then, fit the sphere radius L1. Assume that point S 1-rxyz In the new reference coordinate system O R Determine, find a sphere radius L1 so that the sum of the squares of the differences between the distances of all points to the center of the sphere and L1 is minimized. That is:

[0068] S309, after fitting errors E1 and E2 are obtained, determine E s Whether ≥ E1 and E l Is ≥ E2? If the result is no, that is, the fitting error is greater than the threshold, then re-execute from S305 in order, re-randomly extract the coordinate data of the three reflective marker balls 5 in group A, and re-select the coordinate data of the reflective marker ball 5 in group B. Use the new data to re-fit to obtain the ideal fitting value.

[0069] Fitting threshold E s and E L The default value is e s and e l , using the default value, the final fitting error is strictly less than 5mm, E s and E LThe value can be adjusted appropriately according to the doctor's needs to reduce the strict error to 4mm, 3mm, 2mm or smaller. It should be noted that a smaller threshold will increase the system calculation time and fail to fit effectively, so it needs to be adjusted based on the actual situation.

[0070] S309, E of judgment s Whether ≥ E1 and E l Is it ≥ E2? The result is true, that is, the fitting error is less than the threshold, and the fitting result is valid. The radius L1 and the coordinates of the center of the ball are recorded as S. 1-rxyz data.

[0071] S4. After replacing the prosthesis during surgery, adjust the affected limb, determine the prosthesis rotation center, and adjust the prosthesis according to the preoperative fitted spherical center coordinates to align the two until the prosthesis rotation center coincides with the preoperative hip rotation center.

[0072] Method for aligning the prosthesis rotation center and the preoperatively fitted spherical center coordinates: After the prosthesis is installed, shake the lower limb (adjust the affected limb again), fit the prosthesis rotation center, and the distance from the second reflector 2 on the femur side to the prosthesis rotation center is temporarily set as the prosthesis length. At this time, the prosthesis, femur and the second reflector 2 on one side of the femur form a rigid tool. The spatial rotation and displacement of the second reflector 2 will also be characterized on all components of the rigid tool. The real-time position of the prosthesis ball head can be determined by tracking the displacement and rotation of the second reflector 2 in space, which is convenient for doctors to align.

[0073] S5. After the rotation center of the prosthesis is determined, the length from the marked point on one side of the femur to the rotation center of the prosthesis is calculated. This length is used as the new spherical radius of the spherical motion of the lower limb after replacing the prosthesis. The difference between the new spherical radius and the preoperative fitted spherical radius is the change in the length of the lower limb.

[0074] Then adjust the length of the femoral stem and calculate the length from the marked point on one side of the femur to the rotation center of the prosthesis in real time to dynamically adjust the change in the length of the lower limb.

[0075] Specifically, the hip rotation center height h obtained before and during surgery i The straight-line distance from the marked point on the femur to the femoral head is l i Subtract and get the height difference h of the hip rotation center x Difference in length between lower limbs x According to h x With l x Determine the change in the position of the lower limb hip rotation center and the length of the femoral prosthesis neck after prosthesis implantation. Based on this, the doctor can perform a trial mold during surgery and replace the liner and the appropriate head and neck during the prosthesis debugging stage, thereby adjusting the hip rotation center and femoral length, and reducing the length change of the affected limb before and after surgery.

[0076] In the present application, the lower limb length measurement method and system in hip replacement surgery mentioned above are used to detect the changes in the hip rotation center and the length of the affected limb of the patient before and during the hip replacement surgery. During the debugging stage after the implantation of the biological femoral prosthesis, it is convenient for the doctor to conduct a better evaluation to select a suitable head and neck trial mold, and install a prosthesis stem and femoral head prosthesis of the appropriate size, which effectively reduces the postoperative length change of the patient's affected limb, thereby avoiding the occurrence of complications of unequal length of both lower limbs.

[0077] The inventors have found that imaging measurements in the prior art are also used in intraoperative lower limb length measurements, namely, standard pelvic plain film measurements and CT measurements, etc. However, the surgery is usually performed in the lateral position, and it is impossible to accurately determine whether the patient is in the standard lateral position and measure whether there is micro-movement in the front and back positions during the surgery. Since this method requires imaging during the surgery, it also prolongs the operation time and increases the potential risk of infection.

[0078] In addition, surgical robots are used in the field of hip replacement in the existing technology. They combine computer navigation with more precise robotic arms to perform modeling and surgical planning before surgery. In theory, they can implant the prosthesis in a more ideal position, but they still cannot fundamentally avoid the intraoperative lower limb length measurement errors caused by changes in body position and three-dimensional movement of the hip joint. The introduction of surgical robots has lengthened the surgical preparation cycle and increased the cost of surgery, making it difficult to promote them across the board.

[0079] In the present invention, the coordinate trajectory of the second reflector 2 is a sphere. Affected by the movement of the femur, the pelvis and the femoral head may be displaced. The reference coordinate system is established based on the spatial position information of the marking points on one side of the pelvis (i.e., the marking points of the reflective marking ball 5 on the first reflector 1 are used as reference to establish a new coordinate system). The spherical fitting of all spherical motion trajectory points is in the reference coordinate system, which shields the influence of pelvic displacement.

[0080] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the claims of the present invention.

Claims

1. A method for measuring the length of lower limbs in hip replacement surgery, characterized in that: include: S1. Fix reflective structures on the pelvic side and femoral side of the affected limb to form multiple marking points, and adjust the position of the camera so that the reflective structure is within the field of view of the camera; S2, presetting a spherical motion of the thigh around the femoral head, adjusting the affected limb according to the spherical motion, and collecting spatial position information of all the marking points during the entire motion time through a camera to obtain dynamic spatial coordinates of all the marking points at different times in a world coordinate system; S3, analyzing the spatial position information of the marker points collected by the camera, and using the spatial position information of the marker points on one side of the pelvis to establish a reference coordinate system; According to the conversion relationship from the world coordinate system to the reference coordinate system, the spatial coordinates of the marking points on one side of the femur are converted to the reference coordinate system, and the spherical trajectory of the movement of the marking points is fitted using the least squares method to obtain the fitted spherical center coordinates and spherical radius, and the spherical center coordinates are approximately the hip rotation center coordinates; Record the coordinates of the sphere center and the sphere radius fitted before surgery; S4. After replacing the prosthesis during surgery, adjust the affected limb, determine the prosthesis rotation center, and adjust the prosthesis according to the preoperative fitted spherical center coordinates to align the two until the prosthesis rotation center coincides with the preoperative hip rotation center; S5. After the rotation center of the prosthesis is determined, the length from the marked point on one side of the femur to the rotation center of the prosthesis is calculated. This length is used as the new spherical radius of the spherical motion of the lower limb after the prosthesis is replaced. The difference between the new spherical radius and the preoperative fitted spherical radius is the change in the length of the lower limb. Adjust the length of the femoral stem and calculate the length from the marked point on one side of the femur to the rotation center of the prosthesis in real time to dynamically adjust the change in the length of the lower limb.

2. The measuring method according to claim 1, characterized in that: In S2, the method for adjusting the affected limb includes: presetting an angle range, an abduction angle range, and an adduction angle range, and in a lying state, lifting the sole of the affected limb in a vertical direction to flex the lower limb forward until the angle between the lower limb and the horizontal plane is within the angle range, forming a flexion angle, maintaining the flexion angle, adjusting the lower limb so that it is within the abduction angle range and the adduction angle range, abducting and adducting, and finally straightening the lower limb.

3. The measuring method according to claim 1, characterized in that: In the S1, the spatial arrangement of the multiple marking points on the pelvis side and the multiple marking points on the femur side is different, and preoperative registration can be used to distinguish the marking points formed by different reflective structures during surgery.

4. The measuring method according to claim 1, characterized in that: In S2, when the affected limb is adjusted, the dynamic spatial coordinates of the marking points are the data points of the movement of the pelvis being displaced by the movement of the thigh, and the data points of the spherical movement of the thigh around the femoral head.

5. A system for measuring the difference in length of lower limbs in hip replacement surgery, applicable to the measurement method according to any one of claims 1 to 4, characterized in that: include: Reflective structure and computing unit; The reflective structure is provided with two, namely a first reflective member (1) and a second reflective member (2), and the reflective structure comprises a plurality of reflective marker balls (5), and the reflective marker balls (5) are used to uniformly reflect visible light and near-infrared light; The computing unit comprises a collection module, which is used to collect real-time video image data of the lower limbs and collect the spatial position coordinates of the reflective marker ball (5) on the affected limb; The acquisition module is connected to the data processing module, and the data processing module receives the spatial position coordinates transmitted from the acquisition module, performs analysis and processing, and generates processing data; The data processing module is connected to the display module, and the display module receives the processed data transmitted from the data processing module and the video image data transmitted from the acquisition module, and visualizes them.

6. The measuring system according to claim 5, characterized in that: The sizes of the plurality of reflective marking balls (5) are the same, and the centers of the plurality of reflective marking balls (5) in the same reflective structure are located in the same plane and are not collinear.

7. The measuring system according to claim 5, characterized in that: The reflective structure comprises a fixing frame (4), the fixing frame (4) is detachably connected to a plurality of reflective marking balls (5), and the fixing frame (4) is connected to a bone screw (6).

8. The measuring system according to claim 5, characterized in that: The spatial arrangement of the reflective marker balls (5) on the first reflective member (1) and the reflective marker balls (5) on the second reflective member (2) is different.

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