A motion planning and application method for tibial fracture healing and functional rehabilitation

Abstract

A motion planning and application method for tibial fracture healing and functional rehabilitation, comprising the following contents: step 1, obtaining a CT image simultaneously including the tibia, the Kirschner wire, and the outer ring fixer fixed to the tibia by the Kirschner wire; step 2, performing three-dimensional reconstruction of the tibia installed with the outer ring fixer according to the CT image and the patient's physiological information; step 3, establishing a bone section coordinate system, a fixed coordinate system for the proximal fixed platform of the outer ring fixer, and a dynamic coordinate system for the distal dynamic platform of the outer ring fixer on the bone section according to the three-dimensionally reconstructed model; step 4, transforming the rehabilitation motion based on the bone section coordinate system to the fixed coordinate system based on the proximal fixed platform of the outer ring fixer: step 5, performing inverse kinematics solution on the motion of the bone section in the fixed coordinate system to obtain the motion of the upper branch of the outer ring fixer. The present invention can apply targeted motion stimulation to different postoperative tibial fixation states and bone section postures.

Description

Technical Field

[0001] The invention relates to an exoskeleton rehabilitation training method, and in particular to a motion planning and application method for tibial fracture healing and functional rehabilitation. Background Art

[0002] The tibia is located between the knee and ankle joints. Tibia fractures are prone to occur when they are hit by external forces, fall from heights, or during strenuous exercise. Tibia fractures are one of the most common fractures and a multiple disease. The time and effect of tibial fracture healing directly affect the patient's daily life. Long-term rest will not only affect the patient's life for a long time, but also easily cause sequelae such as muscle atrophy, delayed healing or non-healing. Studies have shown that applying intermittent micro-motion stimulation to the fracture site can promote the formation and calcification of the early external callus of the fracture, improve the stiffness of fracture healing, and shorten the fracture healing time.

[0003] The position and posture of the fracture section in space in tibial fractures are complex and diverse, and the relative position of the external fixation ring and the human tibia during fracture surgery is not unique. Applying motion stimulation without considering the fixation status of the fracture surgery and the spatial posture of the fracture section may hinder fracture healing and even cause secondary fractures. Therefore, combining the spatial posture of the bone section in the actual fracture healing process to carry out motion planning and apply corresponding stimulation is one of the key factors to promote normal fracture healing and reduce complications. At present, the application of stimulation to promote tibial healing is mostly carried out by doctors through rehabilitation training, which often relies on a lifetime of experience. So far, there is no clear planning and application method for quantitative application of movement in the early stage after tibial fracture surgery. Therefore, combined with the postoperative tibial fixation status and the spatial posture of the bone section, targeted motion planning and stimulation application is an important means to promote efficient tibial healing. Summary of the invention

[0004] The present invention overcomes the shortcomings of the prior art and provides a motion planning and application method for tibial fracture healing and functional rehabilitation. The method can apply targeted motion stimulation to different postoperative tibial fixation states and bone section positions through scanning modeling, spatial transformation, and kinematic solution.

[0005] A motion planning and application method for tibial fracture healing and functional rehabilitation, including the following contents:

[0006] Step 1: Perform a CT scan on the lower leg of a patient who has undergone fracture fixation surgery and installed a six-axis parallel external ring fixator, and obtain a CT image that includes the tibia, the Kirschner wire, and the external ring fixator fixed to the tibia through the Kirschner wire;

[0007] Step 2: Perform three-dimensional reconstruction of the tibia with the external ring fixator installed according to the CT image and the patient's physiological information, obtain a three-dimensional geometric model of the tibia and determine the relative position relationship between the external ring fixator, the Kirschner wire and the tibia;

[0008] Step 3: establishing a bone section coordinate system at the bone section, a fixed coordinate system for the proximal fixed platform of the outer ring fixator, and a dynamic coordinate system for the distal dynamic platform of the outer ring fixator according to the three-dimensional reconstructed model;

[0009] Step 4: Transform the rehabilitation motion based on the bone section coordinate system to the fixed coordinate system of the proximal fixed platform based on the outer ring fixator:

[0010] Step 5: Perform inverse kinematics on the movement of the bone section in the fixed coordinate system to obtain the movement of the branch chain on the outer ring fixator, convert the movement of the branch chain into motor input information, and control the motor to drive the outer ring fixator to complete the rehabilitation movement.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] The method of the present invention obtains motion input information through scanning modeling, spatial transformation, and kinematic solution in combination with the patient's physiological information, and the input signal implements tibial rehabilitation exercise. The present invention can apply targeted motion stimulation to different postoperative tibial fixation states and bone section postures, and has universal applicability.

[0013] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments: BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a flowchart of the motion planning and application method for tibial fracture healing and functional rehabilitation of the present invention;

[0015] Figure 2 It is a schematic diagram of three-dimensional reconstruction of the tibia and the six-axis parallel external ring fixator of the present invention;

[0016] Figure 3 It is a schematic diagram of the interconnected structure of the tibia, the Kirschner wire and the external ring fixator;

[0017] Among them: 1- proximal end of tibia; 2- distal end of tibia; 3- Kirschner wire; 4- motor; 5- universal joint; 6- ball screw; 7- distal moving platform; 8- proximal fixed platform;

[0018] Figure 4 Create a method diagram for the coordinate system;

[0019] Wherein: 9-x-axis of fixed coordinate system A, 10-y-axis of fixed coordinate system A, 11-z-axis of fixed coordinate system A, 12-x-axis of bone section coordinate system H, 13-z-axis of bone section coordinate system H, 14-x-axis of moving coordinate system B, 15-y-axis of moving coordinate system B, 16-z-axis of moving coordinate system B;

[0020] Figure 5Flow chart of the process for implementing exercise for rehabilitation.

[0021] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0022] like Figure 1 As shown, a motion planning and application method for tibial fracture healing and functional rehabilitation in this embodiment:

[0023] Step 1: Perform a CT scan on the lower leg of a patient who has undergone fracture fixation surgery and installed a six-axis parallel external ring fixator to obtain a CT image that includes the tibia 20, the Kirschner wire, and the external ring fixator fixed to the tibia 20 through the Kirschner wire 3;

[0024] Step 2: Perform three-dimensional reconstruction of the tibia with the external ring fixator installed according to the CT image and the patient's physiological information, obtain a three-dimensional geometric model of the tibia and determine the relative position relationship between the external ring fixator, the Kirschner wire 3 and the tibia 20; the reconstructed three-dimensional model is as follows: Figure 2 As shown;

[0025] In this step, the CT image data is imported into the medical processing software for three-dimensional reconstruction, the three-dimensional geometric model of the tibia is obtained, and the relative position relationship between the outer ring fixator, the Kirschner wire 3 and the tibia 20 is determined. By calling the patient's age, gender, height, and weight physiological information, the material parameters such as tibia density, Poisson's ratio, and elastic modulus are matched and assigned.

[0026] Step 3: establishing a bone section coordinate system H at the bone section, a fixed coordinate system A by the proximal fixed platform 8 of the outer ring fixator, and a dynamic coordinate system B by the distal dynamic platform 7 of the outer ring fixator according to the three-dimensional reconstructed model;

[0027] like Figure 3 and Figure 4 As shown, further, in this step, the broken bone section fixed with the distal moving platform of the outer ring fixator is fitted into a plane by three-dimensional software and the centroid is determined, and the bone section coordinate system H is established with the centroid as the origin, and the fixed coordinate system A is established with the centroid of the proximal fixed platform 8 of the outer ring fixator and the dynamic coordinate system B is established with the centroid of the distal moving platform 7 of the outer ring fixator. Each coordinate system is as shown in FIG. Figure 4 shown.

[0028] Step 4: transform the rehabilitation motion based on the bone section coordinate system H to the fixed coordinate system A based on the proximal fixed platform 8 of the outer ring fixator:

[0029] Furthermore, the motion transformation is a spatial transformation. First, the material properties of the patient's tibia are matched with the patient's biological information to obtain the Young's modulus of the patient's corresponding healing tissue. The linear strain △L under a certain stress stimulus can be solved by the Young's modulus to determine the spatial displacement of the bone section in the bone section coordinate system. H P, where || H P||=△L;

[0030] Secondly, the displacement based on the bone section coordinate system H H P is transformed into the moving coordinate system B, and the motion in the moving coordinate system B is obtained. B P, where B P= B T H H P;

[0031] Then, the spatial displacement based on the moving coordinate system B B P is transformed into the fixed coordinate system A, and the motion in the fixed coordinate system is obtained A P, where A P= A T B B P;

[0032] in, || B P OH || is the distance between the origin of the bone section coordinate system H and the origin of the moving coordinate system B, B R H is the rotation matrix of the bone section coordinate system H relative to the moving coordinate system B; || A P OB || is the distance between the origin of the moving coordinate system B and the origin of the fixed coordinate system A, A R B is the rotation matrix of the moving coordinate system relative to the fixed coordinate system.

[0033] Step 5: Perform inverse kinematics on the movement of the bone section in the fixed coordinate system A to obtain the movement of the branch chain on the outer ring fixator, convert the movement of the branch chain into motor input information, and control the motor to drive the outer ring fixator to complete the rehabilitation movement.

[0034] Furthermore, in this step, the motion in the fixed coordinate system A is AP performs inverse kinematics to obtain the length changes of the six branches of the six-axis parallel external fixator (the branches in this embodiment are the general term for the construction of the universal joint 5 and the ball screw 6), and converts the length change information of the branches (such as position, speed, etc.) into motor angle or speed information, which is input as a motion input signal into the motor (such as a motor controller) to realize the rehabilitation movement of the distal end of the tibia driven by the external ring fixator in space. In this step, the input signal implements the tibial rehabilitation movement such as Figure 5 shown.

[0035] Example

[0036] Combination Figure 1-Figure 5 Taking a short oblique fracture line in space as an example, the technical solution of the present invention is further described:

[0037] Step 1: Perform a CT scan on the lower leg of a patient who has undergone fracture fixation surgery and installed a six-axis parallel external ring fixator, and obtain a CT image that includes the tibia, the Kirschner wire, and the external ring fixator fixed to the tibia through the Kirschner wire;

[0038] Step 2: Perform three-dimensional reconstruction of the tibia with the external ring fixator installed according to the CT image and the patient's physiological information, obtain a three-dimensional geometric model of the tibia and determine the relative position relationship between the external ring fixator, the Kirschner wire 3 and the tibia 20;

[0039] As an implementable method, the CT image is imported into the medical image processing software Mimic, and the grayscale threshold is set to segment the tibia 20, the outer ring fixator, and the Kirschner wire 3 to perform a general outline segmentation, and the internal cavity of the tibia 20 is manually adjusted, and the mask segmentation method is used to obtain a complete tibia mask. The positions of the CT image, the Kirschner wire 3, the outer ring fixator and the tibia 20 are manually adjusted, and the masks of the tibia 20, the Kirschner wire 3 and the outer ring fixator are obtained by Boolean operation. Three-dimensional surface reconstruction is performed, and then meshing and surface processing are performed, and the three-dimensional image containing the tibia 20, the Kirschner wire 3, the outer ring fixator and the three-dimensional image containing the tibia alone are stored in stl format.

[0040] In one of the examples, a 3D image in stl format containing a tibia was imported into Geomagic Studio for 3D filling and the result was saved in step format.

[0041] In another example, an stl file containing a tibia, a Kirschner wire, and an external fixation ring is imported into SolidWorks, and the relative positions of the external ring fixator, the Kirschner wire 3, and the tibia 20 are obtained through the "Evaluation-Measurement" function in SolidWorks, and the model is replaced. The external ring fixator and the Kirschner wire 3 are replaced with the product model, and the tibia 20 is replaced with a three-dimensional tibia model obtained through Geomagic Studio. A three-dimensional image is re-established, such as Figure 2 shown.

[0042] Step 3: establishing a bone section coordinate system H at the bone section, a fixed coordinate system A by the proximal fixed platform 8 of the outer ring fixator, and a dynamic coordinate system B by the distal dynamic platform 7 of the outer ring fixator according to the three-dimensional reconstructed model;

[0043] Combination Figure 3 and Figure 4 Note that the proximal end refers to the position close to the trunk, and the distal end refers to the position away from the trunk. Correspondingly, the bone section divides the tibia into two parts: the proximal end 1 of the tibia close to the trunk, and the distal end 2 of the tibia away from the trunk. Similarly, the proximal fixed platform 8 is fixed to the proximal end 1 of the tibia, and the distal dynamic platform 7 is fixed to the distal end 2 of the tibia. In SolidWorks, the contour of the distal bone section is extracted, and the extracted contour is stretched a small distance (such as 0.01mm) to generate a new three-dimensional structure. The bone density is assigned to the new structure, and the centroid of the plane can be obtained by solving the center of mass solution (for a solid object with uniform density, the center of mass and the centroid coincide).

[0044] On the bone section of the distal end, a bone section coordinate system H is established with the centroid OH as the origin, wherein the x-axis 12 of the bone section coordinate system H and the y-axis 13 of the bone section coordinate system H coincide with the bone section, and the z-axis of the bone section coordinate system H is perpendicular to the bone section and points to the side of the distal platform. On the distal moving platform 7, a moving coordinate system B is established with the centroid OB of the distal moving platform as the origin, wherein the x-axis 14 of the moving coordinate system B and the y-axis 15 of the moving coordinate system B are parallel to the plane of the distal moving platform, and the z-axis 16 of the moving coordinate system B is perpendicular to the distal moving platform and points away from the side of the proximal fixed platform 8. On the proximal fixed platform 8, a fixed coordinate system A is established with the centroid OA of the proximal fixed platform as the origin, wherein the x-axis 9 of the fixed coordinate system A and the y-axis 10 of the fixed coordinate system A are parallel to the plane of the proximal fixed platform, and the z-axis 11 of the fixed coordinate system A is perpendicular to the proximal fixed platform and points to the side of the distal bone end 2 of the tibia.

[0045] Step 4: transform the rehabilitation motion based on the bone section coordinate system H to the fixed coordinate system A based on the proximal fixed platform 8 of the outer ring fixator:

[0046] The motion transformation is a spatial transformation. First, the material properties of the patient's tibia are matched with the patient's biological information to obtain the Young's modulus of the patient's corresponding healing tissue. The linear strain △L under a certain stress stimulus can be solved by the Young's modulus to determine the spatial displacement of the bone section in the bone section coordinate system. H P, where || H P||=△L;

[0047] Secondly, the displacement based on the bone section coordinate system H H P is transformed into the moving coordinate system B, and the motion in the moving coordinate system B is obtained. B P, where B P= B T H H P;

[0048] Then, the spatial displacement based on the moving coordinate system B B P is transformed into the fixed coordinate system A, and the motion in the fixed coordinate system is obtained A P, where A P= A T B B P;

[0049] in || B P OH || is the distance between the origin of the bone section coordinate system H and the origin of the moving coordinate system B, B R H is the rotation matrix of the bone section coordinate system H relative to the moving coordinate system B; || A P OB || is the distance between the origin of the moving coordinate system B and the origin of the fixed coordinate system A, A R B is the rotation matrix of the moving coordinate system relative to the fixed coordinate system.

[0050] Step 5: Combine Figure 5 Description: The inverse kinematics solution of the movement of the bone section in the fixed coordinate system A is used to obtain the movement of the branch chain on the outer ring fixator, and the movement of the branch chain is converted into motor input information to control the motor to drive the outer ring fixator to complete the rehabilitation movement.

[0051] The inverse kinematics solution process is as follows: first, the initial position in the fixed coordinate system A is solved by the inverse kinematics of the six-axis parallel platform to obtain the initial lengths l1, l2, ... l6 of the six branches (the branches in this embodiment are the general term for the universal joint 5 and the ball screw 6). AP can be solved to get the desired posture at the next moment. The desired posture is also solved by inverse kinematics to get the lengths of the six branches at the next moment l1', l2', ... l6'. The lengths of the branches at the initial moment l1, l2, ... l6 are subtracted from the lengths of the branches at the next moment l1', l2', ... l6' to get the changes in the lengths of the branches △l1, △l2, ... △l6, then △θ i =2π(△l i / h), where △θ i is the rotation angle of the motor, △l i is the change in the length of the branch chain, h is the lead of the ball screw, and the motor's rotation angle information △θ i This is fed into the motor controller as input and the desired motion is achieved.

[0052] The present invention has been disclosed as above with preferred implementation cases, but it is not used to limit the present invention. Any technician familiar with the profession can make slight changes or modifications to equivalent implementation cases with equivalent changes by using the above-disclosed structures and technical contents without departing from the scope of the technical solution of the present invention, which still fall within the scope of the technical solution of the present invention.

Claims

1. An external ring fixator for tibial fracture healing and functional rehabilitation, characterized in that: It comprises a universal joint, a ball screw, a distal moving platform and a proximal fixed platform; a ball screw is arranged between the distal moving platform and the proximal fixed platform, and the ball screw is respectively connected to the distal moving platform and the proximal fixed platform through the universal joint; The outer ring fixer implements motion planning through the following steps: Step 1: Perform a CT scan on the lower leg of a patient who has undergone fracture fixation surgery and installed a six-axis parallel external ring fixator, and obtain a CT image that includes the tibia, the Kirschner wire, and the external ring fixator fixed to the tibia through the Kirschner wire; Step 2: Perform three-dimensional reconstruction of the tibia with the external ring fixator installed according to the CT image and the patient's physiological information, obtain a three-dimensional geometric model of the tibia and determine the relative position relationship between the external ring fixator, the Kirschner wire and the tibia; Step 3: establishing a bone section coordinate system at the bone section, a fixed coordinate system for the proximal fixed platform of the outer ring fixator, and a dynamic coordinate system for the distal dynamic platform of the outer ring fixator according to the three-dimensional reconstructed model; Step 4: Transform the rehabilitation motion based on the bone section coordinate system to the fixed coordinate system of the proximal fixed platform based on the outer ring fixator: Step 5: Perform inverse kinematics on the movement of the bone section in the fixed coordinate system to obtain the movement of the branch chain on the outer ring fixator, convert the movement of the branch chain into motor input information, and control the motor to drive the outer ring fixator to complete the rehabilitation movement.

2. The outer ring fixator for tibial fracture healing and functional rehabilitation according to claim 1, characterized in that: In step three, the broken bone section fixed with the distal moving platform of the outer ring fixator is fitted into a plane through three-dimensional software and the centroid is determined. A bone section coordinate system is established with the centroid as the origin, a fixed coordinate system is established with the centroid of the proximal fixed platform of the outer ring fixator, and a dynamic coordinate system is established with the centroid of the distal moving platform of the outer ring fixator.

3. The outer ring fixator for tibial fracture healing and functional rehabilitation according to claim 1, characterized in that: Step 2: Import the CT image into medical image processing software for three-dimensional reconstruction.

4. An external ring fixator for tibial fracture healing and functional rehabilitation according to claim 1, 2 or 3, characterized in that: The motion transformation in step 4 includes: First, the patient's tibia material properties are matched with the patient's biological information to obtain the Young's modulus of the patient's corresponding healing tissue. The linear strain ΔL under a certain stress stimulus can be solved through the Young's modulus to determine the spatial displacement of the bone section in the bone section coordinate system. H P, where || H P||=ΔL; Secondly, the displacement based on the bone section coordinate system H H P is transformed into the moving coordinate system B, and the motion in the moving coordinate system B is obtained. B P, where B P= B T H H P; Then, the spatial displacement based on the moving coordinate system B B P is transformed into the fixed coordinate system A, and the motion in the fixed coordinate system A is obtained A P, where A P= A T B B P; in, || B P OH || is the distance between the origin of the bone section coordinate system H and the origin of the moving coordinate system B, B R H is the rotation matrix of the bone section coordinate system H relative to the moving coordinate system B; || A P OB || is the distance between the origin of the moving coordinate system B and the origin of the fixed coordinate system A, A R B is the rotation matrix of the moving coordinate system relative to the fixed coordinate system A.

5. The outer ring fixator for tibial fracture healing and functional rehabilitation according to claim 4, characterized in that: In step 5, the motion in the fixed coordinate system A is A The inverse kinematics of the six-axis parallel external fixator is solved by P to obtain the length change of the six branches of the six-axis parallel external fixator. The length change information of the branches is converted into motor angle or speed information, which is input into the motor as a motion input signal to realize the rehabilitation movement of the distal end of the tibia driven by the external ring fixator in space.

6. The outer ring fixator for tibial fracture healing and functional rehabilitation according to claim 5, characterized in that: The specific process of step five is: First, the initial position of the fixed coordinate system A is solved by the inverse kinematics of the six-axis parallel platform to obtain the initial lengths of the six branches l1, l2, ... l6. According to the motion of the fixed coordinate system A solved in step 4, A P can be solved to get the desired posture at the next moment. The desired posture is also solved by inverse kinematics to get the lengths of the six branches at the next moment l1', l2', ... l6'. The lengths of the branches at the initial moment l1, l2, ... l6 are subtracted from the lengths of the branches at the next moment l1', l2', ... l6' to get the changes in the lengths of the branches Δl1, Δl2, ... Δl6. Then Δθ i =2π(Δl i / h), where Δθ i is the rotation angle of the motor, Δl i is the change in the length of the branch chain, h is the lead of the ball screw, and the motor's rotation angle information Δθ i This is fed into the motor controller as input and the desired motion is achieved.

7. The outer ring fixator for tibial fracture healing and functional rehabilitation according to claim 3, characterized in that: The medical image processing software is Mimic software, which sets the grayscale threshold to segment the general contours of the tibia, external ring fixator, and Kirschner wire, reconstruct the three-dimensional surface, and then perform meshing and surface processing to store the three-dimensional image containing the tibia, Kirschner wire, external fixator ring, and the three-dimensional image of the tibia in stl format.

8. The outer ring fixator for tibial fracture healing and functional rehabilitation according to claim 7, characterized in that: The three-dimensional image in stl format containing the tibia was imported into Geomagic Studio for three-dimensional filling, and the result was saved in step format. The stl format file containing the tibia, Kirschner wire, and external ring fixator was imported into SolidWorks. The relative positions of the external ring fixator, Kirschner wire, and tibia were obtained through the "Evaluation-Measurement" function in SolidWorks. The model was replaced, and the external ring fixator and Kirschner wire were replaced with the product modeling model, and the tibia was replaced with the three-dimensional tibia model obtained through Geomagic Studio.

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