阅读说明：本技术 面向骨折手术机器人的踝关节骨折术后早期量化康复方法 (Fracture surgery robot-oriented early-stage quantitative rehabilitation method for ankle fracture surgery ) 是由 孙涛 倪沫楠 晋嘉浩 宋轶民 于 2021-08-03 设计创作，主要内容包括：本发明公开了一种面向骨折手术机器人的踝关节骨折术后早期量化康复方法,基于有限元分析,采用骨间位移作为安全运动的限制条件,建立了踝关节骨折术后早期被动康复训练的定量方法。通过有限元分析,还可以揭示踝关节运动过程中,关节内部生物力学行为变化规律。弥补了传统生物力学研究中,针对踝关节骨折康复训练方法的缺失。同时,本发明对于其他可被重建的踝关节骨折类型具有普适性。该方法不需要大量的循环试验,可以大大降低时间成本和经济成本,且能够直接应用在机器人辅助康复工程中,降低术后并发症概率,提高康复质量。(The invention discloses an ankle fracture postoperative early-stage quantitative rehabilitation method oriented to a fracture surgery robot, which is based on finite element analysis and adopts inter-osseous displacement as a limiting condition of safe movement, and establishes a quantitative method of ankle fracture postoperative early-stage passive rehabilitation training. Through finite element analysis, the change rule of the biomechanical behavior inside the joint in the motion process of the ankle joint can be revealed. Makes up for the deficiency of the rehabilitation training method aiming at the fracture of the ankle joint in the traditional biomechanical research. Meanwhile, the invention has universality for other types of ankle joint fractures which can be reconstructed. The method does not need a large number of cyclic tests, can greatly reduce time cost and economic cost, can be directly applied to robot-assisted rehabilitation engineering, reduces postoperative complication probability and improves rehabilitation quality.)

1. An early-stage quantitative rehabilitation method after ankle fracture surgery for a fracture surgery robot is characterized by comprising the following steps:

step 1, performing three-dimensional reconstruction on a CT data set of a healthy volunteer;

acquiring a CT image of an ankle joint of a healthy volunteer, importing the CT image into medical image processing software to perform threshold segmentation operation, and reconstructing the CT image into a 3D geometric surface model comprising a tibia, a fibula, a talus, a calcaneus, a tibia cartilage, a talus cartilage and two pieces of talus cartilage; importing the three-dimensional solid into reverse reconstruction software to perform accurate curved surface operation to form a three-dimensional solid;

step 2, performing virtual fracture and operation on the geometric model of the healthy ankle joint;

performing virtual truncation in three-dimensional drawing software to simulate various ankle joint fracture types, and performing virtual internal fixation by using an internal fixation instrument model according to actual conditions;

step 3, establishing a complete finite element model after the ankle fracture operation;

inserting a spring unit into finite element simulation software to simulate an ankle joint ligament, applying fixing constraint to a tibiofibular joint near end, establishing an ankle joint motion coordinate system at a far end, applying motion load of 20 degrees of dorsiflexion to 32 degrees of plantarflexion to form a finite element model after the ankle joint fracture surgery, and performing simulation calculation;

step 4, establishing the relationship between the displacement and the movement angle between bones, setting safety conditions and obtaining a rehabilitation training range;

defining the average displacement difference of the fracture surface of the bone block and the fracture surface of the body at each fracture part as the bone displacement; outputting the relationship between the displacement and the movement angle between bones; according to the previous research results, the early passive rehabilitation range after ankle fracture surgery can be quantified by using 150 μm as a safety limit condition according to the relationship obtained in step 4.

2. The method for early quantitative rehabilitation after ankle fracture surgery oriented to fracture surgery robot as claimed in claim 1, characterized in that the calcaneus bone in step 1 comprises cortical bone and cancellous bone.

The technical field is as follows:

the invention relates to the field of crossing of robots and rehabilitation medical engineering, in particular to an ankle joint fracture postoperative early-stage quantitative rehabilitation method oriented to a fracture surgery robot.

Background art:

ankle fracture is a multiple disease, and dislocation fracture must be treated by surgery. Accurate anatomical reduction and strong internal fixation can restore the physiological structure of the ankle joint to the maximum extent. However, postoperative rest may result in loss of ankle function. Early rehabilitation training has been shown to reduce or even avoid the series of complications of deep vein thrombosis, muscle contracture, joint adhesion and traumatic arthritis. Generally, rehabilitation training after ankle fracture surgery is divided into two modes of passive rehabilitation and active rehabilitation. Passive rehabilitation is usually achieved by a doctor or an instrument assisting the patient in dorsiflexion/plantarflexion rehabilitation training, and is the most common rehabilitation mode used in the early postoperative period. At present, the establishment of a passive rehabilitation training scheme depends on the experience of doctors, the improper or excessive motion range can prevent healing and even secondary injury, and no clear early quantitative rehabilitation method after ankle fracture surgery exists.

Determining early biomechanical behavior of ankle fractures is key to quantifying the range of motion for rehabilitation. Finite element analysis is one of the most effective techniques to solve biomechanical problems. The existing research provides a method for establishing a complete ankle finite element model, and reveals the mechanical behavior of different types of injuries of the ankle under the action of static load. However, the influence rule of the ankle joint flexion and extension movement on the internal mechanical environment of the joint (especially the fracture part) is not disclosed. This is the core and difficult problem of quantifying the range of early postoperative rehabilitation training.

The invention content is as follows:

the invention aims to provide a universal early-stage quantitative rehabilitation method for the fracture of the ankle joint after the operation based on a finite element analysis method.

The technical scheme adopted by the invention for solving the technical problems is as follows:

the method for early quantitative rehabilitation after the ankle fracture surgery for the fracture surgery robot comprises the following steps:

step 1, performing three-dimensional reconstruction on a CT data set of a healthy volunteer.

The method comprises the steps of collecting CT images of ankle joints of healthy volunteers, importing the images into medical image processing software to perform operations such as threshold segmentation and the like, and reconstructing the images into a 3D geometric surface model comprising tibia, fibula, talus, calcaneus (including cortical bone and cancellous bone), tibia cartilage, talus cartilage and two pieces of calcaneus cartilage. And importing the three-dimensional solid into reverse reconstruction software to perform accurate curved surface operation to form a three-dimensional solid.

And 2, performing virtual fracture and operation on the geometric model of the healthy ankle joint.

Performing virtual truncation in three-dimensional drawing software to simulate various ankle joint fracture types, and performing virtual internal fixation by using an internal fixation instrument model according to actual conditions.

And 3, establishing a complete finite element model after the ankle fracture operation.

Inserting a spring unit into finite element simulation software to simulate an ankle joint ligament, applying fixing constraint to the tibiofibular joint near end, establishing an ankle joint motion coordinate system at the far end, applying motion load of dorsiflexion of 20 degrees to plantarflexion of 32 degrees, forming a finite element model after the ankle joint fracture surgery, and performing simulation calculation.

And 4, establishing the relationship between the bone displacement and the motion angle, setting safety conditions and obtaining the rehabilitation training range.

The mean difference in displacement between the fracture surface of the bone block and the fracture surface of the body at each fracture site was defined as the interosseous displacement. And outputting the relation between the displacement between bones and the movement angle. According to the previous research results, the early passive rehabilitation range after ankle fracture surgery can be quantified by using 150 μm as a safety limit condition according to the relationship obtained in step 4.

The invention has the beneficial effects that:

the invention provides a complete method for establishing a finite element model after ankle fracture surgery, and the biomechanical behavior in the joint under the stimulation of rehabilitation motion is analyzed by applying flexion and extension motion load. Provides a universal early-stage quantitative rehabilitation method for fracture surgery robots. In theory, the method is applicable to any type of ankle fracture that can be reconstructed in three dimensions. The problem of blindness and experience of early rehabilitation training after ankle fracture surgery is solved.

Description of the drawings:

FIG. 1 is a flow chart of a method for quantifying the range of early rehabilitation training after an ankle fracture operation according to the present invention;

FIG. 2 is a schematic view of a fracture simulation of one embodiment of the present invention;

FIG. 2a is a schematic view of a lateral malleolus fracture pattern;

FIG. 2b is a schematic view of an internal ankle fracture pattern;

FIG. 2c is a schematic view of a posterior ankle fracture line definition;

FIG. 2d is a schematic representation of a posterior ankle fracture pattern;

FIG. 3 is a schematic diagram of a post-operative finite element model of one embodiment of the present invention;

FIG. 3a is a front view;

FIG. 3b is a rear view;

wherein: 1-periosteum; 2-tibiofibular anterior ligament; 3-tibiofibular posterior ligament; 4-tibialis anterior ligament; 5-tibial posterior ligament; 6-fibular anterior ligament; 7-posterior fibular ligament; 8-the calcaneofibular ligament; 9-the tibioheel ligament; 10-calcaneal ligament; 11-lateral calcaneal ligament; 12-calcaneal ligament;

FIG. 4 is a graph of inter-bone displacement versus angle of motion for one of the examples of the present invention;

the specific implementation mode is as follows:

the technical scheme of the invention will be clearly and completely described by taking the 44A3.3 type fracture as one embodiment of the invention.

Referring to the attached drawing 1, the invention provides an ankle fracture postoperative early-stage quantitative rehabilitation method for a fracture surgery robot, which comprises the following steps:

step 1, acquiring CT images of healthy volunteers, importing the CT images into medical image processing software, and reconstructing a complete ankle joint three-dimensional solid model by combining reverse engineering software.

In one embodiment of the invention, the CT image is imported into mic for threshold segmentation to segment the position and approximate contour of tibia, talus, fibula and calcaneus. The internal cavities of 4 bones were filled in combination with manual operations to form 4 complete masks. At this time, the cortical and cancellous bones are not segmented. And segmenting a corresponding cancellous bone mask from 4 complete bone masks by combining morphological corrosion operation and manual modification. And (4) segmenting a corresponding cortical bone mask by adopting Boolean operation. According to the CT image and the anatomical position of the ankle joint cartilage, the tibia cartilage, the talus cartilage and 2 pieces of calcaneal cartilage are drawn manually from corresponding bone masks, and the cartilage is divided from the bone masks by adopting Boolean operation and combined with manual modification to form masks of 4 pieces of cartilage. After they are reconstructed into a three-dimensional surface, they are smoothed and mesh-simplified and saved in STL format.

In one embodiment of the invention, the obtained 12 models are introduced into a Geomagic Studio to perform accurate surface operation, so as to form a three-dimensional solid model, and the three-dimensional solid model is stored in a STEP format.

In one embodiment of the invention, cortical bone and cartilage are opened in SolidWorks for boolean operations, ensuring smooth contact between models without interference. Stored in STEP format.

And 2, performing virtual truncation in three-dimensional drawing software to simulate ankle joint fracture, and performing virtual internal fixation by using an internal fixation instrument model according to actual conditions.

In one embodiment of the invention, the resulting tibial and fibular models were introduced into SolidWorks. The simulation of the fracture was performed according to AO typing. Referring to fig. 2, the fibula fracture was simulated by cutting in a plane 22mm from the anterior border of the lateral malleolus and parallel to the transverse plane; the internal ankle fracture is cut off at the ankle tenon part by a plane with an included angle of 30 degrees with the cross section; two bulges AB on the outer side of the far end of the tibia are connected to be used as reference lines, a point C at the intersection point O of the posterior ankle and the medial ankle and a point C at the line AB 1/4 are connected to be used as fracture lines, and the simulation of the fracture of the posterior ankle is cut off by a plane with 60 degrees formed by an OC line and the cross section.

In one embodiment of the present invention, the internal fixation instrument comprises a steel plate and a screw, wherein the steel plate is a model reconstructed by CT images and the screw is replaced by a cylinder model. And assembling the fracture model and the internal fixation instrument model to form a three-dimensional solid model after the fracture operation, and storing the three-dimensional solid model in a STEP format.

And 3, establishing a complete finite element model after the ankle fracture operation in finite element simulation software.

In one embodiment of the present invention, referring to FIG. 3, the entire model is imported into an Ansys Workbench for further processing. The simulation of ligaments was simulated using linear springs, considering 12 types: the posterior tibial ligament (PTiFL), the anterior tibial ligament (ATiTL), the posterior tibial ligament (PTiTL), the anterior tibial ligament (ATaFL), the posterior tibial ligament (PTaFL), the posterior calcaneofibular ligament (CaFL), the tibiofemoral ligament (TiCL), the medial calcaneal ligament (mtalcl), the lateral calcaneal ligament (LTaCL), and the posterior calcaneal ligament (PTaCL). The stiffness and number of ligaments are listed in table 1.

TABLE 1 ligament stiffness

All bones and implants assumed isotropic linear elastic characteristics, and the material properties used are listed in table 2. Due to the complexity of the bone and cartilage surfaces, a method of free meshing was chosen. The mesh model has 58627 nodes, 28730 cells. In order to make the whole model more approximate to the real biomechanical condition, the interaction type is carefully selected, and the binding constraint between the screw and the bone simulates the pretightening force of the screw. Binding constraints are applied between the cartilage and bone to fix their relative positions. The friction type between the cartilage and the broken bone piece and the body is defined, and the friction coefficients are 0.1 and 0.4 respectively.

TABLE 2 Material Properties

According to the definition of an ankle joint coordinate system by the international biomechanics society, a middle point of a connecting line between an inner ankle tip and an outer ankle tip is used as an origin, the connecting line is used as a rotating shaft, the ankle joint coordinate system is established, 20-degree dorsiflexion and 32-degree plantarflexion rotation loads are respectively applied in a normal motion range of an ankle joint, after multiple tests, 3-mm y-axis negative displacement and 2-mm z-axis negative displacement are applied during dorsiflexion during rotation, 3-mm y-axis positive displacement and 1-mm z-axis negative displacement are applied during plantarflexion, the ankle joint coordinate system is used for ensuring the joint of an ankle joint contact surface, and the proximal surfaces of a tibia and a fibula are used for applying fixation constraint.

And 4, establishing the relationship between the bone displacement and the motion angle, setting safety conditions and obtaining the rehabilitation training range.

In one embodiment of the invention, the fracture surfaces of the lateral malleolus, the medial malleolus and the posterior malleolus bone pieces and the fracture surface of the body are respectively selected to output average displacement, and the data are stored in a csv format. And (3) carrying out data arrangement and calculation in Matlab to obtain the change of the relative displacement difference between the bone block and the body along with time, wherein the relative displacement difference is called as the bone displacement. Referring to fig. 4, a graph of inter-bony displacement versus angle of motion is obtained by mapping the change in angle of motion over time in time steps to the inter-bony displacement.

In one embodiment of the present invention, reference is made to the study by Fujie H et al and Shimamura Y et al. (for details see references: Fujie H. negative effects of mechanical stimulation on fracture healing [ J ]. Jscbrr,1988,10. and Shimamura Y, Kaneko K, Kume K, et al. initial safe range of motion of the ankle joint after three internal fixation methods to simulate an internal ankle fracture. Clinical biometics, 2006,21(6):617 and 622.) with 150 μm as the safe limit (FIG. 4), the early safe range of motion after surgery for this example was derived: dorsiflexion is 10.1 degree to plantarflexion is 12.5 degree.

In conclusion, the quantitative method for early passive rehabilitation training after ankle fracture surgery is established based on finite element analysis and by adopting the inter-osseous displacement as the limiting condition of safe movement. Through finite element analysis, the change rule of the biomechanical behavior inside the joint in the motion process of the ankle joint can be revealed. Makes up for the deficiency of the rehabilitation training method aiming at the fracture of the ankle joint in the traditional biomechanical research. Meanwhile, the invention has universality for other types of ankle joint fractures which can be reconstructed. The method does not need a large number of cyclic tests, can greatly reduce time cost and economic cost, can be directly applied to robot-assisted rehabilitation engineering, reduces postoperative complication probability and improves rehabilitation quality.

The embodiments of the present invention are not limited to the specific examples described above. It will be apparent to those skilled in the art that other variations and modifications can be made without departing from the spirit of the invention and the scope of the appended claims.