Method for determining optimal anteversion angle before femoral head osteotomy

Abstract

A method for determining the optimal anteversion angle before femoral head osteotomy, which comprises the following steps: first, establishing a femur geometric model by modeling means; then, establishing a femur guide plate model according to the surface characteristics of the femur geometric model and the determined slot reference surface of the femur guide plate model; finally, printing the femur geometric model and the femur guide plate model by 3D printing, sticking them together, drawing a mark on the femur geometric model along the slot position of the femur guide plate model by a graver, connecting the two points obtained by drawing the mark to obtain the optimal anteversion angle of the femoral prosthesis; the optimal anteversion angle of the femoral head osteotomy is determined by the slotting and marking method, the femoral head osteotomy amount can be accurately controlled, preoperative guidance is provided for the patient, compared with the manual placement of the prosthesis by the doctor and the installation of the prosthesis by using a simple guide plate, the error of the implantation angle is greatly reduced, and the risk of postoperative dislocation and the wear rate of the patient are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of total hip arthroplasty preoperative planning, in particular to a femoral head osteotomy preoperative optimal anteversion angle determination method. BACKGROUND

[0002] Total hip arthroplasty is an important means for treating end-stage osteoarthritis of the hip joint, functional dysplasia and avascular necrosis of the femoral head, etc., and is usually used in clinic to restore the joint movement function of patients. However, one of the key factors affecting the treatment effect of the surgery is whether the prosthesis can be implanted accurately according to the optimal implantation angle calculated preoperatively, so that the patient can restore normal movement ability and biomechanical properties after surgery, such as bilateral leg length, hip joint range of motion, prosthesis and bone contact characteristics, etc. These important factors are determined by surgical techniques and doctor's operation methods, which will directly affect the recovery effect of the surgery. If the difference between prosthesis implantation and preoperative planning is too large, it may cause dislocation in the short term after surgery, and the patient has to undergo treatment again.

[0003] Therefore, based on the CT data of each patient, the femoral head osteotomy amount and the optimal anteversion angle of the prosthesis implantation are planned preoperatively, and a personalized femoral surgical guide plate is established, which plays an important role in osteotomy and prosthesis implantation according to the specific conditions of the patient during surgery. However, at present, doctors generally place the prosthesis by hand, and measure the anteversion angle by visual observation, which causes large postoperative errors and poor rehabilitation effect of the patient, postoperative dislocation, bilateral lower limb inequality, and low prosthesis matching degree leading to complications such as impact and sinking. SUMMARY

[0004] In order to overcome the defects of the prior art, the purpose of the present application is to provide a femoral head osteotomy preoperative optimal anteversion angle determination method, which uses modeling means to groove on the femoral guide plate model and draw marks on the femoral geometric model, and connects the two points obtained by drawing marks to obtain the optimal implantation anteversion angle of the femoral prosthesis. The present application can accurately control the femoral head osteotomy amount and provide personalized preoperative guidance for patients.

[0005] In order to achieve the above purpose, the present application provides the following technical scheme:

[0006] A femoral head osteotomy preoperative optimal anteversion angle determination method, comprising the following steps:

[0007] Step 1: based on the CT image of the patient, the three-dimensional reconstruction of the patient's affected hip joint is carried out, the patient's femoral geometric model is obtained, and the joint is adjusted to the neutral position in the software;

[0008] Step 2: adjust the femoral geometric model to the horizontal position in the software, establish the femoral ankle reference surface, and tilt the reference surface according to the optimal implantation angle of the prosthesis calculated by the software to obtain the grooving reference surface of the femoral guide plate model, i.e. the implantation direction of the prosthesis;

[0009] Step 3: Establish the osteotomy surface, a reference surface is established on the femoral geometric model 5-10mm above the lesser trochanter and perpendicular to the femoral neck, which is the osteotomy surface that the surgeon will fit the saw to in the future, the osteotomy position is determined by the actual leg length difference of the patient, to ensure that the leg length is the same after osteotomy;

[0010] Step 4: According to the surface characteristics of the femoral geometric model in steps 1-3 and the slot reference surface of the femoral guide plate model determined in step 2, the femoral guide plate model is established, to ensure that the inner surface of the femoral guide plate model completely fits the irregular shape of the femoral head of the femoral geometric model, and bolt holes are opened on the femoral guide plate model according to the diameter of the medical screw;

[0011] Step 5: The femoral geometric model and the femoral guide plate model are both 3D printed, and the selected material is a biocompatible guide plate resin material;

[0012] Step 6: The printed femoral geometric model and femoral guide plate model are fitted, and a scribe is used to draw marks on the femoral geometric model along the slot position of the femoral guide plate model, and the two points obtained by drawing marks are connected to obtain the best anteversion angle of the femoral prosthesis before implantation.

[0013] In the step 1, the CT image of the patient is processed by using MIMICS software to perform threshold division, cavity filling, region growing, multi-layer editing and segmentation operation on the CT data of the patient, and the surface geometry model of the bone structure is obtained by three-dimensional calculation and related smoothing processing operation, and saved as.stl format.

[0014] In the step 1 of three-dimensional reconstruction, Geomagic software is used to repair the triangular facets and reconstruct the surface, the triangular facets are fitted into NRBUS surface based on the surface geometry characteristics, and the entity model is constructed, saved as.STEP format; and the best fitting command is used to fit the acetabular and femoral head joint surfaces into a sphere respectively, and the midpoint of the connecting line of the two ball centers is taken as the joint center.

[0015] In the step 1, the neutral position of the joint is obtained by adjusting the hip bone and the femur to the neutral position, and the bone model is translated to make the joint center coincide with the origin of the fixed coordinate system, wherein in the neutral position of the hip bone, the projection of the front plane of the pelvis on the sagittal plane is vertical, and in the neutral position of the femur, the axis is vertical and strictly points to the up and down direction of the human body.

[0016] In the step 4, the femoral guide plate model is lengthened on the osteotomy surface; at the same time, the screw hole position is set on the inclined plane of the femoral guide plate model, and the diameter of the screw hole matches the model of the medical screw.

[0017] Compared with the prior art, the innovation of the present application lies in:

[0018] (1) The application utilizes modeling means to groove on the femoral guide plate model, and draw marks on the femoral geometric model, and connect the two points obtained by drawing marks to determine the optimal anteversion angle of the femoral head osteotomy, and the osteotomy in this direction can ensure the consistency with the anteversion angle planned before operation, and the step 6 operation on the femoral geometric model is equivalent to simulate the future operation of the doctor on the human body in the operation, thereby reducing the risk of the patient during and after operation.

[0019] (2) Screw holes are drilled on the inclined plane of the femoral guide plate model, the fixed position of the screw is optimized, the direction is parallel to the line of sight of the doctor during operation, the screw can be easily screwed and positioned stably on the femoral head, and the screw hole is matched with the diameter of the medical screw, so that the fixation of the femoral guide plate is reliable, and relative movement does not occur between the guide plate and the femur during the sawing osteotomy.

[0020] (3) The femoral guide plate model established in step 4 is lengthened on the osteotomy surface, so that the saw can be stably fitted during the operation in the future, and the vibration caused by the insufficient contact area between the saw and the osteotomy surface of the femoral guide plate is avoided, so that the inclination of the osteotomy surface is avoided.

[0021] (4) The material for 3D printing is optimized, and a better guide plate resin material can be selected, the performance of which is strengthened compared with the ordinary resin used before, and no deformation occurs after high-temperature and high-pressure disinfection, and perfect fitting with the actual femoral head is achieved, so that the positioning and guiding functions are realized.

[0022] In summary, the application grooves on the femoral guide plate, draws marks on the femoral geometric model, connects the two points obtained by drawing marks to determine the optimal anteversion angle of the femoral head osteotomy, can accurately control the amount of femoral head osteotomy, provides preoperative guidance for patients, and greatly reduces the error of implantation angle compared with the manual placement of prosthesis by the doctor and the installation of prosthesis using a simple guide plate, thereby reducing the risk of postoperative dislocation and wear rate of the patient. BRIEF DESCRIPTION OF DRAWINGS

[0023] Fig. 1(a) is a three-dimensional hip joint model of a patient reconstructed based on CT data of the patient; Fig. 1(b) is a model in which the patient's pelvis and bilateral femurs are respectively adjusted in the sagittal plane, coronal plane and transverse plane, that is, the neutral position in the medical sense.

[0024] Fig. 2(a) is a schematic view of the femoral ankle reference surface; Fig. 2(b) is a schematic view of the anteversion reference surface; and Fig. 2(c) is a schematic view of upward translation to the guide plate side.

[0025] Figure 3 Fig. 3 is a schematic view of the osteotomy surface determined according to the positions of the femoral head and femoral neck.

[0026] Figure 4 Fig. 4 is a femoral guide plate model established according to the bone surfaces of different patients.

[0027] Figure 5 This is a femoral guide plate model manufactured using photopolymerization 3D printing technology. Detailed Implementation

[0028] The present invention will now be further described with reference to the accompanying drawings.

[0029] This invention provides a method for determining the optimal anteversion angle before femoral head osteotomy, comprising the following steps:

[0030] Step 1: Based on the patient's CT images, perform three-dimensional reconstruction of the affected hip joint. Use Geomagic software to repair the triangular facets and reconstruct the surface. Outline the bone contours of each CT slice to obtain the geometric model of the patient's hip bone and proximal femur, as shown in Figure 1(a). After adjusting the hip joint to the neutral position, it is shown in Figure 1(b). To obtain the neutral position of the joint, adjust the hip bone and femur to the neutral position of motion by adjusting the joint center and translating the bone model so that the joint center coincides with the origin of the fixed coordinate system. When the hip bone is in the neutral position, the projection of the anterior plane of the pelvis on the sagittal plane is vertical. When the femur is in the neutral position, its axis is vertical and strictly points in the direction of the upper and lower sides of the human body.

[0031] Step 2: Import the femoral model based on CT data into SolidWorks software. After unpacking the features, draw the femoral guide plate. First, establish the femoral ankle reference plane as shown in Figure 2(a). Tilt the reference plane according to the optimal implantation anteversion angle planned by the software before surgery to obtain the anteversion reference plane as shown in Figure 2(b). Then, translate the anteversion reference plane to the femoral guide plate to obtain the femoral guide plate slot reference plane as shown in Figure 2(c).

[0032] Step 3: Determine the osteotomy surface, such as... Figure 3 As shown, the osteotomy surface and height are determined preoperatively based on the position of the femoral head and neck to ensure that both legs are the same length after the prosthesis is inserted. Its position is 5-10mm above the lesser trochanter and perpendicular to the femoral neck; the specific distance from the lesser trochanter depends on the patient's actual leg length and the surgeon's preoperative planning.

[0033] Step 4: Based on the surface features of the femoral geometric model, namely the surfaces of the femoral head and neck, a femoral guide plate model is created in SolidWorks software, such as... Figure 4The femoral guide plate model is modeled according to different patient bone surfaces, and different femoral guide plates can be modeled according to different surgical approaches of different doctors, that is, the anterior femoral guide plate and the posterior femoral guide plate. According to the actual use of the screw nominal diameter, the screw hole is opened on the femoral guide plate, the screw hole adopts a 3.5mm diameter to match the medical screw model, and the fixation of the femoral guide plate is reliable, so that the relative movement between the guide plate and the femur does not occur when the saw is cut, and the positioning of the femoral guide plate is reliable.

[0034] Step 5: The femoral guide plate model and the femoral geometric model are printed out by using 3D printing technology, the selected material is a guide plate resin material, the printing layer thickness is set to 0.1mm, and the printed physical model is as shown in Figure 5 The physical model material is a guide plate transparent resin material; the selected guide plate transparent resin material can be sterilized by ethylene oxide and high temperature and high pressure, and after sterilization, it will not deform and can ensure the close cooperation with the femoral head, and the actual anteversion angle is consistent with the preoperative planning anteversion angle to the greatest extent.

[0035] Step 6: The printed femoral geometric model and femoral guide plate model are attached, the scribe is used to draw marks on the femoral geometric model along the slot position of the femoral guide plate model, and the two points obtained by drawing marks are connected to obtain the best implantation anteversion angle of the femoral prosthesis.

[0036] In the future, when applied in the operation, the obtained femoral guide plate is sterilized by high temperature and high pressure or ethylene oxide, and is used in cooperation with the acetabular guide plate in the operation. After the femoral head is exposed in the operation, the femoral guide plate is installed on the femoral neck, medical screws are punched after the positioning is determined to be firm, the scribe is used to draw lines on the femoral neck along the slot position of the femoral guide plate, and then the femoral head is cut along the osteotomy surface of the femoral guide plate. The line drawn by the scribe on the osteotomy surface is connected to form a horizontal line, which is the best implantation direction of the femoral prosthesis. The medullary cavity is opened on the femur along the direction, and the medullary cavity for placing the prosthesis is tapered on the osteotomy surface. Then the femoral prosthesis is placed into the medullary cavity, and the prosthesis is implanted along the direction of the line, that is, the best anteversion direction, to complete the total hip replacement part on the femoral side. The prosthesis implanted at this position can be consistent with the preoperative planning angle to the greatest extent, and dislocation is effectively prevented.

[0037] The above embodiments are only the preferred specific embodiments of the present application, and the protection scope of the present application is not limited thereto. Any simple change or equivalent replacement of the technical solutions within the technical range disclosed by the present application can be obtained by those skilled in the art, and all belong to the protection scope of the present application.

Claims

1. A method of determining the optimal anteversion angle for femoral head osteotomy, characterized in that, It comprises the following steps: Step 1: three-dimensional reconstruction of the patient's affected hip joint based on the patient's CT image, obtaining the patient's femur geometric model and adjusting it to the joint neutral position in the software; Step 2: adjust the femur geometric model to the horizontal position in the software, establish the femoral condyle reference plane, tilt the reference plane according to the best implantation angle of the prosthesis calculated by the software, and obtain the slotting reference plane of the femoral guide plate model, that is, the implantation direction of the prosthesis; Step 3: establish the reference plane on the position 5-10mm above the femoral lesser trochanter and perpendicular to the femoral neck of the femur geometric model, which is the cutting surface for the doctor to place the saw during the operation, and the cutting position is determined by the actual leg length difference of the patient to ensure that the leg length is the same after cutting; Step 4: establish the femoral guide plate model according to the surface characteristics of the femur geometric model and the slotting reference plane of the femoral guide plate model, ensure that the inner surface of the femoral guide plate model completely matches the irregular shape of the femoral head of the femur geometric model, and open bolt holes on the femoral guide plate model according to the diameter of the medical screw; Step 5: 3D print the femur geometric model and the femoral guide plate model, and the selected material is a biocompatible guide plate resin material; Step 6: fit the printed femur geometric model and femoral guide plate model, use a graver to draw marks on the femur geometric model along the slotting position of the femoral guide plate model, and connect the two points obtained by drawing marks to get the best implantation anteversion angle of the femoral prosthesis.

2. The method of determining optimal anteversion angle prior to femoral head osteotomy according to claim 1, wherein, In step 1, the patient's CT image is obtained by using MIMICS software to perform threshold division, cavity filling, region growing, multi-layer editing and segmentation operation on the patient's CT data, and through three-dimensional calculation and related smoothing operation, the surface geometry model of the bone structure is obtained and saved as.stl format.

3. The method of determining optimal anteversion angle prior to femoral head osteotomy according to claim 1, wherein, In step 1, when three-dimensional reconstruction is performed, Geomagic software is used to repair triangular facets and reconstruct surfaces, triangular facets are fitted into NRBUS surface based on surface geometric characteristics, and a solid model is constructed, saved as.STEP format; and the best fitting command is used to fit the acetabulum and femoral head joint surface into a sphere respectively, and the midpoint of the connecting line of the two sphere centers is taken as the joint center.

4. The method of determining optimal anteversion angle prior to femoral head osteotomy according to claim 1, wherein, In step 1, the joint neutral position is obtained by adjusting the hip bone and femur to the neutral position and translating the bone model to make the joint center coincide with the origin of the fixed coordinate system, wherein when the hip bone is in the neutral position, the projection of the anterior plane of the pelvis on the sagittal plane is vertical, and when the femur is in the neutral position, its axis is vertical and strictly points to the up and down direction of the human body.

5. The method of determining optimal anteversion angle prior to femoral head osteotomy according to claim 1, wherein, In step 4, the femoral guide plate model is lengthened on the cutting surface; at the same time, the screw hole position is set on the inclined plane of the femoral guide plate model, and the diameter of the screw hole matches the model of the medical screw.

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