WO2020119683A1 - 膝关节假体垫片三维力传感器及其接触应力测量方法 - Google Patents

膝关节假体垫片三维力传感器及其接触应力测量方法 Download PDF

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WO2020119683A1
WO2020119683A1 PCT/CN2019/124328 CN2019124328W WO2020119683A1 WO 2020119683 A1 WO2020119683 A1 WO 2020119683A1 CN 2019124328 W CN2019124328 W CN 2019124328W WO 2020119683 A1 WO2020119683 A1 WO 2020119683A1
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curved surface
hard layer
layer
force sensor
dimensional force
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PCT/CN2019/124328
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English (en)
French (fr)
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王宇
胡颖
杨远源
赵世佳
何玉成
高鹏
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中国科学院深圳先进技术研究院
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Publication of WO2020119683A1 publication Critical patent/WO2020119683A1/zh

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general

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  • the invention belongs to the technical field of medical equipment, and particularly relates to a three-dimensional force sensor of a knee joint prosthesis pad and a contact stress measurement method thereof.
  • Soft tissue balance is an important part of total knee arthroplasty (TKA).
  • TKA total knee arthroplasty
  • the quality of its treatment directly affects the stability and function of the knee joint after surgery.
  • the so-called soft tissue balance mainly involves stable static structures such as knee ligaments and joint capsules, that is, the pursuit of "ligament balance", emphasizing on the basis of correct osteotomy, by loosening ligaments, joint capsules, etc.
  • the starting point or the stopping point allows the joint to return to the normal force line arrangement, thereby restoring the normal joint surface contact point.
  • the main method of soft tissue balance is to indirectly evaluate the balance by measuring the joint space.
  • the US patent application US2013/0079668A1 discloses a high-precision smart joint sensor in the knee joint (smart trials), which uses the principle of capacitive sensing.
  • the shape of the sensor is consistent with the shape of the standard prosthesis.
  • the force first acts on the upper surface of the housing. Due to the flexibility of the housing material, the force is transmitted to the triangular pressure plate after deformation. Below the pressure plate is the bottom plate with capacitive sensing elements. There are three sensing elements in the left and right side chambers respectively. Because the position and size of the concentrated force on the plane can be calculated from the three-point force size and position, the software interface of this prosthetic pad sensor can display the prosthetic pad sensor in real time. The point and size of the concentration of the chamber on both sides.
  • the thickness of the smart pad can be made the same as the real prosthesis by using the thickness adjustment sheet.
  • the polyethylene shell contains an integrated circuit board inside.
  • the circuit board contains components such as power supply, sensor, signal transmitter and switch.
  • the four mechanical sensors are evenly distributed on both the inner and outer sides, which can convert the displacement signal into an electronic signal.
  • the internal stress of the knee joint can be converted into a radio signal and sent to the signal receiver.
  • the receiver transmits the information to the computer terminal.
  • the medial and lateral stress value (unit: N)
  • the form is displayed on the screen.
  • the surgeon can evaluate the stress distribution and soft tissue balance in joints at different angles through the size of the medial and lateral stress displayed on the terminal screen. According to reports, the measurement accuracy error of the stress measurement system is ⁇ 4%, and the repeated measurement error is ⁇ 5%.
  • the existing knee prosthesis pad sensor can only measure the component size of the joint contact stress in one direction. Since the actual shape of the joint prosthesis pad is a curved surface, the position and size of the concentrated force in the one-dimensional direction often cannot reflect The true stress distribution.
  • the object of the present invention is to provide a three-dimensional force sensor for a knee joint prosthesis pad and a contact stress measurement method thereof, aiming to solve the problem in the prior art that a knee joint prosthesis pad sensor can only measure one direction of joint contact stress The size of the component causes it to fail to reflect the true technical problem of stress distribution.
  • a three-dimensional force sensor for a knee joint prosthesis pad including:
  • An intermediate flexible layer has an upper curved surface and a lower curved surface, and a plurality of sensing elements are provided on the upper curved surface or the lower curved surface;
  • An upper hard layer the shape of the upper hard layer is adapted to the shape of the upper curved surface and fits on the upper curved surface;
  • a lower hard layer, the shape of the lower hard layer is adapted to the shape of the lower curved surface and is attached to the lower curved surface.
  • the lower hard layer is provided with a plurality of support columns corresponding to the positions of the sensing elements
  • each of the support columns is attached to the lower curved surface;
  • each of the support columns is respectively attached to each of the sensing elements.
  • each of the sensing elements is arranged close to the periphery of the lower curved surface.
  • the shape of the upper end surface of the support column is adapted to the shape of the corresponding position of the lower curved surface.
  • the middle flexible layer is a silica gel layer
  • the upper hard layer and the lower hard layer are both polyethylene layers.
  • both the silicone layer and the polyethylene layer are made by 3D printing.
  • the sensing element is a flexible thin-film sensing element.
  • an upper concave cavity is provided on the top of the middle flexible layer, the bottom surface of the upper concave cavity is the upper curved surface, and the upper hard layer is accommodated in the upper concave cavity.
  • a concave cavity is provided at the bottom of the middle flexible layer, the cavity bottom surface of the concave cavity is the lower curved surface, and the lower hard layer is accommodated in the concave cavity.
  • the three-dimensional force sensor of the knee joint prosthesis pad of the present invention has an overall structure of a hard-soft-hard three-layer structure, and each sensing element provided on the upper or lower curved surface of the middle flexible layer It can be arranged according to the actual sensing point. Due to its own variability, the force signal output by each sensing element plus the normal direction of the position provides a three-dimensional force signal, and the contact between the tibiofemoral joint can be calculated by the algorithm The direction and position of the force force make the measured value more accurate and can calculate the three-dimensional force of the joint contact stress, reflecting a more realistic stress distribution, which provides doctors with a way to judge the force distribution between the joints and the soft tissue balance link. Quantitative guidance.
  • a contact stress measurement method for a three-dimensional force sensor of a knee joint prosthesis pad which is used to measure the three-dimensional force sensor of the knee joint prosthesis pad described above, and includes the following steps:
  • the contact stress measurement method of the three-dimensional force sensor of the knee joint prosthesis pad of the present invention can measure the three-dimensional contact force between the joints, not just the component in a certain direction, and the contact between the tibiofemoral joints can be calculated by the algorithm
  • the direction and position of the force force make the measured value more accurate and can calculate the three-dimensional force of the joint contact stress, reflecting a more realistic stress distribution, which provides doctors with a way to judge the force distribution between the joints and the soft tissue balance link. Quantitative guidance.
  • FIG. 1 is a schematic structural diagram of a three-dimensional force sensor of a knee joint prosthesis provided by an embodiment of the present invention.
  • FIG. 2 is an exploded schematic view of the structure of a three-dimensional force sensor of a knee joint prosthesis provided by an embodiment of the present invention.
  • FIG. 3 is a schematic structural diagram of a middle flexible layer of a three-dimensional force sensor of a knee prosthesis pad provided by an embodiment of the present invention.
  • FIG. 4 is a partial structural schematic diagram of a three-dimensional force sensor of a knee joint prosthesis pad provided by an embodiment of the present invention.
  • first and second are used for description purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated.
  • the features defined as “first” and “second” may explicitly or implicitly include one or more of the features.
  • the meaning of “plurality” is two or more, unless otherwise specifically limited.
  • the terms “installation”, “connected”, “connected”, “fixed” and other terms should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , Or integrated; it can be mechanical connection or electrical connection; it can be directly connected or indirectly connected through an intermediary, it can be the connection between two components or the interaction between two components.
  • installation can be a fixed connection or a detachable connection , Or integrated; it can be mechanical connection or electrical connection; it can be directly connected or indirectly connected through an intermediary, it can be the connection between two components or the interaction between two components.
  • a three-dimensional force sensor for a knee prosthesis pad provided by an embodiment of the present invention can be applied between tibial and femoral joints.
  • the shape of the sensor is similar to that of femur and tibia implanted during TKA surgery.
  • the shape of the standard prosthesis pads is consistent.
  • the knee prosthesis pad sensor is placed between the tibial and femoral joints of the patient to simulate the measurement of the stress distribution between the joints after replacement.
  • the sensor of the embodiment of the present invention has the advantage of being able to measure the three-dimensional contact force between the joints, not just the component in a certain direction, and the unique combination of soft and hard.
  • the layered structure design ensures a good and accurate transmission of force from top to bottom, supplemented by the surface concentration force algorithm, which can calculate the direction and position of the resultant force, combined with the dynamic model of the knee flexion process for soft tissue balance.
  • the link provides quantitative guidance, which provides quantitative guidance for doctors to judge the distribution of force between joints and the balance of soft tissue.
  • the three-dimensional force sensor of the knee prosthesis pad includes an intermediate flexible layer 10, an upper hard layer 20, and a lower hard layer 30.
  • the three-layer structure is fixedly connected, and the overall structure shape is completely consistent with the standard prosthesis shape.
  • the shapes of the upper hard layer 20 and the lower hard layer 30 are respectively adapted to the articular surfaces of the corresponding tibiofemoral joints.
  • the middle flexible layer 10 has an upper curved surface 101 and a lower curved surface 102, and the arrangement of the upper curved surface 101 and the lower curved surface 102 can be used to communicate with the upper hard layer 20 and the lower hard surface, respectively Layer 30 adapts the connection.
  • each sensing element 40 can be disposed on the upper curved surface 101 or the lower curved surface 102 according to actual needs; the upper hard layer 20 is pasted Combined with the upper curved surface 101, when the upper hard layer 20 is stressed, the force will be transmitted to the middle flexible layer 10, because the middle flexible layer 10 has good contact characteristics, so that each sensing element 40
  • the output force information carries direction information, that is, the normal direction of each sensing element 40; the lower hard layer 30 is attached to the lower curved surface 102, and the setting of the lower hard layer 30 ensures that the pressure is completely distributed in the induction Point (ie the position where the sensing element 40 is set).
  • the shape of the upper hard layer 20 is adapted to the shape of the upper curved surface 101
  • the shape of the lower hard layer 30 is adapted to the shape of the lower curved surface 102, so designed It can be ensured that the middle flexible layer 10 can completely fit the upper hard layer 20 and the lower hard layer 30, and the force of the upper hard layer 20 can be transmitted evenly.
  • the overall structure of the knee joint prosthesis pad three-dimensional force sensor of the embodiment of the present invention is a hard-soft-hard three-layer structure, and the upper surface 101 or the lower surface 102 provided on the middle flexible layer 10
  • Each sensing element 40 can be arranged according to the actual sensing point. Due to its own variability, the force signal output by each sensing element 40 plus the normal direction of the location provides a three-dimensional force signal, which can be calculated by the algorithm
  • the size and direction of the contact force between the femoral joints makes the measured value more accurate and can calculate the three-dimensional joint force of the joint contact stress, reflecting a more realistic stress distribution, for the doctor to determine the force distribution between the joints and
  • the soft tissue balance link provides quantitative guidance.
  • the number of the sensing elements 40 is set according to actual needs, and may be six, seven, eight, or nine, for example.
  • a plurality of support pillars 31 corresponding to the positions of the sensing elements 40 are provided on the lower hard layer 30.
  • the setting position of each sensing element 40 is a sensing point, and the setting position of the lower hard layer 30 also corresponds to each sensing point.
  • each of the support columns 31 is attached to the lower curved surface 102.
  • each of the support posts 31 is respectively attached to each of the sensing elements 40. In this way, the rigid structure of the support column 31 is supported on each sensing point, then it can effectively ensure that the pressure is completely distributed on the sensing point (that is, the position where the sensing element 40 is set), and further improve the measured and calculated resultant force Accuracy of size direction and action position.
  • the bottom of the middle flexible layer 10 is preferably provided with a stepped structure (see FIG. 3 for details).
  • the stepped structure has two surfaces with different heights ( The height difference may be equal to the height of the support pillar 31), the sensing element 40 may be disposed on a surface of a height, and the lower hard layer 30 is provided with the surface of the support pillar 31 and is attached to the surface of another height.
  • each of the sensing elements 40 is arranged close to the periphery of the lower curved surface 102. In this way, the settings corresponding to each sensing point can be prepared.
  • the sensing element 40 may be disposed at a position not close to the periphery of the lower curved surface 102. As long as the calculation of the magnitude and position of the concentrated force can be realized on the curved surface, the three-point force measurement algorithm can be extended.
  • the shape of the upper end surface of the support column 31 is adapted to the shape of the corresponding position of the lower curved surface 102. In this way, it can be ensured that the support column 31 can be completely attached to the lower curved surface 102 or the sensing element 40 provided on the lower curved surface 102, and the stability and reliability of the entire sensor structure are ensured.
  • the middle flexible layer 10 is a silicone layer, and the middle flexible layer 10 is made of silicone material.
  • the flexibility of the silicone material ensures that the sensing element 40 can have good contact with the upper hard layer 20 or the lower hard layer 30.
  • the silicone material can also be replaced by other flexible materials that meet the requirements.
  • both the upper hard layer 20 and the lower hard layer 30 are polyethylene layers.
  • the upper hard layer 20 and the lower hard layer 30 made of polyethylene material are easy to form on the one hand, and the layer structure formed is moderate in hardness, and can form a perfect combination with the middle flexible layer 10 made of silicone material.
  • both the silicone layer and the polyethylene layer are made by 3D printing. That is to say, the three-layer structure of the sensor in this embodiment can be manufactured using a 3D printing process, so that it can be produced quickly and at a low cost.
  • the shape of the layer structure is also easy to design and shape, and has strong practicality.
  • the sensing element 40 is a flexible thin-film sensing element. That is, the entire sensing element 40 is a flexible thin film structure, which is favorable for being attached to the upper curved surface 101 or the lower curved surface 102, and when it is attached to the lower curved surface 102, it is also beneficial to be attached to the upper end surface of the support post 31 ⁇ Close connection.
  • the sensing element 40 of the flexible thin film structure is also prone to deformation, that is, the sensing element 40 is more stable and reliable during operation.
  • the sensing element 40 may use other sensor elements that are smaller and can be arranged on a curved surface.
  • an upper concave cavity 11 is provided on the top of the middle flexible layer 10, the bottom surface of the upper concave cavity 11 is the upper curved surface 101, and the upper hard layer 20 is accommodated in the upper cavity 11.
  • the arrangement of the upper cavity 11 can reduce the thickness of the entire sensor when the upper hard layer 20 is bonded to the middle flexible layer 10, so that the structural design of the sensor is more optimized.
  • the outer surface of the upper hard layer 20 cooperates with the top surface of the top of the middle flexible layer 10 to form a surface suitable for joint connection.
  • a concave cavity 12 is provided at the bottom of the middle flexible layer 10, the cavity bottom surface of the concave cavity 12 is the lower curved surface 102, and the lower hard layer 30 is accommodated in the concave cavity 12.
  • the arrangement of the lower cavity 12 can make the lower hard layer 30 and the middle flexible layer 10 fit together, which is also beneficial to the reduction of the thickness of the entire sensor and the optimization of the structural design of the sensor.
  • the outer surface of the lower hard layer 30 cooperates with the bottom surface of the bottom of the middle flexible layer 10 to form a surface suitable for joint connection.
  • the embodiment of the present invention also provides a contact stress measurement method for a three-dimensional force sensor of a knee joint prosthesis pad, which is used to measure the three-dimensional force sensor of the knee joint prosthesis pad described above, and includes the following steps:
  • the contact stress measurement method of the three-dimensional force sensor of the knee joint prosthesis pad can measure the three-dimensional contact force between the joints, not just the component in a certain direction, and the tibiofemoral joint can be calculated by the algorithm
  • the method for measuring the contact stress of the knee joint prosthesis pad three-dimensional force sensor includes the following steps:

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Abstract

一种膝关节假体垫片三维力传感器及接触应力测量方法。膝关节假体垫片三维力传感器可以应用于胫股关节之间，包括中间柔弹性层(10)、上硬质层(20)和下硬质层(30)，中间柔弹性层(10)具有上曲面(101)和下曲面(102)，上曲面(101)或者下曲面(102)上设置有若干个感应元件(40)；上硬质层(20)的形状与上曲面(101)的形状相适配并贴合于上曲面(101)上；下硬质层(30)的形状与下曲面(102)的形状相适配并贴合于下曲面(102)上。通过算法可以计算出胫股关节之间接触力合力的大小方向和位置，使得测得的数值更加精准且能够计算出关节接触应力的三维方向合力，反映出更加真实的应力分布，为医生判断关节间受力分布情况以及软组织平衡环节提供了量化的指导。

Description

膝关节假体垫片三维力传感器及其接触应力测量方法 技术领域
本发明属于医疗器械技术领域，尤其涉及一种膝关节假体垫片三维力传感器及其接触应力测量方法。
背景技术
软组织平衡是全膝关节置换术(total knee arthroplasty，TKA)中的重要环节。其处理的好坏直接影响到术后膝关节的稳定性及功能，随着国内外研究的广泛开展，人们对软组织平衡的认识逐渐加深。在TKA中，所谓软组织平衡，涉及到的主要是膝关节韧带、关节囊等稳定静力结构，即追求的是“韧带平衡”，强调在正确截骨基础上，通过松解韧带、关节囊等起点或止点，使关节恢复正常的力线排列，从而恢复正常的关节面接触点。而在传统的手术过程中，软组织平衡的主要方法是通过测量关节间隙间接评估平衡情况。
随着计算机辅助技术的发展，针对患者制定个性化的手术方案成为可能。传统的关节置换术中的软组织平衡过程大多依据医生主观经验，为了给医生提供新的更可靠的评估方法，有些学者或企业开展了膝关节假体垫片传感器的研究。
美国专利申请US2013/0079668A1中公开了一种高精度膝关节内智能垫片传感器(smart trials)，该传感器采用电容式感应原理。传感器外形与标准假体形状一致，力首先作用在外壳上表面上，由于外壳材料具有一定柔性，形变后将力传递至三角形压板上，压板下是布置有电容式感应元件的底板。左右两个侧室分别有三个感应元件，由于平面上集中力的位置和大小可由三点的受力大小和位置计算得到，这款假体垫片传感器的软件界面上可以实时显示假体垫片传感器两侧室的集中力作用点和大小。
文献《A wireless force measurement system for total knee arthroplasty》 (IEEE Trans Inform Technol Bi-omed，2012)中介绍了一个由北京积水潭医院与清华大学微电子研究所联合研制的膝关节应力无线检测系统(Wireless Force Measurement System，WFMS)测量术中膝关节内应力分布。WFMS由三部分组成：膝关节内智能垫片(smart trial)、信号接收器和结果显示终端组成。其中智能垫片由两部分组成：内部集成电路和聚乙烯外壳。聚乙烯外壳其表面形状与真实聚乙烯垫片完全相同，长、宽、厚度等型号也与相应真实垫片完全相同。可通过使用厚度调节薄片使智能垫片的厚度与真实假体相同。聚乙烯外壳内部容纳集成电路板，电路板上包含电源、传感器、信号发射器和开关等元器件，其内外两侧各均匀分布四个力学传感器，可将位移信号转化为电子信号。当智能垫片放置到膝关节内，可将膝关节内应力转化为无线电信号发送到信号接收器，接收器将信息传递给电脑终端，经过软件计算和处理，以内外侧应力值(单位：N)的形式显示在屏幕上。术者即可通过终端屏幕所显示的内外侧应力大小来评估不同角度关节内应力分布和软组织平衡情况。据报道，该应力测量系统的测量精确度误差＜4％，重复测量误差＜5％。
然而，现有的膝关节假体垫片传感器只能测量关节接触应力的一个方向的分量大小，由于关节假体垫片的实际形状为曲面，一维方向的集中力的位置和大小往往不能反映真实的应力分布状况。
技术问题
本发明的目的在于提供一种膝关节假体垫片三维力传感器及其接触应力测量方法，旨在解决现有技术中的膝关节假体垫片传感器存在只能测量关节接触应力的一个方向的分量大小导致其无法反映真实的应力分布的技术问题。
技术解决方案
为实现上述目的，本发明采用的技术方案是：一种膝关节假体垫片三维力传感器，包括：
中间柔弹性层，所述中间柔弹性层具有上曲面和下曲面，所述上曲面或者所述下曲面上设置有若干个感应元件；
上硬质层，所述上硬质层的形状与所述上曲面的形状相适配并贴合于所述上曲面上；
下硬质层，所述下硬质层的形状与所述下曲面的形状相适配并贴合于所述下曲面上。
进一步地，所述下硬质层上设置有若干与各所述感应元件位置对应的支撑柱；
当所述上曲面上设置有若干个所述感应元件时，各所述支撑柱均与所述下曲面贴合；
当所述下曲面上设置有若干个所述感应元件时，各所述支撑柱分别与各所述感应元件贴合。
进一步地，各所述感应元件均靠近所述下曲面的周缘间隔设置。
进一步地，所述支撑柱的上端面的形状与所述下曲面对应位置的形状相适配。
进一步地，所述中间柔弹性层为硅胶层，所述上硬质层和所述下硬质层均为聚乙烯层。
进一步地，所述硅胶层和所述聚乙烯层均通过3D打印制成。
进一步地，所述感应元件为柔性薄膜感应元件。
进一步地，所述中间柔弹性层的顶部设有上凹腔，所述上凹腔的腔底面为所述上曲面，所述上硬质层容置于所述上凹腔内。
进一步地，所述中间柔弹性层的底部设有下凹腔，所述下凹腔的腔底面为所述下曲面，所述下硬质层容置于所述下凹腔内。
本发明的有益效果：本发明的膝关节假体垫片三维力传感器，整体结构为硬-软-硬三层式结构，而设置在中间柔弹性层的上曲面或者下曲面上的各个感应元件可以根据实际感应点进行布置，由于自身的可变性能力，使得每个感应元件输出的力信号加上所在位置的法线方向提供了一个三维力信号，通过算法可以计算出胫股关节之间接触力合力的大小方向和位置，使得测得的数值更加精准且能够计算出关节接触应力的三维方向合力，反映出更加真实的应力分布，为医生判断关节间受力分布情况以及软组织平衡环节提供了量化的指导。
本发明采用的另一技术方案是：一种膝关节假体垫片三维力传感器的接触应力测量方法，其用于测量上述的膝关节假体垫片三维力传感器，包括以下步骤：
S01：通过拟合得到所述中间柔弹性层、所述上硬质层和所述下硬质层的表面形状的曲面方程f(x,y,z)＝0，每个感应点的坐标为(x i,y i,z i)(i＝1,2,3,4,5,6,7……m)，对应的法线方向为
Figure PCTCN2019124328-appb-000001
单位化后三个分量记为
Figure PCTCN2019124328-appb-000002
输出的力信号大小为F i；其中，i表示感应元件的数量；
S02：设集中力的坐标为(x 0,y 0,z 0)，合力大小方向为各力的矢量和
Figure PCTCN2019124328-appb-000003
根据合力求得单位方向向量n＝(n x,n y,n z)；
S03：根据力矩平衡求出集中力点位置(x 0,y 0,z 0)：
Figure PCTCN2019124328-appb-000004
有益效果
本发明的膝关节假体垫片三维力传感器的接触应力测量方法，能够测量出关节间三维方向的接触合力，而不仅仅是某一方向的分量，通过算法可以计算出胫股关节之间接触力合力的大小方向和位置，使得测得的数值更加精准且能够计算出关节接触应力的三维方向合力，反映出更加真实的应力分布，为医生判断关节间受力分布情况以及软组织平衡环节提供了量化的指导。
附图说明
为了更清楚地说明本发明实施例中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动性的前提下，还可以根据这些附图获得其他的附图。
图1为本发明实施例提供的膝关节假体垫片三维力传感器的结构示意图。
图2为本发明实施例提供的膝关节假体垫片三维力传感器的结构分解示意图。
图3为本发明实施例提供的膝关节假体垫片三维力传感器的中间柔弹性层的结构示意图。
图4为本发明实施例提供的膝关节假体垫片三维力传感器的局部结构示意图。
其中，图中各附图标记：
10—中间柔弹性层      11—上凹腔        12—下凹腔
20—上硬质层          30—下硬质层      31—支撑柱
40—感应元件          101—上曲面       102—下曲面。
本发明的实施方式
下面详细描述本发明的实施例，所述实施例的示例在附图中示出，其中自始至终相同或类似的标号表示相同或类似的元件或具有相同或类似功能的元件。下面通过参考附图1～4描述的实施例是示例性的，旨在用于解释本发明，而不能理解为对本发明的限制。
在本发明的描述中，需要理解的是，术语“长度”、“宽度”、“上”、“下”、“前”、“后”、“左”、“右”、“竖直”、“水平”、“顶”、“底”“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本发明和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本发明的限制。
此外，术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括一个或者更多个该特征。在本发明的描述中，“多个”的含义是两个或两个以上，除非另有明确具体的限定。
在本发明中，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”、“固定”等术语应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或成一体；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本发明中的具体含义。
如图1～4所示，本发明实施例提供的一种膝关节假体垫片三维力传感器，其可以应用于胫股关节之间，该传感器外形与TKA手术过程中植入股骨和胫骨之间的标准假体垫片形状一致，在正式植入假体垫片前，先将膝关节假体垫片传感器放置在患者胫股关节间，模拟测量置换后的关节间应力分布情况。与目前的现有的关节垫片传感器相比，本发明实施例的传感器的优点在于能够测量出关节间三维方向的接触合力，而不仅仅是某一方向的分量，同时独特的软硬结合三层结构设计很好的保证了力自上而下良好准确的传递，辅以曲面集中力算法，能够计算出合力大小方向和作用位置，结合膝关节屈膝过程的动力学模型为软组织平衡这一手术环节提供量化指导，即为医生判断关节间受力分布情况以及软组织平衡环节提供了量化的指导。
具体地，膝关节假体垫片三维力传感器包括中间柔弹性层10、上硬质层20和下硬质层30，三层结构贴合固定连接，整体结构形状与标准假体形状完全一致。其中，上硬质层20和下硬质层30的形状分别与对应的胫股关节的关节面相适配。
进一步地，如图2～3所示，所述中间柔弹性层10具有上曲面101和下曲面102，上曲面101和下曲面102的设置可以分别用于与上硬质层20和下硬质层30适配连接。其中，所述上曲面101或者所述下曲面102上设置有若干个感应元件40，即根据实际需求可以将各个感应元件40设置在上曲面101或者下曲面102；所述上硬质层20贴合于所述上曲面101上，当上硬质层20受力后，会将该力传递至中间柔弹性层10上，由于中间柔弹性层10具有良好的接触特性，从而使得各感应元件40输出的力信息带有方向信息，即各感应元件40的法线方向；所述下硬质层30贴合于所述下曲面102上，下硬质层30的设置保证了压力完全分布在感应点上(即感应元件40设置的位置)。
在一个实施例中，所述上硬质层20的形状与所述上曲面101的形状相适配，所述下硬质层30的形状与所述下曲面102的形状相适配，如此设计可以保证故中间柔弹性层10能够与上硬质层20和下硬质层30完全贴合，并使得上硬质层20的受力能够均匀的传递。
更具体地，本发明实施例的膝关节假体垫片三维力传感器的整体结构为硬-软-硬三层式结构，而设置在中间柔弹性层10的上曲面101或者下曲面102上的各个感应元件40可以根据实际感应点进行布置，由于自身的可变性能力，使得每个感应元件40输出的力信号加上所在位置的法线方向提供了一个三维力信号，通过算法可以计算出胫股关节之间接触力合力的大小方向和位置，使得测得的数值更加精准且能够计算出关节接触应力的三维方向合力，反映出更加真实的应力分布，为医生判断关节间受力分布情况以及软组织平衡环节提供了量化的指导。
其中，感应元件40的数量根据实际需求设定，例如可以是六个、七个、八个或者九个等。
在一个实施例中，如图2和图4所示，所述下硬质层30上设置有若干与各所述感应元件40位置对应的支撑柱31。每个感应元件40的设置位置即为一个感应点，而下硬质层30的设置位置也刚好对应各个感应点。
具体地，当所述上曲面101上设置有若干个所述感应元件40时，各所述支撑柱31均与所述下曲面102贴合。或者，当所述下曲面102上设置有若干个所述感应元件40时，各所述支撑柱31分别与各所述感应元件40贴合。如此，通过硬质结构的支撑柱31支撑在各个感应点上，那么可以有效地保证压力完全分布在感应点上(即感应元件40设置的位置)，更进一步地提升对测量并计算出的合力大小方向和作用位的精准度。
如图2～4所示，当下硬质层30上设置有支撑柱31时，中间柔弹性层10的底部优选设置有台阶结构(具体参阅图3)，台阶结构具有两个高度不一致的表面(高度差可以相等于支撑柱31的高度)，感应元件40可以设置在一个高度的表面上，而下硬质层30设置有支撑柱31的表面且与另外一个高度的表面贴合。
膝关节假体垫片三维力传感器在受力时，其感应点多集中在传感器的周缘位置。在一个实施例中，将各所述感应元件40均靠近所述下曲面102的周缘间隔设置。这样可以准备对应各个感应点设置。
当然，在其他实施例中，根据实际需求，可以将感应元件40设置在非靠近下曲面102的周缘的位置。只要在在曲面上能够实现集中力大小和位置的计算即可，以此拓展三点测力算法。
在一个实施例中，所述支撑柱31的上端面的形状与所述下曲面102对应位置的形状相适配。如此，可以确保支撑柱31与下曲面102或者下曲面102上设置的感应元件40能够完全贴合，确保整个传感器结构的稳定性和可靠性。
在一个实施例中，优选地，所述中间柔弹性层10为硅胶层，中间柔弹性层10采用硅胶材料制造制成。硅胶材料的柔性保证了感应元件40能够与上硬质层20或者下硬质层30之间具有良好的接触。当然，在其他实施例中，硅胶材料也可以使用其他满足要求的柔弹性材料代替。
进一步地，所述上硬质层20和所述下硬质层30均为聚乙烯层。通过聚乙烯材料制成上硬质层20和下硬质层30，一方面易于成型，另外形成的层结构的硬度适中，与硅胶材料制成的中间柔弹性层10能够形成完美的结合。
在一个实施例中，所述硅胶层和所述聚乙烯层均通过3D打印制成。也就是说，本实施例中的传感器的三层结构均可采用3D打印工艺制造形成，如此 可以快速生产，且成本低廉。另外，层结构的形状也容易设计成型，实用性强。
在一个实施例中，优选地，所述感应元件40为柔性薄膜感应元件。即，整个感应元件40为柔性薄膜结构，柔性薄膜结构有利于贴合在上曲面101或者下曲面102上，并且当其贴合在下曲面102上时，也有利于与支撑柱31的上端面贴合连接。
同时，柔性薄膜结构的感应元件40也容易发生形变，即，感应元件40工作时的稳定性更加，也更加可靠。
当然，在其他实施例中，感应元件40可以采用其他体积较小并且可以布置在曲面上的传感器元件。
在一个实施例中，如图2所示，所述中间柔弹性层10的顶部设有上凹腔11，所述上凹腔11的腔底面为所述上曲面101，所述上硬质层20容置于所述上凹腔11内。上凹腔11的设置可以使得上硬质层20与中间柔弹性层10贴合时，减小整个传感器的厚度，让传感器的结构设计更加优化。上硬质层20的外表面与中间柔弹性层10的顶部的顶面相配合形成适合与关节连接的面。
在一个实施例中，如图3所示，所述中间柔弹性层10的底部设有下凹腔12，所述下凹腔12的腔底面为所述下曲面102，所述下硬质层30容置于所述下凹腔12内。同理，下凹腔12的设置可以使得下硬质层30与中间柔弹性层10贴合时，同样有利于整个传感器的厚度减小设置，让传感器的结构设计更加优化。下硬质层30的外表面与中间柔弹性层10的底部的底面相配合形成适合与关节连接的面。
本发明实施例还提供了一种膝关节假体垫片三维力传感器的接触应力测量方法，其用于测量上述的膝关节假体垫片三维力传感器，包括以下步骤：
S01：通过拟合得到所述中间柔弹性层10、所述上硬质层20和所述下硬 质层30的表面形状的曲面方程f(x,y,z)＝0，每个感应点的坐标为(x i,y i,z i)(i＝1,2,3,4,5,6,7……m)，对应的法线方向为
Figure PCTCN2019124328-appb-000005
单位化后三个分量记为
Figure PCTCN2019124328-appb-000006
输出的力信号大小为F i；其中，i表示感应元件40的数量；
S02：设集中力的坐标为(x 0,y 0,z 0)，合力大小方向为各力的矢量和
Figure PCTCN2019124328-appb-000007
根据合力求得单位方向向量n＝(n x,n y,n z)；
S03：根据力矩平衡求出集中力点位置(x 0,y 0,z 0)：
Figure PCTCN2019124328-appb-000008
本发明实施例的膝关节假体垫片三维力传感器的接触应力测量方法，能够测量出关节间三维方向的接触合力，而不仅仅是某一方向的分量，通过算法可以计算出胫股关节之间接触力合力的大小方向和位置，使得测得的数值更加精准且能够计算出关节接触应力的三维方向合力，反映出更加真实的应力分布，为医生判断关节间受力分布情况以及软组织平衡环节提供了量化的指导。
具体地，当感应元件40的数量为七个时，即m为7，那么，膝关节假体垫片三维力传感器的接触应力测量方法包括以下步骤：
S01：通过拟合得到所述中间柔弹性层10、所述上硬质层20和所述下硬质层30的表面形状的曲面方程f(x,y,z)＝0，每个感应点的坐标为(x i,y i,z i)(i＝7)，对应的法线方向为
Figure PCTCN2019124328-appb-000009
单位化后三个分量记为
Figure PCTCN2019124328-appb-000010
输出的力信号大小为F i；
S02：设集中力的坐标为(x 0,y 0,z 0)，合力大小方向为各力的矢量和
Figure PCTCN2019124328-appb-000011
根据合力求得单位方向向量n＝(n x,n y,n z)；
S03：根据力矩平衡求出集中力点位置(x 0,y 0,z 0)：
Figure PCTCN2019124328-appb-000012
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种膝关节假体垫片三维力传感器，其特征在于：包括：
    中间柔弹性层，所述中间柔弹性层具有上曲面和下曲面，所述上曲面或者所述下曲面上设置有若干个感应元件；
    上硬质层，所述上硬质层的形状与所述上曲面的形状相适配并贴合于所述上曲面上；
    下硬质层，所述下硬质层的形状与所述下曲面的形状相适配并贴合于所述下曲面上。
  2. 根据权利要求1所述的膝关节假体垫片三维力传感器，其特征在于：所述下硬质层上设置有若干与各所述感应元件位置对应的支撑柱；
    当所述上曲面上设置有若干个所述感应元件时，各所述支撑柱均与所述下曲面贴合；
    当所述下曲面上设置有若干个所述感应元件时，各所述支撑柱分别与各所述感应元件贴合。
  3. 根据权利要求1所述的膝关节假体垫片三维力传感器，其特征在于：各所述感应元件均靠近所述下曲面的周缘间隔设置。
  4. 根据权利要求1所述的膝关节假体垫片三维力传感器，其特征在于：所述支撑柱的上端面的形状与所述下曲面对应位置的形状相适配。
  5. 根据权利要求1所述的膝关节假体垫片三维力传感器，其特征在于：所述中间柔弹性层为硅胶层，所述上硬质层和所述下硬质层均为聚乙烯层。
  6. 根据权利要求5所述的膝关节假体垫片三维力传感器，其特征在于：所述硅胶层和所述聚乙烯层均通过3D打印制成。
  7. 根据权利要求1所述的膝关节假体垫片三维力传感器，其特征在于： 所述感应元件为柔性薄膜感应元件。
  8. 根据权利要求1～7任一项所述的膝关节假体垫片三维力传感器，其特征在于：所述中间柔弹性层的顶部设有上凹腔，所述上凹腔的腔底面为所述上曲面，所述上硬质层容置于所述上凹腔内。
  9. 根据权利要求1～7任一项所述的膝关节假体垫片三维力传感器，其特征在于：所述中间柔弹性层的底部设有下凹腔，所述下凹腔的腔底面为所述下曲面，所述下硬质层容置于所述下凹腔内。
  10. 一种膝关节假体垫片三维力传感器的接触应力测量方法，其特征在于：用于测量权利要求1～9任一项所述的膝关节假体垫片三维力传感器，包括以下步骤：
    S01：通过拟合得到所述中间柔弹性层、所述上硬质层和所述下硬质层的表面形状的曲面方程f(x,y,z)＝0，每个感应点的坐标为(x i,y i,z i)(i＝1,2,3,4,5,6,7……m)，对应的法线方向为
    Figure PCTCN2019124328-appb-100001
    单位化后三个分量记为
    Figure PCTCN2019124328-appb-100002
    输出的力信号大小为F i；其中，i表示感应元件的数量；
    S02：设集中力的坐标为(x 0,y 0,z 0)，合力大小方向为各力的矢量和
    Figure PCTCN2019124328-appb-100003
PCT/CN2019/124328 2018-12-14 2019-12-10 膝关节假体垫片三维力传感器及其接触应力测量方法 WO2020119683A1 (zh)

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