Study Of A Method For Measuring Apparent Tissue Strain Of Knee Based On LabVIEW Imaging Processing Technology

Knee is a major joint in the body, and its biomechanical behavior is extremely important for body stability and motion. However, the current methods to study knee biomechanics are mostly complicated and costly. Thus, it is necessary to develop new experimental methods that are easy to build and less expensive. Here, described is a new method that measures the apparent tissue strain of knee during flexion based on imaging analysis technique using LabVIEW. This method consists of three components: knee flexion loading, flexion measurement, and strain measurement via surface marker identification. With this method non-contact measurement of apparent tissue strain of knew can be done dynamically during flexion, and it is easy to operate, highly reliable, The design and building of the measurement system are described as follows.①A loading system of knee flexion was designed. Knee was held with a variety of clamps, and driven in flexion movement by a mechanical arm and a stepper motor. The stepper motor was controlled electronically with an embedded micro-control unit (MCU) via an interactive interface on PC based on LabVIEW, thus to achieve accurate control of the direction, speed and the duration of the flexion.②A system to measure flexion angle without contacting the knee was designed. A straight rigid dial was attached onto the moving section of the knee as a marking of its position. By analyzing the image of this marking line, the angle of flexion was obtained. In the meanwhile, the measured angle was be used as the feedback to control the loading system to drive knee flexion at the preset magnitude.③A tissue strain measurement system was designed based on the technique of extracting image feature. A video camera system in the proper orientation was used to record images of knee surface that was marked by an array of points in an ordered list. Using image processing technology, coordinates of the marker points were identified from the recorded images, and the corresponding displacements of the marker points over time were measured. From the displacement data, the apparent tissue strain, or knee surface deformation, was calculated. In addition, the marker identification technique was tested to extract coordinates of magnetic microbeads from recorded images, and the results confirmed the effectiveness of the system.④The flexion-loading and measuring system, tissue strain measurement system were integrated and used to study the biomechanical properties of knee tissue (swine hoof, n=12) over the area of patellar incision. The apparent tissue strain of the swine hoof during flexion was measured at different flexion magnitudes, with different methods of patellar incision and suture. By comparing the strain fields in different cases, different surgical procedures of knee incision could be quantitatively evaluated.In summary, a new method and system of non-contact dynamic fast measurement is realized for measuring apparent strain on the surface of knee during flexion. This method is easy to operate and highly reliable, economical for popularization and data-mining, and thus provides an effective way to study biomechanical properties of knee, which is useful for clinical guidance of knee surgery and rehabilitation.