光学定位系统是手术导航设备中的核心部件,本文针对基于FPGA自行研制的红外光学定位跟踪系统设计了几种硬件加速方法.使用SoPC作为计算单元的原有系统能够达到亚毫米级别的定位精度,但是定位跟踪速率不足,无法满足实际应用需求.为克服SoPC计算能力较弱的问题,本文使用浮点数自定义指令集、紧密耦合寄存器 (TCM) 和多核处理等几种硬件加速方法,使红外光学定位跟踪系统的三维重建速度获得了明显的提升,实验数据表明速度提升18倍.硬件加速之后的系统性能可以支持高达32个标志点以60fps帧率进行的实时定位和跟踪,满足手术导航系统对运动跟踪速率的要求.

Objective A new type of tibial-femoral force-balancing telemetry device was developed for measuring force balance on the tibial-femoral contact surface in knee joint. Method The force-balance telemetry device was designed imitating the configuration of tibial part of total knee prosthesis,in which force sensors and telemetry circuit were embedded. During total knee arthroplasty(TKA),this device was implanted as a tibial prosthesis to measure tibial-femoral force while the knee joint was being placed at different angles. The tension balance was adjusted by releasing soft tissue around knee joint. Results The results indicat that this device has advantage of high accuracy for force measurement (r0.98,RMS= 65 g),which is sufficient to meet clinical demand. Conclusions The measurement of force balance on the tibial-femoral contact surface with telemetry device can provide new insight into the estimation of optimal knee prosthesis position and selection of appropriate polyethylene insert.

This paper presents several hardware accelerating methods for an infrared optical tracking system based on FPGA (Field Programmable Gate Array). The system is designed for Image-Guided Surgical Navigation. Since FPGA and SoPC (System on Programming Chip) have the inherent flexibility and ease of implemented, system architecture together with PCB (Printed Circuit Board) design can be greatly simplified while the reliability can be increased. With the hardware accelerating methods, which are Floating-Point Custom Instruction, Tightly Coupled Memory (TCM) and Multiprocessor, calculating speed of 3D reconstruction gets a significant promotion of 18 times according to experiment results. This overcomes the lack of dominant frequency and floating-point computational capability in Altera soft processor Nios II. However, the benefit of speed is obtained at the cost of hardware resources, which should be considered. The hardware acceleration and its testing performance could theoretically support up to 32 markers real-time location with a frame rate of 60fps (frame per second).

Background: Fixed-bearing posterior-stabilized (PS) total knee arthroplasty (TKA) has been used in Asian countries for several years, but few studies have investigated differences in the kinematic properties of the patellar tendon after standard PS TKA as compared to high-flex PS TKA. Purpose: To quantify the in vitro three-dimensional (3D) kinematics of the patellar tendon during passive high flexion and full extension before and after two different types of PS TKAs. Methods: Six fresh-frozen cadaveric knees were tested under the following conditions: the unaltered state, status-post traditional PS prostheses (Simth-nephew GENESIS II) replacement, and status-post high-flexion PS prostheses replacement. The soft tissue around the knee and the quadriceps muscle were preserved, then tested under the load of a specific weight in an Oxford knee rig. We designed a specialized rigid body with four active markers fixed to each bone to track the 3D passive motion of the cadaveric knees. Flexion and extension was controlled by the knee rig and captured by an Optotrak Certus™ high precision optical tracking system. The attachment sites of the patellar tendon were registered as virtual markers to calculate the 3D kinematics. Results: The patellar tendon of the unaltered knee and both TKA knees showed similar deformation. We found the length of the patellar tendon changed significantly during a motion from full extension to 30°, but there was no significant change in length while undergoing a motion from 30° to full flexion. Both the sagittal plane and coronal plane angles of the patellar tendon decreased after PS TKAs. There was no significant difference in patellar tendon kinematics between the two types of PS TKAs. Conclusion: We believe the changes observed in the sagittal plane and coronal plane angles of the patellar tendon after PS TKAs may influence the extensor mechanism and be an important cause of patella-femoral complications. These data may- be used to assess patella-femoral complications after surgery so as to improve the design of high-flexion TKAs for Asians and achieve long-term stability.

The revision of total hip arthroplasty (THA) is becoming an increasingly common procedure around the world. The extended trochanteric osteotomy (ETO) has proved to be an effective way in revision of THA. Four generations of trochanteric osteotomy fixation systems have been developed, all of which has its own clinical application. However, few studies on the biomechanical stability of the above fixation methods have been reported, though many clinical follow-up studies showed some postoperative functional differences among them. Research in this field is mainly subject to constraints of measurement devices and 3D motion analysis. We designed a synchronous testing approach to acquire the tension data loaded to the greater trochanter and minimal rotation or migration of osteotomy fragment which could not be solved by strain gauge method. Active markers were designed to precisely track proximal femoral bed and the osteotomy fragment in 3D space. Six cadaver femurs constructed as vitro biomechanical models were chosen for a preliminary study. Each femur underwent the steps of prosthesis implanting, ETO and a series of five fixation methods in a random order with 2 wires, 3wires, 2 wires and a short claw plate,2 cables and a short claw plate, and a long claw plate. We also gave a preliminary result of the displacement of fragment and the stiffness of femur after ETO in this paper. Further clinical significance remains to be discussed.

This paper proposed a method of using virtual markers to track the movement of the articular bearing surfaces of femur, tibia and patella simultaneously. With this method, the femur, tibia and patella were treated as three rigid body connected by soft tissue and thus the articular surface moves with corresponding bone in three dimensional (3D) space. The contact kinematics of articular bearing surface can be figured out by track the position and orientation of bones during knee flexion. To perform this method, three sets of tracking marker were attached tightly to femur, tibia and patella to track the 3D motion of lower limb. The articular bearing surfaces of knee joint were digitized to create three groups of registered virtual markers associated to the tracking markers of each bone, respectively. During knee flexion, 3D movement of femur, tibia and patella were tracked by capture the motion of tracking markers. Then the 3D coordinate of each virtual marker was calculated using the registration information of virtual markers. Thus, the trajectory of virtual markers could be tracked during knee flexion which indicates the real kinematics of bearing surfaces of knee joint. Three fresh-frozen lower limbs were tested before and after total knee replacement operation using this technique. The test results show that this method could be used to explore the contact condition of articular bearing surfaces accurately.

本文设计了一种测量膝关节屈伸中股骨、胫骨和髌骨关节面的相对位置和接触情况的方法，分析研究关节面的运动。通过在关节面上测量定义一系列虚拟标志点，依据对骨骼运动跟踪的三维动态数据，从而解算关节面的相对运动和接触情况；通过对假体建立高精度的关节面模型，并与虚拟标志点位置进行配准，精确分析关节假体的动态接触情况。实验表明，通过本文方法，可以精确跟踪任意关节角度下股骨、胫骨和髌骨关节面的运动和接触情况。利用虚拟标志点动态跟踪技术，可以测量得到任意关节角度下关节面相对位置和接触的情况，使得对关节面的运动跟踪和分析更加精确。