Yohei Tsumori

A 3-DOF knee joint angle measurement system with inertial and magnetic sensors

Quantitative diagnosis of the knee joint dynamics is required to decrease the inner- and intra-observer variability. This paper proposes a noninvasive, unconstrained and free field of measurement system of 3 degree-of-freedom knee joint angles. The proposed system employs a compound sensor of inertial and magnetic sensors. Based on a rigid-body link model, the proposed method enables a measurement system. The experimental results showed that the proposed method estimated the flexion of knee joint angle with a mean displacement of 1.3 deg.

Analysis of weight-bearing kinematics of posterior-stabilized total knee arthroplasty with novel helical post-cam design.

We developed a new posterior-stabilized total knee arthroplasty (TKA) with a unique post-cam design that induces and accommodates internal tibial rotation with deep knee flexion. To validate the design concept of this system, we conducted an image analysis study employing a computer-aided diagnosis system for 24 TKA-implanted knees. In the analysis, the tibiofemoral relationship in the following 3 postures was evaluated: standing at extension, forward lunge, and kneeling with maximum knee flexion. The results of the image analysis showed achievement of consistent internal rotation of the tibia in deep flexion with a broad contact area at the post-cam interface as intended by the original design concept of this TKA system.

Wearable joint kinematic monitoring system using inertial and magnetic sensors

Wearable joint kinematics monitoring is effective for analyzing daily human behavior, for evaluating the knee functionality in the daily life, etc. This study proposes a new wearable joint kinematics monitoring system using a composite sensor which is composed of inertial and magnetic sensors. For each segment of the joint, the composite sensor is attached. By indentifying the two sets of acceleration and magnetic vector at the center of knee joint, difference of pose between the sensors are estimated. And, all of three joint angles; flexion/extension (f/e) angle, internal/external (i/e) rotation angle and varus/valgus (v/v) angle, are calculated. The proposed system was applied to knee joint kinematic analysis. The measurement accuracy was evaluated by comparing with optical sensor system. The mean error of measuring f/e angle was −1.61 ± 3.09 deg; of measuring i/e angle was 0.93 ± 1.75 deg; and of measuring v/v angle was 1.83 ± 1.79 deg. To demonstrate the applicability of wearable monitoring, the proposed method was applied to measure knee joint angles during walking and during stair-climbing.

Unconstraint Knee Joint Dynamics Estimation System Using Inertial and Magnetic Composite MEMS Sensor

The estimation system of the knee joint angle that decreases the variability caused by the subjective diagnosis of the knee joint disorders has been attracting a considerable attention. This paper proposes an unconstraint knee joint angle measurement system using inertial and magnetic composite MEMS sensor. The proposed system estimated the posture difference between the thigh and shank region from the difference of the measurement vector between the compound sensors attached on the shank and the thigh, respectively, and 3-D knee joint angles can be calculated by applying Grood’s definition. Through experimented results, the knee flexion angle was obtained compared with the true value due to the measurement error of 1.3 deg in average.

2-D/3-D image registration of implanted knee DR images with Kalman filter

Total knee arthroplasty (TKA) is an orthopedic surgery which replaces the damaged knee joint with the artificial one. To diagnose the function of the implanted knee joint, it is effective to estimate 3-D knee kinematics in vivo. There are some conventional methods for estimating kinematics of the implanted knee using 2-D/3-D image registration for X-ray fluoroscopic images and 3-D geometrical models of the knee implant. However, these methods are based on static image analysis although the knee joint continuously moves. This paper proposes an analysis method of the knee kinematics using digital radiography images with Kalman filter. Use of Kalman filter enables us to take into account the continuous knee movement. The experimental results showed that the proposed method estimated the knee joint angles within a mean error of 0.31 deg.

Wavelet Transform Based Quantification of Pivot-Shift Testing Using Inertial and Magnetic Composite MEMS Sensor

Anterior cruciate ligament (ACL) injury and knee osteoarthritis are well-known injuries of the knee joint, and pivot shift is a symptom of the ACL injury. Today, to diagnose the pivot shift phenomenon, the manual testing is examined for the early diagnosis, however, it should be affected by inter- and intra observer variability. This article proposes a novel system for detecting and quantifying the pivot shift phenomenon during pivot-shift testing using inertial and magnetic composite micro electro mechanical systems (MEMS) sensor. The system estimated 3-D acceleration vector caused by the pivot shift phenomenon using wavelet transform. The experimental results indicated that the pivot shift phenomenon was detected and quantified. And, there are correlation between the maximum acceleration of the knee movement at the pivot shift and the conventional evaluation by assessors.