Real-time interfacial load monitoring and tracking between the composite prosthetic socket and residual limb for below-knee amputees

© 15th International Conference on Condition Monitoring and Machinery Failure Prevention Technologies, CM 2018/MFPT 2018. All rights reserved. Real time-in-service interfacial load measurement and load tracking between prosthetic socket and the residual limb is of paramount importance. Noroozi et al proposed an inverse method approach using ANN to predict the magnitude and location of the interfacial load between prosthetic socket and the residual limb from the structural response of the socket to the normal internal load due to contact between the stump and the socket. Here the socket mechanical properties act as the transfer function between the forces acting normal to the internal surface of the socket forces and the resultant strains generated on the external surface of the socket. Using this method, it is possible to use the external strains to predict the internal load that caused the strain. With this method, there will be no need for the socket or tissue properties or the exact socket thickness. Using this technique, one can simply transform everyone's socket into their own dedicated transducer suitable for measuring, tracking and monitoring the resultant interfacial load on the internal surfaces of the socket for that user. Currently, all socket interfacial load measurement systems require tactile sensors which require the prior knowledge of the location of the contact points. This makes it impossible for the tactile sensor to predict the magnitude and location of high-pressure points. Alternative tools are tactile sensor placed in liners or drilled and mounted through the socket wall, or total surface bearing ones that are subjective and not suitable for everyday use. For that reason, they require the knowledge of the contact point or areas of high load intensities. The proposed new system requires none of the above constraints and due to its unique design, it is immune to the changes in the overall boundary conditions, making it an invaluable clinical system

Assessment of key parameters on the performance of the deltoid muscle in reverse shoulder arthroplasty – a modeling and simulation based study

Reverse shoulder arthroplasty (RSA), in which anatomic concavities of glenohumeral (GH) joint are inverted, is a popular treatment of arthritic shoulders with deficient rotator cuff. The correct positioning of the glenohumeral center of rotation and initial setting of the deltoid length (Deltoid Tension) plays an important role in the outcome of the RSA. A study of the key literature has shown that despite common use of RSA, its biomechanical characteristics during motion are not fully understood. This study investigates the influence of some of the key parameters on the intensity of the moment in a shoulder after RSA during abduction in scapular plane. The kinematics after RSA are then compared with the anatomic shoulder kinematics and differences are discussed. Mathematical models of both the anatomical and reverse shoulder (RS) were developed in MATLAB and in MSC ADAMS. The anatomical and RSA geometries were defined using measurements obtained from X-ray and magnetic resonance imaging (MRI) images of the shoulder girdle. The results show that in RSA, the intensity of the moment generated in the GH joint improves. However, this improvement does not show a constant trend and its intensity can dramatically decrease in higher GH joint abduction

Visualising kinematics of an elastic Ossur ESR prosthetic foot using novel low-cost optical tracking systems

A novel method of measuring kinematics of elastic body is the subject of this investigation. Unlike kinematics of rigid body large elastic deformation tends to modify the dynamics of motion. In the case of amputee runner the change in kinematics of the foot depends on the stiffness, body mass and running beat frequency. Current measurement techniques, such as gait analysis assumes rigid elements. Currently there are inertia measurement unit (IMU) based systems that uses accelerometers and gyro to determine acceleration, velocities and orientations of the sensors. They are not capable of measuring changes in lengths or positions of the objects that they are attached to. For that reason predicting velocities and displacement by integrating acceleration is not always viable due to time step limits of the integrations that are necessary. Here a new optical device is developed and presented that is accurate and is practically error free to monitor Foot elastic deformation. In this paper the Dynamic elastic response of Ossur Running foot is being investigated using this device. The data generated show complete phase synchronisation with IMU but much better accuracy in terms of velocity and relative displacement of the feet due to flexure as a result of elastic response to Impulse

Kinematics study of the deltoid in Reverse Shoulder Arthroplasty using Standard Pre and Post-Operative X-Rays

© 15th International Conference on Condition Monitoring and Machinery Failure Prevention Technologies, CM 2018/MFPT 2018. All rights reserved. For patients with deficient rotator cuff Reverse Shoulder Arthroplasty, in which the centre of rotation of the glenohumeral joint is repositioned, is a popular treatment. However, for optimal restoration of motion after RSA, the correct implant selection and positioning within the bones is critical for a successful surgical outcome. This paper examines current practice of implant insertion and predicts what would be its mechanical advantage by using a developed graphical user interface importing pre and post-operative shoulder X-rays. Standardised X-rays of 8 shoulder griddle pre and post-operative were provided in the true anteroposterior (Grashey) view. Images were then calibrated and key geometrical parameters were identified in all images. A mathematical model for deltoid excursion and deltoid lever arm in full abduction was developed based on the mechanical model of the shoulder in order to investigate its performance (deltoid) in both native and reverse shoulders. Results showed that the deltoid lever arm was improved in reverse shoulders for lower abductions. In higher abductions a sudden drop in the lever arm's mechanical advantage was observed. It was also observed that more deltoid excursion occurred in full abduction of reverse shoulders compared to native shoulders