Investigating the ideal deltoid kinematics and tension in reverse shoulder arthroplasty (RSA).

The shoulder is the one of the most active joints within the human body. Recruited in the majority of daily activities either in active use such as moving/carrying of objects or as a source of stability during locomotion. Therefore painful shoulder or its reduced mobility and function can be very debilitating hence affecting the quality of life. While shoulder pain and restricted motion encompasses a diverse array of pathologies, the most common causes are due to infection, arthritis, or trauma. Arthroplasty (the surgical reconstruction or replacement of a joint) of the shoulder has offered the potential for improved function and pain relief where the native structures have been damaged. The conventional total shoulder replacement, however, is not beneficial for all patients and may result in further pain and limited motion in persons with arthritic shoulders with a deficient rotator cuff. For these patients Reverse Shoulder Arthroplasty (RSA), in which anatomic concavities of glenohumeral joint are inverted, is a popular treatment. However, for optimal restoration of motion, the correct positioning of the glenohumeral centre of rotation and initial setting of the deltoid length (Deltoid Tension) must play an important role in the surgery outcome. 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 forces and moments in the shoulder joint before, during and after RSA. These parameters include; geometry, kinematics and muscle passive force measurement (deltoid pretension measurement). To investigate the effect of geometrical changes on kinematics of shoulder after RSA, a musculoskeletal model of the shoulder is developed and simulated. Geometrical parameters of the musculoskeletal model are extracted from previous published studies. Results of the simulation enabled the detection of key parameters in reverse shoulder kinematics and its influence on determining the mechanical advantage of the shoulder mechanism. This identified the need for developing an X-ray imaging protocol and image processing tool that enable surgeons to predict optimum implants insertion position and estimate the performance of the shoulder before planning the operation. Subsequently, an assessment tool was proposed to assess shoulder Range of Motion (ROM) and deltoid muscle activity to both quantify and validate the predicted outcome of the surgery. The main purpose of this study is to measure the passive force exerted on the reverse shoulder joint during surgery as a criterion or measure of deltoid pretension. Hence a force sensor is designed, developed and tested in a custom built joint simulator. As part of this research and to allow objective assessment of the joint, a series of tools/hardware/software were proposed, designed and developed, and then tested and evaluated for effectiveness and functionality. The introduction of a system proposed here provides data which could be recorded in a database along with geometrics and kinematics pre and post operatively, residual force in glenohumeral joint intraoperatively and shoulder performance in terms of range of motion and EMG muscle activity of individual patients pre and post operatively. Such a database in time will enable us to find correlations between these parameters and the outcome of surgery in the long term. It is hoped that this will provide a tool for surgeons in future operations to who choose to use a more quantitative and repeatable way of optimizing the implant size and position accordingly

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

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

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

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

Influences and trends of various shape-capture methods on outcomes in trans-tibial prosthetics : a systematic review

Introduction: In trans-tibial prosthetics, shape-capture methods are employed to create a representation of the residuum. Shape-capture methods can be grouped into the categories of 'hands-on', 'hands-off' and computer-aided design. Objective: This review examines the influences and trends of shape-capture methods on the outcomes of quality, comfort of user and clinical efficiency, in the population of trans-tibial prosthesis users. Study Design: Systematic Review Method: Databases and relevant journals were searched. Participants included trans-tibial prosthetics users/limb models. Interventions included shape-capture methods. Outcomes included quality, comfort of user and clinical efficiency. Results: Overall, 22 papers were evaluated; 8 papers evaluated hands-on and hands-off methods, 2 evaluated computer-aided design and 12 evaluated measurement systems used with shape capture. No papers relating to clinical efficiency were found. Conclusion: Overall evidence was weak in suggesting that effects on outcomes were due to the sole influences of shape capture. However, studies suggest that hands-on methods are dependent on a prosthetist's skill. Hands-off methods, although repeatable, might still require experience to attain a good fit. Computer-aided design studies were mostly done on theoretical models. Shape-capture measurements require more consistent 'gold standards'. The relation between socket fit and comfort is still unclear. Overall, more research is required in each area. Clinical relevance: A good fitting prosthetic socket is crucial for efficient and comfortable use of a prosthesis. To attain the best chances of a good fit, it is important that the characteristics of the residuum are captured as accurately as possible during the initial "shape capture" stage. This paper attempts to categorize and evaluate the existing shape capture methods on their influence and trends on various outcomes - Quality of shape capture, comfort of user and clinical efficiency

Dynamic characterisation of Össur Flex-Run prosthetic feet for a more informed prescription

Background: The current method of prescribing composite Energy Storing and 6 Returning (ESR) feet is subjective and is based only on the amputee’s static body 7 weight/mass. 8 Objectives: The aim is to investigate their unique design features through identifying 9 and analysing their dynamic characteristics, utilising modal analysis, to determine 10 their mode shapes, natural damping and natural frequencies. Full understanding of 11 the dynamic characteristics can inform on how to tune a foot to match an amputee’s 12 gait and body condition. 13 Methods: This paper presents the modal analysis results of the full range of Össur 14 Flex-Run running feet that are commercially available (1LO-9LO). 15 Results: It is shown that both the undamped natural frequency and stiffness increase 16 linearly from the lowest to highest stiffness category of foot. The effect of over-load 17 and under-loading on natural frequencies is also presented. The damping factor for 18 each foot has been experimentally determined and it was found to be ranging 19 between 1.5-2.0%. An analysis of the mode shapes also showed a unique design 20 feature of these feet that is hypothesised to enhance their performance. 21 Conclusions: A better understanding of the feet dynamic characteristics can help to 22 tune the feet to the user’s requirements. 23 (194 words

Exploring the Performance of an Artificial Intelligence-Based Load Sensor for Total Knee Replacements.

Using tibial sensors in total knee replacements (TKRs) can enhance patient outcomes and reduce early revision surgeries, benefitting hospitals, the National Health Services (NHS), stakeholders, biomedical companies, surgeons, and patients. Having a sensor that is accurate, precise (over the whole surface), and includes a wide range of loads is important to the success of joint force tracking. This research aims to investigate the accuracy of a novel intraoperative load sensor for use in TKRs. This research used a self-developed load sensor and artificial intelligence (AI). The sensor is compatible with Zimmer's Persona Knee System and adaptable to other knee systems. Accuracy and precision were assessed, comparing medial/lateral compartments inside/outside the sensing area and below/within the training load range. Five points were tested on both sides (medial and lateral), inside and outside of the sensing region, and with a range of loads. The average accuracy of the sensor was 83.41% and 84.63% for the load and location predictions, respectively. The highest accuracy, 99.20%, was recorded from inside the sensing area within the training load values, suggesting that expanding the training load range could enhance overall accuracy. The main outcomes were that (1) the load and location predictions were similar in accuracy and precision (p > 0.05) in both compartments, (2) the accuracy and precision of both predictions inside versus outside of the triangular sensing area were comparable (p > 0.05), and (3) there was a significant difference in the accuracy of load and location predictions (p < 0.05) when the load applied was below the training loading range. The intraoperative load sensor demonstrated good accuracy and precision over the whole surface and over a wide range of load values. Minor improvements to the software could greatly improve the results of the sensor. Having a reliable and robust sensor could greatly improve advancements in all joint surgeries

Simulation of gait asymmetry and energy transfer efficiency between unilateral and bilateral amputees

Efficient walking or running requires symmetrical gait. Gait symmetry is one of the key factors in efficient human dynamics, kinematics and kinetics. The desire of individuals with a lower-limb amputation to participate in sports has resulted in the development of energy-storing and-returning (ESR) feet. This paper analyses a case study to show the effect of symmetry and asymmetry as well as energy transfer efficiency during periodic jumping between simulated bilateral and unilateral runners. A custom gait analysis system is developed as part of this project to track the motion of the body of a physically active subject during a set of predefined motions. Stance and aerial times are accurately measured using a high speed camera. Gait frequency, the level of symmetry and the non-uniform displacement between left and right foot and their effects on the position of the Centre of Mass (CM) were used as criteria to calculate both peak energies and transformation efficiency. Gait asymmetry and discrepancy of energy transfer efficiency between the intact foot and the ESR are observed. It is concluded that unilateral runners require excessive effort to compensate for lack of symmetry as well as asymmetry in energy transfer, causing fatigue which could be a reason why bilateral amputee runners using ESR feet have a superior advantage over unilateral amputees

Development of a 3D workspace Shoulder Assessment Tool Incorporating Electromyography and an Inertial Measurement Unit - A preliminary study

Traditional shoulder Range of Movement (ROM) measurement tools suffer from inaccuracy or from long experimental set-up times. Recently, it has been demonstrated that relatively low-cost wearable inertial measurement unit (IMU) sensors can overcome many of the limitations of traditional motion tracking systems. The aim of this study is to develop and evaluate a single IMU combined with an Electromyography (EMG) sensor to monitor the 3D reachable workspace with simultaneous measurement of deltoid muscle activity across the shoulder ROM. Six volunteer subjects with healthy shoulders and one participant with a ‘frozen’ shoulder were recruited to the study. Arm movement in 3D space was plotted in spherical coordinates while the relative EMG intensity of any arm position is presented graphically. The results showed that there was an average ROM surface area of 27291±538 deg2 among all six healthy individuals and a ROM surface area of 13571±308 deg2 for the subject with frozen shoulder. All three sections of the deltoid show greater EMG activity at higher elevation angles. Using such tools enables individuals, surgeons and physiotherapists to measure the maximum envelope of motion in conjunction with muscle activity in order to provide an objective assessment of shoulder performance in the voluntary 3D workspace