Matthew M. Wernke

Differences in knee flexion between the Genium and C-Leg microprocessor knees while walking on level ground and ramps

BACKGROUND Microprocessor knees have improved the gait and functional abilities of persons with transfemoral amputation. The Genium prosthetic knee offers an advanced sensor and control system designed to decrease impairment by: allowing greater stance phase flexion, easing transitions between gait phases, and compensating for changes in terrain. The aim of this study was to determine differences between the knee flexion angle of persons using the Genium knee, the C-Leg knee, and non-amputee controls; and to evaluate the impact the prostheses on gait and level of impairment of the user. METHODS This study used a randomized experimental crossover of persons with transfemoral amputation using the Genium and C-Leg microprocessor knees (n=25), with an observational sample of non-amputee controls (n=5). Gait analysis by 3D motion tracking of subjects ambulating at different speeds on level ground and on 5° and 10° ramps was completed. FINDINGS Use of the Genium resulted in a significant increase in peak knee flexion for swing (5°, p<0.01, d=0.34) and stance (2°, p<0.01, d=0.19) phases relative to C-Leg use. There was a high degree of variability between subjects, and significant differences still remain between the Genium group and the control groups knee flexion angles for most speeds and slopes. INTERPRETATION The Genium knee generally increases flexion in swing and stance, potentially decreasing the level of impairment for persons with transfemoral amputation. This study demonstrates functional differences between the C-Leg and Genium knees to help prosthetists determine if the Genium will provide functional benefits to individual patients.

The effects of incongruent feedback on bimanual task performance

Previous studies analyzing the effects of incongruent visual and haptic feedback have found differences in the perceived stiffness of an object depending on what modality was delayed. These studies required only unilateral performance of the individual and did not measure functional task completion. Our study evaluated the effects of incongruent visual and haptic feedback during a bimanual pick and place task within a virtual environment using two Phantom Omnis. Subjects were asked to place three different colored spheres into matching colored baskets under various testing conditions. The testing conditions included various temporal delays in either the haptic feedback, visual feedback or both feedback modalities simultaneously. The amount of time required to complete the task as well as the number of spheres broken were recorded for each trial. The results show that delays in either or both of the feedback modalities had a negative effect on the subjects ability to complete the task. The most detrimental effects on task performance were observed when both feedback modalities were simultaneously delayed 133 ms for both the completion time and number of broken spheres.

EFFECTS OF THE GENIUM KNEE SYSTEM ON FUNCTIONAL LEVEL, STAIR AMBULATION, PERCEPTIVE AND ECONOMIC OUTCOMES IN TRANSFEMORAL AMPUTEES

Compared to non-microprocessor knees, the C-Leg microprocessor knee (MPK) is bioenergentically and economically more efficient and safer for transfemoral amputation (TFA) patients. The Genium MPK has demonstrated improvements in perceived function, knee kinematics, and physical functional performance compared to C-Leg. Clinical and health economic analyses have not been conducted with the Genium knee system. The purpose of this study was to determine if laboratory determined benefits of Genium are detectable using common clinical assessments and if there are economic benefits associated with its use. This study utilized a randomized AB crossover study with 60 d follow-up including cost-effectiveness analysis. Twenty TFA patients tested with both knees in mobility and preference measures. Incremental cost-effectiveness ratios (ICER) were calculated based on performance measures. Stair Assessment Index scores improved with Genium. Mean stair completion times and descent stepping rate were not different between knees. Stair ascent stepping rate for C-Leg was greater compared with Genium (p = 0.04). Genium use decreased Four square step test completion time and increased functional level and step activity (p ≤ 0.05). Further, Genium use improved (p ≤ 0.05) function and safety in three out of five Activities of Daily Living (ADL) survey domains. Finally, more subjects preferred Genium following testing. Functional measures were used to calculate ICERs. ICER values for Genium fall within established likely-to-accept value ranges. Compared with C-Leg, Genium use improved stair walking performance, multi-directional stepping, functional level, and perceived function. In this group of community ambulators with TFA, Genium was preferred, and, while more costly, it may be worth funding due to significant improvements in functional performance with ADLs.

Probability density based gradient projection method for inverse kinematics of a robotic human body model

This paper presents the probability density based gradient projection (GP) of the null space of the Jacobian for a 25 degree of freedom bilateral robotic human body model (RHBM). This method was used to predict the inverse kinematics of the RHBM and maximize the similarity between predicted inverse kinematic poses and recorded data of 10 subjects performing activities of daily living. The density function was created for discrete increments of the workspace. The number of increments in each direction (x, y, and z) was varied from 1 to 20. Performance of the method was evaluated by finding the root mean squared (RMS) of the difference between the predicted joint angles relative to the joint angles recorded from motion capture. The amount of data included in the creation of the probability density function was varied from 1 to 10 subjects, creating sets of for subjects included and excluded from the density function. The performance of the GP method for subjects included and excluded from the density function was evaluated to test the robustness of the method. Accuracy of the GP method varied with amount of incremental division of the workspace, increasing the number of increments decreased the RMS error of the method, with the error of average RMS error of included subjects ranging from 7.7° to 3.7°. However increasing the number of increments also decreased the robustness of the method.

Effects of the Genium Microprocessor Knee System on Knee Moment Symmetry During Hill Walking

Use of the Genium microprocessor knee (MPK) system reportedly improves knee kinematics during walking and other functional tasks compared to other MPK systems. This improved kinematic pattern was observed when walking on different hill conditions and at different speeds. Given the improved kinematics associated with hill walking while using the Genium, a similar improvement in the symmetry of knee kinetics is also feasible. The purpose of this study was to determine if Genium MPK use would reduce the degree of asymmetry (DoA) of peak stance knee flexion moment compared to the C-Leg MPK in transfemoral amputation (TFA) patients. This study used a randomized experimental crossover of TFA patients using Genium and C-Leg MPKs (n = 20). Biomechanical gait analysis by 3D motion tracking with floor mounted force plates of TFA patients ambulating at different speeds on 5° ramps was completed. Knee moment DoA was significantly different between MPK conditions in the slow and fast uphill as well as the slow and self-selected downhill conditions. In a sample of high-functioning TFA patients, Genium knee system accommodation and use improved knee moment symmetry in slow speed walking up and down a five degree ramp compared with C-Leg. Additionally, the Genium improved knee moment symmetry when walking downhill at comfortable speed. These results likely have application in other patients who could benefit from more consistent knee function, such as older patients and others who have slower walking speeds.

Golf hand prosthesis performance of transradial amputees

Background: Typical upper limb prostheses may limit sports participation; therefore, specialized terminal devices are often needed. The purpose of this study was to evaluate the ability of transradial amputees to play golf using a specialized terminal device. Case description and methods: Club head speed, X-factor, and elbow motion of two individuals with transradial amputations using an Eagle Golf terminal device were compared to a non-amputee during a golf swing. Measurements were collected pre/post training with various stances and grips. Findings and outcomes: Both prosthesis users preferred a right-handed stance initially; however, after training, one preferred a left-handed stance. The amputees had slower club head speeds and a lower X-factor compared to the non-amputee golfer, but increased their individual elbow motion on the prosthetic side after training. Conclusion: Amputees enjoyed using the device, and it may provide kinematic benefits indicated by the increase in elbow flexion on the prosthetic side. Clinical relevance The transradial amputees were able to swing a golf club with sufficient repetition, form, and velocity to play golf recreationally. Increased elbow flexion on the prosthetic side suggests a potential benefit from using the Eagle Golf terminal device. Participating in recreational sports can increase amputees’ health and quality of life.

DESIGN AND PERFORMANCE OF A PUSH-UP DEVICE FOR ABOVE-ELBOW AMPUTEES: A TECHNICAL NOTE

Accepted April 2, 2013. Address correspondence to Matthew Wernke, BSBME, Center for Assistive, Rehabilitation, and Robotics Technologies, University of South Florida, 4202 E. Fowler Ave, ENB 118, Tampa, FL 33620, USA. Tel: +1-813-974-9651; Fax: +1-813-974-3539; E-mail: mwernke@mail.usf.edu Technology and Innovation, Vol. 15, pp. 297–300, 2014 1949-8241/14

Inverse kinematics of a bilateral robotic human upper body model based on motion analysis data

90.00 + .00 Printed in the USA. All rights reserved. DOI: http://dx.doi.org/10.3727/194982413X13844488878970 Copyright  2014 Cognizant Comm. Corp. E-ISSN 1949-825X www.cognizantcommunication.com

A SPRING-LOADED POLE DESIGN FOR CALIBRATION OF FORCE PLATFORMS

Accurately predicting the movements of the human upper body is an obstacle in simulating human movement. This paper describes the optimization and comparison of three inverse kinematic algorithms designed to predict the pose of a 25 degree of freedom robotic human upper body model (RHBM). Motion analysis data of 10 subjects performing 5 activities of daily living were used to evaluate the performance of each method. The first algorithm used a numerically optimized weighted-least-norm (WLN) solution. The second algorithm maximized the joint angle probability density, using the gradient projection method (GP). The third algorithm used a single layer artificial neural network (NN), trained by Levenberg-Marquart backpropagation using the motion analysis data. Error was evaluated using the root mean square of the difference between calculated and recorded joint angles. The robustness was then tested by progressively excluding subject data from the training set, re-training the algorithms, and evaluating the error for all subjects. The numerically optimized WLN solution showed the highest robustness, and the GP and NN solutions had greater accuracy for the data included in training and lower accuracy for the data excluded from training. The gradient projection method showed greater robustness than the artificial neural network, and has potential to be refined and combined with the weighted least norm solution to increase accuracy and robustness. Future work will investigate combined methods and the ability to predict motion of persons using prostheses.

Differences in Military Obstacle Course Performance Between Three Energy-Storing and Shock-Adapting Prosthetic Feet in High-Functioning Transtibial Amputees: A Double-Blind, Randomized Control Trial

Gait analysis is an important tool in the diagnosis of movement disorders as well as analysis of prosthetic design and function. 3D motion analysis systems frequently use a combination of motion capture cameras and force platforms (FP). Inverse dynamics can be applied to calculate various kinetic outcomes from the data these systems provide. In order for these outcomes to be accurate, it is essential these systems are calibrated properly in order to provide accurate raw data. This paper reports on a new spring-loaded pole used to determine and minimize the error in force and center of pressure (CoP) data. The spring-loaded pole consists of two short segments of polyvinylchloride (PVC), a universal joint, two springs, a rubber tip and a handle. This spring-loaded pole improves previous instrumented pole designs by replacing expensive force transducers with an inexpensive spring, allowing for a quick analysis of a systems performance and calibration.