Joseph B. Webster

Utilization of a lower extremity ambulatory feedback system to reduce gait asymmetry in transtibial amputation gait

The goal of our research is to augment gait rehabilitation for persons with gait asymmetry through a real-time feedback system that can be used independently by patients in the community. Our wireless, wearable, real-time gait asymmetry detection system called the lower extremity ambulatory feedback system (LEAFS) is a low-cost, in-shoe gait detection device that provides real-time auditory feedback based on the stance time symmetry ratio between the right and left limbs. This study evaluated the performance of the LEAFS in three study subjects with gait asymmetry secondary to unilateral transtibial amputation. Study subjects used the LEAFS for six 30-min training sessions under the supervision of a physical therapist. Two subjects demonstrated improved gait symmetry, with one subject reducing trunk sway by 85.5%, and the other subject reducing trunk sway by 16.0% and increasing symmetry ratio toward unity by 26.5%, as measured by a clinical motion analysis lab. The third subject did not demonstrate any objective improvements in gait symmetry or trunk sway. While testing with a larger number of subjects is necessary, this initial study using LEAFS with persons with transtibial amputations suggests that it can assist in improving gait symmetry in this population.

Perceptions and acceptance of osseointegration among individuals with lower limb amputations: A prospective survey study

Osseointegration is a new technique for prosthetic suspension in individuals with limb loss. The objective of this study was to determine perceptions and acceptance of osseointegration as a means of prosthetic suspension among individuals with lower limb amputations. A survey instrument was developed and administered to individuals 18 years or older with a lower limb amputation at or above the transtibial level. Of the 73 participants who completed the survey, 33% stated that they would consider undergoing the osseointegration procedure for prosthetic attachment. Anticipated improvements in prosthetic function, improved activity level, the security of the suspension system, improved walking ability, and ease of prosthetic attachment were cited as the top advantages to the procedure. Forty-two percent of the participants responded that they would not consider having the procedure. In this group, infection, potential activity limitations due to implant failure, long rehabilitation course, and risk of a broken bone in the residual limb were cited as the top concerns. Characteristics that significantly correlated with a participant considering osseointegration included living in a rural community, pain interfering with daily activity, and problems with the prosthesis falling off. Based on these findings, it seems that improvements in infection prevention, efficient rehabilitation strategies, and the prevention of implant failure will be important for increased acceptance of osseointegration procedures among individuals with lower limb amputations.

Bioelectric Analyses of an Osseointegrated Intelligent Implant Design System for Amputees

The projected number of American amputees is expected to rise to 3.6 million by 2050. Many of these individuals depend on artificial limbs to perform routine activities, but prosthetic suspensions using traditional socket technology can prove to be cumbersome and uncomfortable for a person with limb loss. Moreover, for those with high proximal amputations, limited residual limb length may prevent exoprosthesis attachment all together. Osseointegrated implant technology is a novel operative procedure which allows firm skeletal attachment between the host bone and an implant. Preliminary results in European amputees with osseointegrated implants have shown improved clinical outcomes by allowing direct transfer of loads to the bone-implant interface. Despite the apparent advantages of osseointegration over socket technology, the current rehabilitation procedures require long periods of restrictive load bearing prior which may be reduced with expedited skeletal attachment via electrical stimulation. The goal of the osseointegrated intelligent implant design (OIID) system is to make the implant part of an electrical system to accelerate skeletal attachment and help prevent periprosthetic infection. To determine optimal electrode size and placement, we initiated proof of concept with computational modeling of the electric fields and current densities that arise during electrical stimulation of amputee residual limbs. In order to provide insure patient safety, subjects with retrospective computed tomography scans were selected and three dimensional reconstructions were created using customized software programs to ensure anatomical accuracy (Seg3D and SCIRun) in an IRB and HIPAA approved study. These software packages supported the development of patient specific models and allowed for interactive manipulation of electrode position and size. Preliminary results indicate that electric fields and current densities can be generated at the implant interface to achieve the homogenous electric field distributions required to induce osteoblast migration, enhance skeletal fixation and may help prevent periprosthetic infections. Based on the electrode configurations experimented with in the model, an external two band configuration will be advocated in the future.

The Lower Extremity Ambulation Feedback System for Analysis of Gait Asymmetries: Preliminary Design and Validation Results

Asymmetric gait, commonly referred to as “limping,” is frequently seen in individuals with a variety of musculoskeletal and neurologic conditions. Asymmetric gait impacts the metabolic cost of ambulation and the development of osteoarthritis and also affects the cosmetic appearance of gait. This is especially true for individuals with lower limb amputations who ambulate with prosthetic limbs. The Lower Extremity Ambulation Feedback System (LEAFS) is a shoe-insert device that uses force sensors to evaluate asymmetries in gait and provide auditory feedback when an asymmetric gait threshold is reached. The aim of this study was to validate the ability of the LEAFS to accurately measure stance time and detect asymmetries in stance time. A prospective, consecutive case series study design was used. The study population consisted of individuals with lower limb amputations at the transtibial level. Data were collected simultaneously using both the LEAFS and a force plate and markers on the foot in a clinical motion analysis laboratory as subjects ambulated at their self-selected walking speed. The methods comparison approach of Bland and Altman was used to validate the measurement of stance time, and two-sample t-tests were used to validate the detection of asymmetry. The LEAFS determined the stance time with a bias error of −10.4 ± 37.2 ms, when compared with the clinical motion laboratory, and detected the same asymmetries in stance time for subjects with unilateral amputation (a shorter stance time on the limb with the prosthetic, when compared with the intact limb) as the clinical motion laboratory.

Effectiveness of resonance frequency in predicting orthopedic implant strength and stability in an in vitro osseointegration model

Developing noninvasive tools that determine implant attachment strength to bone and monitor implant stability over time will be important to optimize rehabilitation protocols following insertion of osseointegrated implants in patients with limb loss. While resonance frequency has been previously shown to correlate with implant stability in dental implants placed in the mandible and maxilla, this tool has not been evaluated with implants placed in the medullary canal of long bones. In an in vitro model used to simulate irregular medullary canal implant contact and osseointegration, a strong positive correlation was determined between resonance frequency implant stability quotient values and the force required for implant pushout. The force required for implant displacement also correlated to the distance from the point of fixation to the transducer at the proximal end of the implant (point of resonance frequency monitoring).

Characterization of step count accuracy of actigraph activity monitor in persons with lower limb amputation

Activity monitors can be used to objectively assess patient progress and to quantitatively measure the impact of new technologies on function. The purpose of this study was to characterize the accuracy of the step counter, GT1M, when worn on the waist and ankle location in persons using a prosthetic limb to ambulate. Potential subjects were given the opportunity to enroll while at their usual clinical prosthetic checkup. The subject population consisted of nine males (two transfemoral and seven transtibial amputations). Accuracy of GT1M was determined by measuring the percent difference between visually observed steps and the steps recorded by the GT1M. Statistical significance was achieved if the p value was ≤0.05. The accuracy of the GT1M when worn on the ankle (90.2% mean ± 16.3% SD) was greater than when worn on the waist (63.5% mean ± 39.2% SD) as determined with a paired t-test (p = 0.028). Linear regression demonstrated that inaccuracies of the GT1M highly correlated to use of a walking aid (r2=0.789, p = 0.001). Therefore, the GT1M demonstrated the highest accuracy when worn on the prosthetic ankle and when ambulating over level surfaces without the use of a walking aid (97.8% ± 4.0%). Percent accuracy was as low as 10% in a participant who did not meet these criteria. If planning to use GT1M to quantify walking in persons with lower limb amputation, validation of the GT1M on the subjects and walking terrain to be studied is recommended.

Prediction of Stance Time and Force Symmetries using Instrumented Shoe Insoles for Use in Rehabilitation and Weight-Bearing Regimens

Objective: Evaluate predictions of stance time symmetry and stance force symmetry from wireless bilateral instrumented shoe insoles designed for rehabilitation using smartphone applications to provide real-time feedback. Design: Cross-sectional study. Subjects: Five subjects with no known gait abnormalities. Methods: Subjects performed ten trials of three conditions: walking without a limp, limping on the right foot, and limping on the left foot, with data captured simultaneously with two force plates and the instrumented shoe insoles. Linear regression analyses were used to develop prediction equations and significance. Results: The regression between the instrumented shoe insole and the force plate resulted in R-squared values ranging from 0.952 to 0.998 for stance time symmetry using symmetry ratio, and from 0.936 to 0.994 for stance force symmetry using a cumulative loading measure for force. With peak and average loading measures, R-squared values were lower and more variable. Conclusion: Symmetry based on stance times or stance forces was highly predicted using the instrumented shoe insoles. Instrumented shoe insoles and real-time feedback on a smartphone could be used in the future for improving patient compliance with weight-bearing regimens or other time or force based symmetry analyses outside of the gait laboratory setting.

Incorporation of Core Competency Questions Into an Annual National Self-Assessment Examination for Residents in Physical Medicine and Rehabilitation: Results and Implications

To determine the performance and change over time when incorporating questions in the core competency domains of practice‐based learning and improvement (PBLI), systems‐based practice (SBP), and professionalism (PROF) into the national PM&R Self‐Assessment Examination for Residents (SAER).