Alison L. Pruziner

Performance of conventional and X2® prosthetic knees during slope descent

BACKGROUND Individuals with transfemoral amputation often have difficulty descending sloped surfaces due to increased lower extremity range of motion and torque requirements. The X2®, a new microprocessor-controlled prosthetic knee, claims to improve gait over sloped terrain. The aim of this study was to evaluate how experienced prosthesis users descended a sloped surface using the X2®, compared to a conventional knee, either mechanical (MECH) or microprocessor (MP). METHODS Descent technique and biomechanics were assessed in 21 service members with unilateral transfemoral amputation as they descended an instrumented 10° slope at a self-selected walking velocity. FINDINGS Use of the X2® in the MECH group resulted in greater hill assessment scores (8.5 to 11.0, P=0.026), due primarily to decreased reliance on handrail use. The use of the X2® in the MP group increased prosthetic knee flexion to a median of 6.4° at initial contact (P=0.002) and 73.7° in swing (P=0.005), contributing to longer prosthetic limb steps (P=0.024) and increased self-selected velocity (P=0.041). Additionally, the use of the X2® in the MP group increased prosthetic limb impact peaks (11.6N/kg, P=0.004), improving impact peak symmetry to -1.3% (P=0.004). INTERPRETATION Decreased reliance on handrail use as MECH users descended in the X2® indicate improved function and perhaps greater confidence in the device. Additional biomechanical improvements for existing MP users suggest potential longer-term benefits with regard to intact limb health and overuse injuries.

Medial knee joint contact force in the intact limb during walking in recently ambulatory service members with unilateral limb loss: a cross-sectional study

Background Individuals with unilateral lower limb amputation have a high risk of developing knee osteoarthritis (OA) in their intact limb as they age. This risk may be related to joint loading experienced earlier in life. We hypothesized that loading during walking would be greater in the intact limb of young US military service members with limb loss than in controls with no limb loss. Methods Cross-sectional instrumented gait analysis at self-selected walking speeds with a limb loss group (N = 10, age 27 ± 5 years, 170 ± 36 days since last surgery) including five service members with transtibial limb loss and five with transfemoral limb loss, all walking independently with their first prosthesis for approximately two months. Controls (N = 10, age 30 ± 4 years) were service members with no overt demographical risk factors for knee OA. 3D inverse dynamics modeling was performed to calculate joint moments and medial knee joint contact forces (JCF) were calculated using a reduction-based musculoskeletal modeling method and expressed relative to body weight (BW). Results Peak JCF and maximum JCF loading rate were significantly greater in limb loss (184% BW, 2,469% BW/s) vs. controls (157% BW, 1,985% BW/s), with large effect sizes. Results were robust to probabilistic perturbations to the knee model parameters. Discussion Assuming these data are reflective of joint loading experienced in daily life, they support a “mechanical overloading” hypothesis for the risk of developing knee OA in the intact limb of limb loss subjects. Examination of the evolution of gait mechanics, joint loading, and joint health over time, as well as interventions to reduce load or strengthen the ability of the joint to withstand loads, is warranted.

A comparison of kinematic-based gait event detection methods in a self-paced treadmill application

Kinematic-based algorithms for detecting gait events are efficient and useful in the absence of (reliable) kinetic data. However, the validity of these kinematic-based algorithms for self-paced treadmill walking is unknown, particularly given the influence of walking speed on such data. We quantified offsets in event detection of four foot kinematics-based algorithms (horizontal position, horizontal velocity, vertical velocity, and sagittal resultant velocity) relative to events determined by a threshold in vertical ground reaction force among seven uninjured individuals - and nine with unilateral transtibial amputation - walking on a self-paced treadmill. Across walking speeds from 0.48-1.64m/s (0.5-31.7% CV), offsets ranged from -7 to +3 frames (≈83.3ms) in heel strike, and -3 to +5 frames (≈66.6 ms) in toe off. Regardless of method, offsets in heel strike were not influenced (-0.010.61) by variability in walking speed. However, offsets in toe-off were positively correlated with variability in walking speed for the horizontal position (r=0.539; P<0.001) and velocity (r=0.463; P<0.001) algorithms, and negatively correlated (r=-0.317; P<0.001) for the vertical velocity algorithm; offsets from the sagittal resultant velocity algorithm, with thresholds adjusted for walking speed, were not strongly associated (r=0.126; P=0.27). Although relatively minimal offsets support the applicability of these algorithms to self-paced walking, for individuals with asymptomatic and pathological gait patterns, sagittal resultant velocity of the foot produces the most consistent event detection over the widest range of (and variability in) walking speeds.

Metabolic and body composition changes in first year following traumatic amputation.

Body composition and metabolism may change considerably after traumatic amputation because of muscle atrophy and an increase in adiposity. The purpose of this study was to quantify changes in weight, body composition, and metabolic rate during the first year following traumatic amputation in military servicemembers. Servicemembers without amputation were included for comparison. Participants were measured within the first 12 wk after amputation (baseline) and at 6, 9, and 12 mo after amputation. Muscle mass, fat mass, weight, and metabolic rate were measured at each time point. There was a significant increase in weight and body mass index in the unilateral group between baseline and all follow-up visits (p < 0.01). Over the 12 mo period, total fat mass and trunk fat mass increased in both unilateral and bilateral groups; however, these changes were not statistically significant over time. Muscle mass increased in both the unilateral and bilateral group despite percent of lean mass decreasing. No changes in resting metabolism or walking energy expenditure were observed in any group. The results of this study conclude that weight significantly increased because of an increase in both fat mass and muscle mass in the first year following unilateral and bilateral amputation.

Use of a Powered Versus a Passive Prosthetic System for a Person with Bilateral Amputations during Level-Ground Walking

ABSTRACT Persons who have had bilateral lower-limb amputations, especially transfemoral amputation, must use biomechanical compensations to ambulate. Compensations during gait produce abnormal loads on the body and may reduce efficiency. Recent prosthetic advances have attempted to mimic the lost musculature by adding power to knee and ankle systems. A patient with bilateral amputations (right transtibial, left transfemoral) was evaluated 10 months after injury. The patient initially presented wearing a passive prosthetic system and was then fit with a powered prosthetic system and allowed to acclimate for 1 month. Kinematic and kinetic data were collected while the patient walked overground wearing both systems. The patient showed greater symmetry of step length, decreased vertical ground reaction force, and increased limb transition work using the powered system. Biomechanical variables showed some improvements when using a powered prosthetic system, which may indicate increased mechanical efficiency and decreased lower-limb loading.

The Center for Rehabilitation Sciences Research: Advancing the Rehabilitative Care for Service Members With Complex Trauma

The Center for Rehabilitation Sciences Research (CRSR) was established to advance the rehabilitative care for service members with combat-related injuries, particularly those with orthopedic, cognitive, and neurological complications. The center supports comprehensive research projects to optimize treatment strategies and promote the successful return to duty and community reintegration of injured service members. The center also provides a unique platform for fostering innovative research and incorporating clinical/technical advances in the rehabilitative care for service members. CRSR is composed of four research focus areas: (1) identifying barriers to successful rehabilitation and reintegration, (2) improving pain management strategies to promote full participation in rehabilitation programs, (3) applying novel technologies to advance rehabilitation methods and enhance outcome assessments, and (4) transferring new technology to improve functional capacity, independence, and quality of life. Each of these research focus areas works synergistically to influence the quality of life for injured service members. The purpose of this overview is to highlight the clinical research efforts of CRSR, namely how this organization engages a broad group of interdisciplinary investigators from medicine, biology, engineering, anthropology, and physiology to help solve clinically relevant problems for our service members, veterans, and their families.

Use of Predictive Energy Expenditure Equations in Individuals with Lower Limb Loss at Seated Rest

BACKGROUND As a result of the global war on terrorism, there has been a significant increase in young service members with traumatic amputations. Few published data are available on metabolic requirements for young, active individuals after traumatic limb loss, especially lower limb loss. OBJECTIVE The purpose of this study was to determine which predictive energy equation best predicted resting energy expenditure (REE) in this population. METHODS One hundred service members, 50 with at least one traumatic lower limb loss and 50 without limb loss, completed this study. Mean (standard deviation [SD]) age, height, and weight were 27.3 years (±5.3), 178.5 cm (±7.7), 86.5 kg (±15.8) for those with limb loss; and 29.4 years (±5.8), 179.1 cm (±6.7), 85.9 kg (±12.6) for those without. REE was measured using the Oxycon Mobile metabolic system (CareFusion). Measured REE was compared with the following REE equations: Mifflin-St Joer, Harris Benedict, Owen, 25 kcal/kg, and 30 kcal/kg. RESULTS All equations tended to underestimate or overestimate REE for both groups (P<0.001); however, the 25 kcal/kg had a more even distribution of disagreement for individuals with limb loss and without (P=0.100 and P=0.308, respectively), with 52% within ±10%. CONCLUSIONS The 25 kcal/kg best predicts REE for young, active individuals with or without limb loss. Future studies may determine that more appropriate equations are most useful for different subgroups of this population.

The Bridging Advanced Developments for Exceptional Rehabilitation (BADER) consortium: Reaching in partnership for optimal orthopaedic rehabilitation outcomes

The Bridging Advanced Developments for Exceptional Rehabilitation (BADER) Consortium began in September 2011 as a cooperative agreement with the Department of Defense (DoD) Congressionally Directed Medical Research Programs Peer Reviewed Orthopaedic Research Program. A partnership was formed with DoD Military Treatment Facilities (MTFs), U.S. Department of Veterans Affairs (VA) Centers, the National Institutes of Health (NIH), academia, and industry to rapidly conduct innovative, high-impact, and sustainable clinically relevant research. The BADER Consortium has a unique research capacity-building focus that creates infrastructures and strategically connects and supports research teams to conduct multiteam research initiatives primarily led by MTF and VA investigators.BADER relies on strong partnerships with these agencies to strengthen and support orthopaedic rehabilitation research. Its focus is on the rapid forming and execution of projects focused on obtaining optimal functional outcomes for patients with limb loss and limb injuries. The Consortium is based on an NIH research capacity-building model that comprises essential research support components that are anchored by a set of BADER-funded and initiative-launching studies. Through a partnership with the DoD/VA Extremity Trauma and Amputation Center of Excellence, the BADER Consortiums research initiative-launching program has directly supported the identification and establishment of eight BADER-funded clinical studies. BADERs Clinical Research Core (CRC) staff, who are embedded within each of the MTFs, have supported an additional 37 non-BADER Consortium-funded projects. Additional key research support infrastructures that expedite the process for conducting multisite clinical trials include an omnibus Cooperative Research and Development Agreement and the NIH Clinical Trials Database. A 2015 Defense Health Board report highlighted the Consortiums vital role, stating the research capabilities of the DoD Advanced Rehabilitation Centers are significantly enhanced and facilitated by the BADER Consortium.

Virtual reality-based assessment and treatment interventions for the combat-injured service member

Summary form only given. This presentation will highlight clinical cases and empirical results from virtual reality (VR)-based rehabilitation programs at two military medical facilities. These programs utilize VR environments to detect and treat functional deficits often difficult to address with standard clinical methods. Injured service members seen at these facilities are often young and highly fit at the time of their injuries. Their injuries include single and multiple limb traumas such as amputation, burns, and limb salvage. Despite the severity of these injuries and associated co-morbidities, these individuals commonly set rehabilitation goals that include a return to competitive sports and/or military duty. Deficits described by these individuals, that can limit the achievement of these goals, can be difficult to detect and quantify with conventional clinical measures. Novel VR-based assessments, developed by our clinical research team, have helped identify functional deficits across multiple domains using ecologically-valid tasks. Further, VR-based treatment applications have been designed to address these deficits and progress patients toward their goals. In general, we have found that service members following traumatic brain injury, amputation, and severe limb trauma demonstrate significant increases in function with VR therapies. These VR interventions are based on well-established therapeutic techniques and can be used to promote functional interactions with challenging environments while maintaining full safeties and controls.