Christopher A. Rábago

Evaluation of a Powered Ankle-Foot Prosthetic System During Walking

OBJECTIVE To determine whether a powered ankle-foot prosthesis improves gait mechanics, physical performance, and user satisfaction after traumatic transtibial amputation. DESIGN Pre-post. SETTING Gait analysis laboratory. PARTICIPANTS Young individuals with traumatic transtibial amputation (n=11) and matched controls (n=11). INTERVENTIONS Wearing an energy-storing and -returning (ESR) foot and a powered ankle-foot prosthesis. MAIN OUTCOME MEASURES Gait mechanics, physical performance, and user satisfaction. RESULTS The powered prosthesis ankle range of motion (ROM) was significantly larger (∼30%) than that of the ESR limb. However, both devices demonstrated significantly less ankle ROM than the control and intact limbs. At preswing, the ESR limb generated approximately 40% less peak ankle power than control and intact limbs. In contrast, the powered prosthesis generated significantly greater peak ankle power than control (35%) and ESR (∼125%) limbs, resulting in the powered limb absorbing twice the peak knee power observed in the control and intact limbs. The powered prosthesis limb peak hip power generation was approximately 45% greater at preswing than that of the intact limb. Walking velocity increased with the powered prosthesis compared with the ESR limb and was greater than that of the control group. However, physical performance measures were not significantly different between ESR and powered conditions. User satisfaction scores indicated a preference for the powered prosthesis over the ESR limb. CONCLUSIONS Compensatory strategies during gait with the ESR and powered prosthetic devices were similar to those reported in the literature. However, the addition of ankle power and ROM by the powered prosthesis appeared to increase compensatory strategies at proximal joints.

Application of a mild traumatic brain injury rehabilitation program in a virtual realty environment: a case study.

BACKGROUND AND PURPOSE Mild traumatic brain injury (mTBI) can compromise reaction time, visual perception, memory, attention, balance, and gait. These deficits, especially if persistent, can restrict participation in daily activities and the resumption of personal and profession roles. The purpose of this case study is to describe an mTBI-specific clinical assessment and rehabilitation intervention administered in a virtual reality environment. CASE DESCRIPTION The case involved a 31-year-old male service member who had sustained an mTBI (concussion) during a recreational softball game 36 days prior to physical therapist evaluation. He had complaints of severe visual and physical motion intolerance. He demonstrated impaired static balance and was restricted from full military duty. INTERVENTIONS The assessment included measurements of postural and gait balance during cognitive, visual, and vestibular challenges within a Computer-Assisted Rehabilitation Environment. Phase 1 of the intervention consisted of clinical techniques (ie, optokinetic stimulation/habituation, visual/physical perturbations, and postural stability exercises) targeting specific impairments. Phase 2 training consisted of weapon handling and target recognition tasks to simulate the requirements of his military occupation. OUTCOMES At the conclusion of 6 treatments, the patient demonstrated significant increases in postural and gait balance with a near complete resolution of all postconcussion symptoms. He successfully returned to full duty and training for combat deployment. DISCUSSION Service members and civilians exhibit similar impairments, limitations, and restrictions following mTBI. A rehabilitation program delivered in a virtual-reality environment can be structured to manage complex mTBI symptoms through the integration of multiple treatment modalities specific to a patients personal and professional roles.

Does unilateral transtibial amputation lead to greater metabolic demand during walking

Previous literature reports greater metabolic demand of walking following transtibial amputation. However, most research focuses on relatively older, less active, and often dysvascular amputees. Servicemembers with traumatic amputation are typically young, fit, and highly active before and often following surgical amputation of their lower limb. This study compared the metabolic demand of walking in young, active individuals with traumatic unilateral transtibial amputation (TTA) and nondisabled controls. Heart rate (HR), rate of oxygen consumption, and rating of perceived exertion (RPE) were calculated as subjects walked at a self-selected velocity and at five standardized velocities based on leg length. The TTA group completed a Prosthetics Evaluation Questionnaire. Oxygen consumption (p = 0.89), net oxygen consumption (p = 0.32), and RPE (p = 0.14) did not differ between groups. Compared with controls, HR was greater in the TTA group and increased to a greater extent with velocity (p < 0.001). Overall, the TTA group rated their walking abilities as high (mean: 93% out of 100%). This is the first study to report equivalent metabolic demand between persons with amputation and controls walking at the same velocity. These results may reflect the physical fitness of the young servicemembers with traumatic amputations and may serve to guide outcome expectations in the future.

Reliability and minimum detectable change of temporal-spatial, kinematic, and dynamic stability measures during perturbed gait

Temporal-spatial, kinematic variability, and dynamic stability measures collected during perturbation-based assessment paradigms are often used to identify dysfunction associated with gait instability. However, it remains unclear which measures are most reliable for detecting and tracking responses to perturbations. This study systematically determined the between-session reliability and minimum detectable change values of temporal-spatial, kinematic variability, and dynamic stability measures during three types of perturbed gait. Twenty young healthy adults completed two identical testing sessions two weeks apart, comprised of an unperturbed and three perturbed (cognitive, physical, and visual) walking conditions in a virtual reality environment. Within each session, perturbation responses were compared to unperturbed walking using paired t-tests. Between-session reliability and minimum detectable change values were also calculated for each measure and condition. All temporal-spatial, kinematic variability and dynamic stability measures demonstrated fair to excellent between-session reliability. Minimal detectable change values, normalized to mean values ranged from 1–50%. Step width mean and variability measures demonstrated the greatest response to perturbations with excellent between-session reliability and low minimum detectable change values. Orbital stability measures demonstrated specificity to perturbation direction and sensitivity with excellent between-session reliability and low minimum detectable change values. We observed substantially greater between-session reliability and lower minimum detectable change values for local stability measures than previously described which may be the result of averaging across trials within a session and using velocity versus acceleration data for reconstruction of state spaces. Across all perturbation types, temporal-spatial, orbital and local measures were the most reliable measures with the lowest minimum detectable change values, supporting their use for tracking changes over multiple testing sessions. The between-session reliability and minimum detectable change values reported here provide an objective means for interpreting changes in temporal-spatial, kinematic variability, and dynamic stability measures during perturbed walking which may assist in identifying instability.

Use of Perturbation-Based Gait Training in a Virtual Environment to Address Mediolateral Instability in an Individual With Unilateral Transfemoral Amputation

Background and Purpose Roughly 50% of individuals with lower limb amputation report a fear of falling and fall at least once a year. Perturbation-based gait training and the use of virtual environments have been shown independently to be effective at improving walking stability in patient populations. An intervention was developed combining the strengths of the 2 paradigms utilizing continuous, walking surface angle oscillations within a virtual environment. This case report describes walking function and mediolateral stability outcomes of an individual with a unilateral transfemoral amputation following a novel perturbation-based gait training intervention in a virtual environment. Case Description The patient was a 43-year-old male veteran who underwent a right transfemoral amputation 7+ years previously as a result of a traumatic blast injury. He used a microprocessor-controlled knee and an energy storage and return foot. Outcomes Following the intervention, multiple measures indicated improved function and stability, including faster self-selected walking speed and reduced functional stepping time, mean step width, and step width variability. These changes were seen during normal level walking and mediolateral visual field or platform perturbations. In addition, benefits were retained at least 5 weeks after the final training session. Discussion The perturbation-based gait training program in the virtual environment resulted in the patients improved walking function and mediolateral stability. Although the patient had completed intensive rehabilitation following injury and was fully independent, the intervention still induced notable improvements to mediolateral stability. Thus, perturbation-based gait training in challenging simulated environments shows promise for improving walking stability and may be beneficial when integrated into a rehabilitation program.

Evaluation of a Powered Ankle-Foot Prosthesis during Slope Ascent Gait.

Passive prosthetic feet lack active plantarflexion and push-off power resulting in gait deviations and compensations by individuals with transtibial amputation (TTA) during slope ascent. We sought to determine the effect of active ankle plantarflexion and push-off power provided by a powered prosthetic ankle-foot (PWR) on lower extremity compensations in individuals with unilateral TTA as they walked up a slope. We hypothesized that increased ankle plantarflexion and push-off power would reduce compensations commonly observed with a passive, energy-storing-returning prosthetic ankle-foot (ESR). We compared the temporal spatial, kinematic, and kinetic measures of ten individuals with TTA (age: 30.2 ± 5.3 yrs) to matched abled-bodied (AB) individuals during 5° slope ascent. The TTA group walked with an ESR and separately with a PWR. The PWR produced significantly greater prosthetic ankle plantarflexion and push-off power generation compared to an ESR and more closely matched AB values. The PWR functioned similar to a passive ESR device when transitioning onto the prosthetic limb due to limited prosthetic dorsiflexion, which resulted in similar deviations and compensations. In contrast, when transitioning off the prosthetic limb, increased ankle plantarflexion and push-off power provided by the PWR contributed to decreased intact limb knee extensor power production, lessening demand on the intact limb knee.

The Extremity Trauma and Amputation Center of Excellence: Overview of the Research and Surveillance Division

Congress authorized creation of the Extremity Trauma and Amputation Center of Excellence (EACE) as part of the 2009 National Defense Authorization Act. The legislation mandated the Department of Defense (DoD) and Department of Veterans Affairs (VA) to implement a comprehensive plan and strategy for the mitigation, treatment, and rehabilitation of traumatic extremity injuries and amputation. The EACE also was tasked with conducting clinically relevant research, fostering collaborations, and building partnerships across multidisciplinary international, federal, and academic networks to optimize the quality of life of service members and veterans who have sustained extremity trauma or amputations. To fulfill the mandate to conduct research, the EACE developed a Research and Surveillance Division that complements and collaborates with outstanding DoD, VA, and academic research programs across the globe. The EACE researchers have efforts in four key research focus areas relevant to extremity trauma and amputation: (1) Novel Rehabilitation Interventions, (2) Advanced Prosthetic and Orthotic Technologies, (3) Epidemiology and Surveillance, and (4) Medical and Surgical Innovations. This overview describes the EACE efforts to innovate, discover, and translate knowledge gleaned from collaborative research partnerships into clinical practice and policy.

The influence of traumatic transfemoral amputation on metabolic cost across walking speeds

Background: Recent literature indicates equivalent costs of walking can be achieved after a transtibial amputation when the individual is young, active, and/or has extensive access to rehabilitative care. It is unknown if a similar cohort with transfemoral amputation can also achieve lower metabolic costs of walking than previously reported. Objective: Compare metabolic cost in individuals with a transfemoral amputation to controls and to the literature across a range of walking speeds. Study design: Cross-sectional. Methods: A total of 14 individuals with a unilateral transfemoral amputation (27 ± 5 years, N = 4 mechanical knee, N = 10 microprocessor knee) and 14 able-bodied controls (26 ± 6 years) walked at self-selected and four standardized speeds. Heart rate, metabolic rate (mL O2/kg/min), metabolic cost (mL O2/kg/m), and rating of perceived exertion were calculated. Results: Self-selected speed was 8.6% slower in the transfemoral amputation group (p = 0.031). Across standardized speeds, both metabolic rate and metabolic cost ranged from 44%–47% greater in the transfemoral amputation group (p < 0.001), heart rate was 24%–33% greater (p < 0.001), and perceived exertion was 24%–35% greater (p < 0.009). Conclusion: Although the transfemoral amputation group was relatively young, physically fit, and had extensive access to rehabilitative care, the metabolic cost of walking fell within the ranges of the literature on older or presumably less fit individuals with transfemoral amputation. Clinical relevance Developments in prosthetic technology and/or rehabilitative care may be warranted and may reduce the metabolic cost of walking in individuals with a transfemoral amputation.

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.

The Prevalence of Gait Deviations in Individuals With Transtibial Amputation

Individuals with a transtibial amputation (TTA) are at increased risk for developing secondary musculoskeletal disorders as a result of multiple gait deviations. These deviations are primarily characterized using group mean comparisons, which do not establish if deviations are prevalent, of large magnitude, or both. In contrast, use of normative reference ranges and prevalence specifically identifies the percentage of individuals outside of a predefined acceptable range. The purpose of this study was to identify and characterize gait deviations in service members with unilateral TTA using group mean comparisons and normative reference ranges (able-bodied mean ± 2 SD). Temporal spatial, kinematic, and kinetic data were collected during biomechanical gait assessments of 40 able-bodied males and 16 males with a TTA. Highly prevalent and statistically significant deviations were observed at the ankle and knee of the prosthetic limb and hip of the intact limb in the TTA group. Approximately 20% of measures that were significantly different between groups demonstrated 0% deviation prevalence. Deviations in the prosthetic limb were in agreement with literature, although most intact limb deviations were not. Further study is needed to determine the exact etiology of these deviations, and their association with the development of secondary musculoskeletal conditions.