Intrepid Dynamic Exoskeletal Orthosis Research Articles

Biomechanical response to ankle–foot orthosis stiffness during running

BackgroundThe Intrepid Dynamic Exoskeletal Orthosis (IDEO) is an ankle–foot orthosis developed to address the high rates of delayed amputation in the military. Its use has enabled many wounded Service Members to run again. During running, stiffness is thought to influence an orthosis' energy storage and return mechanical properties. This study examined the effect of orthosis stiffness on running biomechanics in patients with lower limb impairments who had undergone unilateral limb salvage. MethodsTen patients with lower limb impairments underwent gait analysis at a self-selected running velocity. 1. Nominal (clinically-prescribed), 2. Stiff (20% stiffer than nominal), and 3. Compliant (20% less stiff than nominal) ankle–foot orthosis stiffnesses were tested. FindingsAnkle joint stiffness was greatest in the stiffest strut and lowest in the compliant strut, however ankle mechanical work remained unchanged. Speed, stride length, cycle time, joint angles, moments, powers, and ground reaction forces were not significantly different among stiffness conditions. Ankle joint kinematics and ankle, knee and hip kinetics were different between limbs. Ankle power, in particular, was lower in the injured limb. InterpretationAnkle–foot orthosis stiffness affected ankle joint stiffness but did not influence other biomechanical parameters of running in individuals with unilateral limb salvage. Foot strike asymmetries may have influenced the kinetics of running. Therefore, a range of stiffness may be clinically appropriate when prescribing ankle–foot orthoses for active individuals with limb salvage.

How does ankle-foot orthosis stiffness affect gait in patients with lower limb salvage?

Ankle-foot orthoses (AFOs) are commonly prescribed during rehabilitation after limb salvage. AFO stiffness is selected to help mitigate gait deficiencies. A new custom dynamic AFO, the Intrepid Dynamic Exoskeletal Orthosis (IDEO), is available to injured service members but prescription guidelines are limited. In this study we ask (1) does dynamic AFO stiffness affect gait parameters such as joint angles, moments, and powers; and (2) can a given dynamic AFO stiffness normalize gait mechanics to noninjured control subjects? Thirteen patients with lower limb salvage (ankle arthrodesis, neuropathy, foot/ankle reconstruction, etc) after major lower extremity trauma and 13 control subjects who had no lower extremity trauma and wore no orthosis underwent gait analysis at a standardized speed. Patients wore their custom IDEO with posterior struts of three different stiffnesses: nominal (clinically prescribed stiffness), compliant (20% less stiff), and stiff (20% stiffer). Joint angles, moments, powers, and ground reaction forces were compared across the varying stiffnesses of the orthoses tested and between the patient and control groups. An increase in AFO compliance resulted in 20% to 26% less knee flexion relative to the nominal (p = 0.003) and stiff (p = 0.001) conditions, respectively. Ankle range of motion and power generation were, on average, 56% (p < 0.001) and 63% (p < 0.001), respectively, less than controls as a result of the relatively fixed ankle position. Patients with limb salvage readily adapted to different dynamic AFO stiffnesses and demonstrated few biomechanical differences among conditions during walking. None of the stiffness conditions normalized gait to controls. The general lack of differences across a 40% range of strut stiffness suggests that orthotists do not need to invest large amounts of time identifying optimal device stiffness for patients who use dynamic AFOs for low-impact activities such as walking. However, choosing a stiffer strut may more readily translate to higher-impact activities and offer less chance of mechanical failure.

Can an integrated orthotic and rehabilitation program decrease pain and improve function after lower extremity trauma?

Patients with severe lower extremity trauma have significant disability 2 years after injury that worsens by 7 years. Up to 15% seek late amputation. Recently, an energy-storing orthosis demonstrated improved function compared with standard orthoses; however, the effect when integrated with rehabilitation over time is unknown. (1) Does an 8-week integrated orthotic and rehabilitation initiative improve physical performance, pain, and outcomes in patients with lower extremity functional deficits or pain? (2) Is the magnitude of recovery different if enrolled more than 2 years after their injury versus earlier? (3) Does participation decrease the number considering late amputation? We prospectively evaluated 84 service members (53 less than and 31 > 2 years after injury) who enrolled in the initiative. Fifty-eight sustained fractures, 53 sustained nerve injuries with weakness, and six had arthritis (there was some overlap in the patients with fractures and nerve injuries, which resulted in a total of > 84). They completed 4 weeks of physical therapy without the orthosis followed by 4 weeks with it. Testing was conducted at Weeks 0, 4, and 8. Validated physical performance tests and patient-reported outcome surveys were used as well as questions pertaining to whether patients were considering an amputation. By 8 weeks, patients improved in all physical performance measures and all relevant patient-reported outcomes. Patients less than and greater than 2 years after injury improved similarly. Forty-one of 50 patients initially considering amputation favored limb salvage at the end of 8 weeks. We found this integrated orthotic and rehabilitation initiative improved physical performance, pain, and patient-reported outcomes in patients with severe, traumatic lower extremity deficits and that these improvements were sustained for > 2 years after injury. Efforts are underway to determine whether the Return to Run clinical pathway with the Intrepid Dynamic Exoskeletal Orthosis (IDEO) can be successfully implemented at additional military centers in patients > 2 years from injury while sustaining similar improvements in patient outcomes. The ability to translate this integrated orthotic and rehabilitation program into the civilian setting is unknown and warrants further investigation.

Return to Duty After Integrated Orthotic and Rehabilitation Initiative

To determine the return to active duty rate of military service members undergoing lower extremity limb salvage while using a novel custom orthosis and specialized rehabilitation compared with those receiving a novel custom orthosis alone. Retrospective cohort study. Military level I trauma center and tertiary referral center for limb salvage. All active duty service members enrolled in our institution's Return to Run Clinical Pathway were analyzed retrospectively. Service members were enrolled if they sustained injuries with residual disability below the knee. Injuries typically involved substantial motor and/or nerve deficit, and the overwhelming majority was secondary to high-energy injuries. Service members were fitted with a customized orthosis, an Intrepid Dynamic Exoskeletal Orthosis (IDEO), for use during rehabilitation. Service members were divided into 2 groups: those who had participated in the Return to Run Clinical Pathway with an IDEO (group 1) and those who only were fitted with an IDEO only (group 2). Return to military active duty rate. One hundred forty-six service members met the inclusion criteria. Group 1 consisted of 115 service members and group 2 consisted of 31 service members. Of those in group 1, 59 (51.3%) returned to active duty compared with 4 (12.9%) in group 2 (P = 0.0001). Mechanisms of injury were significant factors for return to duty (RTD), and those sustaining explosive mechanisms of injury or gunshot wounds had significantly lower RTD rates across both groups. Active duty service members participating in an integrated orthotic and rehabilitation initiative after a lower extremity injury have a higher rate of RTD than previous reports, and it is significantly higher than the orthotic device alone.

Deployment after limb salvage for high-energy lower-extremity trauma

Many wounded warriors experienced high-energy lower-extremity trauma (HELET) that may be limb threatening. Volumetric muscle loss, posttraumatic osteoarthritis, nerve injuries, and pain may severely limit physical function. Several wounded warriors express a strong desire to return to their units and be deployed in their original military occupational specialty. We began the return-to-run (RTR) clinical pathway at our institution 2 years ago to facilitate high-performance goals such as these. It involves an energy storing ankle foot orthosis, the intrepid dynamic exoskeletal orthosis in combination with high-intensity, progression-oriented rehabilitation. We sought to determine the rate of deployment or predeployment training after participation in this noninvasive intervention. A retrospective analysis of the RTR database was performed to determine the rate of deployment or predeployment training among those service members who began participation in the RTR between November of 2009 and March of 2011. Medical records were reviewed for demographics, injury, surgical data, and major complications. Requests for delayed amputation were recorded, and charts were reviewed to determine if patients eventually elected to proceed with amputation or if they chose to continue with limb salvage. Between November 2009 and March 2011, 87 service members completed the RTR. Of these, 17 (19.5%) have been deployed to combat or are in predeployment training. Sixteen serve in combat arms (nine Special Forces, four infantry/ranger, two combat engineers, and one gunner), and one is a member of the military intelligence community. Fifteen patients sustained their injuries as a result of HELET (four gunshot, five motor vehicle collisions, four explosions, one parachute injury, and one fall from height), one had idiopathic avascular necrosis of the talus, and one had an iatrogenic nerve injury after pelvic surgery. Six of the patients underwent circular external fixation, five received joint fusions (three ankle, two subtalar joint), and nine had major nerve injuries. Four initially desired amputation of their injured limb but have subsequently countermanded their request. Returning to high-level physical function after HELET is challenging. After implementation of the RTR clinical pathway with the intrepid dynamic exoskeletal orthosis, 19.5% of wounded warriors treated with the RTR have been deployed or will be deployed in the coming year.

Comparative Effect of Orthosis Design on Functional Performance

High-energy extremity trauma is common in combat. Orthotic options for patients whose lower extremities have been salvaged are limited. A custom energy-storing ankle-foot orthosis, the Intrepid Dynamic Exoskeletal Orthosis (IDEO), was created and used with high-intensity rehabilitation as part of the Return to Run clinical pathway. We hypothesized that the IDEO would improve functional performance compared with a non-custom carbon fiber orthosis (BlueRocker), a posterior leaf spring orthosis, and no brace. Eighteen subjects with unilateral dorsiflexion and/or plantar flexion weakness were evaluated with six functional tests while they were wearing the IDEO, BlueRocker, posterior leaf spring, or no brace. The brace order was randomized, and five trials were completed for each of the functional measures, which included a four-square step test, a sit-to-stand five times test, tests of self-selected walking velocity over level and rocky terrain, and a timed stair ascent. They also completed one trial of a forty-yard (37-m) dash, filled out a satisfaction questionnaire, and indicated whether they had ever considered an amputation and, if so, whether they still intended to proceed with it. Performance was significantly better with the IDEO with respect to all functional measures compared with all other bracing conditions (p < 0.004), with the exception of the sit-to-stand five times test, in which there was a significant improvement only as compared with the BlueRocker (p = 0.014). The forty-yard dash improved by approximately 35% over the values for the posterior leaf spring and no-brace conditions, and by 28% over the BlueRocker. The BlueRocker demonstrated a significant improvement in the forty-yard dash compared with no brace (p = 0.033), and a significant improvement in self-selected walking velocity on level terrain compared with no brace and the posterior leaf spring orthosis (p < 0.028). However, no significant difference was found among the posterior leaf spring, BlueRocker, and no-brace conditions with respect to any other functional measure. Thirteen patients initially considered amputation, but after completion of the clinical pathway, eight desired limb salvage, two were undecided, and three still desired amputation. Use of the IDEO significantly improves performance on validated tests of agility, power, and speed. The majority of subjects initially considering amputation favored limb salvage after this noninvasive intervention.