How Does Ankle-foot Orthosis Stiffness Affect Gait in Patients With Lower Limb Salvage?
BROOKE ARMY MEDICAL CENTER FORT SAM HOUSTON TX
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Background 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. Questionspurposes 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 Methods Thirteen patients with lower limb salvage ankle arthrodesis, neuropathy, footankle 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. Results 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. Conclusions 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.
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