Publications by authors named "Marshall K Ishmael"

Article Synopsis
  • - The study investigates how a powered hip exoskeleton affects walking efficiency in individuals with above-knee amputations, hypothesizing that it reduces energy used by the residual limb.
  • - Eight participants walked on a treadmill with and without the exoskeleton, measuring various biomechanical factors, leading to a significant decrease in energy exerted by the residual hip.
  • - Results show that using the exoskeleton reduced the net energy and hip extension torque during walking, suggesting that this assistance improves walking economy by making movement easier for those with amputations.
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Most individuals suffering a stroke have permanent weakness on one side of the body (hemiparesis) that reduces their ability to ambulate. Autonomous powered exoskeletons have been proposed as a possible solution to this problem. Studies with healthy subjects show that assistive powered exoskeletons have the potential to improve gait, for example, by reducing the metabolic cost of walking.

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Above-knee amputation severely reduces the mobility and quality of life of millions of individuals. Walking with available leg prostheses is highly inefficient, and poor walking economy is a major problem limiting mobility. Here we show that an autonomous powered hip exoskeleton assisting the residual limb significantly improves metabolic walking economy by 15.

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Misalignments between powered exoskeleton joints and the user's anatomical joints are inevitable due to difficulty locating the anatomical joint axis, non-constant location of the anatomical joint axis, and soft-tissue deformations. Self-aligning mechanisms have been proposed to prevent spurious forces and torques on the user's limb due to misalignments. Several exoskeletons have been developed with self-aligning mechanisms based on theoretical models.

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Motion capture is necessary to quantify gait deviations in individuals with lower-limb amputations. However, access to the patient population and the necessary equipment is limited. Here we present the first open biomechanics dataset for 18 individuals with unilateral above-knee amputations walking at different speeds.

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In this paper, we explore the effect of residual hip assistance in one above-knee amputee subject using a novel lightweight powered hip exoskeleton. Differently from a powered prosthesis, a powered hip exoskeleton adds mass proximally. Thus, we expect that the negative effect of the added mass will be lower for a powered hip exoskeleton than a powered ankle and knee prosthesis.

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Background: Few studies on kinematics correlate patterns to functional outcomes after total knee arthroplasty (TKA). The purpose of this study was to determine if lateral pivot motion in early flexion and medial pivot in high flexion, simulating native knee kinematics, produces superior clinical outcomes. A second objective was to determine if specific kinematic patterns produce superior outcomes.

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Background: Many total knee arthroplasty (TKA) implants are designed to facilitate a medial pivot kinematic pattern. The purpose of this study was to determine whether intraoperative medial pivot kinematic patterns are associated with improved patient outcomes.

Methods: A retrospective review of consecutive primary TKAs was performed.

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Background: Current patient selection criteria and medical risk stratification methods for outpatient primary total joint arthroplasty (TJA) surgery are unproven. This study assessed the predictive ability of a medically based risk assessment score in selecting patients for outpatient and short stay surgery.

Methods: A retrospective review of 1120 consecutive primary TJAs in an early discharge program was performed.

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Background: Recent popularity of kinematic alignment and constitutional varus has caused some surgeons to leave varus limbs in residual varus after total knee arthroplasty (TKA). This study assessed whether if patients left in residual varus have improved outcomes compared with those fully corrected to neutral alignment.

Methods: A retrospective review of 361 consecutive primary TKAs was performed.

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