Time-varying and speed-matched model for the evaluation of stroke-induced changes in ankle mechanics.

The ankle mechanics (stiffness and moment) are modulated continuously when interacting with the environment during human walking. However, it remains unclear how ankle mechanics vary with walking speeds, and how they are affected by stroke. This study aimed to determine time-varying ankle stiffness and moment in stroke participants during walking, comparing them with healthy participants at matched speeds. A motion capture system, surface electromyography (EMG) system and force plates were used to measure biomechanics of seven healthy participants walking at 5 controlled speeds and ten patients with stroke at self-selected speeds. The ankle moment and stiffness during the stance phase were calculated using an EMG-driven musculoskeletal model. Surface equations of ankle moment and stiffness in healthy participants, with walking speed and stance phase as variables, were proposed based on polynomial fitting. Results showed that as walking speed increased, there was an increase in the ankle stiffness and moment of healthy participants during 77 %-89 % and 63 %-91 % of stance phase, respectively. Patients with stroke had lower ankle stiffness and moment at self-selected walking speed than healthy participants at 1.04 m/s walking speed during 52 %-87 % and 52 %-91 % of stance phase, respectively. At matched walking speed, the peak values of ankle stiffness and moment in patients with stroke were significantly less than those in healthy participants (p = 0.007; p = 0.028, respectively). This study proposes a novel approach to evaluate the ankle mechanics of patients with stroke using the speed-matched model of healthy participants and may provide insights into understanding speed-dependent movement mechanisms of human walking.

How Compliance of Surfaces Affects Ankle Moment and Stiffness Regulation During Walking.

Humans can regulate ankle moment and stiffness to cope with various surfaces during walking, while the effect of surfaces compliance on ankle moment and stiffness regulations remains unclear. In order to find the underlying mechanism, ten healthy subjects were recruited to walk across surfaces with different levels of compliance. Electromyography (EMG), ground reaction forces (GRFs), and three-dimensional reflective marker trajectories were recorded synchronously. Ankle moment and stiffness were estimated using an EMG-driven musculoskeletal model. Our results showed that the compliance of surfaces can affect both ankle moment and stiffness regulations during walking. When the compliance of surfaces increased, the ankle moment increased to prevent lower limb collapse and the ankle stiffness increased to maintain stability during the mid-stance phase of gait. Our work improved the understanding of gait biomechanics and might be instructive to sports surface design and passive multibody model development.

Intramuscular hematoma in rhabdomyolysis patients treated with low-molecular-weight heparin: Report of two cases.

BACKGROUND: Rhabdomyolysis is a serious complication of heat stroke. Unlike that in acute kidney injury, the risk of muscle bleeding in rhabdomyolysis is often ignored and can substantially increase via the widespread use of anticoagulants, leading to the formation of intramuscular hematoma. CASE SUMMARY: During the summer, a middle-aged man and an elderly man were diagnosed with heat stroke, rhabdomyolysis, and acute renal impairment. Low-dose enoxaparin sodium was initiated for prophylaxis of deep vein thrombosis after the disease was stabilized with continuous renal replacement therapy. After that, the patients' hemoglobin decreased progressively, and no obvious intracranial, thoracic, digestive, or skin bleeding tendency was found. However, one of the patients had hip muscle pain, and computed tomography and color ultrasound confirmed that the patients separately had lumbar back and hip intermuscular hematoma. After discontinuation of anticoagulant drugs and monitoring of the steady increase in hemoglobin, the intermuscular hematomas were gradually absorbed. Following the use of prophylactic anticoagulation therapy, the patients' hemoglobin showed a progressive downward trend. Hematoma formation in the lumbosacral and buttock muscles was confirmed after excluding bleeding in typical regions (such as the digestive tract, thoracic cavity, and abdominal cavity). Anticoagulant drugs were discontinued immediately, and nutritional support was increased. Subsequently, the hemoglobin levels gradually increased, and the hematoma volumes gradually decreased. CONCLUSION: Patients with rhabdomyolysis have a risk of muscle bleeding, and inappropriate use of anticoagulants may lead to an increased risk or even to the formation of an intermuscular hematoma. When continuous blood loss is found in the body, the possibility of bleeding in the muscles and more typical sites should be considered.