ABSTRACT
BACKGROUND:During the percutaneous vertebroplasty, the optimal dose of bone cement that can bring favorable cement dispersion and remodel the biomechanical balance of the fractured vertebrae remains controversial. OBJECTIVE:To investigate the dispersion degree of small dose of bone cement in vertebroplasty. METHODS: In this experiment, 18 sheep selected with the same condition were randomly divided into three groups (group A, group B, group C), 6 in each group. A model of thoracolumbar vertebral compression fracture (T12, L1, L2) was made in each sheep. The injected volume of bone cement in groups A, B, C was 15％, 20％, 25％ of the average volume of adjacent vertebral bodies, respectively. Postoperative CT images were used to evaluate the bone cement dispersion. Dispersion degree of bone cement among the three groups was compared by the Kruskal-Wallis test. RESULTS AND CONCLUSION:There was no statistical difference in the dispersion degree of bone cement among the three groups, and the excellent and good rate of dispersion was over 80％. To conclude, the optimal dose of bone cement injected into the fractured vertebra is 15％ of the average volume of adjacent vertebral bodies, which can achieve good dispersion degree and restore the biomechanical stability of the vertebral body.
ABSTRACT
Objective To simulate the supination-external rotation ankle injury and establish a 3D finite element model of the ankle. Methods Based on CT images of the normal human ankle joint, the 3D model of the ankle with ligaments was established. The supination-external rotation ankle injuries with four different degrees of Lauge-Hanson were analyzed by finite element method. Distributions of the ankle joint stress and tibial articular surface pressure were obtained. Results The maximum stress was at the anterior tibiofibular ligament attachment point of the tibial under supination-external rotation loading. When the anterior tibiofibular ligament was ruptured, the maximum stress was at the interosseous membrane. After the interosseous membrane was ruptured, the high stress was at the posterior ligament of the ankle. When the posterior tibiofibular ligament was ruptured, the high stress was at the deltoid ligament. The high pressure was at the distal fibula or the rear of tibial articular surface. Conclusions The established ankle-foot 3D numerical model can be used for the mechanical analysis of supination-externalrotation ankle injury. The calculated distributions of the ankle stress and the tibial articular surface pressure were in agreement with the description of Lauge-Hanson classification.
ABSTRACT
<p><b>BACKGROUND</b>The mortality and disability associated with progressing ischemic stroke are much higher than general ischemic stroke. This study was conducted to determine the risk factors for progressing ischemic stroke in the Han population of northeast China.</p><p><b>METHODS</b>A total of 2511 patients with ischemic stroke within 24 hours admitted to Department of Neurology, First Affiliated Hospital of Harbin Medical University were studied, from November 2007 to May 2009. All of the patients were classified into the progressing or non-progressing group according to the scores of the Scandinavian Neurological Stroke Scale. Fifteen putative risk factors were evaluated. The influence of risk factors for progressing ischemic stroke was analyzed with the simple Logistic analysis, the multiple Logistic analysis, and the stepwise Logistic regression model. All the statistical analysis was performed by SAS 9.1.</p><p><b>RESULTS</b>Totally 359 (14.3%) patients met the criteria for progressing ischemic stroke. The Logistic analysis showed that age, family stroke history, smoking history, hypertension on admission, a drop in blood pressure after admission to the hospital, high serum glucose on admission, and fever were related to progressing ischemic stroke in the Han population of northeast China.</p><p><b>CONCLUSION</b>People of the ischemic stroke with these factors are more likely to develop progressing ischemic stroke.</p>