BACKGROUND:Postoperative transfer metatarsalgia is a common complication after hallux valgus surgeries. Shortening of the first metatarsal is traditionally thought to be the primary cause of it. However, we speculate the abnormal loading pattern during gait is the real reason. This study is to determine specific differences in the loading patterns between reconstructive hallux valgus (HV) feet with and without postoperative transfer metatarsalgia, so as to find risky loading characteristics of this complication.METHODS:Thirty feet with postoperative transfer metatarsalgia were recruited as pain group, while another 30 postoperative feet without pain as controls. All participants were asked to walk barefoot at self-selected speed through a plantar force measuring plate (Rs-Scan Inc.) for three times. Certain plantar load variables were recorded or calculated, and their differences between two groups were compared.RESULTS:For pain group, the maximum plantar force and force time integral of the first metatarsal decrease significantly; the force time integral of the central rays (second plus third metatarsal) does not significantly differ with that in the controls, but their cumulative load percentage to the whole foot is higher. In pain group, the time point when central rays reached their peak force during the push-off is significantly later than that in controls. And the regional instant load percentage at this moment presented significantly higher for central rays, while significantly lower for the first metatarsal and the hallux compared to the controls.CONCLUSIONS:For hallux valgus feet with postoperative metatarsalgia, the load function of the first metatarsal is obviously impaired. But for central rays, indicative difference is not reflected in either peak or cumulative load during the gait cycle, but in the instant load distribution when central rays reach their peak load. So we can conclude that whether the remaining regions can adequately share certain load during walking, especially around the time metatarsalgia often occurs, plays an unnegligible role. So surgeons should pay more attention to reconstruct a foot where load can be evenly distributed.

The tarsal bones articulate with each other and demonstrate complicated kinematic characteristics. The in vivo motions of these tarsal joints during normal gait are still unclear. Seven healthy subjects were recruited and fourteen feet in total were tested in the current study. Three dimensional models of the tarsal bones were first created using CT scanning. Corresponding local 3D coordinate systems of each tarsal bone was subsequently established for 6DOF motion decompositions. The fluoroscopy system captured the lateral fluoroscopic images of the targeted tarsal region whilst the subject was walking. Seven key pose images during the stance phase were selected and 3D to 2D bone model registrations were performed on each image to determine joint positions. The 6DOF motions of each tarsal joint during gait were then obtained by connecting these positions together. The TNJ (talo-navicular joint) exhibited the largest ROMs (range of motion) on all rotational directions with 7.39±2.75°of dorsi/plantarflexion, 21.12±4.68°of inversion/eversion, and 16.11±4.44°of internal/external rotation. From heel strike to midstance, the TNJ, STJ (subtalar joint), and CCJ (calcaneao-cuboid joint) were associated with 5.97°, 5.04°, and 3.93°of dorsiflexion; 15.46°, 8.21°, and 5.82°of eversion; and 9.75°, 7.6°, and 4.99°of external rotation, respectively. Likewise, from midstance to heel off, the TNJ, STJ, and CCJ were associated with 6.39, 6.19°, and 4.47°of plantarflexion; 18.57°, 11.86°, and 6.32°of inversion and 13.95°, 9.66°, and 7.58°of internal rotation, respectively. In conclusion, among the tarsal joints, the TNJ exhibited the greatest rotational mobility. Synchronous and homodromous rotational motions were detected for TNJ, STJ, and CCJ during the stance phase.

OBJECTIVE:To explore the accurate in vivo kinematic changes in the ankle complex when wearing low- and high-heel shoes (LHS and HHS, respectively).MATERIALS AND METHODS:Twelve young women were tested unilaterally. Three-dimensional models of the tibia, talus, and calcaneus were first created based on CT scan results. The subjects walked at a self-controlled speed in barefoot, LHS (4cm), and HHS (10cm) conditions. A fluoroscopy system captured the lateral fluoroscopic images of the ankle complex. The images of seven key positions in the stance phase were selected, and 3D to 2D bone model registrations were performed to determine the joint positions. The mean of 6 degree of freedom (DOF) range of motions (ROM), joint positions, and angular displacements of the ankle complex during the gait were then obtained.RESULTS:For the talocrural joint, the rotational ROMs of the subjects either in LHS or HHS condition displayed no significant difference from those in barefoot condition. For the subtalar joint, all the rotational ROMs in the HHS condition and the internal/external rotations in the LHS condition significantly decreased compared with those in the barefoot condition. The talocrural joint was positioned significantly more plantarflexed, inverted, internally rotated, and posteriorly seated in all seven poses in HHS condition, compared with those in barefoot condition.CONCLUSION:HHS mainly affected the rotational motion of the ankle complex during walking. The talocrural joint position was abnormal, and the subtalar joint ROM decreased during the gait in HHS condition. Only a few kinematic changes occurred in LHS condition relative to the barefoot condition.

Hallux valgus (HV) deformity is closely correlated to the hypermobility of the first metatarsal-cuneiform joint, but adequate understanding of the three-dimentional (3D) mobility of this joint in normal or HV feet is lacking. This study was conducted to investigate the mobility of the first metatarsal-cuneiform joint in multiple planes during body weight-bearing conditions for both normal and HV patients.

The motion of the distal syndesmosis correlates highly with the instability, while an accurate kinematic description of the distal tibiofibular joint during normal gait has not previously been presented.

The electrical shock is the only useful method to terminate the ventricular fibrillation (VF). The low energy defibrillation research is very important. The relationship of the shock parameters and the defibrillation efficiency will be investigated in this study. The mechanism of electrical defibrillation is that most of the myocardium cells can be enforced to depolarize and enter to refractory period at the same time when electrical field of the shock interacts with myocardium. The change of trans-membrane potential depends on the trans-membrane current. The defibrillation voltage is only the method to produce the needed current. The voltage needed to defibrillation lies on the defibrillation impedance. Energy is the product of the voltage and current and more easily influenced by the impedance and the current distribution. The effects of pulse duration to defibrillation threshold need to be considered also. Generally, the change of trans-membrane potential to reach the depolarization ΔEm is constant. Then I × τ (pulse duration) is a constant too. So cell's depolarization depends on the quantities of charge (the product of current and time) injected to the cell. Totally 7 domestic swine had been used for animal trails and more than 300 times VF had been induced. Defibrillation threshold is the lowest dosage of the shock for successful defibrillation. The animal trails show that the charge threshold varies little when the pulse duration is short but it will increase quickly at an certain pulse duration. We think that electric charge Q is the main parameter to determine the defibrillation result. The energy threshold is diverse because it maybe influenced by many reasons. So the energy threshold can be used to evaluate the ways and means of defibrillation, but not suitable to be used as the defibrillation dosage. © 2013 Springer-Verlag.

In order to fulfill the design requirements of motor evoked potential (MEP) stimulator in intraoperative neurophysiological monitoring (IONM) system, a kind of constant voltage pulse (CVP) stimulator has been designed. Two Flyback switching power supply (FSPS) circuits based on UC3845 provide the needed voltages. A transistor control circuit ensures that the voltage output is constant. An IGBT works as control switch to release pulses. The input and the output of the stimulator are physically isolated. Experimental results indicate that the stimulator has satisfied the design requirements. The parameters of output pulse are high-precision, rapid-response and wide-range with plenty options. When all setups are complete, the stimulator can release pulse within less than 100ms. The pulse highest amplitude is 900V. All parameters' relative errors are less than ±10%. The pulse rise time and fall time are less than 0.4μs. The stimulator can be also employed in other operations and be modified for constant current stimulation.

临床动物电击除颤实验无法精确测量放电电场在心脏上的实际分布情况,且存在诸多不便利和不安全因素。鉴于此,提出了一种基于心脏建模及有限元求解的心脏除颤电场分布仿真研究方法,心脏模型包含了完整的心房心室解剖结构和左右心腔,考虑了心肌细胞和血液的电阻率,然后采用有限元方法进行分析,并使用Abaqus集成环境进行求解,求解结果与文献报道的参考标准进行对比。仿真结果在除颤电压阈值和能量阈值方面与目前的植入式心脏复律除颤器（ICD）的临床应用效果具有相当的吻合度,能量阈值相对误差仅为10%,验证了所提出方法的可行性。

In order to make the actual defibrillation energy approximate to target defibrillation energy in automated external defibrillator, an energy compensation method is proposed in this paper. The transthoracic impedance is measured first, and then the charging voltage of energy storage capacitor is determined based on this impedance and target defibrillation energy. The system includes three parts, stimulation module, detection module and determination module. The system has been tested by standard resistor and animal experiments. The standard resistor experiments confirm that the system can work well, while the animal experiments validate the accuracy of the transthoracic impedance measurement and the effect of energy compensation. The effect of energy compensation based on our transthoracic impedance measurement is remarkable.