Effects of Backpack Types on Kinematics and Plantar Pressure in College Students During Stairs Walking / 医用生物力学

Objective To analyze the influence of different backpack types and loads on kinematics and plantar pressure of college students during stair climbing, so as to provide references for choosing the appropriate backpack and carrying mode. Methods The Nokov infrared light point motion capture system and Podome plantar pressure system were used to analyze the differences in the range of motion ( ROM) of the trunk and lower limb joints, the kinematic parameters at the peak time, the peak pressure of each plantar partition, the contact time, the maximum pressure of the whole foot, the average pressure and the maximum contact area for 15 male college students during the support period of stair climbing. Results The 5% BW and 10% BW backpack loads reduced ROM of trunk rotation, increased ROM of ankle flexion/ extension and varus / valgus. The 10% BW backpack loads increased the peak pressure of the 1st and 3rd metatarsals bones and the maximum pressure of the whole foot ( P < 0. 05). Single-shoulder bag and handbag reduced ROM of trunk tilting and rotation, and increased ROM of ankle flexion and extension, hip flexion angle, peak pressure of foot arch and medial heel (P<0. 05). The double-shoulder bag loads increased peak pressure in the toe area (P<0. 05). Conclusions During walking on the stairs, the 5% BW and 10% BW backpack loads limited trunk rotation and increased ankle ROM. The 10% BW loads also increased the load in metatarsal area. The unilateral weight-bearing mode would make the trunk tilt to the unload side and rotate to the weight-bearing side. The pressure in toe area was higher when carrying double-shoulder bag, while single-shoulder bag and handbag mainly increased the pressure of arch foot and medial heel. It is suggested that college students choose symmetrical backpack scheme, and wisely allocate back weight to avoid the injury of foot area.

The Effect of Ankle Brace on Biomechanics of the Lower Extremity During Landing: A Systematic Review and Meta Analysis / 医用生物力学

Objective To examine the effects of ankle brace on biomechanics of the lower extremity during landing, so as to provide a theoretic support to choose ankle brace for people with different sports levels. Methods The key words (ankle brace OR ankle braces OR ankle bracing OR ankle support) AND (landing OR land OR jump OR hopped OR hopping) AND (biomechanics OR kinematics OR kinetics OR electromyography OR neuromuscular) in Chinese and English were searched from different electronic databases (CNKI, Web of Science, EBSCO, PubMed and other databases), for a period of Jan. 2000 to Dec. 2020. Cochrane was used to evaluate the quality of eligible studies. For meta analysis, subgroup analysis was used to assess the impact of ankle braces on ankle biomechanics.Results Thirteen studies with a total of 222 participants were included for mata analysis in this study. The semi-rigid ankle brace reduced the peak of ankle inversion by 25.8% compared with the elastic ankle brace (SMD=-0.562, P<0.001). Moreover, the elastic ankle brace reduced ankle plant flexion during landing among athletes (SMD=-3.42, P=-0.021). As for collagiate students, both elastic ankle and semi-rigid ankle decreased the ankle inversion (elastic ankle brace: 35.4%, SMD=-1.000, P=-0.013; semi-rigid ankle brace: 31.11%, SMD=-0.881, P<0.001) and ankle plant flexion (elastic ankle brace:23.30%, SMD=-1.381, P<0.001;semi-rigid ankle brace: 36.33%, SMD=-1.605, P<0.001).Conclusions Both ankle braces can prevent ankle sprain for athletes (basketball, volleyball, running) who experience training more than 5 years. The elastic ankle brace can limit the inversion and plantar flexion, while the semi-rigid ankle brace can merely decrease the ankle inversion. Therefore, athletes are more suitable for the elastic ankle brace. As for collegiate students without training history, both ankle brace can decrease the ankle inversion and plantar flexion. The elastic ankle brace has greater restriction on inversion, while the semi-rigid ankle brace has more restriction on plantar flexion. Therefore, the elastic ankle brace should be utilized if collegiate students have calcaneofibular ligament injury, while the semi-rigid ankle brace is more suitable for collegiate students who have a history of anterior talofibular ligament injury.

Effects of Gender and Maneuvers on ACL Injury Risk Factors for Volleyball Players / 医用生物力学

Objective To study the effect of gender and maneuvers on anterior cruciate ligament (ACL) injury risk factors for volleyball players. Methods Sports biomechanics data of volleyball players during stop-jump, drop landing and sidestep cutting were collected. The ACL injury rate and biomechanical parameters of simulated injured jumps were obtained with Monte Carlo simulation. The influence of gender and maneuvers on ACL injury risk factors was validated by 2×3 mixed designed two-way ANOVA. Results Sidestep cutting was the highest risk maneuver of ACL injury for both genders (P＜0.001). Compared with male players, female players had a greater risk of ACL injury during sidestep cutting and stop-jump (P＜0.001), while male players were more prone to have ACL injury than female players during drop landing (P＜0.001). The risk factors of ACL injury obtained by simulation were significantly influenced by gender and maneuvers (P＜0.001). Conclusions Male players were more likely to increase ACL load due to smaller knee flexion, forward leg tilt and heel landing than female players during sidestep cutting, while female players owned larger ground reaction force (GRF) and knee extension moment. Smaller knee flexion angle during stop jump was the major risk factor for both genders, however more characteristics contributed to the males. Female players with large GRF, knee valgus and extension moment, and heel-landing were likely to have ACL injury, while the small knee flexion angle was the key risk factor for male players. The results can provide evidences for evaluation of volleyball players’ ACL injury risk, individualized injury prevention protocols, and clinical treatment and rehabilitation directions.

Numerical Simulation for the Safe Retention Value of Residual Stromal Bed Thickness in Laser-Assisted in situ Keratomileusis / 医用生物力学

Objective To study the effects of different residual stromal bed thickness (RSBT) in laser-assisted in situ keratomileusis (LASIK) surgery on geometric deformation and stress changes of the cornea under different intraocular pressures (IOP), and evaluate safety of the three retention values (250, 280, 300 μm). Methods The models of normal cornea and corneas with different RSBT after surgery were established by the finite element software ABAQUS. Appropriate loading and boundary conditions were set and then the corresponding displacement and stress were calculated. Results The apical displacement of the postoperative cornea (RSBT=250 μm) under IOP=2.66 kPa was basically the same as that of the normal cornea (RSBT=550 μm) under IOP=5.32 kPa. RSBT=280 μm was in the low risk area of keratoconus, while RSBT=250 μm was in the high-risk area. At a value between 280 μm and 300 μm of RSBT, the stress distribution was nearly consistent with that of the normal cornea. With RSBT=300 μm, the stromal layer of the cornea lost 40% of the strongest strength against tissue tension. Conclusions RSBT=250 μm is the minimum retention value for LASIK surgery. RSBT=250 μm is the high risk value. With RSBT=330-340 μm, LASIK surgery is safe enough for most patients.

The Trans-Scale Conduction Behavior of Fluid Stimulation in Loaded Bone / 医用生物力学

Objective To investigate the conduction behavior of fluid flow induced by physiological loads at different scales of bone. Method sThe multiscale bone models were established by using the COMSOL Multiphysics software, and the fluid behaviors were investigated at macro-, meso- and micro-scale. Results At macro-meso scale，the distribution of pore pressure and fluid velocity of osteon near the periosteum and endoosteum were different from that in other parts. Due to the different structure and material parameters at different layers, the loading and fluid pressure caused different biomechanical responses in the process of transferring from macro-scale to micro-scale. Conclusions The multi-scale layered modeling of bone structure-osteon-lacunae-bone canaliculi was established, which provided the theoretical reference for deeper understanding of fluid stimulation and mechanotransduction.

Trends on the changing prevalence in patients with early syphilis and HIV infection among men who having sex with men in Nanjing, from 2008 to 2013 / 中华流行病学杂志

<p><b>OBJECTIVE</b>To observe the trends on prevalence of early syphilis and HIV infection among men who had sex with men in the last six years from a HIV/AIDS counseling and testing clinic in Nanjing, and to develop relative strategies.</p><p><b>METHODS</b>Men who have sex with men involved in AIDS/HIV and syphilis voluntary counseling and testing services were recruited and investigated from 2008 to 2013 in this clinic. Clients whose syphilis serologic test showed positive were determined the diagnosis by physician within the referral network from sexually transmitted diseases clinics. Demographic information on early syphilis, HIV infection or co-infection with HIV and early syphilis was described while related epidemic trend analysis was performed.</p><p><b>RESULTS</b>The annual numbers of men having sex with men under survey were 1 004 in 2008, 1 218 in 2009, 1 236 in 2010, 748 in 2011, 1 019 in 2012 and 1 420 in 2013. The prevalence rates of early syphilis appeared to be: 2.19% in 2008, 2.71% in 2009, 2.43% in 2010, 1.74% in 2011, 3.04% in 2012 and 2.32% in 2013, with the trend as: P > 0.05. The prevalence rates of HIV infection were 1.29% in 2008, 2.63% in 2009, 5.42% in 2010, 8.82% in 2011, 11.97% in 2012 and 10.42% in 2013, with trend as: P < 0.01. The prevalence rates of early syphilis with HIV infection increased from 0.20% in 2008 to 1.06% in 2013 (trend: P < 0.01). The proportion of HIV co-infection among men having sex with men with early syphilis infection, increased from 9.09% in 2008 to 45.45% in 2013, with trend: P < 0.01.</p><p><b>CONCLUSION</b>Early syphilis infection among men who having sex with men showed a stable trend but the number of HIV and co-infections with early syphilis and HIV increased rapidly in the last six years in Nanjing. Continued intervention strategies should target on men who have sex with men to slow down the epidemic of syphilis and HIV infection.</p>

Effect of Early Rehabilitation on Patients with Closed Traumatic Brain Injury / 中国康复理论与实践

@#ObjectiveTo observe the effect of early rehabilitation on patients with closed traumatic brain injury (TBI).Methods80 TBI patients were divided into rehabilitation group and control group with 40 cases in each group. The control group was treated with routine surgical and other treatments. The rehabilitation group was treated with limb exercise and daily living training, besides treatments mentioned above. The scores of degrees of neural damage, Fugl-Meyer Assessment (FMA), modified Barthel index (MBI) and disability rating scale, and complications within 3 months of two groups were compared.ResultsThe scores of degree of neural damage, FMA, MBI and disability rating scale, and rate of complication of the rehabilitation group were significantly different from that of the control group (P<0.05～0.01).ConclusionEarly rehabilitation can improve brain function and reduce complication incidence of TBI patients.