Screw angulation affects bone-screw stresses and bone graft load sharing in anterior cervical corpectomy fusion with a rigid screw-plate construct: a finite element model study

Background contextAnterior corpectomy and reconstruction with bone graft and a rigid screw-plate construct is an established procedure for treatment of cervical neural compression. Despite its reliability in relieving symptoms, there is a high rate of construct failure, especially in multilevel cases.PurposeThere has been no study evaluating the biomechanical effects of screw angulation on construct stability; this study investigates the C4–C7 construct stability and load-sharing properties among varying screw angulations in a rigid plate-screw construct.Study designA finite element model of a two-level cervical corpectomy with static anterior cervical plate.MethodsA three-dimensional finite element (FE) model of an intact C3–T1 segment was developed and validated. From this intact model, a fusion model (two-level [C5, C6] anterior corpectomy) was developed and validated. After corpectomy, allograft interbody fusion with a rigid anterior screw-plate construct was created from C4 to C7. Five additional FE models were developed from the fusion model corresponding to five different combinations of screw angulations within the vertebral bodies (C4, C7): (0°, 0°), (5°, 5°), (10°, 10°), (15°, 15°), and (15°, 0°). The fifth fusion model was termed as a hybrid fusion model.ResultsThe stability of a two-level corpectomy reconstruction is not dependent on the position of the screws. Despite the locked screw-plate interface, some degree of load sharing is transmitted to the graft. The load seen by the graft and the shear stress at the bone-screw junction is dependent on the angle of the screws with respect to the end plate. Higher stresses are seen at more divergent angles, particularly at the lower level of the construct.ConclusionThis study suggests that screw divergence from the end plates not only increases load transmission to the graft but also predisposes the screws to higher shear forces after corpectomy reconstruction. In particular, the inferior screw demonstrated larger stress than the upper-level screws. In the proposed hybrid fusion model, lower stresses on the bone graft, end plates, and bone-screw interface were recorded, inferring lower construct failure (end-plate fractures and screw pullout) potential at the inferior construct end.     

儿童青少年睡眠时间与社交焦虑的关联

  目的  分析儿童青少年睡眠时间与社交焦虑的关联,为提倡儿童青少年保持健康的生活方式进而促进心理健康提供依据。  方法  于2020年在北京市采取整群随机抽样的方式招募1 145名7~16岁儿童青少年,对其进行一般身体测量和问卷调查,使用儿童社交焦虑量表和匹兹堡睡眠质量指数量表评价儿童青少年的社交焦虑症状和睡眠时间。使用t检验比较不同组社交焦虑得分的差异,使用多元线性回归模型分析睡眠时间与社交焦虑之间的关联。  结果  研究对象的社交焦虑平均得分为(5.47±4.18)分,女生、13~16岁、每日中高强度体力活动时间不足和睡眠时间不足的儿童青少年社交焦虑分数较高(t值分别为-4.34,-6.14,3.35,2.93,P值均 < 0.05)。多元线性回归模型结果显示,在调整相关的混杂因素后,总体的睡眠时间每增加1 h,社交焦虑分数降低0.78分(β=-0.78,95%CI=-1.03~-0.54,P < 0.01),男生和女生的社交焦虑分数分别降低0.60(95%CI=-0.95~-0.25)和0.90(95%CI=-1.24~-0.56)分,7~12和13~16岁儿童青少年的社交焦虑分数分别降低0.75(95%CI=-1.11~-0.40)和0.76分(95%CI=-1.11~-0.41),非超重肥胖和超重肥胖儿童分别降低0.78(95%CI=-1.09~-0.48)和0.81分(95%CI=-1.22~-0.41)(P值均 < 0.01)。  结论  不同性别、年龄、营养状况儿童青少年社交焦虑程度不同,睡眠时间延长与社交焦虑分数降低相关。保证充足的睡眠有助于降低儿童青少年的社交焦虑程度,提高心理健康水平。     

运动能力与儿童早期发展

儿童早期发展对个人成年时期,乃至老年阶段的全面发展和健康促进均具有重要意义,受到越来越多的社会关注。本文从早期教育中运动能力培养的角度,总结其对儿童早期体格生长、智力发展、神经心理发育的作用及对特殊儿童疾病干预的影响,为促进儿童健康成长寻找途径和方向。     

Radioprotective Effect of Whey Hydrolysate Peptides against γ-Radiation-Induced Oxidative Stress in BALB/c Mice

Radiation therapy is widely used in the treatment of tumor diseases, but it can also cause serious damage to the body, so it is necessary to find effective nutritional supplements. The main purpose of this study is to evaluate the protective effect of whey hydrolysate peptides (WHPs) against ⁶⁰Coγ radiation damage in mice and explore the mechanism. BALB/c mice were given WHPs by oral gavage administration for 14 days. Then, some mice underwent a 30-day survival test after 8 Gy radiation, and other mice received 3.5 Gy radiation to analyze the changes in body weight, hematology and bone marrow DNA after three and 14 days. In addition, through further analysis of the level of oxidative stress and intestinal barrier function, the possible mechanism of the radioprotective effect of WHPs was explored. The study found WHPs can prolong survival time, restore body weight, and increase the number of peripheral blood white blood cells and bone marrow DNA content in irradiated mice. In addition, WHPs can significantly improve the antioxidant capacity, inhibit pro-inflammatory cytokines and protect the intestinal barrier. These results indicate that WHPs have a certain radioprotective effect in mice, and the main mechanism is related to reducing oxidative damage.