Throwing induces substantial torsional adaptation within the midshaft humerus of male baseball players

Athletes participating in unilateral dominant sports are useful models for investigating skeletal responses to mechanical loading as they provide controlled evidence in the absence of completing a randomized controlled trial. Throwing athletes may be an additional model for this purpose as they overload their dominant upper extremity enabling the contralateral side to act as an internal control and load the bones of the upper extremity purely via the generation of internal (i.e. muscular) forces without superposition of externally applied loads (i.e. impact with an external object). The aim of this study was to investigate upper extremity bone adaptation in throwing athletes and explore factors that predict this adaptation. Two cohorts were recruited—male baseball players (throwers; n = 15) and matched controls (controls; n = 15). Each subject was assessed for shoulder range and strength, and upper extremity bone mass, structure and estimated strength. Throwers had substantially greater skeletal differences between their dominant and nondominant upper extremities than controls, indicating that throwing induces greater adaptation than induced by habitual loading of the dominant upper extremity. Bone adaptation in throwers was localized to the humerus, with the midshaft humerus in the dominant upper extremity of throwers having enhanced bone mass, structure and estimated strength. The largest effect was for estimated strength of the midshaft humerus which had 30% greater polar moment of inertia (I_P) in throwers and suggests adaptation to resist torsional loads. The skeletal effect of throwing at the midshaft humerus was influenced by playing position with pitchers and catchers displaying greater dominant-to-nondominant differences than fielders, and was predicted by years throwing and dominant-to-nondominant difference in upper arm lean cross-sectional area. The latter two variables explained 67% of the variance in dominant-to-nondominant differences in I_P. Collectively, these data indicate that throwing induces substantial adaptation within the midshaft humerus. Adaptation was primarily in the direction of torsion which is consistent with biomechanical and injury data suggesting throwing introduces high magnitude torsional forces. As the magnitude of adaptation in throwers was equivalent to that observed in athletes participating in other unilateral dominant sports, throwers represent an alternative model for investigating the skeletal effects of mechanical loading.     

骨胶原与骨质疏松骨密度及骨生物力学的相关性研究

目的探讨骨胶原含量在绝经后骨质疏松症的发生、发展及在骨质疏松性骨折中的作用。方法取7个月龄未交配雌性SD大鼠60只，随机分为四组，A组：对照组（sham组）；B组：切除卵巢组；C组：切除卵巢＋雌激素治疗组；D组：切除卵巢＋降钙素治疗组。除A组外，其他三组通过切除双侧卵巢法12周后制成骨质疏松模型，24周后分别行k的力学特性、右侧股骨三点弯曲试验、羟脯氨酸含量、k骨密度（BMD）测定，Masson三色染色法显示骨胶原形态。结果A、C、D组与B组在k羟脯氨酸含量、BMD、k压缩力学参数值、右侧股骨生物力学参数值、骨胶原染色含量及形态方面差异均有统计学意义（P〈0．05），而A、C、D组之间差异无统计学意义（P〉0．05）。统计学分析显示羟脯氨酸含量与BMD及骨生物力学参数值呈直线相关性。结论骨质疏松的发生与骨胶原含量下降有关。骨胶原含量的下降与BMD降低及骨生物力学改变呈相关性。应用雌激素和降钙素治疗去势后骨质疏松大鼠，不仅可以提高其BMD含量和骨生物力学性能，而且还可以提高骨胶原的含量。     

下颈椎经关节螺钉钉棒系统固定的生物力学研究

目的：比较下颈椎三柱损伤后单独经关节螺钉固定（TAS）、经关节钉棒系统同定（TRS）和侧块螺钉钉棒系统固定（LRS）的三维稳定性。方法：12具新鲜颈椎标本．制成C4／5、C5／6节段三柱损伤模型，分别进行单独经关节螺钉（TAS组）、经关节螺钉钉棒系统（TRS组）和侧块螺钉钉棒系统（LRS组）三种方法固定，在非限制性和非破坏性的实验条件下测试其前屈、后伸、左右侧弯和轴向旋转运动状态的稳定性。结果：TAS组和TRS组在各方向的运动范同（ROM）和中性区（NZ）的均数均显著小于完整标本组，差异有统计学意义（P〈0．05）；LRS组在前屈、后伸、侧弯运动中的ROM和NZ与完整标本组比较有显著降低，差异有统计学意义（P〈0．05）；LRS组在旋转运动中的ROM和NZ与完整标本组比较有不同程度的降低，但差异无统计学意义（P〉0．05）。TAS、TRS在各个方向稳定性明显优于LRS组（P〈0．05）。TRS在前屈运动中的ROM和NZ与TAS组比较有所减小，但无统计学意义（P〉0．05）；在后伸、侧弯和旋转运动中，TRS组稳定性明显优于TAS组，有统计学意义（P〉0．05）。结论：在下颈椎三柱损伤选择经关节固定技术时以钉棒形式同定稳定性更好。     

单节段与双节段椎弓根螺钉固定胸腰椎单椎体骨折的生物力学比较

目的:比较单节段与双节段椎弓根螺钉固定术固定胸腰椎单椎体骨折的生物力学效果。方法:在16具新鲜小牛胸腰椎标本(T11-L3)的L1椎体上制作不完全爆裂骨折模型,分为两组,分别行单节段与双节段椎弓根螺钉固定,对固定后的标本施加扭矩为4Nm的疲劳载荷共2000次,加载频率为0.5Hz,经脊柱三维运动测量系统测量正常、损伤、固定和周期性加载后固定节段前屈/后伸、左/右侧弯和左/右旋转运动时固定节段的运动范围。结果:单节段固定组前屈、后伸、侧屈、旋转稳定指数(SPI)分别为0.78、0.80、0.92、0.83,双节段固定组SPI分别为0.88、0.89、0.95、0.85,在前屈方向单节段固定组明显小于双节段固定组(P<0.01);疲劳后,单节段固定组SPI在前屈、后伸、侧屈、旋转方向分别降低0.05、0.03、0.05、0.11,降低值均大于双节段固定组,且在旋转和侧屈方向有显著性差异(旋转:P<0.01;侧屈:P<0.05)。结论:两种术式均可重建脊柱骨折即刻稳定性,效果无明显差异。在旋转、侧屈方向,双节段椎弓根螺钉固定术抗疲劳载荷效果优于单节段固定术。     

梗阻性脑积水侧脑室及室周脑组织生物力学响应的有限元分析

目的运用有限元方法对梗阻性脑积水进行计算机模拟,研究分析侧脑室及室周脑组织的生物力学响应及其所产生的病理生理影响。方法依据正常国人颅脑MRI轴位T2加权图像获取解剖信息,在有限元软件ANSYS中生成包含侧脑室前、后角和体部的半侧脑层面的二维有限元模型。模拟脑组织为固、液两相物质组成的线性多孔弹性材料,设定生物力学特性参数及边界条件和初始条件,施加载荷,运用有限元软件ABAQUS进行计算求解,以云图形式输出结果。结果有限元模型动态模拟了梗阻性脑积水侧脑室各部的扩张过程,直观显示出各个时间步室周脑组织内的应力类型及分布、各部的应变和位移。结论膨胀性应力集中引起角部脑水肿;梗阻性脑积水早期侧脑室角部形态变化最明显;体部附近脑组织结构容易受压移位。这些生物力学响应是室内压增高的结果,也与侧脑室的解剖形态密切相关。     

Biology and Biomechanics in Osteosynthesis of Proximal Humerus Fractures

Abstract Surgical treatment of proximal humeral fractures still remains a challenge. This is primarily due to the fact that sufficient implant fixation in humeral head fractures is often not achieved due to substantial bone tissue loss with increasing age. In the last few years the locking plates and locking nails have been introduced into clinical practice with varying results. The biomechanical studies have focused on locking plate osteosynthesis as well. The following paper focuses on bone quality, biomechanical studies and biology of proper osteosynthesis and reviews the most recent literature.     

尺骨假关节成形术尺桡骨的生物力学变化

目的了解尺骨假关节成形术对尺桡骨应力的影响。方法用新鲜尸体上肢标本 9只 ,于尺桡骨远端背侧骨表面粘贴应变片 ,在前臂中立位 ,旋前和旋后 40°位 ,应用动态加载方法研究其应力变化。结果尺骨假关节成形术后 ,尺骨切骨远端应力升高 (P <0 0 5 )。桡骨远端应力无变化 (P >0 0 5 )。术后桡骨承受的轴向压力显著升高。结论尺骨假关节成形术在改善前臂旋转功能和稳定腕关节的同时 ,可能对肱桡关节造成不利影响 ,临床上值得重视     

股骨颈骨折粗细双螺钉内固定生物力学研究

股骨颈骨折内固定方法繁多。本文采用一粗一细加压螺纹钉，采用先进电阻应变仪方法，对股骨颈的应力分布规律在中立、外展、内收不同位置上施加50kg荷载压力．通过电阻应变计测定一耗一细两钉所承受拉、压应力优于其它内固定形式。     

新型胫骨髓内钉的研制与生物力学研究

目的　研制新型胫骨串孔型髓内钉并对其进行生物力学研究。方法　用TAMZ合金制造远端锁孔由一个三个同样直径的串孔所替代的 9根新型胫骨髓内钉。将髓内钉安装在自行设计的夹具中 ,先将 3根新钉进行静态垂直压缩实验 ,根据静态实验结果 ,分别测试 6根新钉的动态疲劳强度。结果　新钉的静态压缩破坏载荷为 2 1 33N ,是人平均体重的 3倍多 ;通过 5 0万次压缩循环的条件疲劳强度为 1 2 0 0N ,约是人体重的 2倍。结论　新钉不仅能够方便临床使用 ,而且拥有较好的力学特性     

中下段颈椎的应力松弛特性及前、后路手术对其的影响

目的 研究中下段颈椎的应力松弛特性，并评估椎间盘切除植骨术与椎板切开术对其影响。方法 6例新鲜尸体完整颈椎及手术后颈椎，在模拟生理状态下进行屈曲及伸展位的应力松弛实验。结果 在恒应变条件下，绘制术前及不同术式后的中下段颈椎的应力松弛函数及曲线；术后的中下段颈椎的应力和初始化应力比值G(t)比术前明显增大，前路椎间盘切除植骨术后的G(t)值比椎板切开术大，两者均有统计学意义。结论 在恒应变条件下，颈椎具有快速应力松弛敏感性，屈曲位比伸展位大。椎板成形术及颈椎前路椎间盘切除植骨术都使颈椎的应力松弛能力减弱，前路椎间盘切除植骨术的影响更大。