A biomechanical rationale for C1-ring osteosynthesis as treatment for displaced Jefferson burst fractures with incompetency of the transverse atlantal ligament

Nonsurgical treatment of Jefferson burst fractures (JBF) confers increased rates of C1–2 malunion with potential for cranial settling and neurologic sequels. Hence, fusion C1–2 was recognized as the superior treatment for displaced JBF, but sacrifies C1–2 motion. Ruf et al. introduced the C1-ring osteosynthesis (C1–RO). First results were favorable, but C1–RO was not without criticism due to the lack of clinical and biomechanical data serving evidence that C1–RO is safe in displaced JBF with proven rupture of the transverse atlantal ligament (TAL). Therefore, our objectives were to perform a biomechanical analysis of C1–RO for the treatment of displaced Jefferson burst fractures (JBF) with incompetency of the TAL. Five specimens C0–2 were subjected to loading with posteroanterior force transmission in an electromechanical testing machine (ETM). With the TAL left intact, loads were applied posteriorly via the C1–RO ramping from 10 to 100 N. Atlantoaxial subluxation was measured radiographically in terms of the anterior antlantodental interval (AADI) with an image intensifier placed surrounding the ETM. Load–displacement data were also recorded by the ETM. After testing the TAL-intact state, the atlas was osteotomized yielding for a JBF, the TAL and left lateral joint capsule were cut and the C1–RO was accomplished. The C1–RO was subjected to cyclic loading, ramping from 20 to 100 N to simulate post-surgery in vivo loading. Afterwards incremental loading (10–100 N) was repeated with subsequent increase in loads until failure occurred. Small differences (1–1.5 mm) existed between the radiographic AADI under incremental loading (10–100 N) with the TAL-intact as compared to the TAL-disrupted state. Significant differences existed for the beginning of loading (10 N, P = 0.02). Under physiological loads, the increase in the AADI within the incremental steps (10–100 N) was not significantly different between TAL-disrupted and TAL-intact state. Analysis of failure load (FL) testing showed no significant differences among the radiologically assessed displacement data (AADI) and that of the ETM (P = 0.5). FL was Ø297.5 ± 108.5 N (range 158.8–449.0 N). The related displacement assessed by the ETM was Ø5.8 ± 2.8 mm (range 2.3–7.9). All specimens succeeded a FL >150 N, four of them >250 N and three of them >300 N. In the TAL-disrupted state loads up to 100 N were transferred to C1, but the radiographic AADI did not exceed 5 mm in any specimen. In conclusion, reconstruction after displaced JBF with TAL and one capsule disrupted using a C1–RO involves imparting an axial tensile force to lift C0 into proper alignment to the C1–2 complex. Simultaneous compressive forces on the C1-lateral masses and occipital condyles allow for the recreation of the functional C0–2 ligamentous tension band and height. We demonstrated that under physiological loads, the C1–RO restores sufficient stability at C1–2 preventing significant translation. C1–RO might be a valid alternative for the treatment of displaced JBF in comparison to fusion of C1–2.     

经皮椎体成形术中椎体内压力的测定与分析

目的　从生物力学的角度来分析椎体成形术(PVP)中并发症发生的可能性缘由,并提出科学的预防性建议。方法　对16例具有脊柱椎体骨质疏松症临床诊断的老年尸体腰椎（14具）有椎体压缩性骨折的椎体（其椎体骨密度值T<-2.5）予以C-arm透视机的动态监测下达到临床评价要求的椎体成形术,采用unisensor AG公司生产的直径为2.0mm的微型压力传感器(5mv/bar)和Peekel Instruments GmbH生产的载频放大器及其附属配套软件－SignaSoft6000 (PICAS & SIGNALOG 6000)测定每个椎体的椎体成形术术中椎体内压力的动态变化,采用描述性的统计和非参数统计方法进行统计学上的描述和分析,并就并发症发生的可能性进行临床意义上的分析。结果　每个椎体的椎体成形术均达到临床评价要求,每次推杆（美国Kypho公司提供标准椎体成形术中Yamshi-Nadel套系中推注骨水泥入椎体的器具,每具推杆可容纳骨水泥约1.5mL）推注骨水泥入椎体时所产生的椎体内的压力P(下标 max)不是很高,多数在0.50 bar以下,其所导致的效应具有显著的统计学差异(P<0.01),而每次推杆推注骨水泥入椎体时的椎体内压力面积值P(下标 ares)也不是很高,多数在10.00 Unit以下,其所导致的效应具有显著的统计学差异(P<0.01),两者均呈偏态分布;而且,对每例椎体的第一、二、三、四杆之间两两予以统计学上的分析,在总体存在差异有统计学意义的基础上还发现除第一和二杆、第三和四杆之间外,其他各杆之间存在着差异(a<0.0083)。结论　对骨质疏松性腰椎椎体压缩性骨折行椎体成形术(PVP)时,其在推注骨水泥入病椎时一般3推杆（约4.5ml骨水泥）即可达到推注骨水泥的临床评价要求,已无必要予第四杆等再次将骨水泥推注入病椎,既不作无意义的行为,又减少发生手术并发症的风险。     

螺钉F角对后路单节段固定稳定性的影响

目的　比较4组不同椎弓根螺钉置入方式对后路单节段固定生物力学稳定性的差异。方法　将24具新鲜小牛胸腰椎标本(T11~L3)分为4组,用椎体楔行切除法在L1椎体上制作严重压缩性骨折模型,用4组不同进钉角度行后路单节段椎弓根钉内固定,对固定后的标本施加频率为1.0Hz的前屈／后伸、左／右侧屈和左／右旋转疲劳载荷各3000次,经脊柱三维运动测量系统测量正常、损伤、固定和疲劳后4种状态下固定节段(T13~L1)前屈／后伸、左／右侧屈和左／右旋转运动范围,将其标准化为稳定指数后比较四组内固定方式在4种状态下6个载荷方向上稳定性的差异。结果　4组固定均能显著提高骨折模型在6个载荷方向上的稳定性(P<0.01),而且显著强于正常标本组(P<0.01),但四组间无显著性差异(P>0.05);疲劳试验后4组标本在6个载荷方向上的稳定性均小于各自疲劳试验前,但两者间无显著性差异(P>0.05),且4组间无显著性差异(P>0.05)。结论　只要保证螺钉在椎弓根及椎体内且伤椎螺钉避开骨折区域,螺钉的F角大小不会影响单节段固定的即刻稳定性及疲劳后稳定性。     

Biomechanical evaluation in osteoporosis: ovariectomized rat model

The aim of our study was to investigate the effects of ovariectomy on rat femur biomechanical parameters. Bone mineral density (BMD) and histological investigation were also evaluated. Fourteen female Sprague–Dawley rats (seven ovariectomized, seven control) were used. BMD was measured by dual-energy X-ray absorbsiometry. Bone biomechanical parameters were measured in femoral midshaft with tensile test using a biomaterial testing machine and maximum load, stiffness, energy absorption capacity (structural properties), ultimate stress, ultimate strain, and elastic modulus (material properties) were calculated. Diaphyseal cortical bone thickness was measured by using histological method. The ovariectomized (OVX) rat femur’s BMD was 14% lower than control rats (p=0.006). Mean maximum load was 55% less than the control group’s (p=0.0001). Stiffness was 72% less in OVX rats (p=0.05). Femurs of rats with OVX had 32% less absorbed energy than controls (p=0.09). From the stress–strain curve ultimate stress, ultimate strain and elastic modulus was calculated. Elastic modulus was 53% less than controls (p=0.05). Ultimate stress decreased 21% in OVX rats (p=0.097). Ultimate strain was 25% less than controls in OVX rats. Cortical thickness was significantly decreased in OVX rats than in controls (p<0.05). In conclusion, femur biomechanical parameters are decreased in osteoporosis.     

快速扩张后皮肤生物力学特性的实验研究

本实验研究的目的在于观察皮肤软组织快速扩张后生物力学特性的改变,并与常规扩张、未扩张的皮肤进行对比研究,以了解扩张皮肤生物力学特性的改变与扩张速度的关系,即扩张皮肤24小时应力松弛的程度和应力状态的平衡与一周应力松弛和平衡的区别,为临床快速扩张提供生物力学的研究基础。取4只体重为15kg 左右的猪为实验动物,分为常规扩张组,快速扩张组和对照组;将容量为240ml 的矩形扩张器埋置于筋膜下,按分组要求定期给予扩张;扩张结束后取标本进行皮肤构关系、应力松弛特性、应变能密度和强度参数等生物力学指标的测定,结果表明扩张皮肤的粘弹性明显下降,有别于未扩张的皮肤,而快速扩张皮肤与常规扩张皮肤的粘弹性的下降则非常相似。因此,扩张可致皮肤粘弹性下降,但扩张皮肤粘弹性的下降除与扩张刺激的强度有明显的关系外,尚与扩张刺激的间隔时间有关,但后者的影响较小。临床上可以采用快速扩张的方法,以缩短疗程,提高疗效。     

A nonlinear biomechanical model for evaluation of cerebrospinal fluid shunt systems

In view of complications arising from physical properties of cerebrospinal fluid shunts, a biomechanical model of hydrocephalus was set up to study in vivo parameters that may influence their function. These include: intracranial pressure, compliance and pulses, intrathoracic, intra-abdominal, and subcutaneous pressures, and the effects of siphonage and repeated valve flushing. Each of these factors was studied separately upon shunt implantation in the model. Results of testing of a sample lowpressure valve with antisiphon device conformed with consumer information in regard to valve opening pressure and pressure flow measurements. No customer information, however, was supplied concerning the deleterious effects of direct subcutaneous pressure, variable degrees of siphonage, and repeated valve flushing that were demonstrated by the model. Such results indicate that shunts should be similarly tested prior to marketing and implantation in patients.     

6 Gy γ射线对骨髓细胞生物力学特性的影响

目的了解放射损伤条件下骨髓细胞(包括基质细胞和造血细胞)生物力学特性的改变。方法以6Gy^60Coγ射线照射昆明系小鼠制备动物模型，以细胞电泳法检测骨髓细胞的细胞电泳率，荧光探针法测定细胞膜微黏度，旋转法检测细胞的黏附性，核孔滤膜法检测细胞的变形指数。结果放射损伤后骨髓细胞的变形能力降低，细胞膜微黏度增加，细胞的黏附率和电泳率显著降低。结论6Gy^60Coγ射线对骨髓细胞的生物力学特性有显著影响，可能是放射损伤后造血功能减退的原因之一。     

The effectiveness of biomechanical taping and Kinesiotaping on shoulder pain,active range of motion and function of participants with Trapezius Myalgia: A randomized controlled trial

BackgroundTrapezius Myalgia (TM) is characterized by shoulder pain and dysfunction. Kinesio Taping is commonly used in symptom management of TM. Biomechanical Taping (BMT), a novel intervention, may provide equally effective management.ObjectivesThis paper reports on the effectiveness of Biomechanical Taping compared with Kinesio Taping in improving shoulder pain, active range of motion (AROM), and function.MethodsTwo groups of participants with TM were recruited through simple random sampling of participants from nine call centers and purposively-sampled participants from one fast-food chain and one community based rehabilitation center in Manila, Philippines. Participants were randomly allocated to either Kinesio Taping or biomechanical taping group in a double-blind clinical trial. Irrespective of the type of taping, participants performed gentle passive stretching of upper trapezius for six times each held for 30 s on Days 1, 3, and 5. On Days 2 and 4, participants performed gentle passive stretch of upper trapezius three times a day. Pre- and post-intervention measures were taken of Visual Analogue Scale for pain intensity, AROM for shoulder movement, and Disability of Arm, Shoulder, and Hand for function.ResultsOf 68 participants, 62 had shoulder symptoms secondary to TM. Similar significant within group improvements were found for Visual Analogue Scale scores, and Disability of Arm, Shoulder and Hand for biomechanical taping and Kinesio Taping interventions when comparing between group results (p < 0.05).ConclusionBiomechanical Taping appears to be as effective as Kinesio Taping in the short term in decreasing pain and improving function of individuals with TM. Both taping techniques did not restrict shoulder AROM of included participants.Mesh TermsAthletic Tape, Myalgia, Pain Measurements, Shoulder PainNon-Mesh TermsBiomechanical Taping Technique     

Biomechanical performance of a collagen meniscus implant with regard to suture material and irrigation fluid

Background

The role of meniscus scaffolds remains controversial as failure rates remain high. The aim of this study was to evaluate the pullout strength of different suture materials used for fixation of the Collagen Meniscus Implant (CMI) regarding different suture materials, and type or temperature of irrigation fluid.