股骨型髓内分叉钉的生物力学研究与临床应用

目的 研究新型股骨型髓内分叉钉治疗股骨下段骨折的生物力学特征。方法 将36根成人股骨尸骨标本随机分为三组，并在股骨的下1／4处锯断，做成股骨中下段模型骨折的模型；分别用股骨型髓内分叉钉、Ender钉和梅花钉固定；然后各组分别进行抗钮、抗弯和抗拉生物力学实验。结果 股骨型髓内分叉钉的抗钮、抗弯和抗拉性能明显优于Ender钉和梅花钉。髓内分叉钉的扭强度是Ender钉和梅花钉的2．8倍和4．4倍，抗扭刚度系数α也明显高于Ender钉和梅花钉（P＜0.01)；抗弯强度是Ender钉和梅花钉的2．3倍和1．4倍，抗弯刚度系数β也明显高于Ender钉和梅花钉（P＜0.01)；髓内分叉钉的抗拉强度随位移的增加而逐渐增大；当位移达到5mm时，抗拉强度是Ender钉和梅花钉的1．7倍和4．5倍。结论 髓内分叉钉的设计符合股骨下段解剖特点，具有良好的生物力学性能，股骨型髓内分叉钉是一种治疗股骨骨折的新型髓内固定器械。     

胫骨型髓内分叉钉治疗胫骨骨折的生物力学研究

目的　对胫骨型髓内分叉钉 (TITN)内固定胫骨骨折的生物力学性能进行实验研究 ,为临床应用提供理论依据。方法　采用 36根湿尸体胫骨标本进行实验 ,比较TITN与矩形钉 ,Ender钉及梅花钉固定之胫骨骨折在抗扭转、抗弯曲和抗轴向拉伸刚度等方面差异性。结果　扭转试验、弯曲试验及轴向拉伸试验结果均表明TITN的抗扭、抗弯、抗轴向拉伸刚度均优于矩形钉、Ender钉、梅花钉 (P <0 0 5 )。结论　TITN有良好的生物力学性能 ,有较强的骨折固定作用和稳定性 ,尤其在抗旋转和抗拉性能方面     

胫骨型髓内分叉钉治疗胫骨骨折的生物力学研究

目的：对胫骨型髓内分叉钉（TITN）内固定胫骨骨折的生物力学性能进行实验研究,为临床应用提供理论依据。方法：采用36根湿尸体胫骨标本进行实验,比较TITN与矩形钉,Ender钉及梅花钉固定之胫骨骨折在抗扭转、抗弯曲和抗轴向拉伸刚度等方面差异性。结果：扭转试验、弯曲试验及轴向拉伸试验结果均表明TITN的抗扭、抗弯、抗轴向拉伸刚度均优于矩形钉、Ender钉、梅花钉（P＜0.05）。结论：TITN有良好的生物力学性能,有较强的骨折固定作用和稳定性,尤其在抗旋转和抗拉性能方面。     

矩形髓内钉治疗胫腓骨骨折的生物力学研究

为进一步探讨矩形髓内钉良好疗效的生物力学机制 ,设计本实验研究。 1 2对 2 4根人体胫骨标本分为两组 ,以同一人体左右侧作自身对照。实验组行矩形髓内钉固定 ,对照组行Ender钉固定。其中 6对标本行扭转试验 ,测量扭转变形位移及扭角值 ,描绘扭矩—扭角曲线 ,并计算扭转刚度 ,结果进行统计学处理 (t检验 )。其余 6对标本按内→外、外→内、前→后、后→前四个方向 ,行三点弯曲试验 ,测量弯曲负载、角位移值 ,数据处理同前。结果显示实验组的扭转负载及前、后弯曲负载均大于对照组 (Ender钉 ) (P <0 0 1 ) ,而侧方弯曲负载与对照组无显著性差异 (P >0 0 5)。实验组内旋扭转刚度为对照组的 3 3倍 ;外旋扭转刚度为对照组 4 6倍 ;前→后弯曲刚度为对照组的 4 1倍 ;后→前弯曲刚度为对照组 1 7倍。认为矩形髓内钉在抗旋转及前后抗弯等生物力学性能方面优于Ender钉。     

叉型股骨自锁髓内钉治疗股骨骨折的生物力学研究

目的 对叉型股骨自锁髓内钉(Tridentate self-locking intramedullary femoral.nail,TSIFN)力学性能进行实验研究,为临床应用提供依据。方法 采用8具成人新鲜尸体股骨标本进行应力分析实验。比较用TSIFN、梅花钉、Orthofix公司生产的第三代交锁髓内钉固定的股骨骨折在抗压、抗弯、抗扭强度、刚度及其系统承载能力等方面的差异性。结果 实验结果表明:TSIFN在抗压、抗弯、抗扭强度和刚度及其系统承载能力均优于梅花钉内固定(P<0.05)。与Orthofix交锁髓内钉两者无显著性差异(P>0.05)。结论 TSIFN不但生物力学性能优越,强刚度符合生物力学要求,而且应力遮挡小,远端毋需交锁,弹性固定,固定牢靠,能加速骨折愈合,且手术操作简单,便于推广应用。     

解剖型矩形髓内钉的生物力学评价及临床应用初步报告

目的：为进一步完善矩形髓内钉在胫骨骨折中的应用,克服其操作时容易交叉,对胫骨上段骨折固定力学性能较差等不足,作者设计了胫骨解剖型可屈性矩形髓内钉,并将其与原矩形髓内钉进行生物力学比较后初步应用于临床。方法：将新鲜成人胫骨标本制造胫骨上１／３ 与中１／２ 横断骨折模型,分别用２ 种矩形髓内钉进行固定,并进行生物力学测试。结果：对胫骨上１／３ 骨折,解剖型矩形髓内钉的抗弯能力是普通矩形髓内钉的２－５ 倍（ 冠状面） 和４－３ 倍（ 矢状面） ,抗扭能力是后者的３－９ 倍;对胫骨中段骨折,解剖型矩形髓内钉的抗弯能力是后者的１－８ 倍（ 冠状面） 和１－５ 倍（ 矢状面） ,抗扭能力为１－６ 倍。结论：解剖型矩形髓内钉是在研究胫骨髓腔解剖学特点基础上进行设计的,其生物力学特性优良,初步临床应用已取得了较好效果,值得进一步推广。     

一种新型弹力内锁钉的生物力学评价

目的研制一种新型的骨折内固定器械,即弹力内锁髓内钉,对其进行生物力学性能测试,为临床应用提供依据。方法用8付新鲜成人股骨标本,制成股骨中下2／5骨折,分别用弹力内锁髓内钉、国产内锁髓内钉、钢板及梅花钉内固定,对内固定后的标本进生物力学测试,用Spss统计软件对实验数据进行分析。结果弹力内锁钉抗旋转刚度接近交锁髓内钉,钢板最强,梅花钉最差。结论弹力内锁钉在冶疗股骨中下段骨折中固定可靠,符合生物力学要求。该器械结构合理,简单实用,有一定的临床价值。     

股骨自锁髓内钉的设计与生物力学特性

目的设计一种操作简便的新型髓内钉———斜面型自锁髓内钉(SLN),并测试其生物力学特性。方法本型SLN通过斜面结构的原理将轴向推动力转化为横向推动力,从而实现通过髓内钉尾部的运动控制横钉的收缩运动,进一步通过横钉的髓内把持作用实现带锁髓内钉的功能。在制成原型钉后,以10根股骨为标本制造股骨中上端骨折模型的实际操作,验证该结构运动的可行性和可靠性,通过X线片检查髓内固定情况。模拟单腿负重的受力力线,在instron-1342型MTS机测试拉、压、弯、扭等力学指标。结果该结构能够顺利完成设计动作,运动过程稳定、可靠,髓内固定情况满意;横钉与主钉接触面间可提供相当的剪切力切断可能的包绕物。在拉、压、弯、扭四项指标上,本型SLN的性能与G-K型带锁髓内钉接近,较分叉型自锁髓内钉略优,比梅花针和Ender氏髓内钉明显优越。结论本型SLN结构简单,运动可靠,在主要的受力面上无明显的应力集中点;受力合理,生物力学性能满意,基本能够达到设计要求;操作简便。     

胫骨髓腔形态学测量与解剖型胫骨弹性髓内钉的设计

目的在研究胫骨髓腔解剖的基础上设计一种解剖型胫骨弹性髓内钉,并测量其生物力学性能.方法选择35枚成人胫骨标本,根据X线片测量结果获得髓内钉的腰段长度、前锥度、后锥度、弧度等形态参数,制作髓内钉,并在胫骨中段骨折模型上进行生物力学测试,比较其抗弯,抗扭转性能.结果解剖型弹性髓内钉固定胫骨干骨折的抗弯能力是矩形髓内钉的1.8倍和1.5倍.抗扭转能力是其1.6倍.结论胫骨解剖型弹性髓内钉是一种更复合胫骨骨折内固定的弹性髓内钉.     

自动空心分叉交锁加压髓内钉固定股骨骨折的生物力学原理

目的：目前应用国外带锁G－K钉,由于技术要求高,又需昂贵设备,难于普及应用,我院在此基础上,成功研制出自动空心分叉交锁加压髓内钉（AFLN）,它能广泛应用于股骨髁上7cm至转子下股骨干各类型骨折,本文通过生物力学试验论证的疗效为临床提供科学依据。方法：采用8具新鲜尸体股骨,以AFLN内固定,与国外GK钉,国内梅花钉（SN）及实心自动开叉交锁加压髓内钉（ALN）在生物力学性能上比较它们的优劣。结果：结果表明,AFLN在抗压抗弯抗扭强度、刚度与承载能力上比对照组优越,两者具有显著差异（P＜0．01）。结论：该钉不但在生物力学性能上优越,而且无应力遮挡作用。具有操作简便、固定牢靠,疗效明显的特点,可广泛应用于临床。     

Vasopressor hormone response following mesenteric traction during major abdominal surgery

Background : We investigated the vasopressor hormone response following mesenteric traction (MT) with hypotension due to prostacyclin (PGI₂) release in patients undergoing abdominal surgery with a combined general and epidural anesthesia. Methods : In a prospective, randomized, placebo-controlled study we administered 400 mg ibuprofen (i.v.) in 42 patients scheduled for abdominal surgery. General anesthesia was combined with epidural anesthesia (T4-L1). Before as well as 5, 15, 30, 45, and 90 min after MT we recorded plasma osmolality, hemodynamics and measured 6-keto-PGFlα (stabile metabolite of PGI₂), TXB₂ (stabile metabolite of thromboxane A₂) active renin, and arginine vasopressin (AVP) plasma concentrations by radioimmunoassay. Catecholamine levels were assessed by high-pressure liquid chromatography (HPLC) with electrochemical detection. Results : Following MT, arterial hypotension occurred along with a substantial PGI₂ release. This was completely abolished by ibuprofen administration. Although plasma levels of 6-keto-PGF_1α (1133 (708) vs. 60 (3) ng/L, median (median absolute deviation), P=0.0001, placebo vs. ibuprofen) remained significantly elevated, blood pressure was restored within 30 min after MT in the placebo group. At the same point in time plasma concentrations of TXB² (164 (87) vs. 58 (1) ng/L, P=0.0001), epinephrine (46 (33) vs. 14 (6) ng/L, P=0.001), AVP (41 ± (18) vs. 12 (7) ng/L, P=0.0004), and active renin (27 (12) vs. 12 (4) ng/L, P = 0.001) were significantly higher in placebo-treated patients. Conclusion : Under combined general and epidural anesthesia arterial hypotension following MT due to endogenous PGI₂ release is associated with enhanced release of AVP, active renin, epinephrine and thromboxane A₂, presumably contributing to hemodynamic stability within 30 min after MT.     

A Teaspoon Pump for Pumping Blood with High Hydraulic Efficiency and Low Hemolysis Potential

Abstract: Virtually all blood pumps contain some kind of rubbing, sliding, closely moving machinery surfaces that are exposed to the blood being pumped. These valves, internal bearings, magnetic bearing position sensors, and shaft seals cause most of the problems with blood pumps. The original teaspoon pump design prevented the rubbing, sliding machinery surfaces from contacting the blood. However, the hydraulic efficiency was low because the blood was able to "slip around" the rotating impeller so that the blood itself never rotated fast enough to develop adequate pressure. An improved teaspoon blood pump has been designed and tested and has shown acceptable hydraulic performance and low hemolysis potential. The new pump uses a nonrotating "swinging" hose as the pump impeller. The fluid enters the pump through the center of the swinging hose; therefore, there can be no fluid slip between the revolving blood and the revolving impeller. The new pump uses an impeller that is comparable to a flexible garden hose. If the free end of the hose were swung around in a circle like half of a jump rope, the fluid inside the hose would rotate and develop pressure even though the hose impeller itself did not "rotate"; therefore, no rotating shaft seal or internal bearings are required.     

Microspheres Based Detoxification System: A New Method in Convective Blood Purification

Abstract: A variety of protein-bound or hydrophobic substances, accumulating as a result of pathologic conditions such as exogenous or endogenous intoxications, are removed poorly by conventional detoxification methods because of low accessibility (hemodialysis), insufficient adsorption capabilities (hemosorption), low efficiency (peritoneal dialysis), or economic limitations (high-volume plasmapheresis). Combining advantages of existing methods with microspheric technology, a module-based system was designed. Major operating parameters of the latter can be modified to allow for adjustment to individual clinical situations. An extracorporeal blood circuit including a plasmafilter is combined with a secondary high-velocity plasma circuit driven by a centrifugal pump. Different microspheric adsorbers can be combined in one circuit or applied in sequence. Thus, a prolonged treatment can be tailored using specially designed selective adsorber materials. Comparing this system with existing methods (high-flux hemodialysis, molecular adsorbent recycling system), results from our in vitro studies and animal experiments demonstrate the superior efficiency of substance removal.     

Tissue perfusion in relation to cardiac output during continuous positive-pressure ventilation and administration of propranolol or verapamil

Background : Our objective was to determine whether administration of propranolol or verapamil modifies the hemodynamic adaptation to continuous positive-pressure ventilation (CPPV), in particular the regional distribution of cardiac output (CO).
Methods : General hemodynamics and regional blood flows assessed by microsphere technique (15 (μm) were recorded in 16 anesthetized pigs during spontaneous breathing (SB) and CPPV with 8 cm H₂O end-expiratory pressure (CPPV8) before and after intravenous administration of propranolol (0.3 mg · kg⁻¹ followed by 0.15 mg · kg⁻¹ · h⁻¹, n=8) or verapamil (0.1 mg · kg⁻¹ followed by 0.3 mg · kg⁻¹ · h⁻¹, n=8).
Results : CPPV8 depressed CO by 25% without shifts in its relative distribution with the exception of a noteworthy increase in adrenal perfusion. Propranolol increased arterial blood pressure, and due to a fall in heart rate, CO dropped by 25%. The kidneys and, to a lesser extent, the splanchic region and central nervous system received increased fractions of the remaining CO at the expense of skeletal muscle flow. Similar patterns were seen during SB and CPPV8 such that the combination of propranolol and CPPV8 depressed CO by 50%. The circulatory effects of verapamil were less evident but myocardial perfusion tended to increase.
Conclusions : The combination of propranolol or verapamil with CPPV does not result in any specific hemodynamic interaction in anesthetized pigs, except that the combined effect of propranolol and CPPV may severely reduce CO.     

Volatile anaesthetics reduce adhesion of blood platelets under low-flow conditions in the coronary system of isolated guinea pig hearts

Background : Inhibitory effects of volatile anaesthetics on platelet aggregation have been demonstrated in several studies. However, the influence of volatile anaesthetics on intracoronary platelet adhesion has not been elucidated so far.
Methods : Isolated hearts of guinea pigs were perfused with buffer in the absence or presence of volatile anaesthetics (0.5 and 1 MAC) at constant coronary flow rates of 5 ml/min for 25 min, then 1 ml/min for 30 min and again 5 ml/min for 10 min. Before, during and after low-flow perfusion, a bolus of human platelets was applied into the coronary system. To simulate thrombogenic conditions, 0.3 U/ml human thrombin was infused during low-flow perfusion and reperfusion. The number of platelets sequestered to the endothelium was calculated from the difference between coronary in- and output of platelets. The myocardial production of lactate and consumption of pyruvate and coronary perfusion pressure were also determined.
Results : At a flow rate of 5 ml/min only about 3% of the applied platelets did not emerge from the coronary system, in any group. In contrast, 13.1±1.2% (mean±SEM) of infused platelets became adherent in low-flow perfusion in the control group without anaesthetic. The adherence was reduced with each 1 MAC isoflurane (to 6.2±1.2%), sevoflurane (to 4.4±0.9%) or halothane (to 3.2±1.5%) (each P <0.05 vs. control). Volatile anaesthetic, 0.5 MAC, did not inhibit platelet adhesion to a statistically significant extent in any case. Perfusion pressure and metabolic parameters were not statistically different between the control and the hearts exposed to anaesthetics.
Conclusion : Volatile anaesthetics in a concentration of 1 MAC can reduce the adhesion of platelets in the coronary system under reduced flow conditions. This action does not arise from vasodilation or inhibition of ischaemic stress.     

Bariatric Surgery in Some "Central and East-European (former Eastern bloc)"Countries - Current Status and Prediction for the Next Millennium

Background: Obesity is increasing globallly, including in the formerly "Eastern Bloc" countries. Methods: A survey was made of obesity and bariatric surgery. Results: In the 8 East and Central European countries studied, with total population 300 million, roughly 43% of the population was overweight (BMI 25-30), 23% obese (BMI > 30), with about 15 million people morbidly obese (BMI > 40). From 0-10 morbidly obese individuals/100,000/year undergo bariatric surgery. Conclusion: Most countries were found to provide inadequate treatment for obesity.The majority of the morbidly obese are not treated effectively. However, health-care awareness of obesity and bariatric surgeons are slowly increasing.     

Synergistic interaction between the effects of propofol and midazolam with fentanyl on phrenic nerve activity in rabbits

Background: It has been shown that the depressive effects of both propofol and midazolam on consciousness are synergistic with opioids, but the nature of their interactions on other physiological systems, e. g. respiration, has not been fully investigated. The present study examined the effect of propofol and midazolam alone and in combination with fentanyl on phrenic nerve activity (PNA) and whether such interactions are additive or synergistic. Methods: PNA was recorded in 27 anaesthetised and artificially ventilated rabbits. In three groups, propofol, fentanyl and midazolam were administered intravenously in incremental doses to construct dose-response curves for the depressant effects of each one on PNA. In another two groups, the effect of pretreatment with either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. on the effects of propofol and fentanyl respectively on PNA were studied. Results: Propofol and fentanyl caused a dose-dependent depression of PNA with complete abolition at the highest total doses of 16 mg · kg^?1 i. v. and 32 μg · kg^?1 i. v., respectively. In contrast, midazolam in incremental doses to a total of 0.8 mg · kg^?1 reduced mean PNA by 63%, but approximately 12% of PNA remained at a total dose as high as 6.4 mg · kg^?1. The mean ED₅₀s, calculated from dose-response curves, were 5.4 mg · kg^?1, 3.9 μg · kg^?1 and 0.4 mg · kg^?1 for propofol, fentanyl and midazolam, respectively. Initial doses of either fentanyl 1 μg · kg^?1 i. v. or midazolam 0.05 mg · kg^?1 i. v. acted synergistically with subsequent doses of either propofol or fentanyl to abolish PNA at total doses of 8 mg · kg^?1 and 8 μg · kg^?1, respectively. Conclusion: Fentanyl has a synergistic interaction with both propofol and midazolam on PNA and hence potentially on respiration.     

Influence of dopexamine hydrochloride on haemodynamics and regulators of circulation in patients undergoing major abdominal surgery

Background: Catecholaminergic support is often used to improve haemodynamics in patients undergoing major abdominal surgery. Dopexamine is a synthetic vasoactive catecholamine with beneficial microcirculatory properties. Methods: The influence of perioperative administration of dopexamine on cardiorespiratory data and important regulators of macro- and microcirculation were studied in 30 patients undergoing Whipple pancreaticduodenectomy. The patients received randomized and blinded either 2 μg · kg^?1 · min^?1 of dopexamine (n=15) or placebo (n=15, control group). The infusion was started after induction of anaesthesia and continued until the morning of the first postoperative day. Endothelin-1 (ET-1), vasopressin, atrial natriuretic peptide (ANP), and catecholamine plasma levels were measured from arterial blood samples. Measurements were carried out after induction of anaesthesia, 2 h after onset of surgery, at the end of surgery, 2 h after surgery, and on the morning of the first postoperative day. Results: Cardiac index (CI) increased significantly in the dopexamine group (from 2.61±0.41 to 4.57±0.78 1 · min^?1 · m^?2) and remained elevated until the morning of the first postoperative day. Oxygen delivery index (DO₂I) and oxygen consumption index (VO₂I) were also significantly increased in the dopexamine group (DO₂I: from 416±91 to 717±110 ml/m² · m²; VO₂I: from 98±25 to 157±22 ml/m² · m²), being significantly higher than in the control group. pHi remained stable only in the dopexamine patients, indicating adequate splanchnic perfusion. Vasopressive regulators of circulation increased significantly only in the untreated control patients (vasopressin: from 4.37±1.1 to 35.9±12.1 pg/ml; ET-1: from 2.88±0.91 to 6.91±1.20 pg/ml). Conclusion: Patients undergoing major abdominal surgery may profit from prophylactic perioperative administration of dopexamine hydrochloride in the form of improved haemodynamics and oxygenation as well as beneficial influence on important regulators of organ blood flow.     

Immunomodulation in Transplantation with Photopheresis

Abstract: Photopheresis is a technique in which peripheral blood mononuclear cells, in the presence of a photoacti-vatable compound, are exposed extracorporeally to ultraviolet A light and reinfused, inducing a host autoregula-tory immune response. Experimental work and ongoing clinical studies are helping to define the role of this novel, safe, and non-toxic immunomodulating technology in the field of transplantation.