Design of a dynamic measurement system for Bl factor spatial distribution of resonant blood viscoelastic sensor / 生物医学工程学杂志

Bl factor is a key system parameter of the resonant blood viscoelastic sensor. In this paper, a dynamic measurement system for the spatial distribution of Bl factor based on velocity amplitude and motional impedance was designed. The system extracted the velocity amplitude and motional impedance of the coil under the dynamic condition of driving the sensor to generate simple harmonic oscillations using laser displacement and impedance analysis combined with in-phase/quadrature demodulation algorithm, and controlled the equilibrium position of the coil by adjusting the direct current component of the excitation current to realize the position scanning. In the position interval of [-240, 240] μm, the maximum coefficient of variation of the measurement results was 0.077 3%, and the maximum relative error to the simulation results was 2.937 9%, with a linear fitting correlation coefficient R 2 = 0.996 8. The system can be used to accurately measure the spatial distribution of Bl factor of the resonant blood viscoelastic sensor, which provides a technical support for the verification of the design of the sensor magnetic circuit.

Citrate does not Change Viscoelastic Haemostatic Assays after Cardiopulmonary Bypass

Context:Viscoelastic hemostatic assays (VHA) are commonly used to identify specific cellular and humoral causes for bleeding in cardiac surgery patients. Cardiopulmonary bypass (CPB) alterations to coagulation are observable on VHA. Citrated VHA can approximate fresh whole blood VHA when kaolin is used as the activator in healthy volunteers. Some have suggested that noncitrated blood is more optimal than citrated blood for point?of?care analysis in some populations. Aims: To determine if storage of blood samples in citrate after CPB alters kaolin activated VHA results. Settings and Design: This was a prospective observational cohort study at a single tertiary care teaching hospital. Methods and Material: Blood samples were subjected to VHA immediately after collection and compared to samples drawn at the same time and stored in citrate for 30, 90, and 150 min prior to kaolin activated VHA both before and after CPB. Statistical Analysis Used: VHA results were compared using paired T?tests and Bland–Altman analysis. Results: Maximum clot strength and time to clot initiation were not considerably different before or after CPB using paired T?tests or Bland– Altman Analysis. Conclusions: Citrated samples appear to be a clinically reliable substitute for fresh samples for maximum clot strength and time to VHA clot initiation after CPB. Concerns about the role of citrate in altering the validity of the VHA samples in the cardiac surgery population seem unfounded.

Comparison of corneal endothelial cell loss during manual small-incision cataract surgery using viscoelastic-assisted nucleus removal versus continuous balanced salt solution plus technique - Randomized controlled trial

Purpose: The purpose of this study was to compare and analyze the endothelial cell loss during manual small-incision cataract surgery (MSICS) using the viscoelastic-assisted nucleus removal versus basal salt solution plus technique. Methods: This was a prospective randomized trial of 204 patients who underwent MSICS using viscoelastic-assisted nucleus removal (Group 1- OVD) versus basal salt solution plus technique (Group 2- BSS) at a tertiary eye care hospital in North India from January 2018 to 2021. Of these 204 patients, 103 (50.5%) and 101 (49.5%) were allocated to Group 1 and 2, respectively. The parameters assessed were detailed history, demographics, and anterior and posterior segment details. Visual acuity, intraocular pressure (IOP), keratometry, pachymetry, and endothelial cell density were evaluated preoperatively and postoperatively on day 1 and 30. Results: The mean age of the patients was 64.5 � 8.2 years (range 48� years). There were 129 (63.2%) males and 75 (36.8%) females. The mean LogMAR visual acuity for both groups on day 1 (Group 1- 0.3 � 0.1, Group 2- 0.5 � 0.2) and day 30 (Group 1- 0.1 � 0.2, Group 2- 0.1 � 0.1) was statistically significant (P < 0.001), and the mean IOP value showed a statistically significant value (P < 0.009) on day 1 in Group 2 (15.0 � 2.4 mmHg) and on day 30 (P < 0.001) in both the groups (Group 1- 13.6 � 1.8 mmHg, Group 2- 13.5 � 2 mmHg). The horizontal and vertical k values also showed a statistically significant difference on day 1 and day 30 (P < 0.001). The mean percentage change of central corneal thickness (CCT) in Group 1 was 17.7% and in Group 2 was 17.4% on day 1, and it was 1.1% on day 30 in both the groups, which was statistically significant (P < 0.001) compared to preoperative values. The percentage change in endothelial cell density on day 1 was 9% in Group 1 and 4.6% in Group 2, which was statistically significant (P < 0.001). On day 30, it was 9.7% and 4.8%, respectively, which was statistically significant (P < 0.001). Conclusion: Our study highlights statistically significant endothelial cell loss with viscoelastic-assisted nuclear delivery compared to BSS-assisted nuclear delivery during MSICS in a short follow-up of 1 month. The CCT values showed a slight increase, and the keratometry and IOP were unaffected compared to the preoperative parameters in both the groups

Clinical application of viscoelastic point-of-care tests of coagulation-shifting paradigms

Bleeding during cardiac surgery, liver transplant, trauma and post partum hemorrhage are often multifactorial and these factors are dynamic as new factors crop up during the course of management. Conventional tests of coagulation offer information of a part of the coagulation system and also is time consuming. Viscoelastic point of care tests (VE POCTs) like rotational thromboelastometry, thromboelastogram and Sonoclot, are based on analysis of the viscoelastic properties of clotting blood and provide information for the entire coagulation pathway. In this comprehensive review being presented here, we have examined the pros and cons of VE POCTs including clinical, cost and survival benefits. The recommendations of the various guidelines regarding use of VE POCTs in various scenarios have been discussed. The review also tried to offer suggestions as to their optimal role in management of bleeding during cardiac surgeries, extracorporeal membrane oxygenation, left ventricular assist devices, liver transplant and briefly in trauma and postpartum hemorrhage.

Effects of different viscoelastic agents on corneal endothelium of patients after phacoemulsification and foldable IOL implantation / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To analyze the effects of dual viscoelastic agents DisCoVisc and sodium hyaluronate on corneal endothelium of patients after phacoemulsification and foldable intraocular lens(IOL)implantation.METHODS: A total of 247 patients(285 eyes)with cataract treated in Jingmen Aier Eye Hospital between June 2017 and December 2019 were selected, and they were divided into DisCoVisc group(123 cases, 141 eyes)and sodium hyaluronate group(124 cases, 144 eyes)by random number table method. Both groups were treated with phacoemulsification and foldable IOL implantation. DisCoVisc and 1.7% sodium hyaluronate were used as viscoelastic agents in DisCoVisc group and sodium hyaluronate group, respectively. The two groups were compared in terms of intraoperative ultrasound time(UST), cumulative dissipated energy(CDE), time for aspiration of viscoelastic agents after IOL implantation, corneal edema at 1d, 1wk, 1 and 3mo after operation, corneal endothelial cell density(ECD)and ECD loss rates before operation and at 3mo after operation, coefficient variation of corneal endothelial cell size(CV), percentage of corneal hexagonal endothelial cells(6A), intraocular pressure, the proportions of patients with uncorrected visual acuity ≥0.5 and central corneal thickness(CCT)values before and after operation at 1d, 1wk and 1mo.RESULTS:There was no statistically significant difference between the two groups in UST, CDE, aspiration time of viscoelastic agents(P &#x003E;0.05)or corneal edema both rate on day 1 after operation(P&#x003E;0.05). Corneal edema disappeared at 1 wk after operation. The ECD loss rate in DisCoVisc group was significantly lower than that in sodium hyaluronate group at 3mo after operation(P&#x003C;0.05). Intraocular pressure, the proportion of patients with uncorrected visual acuity ≥0.5 and CCT values showed no statistically significant differences between the two groups before and after operation at 1d, 1wk and 1mo(P &#x003E;0.05).CONCLUSION: DisCoVisc, as the viscoelastic agent in phacoemulsification and foldable IOL implantation for patients with Emery-Little grade Ⅱ-Ⅲ lens nucleus hardness, can better protect the patients' corneal endothelium.

Analysis of the causes of high intraocular pressure after implantation of V4c implantable contact lens / 国际眼科杂志(Guoji Yanke Zazhi)

@#High intraocular pressure is the most concerned complication of the implantation surgery of V4c implantable contact lens(ICL). According to the appearance time of intraocular pressure elevation, it can be divided into three periods: the early period(1wk after surgery), the middle period(1-4wk after surgery)and the late period(1-3mo after surgery). During the early period, the intraocular pressure increase is mainly caused by the residue of the intraoperative viscoelastic. In the middle period, the application of the hormone drugs results the elevation of the intraocular pressure. Furthermore, during the late period, persistent increasing of the intraocular pressure may cause the secondary glaucoma. Identifying the mechanism of different periods of intraocular pressure rise correctly and thus formulating a reasonable treatment plan, is of great significance for the prevention of glaucoma and other long-term vision threatening complications. Therefore, this article reviews the appearance time and mechanism of the intraocular pressure rise after surgery.

Use of viscoelastic substance for preventing Descemet's membrane rupture in deep anterior lamellar keratoplasty / Uso de substância viscoelástica na prevenção da ruptura da membrana de Descemet na ceratoplastia lamelar anterior profunda

ABSTRACT Purpose: This study aimed to investigate the effect of using a viscoelastic substance in Descemet's membrane rupture in "double bubble" deep anterior lamellar keratoplasty. Methods: The medical records and videos of surgeries of 40 patients who underwent surgery between January 2014 and July 2015 were retrospectively evaluated. The patients were divided into two groups: 20 patients whose perforation of the posterior stromal wall was performed without administration of any viscoelastic substance (group 1) and 20 patients whose perforation of the posterior stromal wall was performed with administration of viscoelastic substance onto the posterior stroma (group 2). The Descemet's membrane perforation rate was compared between groups. Results: Perforation of the Descemet's membrane was observed in 12 (60.0%) patients in group 1 and only three (15.0%) patients in group 2. This difference was statistically significant (p=0.003). Only one (5%) patient in group 2 had macroperforation during the procedure, and the surgery was converted to penetrating keratoplasty. Eleven (55.0%) patients in group 1 had macroperforation of Descemet's membrane, and surgeries were converted to penetrating keratoplasty. This difference between the groups was statistically significant (p=0.001). Conclusions: Administering a viscoelastic substance onto the posterior stromal side just before puncture is an effective method to decrease the risk of Descemet's membrane perforation in deep anterior lamellar keratoplasty.(AU)

RESUMO Objetivo: Investigar o efeito do uso de uma substância viscoelástica na ruptura da membrana de Descemet em casos de ceratoplastia lamelar anterior profunda em "bolha dupla". Métodos: Foram avaliados retrospectivamente prontuários e vídeos de cirurgias de 40 pacientes operados entre janeiro de 2014 e julho de 2015. Os pacientes foram divididos em dois grupos: 20 pacientes nos quais a parede posterior do estroma foi puncionada sem a colocação de nenhuma substância viscoelástica (grupo 1) e 20 pacientes nos quais uma substância viscoelástica foi aplicada sobre o estroma posterior ao ser puncionada a parede posterior do estroma (grupo 2). A taxa de perfuração da membrana de Descemet foi comparada entre os grupos. Resultados: Observou-se perfuração da membrana de Descemet em 12 casos (60,0%) no grupo 1 e em apenas 3 casos (15,0%) no grupo 2. Essa diferença foi estatisticamente significativa (p=0,003). Apenas um caso (5%) no grupo 2 teve macroperfuração durante o procedimento, sendo a cirurgia então convertida em uma ceratoplastia penetrante. Onze casos (55,0%) no grupo 1 tiveram macroperfuração da membrana de Descemet e essas cirurgias foram convertidas em ceratoplastias penetrantes. Essa diferença entre os grupos foi estatisticamente significativa (p=0,001). Conclusões: A aplicação de substância viscoelástica sobre o lado posterior do estroma logo antes da punção é um método eficaz para diminuir o risco de perfuração da membrana de Descemet na ceratoplastia lamelar anterior profunda.(AU)

Research progress on strategies of reducing perioperative blood transfusion in liver transplantation / 器官移植

Massive blood loss and blood transfusion constantly occur in liver transplantation. Over the past two decades, the amount of blood transfusion during the perioperative period has been decreased dramatically along with the continual maturity of liver transplantation techniques. The goal of liver transplantation without blood transfusion has been achieved. Since bleeding and blood transfusion are correlated with poor prognosis after liver transplantation, reducing bleeding and unnecessary blood transfusion has become the key objective during perioperative period of liver transplantation. In this article, adverse effects of allogeneic blood transfusion during perioperative period of liver transplantation, coagulation function monitoring of patients with end-stage liver disease, blood transfusion management of liver transplant recipients and the strategies of reducing perioperative blood transfusion in liver transplantation were summarized, aiming to provide reference for reducing the requirement of blood transfusion during perioperative period of liver transplantation.

Effect of the vault on corneal endothelial cells after microincision ICL V4c implantation without viscoelastic / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM:To evaluate the effect of the vault on corneal endothelial cells after implantation of central hole implantable lens(ICL)V4c without viscoelastic microincision.<p>METHODS: Prospective non-randomized controlled study. A total of 70 patients(137 eyes)with myopia who underwent ICL V4c implantation in our hospital from November 2017 to February 2018 were divided into low vault group(100μm<vault≤250μm, 37 eyes), medium vault group(250μm<vault≤750μm, 69 eyes)and high vault group(750μm<vault≤900μm, 31 eyes)according to the size of postoperative vault. After 1a of follow-up, the changes of corneal endothelial cell count and anterior chamber parameters were observed.<p>RESULTS:At 1wk after operation, the anterior chamber depth, anterior chamber volume and anterior chamber angle of the three groups were all decreased compared with those before operation(<i>P</i><0.05). There was no significant difference in corneal endothelial cell count among the three groups at different time points before and after surgery. The loss rate of corneal endothelial cells in the low vault group at 1wk, 3mo and 1a after surgery were about 1.2%, 1.5% and 1.7%, respectively. The loss rate of corneal endothelial cells in the middle vault group were about 0.5%, 0.7% and 1.0%, respectively. The loss rate of corneal endothelial cells in the high vault group were about 1.1%, 1.3% and 1.4%, respectively.<p>CONCLUSION:The vault in early period after ICL V4c implantation without viscoelastic microincision had no significant effect on corneal endothelial cells.

Liver transplantation in Jehovah's Witnesses: a case series / Experiencia en trasplante hepático para testigos de Jehová: serie de casos

Abstract Introduction: Orthotopic liver transplantation (OLT) is a procedure characterized by high bleeding rates and a significant likelihood of exposure to blood products. Objectives: This case series shows the experience at a referral center for Jehovah's Witnesses (JW) with end-stage liver disease, undergoing OLT. Materials and methods: A search was conducted in our database of JW undergoing OLT between July 2007 and August 2012. The information about their pre-operative condition and progress up to 30 days post-transplantation. Results: Four subjects were identified (3F/1M) with an average age of 42 years (range 22-55). All of them received a multidisciplinary management which included pre-operative optimization of red cell mass, antifibrinolytic prophylaxis, and cell salvage (mean volume of 344mL [range 113-520]). The average intraoperative bleeding volume was of 625mL (range 300-1000). One of the patients presented with a primary graft dysfunction and died, while the rest had a normal postoperative course. Conclusion: It is possible to offer OLT to patients who refuse to receive allogeneic blood transfusions, through a comprehensive approach that includes perioperative hematologic optimization and the use of blood conservation measures, without a significant impact on the outcomes.

Resumen Introducción: El trasplante hepático ortotópico (THO) es un procedimiento caracterizado por índices significativos de sangrado y alta probabilidad de exposición a hemocomponentes. Objetivos: Esta serie de casos muestra la experiencia de un centro de referencia en la atención de testigos de Jehová (TJ) con enfermedad hepática terminal llevados a THO. Materiales y métodos: Se realizó una búsqueda en nuestra base de datos de TJ que hubiesen sido llevados a THO entre julio de 2007 y agosto de 2012. Se registraron datos correspondientes a su estado preoperatorio, manejo perioperatorio y evolución hasta los 30 días postrasplante. Resultados: Se encontraron cuatro sujetos (3M/1H) con una edad promedio de 42 años (rango de 22-55). Todos recibieron un manejo multidisciplinario que incluyó la optimización preoperatoria de su masa eritrocitaria, profilaxis antifibrinolítica y salvamento celular [volumen promedio de 344 ml (rango de 113-520)]. El volumen promedio de sangrado intraoperatorio fue de 625 ml (rango de 300-1000). Uno de los pacientes presentó disfunción primaria del injerto y muerte, mientras que los demás tuvieron un curso posoperatorio convencional. Conclusiones: Es posible ofrecer la posibilidad de THO para sujetos que se niegan a recibir transfusiones alogénicas, por medio de un abordaje integral que incluya la optimización hematológica perioperatoria y la utilización de medidas de conservación sanguínea, sin que esto afecte significativamente los resultados.

Skin stretching device combined with collagen sponge for wound repair / 中华创伤骨科杂志

Objective To evaluate the feasibility and clinical efficacy of our self-designed simple skin stretching device combined with collagen sponge for management of severe soft tissue wounds.Methods From September 2015 to October 2017,a consecutive series of 43 patients whose soft tissue wounds could not be closed primarily were enrolled for a therapy using a simple skin stretching device made of round osseous pins and wire combined with collagen sponge.They were 27 males and 16 females,with a mean age of 31.5 years (from 5 to 56 years).There were 18 fresh wounds and 25 old ones.Their skin defects ranged from 5.5 cm × 3.0 cm to 18.0 cm × 7.5 cm.After debridement and vacuum sealing drainage,2 round osseous pins with a diameter of 2.0 mm or 2.5 mm were driven through the dermis about 1 to 2 cm from both edges of the wound,in parallel with the longitudinal axis of the wound.After the parts of 2 pins exposed outside the skin were bent,they were fixed respectively with a fine wire with 2 twisted strands.The wounds were continuously stitched with eversion suture.The wires and sutures were gradually tightened to contract the wounds until the skin color changed and capillary filling reaction started.Then medical collagen sponge was used to cover the wounds.Next,the wires and sutures were tightened continuously until the wound edges were pulled together.Details of this therapy and its complications were recorded.Follow-up visits were paid until wound healing.Results Of the 43 cases,the wounds were directly closed immediately after primary stretching procedure in 8,closed after skin stretching for 4 to 12 days (average,7.5 days) in 30,and significantly reduced in 5 which were cured following skin graft.Eventually,40 cases were followed up for an average of 6.8 months (from 3 to 18 months) and 3 were lost.Aesthetic reoperation was performed in 3 patients who were inflicted with postoperative scar formation after skin graft.Linear healing of the wound edges was achieved in 37 patients without complications like skin necrosis,pathological hyperplasia scar,skin sensation deletion or wound infection,leading to fine appearance and functional recovery.Conclusion Our self-designed simple skin stretching device combined with collagen sponge provides a cost-effective and practical technique for clinical treatment of soft tissue defects,with an advantage of reducing or even avoiding secondary repair with skin graft or skin flap.

Síndrome tóxico del segmento anterior en el Hospital Oftalmológico Amistad Argelia-Cuba, en Djelfa / Toxic syndrome of the anterior segment in Amistad Argelia-Cuba Ophthalmological Hospital in Djelfa

Objetivos: describir un brote de síndrome tóxico del segmento anterior ocurrido en el Servicio de Catarata del Hospital Oftalmológico Amistad Argelia-Cuba, en Djelfa, en el año 2015. Métodos: se realizó un estudio descriptivo de corte transversal donde se incluyeron 14 casos notificados con diagnóstico de síndrome tóxico del segmento anterior, operados en el Servicio de Catarata del Hospital Oftalmológico Amistad Argelia-Cuba, en Djelfa, en el período comprendido del 13 al 17 de abril del año 2015. Resultados: la facoemulsificación fue la técnica más empleada. La membrana prelental fue el signo más frecuente encontrado, seguido de la hipertensión ocular y el edema corneal, respectivamente. Todos los casos tuvieron un período de resolución de hasta 7 días. El factor común en los 14 pacientes notificados fue la utilización, por primera vez en nuestro centro, del viscoelástico modelo Viscoelastics HMPM Eye Visc para cirugía intraocular del segmento anterior. Conclusión: la coincidencia de la introducción del viscoelástico dispersivo con la aparición del brote y la ausencia de nuevos casos una vez retirado este, confirma la sospecha de que esta es una de las posibles causas del brote de síndrome tóxico del segmento anterior(AU)

Objectives: to describe an outbreak of the anterior segment toxic syndrome occurred at the cataract service of Amistad Argelia-Cuba ophthalmological hospital in Djelfa in 2015. Methods: a cross-sectional descriptive study was carried out, which included 14 notified cases with diagnosis of segment anterior toxic syndrome, who had been operated on at the cataract service of Amistad Argelia-Cuba ophthalmological hospital in Djelfa, in the period of 13th to 17th April, 2015. Results: phacoemulsification was the most used technique. The prelental membrane was the most frequently found sign, followed by ocular hypertension and corneal edema, respectively. All these cases recovered in 7 days. The common factor found in the 14 confirmed patients were the use for the first time of Viscoelastics HMPM Eye Visc viscoelastic model in our center to perform intraocular surgery in the anterior segment. Conclusions: the coincidence of the introduction of this substance with the onset of outbreak and the lack of new case after its withdrawal has confirmed the suspicion that this is one of the possible causes of the outbreak of the anterior segment toxic syndrome(AU)

Comparison of anterior chamber maintainer and viscoelastic agent on corneal astigmatism and endothelial cells after phacoemulsification / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To compare the influence of anterior chamber maintainer and viscoelastic agent on corneal astigmatism and endothelial cells after phacoemulsification.METHODS:Totally 70 patients(70 eyes) of cataract from April 2013 to April 2015 were randomly divided into the study group and the control group, with 35 cases in each group.The study group were treated with anterior chamber maintainer during phacoemulsification with support system approach, and the control group were treated with phacoemulsification under viscoelastic agent.RESULTS:The age (t=0.215, P=0.831), the density of corneal endothelial cells (t=-0.352, P=0.726) and corneal luminosity (t=-0.162, P=0.872) of two groups had no significant difference before surgery;there were no significant difference in preoperative visual acuity (t=0.463, P=0.599) and visual acuity (t=1.616, P=0.124) at 1mo after operation.And patients in the study group (t=-21.129, P<0.01) and the control group (t=-12.780, P<0.01) before surgery and 1mo postoperative when compared with the naked eye eyesight showed significant difference.The visual acuity after operations improved significantly.There were significant differences of corneal endothelial cells density (t=8.489, P< 0.01) and corneal astigmatism (t=-2.032, P=0.046) in the study group before surgery and 1mo after surgery;corneal endothelial cell density (t=8.999, P<0.01) and corneal astigmatism (t=-2.167, P=0.034) in the control group before surgery and 1mo after surgery also had significant differences.There was no significant difference in the rate of corneal endothelial cell loss between the two groups (t=0.410, P=0.683).CONCLUSION:Compared with viscoelastic agent, anterior chamber maintainer during phacoemulsification in patients with cataract won't increase the damage of postoperative surgically induced astigmatism and corneal endothelial cells, which mean the method of anterior chamber maintainer during phacoemulsification in the treatment of cataract is safe and effective.

Rheological study of hyaluronic acid derivatives

The viscoelastic properties of four novel, low molecular weight hyaluronic acid derivatives were investigated and compared to the parent hyaluronic acid compound. Briefly, all derivatives were synthesized by first deacetylating the parent hyaluronic acid. One sample was left as such, while two others were reacytelated. The final compound, of particular interest for its anti-inflammatory properties, was butyrylated. The compounds were dissolved in phosphate buffer solution (PBS) and studied at a concentration of 5 mg/mL. Shear thinning behaviour was observed for all compounds, however, derivative samples had a lower viscosity than the parent compound at high shear rates. Viscoelastic properties were also observed to decrease as a result of the derivative preparation method. It is believed that these changes are primarily caused by a decrease in hyaluronic acid molecular weight. By increasing the concentration of the anti-inflammatory compound, it may be possible to modulate the viscoelastic properties to more closely resemble those of commercial viscosupplements. As a result, an anti-inflammatory derivative of hyaluronic acid may potentially improve upon existing viscosupplements used to treat patients who are susceptible to flare up.

Viscoat viscoelastic combined with soft corneal contact lens for central corneal perforation / 眼科新进展

Objective To investigate the clinical effects of the Viscoat viscoelastic combined with soft corneal contact lens for central corneal perforation.Methods Six cases were collected and treated with corneal local debridement of which diameter were less than 2.0 mm.Six cases received Viscoat viscoelastic injection into their anterior chamber.And then soft corneal contact lens were worn.The curative effect indicators such as patients' symptom,visual acuity,slit lamp examination,intraocular pressure,confocal microscope and corneal endothelial cell counts were recorded in the follow-up periods.Results All the cases were healed with the recovery time of 1 month to 2 months;After treatment,the best corrected visual acuity of patients were increased to 0.6-0.8 and average corneal endothelial cell count was (3415.5 ±279.5)mm-2.No obvious scar was left in the cornea and no serious complicatious occurred during treatment.Conclusion For traumatic corneal central perforation with diameter is 2.0 mm or less can be treated with Viscoat viscoelastic combined with soft corneal contact lens.This therapy is worthy of popularize since it's satisfied prognosis and less economic burden.

Detection of the viscoelasticity of relaxed myocardium in vivo by intervention ultrasound indentation system / 解放军医学杂志

Objective To explore the viscoelasticity of relaxed myocardium in vivo through indentation method with an intervention ultrasound indentation system (IUIS). Methods Old myocardial infarction (OMI) models of canine were established by ligating left anterior descending branch of coronary artery for 3 months. The indentation creep tests were used respectively in OMI group and shame group (n=8, each) by IUIS in middle and advanced diastole stage in vivo. Test data were processed with three-parameter solid viscoelasticity model, and the viscoelastic parameters, such as instantaneous elastic modulus (E1), relaxation modulus (E∞), creep elastic modulus (E2) and viscous damping coefficient (η) in normal and infarcted myocardium were obtained and compared. Results All the parameters of E1, E∞, E2 and η increased obviously in OMI group than in sham group shown as follows: 27.81±6.74kPa vs. 6.78±2.43kPa; 17.87±3.59kPa vs. 4.52±1.56kPa; 49.54±14.35kPa vs. 16.82±12.37kPa and 1.97±0.78Pa.s vs. 0.66±0.40Pa.s. The differences were statistically significant (P<0.05). Conclusions IUIS is a feasible method to assess the viscoelasticity of relaxed myocardium in vivo. Three-parameter viscoelasticity model can be used to describe creep properties of relaxed myocardium. Both elastic modulus and viscosity resistance have increased in infarcted myocardium.

The Effect of Rhythmic Neurodynamic on the Upper Extremity Nerve Conduction Velocity and the Function for Stroke Patients

PURPOSE: The purpose of this study was to resolve, in an efficient manner, the mechanoreceptor problems of the part far from the paretic upper extremity in stroke patients, as well as to provide clinical basic data of an intervention program for efficient neurodynamic in stroke patients, by developing a rhythmic neurodynamic exercise program and verifying functional changes depending on the increase in the upper extremity nerve conduction velocity. METHODS: Samples were extracted from 18 patients with hemiplegia, caused by stroke, and were randomly assigned to either the experimental group I for the general upper extremity neurodynamic (n=9) and the experimental group II for rhythmic upper extremity neurodynamic (n=9). An intervention program was applied ten times per set (three sets one time) and four times a week for two weeks (once a day). As a pre-test, changes in the upper extremity nerve conduction velocity and functions were assessed, and two weeks later, a posttest was conducted to re-measure them in the same manner. RESULTS: The wrist and palm sections of the radial nerve and the wrist and elbow sections of the median nerve, as well as the wrist, lower elbow, upper elbow, and axilla sections of the ulnar nerve had significant differences with respect to the upper extremity nerve conduction velocity between the two groups (p<0.05)(p<0.01), and significant differences were also found in the upper extremity functions (p<0.05). CONCLUSION: Rhythmic neurodynamic accelerated the nerve conduction velocity more in broader neural sections than the general neurodynamic. In conclusion, rhythmic neurodynamic was proven to be effective for improving the functions of upper extremity.

Effects of Different Angles of the Traction Table on Lumbar Spine Ligaments: A Finite Element Study

BACKGROUND: The traction bed is a noninvasive device for treating lower back pain caused by herniated intervertebral discs. In this study, we investigated the impact of the traction bed on the lower back as a means of increasing the disc height and creating a gap between facet joints. METHODS: Computed tomography (CT) images were obtained from a female volunteer and a three-dimensional (3D) model was created using software package MIMICs 17.0. Afterwards, the 3D model was analyzed in an analytical software (Abaqus 6.14). The study was conducted under the following traction loads: 25%, 45%, 55%, and 85% of the whole body weight in different angles. RESULTS: Results indicated that the loading angle in the L3–4 area had 36.8%, 57.4%, 55.32%, 49.8%, and 52.15% effect on the anterior longitudinal ligament, posterior longitudinal ligament, intertransverse ligament, interspinous ligament, and supraspinous ligament, respectively. The respective values for the L4–5 area were 32.3%, 10.6%, 53.4%, 56.58%, and 57.35%. Also, the body weight had 63.2%, 42.6%, 44.68%, 50.2%, and 47.85% effect on the anterior longitudinal ligament, posterior longitudinal ligament, intertransverse ligament, interspinous ligament, and supraspinous ligament, respectively. The respective values for the L4–5 area were 67.7%, 89.4%, 46.6%, 43.42% and 42.65%. The authenticity of results was checked by comparing with the experimental data. CONCLUSIONS: The results show that traction beds are highly effective for disc movement and lower back pain relief. Also, an optimal angle for traction can be obtained in a 3D model analysis using CT or magnetic resonance imaging images. The optimal angle would be different for different patients and thus should be determined based on the decreased height of the intervertebral disc, weight and height of patients.

An experimental methodology for arterial walls / Análise experimental de paredes arteriais

Numerical simulations of arterial walls allow a better understanding of the interaction between biological tissue and endoprosthesis (stents), which are used in aneurysms or atherosclerosis stenosis treatment. A reliable understanding of this interaction may help one to select, or even design, the best structure for a given clinical indication. The development of a realistic numerical simulation requires an appropriated definition of a constitutive model and the obtainment of experimental data useful to a parameter identification procedure. Biological tissues have different mechanical characteristics of materials commonly used for engineering applications, however the experimental data acquisition is a major challenge. Some examples of technical difficulties of experimental test in biological tissue are associated to the obtainment of samples, temperature and humidity control during storage, suitable gripping and geometric and strain measurements methods. Therefore, this paper presents an experimental methodology to perform uniaxial mechanical tests in pig arteries in order to provide useful information for material models of arterial walls. This study proposes the experimental procedure from the sample obtainment to the uniaxial experimental testing of the tissue in two directions (circumferential and longitudinal) at two strain rates. In order to shown the use of the experimental data into a suitable numerical model for arterial walls, a parameter identification procedure was performed to obtain material parameters of a viscoelastic anisotropic model with fiber dispersion for finite strains. Through the experimental methodology proposed it was possible to obtain useful data for the parameter identification. Moreover, the results demonstrate that the arterial walls mechanical behavior was properly represented by the selected model.

Simulações numéricas de paredes arteriais permitem um melhor entendimento da interação entre tecido biológico e endopróteses (stents), os quais são utilizados no tratamento de aneurismas e lesões obstrutivas ateroscleróticas. O melhor entendimento desta interação pode auxiliar na seleção do modelo ou no projeto da estrutura da endoprótese mais adequada para uma dada indicação clínica. A realização de simulações numéricas realísticas requer a definição apropriada de um modelo constitutivo e a obtenção de dados experimentais adequados para um procedimento de identificação de parâmetros. Diferentemente dos materiais usados comumente em engenharia, a aquisição de dados experimentais de tecidos biológicos representa um grande desafio. Alguns exemplos das dificuldades técnicas associadas aos testes experimentais de tecidos biológicos estão na obtenção de amostras, no controle de temperatura e humidade durante o armazenamento, na fixação adequada e na medição geométrica e de deformações. Portanto, o presente artigo apresenta uma metodologia experimental para realização de testes uniaxiais em artérias suínas, visando fornecer informações adequadas para modelos materiais de paredes arteriais. Este estudo propõe um procedimento experimental que abrange desde a obtenção da amostra até o ensaio uniaxial do tecido em duas direções (circunferencial e longitudinal), com duas taxas de velocidades. Para exemplificar o uso dos dados experimentais em um modelo numérico adequado para paredes arteriais, um procedimento de identificação de parâmetros foi realizado, obtendo parâmetros materiais de um modelo viscoelástico anisotrópico com dispersão de fibras para deformações finitas. Através da metodologia experimental proposta foi possível obter dados úteis para identificação de parâmetros. Além disso, os resultados demonstraram que o comportamento mecânico de paredes arteriais foi representado adequadamente pelo modelo selecionado.

Viscoelastic properties of adjacent segments during prolonged flexion after anterior intervertebral fusion / 医用生物力学

Objective To analyze the viscoelastic properties of adjacent segments after anterior fusion under prolonged flexion, and further reveal the mechanism of accelerated adjacent segment degeneration after intervertebral fusion. Methods The same prolonged flexion lasted 30 minutes was applied on the two-level ovine lumbar specimen before and after anterior fusion respectively, and the moment relaxation and viscoelastic deformation of adjacent segments were measured. The moment relaxation curves from two groups were then fitted to obtain the quantitative viscoelastic results. Results After fusion，the initial and final moment in two groups significantly increased by 30.68% and 34.34%, and the viscoelastic deformation of the adjacent segments increased by 28.21%. The Prony model could perfectly fit the moment relaxation curves (R2=99.50%). The integral stiffness significantly increased by 47.82% and 31.14% for two groups, while the viscoelasticity significantly decreased by 27.19% and 28.16%, respectively(P<0.05). Conclusions After intervertebral fusion, to maintain the same posture with the same time, the joints should bear larger loads than before. The viscoelastic deformation of adjacent segments becomes larger, which increases the risk of instability or injury, and further leads to the accelerated degeneration of adjacent segments. The mechanism of quasi-static daily loading on adjacent segment degeneration should be focused in clinical research.