Simulation of transcatheter aortic valve implantation: a patient-specific finite element approach

Until recently, heart valve failure has been treated adopting open-heart surgical techniques and cardiopulmonary bypass. However, over the last decade, minimally invasive procedures have been developed to avoid high risks associated with conventional open-chest valve replacement techniques. Such a recent and innovative procedure represents an optimal field for conducting investigations through virtual computer-based simulations: in fact, nowadays, computational engineering is widely used to unravel many problems in the biomedical field of cardiovascular mechanics and specifically, minimally invasive procedures. In this study, we investigate a balloon-expandable valve and we propose a novel simulation strategy to reproduce its implantation using computational tools. Focusing on the Edwards SAPIEN valve in particular, we simulate both stent crimping and deployment through balloon inflation. The developed procedure enabled us to obtain the entire prosthetic device virtually implanted in a patient-specific aortic root created by processing medical images; hence, it allows evaluation of postoperative prosthesis performance depending on different factors (e.g. device size and prosthesis placement site). Notably, prosthesis positioning in two different cases (distal and proximal) has been examined in terms of coaptation area, average stress on valve leaflets as well as impact on the aortic root wall. The coaptation area is significantly affected by the positioning strategy ( ? 24%, moving from the proximal to distal) as well as the stress distribution on both the leaflets (+13.5%, from proximal to distal) and the aortic wall ( ? 22%, from proximal to distal). No remarkable variations of the stress state on the stent struts have been obtained in the two investigated cases.     

Expression of matrix metalloproteinase-1 (MMP-1) in Wistar rat's intervertebral disc after experimentally induced scoliotic deformity

Minimally invasive spine surgery is becoming more common in the treatment of adult lumbar degenerative disorders. Minimally invasive techniques have been utilized for multilevel pathology, including adult lumbar degenerative scoliosis. The next logical step is to apply minimally invasive surgical techniques to the treatment of adolescent idiopathic scoliosis (AIS). However, there are significant technical challenges of performing minimally invasive surgery on this patient population. For more than two years, we have been utilizing minimally invasive spine surgery techniques in patients with adolescent idiopathic scoliosis. We have developed the present technique to allow for utilization of all standard reduction maneuvers through three small midline skin incisions. Our technique allows easy passage of contoured rods, placement of pedicle screws without image guidance, and allows adequate facet osteotomy to enable fusion. There are multiple potential advantages of this technique, including: less blood loss, shorter hospital stay, earlier mobilization, and relatively less pain and need for pain medication. The operative time needed to complete this surgery is longer. We feel that a minimally invasive approach, although technically challenging, is a feasible option in patients with adolescent idiopathic scoliosis. Although there are multiple perceived benefits, long term data is needed before it can be recommended for routine use.     

High resolution electrocardiography

Over the past decade, significant advances were made in the research, diagnosis, and treatment of cardiovascular diseases. Such progress was in every sphere of cardiology that includes non-invasive, minimally invasive, and invasive technologies. Interpretive electrocardiography, cardiac pacemakers, cardiac stents, and angioplasty are some areas where the progress has been significant. Non-invasive methods of diagnosis of cardiac disorders involve digital recording of cardiac signals at the body surface (chest) and subsequent computerized analysis. Such methods and instruments provide a vital first step to the diagnosis of the heart without involving surgical procedures. One such non-invasive field is High Resolution Electrocardiography (HRECG). A high-resolution electrocardiogram detects very low amplitude signals in the ventricles called 'Late Potentials' in patients with abnormal heart conditions. A standard electrocardiogram cannot detect these signals. The presence of late potentials is widely accepted to have prognostic significance in patients after Acute Myocardial Infarction (AMI) High Resolution Electrocardiography enhances the diagnostic capabilities of ECGs. This article describes the principles involved in HRECG and the techniques that are employed to derive such superior diagnostic capabilities. The use of these techniques may lead to more discoveries in the causes of cardiac disorders and improved drug discoveries to combat such conditions.     

Reviewing the technological challenges associated with the development of a laparoscopic palpation device

Minimally invasive surgery (MIS) has heralded a revolution in surgical practice, with numerous advantages over open surgery. Nevertheless, it prevents the surgeon from directly touching and manipulating tissue and therefore severely restricts the use of valuable techniques such as palpation. Accordingly a key challenge in MIS is to restore haptic feedback to the surgeon. This paper reviews the state-of-the-art in laparoscopic palpation devices (LPDs) with particular focus on device mechanisms, sensors and data analysis. It concludes by examining the challenges that must be overcome to create effective LPD systems that measure and display haptic information to the surgeon for improved intraoperative assessment.     

Laparoscopic and percutaneous ablative techniques in the treatment of renal cell carcinoma

Widespread use of computed tomography, ultrasound, and magnetic resonance imaging has led to an increase in detection of relatively small renal masses, and approaches to managing them have evolved in the last two decades. Indications for nephron-sparing surgery have expanded, and minimally invasive procedures, which can confer advantages over open surgery, are now available. Ablative techniques offer a combination of nephron-sparing and minimally invasive approaches. Ablative techniques include cryoablation, radiofrequency ablation (RFA), and high-intensity focused ultrasound (HIFU). Cryoablation and RFA have been relatively safe. HIFU has been associated with serious side effects in animal models, and is not yet acceptable for use in humans. Ablative techniques require long-term studies to confirm lasting efficacy. The best modality for tumor targeting, monitoring of therapy, and follow-up is still under investigation. Debate exists regarding the best method for ensuring adequate intraoperative tumor cryoablation. For minimally invasive ablative measures to gain a place as nephron-sparing approaches, they should show both equivalent efficacy and reduced morbidity relative to those of open partial nephrectomy. These techniques should currently be reserved for selected patients and should be compared to the evolving modality of laparoscopic partial nephrectomy.     

Quadrant通道下MIS-TLIF与传统术式治疗单节段腰椎退变性疾病的疗效比较

目的:对比分析Quadrant通道下微创椎间孔椎间融合术(MIS-TLIF)与传统开放经椎间孔椎间融合术(TLIF)治疗单节段腰椎退变性疾病的临床疗效和安全性。方法:选取2012年3月至2015年3月120例我院收治的120例单节段腰椎退变性疾病患者,并将其随机分为对照组和微创(MIS)组,每组各60例。对照组患者给予TLIF治疗,微创组给予MIS-TLIF治疗。观察和比较两组患者的手术情况,手术前后的视觉模拟评分(VAS)、Oswestry功能障碍指数(ODI),肌酸磷酸激酶(CPK)水平、椎间植骨融合率及并发症的发生情况。结果:微创组患者的切口长度、出血量、射线照射时间、下地活动时间以及住院时间均显著低于或短于对照组(P0.05);术后1周、6个月,微创组患者的VAS、ODI评分均显著低于对照组(P0.05);术后,两组患者的CPK水平出现剧烈上升,随后又逐渐下降,但同一时段微创组患者的CPK水平明显低于对照组(P0.05);微创组的椎骨性融合率为93.33%(56/60),显著低于对照组(85.00%,P0.05),且其神经损伤、硬膜囊破裂的发生率均显著低于对照组(P0.05),感染的发生率比较差异无统计学意义(P0.05)。结论:Quadrant通道下微创椎间孔椎间融合术治疗单节段腰椎退变性疾病的临床疗效明显优于传统开放经椎间孔椎间融合术,且创伤更小,患者康复更快,安全性更高。     

A completely detachable aortic clamping instrument for minimally invasive cardiac surgery

A minimally invasive cardiac surgery is becoming more popular and is still undergoing a refinement of surgical techniques and dedicated instrumentarium as well. New specifically designed instruments are quintessence of safe surgery with improving operative outcomes and comfortable operator-oriented working conditions. In this article, we attempt to present our early clinical experience with a new aortic clamping instrument specifically developed for limited single-access minimally invasive valve surgery.     

Rates of cardiac catheterization,coronary angioplasty and open-heart surgery in adults in Canada.

OBJECTIVE: To determine the rates of and waiting lists for cardiac catheterization, percutaneous transluminal coronary angioplasty (PTCA) and open-heart surgery in adults in Canada between Apr. 1, 1988, and Mar. 31, 1989. DESIGN: Mail survey. PARTICIPANTS: The directors of all 48 adult cardiac catheterization laboratories and the chiefs of all 33 adult cardiovascular surgery programs in Canada. MAIN RESULTS: A total of 61,116 cardiac catheterization procedures were performed, a rate of 236 per 100,000 population. The mean waiting times for elective procedures were weighted to reflect more accurately the differences between centres in the number of patients awaiting the procedures. The mean wait for elective cardiac catheterization was 8.5 weeks. There were 10,097 PTCA procedures done, a rate of 39 per 100,000 population. The mean wait for elective PTCA was 11.0 weeks, the longest wait occurring in Quebec (15.4 weeks). A total of 16,240 open-heart procedures were performed, a rate of 63 per 100,000 population. The mean wait for elective open-heart surgery was 22.6 weeks, the longest wait occurring in Quebec and British Columbia (more than 32 weeks). The rates for all three procedures were much lower in Canada than in the United States. CONCLUSIONS: The results suggest that the cumulative wait for coronary angiography and PTCA or open-heart surgery may lead to major losses of productivity, delayed rehabilitation and reduced probability of return to previous levels of productivity. Regular collection of data such as ours should help to understand better the resources required for these specialized cardiac procedures.     

Numerical analysis of an anastomotic device

The explicit dynamic finite element method was utilized to investigate the deformation behaviour of a woven wire mesh tubular device that is used in a side-to-side anastomotic procedure for achieving gastrointestinal anastomosis. The numerical model was initially verified by comparison to experimental results that were obtained using a specialized testing mechanism. Once validated, the finite element model (FEM) was parameterized to ascertain the influence of several device parameters on its deformation behaviour. The importance of these parameters, as related to its optimal design for use in minimally invasive surgery (MIS), was subsequently ascertained and discussed.     

Numerical Analysis of An Anastomotic Device

The explicit dynamic finite element method was utilized to investigate the deformation behaviour of a woven wire mesh tubular device that is used in a side-to-side anastomotic procedure for achieving gastrointestinal anastomosis. The numerical model was initially verified by comparison to experimental results that were obtained using a specialized testing mechanism. Once validated, the finite element model (FEM) was parameterized to ascertain the influence of several device parameters on its deformation behaviour. The importance of these parameters, as related to its optimal design for use in minimally invasive surgery (MIS), was subsequently ascertained and discussed.     

Cannulation of the middle cardiac vein during MICS

Coronary sinus cannulation for retrograde cardioplegia administration during cardiac surgery is common practice. Several of the cannulas that are placed by the cardiac surgeon on open procedures are now placed by the cardiac anesthesiologist during minimally invasive cardiac surgery, including the coronary sinus catheter. The understanding of the cardiac venous anatomy is very important during coronary sinus catheter placement. We present a case where a percutaneously placed coronary sinus catheter was inadvertently placed into the middle cardiac vein but detected with the use of fluoroscopy.     

A Hemodilution Technique for Open-Heart Surgery: A Preliminary Clinical Report

With the extension of open-heart procedures and the increasing success of open-heart surgery, a great strain has been placed on many hospital laboratories and on the Red Cross for the maintenance of equipment and the supply of blood. In order to decrease both of these needs, hemodilution techniques combined with disposable oxygenators have been introduced. The authors have used a disposable oxygenator with low molecular weight dextran prime, along with moderate hypothermia, in a consecutive series of 15 patients operated upon for congenital and acquired heart lesions. In this consecutive series there has been one death and this could not be attributed to the perfusion technique but to the surgical procedure carried out. It is felt that this combination not only broadens the horizons of open-heart surgery but makes the procedure more readily available and safer, as well as being economical of blood donors and time.     

Isolated lung chemotherapeutic infusions for treatment of pulmonary metastases: a pilot study

A pilot study was designed to determine the feasibility of combining minimally invasive surgery techniques and cardiac surgical catheter technology to deliver high-dose unilateral pulmonary chemotherapy. Single lung ventilation general anesthesia was combined with catheter-based left pulmonary artery (PA) control in 4 mongrel dogs. p-Aminohippuric acid (PAH) was used to quantify leakage of pulmonary arterial infusate. Surgical exposure was progressively less invasive. Dissection of cranial and caudal pulmonary veins followed methods used in minimally invasive pulmonary lobectomy. All animals survived the experimental procedure. The Heart-Port Endoplege catheter controlled the canine PA. A volume (50 cm(3)) of infusate much smaller than the calculated pulmonary vascular volume caused less vascular overdistention and diffused throughout the pulmonary vascular bed within 3-5 min as verified by fluoroscopy. 75% of the tracer remained in the lung at the completion of the 30-min dwell time. The pulmonary circulation can be isolated by minimally invasive operative and catheter technology so that the pulmonary parenchyma can be exposed to a high concentration of a compound for at least 30 min in the canine model.     

Design of a multifunctional compliant instrument for minimally invasive surgery

A new multifunctional compliant instrument has been designed for use in minimally invasive surgery. The instrument combines scissors and forceps into a single multifunctional device. The main advantage of using multifunctional instruments for minimally invasive surgery is that instrument exchanges can be reduced, thus reducing procedure time and risk of inadvertent tissue injury during instrument exchanges. In this paper, the length, width, and thickness of the multifunctional compliant mechanism tool tip is optimized to maximize the jaw opening and the grasping force. The optimized design is then modeled to simulate the stresses encountered in the scissors mode. A 5.0 mm diameter stainless steel prototype is fabricated using electro-discharge machining and is shown to grasp and cut successfully.     

痔治疗的临床进展研究

痔是肛肠外科最常见的疾病之一,其治疗方式多种多样,尚无统一治疗标准。虽然,痔在临床上以保守治疗为主,但是对于II度以上有症状的痔,手术仍是目前最主要的治疗方式。关于有症状痔最佳治疗方式的争论仍在继续,无论是非手术治疗、传统的痔切除术还是痔的微创手术,都处于不断的改进和探索之中。临床医生总希望能够找到一项理想的具有复发率低、安全可靠、可早期恢复正常活动、术后疼痛轻微甚至无痛的手术方式。随着手术方式的改进和医疗技术的进步,痔的治疗效果也取得了很大的进步。本文就痔的非手术治疗、有创手术治疗以及微创手术治疗作一综述,为痔的临床治疗提供一定的理论依据。     

不同手术方式对腰椎间盘突出症治疗的效果比较分析

目的:探讨应用微创技术治疗腰椎间盘突出症的疗效.方法:对我院脊柱骨科自2005年l1月～2010年10月收治的128例腰椎间盘突出症患者应用不同手术方式进行治疗,其中应用APLD( automated percutaneous lumbar discectomy)治疗单纯腰椎间盘突出症48例;应用MED(microendoscopic discectomy)治疗复杂型腰椎间盘突出症42例;应用传统后路椎板开窗技术治疗单纯腰椎间盘突出症38例;比较各组手术时间、术中出血、术后住院时间、疗效及并发症.术后均随访8个月～3年,观察复发情况.结果:三组不同手术方式手术时间及优良率比较差异无统计学意义(P＞0.05),APLD及MED组术中出血量及术后住院时间与传统手术组比较,差异有显著性(P＜0.05);术后随访疼痛全部缓解,无复发.结论:在严格掌握适应症的基础上,采用微创技术和采用传统手术治疗腰椎间盘突出症疗效相当,但微创技术创伤小、术中出血量少,术后住院日短,恢复快,优于传统手术.     

高血压脑出血的微创治疗

目的：探讨微创清除颅内血肿技术的手术效果。方法：将42例高血压脑出血的患者,都采用YL-1型一次性使用颅内血肿粉碎穿刺针,进行钻颅手术。结果：16例术后次日即拔针,10例第二日拔针,其余全部患者均在一周内拔针。术后一个月意识恢复良好者27例,重残者10例,死亡5例。结论：谊术式操作时间短,血块及时有效地清除,减轻了副损伤,大大提高了救治成功率。适合广大基层医院使用。     

Cosmetic medicine: facial resurfacing and injectables

LEARNING OBJECTIVES: After studying this article, the participant should be able to: 1. Describe the most common options available for minimally invasive facial rejuvenation. 2. Identify key elements essential to each treatment option. 3. Know how to avoid and manage complications for these procedures. SUMMARY: Minimally invasive cosmetic procedures continue to increase in popularity. This article is intended to provide a broad and practical overview of common minimally invasive cosmetic techniques available to the plastic surgeon.     

Optoelectronic display system for minimal invasive laparoscopic operations: initial experiences with new face-mounted display video eyeglasses]

A major aspect of efforts to improve minimally invasive surgery is the optimization of visualization, which is currently unsatisfactory due to the limited number of pixels in the monitors used, and inadequate alignment of the optical axis. Optical systems provided with commercially available head-mounted displays have failed to improve optical quality and significantly facilitate or improve laparoscopic surgery [2,3]. Innovations in the field of consumer video using a new optical prism and a high-resolution matrix (180,000 pixels) are the core elements of a new face-mounted display (FMD-Eye-Trek 700, Olympus Optical Co, Europe GmbH, Hamburg, Germany) that provides high image quality. This device has now been tested for the first time during laparoscopic procedures (n = 14) and combined laparoscopic-endoscopic procedures (n = 7) under clinical conditions. Impressive optical, ergonomic and surgeon-related benefits were established.     

Changing patterns in iatrogenic ureteral injuries

Advances in laparoscopic and endoscopic surgery over the past 25 years have changed the preferred methods for performing many operations. We previously reported an increase in the number of patients treated for ureteral injury at our institution that paralleled the introduction of minimally invasive techniques. Since that report, more advanced endoscopic procedures have been introduced. We sought to determine whether the latter influenced the number of ureteral injuries managed at our institution. Reported here are the results of our retrospective study, which sought to determine if the rate of treatment of major iatrogenic ureteral injuries has changed.