A numerical investigation to evaluate the washout of blood compartments in a total artificial heart

Total artificial heart (TAH) represents the only valid alternative to heart transplantation, whose number is continuously increasing in recent years. The TAH used in this work, is a biventricular pulsatile, electrically powered, hydraulically actuated flow pump with all components embodied in a single device. One of the major issues for TAHs is the washout capability of the device, strictly correlated with the presence of blood stagnation sites. The aim of this work was to develop a numerical methodology to study the washout coupled with the fluid dynamics evaluation of a total artificial heart under nominal working conditions. The first part of this study focussed on the CT scan analysis of the hybrid membrane kinematics during TAH operation, which was replicated with a fluid-structure interaction simulation in the second part. The difference in percentage between the in vitro and in silico flow rates and stroke volume is 9.7% and 6.3%, respectively. An injection of contrast blood was simulated, and a good washout performance was observed and quantified with the volume fraction of the contrast blood still in the ventricle. The left chamber of the device showed a superior washout performance, with a contrast volume still inside the device after four washout cycles of 6.2%, with the right chamber showing 15%.     

Device for accurately siting the acetabular component during total hip replacement

INTRODUCTION: In this paper we describe a device which allows consistent acetabular cup placement to reduce post-arthroplasty dislocation. PATIENTS AND METHODS: The development of this surgical appliance is traced from the initial concept to the construction of a device suitable for clinical trials. The system of use is explained. The constraints imposed by the working environment and the methods employed to meet the demands imposed by surgical practice are elucidated. A clinical trial is described in which the device was used to assist in siting acetabular cup placement in ten patients. RESULTS: The accuracy of the ten cup placements done using the device was then compared by radiography with the accuracy of placement of 17 acetabular cups performed in the standard manner. Comparison of the results show a positive benefit arising from using the device. CONCLUSIONS: Our initial good results on cup positioning in laboratory studies are maintained in a clinical setting, but further modifications could lend to even better results.     

Efficacy of dretler stone cone in the treatment of ureteral stones with pneumatic lithotripsy

INTRODUCTION: Ureteroscopic pneumatic lithotripsy has been used to treat ureteral calculi for more than 10 years. Owing to its low price and high degree of effectiveness, it has become the most popular ureteroscopic lithotripsy device in use worldwide. The major limitation of the technique is the occurrence of proximal fragment migration during intracorporeal lithotripsy. The Dretler Stone Cone is a new device developed to prevent stone migration during ureteroscopic lithotripsy. The aim of this study was to assess the efficacy and safety of this device during ureteroscopic pneumatic lithotripsy. PATIENTS AND METHODS: Twenty-three consecutive patients having ureteral stones were treated with a 10-Fr semirigid ureteroscope, a Stone Cone Nitinol Retrieval Device, and a pneumatic lithotriptor. In all patients Stone Cones were placed under visual guidance through the working channel of the ureteroscope. Outcomes of this device were then compared with the outcomes of 23 previous patients with stones of similar sizes and locations who had undergone ureteroscopic pneumatic lithotripsy prior to the Stone Cone being available at our clinic. RESULTS: All patients in the study group were stone-free after the procedure. No stone fragments were noted to migrate to proximal segments. CONCLUSIONS: The Dretler Stone Cone effectively prevents proximal stone migration and facilitates stone fragmentation during pneumatic lithotripsy with no risk of ureteral injury. It has only a small extra cost.     

Caring for Patients With Ventricular Assist Devices: A Mini-Review of the Literature

Heart transplantation, one of the treatment options for end-stage heart failure, is still regarded as the gold standard treatment to improve quality and length of life. However, the rapid increase in the number of patients waiting for heart transplantation and the inadequate number of donors makes heart transplantation a less feasible option and increases the need for ventricular assist devices as an alternative. The success of ventricular assist device implantation requires the collaboration of a multidisciplinary team consisting of cardiac surgeons, nurses, ventricular assist device coordinators, cardiologist, cardiac anesthesia specialists, perfusionists, and physiotherapists. Nurses working in different fields such as intensive care units, operating rooms, outpatient clinics, and ventricular assist device coordination units have important responsibilities in multidisciplinary teams. In this study, national and international studies on the responsibilities of nurses for the management and care of ventricular assist devices were reviewed. Nurses undertake many tasks, especially in the postoperative care of patients and in preparing them for discharge. Important responsibilities of nurses in the care of patients with ventricular assist devices include monitoring complications, managing equipment and emergency situations, establishing dressing change protocols, organizing daily life activities, determining rehabilitation needs, ensuring use of medicines, and providing comprehensive discharge education. Organizational and communication skills of nurses working with multidisciplinary teams are very important for the success of the ventricular assist device implantation process.     

Magnetic propulsion and ultrasound tracking of endovascular devices

In this paper a robotic means of magnetic navigation of an endovascular device a few millimeters in diameter is presented. The technique, based on traditional computer-assisted surgery adapted to intravascular medical procedures, includes a manipulator for magnetic dragging interfaced with an ultrasound system for tracking the endovascular device. The main factors affecting device propulsion are theoretically analyzed, including magnetic forces, fluidic forces, and friction forces between the endovascular device and the vessel. A dedicated set-up for measuring locomotion, and for navigation with and against the flow, has been developed and preliminary tests have been performed to derive the best configuration for controlled magnetic dragging in the vascular system. Experimental outcomes are consistent with a simple analytical model that analyzes dragging of the magnetic capsule in a tube. By means of this model, different working conditions can be considered to select the appropriate conditions, for example flow rate, coefficient of friction, or magnetic properties.     

一种新型输尿管管路封堵器在输尿管镜钬激光碎石术中的应用初探

目的：研究英诺伟TMIVX-SCIO输尿管管路封堵器在输尿管镜钬激光碎石术中的临床疗效并评价其安全性。方法：对23例单侧输尿管结石患者于输尿管镜工作通道内安置英诺伟TMIVX—SCIO输尿管管路封堵器,完全超越结石后操作体外手柄使叶片折叠成球状防止结石上移,而后使用钬激光碎石,并使用封堵器叶片折叠球将结石碎片拖出输尿管开口。所有患者术后留置双J管两周。结果：1例息肉包裹的肾盂一输尿管连接处结石于安置输尿管管路封堵器前出现结石漂移至患侧肾下盏,改用输尿管软镜以钬激光碎石。术中无患者出现输尿管穿孔或输尿管黏膜撕脱。术后无患者出现发热及菌血症。术后4周影像学随访,除1例结石漂移入肾下盏的患者结石尚未排空外,余22例无明显结石残留,结石清除率为95．7％。结论：输尿管管路封堵器能显著减少输尿管碎石术中结石漂移、提高结石清除率,临床应用价值高、治疗成本低且使用安全,对于输尿管上段结石尤其适用,可望成为输尿管镜手术中重要附属器械之一。     

可拆卸式管路封堵器联合输尿管镜双频双脉冲Nd∶YAG激光治疗输尿管结石200例报告

目的 评估英诺伟可拆卸式TMIVX-SC07输尿管管路封堵器在输尿管镜U-100双频双脉冲Nd∶ YAG碎石术中的安全性和拦截碎石效果.方法 对200例单侧输尿管结石患者于Wolf F6/7.5输尿管镜工作通道内安置可拆卸式英诺伟TMIVX-SC07管路封堵器.完全超越结石后操作体外手柄使叶片折叠成球状防止结石上移,拆卸手柄并退出输尿管镜后重新进境,将封堵器置于输尿管镜外尾部重新固定,而后使用激光碎石至小于2mm结石碎屑,然后使用封堵器叶片折叠球将结石碎片拖带出输尿管开口.所有患者术后留置F6双J管2～4周.结果 16例中重度积水的输尿管上段结石安置输尿管管路封堵器碎石后部分结石漂移至患侧肾内,2周后改用体外冲击波碎石或二期输尿管软镜碎石.术中无患者出现输尿管穿孔或输尿管黏膜撕脱.术后4周予腹部平片和B超等影像学随访,其中184例结石完全排除,结石清除率为92.0％.结论 可拆卸式输尿管管路封堵器联合双频双脉冲Nd∶ YAG激光能显著减少输尿管碎石术中结石漂移,提高结石清除率,手术安全性更高,有良好的应用前景.     

Interface corrective force measurements in Boston brace treatment

Brace application has been reported to be effective in treating idiopathic adolescent scoliosis. The exact working mechanism of a thoracolumbo spinal orthosis is a result of different mechanisms and is not completely understood. One of the supposed working mechanisms is a direct compressive force working through the brace upon the body and thereby correcting the scoliotic deformity, achieving optimal fit of the individual orthosis. In this study we measured these direct forces exerted by the pads in a Boston brace in 16 patients with idiopathic adolescent scoliosis, using the electronic PEDAR measuring device (Novel, Munich, Germany). This is designed as an in-shoe measuring system consisting of two shoe insoles (size 8 1/2), wired to a computer, recording static and dynamic pressure distribution under the plantar surface of the foot. After positioning the inserts between the lumbar and thoracic pads and the body, we measured the forces acting upon the body in eight different postures. In all positions the mean corrective force through the lumbar brace pad was larger than the mean corrective force over the thoracic brace pad. Some changes in body posture resulted in statistically significant alterations in the exerted forces. There was no significant correlation between the magnitude of the compressive force over the lumbar and thoracic brace-pad and the degree of correction of the major curve. Comparing the corrective forces in a relatively new (<6 months) and old (>6 months) brace, there was no statistically relevant difference, although the corrective force was slightly larger in the new braces. We think that the use of this pressure measurement device is practicable and of value for studies of the working mechanism of brace treatment, and in the future it might be of help in achieving optimal fit of the individual orthosis.     

Biochemical and Functional Correlates of Myocardium-Like Transformed Skeletal Muscle as a Power Source for Cardiac Assist Devices

Skeletal muscles, such as the latissimus dorsi muscle, can be transformed to gain considerable fatigue resistance to be suitable either for cardiomyoplasty, or to power a cardiac assist device. Such transformation of the skeletal muscle can be achieved by low frequency electrical stimulation for several weeks. In this article, we reviewed the stimulation protocol, and subsequent histochemical, biochemical, and functional changes in the skeletal muscle, and compared them to those of the cardiac muscle. The parameters that should be useful for stimulating such a muscle to assist the heart are defined. The issues currently under study, including the optimal transformation parameters, the feasibility of working transformation, and the importance of device design to minimize vascular compromise of the muscle, are also discussed. It is concluded that there is a great potential to use the plasticity of skeletal muscle for clinical purposes, specifically by transforming the skeletal muscle to resemble the myocardium in order to use it either to replace or repair the myocardium, or as the endogenous power source for a cardiac assist device.     

Experiences with an artificial sphincter to establish anal continence in dogs

An implantable device for establishing urinary continence has been developed and has received FDA approval (AS 800, American Medical Systems, Inc.). The authors have applied this device to the control of anal continence in dogs. Fifteen mongrel dogs underwent either anal sphincter disruption (7) or abdominal-perineal resection (8). Such animals have bowel movements almost hourly. In each case, the device was implanted at the time of surgery. In dogs with working cuffs and disabled or absent sphincters, continence was maintained in seven out of 15 animals for periods of 4-8 hours. After cuff activation, intraluminal cuff pressures of 50-70 cm of water achieved continence for a period of 8 hours. In animals sacrificed from 1 to 12 months after implantation, the device was found to be well tolerated by the body with minimal fibrosis of the mucosa or muscularis of the bowel. Complications observed in the same four out of 15 animals during the study period were infection, device extrusion, and device malfunction. Infection resolved with local wound care and antibiotics (3/4) and the device was successfully replaced in two out of four instances of extrusion. With cuffs of proper size and pressure, this appliance may be effective in the control of human anal incontinence via the establishment of continent perineal colostomies following an abdominal-perineal resection.     

A Two-Phase Fluid Volume Compensation Chamber for an Electric Ventricular Assist Device

A volume compensation chamber is a device used to reduce large pressure fluctuations created in electric ventricular assist devices during the emptying and filling of the blood sac. In this study, the effect of motor casing pressure variation (pressure swing) on the performance of the Penn State electric ventricular assist device (EVAD) was investigated. Design criteria were established for the maximum pressure swing tolerated by the EVAD and the optimal mean chamber pressure at which to operate. At the chosen mean chamber pressure of -15 mm Hg, it was found that pressure swing should be maintained below 45 mm Hg. A two-phase fluid volume compensation chamber was developed that reduced the pressure swing enough to ensure adequate pump performance. The device consists of a metal chamber with a high-heat-flux porous coating applied to the inside surface. The chamber uses Freon as the working fluid and is isolated from the EVAD by a metal bellows. It was found that the high-flux coating significantly reduces the pressure swing, in some cases by as much as 50% when compared with an identical chamber with no coating. In the coated chamber the pressure swing was maintained between 22 and 30 mm Hg at a beat rate of 60 beats/min, for a wide range of Freon volumes (4-38 ml). Even at 100 beats/min the pressure swings obtained with the coated chamber are well within an acceptable range.     

Extraoral vs. intraoral distraction osteogenesis in the treatment of hemifacial microsomia

During hemifacial microsomia (HMF), an important phase of the treatment is elongation of the hypoplastic mandible, mainly the ramus, at an early stage. Twenty-two patients with HFM were treated with distraction osteogenesis: 12 with an extraoral device (10 unidirectional and 2 multidirectional) and 10 with an intraoral device. The mean elongation with the extraoral device was 21 mm, and with the intraoral device was 17 mm, resulting in a more symmetrical facial appearance. The advantages and disadvantages of both methods are presented, based on the authors' experience and a review of the literature. The extraoral device permits elongation of a greater distance, enables extraoral control of the vector of elongation, and conserves the gonial angle by working in many directions. The main disadvantages of the extraoral device are the social inconvenience to the patient and the extraoral cutaneous scars. Conversely, the intraoral device is much more socially convenient to the patient and avoids residual scarring. However, in 2 patients treated with an intraoral device, an undesired contralateral open bite appeared as a result of reduced vector control. The intraoral method should always be considered first because of its previously mentioned advantages. However, in severely hypoplastic patients, when three-dimensional correction and gonial angle control are necessary, or when there is a limited space along the planned distracted bone, the extraoral device has an advantage over the intraoral device.     

A camera handler for Miccoli’s minimally invasive video-assisted thyroidectomy and paratiroidectomy procedures

Background Minimally invasive video-assisted thyroidectomy and paratiroidectomy (MIVAT/P) are surgical procedures performed with 5-mm cameras handled by a camera assistant. Methods The authors created a new camera handler for video-assisted neck surgery. It consists of a telescopic tripod device designed for mechanical handling of the camera, which is directly oriented by the operator even in solo surgery procedures. The camera is placed inside an O-shaped support, and moved by the operator himself for exploration and work on the surgical field. Results Thanks to this simple device, the camera holder provides a firm field and prevents blood stains in limited working spaces. Conclusions The novel camera handler may be useful in either MIVAT/P or other simple laparoscopic procedures (i.e., cholecystectomy) for a steady handling of the camera, even in solo surgery procedures.     

Appliance of the authors' own concept of the leg support device in the pelvic, hip, thigh operation]

The aim of this study is to present the authors' own concept of the leg support device which facilitates stable positioning in a lateral position with the possibility of a controlled leg abduction in the pelvic, hip and thigh operation. The appliance of this device is a very good and cheap alternative of positioning patients in the hip operation in comparison with the improvised lateral position. As far as the operated leg is concerned the advantages of this device include: stable leg positioning, possibility of controlling the length of the leg, possibility of changing the leg position. The use of this device also reduces the number of medical staff assisting during the operation. Furthermore, this device prevents putting physical pressure on the leg that is not being operated. The experience of using this device for the last few years has proved its numerous advantages.     

A suture-retaining spring device to assist in microvascular procedures

Microvascular anastomosis needs a skilled assistant. A simple spring device subtracts this need. This device is an “add-on” to the conventional vascular clamp. It helps the surgeon to perform the anastomosis alone by lifting up the anterior wall away from the posterior wall. It allows hitching of the sutures throughout the circumference of the vessel, which is not possible with an Acland clamp (can only hitch sutures at 180°). This also helps in the accurate placement of sutures and allows clear vision of the lumen without compromising vision or working space.     

The validity and reliability of the Klaue device

BACKGROUND: Excessive first ray mobility has been implicated as the cause of many forefoot abnormalities. The association between hypermobility and forefoot pathology is controversial, and this is largely related to the difficulty in quantifying first ray motion. Manual examinations have been shown to be unreliable. Klaue etal. developed a device consisting of a modified ankle-foot orthosis with an attached micrometer to objectively measure first ray mobility. The purpose of this study was to evaluate the validity and reliability of this device. METHODS: Sixteen fresh-frozen, below-knee amputation specimens with hallux valgus were used for the study. The study was divided into two parts. Part I was an analysis of the validity of the Klaue device; first ray dorsal displacement was measured on lateral radiographs following manual manipulation, and values were statistically compared to the Klaue device measurements. Part II of the study was an evaluation of intraobserver and interobserver agreement. Two clinicians used the Klaue device on each of the cadaver limbs, and values of first ray sagittal mobility were recorded and compared. RESULTS: The mean value of first ray mobility measured with the Klaue device was 7.5 mm and the average displacement measured from the lateral radiographs was 7.4 mm. Paired t-testing showed no significant difference between the Klaue and radiographic measurements (p = 0.83). The mean first ray mobility by examiners 1 and 2 with the Klaue device were identical (10.5 mm), and statistical analysis showed no significant interobserver or intraobserver differences. CONCLUSIONS: The results confirm the validity of the Klaue device and limited variability of measurements between experienced users.     

Comparison of Peditrol irrigation device and common methods of irrigation

BACKGROUND AND PURPOSE: The Peditrol is a novel hands-free irrigation device that delivers a bolus of irrigant through the ureteroscope when the foot pedal is deployed. The purpose of this study was to compare the flow and pressures created by the Peditrol with those of commonly used methods of irrigation. MATERIALS AND METHODS: Flows through a flexible 6.9F Olympus ureteroscope (F-URS) and a 7.5F semirigid ACMI ureteroscope (S-URS) were measured in duplicate with the working channel empty and with a 2.2F Nitinol basket or a laser fiber in the working port. Irrigant flow was pressurized by gravity drainage at 100 cm H(2)O (GI), pressurized irrigant bag at 300 cm H(2)O (PI), handheld 60-cc syringe (HS), and the Peditrol. A 20-gauge angiocatheter was placed through the parenchyma into the renal pelvis of an ex-vivo cadaveric porcine kidney and attached to a pressure transducer. Pressures were measured in triplicate using the same irrigation techniques. RESULTS: With a basket or 200-microm laser fiber in the working port of the F-URS, Peditrol mean flows were superior to those of PI (3.3 and 6.3 times, respectively; P < 0.001) but similar to those of HS (0.7 to 1.1 times). All irrigation types resulted in intrarenal pressures greater than gravity irrigation (P < 0.05). The Peditrol demonstrated intrapelvic pressures <40 cm H(2)O when used with a 12/14F ureteral access sheath (AS). Without an AS, the intrapelvic pressure reached 92 cm H(2)O, similar to the pressures reached with the S-URS under various irrigation conditions (84-287 cm H(2)O) and comparable to the HS method through the F-URS (97 cm H(2)O). CONCLUSIONS: The Peditrol irrigation device generates superior flow through an F-URS compared with GI or PI, particularly with an instrument in the working port. Intrarenal pressures when used with an F-URS and AS are low. When an AS is not used, the intrarenal pressure is similar to or lower than pressures obtained using an S-URS with different irrigation modalities.     

Scalp marking for a craniotomy using a laser pointer during preoperative computed tomographic imaging: technical note

OBJECTIVE: The preoperative localization of superficial intracranial lesions is often necessary for accurate burr hole placement or craniotomy siting. It is not always easy, however, to localize the lesions over the scalp working only from computed tomographic images. We developed a simple method for such localization using a laser pointer during the preoperative computed tomographic examination. METHODS: The angle of incidence, extending from a point on the scalp to the center of the computed tomographic image, is measured by the software included with the scanner. In the gantry, at the same angle as on the image, a laser is beamed from a handmade projector onto the patient's scalp toward the center of the gantry. The point illuminated on the patient's head corresponds to that on the image. The device and the method are described in detail herein. RESULTS: We applied this technique to mark the area for the craniotomy before surgery in five patients with superficial brain tumors. At the time of surgery, it was confirmed that the tumors were circumscribed precisely. CONCLUSION: The technique is easy to perform and useful in the preoperative planning for a craniotomy. In addition, the device is easily constructed and inexpensive.     

Developments in neuroendoscopy: trial of a miniature rigid endoscope with a multidirectional steerable tip camera in the anatomical lab

The aim of this study is to assess field of view, usability and applicability of a rigid, multidirectional steerable video endoscope (EndActive) in various intracranial regions relevant to neurosurgical practice. In four cadaveric specimens, frontolateral, pterional, transnasal (to sella and clivus), interhemispheric (transcallosal and retrocallosal) and retrosigmoid approaches as well as precoronal burr holes for ventriculoscopy were performed. Anatomical target structures were defined in each region. We assessed field of view as well as optical and ergonomic features of the prototype. The EndActive is a 4-mm-diameter rigid video (endo)scope with an integral image sensor comprising an embedded light source. The viewing direction in a range of 160° can either be controlled by the computer keyboard or a four-way joystick mounted to the handle section of the endoscope. The endoscopic imaging system allows the operator to simultaneously see both a 160° wide-angle view of the site and an inset of a specific region of interest. The surgeon can hold the device like a microsurgical instrument in one hand and control movements precisely due to its reduced weight and ergonomic shape. The multiplanar variable-view rigid endoscope proved to be useful for following anatomical structures (cranial nerves I–XII). The device is effective in narrow working spaces where movements jeopardize the delicate surrounding structures. The multiplanar variable viewing mechanism in a compact device offers advantages in terms of safety and ergonomics. Improving the usability will probably optimize the applicability of endoscopic techniques in neurosurgery.     

Effects of postischemic left ventricular pressure-volume unloading on contractile recovery and myocardial blood flow in the regionally stunned canine heart.

OBJECTIVE: Myocardial stunning remains a clinical problem without definitive therapy. This study tested the hypothesis that mechanical therapy with a ventricular assist device would accelerate recovery of contractility in stunned myocardium by increasing the postischemic myocardial blood flow. METHODS: Regional stunning was induced in dogs (25 kg) by 15 minutes of coronary occlusion and 180 minutes of reperfusion. One group (ventricular assist device; n = 10) was reperfused in conjunction with left ventricular unloading with a centrifugal-pump ventricular assist device. A second group (control; n = 8) underwent unmodified reperfusion. Hemodynamic and regional function data were acquired in all dogs with the heart in the working state before and during ischemia and after 180 minutes of reperfusion. Regional myocardial blood flow was measured at these same intervals and after 30 minutes of reperfusion, at which time the left ventricle was mechanically unloaded in animals with a ventricular assist device. RESULTS: Regional stunning was observed in all animals, but cardiogenic shock developed in none of them. After 180 minutes of reperfusion, animals with a ventricular assist device had greater systolic shortening in the risk segment than did control animals (11.5% +/- 2.8% vs 1.1% +/- 1.3%; P <.05) and had no differences in either the slope or x-axis intercept of regional preload recruitable stroke work relations compared with preischemic values. Differences in contractile recovery did not correlate, however, with postischemic myocardial blood flow. Hyperperfusion mediated by the ventricular assist device was not observed in either stunned or remote segments. CONCLUSIONS: Mechanical left ventricular unloading attenuates regional myocardial stunning within 3 hours in normotensive dogs, independent of effects on myocardial blood flow. The mechanism underlying this effect remains undefined, but these data support expanded use of mechanical therapy for stunned myocardium in clinical settings.