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At least 649 records · Page 36Linked to original sources
PubMed1984

Plate osteosynthesis in posttraumatic deformities of the femoral shaft.

The success of precisely indicated surgical treatment of posttraumatic deformities of the femur shaft depends on painstaking preoperative planning with exact assessment of the locus of correction, careful determination of the correction angle, and choice of an adequate operation method. In correction operations plate osteosynthesis is necessary, in contrast to the various possibilities for care of primary fractures of the femur. Therefore we concentrate in this paper mainly on the use of plate osteosynthesis, without forgetting that there are also indications for intramedullary nailing, especially of not yet consolidated fractures or aseptic wound healing impairments. Long X-rays of the leg are an essential part of the preoperative preparation. The success of all operative treatments does not depend only on the degree of disablement, the age of the patient, and realistic target. Particularly in view of the difficulty of plate osteosynthesis and the variety of methods of primary osteosynthesis, the surgeon has to consider the rules of biomechanics as they apply to the incorrectly set femur and to simulate the surgical treatment with preoperative planning in order to attain physiological axial conditions with the best operative method. This applies particularly to the knee joint. Axial deformities are very often combined with shortening, and surgical correction is therefore sometimes difficult.

Adolescent↗
PubMed1993

Three-dimensional simulation of Harrington distraction instrumentation for surgical correction of scoliosis.

Harrington distraction rod surgery on six female patients with idiopathic scoliosis was simulated in three-dimensional osseoligamentous finite element models with individual geometry taken from preoperative stereo roentgenographic reconstructions of the spine and ribcage and compared with the measured outcome. Boundary conditions at the ends of the spine were used to maintain pelvis and head alignment. Published material and flexibility properties were used. The amount of hook distraction was calculated from measured changes in the distance between the hook sites (range, 13-27 mm). Initial simulations underestimated the Cobb angle correction by an average 6%. They underestimated the spinal elongation by 36% and predicted an average 12 degrees increase in kyphosis angle compared with an actual 10 degrees average decrease. Agreement for sagittal plane changes improved in five cases when the beams representing the motion segments were displaced posteriorly. In the sixth case (with the rod applied over a lordotic spinal region), agreement was improved with the motion segment beams displaced anteriorly. The amount of the beam displacement that gave the best agreement was variable, and we were not able to predict it for each individual. Both measured and simulated changes in vertebral transverse plane rotations and in rib angulations were small. The greatest source of errors in these simulations appeared to be inadequate representation of in vivo motion segment behavior by in vitro measured stiffness properties.

Adolescent↗
PubMed1992

Injury in nonischemic lung after unilateral pulmonary ischemia with reperfusion.

We developed an in vivo intact canine model to study pulmonary ischemia-reperfusion (IR) injury. The surgical approach simulates that of unilateral lung transplantation but is free of technical difficulties and other factors related to lung preservation. Serial measurements of regional pulmonary blood flow (rPBF), extravascular density (EVD), and transcapillary protein flux were made with the quantitative imaging technique of positron emission tomography. Eleven experimental and six control animals were studied. After 2 h of warm ischemia followed by reperfusion, no significant change occurred in rPBF despite significantly increased EVD, which was greater on the ischemic than on the nonischemic side. Protein flux, measured as a rate constant, was also greater on the ischemic than on the nonischemic side (median 181 x 10(-4)/min, range 104-619, vs. median 90, range 33-132) immediately after reperfusion. Both sides were also significantly different from control values (median 37, range 21-57). On both sides, protein flux decreased over time and at 5 h after reperfusion was not different from that of controls. Data from the control animals showed that these findings in the experimental animals were not due to surgical technique, deterioration in the surgical preparation, or hyperperfusion of the nonischemic lung. Thus IR injury of one lung can lead to similar, but less severe, injury in the contralateral lung. Because injury in the nonischemic lung develops only after reperfusion of the ischemic lung, injury to the nonischemic lung is probably humorally mediated. The model is a useful and relevant method for studying the physiological consequences of pulmonary IR injury.

Animals↗
PubMed2004

Development of hybrid integrated endoscope-holder system for endoscopic microneurosurgery.

OBJECTIVE: Endoscopic techniques in the field of neurosurgery are under development. To perform sophisticated bimanual procedures in the delicate surgical fields of neurosurgery, rigid endoscope fixation devices with accurate locking and a safe releasing system are required. Here, we report the development of a new hybrid integrated endoscope-holder system. INSTRUMENTATION: The basic concepts of the holding device were as follows: 1) it should combine both video system and holding device; 2) it should have easy maneuverability and accurate fixation and be equipped with a safe releasing mechanism; and 3) it should be able to be used universally either in a primary or an assisting endoscopic procedure. A negatively actuated air-locking system and a bayonet-shaped endoscope were newly developed. Clinical trials of 25 patients were performed, and each prototype was tested and modified until the functional requirements were fulfilled. The final version was tested for accuracy and security in fixation and releasing mechanism. RESULTS: Eight problems were encountered in the clinical trials and improved. Accuracy in fixation of the final version was superior to the most advanced endoscope-holder on the market. No dangerous events were observed during repetitive insertion, fixation, and release in the simulated deep surgical field in the cadaveric skull. No apparent complications were noted in the clinical application. CONCLUSION: We have developed a highly reliable, accurately fixable, and easily maneuverable hybrid endoscope-holder system. To achieve a safer, more accurate, and less invasive surgery in the current socioeconomic demands, commercial manufacturers and surgeons in multiple centers need to combine their efforts to create useful techniques.

Adult↗
PubMed2000

Algorithms for the computer modelling of mechanical interactions with soft tissue.

The computer modelling of soft tissue has applications in the simulation of surgical procedures, product design, and in CAD generally as well as in motion pictures. We begin by reviewing computer modelling techniques in a range of applications. Algorithms are described to predict where surfaces interact mechanically, aiming as far as possible to use geometric modelling methods available within high level CAD systems. After an initial 2-Dimensional evaluation, 3-dimensional surfaces were used throughout. A model was developed to predict the region of impact of two surfaces in an environment of many surface patches. We report the results of this modelling and the application of refinement algorithms to reduce the computation requirements. We then go on to discuss the applicability of this work in the modelling of the deformation behaviour of soft tissues.

Algorithms↗
PubMed2004

Particle-hemodynamics simulations and design options for surgical reconstruction of diseased carotid artery bifurcations.

Based on the hypothesis that aggravating hemodynamic factors play a key role in the onset of arterial diseases, the methodology of "virtual prototyping" of branching blood vessels was applied to diseased external carotid artery (ECA) segments. The goals were to understand the underlying particle-hemodynamics and to provide various geometric design options for improved surgical reconstruction based on the minimization of critical hemodynamic wall parameters (HWPs). First, a representative carotid artery bifurcation (CAB) and then CABs with stenosed ECAs, i.e., a distally occluded ECA and an ECA stump, were analyzed based on transient three-dimensional blood flow solutions, employing a user-enhanced commercial finite volume code. Specifically, the HWPs, i.e., oscillatory shear index, wall shear stress angle gradient, near-wall residence time of monocytes, and near-wall helicity angle difference were evaluated to compare the merits of each design option, including a reconstructed near-optimal junction which generates the lowest HWP-values. The results provide physical insight to the biofluid dynamics of branching blood vessels and guide vascular surgeons as well as stent manufacturers towards interventions leading to high sustained patency rates.

Blood Flow Velocity↗
PubMed2001

Noninvasive vasectomy using a focused ultrasound clip: thermal measurements and simulations.

INTRODUCTION: Conventional surgical vasectomy may lead to complications including bleeding, infection, and scrotal pain. Noninvasive transcutaneous delivery of therapeutic focused ultrasound has previously been shown to thermally occlude the vas deferens. However, skin burns and inconsistent vas occlusion have presented complications. This study uses bio-heat transfer simulations and thermocouple measurements to determine the optimal ablation dosimetry for vas occlusion without skin burns. METHODS: A 2-rad ultrasound transducer mounted on a vasectomy-clip-delivered ultrasound energy at 4 MHz to the canine vas deferens co-located at the focus between the clip jaws. Chilled degassed water was circulated through an attached latex balloon, providing efficient ultrasound coupling into the tissue and active skin cooling to prevent skin burns. Thermocouples placed at the vas, intradermal, and skin surface locations recorded temperatures during ablation. Procedures were performed with transducer acoustic powers of 3-7 W and sonication times of 60-120 s on both the left and right vas deferens (n = 2) in a total of four dogs (precooling control, 3 W/120 s, 5 W/90 s, 7 W/60 s). Measurements were compared with bio-heat transfer simulations modeling the effects of variations in power and sonication time on tissue temperatures and coagulation zones. RESULTS: Active skin cooling produces a thermal gradient in the tissue during ablation, allowing sufficient thermal doses to be delivered to the vas without skin burns. However, low-power, long-duration heating produced excessive tissue necrosis due to thermal diffusion, while high power and short heating times reduced the therapeutic window and produced skin burns presumably due to direct ultrasound absorption. CONCLUSIONS: Both simulations and experiments suggest that a therapeutic window exists in which thermal occlusion of the vas may be achieved without the formation of skin burns in the canine model (power = 5-7 W, surface intensity = 1.4-1.9 W/cm2, time = 20-50 s). This range of ablation parameters will help guide future experiments to refine incisionless vasectomy using focused ultrasound.

Animals↗
PubMed2002

Modern parathyroid surgery: a cost-benefit analysis of localizing strategies.

HYPOTHESIS: Preoperative and intraoperative localizing techniques are more cost-effective than a nondirected bilateral neck exploration in the initial treatment of primary hyperparathyroidism (HPT). DESIGN: A clinical outcome model was developed to simulate the surgical management of primary HPT. Clinical scenarios modeled included a nondirected bilateral neck exploration and surgery using the following localizing strategies: preoperative technetium Tc 99m sestamibi scanning, intraoperative "quick" intact parathyroid hormone assay, or intraoperative radioguidance. Average total charges based on intent to treat were estimated from our practice and from the literature. MAIN OUTCOME MEASURES: Average total charges per patient (for the primary operation and for reexploration for persistent HPT, if needed), incidence of surgical failure (ie, persistent HPT), and risk of recurrent laryngeal nerve injury (cumulative risk of the primary procedure and a subsequent operation for persistent HPT). RESULTS: The use of any localizing strategy reduced total charges, risk of persistent HPT, and cumulative risk of recurrent laryngeal nerve injury compared with a nondirected bilateral neck exploration. The greatest cost savings and the lowest risk of recurrent laryngeal nerve injury were achieved when technetium Tc 99m sestamibi scanning was combined with intraoperative radioguidance. The lowest rate of persistent HPT was found when technetium Tc 99m sestamibi scanning was combined with an intraoperative parathyroid hormone assay. CONCLUSIONS: Limited parathyroid surgery using any localizing strategy is cost-effective, safe, and efficacious in the management of primary HPT. The cost benefit was primarily achieved by reduced operative charges and immediate hospital discharge rather than a lower need for reexploration for persistent HPT.

Cost Savings↗
PubMed1983

Nonspecific stimulation of host defenses against bacterial challenge in immunosuppressed mice.

Muramyl dipeptide (MDP) has been shown to be a safe and effective host defense stimulant in both normal and malnourished hosts exposed to a bacterial challenge. We investigated its effect in mice compromised by pretreatment with either cyclophosphamide or steroids. The bacterial challenge, designed to simulate a surgical wound infection, consisted of a Klebsiella pneumoniae-laden suture. The MDP treatment resulted in lower local and systemic bacterial spread and increased survival in mice immunosuppressed by cyclophosphamide than in untreated controls. No such effect was demonstrated in animals compromised by steroids. These results suggest that MDP exerts its effect primarily on the macrophage.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1982

Non-specific stimulation of host defenses against a bacterial challenge in malnourished hosts.

We have studied the effects of non-specific enhancement of host defenses in malnourished mice using muramyl dipeptide (MDP). The challenge, consisting of a bacteria laden suture, simulates a surgical wound infection. Adult mice were subjected either to a 48-h period of acute starvation or to a 2 week period of protein deprivation. In each type of malnutrition, mice treated with MDP 24 h before the bacterial challenge had statistically lower local and systemic bacterial recovery, with a corresponding improvement in short term survival, than did untreated controls. MDP enhances local bacterial containment, thereby substantially reversing the detrimental effects of malnutrition on host defences.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed2001

Development of PMMA-precoating metal prostheses via injection molding: residual stresses.

Injection molding polymethylmethacrylate (PMMA) was developed as a potential metal prosthesis precoating method for surgical implantation. However, residual stresses generated in the injection-molded PMMA affect the mechanical performance of the coating polymer. This study used plane polariscope testing to demonstrate the residual stress distribution in the injection-molded polymer. Slitting and strain gages were combined with finite element analysis to give a quantitative measure of the residual stresses. The residual stress testing indicated that the highest circumferential residual stress in the injection-molded PMMA was approximately 5 MPa in tension. Two methods, water soaking and slitting, were developed for reducing residual stresses. A series of four surgical implantation simulation processes were designed. The two methods for reducing residual stress were used in the simulations.

Animals↗
PubMed1997

Uncinate processes and Luschka joints influence the biomechanics of the cervical spine: quantification using a finite element model of the C5-C6 segment.

A fully three-dimensional finite element model of a C5-C6 motion segment of the human spine was developed and validated for the purpose of investigating the biomechanical significance of uncinate processes and Luschka joints. The original intact cervical model was modified to create two additional models. The first simulated the absence of Luschka joints by replacing the fissures with continuous annulus fibrosus and leaving the uncinate processes intact. The second model simulated a surgical resection of the uncinate processes, while leaving the Luschka joints intact. The results of these two models were compared with the intact model, which served as a baseline; thus, the relative contributions of these two structures to cervical motion were established. With use of our model, it was possible, for the first time, to provide quantitative data concerning the source of coupled motions in the lower cervical spine. In principle, the results from this model support the hypothesis of Penning and Wilmink. Our results indicate that the facet joints and Luschka joints are the major contributors to coupled motion in the lower cervical spine and that the uncinate processes effectively reduce motion coupling and primary cervical motion (motion in the same direction as load application), especially in response to axial rotation and lateral bending loads. Luschka joints appear to increase primary cervical motion, showing an effect on cervical motion opposite to that of the uncinate processes. Surgeons should be aware of the increase in motion accompanied by resection of the uncinate processes.

Biomechanical Phenomena↗
PubMed1995

Dynamic three-dimensional transesophageal echocardiography using a computed tomographic imaging probe--clinical potential and limitation.

Dynamic three-dimensional echocardiography is a new diagnostic tool for spatial visualisation of cardiac anatomy and volumetric assessment. A computer-controlled probe acquires parallel tomographic slices, from which dynamic three-dimensional images of the heart can be reconstructed. Thirty adult patients with valvular heart diseases, congenital heart diseases, intracardiac masses, heart failure and other cardiac lesions, underwent conventional two-dimensional (n = 30), three-dimensional echocardiography (n = 30) and thermodilution (n = 17). The feasibility, usefulness and possibility of simulating a surgical view of intracardiac anatomy and exact volumetry were determined. The two different morphologic images were compared qualitatively. For quantitative analysis volumetry was performed using standard thermodilution technique and dynamic three-dimensional echocardiography. In more than 80% of the patients additional morphologic information was gained and a strong correlation (r = 0.75-0.95) between two volumetry assessments was found. Based on this findings, dynamic three-dimensional echocardiography is an additional and valuable approach in the perioperative and intensive care management in this group of patients.

Adult↗
PubMed1993

[3-dimensional imaging diagnosis with a personal computer].

During orthodontic and surgical treatment planning of severe dentofacial deformities, 3D-reconstruction imaging from axial CT-scans could previously only be handled by high-capacity computers in radiological centers. The improved performance of personal computers enables CT-scan data be transferred to a standardized MS-DOS computer. The presented software displays a 3D-reconstruction and secondary reformed vertical slices within seconds on the monitor. The symmetry of the 3D-objects can be evaluated with a freely definable grid. The distance between two different landmarks in the 3D-image can also be measured. Various tools for data manipulation permit surgical treatment simulation. The advantage of 3D-imaging with a personal computer is the user-specified orientation of the software. The off-line computing system permits a high degree of flexibility independent of any computing center.

Cephalometry↗
PubMed1997

[Anatomical comment: Hohmann retractor. A source of danger to the sciatic nerve.].

In referring to the article by Stühmer the authors describe the topographic relationship between the sciatic nerve and an inserted normal Hohmann retractor or a specially designed retractor by Stühmer. By simulating the surgical circumstances the following observations are made:In lateral position and with external rotation of the hip the sciatic nerve is found directly posterior to the major trochanter. When inserting the Hohmann retractor its point slips between the trochanter and the sciatic nerve. The nerve lies directly on the retractor or can be injured by inserting it. Contrary to this the Stühmer retractor avoids pressure on or skewing of the nerve.

English Abstract↗
PubMed2003

[Emergency cricothyrotomy--puncture or anatomical preparation? Peculiarities of two methods for emergency airway access demonstrated in a cadaver model].

OBJECTIVES: The aim of the study was a demonstration of peculiarities of two invasive airway management methods performed by anesthesiology residents as a subgroup of emergency physicians. METHODS: During an airway management training seminar,2 groups including 18 anaesthesiology residents and 2 students performed a simulated emergency surgical cricothyrotomy on unfixed cadavers. The more experienced physicians in group 2 started with a puncture technique preceding a blind surgical approach. The time needed to perform each procedure and resulting complications were analyzed. RESULTS: The time taken ranged from 75 to 280 s (median 180 s) in group 1 and from 53 to 255 s (median 73 s) in group 2. The surgical approach caused "bleeding" in 40% (group 1) and 30% (group 2) and damage to the cartilages occurred in 20% and 30%, respectively. Punctures were performed within 10-36 s (median 25 s) and 70% were successful without complications. CONCLUSIONS: Puncture of the cricothyroid membrane can serve as initial emergency approach or as intermediate airway access until a surgical method is available.

Anesthesiology↗
PubMedDate not supplied

Brachial plexus injury from CT-guided RF ablation under general anesthesia.

Brachial plexus injury in a patient under general anesthesia (GA) is not uncommon, despite careful positioning and, particularly, awareness of the possibility. The mechanism of injury is stretching and compression of the brachial plexus over a prolonged period. Positioning the patient within the computed tomography (CT) gantry for abdominal or chest procedures can simulate a surgical procedure, particularly when GA is used. The potential for brachial plexus injury is increased if the case is prolonged and the patient's arms are raised above the head to avoid CT image degradation from streak artifacts. We report a case of profound brachial plexus palsy following a CT-guided radiofrequency ablation procedure under GA. Fortunately, the patient recovered completely. We emphasize the mechanism of injury and detail measures to combat this problem, such that radiologists are aware of this potentially serious complication.

Anesthesia, General↗