Late Implant Failure in Cervical Disc Arthroplasty (M6-C, Spinal Kinetics) Causing Radiculopathy and Myelopathy.

Cervical disc arthroplasty (CDA) is an approved surgical treatment option in selected patients with cervical spinal disc degeneration. Even though CDA is a standard procedure since 20 years, there is a lack of information about long term performance. The published reoperation rates after CDA are low and comparable to anterior cervical fusion.

[Minimally invasive transforaminal lumbar interbody fusion].

Objective: Instrumented fusion of lumbar motion segments using a minimally invasive technique.

Indications: Degenerative disc disease, segmental degeneration, degenerative spondylolisthesis, isthmic spondylolisthesis, pseudarthrosis, other spinal lumbar instabilities, disc prolapse, revision for failed back surgery syndrome, unilateral neuroforaminal stenosis, facet joint arthrosis.

Contraindications: High-grade spondylolisthesis (Meyerding grades III/IV, spondyloptosis), bilateral nerve root compression, vertebral fractures, tumors, high-grade spinal instabilities, primary spinal deformities, multilevel pathologies.

Active bundles of polar and bipolar filaments.

Bundles of actin filaments and molecular motors of the myosin family are a common subcellular organizational motif. Typically, such bundles are under contractile stress resulting from interactions between the filaments and the motors. This holds in particular for contractile rings that appear in the late stages of cell division in animal cells and that cleave the mother into two daughter cells.

Transoral Spine Surgery - an Update.

Even though in recent years the number of transoral spinal interventions has decreased in Europe and North America - mainly because of the progress in the drug therapy of rheumatism, there are still pathologies that can only be addressed by a transoral approach. The classical transoral approach can be expanded in collaboration with oral-maxillofacial surgery and ear, nose and throat surgery, but this is rarely necessary. The transoral approach is now mainly used for resection of pathological tissue.

Staged surgical treatment for infection of total disc arthroplasty: three cases and a narrative review of the literature.

Although total disc arthroplasty (TDA) is a common procedure for selected cases of degenerative disc disease, until today there are only two cases of TDA infections reported in the literature. We report three cases of postoperative TDA infections, two developed cutaneous fistulas. To eradicate the infectious site, a staged removal of the device, resolute debridement, and stabilization plus fusion is proposed.

[Indications for Surgical Correction of Degenerative Spondylolisthesis].

There is no general consensus about indications for surgical treatment of degenerative spondylolisthesis. This is--in part--due to a paucity of knowledge of its natural history and outcomes of conservative treatment, as well as a relatively small number of sufficiently powered outcome studies for surgical treatment. We aim to provide an overview of current surgical techniques and deduce indications based on two simple principles: presence of neurological deficits and instability.

Combating the Health Risks of Sedentary Behavior in the Contemporary Radiology Reading Room.

Objective: We detail the association of sedentary behavior with a variety of health problems and provide the radiologist with a number of simple activities and techniques that can improve overall health while still meeting the productivity demands of a high-volume practice. Although these techniques are well known and recognized in the fitness and nutrition literature, they are not widely used in the radiology reading room. The computer- and workstation-based work routinely performed by diagnostic radiologists typically occurs in the seated position, leading to more than 8 hours per day of sitting.

Elongational flow effects on the vortex growth out of Couette flow in ferrofluids.

The growth behavior of stationary axisymmetric vortices and of oscillatory, nonaxisymmetric spiral vortices in Taylor-Couette flow of a ferrofluid in between differentially rotating cylinders is analyzed using a numerical linear stability analysis. The investigation is done as a function of the inner and outer cylinder's rotation rates, the axial wave number of the vortex flows, and the magnitude of an applied homogeneous axial magnetic field. In particular, the consequences of incorporating elongational flow effects in the magnetization balance equation on the marginal control parameters that separate growth from decay behavior are determined.

[Cervical disc herniation].

The cervical disc herniation is characterized by prolapsed nucleus pulposus material through the annulus into the spinal canal. The local mechanical or chemical irritation of neural structures typically leads to symptoms of radiculopathy, cervicocephalgia or myelopathy. Pronounced sensorimotor deficits or intractable pain constitute surgical treatment.

Islands of instability for growth of spiral vortices in the Taylor-Couette system with and without axial through flow.

We present numerical calculations of the linearized Navier-Stokes equations for axially extended and axially localized spiral structures in the Taylor-Couette system. The eigenvalue surface for spiral vortices with azimuthal wave number M=2 shows significantly more structure than that for vortices with M=0 and 1. Islands are found in parameter space where axially periodic vortex perturbations can grow.

Influence of homogeneous magnetic fields on the flow of a ferrofluid in the Taylor-Couette system.

We investigate numerically the influence of a homogeneous magnetic field on a ferrofluid in the gap between two concentric, independently rotating cylinders. The full Navier-Stokes equations are solved with a combination of a finite difference method and a Galerkin method. Structure, dynamics, symmetry properties, bifurcation, and stability behavior of different vortex structures are investigated for axial and transversal magnetic fields, as well as combinations of them.

End wall effects on the transitions between Taylor vortices and spiral vortices.

We present numerical simulations as well as experimental results concerning transitions between Taylor vortices and spiral vortices in the Taylor-Couette system with rigid, nonrotating lids at the cylinder ends. These transitions are performed by wavy structures appearing via a secondary bifurcation out of Taylor vortices and spirals, respectively. In the presence of these axial end walls, pure spiral solutions do not occur as for axially periodic boundary conditions but are substituted by primary bifurcating, stable wavy spiral structures.

Nonlinear defects separating spiral waves in Taylor-Couette flow.

Stable domain walls which are realized by a defect between oppositely traveling spiral waves in a pattern-forming hydrodynamic system, i.e., Taylor-Couette flow, are studied numerically as well as experimentally.

Wave-number dependence of the transitions between traveling and standing vortex waves and their mixed states in the Taylor-Couette system.

Previous numerical investigations of the stability and bifurcation properties of different nonlinear combination structures of spiral vortices in a counter-rotating Taylor-Couette system that were done for fixed axial wavelengths are supplemented by exploring the dependence of the vortex phenomena waves on their wavelength. This yields information about the experimental and numerical accessibility of the various bifurcation scenarios. Also backward bifurcating standing waves with oscillating amplitudes of the constituent traveling waves are found.

Bifurcation of standing waves into a pair of oppositely traveling waves with oscillating amplitudes caused by a three-mode interaction.

A flow state consisting of two oppositely traveling waves (TWs) with oscillating amplitudes has been found in the counter-rotating Taylor-Couette system by full numerical simulations. This structure bifurcates out of axially standing waves that are nonlinear superpositions of left- and right-handed spiral vortex waves with equal time-independent amplitudes. Beyond a critical driving, the two spiral TW modes start to oscillate in counterphase due to a Hopf bifurcation.

Stabilization of domain walls between traveling waves by nonlinear mode coupling in Taylor-Couette flow.

We present a new mechanism that allows the stable existence of domain walls between oppositely traveling waves in pattern-forming systems far from onset. It involves a nonlinear mode coupling that results directly from the nonlinearities in the underlying momentum balance. Our work provides the first observation and explanation of such strongly nonlinearly driven domain walls that separate structured states by a phase generating or annihilating defect.

Localized spirals in Taylor-Couette flow.

We present a type of spiral vortex state that appears from a supercritical Hopf bifurcation below the linear instability of circular Couette flow in a Taylor-Couette system with rigid end plates. These spirals have been found experimentally as well as numerically as "pure" states but also coexist with "classical" spirals (or axially standing waves for smaller systems) which typically appear from linear instability in counterrotating Taylor-Couette flow. These spiral states have an axial distribution of the strongly localized amplitude in the vicinity of the rigid end plates that confine the system in the axial direction.

Controlling the stability transfer between oppositely traveling waves and standing waves by inversion-symmetry-breaking perturbations.

The effect of an externally applied flow on symmetry degenerated waves propagating into opposite directions and standing waves that exchange stability with the traveling waves via mixed states is analyzed. Wave structures that consist of spiral vortices in the counter rotating Taylor-Couette system are investigated by full numerical simulations and explained quantitatively by amplitude equations containing quintic coupling terms. The latter are appropriate to describe the influence of inversion-symmetry-breaking perturbations on many oscillatory instabilities with O(2) symmetry.

Free vascularized fibular grafting for reconstruction after tumor resection in the upper extremity.

Background: Limb salvage is viable in the majority of patients with malignant bone tumors, but especially in case of extensive tumors and bad soft tissue conditions, it is challenging in upper extremity.

Objectives/method: The clinical and radiological results of 21 patients, who had free vascularized fibular grafts (VFG), for diaphyseal (14), and epipyseal (7) defect reconstruction of the upper extremity, are presented. The indications for VFG were resection after osteosarcoma (9 cases), Ewings sarcoma (9 cases), chondrosarcoma (1 case), rhabdomyosarcoma (1 case), and 1 case of fibrous dysplasia.

Competition between traveling fluid waves of left and right spiral vortices and their different amplitude combinations.

Stability, bifurcation properties, and the spatiotemporal behavior of different nonlinear combination structures of spiral vortices in the counterrotating Taylor-Couette system are investigated by full numerical simulations and by coupled amplitude-equation approximations. Stable cross-spiral structures with continuously varying content of left- and right-spiral modes are found. They provide a stability transferring connection between the initially stable, axially counterpropagating wave states of pure spirals and the axially standing waves of so-called ribbons that become stable slightly farther away from the onset of vortex flow.

Spiral vortices traveling between two rotating defects in the Taylor-Couette system.

Numerical calculations of vortex flows in Taylor-Couette systems with counter rotating cylinders are presented. The full, time-dependent Navier-Stokes equations are solved with a combination of a finite difference and a Galerkin method. Annular gaps of radius ratio eta=0.