Management of painful spinal lesions caused by multiple myeloma using percutaneous acrylic cement injection.

BACKGROUND AND PURPOSE: Spinal lesions with marked destruction are common site of morbidity in patients with multiple myeloma causing serious clinical symptoms. The aim of the study was to evaluate the therapeutic benefit of percutaneous vertebroplasty (PVP) in treating vertebral body lesions in patients suffering from multiple myeloma. MATERIALS AND METHODS: Twenty nine patients (55 vertebral bodies) were treated after complete diagnostic evaluation, preparation and obtaining informed consent. Needle position and acrylic material injection was performed under fluoroscopic guidance. RESULTS: Average visual analogue score dropped from 7.8 before to 2.3 after the intervention. Soft tissue leak was present at 9 treated levels, small epidural cement collection at 5, venous leak at 4 and intradiscal leak at 3 levels without any clinically manifest complications. The effects of PVP were stable in all of the patients at 12 months follow-up. Subjective outcome scores collected through follow-up showed improvement of +1.45 in pain, + 1.15 in ambulation and + 1.23 in medication use. There were recurrence of back pain in 9 patients at non-treated levels due to the new lesions. CONCLUSION: In our series, PVP of painful lesions caused by multiple myeloma provides immediate and long-term pain relief. The procedure is safe and, despite of the present leakage of cement, may be performed on outpatients basis.

[Treatment of unstable closed tibial shaft fractures by external fixation].

The fracture of tibia shaft is one of the most common fracture of long bones. The authors bring out the results of the treatment of 90 patients with unstable closed tibial shaft fractures treated by the use of Mitkovic external fixation systems. Within the analayzed group there were 66 (73%) male and 24 (27%) female. The average patients age was 43.9 years (range 15 to 82). Excellent result in treatment of unstable closed tibial shaft fractures with external fixation were achieved in 15 (16,7%) patients, very good in 38 (42,2%) patients, good in 24 (26,7%), poor in 9 (10%) and bad in 4 (4,4%) patients. With 4 (4,4%) patients pseudoarthrosis was formed. Additional treatment of patients with pseudoarthrosis (spongioplastic and placing of CD device) led to pseudoarthrosis healing. Within the analyzed group in all patients treated with extenal fixation there were no registered cases of postoperative osteitis. External fixation by the use of Mitkovic external fixation is one of the method of choose in the treatment of unstable closed tibial fractures, providing dynamic and balanced biomehanical conditions for fracture healing.

Hairpin turn dislocations in two-dimensional smectic phases of long semiflexible polymers.

We elucidate hairpin turn dislocations in two-dimensional smectic phases of long semi-flexible polymers. We discuss hairpin shapes, sizes, and free energies. We find that hairpin dislocation core may be, under some circumstances, substantially bigger than the smectic period size. Such hairpin dislocations are accompanied by large voids that are stable equilibrium structures with sizes determined by a competition of the polymer bending elasticity and smectic bulk elasticity. The large size of hairpin voids is associated with a low hairpin energy, much smaller than anticipated before. The actual hairpin shape, size, and energy are all qualitatively sensitive to the detailed nature of smectics. We document this by considering hairpin dislocations in lyotropic smectics (systems stabilized by repulsion between polymers, with a positive osmotic pressure) and in thermotropic smectics (systems stable even at zero osmotic pressure, with a preferred distance between semiflexible molecules). We discuss in detail hairpin dislocations in lyotropic sterically stabilized Smectics as well as in DNA-cationic lipid complexes. We elucidate the extinction of hairpin dislocations by annihilations with polymer end points. In lyotropic smectics, rates of these processes are shown to be limited by sluggish reptation of semiflexible molecules, as well as by substantial energy barriers.

Interfacial coarsening dynamics in epitaxial growth with slope selection

We investigate interfacial dynamics of molecular-beam epitaxy (MBE) growth in the presence of instabilities inducing formation of pyramids. We introduce a kinetic scaling theory which provides an analytic understanding of the coarsening dynamics laws observed in numerous experiments and simulations of the MBE. We address MBE growth on crystalline surfaces with different symmetries in order to explain experimentally observed differences between the growth on (111) and (001) surfaces and understand the coarsening exponents measured on these surfaces. We supplement our kinetic scaling theory by numerical simulations which document that the edges of the pyramids, forming a network across the growing interface, are essential for qualitative understanding of the coarsening dynamics of molecular-beam epitaxy.

Structural properties of the sliding columnar phase in layered liquid crystalline systems.

Under appropriate conditions, mixtures of cationic and neutral lipids and DNA in water condense into complexes in which DNA strands form local two-dimensional (2D) smectic lattices intercalated between lipid bilayer membranes in a lamellar stack. These lamellar DNA-cationic-lipid complexes can in principle exhibit a variety of equilibrium phases, including a columnar phase in which parallel DNA strands form a 2D lattice, a nematic lamellar phase in which DNA strands align along a common direction but exhibit no long-range positional order, and a possible new intermediate phase, the sliding columnar (SC) phase, characterized by a vanishing shear modulus for relative displacement of DNA lattices but a nonvanishing modulus for compressing these lattices. We develop a model capable of describing all phases and transitions among them and use it to calculate structural properties of the sliding columnar phase. We calculate displacement and density correlation functions and x-ray scattering intensities in this phase and show, in particular, that density correlations within a layer have an unusual exp(-const x ln(2)r) dependence on separation r. We investigate the stability of the SC phase with respect to shear couplings leading to the columnar phase and dislocation unbinding leading to the lamellar nematic phase. For models with interactions only between nearest neighbor planes, we conclude that the SC phase is not thermodynamically stable. Correlation functions in the nematic lamellar phase, however, exhibit SC behavior over a range of length scales.

Flexible polymers and thin rods far from equilibrium: buckling dynamics

We investigate the dynamics of the classical Euler buckling instability of compressed objects such as flexible molecular chains and thin rods moving in a viscous medium. We find that flexible chains undergo a coarsening process self-similar in time. They develop a wavelike pattern whose amplitude and wavelength grow in time. We relate the buckling dynamics to phase ordering phenomena. The role of the order parameter here is played by the chain slope with respect to the straight initial chain configuration.

Tethered membranes far from equilibrium: buckling dynamics.

We study the dynamics of the classical Euler buckling of compressed solid membranes. We relate the membrane buckling dynamics to phase ordering phenomena. Membranes develop a wavelike pattern whose wavelength grows, via coarsening, as a power of time. We find that evolving membranes are similar to growing surfaces ("growing interfaces") whose transverse width grows as a power of time. The morphology of the evolving membranes is characterized by the presence of a network of growing ridges where the elastic energy is mostly localized. We used this fact to develop a scaling theory of the buckling dynamics that gives analytic estimates of the coarsening exponents. Our findings show that the membrane buckling dynamics is characterized by a distinct scaling behavior not found in other coarsening phenomena.