Dynamic behaviour of multilamellar vesicles under Poiseuille flow.

Surfactant solutions exhibit multilamellar surfactant vesicles (MLVs) under flow conditions and in concentration ranges which are found in a large number of industrial applications. MLVs are typically formed from a lamellar phase and play an important role in determining the rheological properties of surfactant solutions. Despite the wide literature on the collective dynamics of flowing MLVs, investigations into the flow behavior of single MLVs are scarce. In this work, we investigate a concentrated aqueous solution of linear alkylbenzene sulfonic acid (HLAS), characterized by MLVs dispersed in an isotropic micellar phase. Rheological tests show that the HLAS solution is a shear-thinning fluid with a power law index dependent on the shear rate. Pressure-driven shear flow of the HLAS solution in glass capillaries is investigated using high-speed video microscopy and image analysis. The so obtained velocity profiles provide evidence for a power-law fluid behaviour of the HLAS solution and images show a flow-focusing effect of the lamellar phase in the central core of the capillary. The flow behavior of individual MLVs shows analogies with that of unilamellar vesicles and emulsion droplets. Deformed MLVs exhibit typical shapes of unilamellar vesicles, such as parachute and bullet-like. Furthermore, MLV velocity follows the classical Hetsroni theory for droplets provided that the power law shear dependent viscosity of the HLAS solution is taken into account. The results of this work are relevant for the processing of surfactant-based systems in which the final properties depend on the flow-induced morphology, such as cosmetic formulations and food products.

Diffusive mixing of polymers investigated by Raman microspectroscopy and microrheology.

Diffusive mixing in a model polymer blend of limited miscibility (i.e., the pair polydimethylsiloxane/polyisobutene) is investigated. The diffusion process is followed in the actual droplet-based microstructure of the polymer blend, as opposed to the ideal planar geometry used in previous studies (Brochard et al. Macromolecules 1983, 16, 1638; Composto et al. Nature 1987, 328, 234). In our experiments we combine Raman microspectroscopy and video particle-tracking microrheology. The first technique allows us to monitor local concentration of the two polymers with high spatial resolution both inside and outside a micrometer-size droplet of the dispersed phase. In addition, microrheology enables to follow how the local viscosity inside the droplet changes during the diffusion. The polymer viscosity inside the droplet is determined by video tracking the Brownian motion of a polystyrene bead microinjected into the droplet. The microspectroscopic and microrheological data are combined to estimate the concentration dependence of the monomer friction factor of the two species, which is a key parameter to calculate the interdiffusion coefficient D. Numerical calculations based on such concentration-dependent interdiffusion coefficient D and several alternative models of the polymer diffusion are compared to the experimental concentration profiles. A satisfactory agreement is found for the so-called "slow theory" (Brochard et al.). A phenomenological model improving the agreement of the model with the experimental data is also presented.

Prevention of venous thromboembolism in spinal surgery.

Deep vein thrombosis (DVT), and its most feared complication, pulmonary embolism (PE), still have a high incidence with high risk for patients' health. Proven prophylactic measures are available but are generally underused, and DVT is still considered the most common cause of preventable death among hospitalized patients. The rationale for prophylaxis of venous thromboembolism is based on the clinically silent nature of the disease, the relatively high prevalence among hospitalized patients and the potentially tragic consequences of a missed diagnosis. During the last 15-20 years, spine surgery has changed radically, developing into a well-defined area of specialist surgery, and some attention is now being given to DVT events in spine surgery. The incidence of DVT during spine surgery is not documented in the literature, because only case reports or retrospective studies are reported. It would therefore be very helpful to initiate a multicenter study in order to understand this problem better and to develop, if possible, some guidelines on prophylactic measures in spine surgery. In doing so, we need to consider each patient's pattern, any risk factors and every kind of surgical technique related to DVT, in order to improve the outcome of the patient and to reduce any medicolegal problems that could arise from a thrombotic complication or an epidural hematoma, with its high potential for irreversible consequences.

Elastic stabilization alone or combined with rigid fusion in spinal surgery: a biomechanical study and clinical experience based on 82 cases.

The authors report their experience with the treatment of lumbar instability by a kind of spine stabilization. The elastic stabilization, which follows a new philosophy, is obtained by an interspinous device, and should be used alone in degenerative disc disease, recurrent disc herniation and in very low grade instability, or in association with rigid fusion for the prevention of pathology of the border area. In collaboration with bioengineers, we carried out an experimental study on a lumbar spine model in order to calculate stresses and deformations of lumbar disc during simulation of motion, in physiological conditions and when elastic stabilization is combined with rigid fusion. Results suggest that elastic stabilization reduces stresses on the adjacent disc up to 28 degrees of flexion. Based on this preliminary result, we began to use elastic stabilization alone or combined with fusion in 1994. To date, we have performed 82 surgical procedures, 57 using stabilization alone and 25 combined with fusion, in patients affected by degenerative disc disease, disc herniation, recurrence of disc herniation or other pathologies. Clinical results are satisfactory, especially in the group of patients affected by recurrent disc herniation, in whom the elastic device was used alone.

Nontropical sprue with several major complications.

A 43-yr-old woman with celiac disease had an excellent response to a gluten-free diet for 20 yr. Subsequently, she developed the complications of chronic nongranulomatous ulcerative jejunitis and malignant histiocytosis associated with some atypical clinical and pathological features. The early criteria for surgical intervention, to prevent a rapidly fatal malignant histiocytosis, are described.

[Synovial osteochondromatosis]. / L'osteocondromatosi sinoviale.

The Authors have examined the clinical history, roentgenograms, differential diagnosis and treatment of synovial osteochondromatosis.

[Kinesitherapy in lumbago]. / La kinesiterapia nelle lombalgie.

Since most back pain syndromes are due to excessive and long-lasting incorrect postures, we think that such illness may benefit from kinesiotherapy. There must be considered 2 types of back pain: disc pain and static pain. We advise to patients various self control techniques and muscle potentiating gymnastics. Besides these techniques, other adjuvant therapies may be prescribed.

[Considerations on various spinal pains]. / Considerazioni su alcune rachialgie.

Any nerve root irritation from about T6 to L1 is able to carry about parietal and visceral pain in the abdomen, owing to the metameric distribution of the splanchnic and somatic afferent ways along the dorsal roots at all these levels. The cause of abdominal segmental neuralgia are numerous. Radicular abdominalgia is a syndrome of painful and paresthetic sensations, which involve both somatic and visceral components of one or more segments, according to the metameric law. In the osteo-arthrosis in the dorsal intervertebral joints is a most common cause of radicular syndromes simulating intra-abdominal surgical conditions.

[1 year of traumatologic activity in the Emergency Orthopedic Unit of the G. Pini Institute (statistical data)]. / Un anno di attività traumatologica presso L'S.T.U. dell'istituto (rilievi statistici).

The Authors have considered one year's traumatological activity in the G. Pini Institute's S.T.U. by drawing some statistical results. The data refer to the traumas ambulatorium-treated and to all those which required hospitalization during 1979. The total of the traumas surveyed in 1979 is 33335 of which 1812 required urgent hospitalization (5.44%). Previous statistics show 6679 patients in 1961 and 3209 in 1956. We can realize how these figures have increased in a few years (and in this abstract the different kinds of traumas are also highlighted) without any adjustment to the existing structures and equipment which are completely insufficient.

[Osteochondritis dissecans of the elbow (presentation of 2 rare cases)]. / L'osteocondrite dissecante del gomito (presentazione di due rari casi).

The authors show two cases of dissecting osteochondritis of elbow, confirming the frequent absence of a clinical symptomatology in the initial stages of such disease and the benignancy of its course. From a careful study of the casuistries present in literature, what emerges is the rareness of this location, together with a prudent therapeutical trend with periodic clinical and radiographical checkings, reserving the surgical solution to the cases of articular free body with episodes of block.

[Triple screwing in sub-capitated fractures of the neck of the femur (our experience)]. / Il triplice avvitamento nelle fratture sottocapitate del collo del femore.

The authors showed a method of treatment of the fractures of femur-neck under head, being persuaded of its validity, for the good remote results in the 38 cases shown, the lighter trauma caused to this type of patients, and the lower risk and operative care required.

[Considerations on the treatment of fractures of the olecranon]. / Considerazioni sul trattamento delle fratture di olecrano.

The authors illustrated the principles of dynamic osteosynthesis applied to olecranon, showed the good results obtained in 40 cases, and pointed out the importance of the early mobilization on a stabilized fracture focus.

[Fractures of the radial capitellum. Resection of the capitellum (remote results)]. / Fratture del capitello radiale. Resezione del capitello (risultati a distanza).

The authors showed 32 cases of resection of radial capital, inspected 2 years after operation, the results of which, as compared with those obtained through other methods, revealed a good remote validity. This is true in cases where no other important lesions, especially in the periarticular soft parts, were present.

[Arthrography of the operated meniscus]. / L'artrografia nel menisco operato.

The authors performed 20 double contrast arthrographits in syntomatic patients after meniscectomy. The results demonstrate that the lesions occur more frequently in partially excised menisc compared with totally existed ones. In some cases no meniscal regeneration has been found for menisci excised 2 to 4 years before.

[Considerations on the surgical treatment of hallux valgus]. / Considerazioni sul trattamento chirurgico dell'alluce valgo.

The authors, after showing a critical analysis of the most interesting operations for correction of valgus big toe in the history of orthopaedics, show the technique they followed, as well as the results obtained, in a specimen chosen among the patients treated with such method.

[Anatomo-pathologic and therapeutic considerations on the Papineau method]. / Considerazioni anatomo-patologiche e terapeutiche sulla "metodica Papineau".

The authors study the treatment of bone infections through Papineau's technique, and emphasize the element they consider essential in the process restoring the loss of substance: the "bouton" according to the French School. On the basis of the experience deriving from the treatment of 22 patients, they subsequently point out the importance of local antibiotic therapy and, on the contrary, the inefficacy of the administration of antibiotics by general way, at least as far as the not strictly surgical period is concerned.

[Septic arthritis of the knee in adults. Treatment with closed irrigation-drainage]. / Artrite settica del ginocchio nell'adulto. Trattamento con irrigazione drenaggio a cielo chiuso.

The Authors report their experiences in Redon tube closed washing-drainage treatment of secondary septic arthritis in adults. This technique, used at an early stage as an alternative to needle drainage, does not require plaster immobilisation and has allowed a good residual function to be obtained. In case of absence of response to the treatment, it is considered inadvisable to persist; in such case the surgical approach with "functional treatment", and with or without combined synovectomy, is recommended.