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Based on the theory and principles of splinting in the reduction of burn contractures, a facial conformer was fabricated with satisfactory results and further surgery was averted. The facial skin softened and regained pliability and function, thus the lower eyelids were restored to their normal position, which allowed full closure and prevented further drying of the cornea and conjunctiva.
Twenty-seven patients who underwent microvasculosurgical free tissue transfers for head and neck reconstruction with a M. rectus abdominis or M. latissimus dorsi flap are reviewed. In this series the flap reconstruction was completed in 15 patients with extraoral defects, in six patients with an intraoral defect and in six patients with a combined intra and extraoral defect. Split thickness skin graft coverage was used in all cases. All free muscle grafts survived and good take of the split skin was obtained. In extraoral defects coverage of free muscle transfer with split thickness skin grafts results in a better color match than with musculocutaneous flaps and complements the appearance and pliability of the free muscle flap. Reshaping and three-dimensional positioning made reconstruction of every intraoral defect and combined intra and extraoral defects possible. In skilled hands, free tissue transfer provides a reliable method for reconstruction of almost every defect in the head and neck.
Passage of a flexible catheter into a septic flexor tendon sheath can be difficult and time consuming because of the catheter's pliability. This article discusses a technique for converting the flexible catheter into a semirigid stylet.
In cylindric fragments of the rat tail arteries, activation of the smooth muscle with noradrenaline was found to enhance the vessels' rigidity both in stretching and in compression, i.e., the activation of the smooth muscle layer decreased the arteries' pliability.
PURPOSE: To evaluate the physical characteristics and behavior of coils for endovascular therapy. METHODS: Mechanically detachable coils were constructed with simple helical (4 mm X 10 cm and 8 mm X 30 cm) and pretzel shapes (4 mm X 5 cm) made from three metals using 0.003- and 0.004-in wire. Stiffness or pliability, frictional resistance, shape memory, and coil stability were evaluated in vitro. RESULTS: The 0.004-in wire stock coils proved significantly stiffer when compared with the 0.003-in coils. Tungsten coils proved least pliable; platinum coils were intermediate in stiffness; and nitinol coils were softest. Frictional resistance in the catheter was greatest for stiffer coils. The 5-cm pretzel coil consistently created more frictional force than the 10- or 30-cm simple helical coils. Despite a shorter length, the 4-mm simple helical coil exerted more frictional force than the 8-mm coil. Stiffer metal coils constructed of larger-diameter wire (0.004 in) were more stable than softer coils. CONCLUSION: Stiffer coils exert greater frictional forces within the catheter and a greater resistive force during bending but are more stable after placement. Frictional forces also depend on the complex three-dimensional shape of the coil and the diameter of the turns in that shape rather than coil length. These data suggest that a family of coils of different metals is optimal for varied intravascular needs.
In modern multi-disciplinary cancer treatment, rehabilitation and functional results represent utmost intent in reconstructive surgery of the oral cavity. Even in cases where the stage of disease is advanced) and the perspective of survival is limited, it is possible to achieve an acceptable quality of life. The authors report, in this study, the morpho-functional results and the morbidity observed in glossectomies in which the reconstruction was performed using three different methods. In a total of 264 reconstructive flaps of the head and neck regions, the authors considered three groups of 15 patients that had had reconstruction after the demolitive procedure. Respectively these groups were divided by the followed methods: free forearm flap, pectoralis major myocutaneous flap and nasolabial flap. The morbidity showed an extremely low rate of flap loss in all the groups, but "minor" complications, such as fistulas and leakages, were significantly more frequent in the myocutaneous flaps group. Functional evaluation for speech and deglutition showed good results in most patients. Extremely severe postoperative conditions as a permanent NG tube or incomprehensible speech had been observed in less than 15% of the cases. Particularly, the pectoralis major flap, showed its best functional performances in the total or subtotal glossectomies with a sacrifice of the muscles of the oral floor. The free forearm flap is reliable and safe with its low thickness and pliability, especially for partial glossectomies. The nasolabial flap was confirmed to be the first reconstructive choice for selected limited resections of the tongue and of the antero-lateral floor. With this experience it is possible, even in more complex free flaps, to reduce the time consumption and the complication rate. Free flaps do not substitute routinely myocutaneous and conventional flaps, but they represent the "ideal" reconstructive alternatives for specific and selected indications.
OBJECTIVE: To investigate possible injury mechanisms in the eyes of elderly individuals and the effects of lens stiffness on model outputs indicative of injury as a function of age. METHODS: Three separate frontal impact scenarios, a foam particle (30 m/s), steering wheel (15 m/s), and air bag (67 m/s), were simulated with a validated finite-element model to determine the effects of changing lens stiffness on the eye when subjected to blunt trauma. The lens stiffness of the model was increased with increasing age using stiffness values determined from the literature for 3 age groups. RESULTS: The computational eye model demonstrated increasing peak stress in the posterior portion of the ciliary body and decreasing peak stress in the posterior portion of the zonules with increasing lens stiffness for the 2 most severe impact types, the air bag and steering wheel. Peak deformation of the lens decreased with increasing lens stiffness. CONCLUSIONS: On the basis of the computational modeling analysis, the risk of eye injury increases with age; as a result, the eyes of elderly patients may be more susceptible to ciliary body-related eye injuries in traumatic-impact situations. Clinical Relevance These data support the contention that trauma-induced damage to the lens, ciliary body, and zonules may be related to increased stiffness of the lens. The data indicate that all people, especially elderly individuals, should use safety systems while driving an automobile and sit as far from the air bag as is comfortable. Those in sports or work environments requiring protective lenses should wear them. Designers of air bags and automobile companies should continue to work to reduce the potential that the air bag will contact the eye.
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BACKGROUND: Peripheral nerve repair using autograft material has several shortcomings, including donor site morbidity, inadequate return of function, and aberrant regeneration. Recently, peripheral nerve research has focused on the generation of synthetic nerve guidance conduits that might overcome these phenomena to improve regeneration. In our laboratory, we use the unique chemical and physical properties of synthetic polymers in conjunction with the biological properties of Schwann cells to create a superior prosthesis for the repair of multiply branched peripheral nerves, such as the facial nerve. OBJECTIVES: To create a polymeric facial nerve analog approximating the fascicular architecture of the extratemporal facial nerve, to introduce a population of Schwann cells into the analog, and to implant the prosthesis into an animal model for assessment of regeneration. RESULTS: Tubes of poly-L-lactic acid (molecular weight, 100000) or polylactic-co-glycolic acid copolymer were formed using a dip-molding technique. They were created containing 1, 2, 4, or 5 sublumina, or "fascicular analogs." Populations of Schwann cells were isolated, expanded in culture, and plated onto these polymer films, where they demonstrated excellent adherence to the polymer surfaces. Regeneration was demonstrated through several constructs. CONCLUSIONS: A tubular nerve guidance conduit possessing the macroarchitecture of a polyfascicular peripheral nerve was created. The establishment of resident Schwann cells onto poly-L-lactic acid and polylactic-co-glycolic acid surfaces was demonstrated, and the feasibility of in vivo regeneration through the conduit was shown. It is hypothesized that these tissue-engineered devices, composed of widely used biocompatible, biodegradable polymer materials and adherent Schwann cells, will be useful in promoting both more robust and more precisely directed peripheral nerve regeneration.
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Ligand binding may involve a wide range of structural changes in the receptor protein, from hinge movement of entire domains to small side-chain rearrangements in the binding pocket residues. The analysis of side chain flexibility gives insights valuable to improve docking algorithms and can provide an index of amino-acid side-chain flexibility potentially useful in molecular biology and protein engineering studies. In this study we analyzed side-chain rearrangements upon ligand binding. We constructed two non-redundant databases (980 and 353 entries) of "paired" protein structures in complexed (holo-protein) and uncomplexed (apo-protein) forms from the PDB macromolecular structural database. The number and identity of binding pocket residues that undergo side-chain conformational changes were determined. We show that, in general, only a small number of residues in the pocket undergo such changes (e.g., approximately 85% of cases show changes in three residues or less). The flexibility scale has the following order: Lys > Arg, Gln, Met > Glu, Ile, Leu > Asn, Thr, Val, Tyr, Ser, His, Asp > Cys, Trp, Phe; thus, Lys side chains in binding pockets flex 25 times more often then do the Phe side chains. Normalizing for the number of flexible dihedral bonds in each amino acid attenuates the scale somewhat, however, the clear trend of large, polar amino acids being more flexible in the pocket than aromatic ones remains. We found no correlation between backbone movement of a residue upon ligand binding and the flexibility of its side chain. These results are relevant to 1. Reduction of search space in docking algorithms by inclusion of side-chain flexibility for a limited number of binding pocket residues; and 2. Utilization of the amino acid flexibility scale in protein engineering studies to alter the flexibility of binding pockets.
Interventional magnetic resonance imaging (MRI) offers potential advantages over conventional interventional modalities such as X-ray fluoroscopy, ultrasonography, and computed tomography (CT). In particular, it does not use ionizing radiation, can provide high-quality images, and allows acquisition of oblique sections. We have carried out a feasibility study on the use of interventional MRI to track a flexible microendoscope in the paranasal sinuses. In this cadaver study, high-speed MRI was used to track a passive marker attached to the end of the endoscope. Automatic image registration algorithms were used to transfer the coordinates of the endoscope tip into the preoperative MRI and CT images, enabling us to display the position of the endoscope in reformatted orthogonal views or in a rendered view of the preoperative images. The endoscope video images were digitized and could be displayed alongside an approximately aligned, rendered preoperative image. Intraoperative display was provided in the scanner room by means of an liquid crystal display (LCD) projector. We estimate the accuracy of the endoscope tracking to be approximately 2 mm.
Understanding the structures of thick filaments and their relation to muscle contraction has been an important problem in muscle biology. The flexural rigidity of natural thick filaments isolated from Caenorhabditis elegans as determined by statistical analysis of their electron microscopic images shows that they are considerably more rigid (persistence length=263 microm) than similarly analyzed synthetic actin filaments (6 microm) or duplex DNA (0.05 microm), which are known to be helical ropes. Indeed, cores of C. elegans thick filaments, having only 11% of the mass per unit length of intact thick filaments, are quite rigid (85 microm) compared with the thick filaments. Cores comprise the backbones of the thick filaments and are composed of tubules containing seven subfilaments cross-linked by non-myosin proteins. Microtubules reconstituted from tubulin and microtubule-associated proteins are nearly as rigid (55 microm) as the cores. We propose a model of coupled tubules as the structural basis for the observed rigidity of natural thick filaments and other linear structures such as microtubules. A similar model was recently presented for microtubules [Felgner et al., 1997]. This coupled tubule model may also explain the differences in flexural rigidity between natural rabbit skeletal muscle thick filaments (27 microm) or synthetic thick filaments reconstituted from myosin and myosin binding protein C (36 microm) and those reconstituted from purified myosin (9 microm). The more flexible myosin structures may be helical ropes like F-actin or DNA, whereas the more rigid muscle or synthetic thick filaments which contain myosin and myosin binding protein C may be constructed of subfilaments coupled into tubules as in C. elegans cores. The observed thick filament rigidity is necessary for the incompressibility and lack of flexure observed with thick filaments in contracting skeletal muscle.
BACKGROUND: The purpose of this study was to thoroughly evaluate the relationship of possible mechanical and environmental conditions in the testing of spinal joint segments, including ambient-temperature exposure, accumulated test cycles, angular-deformation rate, and moisture condition on the motion characteristics of joints, with the example of isolated spinal segments. METHODS: In one test, controlled loading was applied to six motion segments every 8 hours in each of the primary anatomical directions while moisture was held constant. In a second test, 18 specimens were divided equally into moisture-static, air-exposed, and slowly irrigated groups and loaded to 500 cycles. In a third test, a similar sample was tested over a range of angular-deformation rates (0.6-5.1 degrees/second). RESULTS: Range of motion (ROM) increased steadily with ambient-temperature exposure time, resulting in a 10% change at about 20 hours but was most stable in the moisture-static group over both accumulated load cycles and loading rate changes. CONCLUSIONS: The most critical factor for functional testing of spinal segments appears to be length of exposure.
BACKGROUND: A negative association has previously been reported between long-lasting physically heavy work and some measures of physical capacity. This relationship was further investigated in a 24-year follow-up study of 484 middle-aged men and women from the general population. METHODS: A questionnaire was administered in 1993 concerning retrospective recall of physical work loads and physical training in the time span between 1970 and 1993. Laboratory tests performed in 1993 included tests of muscle function (maximal isometric strength and dynamic endurance) and aerobic power (submaximal ergometer test). RESULTS: Consistent with the hypothesis, but mainly among the women, associations between long-lasting physically heavy demands and low trunk flexion strength, squatting endurance, and aerobic power were observed. In contrast, low isometric hand grip strength and low weight lifting endurance were seldom seen among those with high physical work loads, indicating a possible maintaining or training effect on the hand/arm/shoulder muscle groups. CONCLUSIONS: Physically heavy work seems to have a different impact on different parts of the musculoskeletal system, an effect that is also different between men and women.
We took three types of bioactive bone cement (designated AWC, HAC, and TCPC), each with a different bioactive filler, and evaluated the influence of each filler on the mechanical properties and osteoconductivity of the cement. The cements consisted of bisphenol-a-glycidyl methacrylate-based (Bis-GMA based) monomers as an organic matrix, with a bioactive filler of apatite/wollastonite containing glass-ceramic (AW-GC) or sintered hydroxyapatite (HA) or beta-tricalcium phosphate (beta-TCP) powder. Each filler was mixed with the monomers in proportions of 50, 70, and 80% (w/w), giving a total of nine cement subgroups. The nine subgroups were designated AWC50, AWC70, AWC80, HAC50, HAC70, HAC80, TCPC50, TCPC70, and TCPC80. The compressive and bending strengths of AWC were found to be higher than those of HAC and TCPC for all bioactive filler contents. We also evaluated the cements in vivo by packing them into the intramedullary canals of rat tibiae. To compare the osteoconductivity of the cements, an affinity index was calculated for each cement; it equaled the length of bone in direct apposition to the cement, expressed as a percentage of the total length of the cement surface. Microradiographic examination up to 26 weeks after implantation revealed that AWC showed a higher affinity index than HAC and TCPC for each filler content although the affinity indices of all nine subgroups (especially the AWC and HAC subgroups) increased with time. New bone had formed along the AWC surface within 4 weeks, even in the cement containing AW-GC filler at only 50% (w/w); observation of the cement-bone interfaces using a scanning electron microscope showed that all the cements had directly contacted the bone. At 4 weeks the AWC had bonded to the bone via a 10 micron-thick reactive layer; the width of the layer, in which partly degraded AW-GC particles were seen, became slightly thicker with time. On the other hand, in the HAC- and TCPC-implanted tibiae, some particles on the cement surface were surrounded by new bone and partly absorbed or degraded. The results suggest that the stronger bonding between the inorganic filler and the organic matrix in the AWC cements gave them better mechanical properties. The results also indicate that the higher osteoconductivity of AWC was caused by the higher reactivity of the AW-GC powder on the cement surface.
Modifications of the molluscan feeding apparatus have long been recognized as a crucial feature in molluscan diversification, related to the important process of gathering energy from the environment. An ecologically and evolutionarily significant dichotomy in molluscan feeding kinematics is whether radular teeth flex laterally (flexoglossate) or do not (stereoglossate). In this study, we use a combination of phylogenetic inference and biomechanical modeling to understand the transformational and causal basis for flexure or lack thereof. We also determine whether structural subsystems making up the feeding system are structurally, functionally, and evolutionarily integrated or dissociated. Regarding evolutionary dissociation, statistical analysis of state changes revealed by the phylogenetic analysis shows that radular and cartilage subsystems evolved independently. Regarding kinematics, the phylogenetic analysis shows that flexure arose at the base of the Mollusca and lack of flexure is a derived condition in one gastropod clade, the Patellogastropoda. Significantly, radular morphology shows no change at the node where kinematics become stereoglossate. However, acquisition of stereoglossy in the Patellogastropoda is correlated with the structural dissociation of the subradular membrane and underlying cartilages. Correlation is not causality, so we present a biomechanical model explaining the structural conditions necessary for the plesiomorphic kinematic state (flexoglossy). Our model suggests that plesiomorphically the radular teeth must flex laterally as they pass over the bending plane as a result of the mechanical restrictions in the flexible but inelastic subradular membrane and close association between subradular membrane and cartilages. Relating this model to the specific character states of the clades, we conclude that lack of flexure in patellogastropods is caused by the dissociation of the subradular membrane and cartilage supports.