Complex Joints Research Articles

Osteoid Osteoma

Occasionally, osteoid osteoma can be difficult to radiographically differentiate from osteomyelitis. The precise localization of the nidus of an osteoid osteoma often can be difficult using nothing more than conventional radiographs. In a series of 35 patients, a radionuclide and double density sign facilitated localization of the nidus, confirmed the diagnosis, and aided the surgeon in excision biopsy. This series of cases demonstrates how computed tomography (CT) scanning can more precisely localize the nidus in areas deep in complex joints such as the hip. Fifteen cases of osteoid osteoma were studied with Tc-99m-MDP radionuclide bone scan. Each one exhibited the double density sign. Seven of these patients had CT scans in addition for further localization of the nidus. All were excised with accurate localization of the nidus, and thereby reduced morbidity and postoperative recovery time.

Centrode patterns in the lumbar spine. Baseline studies in normal subjects.

Segmental spinal instability is a known cause of back pain, but no method of accurately quantifying instability exists. The movement of complex joints with rotational and translational components (such as the lumbar motion segment) is tracked by a pathway of instantaneous centers of rotation, or a centrode. Instability, ie, excessive and/or erratic movement, is reflected by increased centrode length in cadaver studies. This study describes an in vivo method that precisely determines the centrode pattern and reports the results for 21 normal male volunteers who were studied at the L4-5 and L5-S1 levels. Each volunteer underwent lateral radiographs of the lumbar spine. High speed films were used and six positions, from full extension to full flexion, were recorded. Acetate tracings and contour matching techniques recorded the relative positions of the vertebral bodies on each film. Multiple tracings of each radiograph, combined with a digitizer and computer, were used to improve precision in the calculated centrode patterns. Centrode lengths measured 43.7 mm and 55.9 mm, respectively, for the L4-5 and L5-S1 levels. This study demonstrates that precise centrode pattern analysis for sagittal plane motion of the lumbar spine is possible in vivo. Studies are under way to determine whether this technique will be useful as a clinical test in diagnosing early segmental instability of the lumbar spine in patients with low-back pain.

Cast Steel Nodes - Their Manufacture and Advantages to Offshore Structures

Summary This paper outlines an extensive development program designed to prove the use of cast steel nodes program designed to prove the use of cast steel nodes as alternatives for the welded nodes now used in the fabrication of oil production platforms. The manufacturing procedures and properties obtained are discussed, and the major advantages-increased fatigue life and design flexibility - are highlighted. Introduction The exploitation of offshore oil reserves has fostered the development and growth of industries associated with the design and manufacture of very large steel or reinforced concrete structures. Forecasts indicate that the fixed production platforms of the future are more likely to be built as piled steel structures or steel gravity platforms.Steel jacket structures for use in the North Sea currently are built to comply with draft standards or the rules of a certification authority. These instructions are based largely on extrapolation of experience with smaller structures located in less hostile waters, and the final specifications for new platforms often include substantial changes based on platforms often include substantial changes based on the availability of new data from current research programs. An analysis of these research activities programs. An analysis of these research activities shows that the most uncertainty concerning the manufacture and use of welded steel structures is related to (1) the quality and integrity of the welded joint, (2) the fatigue and corrosion fatigue resistance of the fabricated node, and (3) node design parameters and, in particular, the analysis of the high parameters and, in particular, the analysis of the high hot-spot stress concentration.Oil exploitation in deeper water requires the design and fabrication of larger structures. In these circumstances, plate thicknesses increase dramatically to provide the necessary stiffness, or complex joints with internal stiffeners are required. Either alternative creates problems during fabrication, making it essential to stress-relieve the node joint.British Steel Corp., recognizing the difficulties encountered during the manufacture and use of large complex node joints for fixed production platforms, pursued the development of cast steel nodes suitable pursued the development of cast steel nodes suitable for use either as direct replacements for the conventional welded node or, where circumstances permit, as part of a total structure designed to permit, as part of a total structure designed to optimize the use of castings. This development was supported by a grant from the U.K. DOE.This paper presents details of the development program, manufacturing principles, and, wherever program, manufacturing principles, and, wherever possible in quantitative terms, the relative merits of a possible in quantitative terms, the relative merits of a cast and weld fabricated structure. Material Development It is unrealistic to expect the offshore design engineer - with his wealth of experience and, therefore, confidence in the design of welded offshore structures - to be immediately enthusiastic about the benefits offered by cast steel nodes. The advantages offered in terms of improved fatigue resistance, cost, and possible weight savings have to be shown to far outweigh the potential risks involved. Because of this, it is likely that offshore operators initially will consider only the limited use of cast nodes, accepting a minimum departure from conventional methods and standards.For these reasons, it was decided to concentrate on the development of cast nodes that could be substituted simply in a structure designed as a welded fabrication. Such a substitute node would be recontoured to take advantage of the benefits of castings, achieving a significant reduction in stress concentration factor and improved fatigue performance, hopefully without a significant increase in performance, hopefully without a significant increase in node weight. JPT P. 1999

Functional morphology of the prosoma of Baltoeurypterus tetragonophthalmus (Fischer) (Chelicerata: Eurypterida)

AbstractThe prosomal morphology ofBaltoeurypterus tetragonophthalmus(Fischer) from the Baltic Silurian is redescribed and reconstructed. The first eurypterid labrum and new secondary sexual characters ofBaltoeurypterusare described. The radially-arranged coxae ofBaltoeurypteruswere capable of adduction and abduction for food mastication, but not promotor-remotor movements for locomotion. Joint diagrams are presented for the first time for an extinct arthropod. Promotion and remotion of the limbs occurred about subvertical trochanteral pivots, as in all other chelicerates except xiphosurans.Baltoeurypterusprobably walked in a “slow” gait; a method of choosing possible gaits for extinct arthropods is outlined. Swimming inBaltoeurypteruswas effected by means of a rowing action of the posterior limb pair, which is provided with complex joints for collapsing the paddle during the recovery stroke. The limb arrangement and joint mechanisms ofBaltoeurypterusare intermediate between those of the xiphosurans and the arachnids. It is possible that a sister relationship exists between the eurypterids and some arachnid groups, which would render Merostomata and Arachnida unnatural assemblages.

METGLAS MBF-20A

Abstract METGLAS MBF-20A is a general-purpose, nickel-base filler metal well suited for brazing stainless steels and heat-resisting nickel alloys. It is supplied as ductile, flexible metallic-glass foil that can be stamped or cut into precision preforms to fit complex joints; it acts as its own shim. It is 100% metal, 100% dense and contains no organic binders to remove by baking. At elevated temperatures in brazed joints it has an outstanding combination of strength, fatigue properites and resistance to oxidation and corrosion. It is used in the aerospace industry for joining internal assemblies. This datasheet provides information on composition, physical properties, microstructure, tensile properties. It also includes information on heat treating. Filing Code: Ni-262. Producer or source: Allied Chemical Corporation.

On the mechanism of the spine

In examining the structure of the vertebrae in different animals, the author was particularly struck with the mechanism of the spine and spinal canal in birds, by which great motion is gained in the neck without injury to the spinal marrow. The cervical vertebrae in birds vary from 9 to 24 in number; they differ considerably from each other, and are articulated by complex joints, in some respects resembling the articulation of the olecranon with the humerus in the human subject, but admitting also of lateral motion. The varying positions of the articulating surfaces are favoured by the interposition of a cartilage, adapted to the surface of each bone, and inclosed between reduplications of sinovial membrane; each joint is thus double, and resembles the articulation of the human lower jaw. The canal of each vertebra is contracted in the centre, and enlarges above and below. In front it is closed by the bodies of the vertebrae ; but in the skeleton its posterior part is imperfect, being filled up in the recent state by membrane, and protected by the ligamentum nuchae. The author then describes the appearance, on dissection, of the membranes of the spinal marrow, and of the mechanism by which its compression in the various and extensive motions of the neck is prevented; he also adverts to the exact correspondence between the extent of motion permitted, and the size and form of the canal in the human spine, and to some pathological consequences connected with such structure.