Narrow Results

We present a novel “lazy” list-based implementation of a concurrent set object. It is based on an optimistic locking scheme for inserts and removes and includes a simple wait-free membership test. Our algorithm improves on the performance of all previous such algorithms.

We focus on a family of shell elements which are a direct generalization of the shell elements most commonly used in engineering practice. The elements in the family include the effects of the through-the-thickness normal stress and can be employed to couple directly with surrounding media on either surfaces of the shell. We establish the "underlying" mathematical model of the shell discretization scheme, and we show that this mathematical model features the same asymptotic behaviors — when the shell thickness becomes increasingly smaller — as classical shell models. The question of "locking" of the finite element discretization is also briefly addressed and we point out that, for an effective finite element scheme, the MITC approach of interpolation is available.

In this paper, we introduce new finite elements to approximate the Hellinger Reissner formulation of elasticity. The elements are the vector-valued tangential continuous Nédélec elements for the displacements, and symmetric tensor-valued, normal–normal continuous elements for the stresses. These elements do neither suffer from volume locking as the Poisson ratio approaches ½, nor suffer from shear locking when anisotropic elements are used for thin structures. We present the analysis of the new elements, discuss their implementation, and give numerical results.

Much work has been done in the last decade in the related areas of object-oriented programming languages and object-oriented databases. Researchers from both areas now seem to be working toward a common end, that of an object management system, or OMS. An OMS is constructed similarly to an OODB but provides a general purpose concurrent object-oriented programming language as well, complementing the OODB query facilities. In this paper, we will define several different types of object systems (object servers, persistent OOPL’s, OODB’s and OMS’s) in terms of their interfaces and capabilities from the viewpoint of how these support the requirements of cooperative information systems. We will examine the distinguishing features and general architecture of systems of each type in the light of a general model of OMS architecture.

We report a case with locking of the metacarpophalangeal (MP) joint of the thumb in a 15-year-old high school baseball catcher, which was caused by an intra-articular loose body arising from osteochondritis dissecans. The loose body was removed arthroscopically, enabling early return to full MP joint function.

We treated a rare case of locked metacarpophalangeal joint of the little finger due to a hyperextension injury. The mechanism of the occurrence was considered to be closely similar to those that happened in the thumb, and the locking was successfully released by a manual reduction without complication.

We report an unusual case of proximal interphalangeal joint locking of the ring finger due to the neglected flexor digitorum profundus avulsion. Although rare, it should be noted that locking is a potential complication after this injury.

Background: Locking plate fixation is widely used in large long bone fixation and is now available for small “long” bones in the hand. Potential advantages of unicortical locked fixation are reduced risk of over-drilling and therefore reduced risk of damage to surrounding structures and reduced risk of irritation from proud screws. Furthermore, unicortical fixation may be used where bicortical fixation is technically impossible. Our aim was to compare fixation strength of unicortical locked plate fixation with bicortical non-locked fixation in a human cadaveric model, by assessing strength under cyclical loading conditions and load to failure (LTF).

Methods: 16 matched pairs of embalmed and refrigerated human cadaveric metacarpals were randomly allocated to either unicortical locked or bicortical non-locked plate and screw fixation. A transverse osteotomy was made. Fractures were stabilized with 2.0 mm self-tapping locking or cortical screws. Each metacarpal was then loaded with a 3-point cantilever testing using a 100 N cell on an Instron materials testing device, cyclically loading them at 1,000 repetitions of 30 N and 50 N. If there was no visible failure of the fixation from cyclical loading they were then loaded to failure with a 1 kN cell.

Results: There was a significant difference of average LTF between the bicortical non-locking and unicortical locking of 38.07–59.95 N (p < 0.01). However, both groups showed no statistically significant difference when comparing their performance under cyclical loading.

Conclusions: The authors regard unicortical locked fixation as a useful adjunct to standard plating technique.

Locking of metacarpophalangeal (MCP) joints of the thumb may be a consequence of dorsal subluxation from hyperextension injury. The joint is locked in mild hyperextension and cannot flex actively or passively. We report four patients with locked MCP joint of the thumb due to radial sesamoid entrapment after hyperextension or forced flexion injury. All patients had a prominent radial condyle of the metacarpal bone. Three patients had a deformity of the longitudinal groove on which the sesamoid was overlaid. The radial sesamoid was entrapped proximal to the radial condyle which could result in limited extension and hinged flexion of the joint. Excision of the radial sesamoid could release the locked joint. The radial sesamoid should be assessed if the motion of the thumb MCP joint is limited after flexion or extension injury.

Level of Evidence: Level V (Therapeutic)