Complications from total knee arthroplasty caused by the implanted material are rare, with the exception of polyethylene wear. Descriptions of screw migration into the knee joint cavity are very rare. The authors report intra-articular migration of a polyethylene safety screw in a case of total knee arthroplasty, with sacrifice of the posterior cruciate ligament (TKA Performance; Biomet, Warsaw...

BACKGROUND Studies have suggested that cross-linked polyethylene bearings reduce wear rates from 40% to 100% compared with conventional polyethylene. However, the reduced mechanical properties of highly cross-linked polyethylene have the potential to be a limiting factor in device performance. We reviewed a series of retrieved acetabular liners with a fracture of the superior rim to assess the ...

The paper presents results of the investigation of structure relaxation and thermal properties of PE-80 and PE-100 polyethylene hot-tool butt welds. It was found that a weld with the re-crystallized crystalline structure is formed during the welding of dissimilar types of polyethylene. It is shown that within a long period (1 year) the relaxation occurs not only in amorphous but also in the cry...

15.

We construct a Π2 enumeration degree which is a strong minimal cover.

It has been known for more than 40 years that there are posets with planar cover graphs and arbitrarily large dimension. Recently, Streib and Trotter proved that such posets must have large height. In fact, all known constructions of such posets have two large disjoint chains with all points in one chain incomparable with all points in the other. Gutowski and Krawczyk conjectured that this feat...

An old question of Yates as to whether all minimal degrees have a strong minimal cover remains one of the longstanding problems of degree theory, apparently largely impervious to present techniques. We survey existing results in this area, focussing especially on some recent progress.

A polyethylene polymer-based obstetrical lubricant [ a] has been used to facilitate successful delivery of numerous foals. However, this study has demonstrated that the polyethylene polymer is rapidly absorbed from the peritoneal cavity and that it causes an acute, fatal toxicity. Thus, extreme caution should be employed by surgeons if a mare requiring cesarean section has had large volumes of ...

Molecular dynamic simulations of the thermal degradation of polyethylene were used to identify factors which might be effective in reducing polymer flammability by promoting the formation of a residual char. Computer movies of the calculated trajectories indicate that cross-linked polymers, such as those obtained from exposure of polyethylene to ionizing radiation, will undergo further cross-li...