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The thickness of the cement mantle around the femoral component of total hip replacements is a contributing factor to aseptic loosening and revision. Nevertheless, various designs of stems and surgical tooling lead to cement mantles of different thicknesses. Opinion is divided on whether a thick mantle enhances implant longevity. This study investigates the effect of cement mantle thickness on accumulated damage in the cement, and how this is influenced by the presence or absence of a proximal collar and on whether the stem—cement interface remains bonded. Three-dimensional finite element simulations incorporating creep and non-linear damage accumulation were performed to investigate cracking in the cement mantles around Stanmore Hips under physiologically informed stair-climbing and gait loads. Cement mantle thickness, stem—cement interfacial bonding, and collar design were varied to assess the interactive effects of these parameters. In all cases, damage levels were three to six times higher when the stem—cement interface remained bonded. Cement mantle thickness had little effect on cement damage accumulation around debonded collared stems but was critical in both bonded and collarless cases, where a thicker mantle reduced cement cracking. Damage around a smooth debonded stem with a collar is thus much less sensitive to cement thickness than around bonded or collarless stems.

The purpose of this study was to determine whether the surgical approach to the femoral neck during total hip arthroplasty affects the quality of femoral cement mantle in terms of thickness and defects, both of which have been implicated in the development of aseptic loosening. A retrospective radiological review of 50 Stanmore Hip femoral stems inserted using the anterior approach and 50 inserted via the posterior approach was performed, with analysis by zone of cement mantle thickness and number of defects.This study demonstrates that the anterior approach is associated with an increase in the frequency of deficiencies in the cement mantle. We recommend that surgeons using the anterior approach are wary of this increased risk and adopt measures, such as the use of distal centralisers, to minimise its occurrence.

The objective of this paper is to determine how residential solid waste has been and could be disposed of or reused in metropolitan regions. By means of optimization techniques, the authors examine the economic efficiency of landfilling, energy and materials recovery, and waste-transportation technologies at centralized and dispersed sites. The results indicate that dry-fuel technology is the most efficient system for the near future. Pyrolysis, incineration, and landfilling are less efficient systems in metropolitan regions which are running out of inexpensive landfill space. Northern New Jersey is used as a case study.