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Excessive local contact stress is implicated as an important factor in the initiation of the loosening process after total joint arthroplasties. A reduced-modulus acrylic bone cement, which decreases the bone-cement interface stresses, was developed to test this hypothesis. The formulation consists of butylmethacrylate beads, having a glass transition temperature of 27 degrees C, in a methylmethacrylate matrix. This cement, polybutylmethylmethacrylate (PBMMA), has an elastic modulus one-eighth that of standard PMMA bone cement, 0.27 vs. 2.1 GPa, at body temperature. In vivo use in a pilot study using the sheep total hip arthroplasty model shows a reduction in the rate of loosening of femoral components when compared both radiographically and mechanically with PMMA controls.

Based on experience with three cases of endobronchial non-Hodgkin's lymphoma and a review of cases previously reported, two patterns of lymphomatous involvement of airways are described. The Type 1 pattern is characterized by diffuse submucosal infiltrates occurring in the presence of intra- and extrathoracic lymphoma. In Type 2 cases, central airways are involved by a solitary mass in the absence of clinically apparent systemic lymphoma. The clinical-radiologic picture is characterized by signs of pneumonitis in Type 1 cases, while in Type 2 cases, signs of airway obstruction uniformly occur.