Pseudomeniscus following total knee arthroplasty as a cause of persistent knee pain.

Persistent pain following total knee arthroplasty is an uncommon complication that may have any of several causes. In the case reported here, a patient who had undergone total knee arthroplasty developed a symptomatic pseudomeniscus that was successfully treated by arthroscopic debridement. Histopathologic analysis of the pseudomeniscus revealed a unique fibrocartilaginous structure, which may give insight into its pathogenesis. Symptomatic pseudomeniscus is one of several postoperative complications of total knee arthroplasty for which arthroscopy may be indicated.

Nonlinear prism coupling with nonlocality.

The characteristics of prism coupling of finite-width beams into nonlinear waveguides composed of media with diffusive nonlinearities (thermal, etc.) are calculated by including a one-dimensional diffusion equation for the nonlocal nonlinearity. The resulting longitudinal feedback leads to bistability, and the threshold value for the minimum diffusion length varies inversely with the angular detuning.

The lysosomal toxicity of aminoglycosides: a morphometric approach.

Lysosomes of kidney proximal tubule cells have been described as an early target involved in aminoglycoside-induced nephrotoxicity. These organelles concentrate these molecules and are overloaded with osmiophilic lamellar material. Biochemical alterations of lysosomes have already been described. In this study 6 aminoglycosides were given i.p. at the doses of 10 and 50 mg/kg for 4-7-15 days. A morphometric study of the lysosomal system of rat kidney proximal tubules is described first using Delesse's principle on electron micrographics. After aminoglycoside treatment, lysosomal volume rose from 3.3% in controls up to 10% or more of the cell volume. Concomitantly lysosomes were overloaded with myeloid bodies up to 50% or more of their own volume. Individual measurements of lysosome sections were performed on micrographics: perimeter and area. Size distributions were compared to each other using the Kolmogorov-Smirnov statistical test. Since the observed distribution could not be compared with a normal, Poisson, or any other theoretical distribution, the size distribution of perimeters has been successfully likened to a sum of individual normal subpopulations, the means of which follow a geometrical progression of rate square root 2 from a constant value of 1.23 micron, with standard errors of 15% of their respective mean value. When converted to membrane area values the progression rate becomes 2 and suggests fusion of identical size lysosomes during their intracellular life.