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The analysis of the bonding interface between hip prostheses and bone after functional use in animals was carried out. Scanning electron microscopy (SEM) with energy dispersive analysis (EDX), and Auger electron spectroscopy were used to evaluate the bonding interface. Various methods of postsacrifice sample preparation were used to evaluate the effect of such different methods on the analysis of the bonding interface. Comparison of the results with several rat tibia implant experiments is also presented.

The quantity of protein and carbohydrate comprising the matrix of calcium oxalate monohydrate (COM) renal stones was found to decrease with distance from the surface of the stone. The average organic concentration of stones 3 to 30 mm in diameter ranged from 5.7% at the surface to 2.7% at the core. This concentration gradient suggests matrix involvement in a "growth front" on stone surfaces with migration of organic material from the "older" interior. The matrix distribution was not readily correlated with density variations or with the presence of hydroxyapatite or calcium oxalate dihydrate. Surface matrix concentrations were greater than amounts predicted by physical adsorption. Electron microscopy confirmed the presence of the organic-rich surface layer and also suggested that increase in stone size occurs predominantly by crystal growth with microcrystal aggregates as growth centers.

Spontaneous or Induced Atrial Fibrillation. As part of a new effort to develop an implantahle drug infusion pacing system to treat atrial fibrillation, this study examined the effects of rapid intracardiac procainamide infusion in humans with fmcing-induced atrial fibrillation. Twenty patients with atrial fibrillation for '5 mim/tes during an EP study received 500mg of procainamide either via a peripheral venotis infusion (n^5) or directly in the right atrium (n 15).

Tongue motion control results from a complicated series of interactions between multiple tongue muscles. Surgical intervention could possibly affect speech while at the same time producing positive benefits as reduction of retro-palatal collapse. The goal of the study was to represent the tongue as a quantifiable structured geometry specifying the various muscle regions as locally varying directional fields and use this model to determine the affect of altered muscle structure on tongue motion. A quantitative computer simulation of the human tongue was constructed around a finite element model. Muscle morphology was generated from segmentation of images from the Visible Human project and MRI images. The extrinsic and intrinsic muscles were represented as directional fields at a large number of elements. Muscle contraction was produced as a stress controlled region of a locally varying directional field. A Lagrangian formulation of an Ogden hyperelastic material was used for the pass...

Biomaterial implants frequently potentiate infections in patients, yet rarely have we considered the interactions between bacteria and biomaterials responsible for this. There is extensive literature concerning suture materials of various types and a few studies comparing porous and solid implants. We have developed a simple, relatively atraumatic model for comparing rates of infection surrounding a biomaterial implant in paired single animal observations. Statistically significant differences between silicone and fluorocarbon implants and between silicone and bioglass implants are demonstrated. The relatively greater rate of infection with silicones is consistent with a previous clinical study. The further use of this model for evaluation of material-surface interfacial effects is proposed.