Flexural composite oscillators for the measurement of anelastic and elastic properties of solids at frequencies of 1 to 10 kHz.

Longitudinal composite oscillators for measuring internal friction, piezoelectric modulus, and strain modulation effects are usually limited to a frequency range of 30 to 200 kHz. If the same crystals are vibrated in flexure, a longitudinal strain can be introduced with the resonance frequency below 3 kHz while at the same time keeping the inherent high Q of the composite system. This paper develops the theory for the strain amplitude and damping for the flexural composite oscillator made up of two quartz crystals plus specimen and, if appropriate, spacers. This high Q technique of vibrating in flexure has applications for strain modulation and damping experiments.

Tumor necrosis factor monoclonal antibody prevents alterations in leukocyte populations during cardiopulmonary bypass.

Tumor necrosis factor-alpha (TNF-alpha) has been implicated as causing the systemic inflammatory response to cardiopulmonary bypass (CPB) that contributes to the postoperative sequelae of coagulopathy, increased capillary permeability, leukocytosis, fever, and multiple organ dysfunction. To define the role of TNF-alpha on leukocyte populations during CPB, pigs (n = 6) were pretreated with 20 mg TNF-alpha monoclonal murine antibody before normothermic CPB (2 hr) in a blinded prospective randomized study with saline used as a control (n = 6). The leukocyte response to CPB was measured at 10, 30, 60, and 120 min during CPB and at 60 and 120 min after CPB. Repeated measures analysis of variance was performed and the null hypothesis was discarded at the 5% level. The control group displayed the typical leukocyte profile associated with CPB: and initial leukopenia (36% reduction) followed by leukocytosis (11% increase, P = 0.0001). The initial leukopenia was due to a fall in both polymorphonuclear neutrophils (33% reduced, P < 0.05) and monocytes (37% reduced, P < 0.05). In the TNF-alpha monoclonal murine antibody group the total leukocyte profile did not change significantly from baseline, (8.7% reduction to a 16% increase, P = 0.24) nor were there significant changes in populations including neutrophils and lymphocytes. In the treatment group the initial reduction in monocytes was prevented and total circulating monocytes increased during bypass. The experimental data suggest that TNF-alpha may play an important role in the early alterations in leukocyte populations associated with CPB, and TNF-alpha monoclonal murine antibody pretreatment ameliorates the leukocyte response.

Acetabular augmentation in primary and revision total hip arthroplasty with cementless prostheses.

Twenty-four consecutive cementless hip arthroplasties (13 autografts and 11 allografts) have been done in which large bone grafts were used to augment major acetabular deficiencies and have been followed for a minimum of 24 months with a mean of 34 and a maximum follow-up period of 55 months. The autograft augmentations were uniformly successful. Two fixation failures occurred in the allograft group. Considering the extreme deficiency in the acetabulae encountered and the absence of sufficient autograft material in this group of patients, the use of frozen allografts (although less successful in this series) seems justified. Graft resorption as determined by direct roentgenographic measurements was less than might be expected but may be a manifestation of the short-term follow-up period. Resorption, however, was greater in the allograft group and, when marked, was associated with fixation failure.

Cement composite delivery system.

Several new and innovative techniques have recently been introduced that purport to increase the strength of polymethyl methacrylate bone cement. One of these concepts is the use of carbon and polymer fibers to form a cement composite. Bone cement composites usually 1% fiber, are very difficult to use clinically. The composite is very sticky and viscous, which precludes effective hand packing or the use of conventional delivery systems. A new delivery system for very viscous materials is presented and examples of in vitro application are shown.

Metal allergy, metal implants and fracture healing.

The rabbit tibia was used as a model to study the effects of metal sensitivity reactions on the healing of fractures. Animals were injected with nickel chloride in Freund's complete adjuvant to cause sensitivity, and fractures were stabilized with 316L stainless steel intramedullary rods and followed for 16 weeks. A control group received no injections. The response was evaluated biomechanically with torsional testing at sacrifice, radiologically by examining the roentgenograms for evidence of loosening, and histologically. The results demonstrated a slight decrease in strength, a moderate increase in resorption and a significant decrease in cellularity and new bone formation in the sensitive animals as compared to control. These results are consistent with a reaction of comparatively short duration.