Deformation of press-fitted metallic resurfacing cups. Part 1: Experimental simulation.

The interference press fit of a metallic one-piece acetabular cup employed for metal-on-metal hip resurfacing procedures was investigated experimentally under laboratory conditions in the present study, in particular regarding the cup deformation. Tests were carried out in cadavers as well as polyurethane foams of various grades with different elastic moduli to represent different cancellous bone qualities. The cadaver test was used to establish the most suitable configuration of the foam model representing realistic support and geometrical conditions at the pelvis. It was found that a spherical cavity, with two identical areas relieved on opposite sides, was capable of creating a two-point pinching action of the ischeal and ilial columns on the cup as the worst-case scenario. Furthermore, the cup deformation produced from such a two-point loading model with a grade 30 foam was similar to that measured from the cadaver test. Therefore, such a protocol was employed in subsequent experimental tests. For a given size of the outside diameter of the cup of 60 mm, the cup deflection was shown to be dependent largely on the cup wall thickness and the diametral interference between cup and prepared cavity at implantation. For a relatively thin cup with a wall thickness between 2.3 mm (equator) and 4 mm (pole) and with a modest nominal diametral interference of 1 mm, which corresponds to an actual interference of approximately 0.5 mm, the maximum diametral cup deflection (at the rim) was around 60 microm, compared with a diametral clearance of 80-120 microm between the femoral head and the acetabular cup, generally required for fluid-film lubrication and tribological performances. Stiffening of the cup, by both thickening and lateralizing by 1 mm, reduced the cup deformation to between 30 and 50 microm with actual diametral interferences between 0.5 and 1 mm.

Campylobacter coli - an important foodborne pathogen.

OBJECTIVES: Campylobacters are the most common bacterial cause of infectious intestinal disease (IID) in temperate countries. C. jejuni is the predominant cause of campylobacter IID, but the impact of other, less prevalent species has largely been ignored. Here, we present estimates of the burden of indigenously acquired foodborne disease (IFD) due to Campylobacter coli, the second most common cause of human campylobacteriosis. METHODS: Data from surveillance sources and specific epidemiologic studies were used to calculate the number of illnesses, presentations to general practice (GP), hospital admissions, hospital occupancy and deaths due to indigenous foodborne C. coli IID in England and Wales for the year 2000. RESULTS: We estimate that in the year 2000, C. coli accounted for over 25,000 cases of IFD. This organism was responsible for more than 12,000 presentations to GP, 1000 hospital admissions, nearly 4000 bed days of hospital occupancy and 11 deaths. The cost to patients and the National Health Service was estimated at nearly pound 4 million. CONCLUSIONS: Although C. coli comprises a minority of human campylobacter disease, its health burden is considerable and greater than previously thought. Targeted research on this organism is required for its successful control.

General outbreaks of infectious intestinal disease (IID) in hospitals, England and Wales, 1992-2000.

Between 1992 and 2000, 26.6% (1,396/5,257) of all general outbreaks of infectious intestinal disease (IID) reported to the Public Health Laboratory Service (PHLS) Communicable Disease Surveillance Centre (CDSC) occurred in hospitals. Over 29,000 patients and staff were affected and the mortality risk was higher than for outbreaks in other settings [relative risk 2.00 (95% CI: 1.52-2.63) P<0.001]. Person-to-person spread was the predominant mode of transmission. The mortality risk was highest in foodborne disease outbreaks [relative risk 3.22 (95% CI: 1.41-7.36); P=0.003]. Most outbreaks occurred between November and April. The pathogens most frequently reported were Norwalk-like virus (NLV) (54%) and Clostridium difficile (12.6%). These findings emphasize the public health importance of outbreaks of IID in hospitals, especially during the winter when pressures on hospitals are at their height.