Deformation of 1-piece metal acetabular components.

The success of metal bearings is dependent on several parameters. The effects of in vivo forces on the deformation of monoblock acetabular components have yet to be determined. The purpose of our study was to assess the amount of deformation with press-fit fixation of 1-piece metal acetabular components. Four manufacturers provided 1-piece metal acetabular components in each size (30 cups). Testing was conducted using a custom vise to simulate press-fit fixation, and measurements were performed with a Mitutoyo Test device (Aurora, Ill). Previously determined in vivo forces were used in the press-fit simulation. All components deformed under simulated in vivo applied loads. Component deformation ranged from 15 to 300 µm. Larger cups with thinner walls to accommodate larger heads had the greatest deformation and often exceeded the range of reported clearances from the manufacturers (76-227 µm).

Reduced articular surface of one-piece cups: a cause of runaway wear and early failure.

BACKGROUND: Despite the clinical success of modern metal-on-metal articulations, concerns with wear-related release of metal ions persist. Evidence suggests metal ion release is related to the effective coverage of the head in the metal shell (the cup's functional articular arc). A recent study suggests a reduced functional articular arc is associated with increased ion release and the arc is a function of component design, size, and the abduction angle. QUESTIONS/PURPOSES: The purposes of this study were to (1) measure the functional articular arc in different sizes of currently available one-piece metal shells from several different manufacturers; and (2) compare the functional articular arc of these one-piece metal shells with the 180 masculine arc of conventional hip arthroplasty acetabular components. METHODS: We calculated the available articular surface arc for 33 one-piece metal cups using measurements of cup depth and internal cup radius. RESULTS: The arc of the articular surface varied among manufacturers and generally decreased with decreasing shell diameter. The mean functional articular arc was 160.5 degrees +/- 3.6 degrees (range, 151.8 degrees -165.8 degrees), which was less than the 180 degrees arc of a conventional acetabular component. CONCLUSIONS: Our data show certain cup designs are at higher risk for failure as a result of the decreased articular surface arc. This, along with analysis of abduction angles, supports the recent findings of bearing failure with vertically placed implants. Care must be taken when implanting these shells to ensure they are placed in less abduction to avoid edge loading and the potential for early bearing failure.

Rapid decline in sputum IL-10 concentration following occupational smoke exposure.

The acute effects of smoke exposure on inflammatory mediators such as interleukin-10 (IL-10), interleukin-8 (IL-8), and tumor necrosis factor-alpha (TNF-alpha) are not well understood. Our study was designed to measure sputum concentrations of these cytokines in firefighters following low-level smoke exposure. At baseline, participating firefighters underwent blood collection, pulmonary function testing, and sputum induction through inhalation of nebulized hypertonic saline. Study participants later performed overhaul of a structural fire, during which time they wore cartridge respirators and were monitored for smoke exposure. Overhaul involves searching for and extinguishing hidden sources of combustion. One hour following overhaul, blood, pulmonary function data, and induced sputum were again collected. IL-10, IL-8, and TNF-alpha concentrations were measured by enzyme-linked immunosorbent assay (ELISA) in sputum supernatant. In 17 firefighters, baseline sputum IL-10 concentrations were 57.0 +/- 56.8 pg/L, and declined to 16.9 +/- 27.2 pg/L following overhaul (p =.02). No significant changes were observed in sputum IL-8 and TNF-alpha concentrations. Forced vital capacity (FVC) declined significantly in study participants following overhaul. Serum concentrations of Clara-cell protein and surfactant-associated protein A increased significantly following overhaul, indicating increased lung permeability. IL-10 concentrations appear to be exquisitely sensitive to smoke, and studies of IL-10 in sputum should control for recent exposure. Reduced suppression of inflammation by IL-10 may be a mechanism by which low-level smoke exposure causes lung injury.

Serum pneumoproteins: a cross-sectional comparison of firefighters and police.

BACKGROUND: Serum pneumoproteins provide a measure of the permeability of the lower respiratory tract, and have shown promise as a biomarker of acute and chronic exposure to respiratory toxicants. METHODS: To evaluate the effects of chronic occupational smoke exposure, 105 firefighters were compared with 44 police controls in a cross-sectional study using spirometry, diffusing capacity of the lung, serum Clara cell protein (CC16), and serum surfactant-associated protein A (SP-A) measurements. RESULTS: There were no significant differences in age, gender, height, spirometry (FVC and FEV(1)), and diffusing capacity between the two groups. Serum SP-A was lower in firefighters (260.1 +/- 121.2 microg/L) than police (316.0 +/- 151.4 microg/L, P = 0.019). Serum CC16 was also lower in firefighters (8.39 +/- 3.11 microg/L) than police (10.56 +/- 4.20 microg/L, P < 0.001), although this difference lost statistical significance when adjusted for confounders. CONCLUSIONS: Firefighters have lower serum concentrations of SP-A than do police. Although the clinical significance of this finding is presently unknown, SP-A deserves further study as a biomarker of toxic exposure to the lower respiratory tract.