Cost Efficacy of Methicillin-Resistant Staphylococcus aureus Decolonization With Intranasal Povidone-Iodine.

BACKGROUND: With increasing rates of virulent drug resistant organisms, MRSA (methicillin-resistant Staphylococcus aureus) decolonization has been demonstrated to decrease infection rates. Recent research has shown the antiseptic povidone-iodine to be equally effective and potentially cost saving compared to intranasal mupirocin. This study's purpose is to evaluate the incidence of MRSA colonization in a more rural community-based population, rates of infection on a mupirocin decolonization protocol, and develop a cost analysis model to compare costs of utilizing povidone-iodine. METHODS: Utilizing over 4 years of data, the incidence of MRSA decolonization of consecutive total knee and hip arthroplasties, as well as the rates of infection of patients uncolonized, colonized with successful decolonization, and unsuccessful decolonization were evaluated. Utilizing these data, cost data, and known infection rate utilizing povidone-iodine decolonization, a cost analysis model was developed. RESULTS: Of the 5584 cases with MRSA data at a single institution, only 3.5% tested positive for intranasal MRSA. Of those patients, 69% were successfully decolonized. Of the 3864 cases with infection data, 21 sustained a surgical site infection within 90 days (0.54%). Of these patients, all tested negative for intranasal MRSA initially and therefore did not undergo the decolonization protocol. The cost analysis predicts a potential savings of $74.72 per patient at our institution to use a global intranasal povidone-iodine protocol prior to total joint arthroplasty. CONCLUSION: Even with a lower incidence of MRSA than typically reported, utilization of intranasal povidone-iodine would potentially save $74.42 per patient.

Distal-third clavicle fracture fixation: a biomechanical evaluation of fixation.

BACKGROUND: Approximately 25% of distal clavicle fractures are unstable. Unstable patterns have longer times to union and higher nonunion rates. Stable restoration of the distal clavicle is important in decreasing the nonunion rate in distal clavicle fractures. The purpose of this study was to biomechanically compare operative constructs for the treatment of unstable, comminuted distal-third clavicle fractures in a cadaveric model using a locking plate and coracoclavicular reconstruction. We hypothesized that the combination of coracoclavicular reconstruction and a distal clavicle locking plate is biomechanically superior to either construct used individually. MATERIALS AND METHODS: An unstable distal clavicle fracture was created in 21 thawed fresh-frozen cadaveric specimens. The 21 specimens were divided into 3 treatment groups of 7: distal-third locking plate, acromioclavicular (AC) TightRope (Arthrex, Naples, FL, USA), and distal-third locking plate and AC TightRope together. After fixation, each specimen was cyclically tested with recording of displacement to determine the stiffness and stability of each construct, followed by load-to-failure testing in tension and compression to determine the maximum load. RESULTS: The combined construct of the locking distal clavicle plate and coracoclavicular reconstruction resulted in increased stiffness, maximum resistance to compression, and decreased displacement compared with either construct alone. CONCLUSION: Greater fracture stability was achieved with the combination of the AC TightRope and locking clavicle plate construct than with either alone, suggesting a possibility for increased fracture-healing rates.

Effect of intra-articular pressurization associated with arthroscopy on the immature physis: investigation in an animal model.

BACKGROUND: Despite the increased use of arthroscopy in pediatric orthopaedics, there is a paucity of data regarding the potential long-term effects of this procedure on the immature physis. The purpose of this study was to test the hypothesis that elevated intra-articular pressures used during arthroscopic surgery do not result in growth disturbances or morphologic alterations in the epiphyseal plate. METHODS: Twenty-seven 6-week-old skeletally immature New Zealand white rabbits were divided into experimental (n=21) and control groups (n=6). In the experimental group, a hydraulic pump was used to pressurize 1 randomly assigned knee joint per rabbit to intra-articular pressures of 120 mm Hg for 2 hours. In the control group, rabbits received a sham intervention. All rabbits were killed at 6 months of age (skeletal maturity), and their tissues were evaluated grossly, radiographically, and histologically. Data collection included gross measurements (femur and tibia lengths, evaluation of varus/valgus angulation, and knee joint range of motion) and histologic analyses to determine whether morphologic changes were present in the articular cartilage or physis. Confidence intervals were used to test for statistical equivalence. RESULTS: The pressurized and control groups had statistically equivalent gross measurements. No significant articular cartilage or physeal lesions were identified in histologic sections or radiographic studies. CONCLUSION: This study provided no evidence that arthroscopic pressurization of the knee joint to 120 mm Hg for 2 hours significantly affected physeal growth in a skeletally immature rabbit model. CLINICAL RELEVANCE: This study provides the first direct evidence that arthroscopic pressurization of immature joints has no clinically significant adverse long-term effects. Therefore, novel uses of arthroscopy in pediatric patients should be explored without undue concern with regard to premature physeal closure.

Gd-DTPA-enhanced cranial MR imaging in children: initial clinical experience and recommendations for its use.

Gd-DTPA was administered prospectively to 65 consecutive children (ages 1 day to 18 years, mean 9.6 years) to document its utility and safety for routine cranial MR imaging. Precontrast T1- and T2-weighted scans and postcontrast T1-weighted scans were obtained. No complications or significant adverse reactions were encountered. Contrast enhancement was seen in 14 lesions from seven patients, but each of these patients had some abnormality also present on precontrast images. Contrast enhancement was thought to be extremely helpful in characterizing four primary tumors and moderately helpful in characterizing four other lesions. Absence of contrast enhancement was helpful in clarifying the nature of abnormalities seen in an additional four patients. Gd-DTPA may be used safely in children, but this study does not support its routine administration. The highest incremental diagnostic yield from its use will likely be among patients with suspected neoplasms or inflammatory diseases and among those requiring further characterization of lesions seen on precontrast scans.

Radioiodide imaging of struma cordis.

This is the first reported case in which struma cordis was demonstrated with radionuclide imaging. A 56-year-old white woman underwent surgical excision of a benign intracardiac thyroid mass (struma cordis). Subsequent radionuclide imaging with I-123 sodium iodide and Tc-99m labeled red blood cells demonstrated a normal cervical thyroid gland as well as a focus of activity in the mediastinum consistent with intracardiac thyroid.

Association of the epidermal growth factor receptor kinase with the detergent-insoluble cytoskeleton of A431 cells.

The epidermal growth factor receptor (EGF-R) on human epidermoid carcinoma cells, A431, was found to be predominantly associated with the detergent-insoluble cytoskeleton, where it retained both a functional ligand-binding domain and an intrinsic tyrosine kinase activity. The EGF-R was constitutively associated with the A431 cytoskeleton; this association was not a consequence of adventitious binding. The EGF-R was associated with cytoskeletal elements both at the cell surface, within intracellular vesicles mediating the internalization of the hormone-receptor complex, and within lysosomes. The EGF-R became more stably associated with cytoskeletal elements after its internalization. The cytoskeletal association of the EGF-R was partially disrupted on suspension of adherent cells, indicating that alteration of cellular morphology influences the structural association of the EGF-R, and that the EGF-R is not intrinsically insoluble. Cytoskeletons prepared from EGF-treated A431 cells, when incubated with gamma-32P-ATP, demonstrated enhanced autophosphorylation of the EGF-R in situ as well as the phosphorylation of several high molecular weight proteins. In this system, phosphorylation occurs between immobilized kinase and substrate. The EGF-R and several high molecular weight cytoskeletal proteins were phosphorylated on tyrosine residues; two of the latter proteins were phosphorylated transiently as a consequence of EGF action, suggesting that EGF caused the active redistribution of the protein substrates relative to protein kinases. The ability of EGF to stimulate protein phosphorylation in situ required treatment of intact cells at physiological temperatures; addition of EGF directly to cytoskeletons had no effect. These data suggest that the structural association of the EGF-R may play a role in cellular processing of the hormone, as well as in regulation of the EGF-R kinase activity and in specifying its cellular substrates.

Nerve growth factor- and epidermal growth factor-stimulated phosphorylation of a PC12 cytoskeletally associated protein in situ.

Nerve growth factor (NGF) and epidermal growth factor (EGF) produce stable alterations in PC12 cells that persist in the detergent-insoluble cytoskeleton, resulting in the phosphorylation of a 250,000-mol-wt cytoskeletally associated protein in situ. Treatment of PC12 cells with NGF or EGF, followed by detergent lysis of the cells and incubation of the resulting cytoskeletons with gamma-32P-ATP, permitted detection of hormonally stimulated, energy-dependent events, which result in the enhanced phosphorylation of a cytoskeletally associated protein as an immediate consequence of receptor occupancy. These events were elicited only upon treatment of intact cells at physiological temperatures. The NGF- and EGF-stimulated events occurred rapidly; however, they were a transient effect of hormone action. NGF and EGF were found to act through independent mechanisms to stimulate the in situ phosphorylation of the 250,000-mol-wt protein, as the effects of NGF, but not EGF, were blocked by methyltransferase inhibitors. The 250,000-mol-wt protein was phosphorylated on serine and threonine residues in response to both NGF and EGF although in somewhat different proportions. The data suggest that the hormone-stimulated labeling of the 250,000-mol-wt protein may be the result of either the direct activation of a protein kinase, the redistribution of the kinase relative to its substrates as a consequence of hormone action, or the coincident occurrence of these events.

The development distribution of vimentin in the chick retina.

The developmental distribution of vimentin was localized in chick retina using light and electromicroscopic immunohistochemical techniques. From embryonic day 4 (E4) to E8 vimentin was present in cells throughout the retina. By E10 vimentin immunoreactivity was restricted to Müller cells. In tissue culture of chick neural retina vimentin was found to be restricted to flat cells that are thought by others to be derived from Müller cells. Neurons in culture did not contain vimentin.

The effects of chemical cross-linking agents on calcium-induced structural changes in skinned muscle fibers. Origin within thick filaments detected by optical diffraction methods.

We have reported earlier (Sabbadini, R.A., Rieser, G.D. and Paolini, P.J. (1979) Biochim. Biophys. Acta 578, 526-533) that physiological levels of calcium (pCa 6.95-5.49) can produce structural changes in thick filaments which are detectable as an intensity loss of the first-order optical diffraction lines from chemically skinned skeletal muscle fibers stretched beyond myofilament overlap. We now show that the calcium-induced intensity decrease results from structural changes within, rather than between, thick filaments. Glycerinated, detergent-treated fibers from frog semitendinosus muscle were incubated in 1-10 mM concentrations of dimethylsuberimidate (DMS), dithiobis(succinimidylpropionate) (DTSP) or dimethyl-3,3'-dithiobispropionimidate (DTBP) for 4 h. These substances are homobifunctional lysine-modifying cross-linking reagents known to restrict movement of S-1 heads and limit changes in the association of myosin rods within the core of the thick filament without affecting interfilament lattice spacing. Diffraction patterns from cross-linked cells in relaxing solution were identical to those in control cells, but Ca2+ (pCa 5.49) totally failed to produce the typical 50-70% attenuation of first-order line intensity. Cleavage of the disulfide bond in DTBP-treated cells with dithiothreitol fully restored the Ca2+ sensitivity. Lysine group modification with methylacetimidate, a monofunctional lysine modification reagent equivalent to DMS, did not block the Ca2+ sensitivity. We observed that intensity reductions can also be produced by numerous other agents and mechanisms, such as nonionic polymeric solutions of polyvinylpyrrolidone, which reduces the lattice spacing, and alkaline pH, which probably displaces the S-1 heads from a resting position close to the thick filament surface. However, the prevention of the Ca2+ effect by cross-linkers indicates that intrafilament rather than interfilament changes in structure are responsible for the light diffraction intensity decrease accompanying activation.

Calcium-induced structural changes in chemically skinned muscle fibers. Detection by optical diffractometry.

The intensity of the first order diffraction line produced by chemically skinned muscle fibers was detected by a self scanning photodiode array and minicomputer system. Line intensity was observed to decrease in fibers stretched to zero filament overlap when subjected to calcium-EGTA buffers in the physiological pCa range. Calcium dependent intensity decreases were not observed for myosin extracted fibers indicating that the thick filament proteins may be the source of the calcium effect seen in non-extracted fibers. These results can be interpreted in terms of calcium dependent effects on thick filament disordering which are not dependent upon cross bridge formation.

Sarcomere motion in isolated cardiac cells.

Computerized image-analysis techniques have been employed to examine the sarcomere dynamics of isolated mammalian cardiac myocytes. The cells were prepared by perfusion of adult rabbit hearts with hyaluronidase-collagenase solutions; they exhibited phasic contractions in the presence of 10(-6) M Ca2+. The dissociated cells were visualized by phase microscopy and a video camera interfaced in a minicomputer. Digitized cell images were processed by an algorithm utilizing signal averaging and contrast enhancement to yield data showing individual sarcomere position and shortening vs. time, so that patterns of sarcomere activation could be observed in spontaneously contracting cells. Compared to records of whole-cell shortening and of striation displacement, computerized image analysis provided a much more faithful indication of time course and sequence of sarcomere shortening. Spontaneously contracting cells showed sequential sarcomere shortening beginning at one end and propagating longitudinally with a constant velocity, typically at 100--150 micron/s for beat rates of 40 min-1. Velocities of initial sarcomere shortening appeared to increase with elevated Ca2+. These observations are consistent with a regenerative mechanism of calcium-induced calcium release.