OBJECTIVE Optimal strategies for fixation in the osteoporotic lumbar spine remain a clinical issue. Classic transpedicular fixation in the osteoporotic spine is frequently plagued with construct instability, often due to inadequate cortical screw–bone purchase. A cortical bone trajectory maximizes bony purchase and has been reported to provide increased screw pullout strength. The aim of the current investigation was to evaluate the biomechanical efficacy of cortical spinal fixation as a surgical alternative to transpedicular fixation in the osteoporotic lumbar spine under physiological loading. METHODS Eight fresh-frozen human spinopelvic specimens with low mean bone mineral densities (T score less than or equal to –2.5) underwent initial destabilization, consisting of laminectomy and bilateral facetectomies (L2–3 and L4–5), followed by pedicle or cortical reconstructions randomized between levels. The surgical constructs then underwent fatigue testing followed by tensile load to failure pullout testing to quantify screw pullout force. RESULTS When stratifying the pullout data with fixation technique and operative vertebral level, cortical screw fixation exhibited a marked increase in mean load at failure in the lower vertebral segments (p = 0.188, 625.6 ± 233.4 N vs 450.7 ± 204.3 N at L-4 and p = 0.219, 640.9 ± 207.4 N vs 519.3 ± 132.1 N at L-5) while transpedicular screw fixation demonstrated higher failure loads in the superior vertebral elements (p = 0.024, 783.0 ± 516.1 N vs 338.4 ± 168.2 N at L-2 and p = 0.220, 723.0 ± 492.9 N vs 469.8 ± 252.0 N at L-3). Although smaller in diameter and length, cortical fixation resulted in failures that were not significantly different from larger pedicle screws (p > 0.05, 449.4 ± 265.3 N and 541.2 ± 135.1 N vs 616.0 ± 384.5 N and 484.0 ± 137.1 N, respectively). CONCLUSIONS Cortical screw fixation exhibits a marked increase in mean load at failure in the lower vertebral segments and may offer a viable alternative to traditional pedicle screw fixation, particularly for stabilization of lower lumbar vertebral elements with definitive osteoporosis.

Vancomycin is the first-line therapy for methicillin-resistant

Vancomycin and daptomycin MICs from 161 isolates of methicillin-resistant Staphylococcus aureus (MRSA)were compared using commercial and in-house broth microdilution, Etest, and common automated methods. Vancomycin Etest MICs were higher than those of other methods, whereas the MICs for daptomycin testing were comparable. Vancomycin MICs vary depending on the testing methodology.Vancomycin is the gold standard for the treatment of serious infections due to methicillin-resistant Staphylococcus aureus (MRSA). Recent guidelines from the Infectious Diseases Society of America (IDSA) state that patients infected with MRSA strains that have a vancomycin MIC of Ն2 g/ml have a higher probability of treatment failure and recommend changing to alternate therapy (9). It is essential that clinical microbiology laboratories accurately determine vancomycin MICs to guide appropriate therapy.Trends toward increasing vancomycin MICs have been noted over the past 5 to 10 years (13). Hypotheses for the increase in vancomycin MICs include "MIC creep," clonal shift, and variation in vancomycin MICs demonstrated with various testing methods (3,10,14). It is critical for laboratorians to be aware of the normal distribution of vancomycin MICs observed by the testing system in use in their institution to properly assess the possibility of MIC creep or strains of MRSA with falsely elevated vancomycin MICs. A "falsely" elevated MIC could lead to an unnecessary change in treatment.The purpose of this study was to compare vancomycin and daptomycin MICs obtained by a variety of testing methods. A total of 161 consecutive blood culture isolates of MRSA were included in this study. The isolates were from Memorial Hermann Hospital, a 700-bed, private, tertiary care, universityaffiliated teaching hospital located within the Texas Medical Center in Houston, Texas, between August 2005 and May 2007. Diversilab sequencing according to the manufacturer's instructions yielded at least seven clones (data not shown), as found in other studies of MRSA isolates from our institution (15). Vancomycin MICs were determined by broth microdilution (BMD) trays prepared commercially and in-house, agarbased methods including Etest (bioMérieux, Durham, NC) and agar dilution, as well as automated BMD methods BD Phoenix, Vitek 2, and Microscan. Daptomycin MICs were determined by commercially prepared BMD trays, Etest, and Microscan. Etest inoculums were performed by hand plating. Agar and broth methods were performed according to CLSI standards using strain ATCC 29213 for quality control with each day of testing (2). All MIC determinations were performed in duplicate, and all commercial systems were used according to the manufacturer's instructions. Agar plates were prepared by serially diluting vancomycin hydrochloride hydrate (Sigma, St. Louis, MO) in Mueller-Hinton (BBL) agar at the following concentrations: 0.25, 0.5, 0.75,1, 1.5, and 2.0 g/ml. Custom-made frozen broth microdilution trays with an expanded dilution range of vancomycin and daptomycin were purchased...

The risk factors for relapse of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia after vancomycin treatment are unknown. Diversilab typing was used to classify recurrent bacteremia as relapse or reinfection. Bacteremia for >7 days and staphylococcal cassette chromosome mec element (SCCmec) type II were independently associated with relapse of MRSA bacteremia after vancomycin treatment.