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Unlabelled: Polymerase chain reaction (PCR) assays have been used to detect bacteria adherent to failed orthopaedic implants, but some PCR assays have had problems with probable false-positive results. We used a combination of a Staphylococcus species-specific PCR and a universal PCR followed by DNA sequencing to identify bacteria on implants retrieved from 52 patients (92 implants) at revision arthroplasty. We addressed two questions in this study: (1) Is this method able to show the existence of bacterial DNA on presumed aseptic loosed implants?; and (2) What proportion of presumed aseptic or culture-negative implants was positive for bacterial DNA by PCR? Fourteen implants (15%) were believed infected, whereas 74 implants (85%) were believed aseptic. Each implant was sonicated and the resulting solution was submitted for dual real-time PCR assay and culture. All implants believed aseptically loose were culture-negative, but nine of the 74 (12%) had bacterial DNA by PCR; two (2.7%) were PCR-positive and also showed histologic findings suggestive of infection. Uniquely developed PCR and bacterial sequencing assays showed bacterial DNA on 12% of implants removed for presumed aseptic loosening. Additional studies are needed to determine the clinical importance of bacterial DNA detected by PCR but not by conventional culture.Level Of Evidence: Level III, diagnostic study. [ABSTRACT FROM AUTHOR]

OBJECTIVE: To determine whether longer duration of anesthesia predisposes patients undergoing orthopedic surgery to venous thromboembolism (VTE). PATIENTS AND METHODS: We conducted a secondary analysis of a retrospective case-control study that examined risk factors for postoperative VTE in postmenopausal women. We matched women aged 50 years and older with radiographically confirmed postoperative VTE (cases) by age, surgeon, year of surgery, and surgical joint (knee vs hip) with women without postoperative VTE (controls). Duration of anesthesia, operative variables, demographic data, comorbid illnesses, and laboratory data were determined by medical record review. RESULTS: Eighty-eight cases were matched with 181 controls. Duration of anesthesia of 3.5 hours or longer (corresponding to the upper tertile of patients) was strongly associated with postoperative VTE compared with a shorter duration of anesthesia (odds ratio, 3.58; 95% confidence Interval, 2.11-6.16; P < .001). This relationship was maintained after controlling for multiple covariates with propensity score methods, Including type of arthroplasty, route of anesthesia, type of antithrombotic prophylaxis, and surgical approach. In multivariate analysis, the Important predictors of VTE included anesthesia duration of 3.5 hours or longer, type of antithrombotic prophylaxis, revision (vs primary) arthroplasty, and allogeneic blood transfusion. CONCLUSION: We found a marked association between the duration of anesthesia and postoperative VTE in patients undergoing Joint arthroplasty. Although it is possible that unmeasured intraoperative variables account for this relationship, we suggest that duration of anesthesia may be an important risk factor for postoperative VTE after orthopedic surgery. [ABSTRACT FROM AUTHOR]

An abstract of the article "Idiopathic calcifications in the pulmonary artery and aorta detected by fetal ultrasound scan and echocardiography: a case report," by J. Q. Andrade, L. M. Lopes, V. L. Krebs, M. Okumura, R. P. Francisco, and M. Zugaib is presented.

Background: Whether decreasing the local anesthetic concentration during a continuous femoral nerve block results in less quadriceps weakness remains unknown.Methods: Preoperatively, bilateral femoral perineural catheters were inserted in subjects undergoing bilateral knee arthroplasty (n = 36) at a single clinical center. Postoperatively, right-sided catheters were randomly assigned to receive perineural ropivacaine of either 0.1% (basal 12 ml/h; bolus 4 ml) or 0.4% (basal 3 ml/h; bolus 1 ml), with the left catheter receiving the alternative concentration/rate in an observer- and subject-masked fashion. The primary endpoint was the maximum voluntary isometric contraction of the quadriceps femoris muscles the morning of postoperative day 2. Equivalence of treatments would be concluded if the 95% CI for the difference fell within the interval -20%-20%. Secondary endpoints included active knee extension, passive knee flexion, tolerance to cutaneous electrical current applied over the distal quadriceps tendon, dynamic pain scores, opioid requirements, and ropivacaine consumption.Results: Quadriceps maximum voluntary isometric contraction for limbs receiving 0.1% ropivacaine was a mean (SD) of 13 (8) N · m, versus 12 (8) N · m for limbs receiving 0.4% [intrasubject difference of 3 (40) percentage points; 95% CI -10-17; P = 0.63]. Because the 95% CI fell within prespecified tolerances, we conclude that the effect of the two concentrations were equivalent. Similarly, there were no statistically significant differences in secondary endpoints.Conclusions: For continuous femoral nerve blocks, we found no evidence that local anesthetic concentration and volume influence block characteristics, suggesting that local anesthetic dose (mass) is the primary determinant of perineural infusion effects. [ABSTRACT FROM AUTHOR]

A letter to the editor related to the diagnosis of congenital pulmonary cystic lesions is presented.

Periprosthetic infections are rare, but there is evidence to suggest that their frequency may be underestimated. No single laboratory test has perfect sensitivity and specificity for diagnosing infection. Most tests have better specificity when they are performed for patients in whom infection is suspected clinically rather than when they are used as screening tests. Screening test results that may suggest the possibility of infection include elevation of the erythrocyte sedimentation rate and/or serum C-reactive protein level more than three months after an arthroplasty. Most serologic tests are difficult to interpret when the patient has an underlying inflammatory arthropathy. Cultures of aspirated joint fluid can be especially helpful for patients who have symptoms suggestive of infection, but their results are best interpreted two weeks after administration of antibiotics has been discontinued. Joint fluid cell counts may also be helpful, but Gram stains of joint fluid have poor sensitivity and specificity. Criteria for diagnosing infection on the basis of frozen sections of implant membranes have not yet been standardized, but in many laboratories more than five neutrophils per high-power field in five or more fields (excluding surface fibrin) has been found to be suggestive of infection. Most polymerase chain reactions that detect the universal 16S rRNA bacterial gene have problems with false-positive results, but combining a universal polymerase chain reaction with subsequent bacterial sequencing can help improve specificity. Polymerase chain reactions can detect necrotic bacteria, so the clinical importance of positive results of this analysis in the absence of other features of infection remains to be determined. [ABSTRACT FROM AUTHOR]

Abstract: Model predictive control (MPC) is a popular controller design technique in the process industry. Conventional MPC uses linear or nonlinear discrete-time models. Recently, MPC has been extended to a class of discrete-event systems that can be described by a model that is 'linear' in max-plus algebra. An adaptive scheme for the time-varying case, based on parameter estimation of input-output models is presented. In a simulation example it is shown that the combined parameterestimation/MPC algorithm gives a good closed-loop behaviour. [ABSTRACT FROM AUTHOR]