Best Predictors Of Failure Research Articles

Patellar strain and patellofemoral contact after bone-patellar tendon-bone harvest for anterior cruciate ligament reconstruction

Objective: To characterize the morbific consequences of harvesting a patellar tendon graft for use in reconstructing the anterior cruciate ligament (ACL) of the knee, specifically, (1) to measure changes in patellar strain and patellofemoral contact due to graft harvest, (2) to evaluate the ability of bone-grafting the patellar defect to mitigate these effects, and (3) to characterize failure of the extensor mechanism after harvest of a patellar tendon graft. Design: Twenty-two cadaver knee joints were tested before and after harvest of a patellar tendon graft and after filling the patellar defect with polymethylmethacrylate to simulate a healed bone graft. Knees were positioned in 30°, 60°, and 90° flexion and loaded while measuring axial strain in the anterior patella and patellofemoral contact. Knees were then loaded to failure. Results: Harvest of the graft produced increases in axial strain at all flexion angles. Filling the defect restored axial strain to normal values. Patellofemoral contact in the presence of a defect, either filled or empty, was not different from contact for intact patellae. Most knees failed by transpatellar fracture; mean extension moment at failure was 112.8Nm. The best predictors of failure were age and gender. Conclusion: Patients undergoing ACL reconstruction with a patellar tendon graft are at increased risk of anterior knee pain and disruption of the extensor mechanism. Bone-grafting the patellar defect created by graft harvest can reduce these risks. Our findings underscore the importance of carefully controlled rehabilitation and suggest that if an accelerated program of rehabilitation is anticipated, the patellar defect should be bone-grafted. Older patients, particularly women, are at increased risk of catastrophic failure of the knee extensor mechanism after ACL reconstruction using patellar tendon graft.

A Prospective Study of Indexes Predicting the Outcome of Trials of Weaning from Mechanical Ventilation

The traditional predictors of the outcome of weaning from mechanical ventilation--minute ventilation (VE) and maximal inspiratory pressure (Plmax)--are frequently inaccurate. We developed two new indexes: the first quantitates rapid shallow breathing as the ratio of respiratory frequency to tidal volume (f/VT), and the second is termed CROP, because it integrates thoracic compliance, respiratory rate, arterial oxygenation, and Plmax. The threshold values for each index that discriminated best between a successful and an unsuccessful outcome of weaning were determined in 36 patients, and the predictive accuracy of these values was then tested prospectively in an additional 64 patients. Sensitivity and specificity were calculated, and the data were also analyzed with receiver-operating-characteristic (ROC) curves, in which the proportions of true positive results and false positive results are plotted against each other for a number of threshold values of an index; the area under the curve reflects the accuracy of the index. Sensitivity was highest for Plmax (1.00), followed closely by the f/VT ratio (0.97). Specificity was highest for the f/VT ratio (0.64) and lowest for Plmax (0.11). The f/VT ratio was the best predictor of successful weaning, and Plmax and the f/VT ratio were the best predictors of failure. The area under the ROC curve for the f/VT ratio (0.89) was larger than that under the curves for the CROP index (0.78, P less than 0.05), Plmax (0.61, P less than 0.001), and VE (0.40, P less than 0.001). Rapid shallow breathing, as reflected by the f/VT ratio, was the most accurate predictor of failure, and its absence the most accurate predictor of success, in weaning patients from mechanical ventilation.

Shock Probation in Ohio

In this study of Ohio's shock probation program, base expectancy rates were developed through the use of predictive attribute analysis. These rates were used to evaluate the stated guidelines of the program; namely, that shock probation should be targeted for use with youthful first offenders. Therefore, the base expectancy rates were utilized to test a prediction which was being made by relevant decision-makers within the program (judges, probation officers). Analysis of the research sample of 1,081 shock probationers released in 1975 revealed that prior record was the best predictor of failure (reincarceration over a two year period). The shock probationers who had a previous criminal record were more than twice as likely to fail. These rates were not cross-validated and were not recommended for application in a mechanical fashion by decision-makers.