Nationwide evaluation study of asphalt concrete overlays placed on fractured PCC pavements

Historically, agencies responsible for pavement rehabilitation have tried a wide variety of materials, processes, and construction methods to eliminate or minimize reflective cracking of asphaltic concrete overlays placed on existing portland cement concrete (PCC) pavements. Over the last 10 years, the fractured slab approach using rubblize, crack and seat, and break and seat has gained increased acceptance. Because the fractured slab approach has gradually evolved through field demonstration and actual projects, very little fundamental knowledge concerning design, construction, and performance models is available. Understandably, performance to date has been variable. To improve the state of the art and develop a better understanding of these techniques, a nationwide study was undertaken. A literature review resulted in the location of nearly 500 highway projects throughout the United States. From this generalized data base, approximately 100 sites were selected for detailed field studies. Field crews conducted visual distress surveys to assess pavement performance and nondestructive deflection testing to assess the in situ characteristics of the pavement layers. The general approach used for the research study and the analysis of field performance and structural data obtained is presented. Performance predictive equations are presented along with the evaluation of the backcalculated effective moduli of fractured PCC slabs for each technique. Analysis of within and between project variability is presented. The selection of optimal rehabilitation procedures and strategies for deteriorating highway pavements requires a knowledge of the type and cause of the distress, determination of candidate rehabilitation procedures, and selection of an optimal strategy based on economic and other considerations. For portland cement concrete (PCC) pavements, the array of possible rehabilitation procedures includes nonoverlay methods such as undersealing, grinding of the surface, and removal and replacement of distressed areas; fulf reconstruction by replacement or recycling; PCC overlays; and asphaltic concrete (AC) overlays. Review of current practice indicates that AC overlays are the most commonly used PCC rehabilitation procedure, with about $1 billion of AC overlays placed· each year, and this amount will likely increase in the future (J). Even though they are commonly used, the performance of AC overlays on PCC pavements is often hampered by the occurrence of reflection cracks over existing joints and cracks. Reflection cracks in the AC overlays are caused by a combination of thermal and traffic-induced stresses. Expansion and contraction of the PCC pavement results in horizontal movements that produce strains in the AC overlay exceeding its tensile strength. Traffic loads can cause vertical differential movements at the location of joints and working cracks in the PCC slab and induce critical shear stresses at the bottom of the AC layer. The overlay immediately over the joints and working cracks in the PCC is not able to accommodate these localized movements, resulting in the development of reflection cracks. A wide variety of rehabilitation techniques aimed at preventing the formation of, or minimizing, reflection cracking have been attempted. They include thick (conventional) overlays, crack relief layers, the saw and seal technique, special overlay and interface materials, and the fractured slab approach. Of these, the technique that has been used increasingly over the last 10 years has been the fractured slab approach. The major objective of the fractured slab approach is to reduce the effective in situ slab length before the overlay is placed. If this is effectively accomplished, the likelihood of having reflective cracks appear is significantly reduced or eliminated. The probability of reflective cracking is proportional to the horizontal movement at joints and cracks, which in tum is directly proportional to the spacing between joints and cracks. The fractured slab category is generally subdivided into three major types of rehabilitation: rubblize, crack and seat, and break and seat. Rubblize is a fractured slab process intended to transform the existing PCC layers into fragments having textural and gradational characteristics similar to those of a large aggregate size crushed stone base. It is most effectively accomplished with a resonant pavement breaker, which has been successfully used on all types of existing PCC pavements [i.e., jointed plain (JPC), jointed reinforced (JRC), and continuously reinforced (CRC) concrete pavements]. Crack/seat and break/seat are fracture techniques intended to produce very short rigid slabs whose effective lengths vary from 12 to 48 in. The techniques are similar, with guillotines or spring-arm (whip) hammers being used to develop reduced crack spacings in the existing PCC pavement. There is, however, a significant distinction between the two techniques. Crack/seat is associated with the fractured slab process conducted solely on JPC pavements. For these pavements, th

Reconstruction of the extensor mechanism with fresh-frozen tendon allograft in total knee arthroplasty

Purpose: Patellar tendon rupture after total knee replacement is a rare and highly limiting injury with multifactorial aetiology. Many reconstruction techniques have been described with not very predictable results. The use of allografts has been accepted as a suitable solution. Methods: A series of seven patients with patellar tendon rupture treated with fresh-frozen tendon allograft reconstruction after knee arthroplasty is presented. Results: Median follow-up is 25 months (20-31). Functional assessment improved, and the knee society score and knee functional score improved from 26 and 16 to 82 and 55, respectively. Median extension lag was 5° (0°-20°), with a median range of motion of 95° (70-100). Radiological study showed a rise of the patella of 22.26 mm. Conclusion: The use of fresh-frozen allografts as a solution to patellar tendon ruptures after knee arthroplasty seems to provide acceptable results. Increased patellar height does not seem to affect functionality

Initial invasive or conservative strategy for stable coronary disease

BACKGROUND Among patients with stable coronary disease and moderate or severe ischemia, whether clinical outcomes are better in those who receive an invasive intervention plus medical therapy than in those who receive medical therapy alone is uncertain. METHODS We randomly assigned 5179 patients with moderate or severe ischemia to an initial invasive strategy (angiography and revascularization when feasible) and medical therapy or to an initial conservative strategy of medical therapy alone and angiography if medical therapy failed. The primary outcome was a composite of death from cardiovascular causes, myocardial infarction, or hospitalization for unstable angina, heart failure, or resuscitated cardiac arrest. A key secondary outcome was death from cardiovascular causes or myocardial infarction. RESULTS Over a median of 3.2 years, 318 primary outcome events occurred in the invasive-strategy group and 352 occurred in the conservative-strategy group. At 6 months, the cumulative event rate was 5.3% in the invasive-strategy group and 3.4% in the conservative-strategy group (difference, 1.9 percentage points; 95% confidence interval [CI], 0.8 to 3.0); at 5 years, the cumulative event rate was 16.4% and 18.2%, respectively (difference, 121.8 percentage points; 95% CI, 124.7 to 1.0). Results were similar with respect to the key secondary outcome. The incidence of the primary outcome was sensitive to the definition of myocardial infarction; a secondary analysis yielded more procedural myocardial infarctions of uncertain clinical importance. There were 145 deaths in the invasive-strategy group and 144 deaths in the conservative-strategy group (hazard ratio, 1.05; 95% CI, 0.83 to 1.32). CONCLUSIONS Among patients with stable coronary disease and moderate or severe ischemia, we did not find evidence that an initial invasive strategy, as compared with an initial conservative strategy, reduced the risk of ischemic cardiovascular events or death from any cause over a median of 3.2 years. The trial findings were sensitive to the definition of myocardial infarction that was used

Health-status outcomes with invasive or conservative care in coronary disease

BACKGROUND In the ISCHEMIA trial, an invasive strategy with angiographic assessment and revascularization did not reduce clinical events among patients with stable ischemic heart disease and moderate or severe ischemia. A secondary objective of the trial was to assess angina-related health status among these patients. METHODS We assessed angina-related symptoms, function, and quality of life with the Seattle Angina Questionnaire (SAQ) at randomization, at months 1.5, 3, and 6, and every 6 months thereafter in participants who had been randomly assigned to an invasive treatment strategy (2295 participants) or a conservative strategy (2322). Mixed-effects cumulative probability models within a Bayesian framework were used to estimate differences between the treatment groups. The primary outcome of this health-status analysis was the SAQ summary score (scores range from 0 to 100, with higher scores indicating better health status). All analyses were performed in the overall population and according to baseline angina frequency. RESULTS At baseline, 35% of patients reported having no angina in the previous month. SAQ summary scores increased in both treatment groups, with increases at 3, 12, and 36 months that were 4.1 points (95% credible interval, 3.2 to 5.0), 4.2 points (95% credible interval, 3.3 to 5.1), and 2.9 points (95% credible interval, 2.2 to 3.7) higher with the invasive strategy than with the conservative strategy. Differences were larger among participants who had more frequent angina at baseline (8.5 vs. 0.1 points at 3 months and 5.3 vs. 1.2 points at 36 months among participants with daily or weekly angina as compared with no angina). CONCLUSIONS In the overall trial population with moderate or severe ischemia, which included 35% of participants without angina at baseline, patients randomly assigned to the invasive strategy had greater improvement in angina-related health status than those assigned to the conservative strategy. The modest mean differences favoring the invasive strategy in the overall group reflected minimal differences among asymptomatic patients and larger differences among patients who had had angina at baseline