At 20 years, the cumulative probability of a post-operative femoralfracture was 3.5% (95% CI 3.2 to 3.9%). Among the 222 post-operativeperiprosthetic fractures after a cemented femoral primary THA, thecumulative probabilities of a fracture were 0.03% (n = 4) duringthe first 30 days, 0.2% (n = 21) during the first year, 0.4% (n= 32) between years one and five, and 3.1% (n = 152) between yearsfive and 20 (Table IX). Among the 335 post-operative periprostheticfractures after an uncemented femoral primary THA, the cumulative probabilitiesof a fracture were 0.2% (n = 32) during the first 30 days, 0.6%(n = 73) during the first year, 1.2% (n = 69) between years oneto five, and 12.5% (n = 159) between years five and 20 (Table IX).Hips treated with uncemented femoral components experienced a higherrate of early fractures and also experienced a higher rate of late fracturesafter THA. In addition, Vancouver AG and B1 fractureswere generally identified earliest, whereas Vancouver AL andB3 fractures tended to happen quite late (Table VIII).
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Intra-operative periprosthetic femoral fractures occurred 14times more often with uncemented stems (3%) compared with cementedstems (0.2%). When analysing previous reports on intra-operativeperiprosthetic femoral fractures associated with cemented primarystems, the frequency ranges from 0.1% to 2.5%.2,12,13 Tayloret al14 reporteda 1.2% rate of intra-operative fracture in 605 cemented THAs. Lookingat the Mayo Clinic Total Joint Registry through 1999, Berry2 noted intra-operativefractures in 0.3% of 20 859 cemented primary THAs. In the same series,which comprised the early experience with uncemented implants, therisk of intra-operative periprosthetic femoral fracture increasedto 5.4% of 3121 primary THAs when the stems were uncemented.2 Schwartz, Mayer andEngh15 similarlyreported a 3.7% intra-operative fracture rate (39 of 1318) in primaryuncemented stems. As such, the incidence of intra-operative periprostheticfemoral fractures associated with uncemented primary stems rangesfrom 3.7% to 5.4% in the older literature.
Risk factors for periprosthetic fractures vary by anatomicalsite, but include host, operative technique, and implant relatedfactors. Intra-operative fractures are most common in female patientsgreater than 65 years of age receiving uncemented stems, whereaspost-operative fractures are most common with uncemented stems,regardless of age or gender. By 20 years, nearly 4% of patientswill have experienced a post-operative periprosthetic fracture ofthe femur.
When utilizing microsurfacing as a treatment to existing flexible pavement, the first step is to ensure the pavement is structurally sound and able to be prepared properly to accept the treatment. Proper preparation of the pavement surface includes cleaning and sealing tight cracks, filling wide cracks, and thoroughly brooming and cleaning the pavement to remove loose dirt and contaminants. A tack coat is not normally applied but can be required in specific applications. The application requires a continuous-flow mixing unit, a multiblade, double-shafted mixer, and a spreader box.
An undisputed limitation of microsurfacing is that it does not level humps in the road. Microsurfacing will fill depressions and ruts but cannot address humps and will, in fact, reproduce a hump in the treatment surface. Any humps should be leveled before applying microsurfacing, and any pothole or crack patches should not be left high [24].
One of the early studies done on microsurfacing in the United States foreshadowed the favorable conclusions of further research by recommending that microsurfacing be approved for routine use in restoring flexible pavements to fill surface ruts and cracks, seal the surface, and restore skid resistance [6]. The Georgia DOT had great success with microsurfacing in correcting smoothness and friction deficiencies, and stopping raveling and load cracking without an increase in pavement noise levels. A good aesthetic value was also achieved with these applications [23].
Critical components to ensure the success of a microsurfacing project include a comprehensive mix design process, quality materials, and the use of a knowledgeable and experienced contractor [21]. Olsen (n.d.) also reported that workmanship is a key factor in the effectiveness of microsurfacing treatments. Other studies have shown that microsurfacing performance is strongly affected by workmanship, and the condition of the pavement at the time of application is the most important factor contributing to success ([15, 35, 47, 48], n.d.). Pederson et al. [6] categorically stated that the quality of a finished microsurfacing project depends greatly on the skill of the operator and crew.
Microsurfacing should not be placed on highly deflecting surfaces, cracked surfaces, pavements with base failures, or on dirty or poorly prepared surfaces (resulting in delamination) [32]. As is true of most PM treatments, microsurfacing is much more effective when used on noninterstate and flexible pavements as opposed to interstate and rigid pavements [13].
Allan [7] stated that one of the greatest challenges for our industry is to be able to meet the ever-changing environmental regulations. Cold-applied-non-polluting maintenance products for road systems will definitely be used. The ISSA reports that microsurfacing emits 1/4 the potential of HMA and 1/3 the potential of modified HMA with regards to kilograms of ethene, carbon dioxide, and kilograms of nitrogen dioxide when measured per lane mile ([41], n.d.). Sinha and Labi [54] similarly stated the impact of environmentally friendly PM treatments by pointing out the monetary costs of air pollution and the global agreements on air quality standards and air-quality legislation. Takamura et al. [19] concluded that a small improvement in durability of the microsurfacing would result in significant cost and ecological advantages, and that future improvements in microsurfacing technologies could lead to additional cost and environmental advantages. Along the same lines with regards to microsurfacing, Allan [7] predicts that the possibilities for the inclusion of performance-enhancing additives above and beyond those already available will greatly impact the equipment used in the future. One such study by Holleran and Reed [55] looked at improving the crack resistance of microsurfacing by increasing polymer content, as well as adding fibers to the binders. They found that while fibers do not help, certain polymers do increase flexibility and cracking resistance of microsurfacing, especially in association with asphalt rubber crumb. More studies need to be done on ways to make microsurfacing less susceptible to reflective cracking, effectively addressing one of the two factors that contribute most to failure of this treatment. 2ff7e9595c
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