Experimental and Computational Approach Investigating Burst Fracture Augmentation Using PMMA and Calcium Phosphate Cements

The aim of the study was to use a computational and experimental approach to evaluate, compare and predict the ability of calcium phosphate (CaP) and poly (methyl methacrylate) (PMMA) augmentation cements to restore mechanical stability to traumatically fractured vertebrae, following a vertebroplasty procedure. Traumatic fractures (n = 17) were generated in a series of porcine vertebrae using a drop-weight method. The fractured vertebrae were imaged using μCT and tested under axial compression. Twelve of the fractured vertebrae were randomly selected to undergo a vertebroplasty procedure using either a PMMA (n = 6) or a CaP cement variation (n = 6). The specimens were imaged using μCT and re-tested. Finite element models of the fractured and augmented vertebrae were generated from the μCT data and used to compare the effect of fracture void fill with augmented specimen stiffness. Significant increases (p <0.05) in failure load were found for both of the augmented specimen groups compared to the fractured group. The experimental and computational results indicated that neither the CaP cement nor PMMA cement could completely restore the vertebral mechanical behavior to the intact level. The effectiveness of the procedure appeared to be more influenced by the volume of fracture filled rather than by the mechanical properties of the cement itself.

Critical evaluation of pulse-echo ultrasonic test method for the determination of setting and mechanical properties of acrylic bone cement: Influence of mixing technique

Currently there is no reliable objective method to quantify the setting properties of acrylic bone cements within an operating theatre environment. Ultrasonic technology can be used to determine the acoustic properties of the polymerising bone cement, which are linked to material properties and provide indications of the physical and chemical changes occurring within the cement. The focus of this study was the critical evaluation of pulse-echo ultrasonic test method in determining the setting and mechanical properties of three different acrylic bone cement when prepared under atmospheric and vacuum mixing conditions. Results indicated that the ultrasonic pulse-echo technique provided a highly reproducible and accurate method of monitoring the polymerisation reaction and indicating the principal setting parameters when compared to ISO 5833 standard, irrespective of the acrylic bone cement or mixing method used. However, applying the same test method to predict the final mechanical properties of acrylic bone cement did not prove a wholly accurate approach. Inhomogeneities within the cement microstructure and specimen geometry were found to have a significant influence on mechanical property predictions. Consideration of all the results suggests that the non-invasive and non-destructive pulse-echo ultrasonic test method is an effective and reliable method for following the full polymerisation reaction of acrylic bone cement in real-time and then determining the setting properties within a surgical theatre environment. However the application of similar technology for predicting the final mechanical properties of acrylic bone cement on a consistent basis may prove difficult.

Bericht englischer Sachverständiger über Palästina

John Orr

The middle Kingdom : a survey of the ... Chinese Empire and its inhabitants : with a new map of the Empire, and illustrations /

Mode of access: Internet.

Pictorial guide to the Falls of Niagara: a manual for visitors, giving an account of this stupendous natural wonder; and all the objects of curiosity in its vicinity; with every historical incident of interest: and also full directions for visiting the cataract and its neighbouring scenes ...

Mode of access: Internet.

Dave Strack, UM Men's Basketball coach, Cazzie Russell, Bill Buntin

[with Big Ten championship ball and all-American certificates)

University of Michigan Men's Basketball Team, 1979

Back Row: trainer Dan Campbell, equip. mngr. Bob Hurst, asst. coach Mike Boyce, Martin Bodnar, Mark Lozier, coach John Orr, John Johnson, Mark Bodnar, Keith Smith, asst. coach Bill Frieder, ?

Front Row: mngr. Edwin VanDeWege, Mike McGee, Paul Heuerman, John Garris, co-captain Phil Hubbard, , Alan Hardy, Thad Garner, co-captain Tom Staton

Off-hand sketches; a companion for the tourist and traveller over the Philadelphia, Pottsville, and Reading railroad.

Engravings signed by Scattergood, Pilliner, Devereux, Brightly, Louderback, R. Telfer, Scattergood & Telfer, Hoffmann, Lawrie, J.W. Orr, Kramer, and Baker.

Agriculture in Berkshire; a survey made on behalf of the Institute for research in agricultural economics, University of Oxford /

Mode of access: Internet.

Commonplace book of Hector Orr, 1789-1804

Hector Orr began recording entries in this commonplace book during his first year as a student at Harvard and continued writing in the volume sporadically until 1804. The entries written while he was a student, from 1789 to 1792, include themes written on the following topics: Time, Discontent, Patriotism, Virtue, Conscience, Patience, Avarice, Compassion, Mortality, Self-knowledge, Benevolence, Morning, Anger, Profanity, Bribery, Autumn and Winter, Hermitage, Conscience and Anticipation. He also wrote detailed entries about the forensic disputations in which he and his classmates participated, explaining both the affirmative and negative positions. One of these disputations involved discussion of the Stamp Act, which was then quite recent history. Orr's entries about the disputations list the names of students involved and specify their position in the argument.