Second-Generation Orthopaedic Measurement Device for in-vivo Assessment of Bone Quality

There are two main types of bone in the human body, trabecular and cortical bone. Cortical bone is primarily found on the outer surface of most bones in the body while trabecular bone is found in vertebrae and at the end of long bones (Ross 2007). Osteoporosis is a condition that compromises the structural integrity of trabecular bone, greatly reducing the ability of the bone to absorb energy from falls. The current method for diagnosing osteoporosis and predicting fracture risk is measurement of bone mineral density. Limitations of this method include dependence on the bone density measurement device and dependence on type of test and measurement location (Rubin 2005). Each year there are approximately 250,000 hip fractures in the United States due to osteoporosis (Kleerekoper 2006). Currently, the most common method for repairing a hip fracture is a hip fixation surgery. During surgery, a temporary guide wire is inserted to guide the permanent screw into place and then removed. It is believed that directly measuring this screw pullout force may result in a better assessment of bone quality than current indirect measurement techniques (T. Bowen 2008-2010, pers. comm.). The objective of this project is to design a device that can measure the force required to extract this guide wire. It is believed that this would give the surgeon a direct, quantitative measurement of bone quality at the site of the fixation. A first generation device was designed by a Bucknell Biomedical Engineering Senior Design team during the 2008- 2009 Academic Year. The first step of this project was to examine the device, conduct a thorough design analysis, and brainstorm new concepts. The concept selected uses a translational screw to extract the guide wire. The device was fabricated and underwent validation testing to ensure that the device was functional and met the required engineering specifications. Two tests were conducted, one to test the functionality of the device by testing if the device gave repeatable results, and the other to test the sensitivity of the device to misalignment. Guide wires were extracted from 3 materials, low density polyethylene, ultra high molecular weight polyethylene, and polypropylene and the force of extraction was measured. During testing, it was discovered that the spring in the device did not have a high enough spring constant to reach the high forces necessary for extracting the wires without excessive deflection of the spring. The test procedure was modified slightly so the wires were not fully threaded into the material. The testing results indicate that there is significant variation in the screw pullout force, up to 30% of the average value. This significant variation was attributed to problems in the testing and data collection, and a revised set of tests was proposed to better evaluate the performance of the device. The fabricated device is a fully-functioning prototype and further refinements and testing of the device may lead to a 3rd generation version capable of measuring the screw pullout force during hip fixation surgery.

AN EXAMINATION OF THE STARS-PAC ANXIETY INTERVENTION PROGRAM AND ITS EFFECTS ON DECREASING SOCIAL AND TEST ANXIETY

The current case study examined the effects of the STARS-PAC anxiety reduction program on the social and test anxiety levels of a middle school student. The literature supporting the effectiveness of cognitive behavioral therapy programs which incorporate methods such as those used in the STARS-PAC program were reviewed. The findings of this case study indicated decreased levels of overall anxiety during the intervention phase; however, the student’s test anxiety level displayed little improvement. Implications of the findings and for future research are discussed.

Secondary Collisions Revisited: Real-World Crash Characteristics and Relationship to Crash Test Criteria

Previous research conducted in the late 1980’s suggested that vehicle impacts following an initial barrier collision increase severe occupant injury risk. Now over twenty-five years old, the data used in the previous research is no longer representative of the currently installed barriers or US vehicle fleet. The purpose of this study is to provide a present-day assessment of secondary collisions and to determine if full-scale barrier crash testing criteria provide an indication of secondary collision risk for real-world barrier crashes. The analysis included 1,383 (596,331 weighted) real-world barrier midsection impacts selected from thirteen years (1997-2009) of in-depth crash data available through the National Automotive Sampling System (NASS) / Crashworthiness Data System (CDS). For each suitable case, the scene diagram and available scene photographs were used to determine roadside and barrier specific variables not available in NASS/CDS. Binary logistic regression models were developed for second event occurrence and resulting driver injury. Barrier lateral stiffness, post-impact vehicle trajectory, vehicle type, and pre-impact tracking conditions were found to be statistically significant contributors toward secondary event occurrence. The presence of a second event was found to increase the likelihood of a serious driver injury by a factor of seven compared to cases with no second event present. Twenty-four full-scale crash test reports were obtained for common non-proprietary US barriers, and the risk of secondary collisions was determined using recommended evaluation criteria from NCHRP Report 350. It was found that the NCHRP Report 350 exit angle criterion alone was not sufficient to predict second collision occurrence for real-world barrier crashes.