Assessment of heat generation and risk of thermal necrosis during bone burring by means of three-dimensional dynamic elastoplastic finite element modelling.

During bone burring, the heat generated due to friction at the bone-burr interface may cause thermal damage to the bone. Therefore, it is necessary to assess bone temperature distribution around a burring site and identify high-risk regions for thermal necrosis due to bone burring. In this study, a three-dimensional (3-D) dynamic elastoplastic finite element model for the burring process was developed and experimentally validated to investigate the influence of burring parameters (rotational speeds: 3,000, 10,000, 15,000 and 60,000 rpm; feed rates: 0.5, 0.9, 1.5 and 3.0 mm/s) on heat generation and evaluate the risk region for thermal necrosis. Calculated bone temperatures were compared with experimental values and found to be in good agreement with them. The analytical results demonstrated a linear relationship between the burring time and friction energy. In addition, the friction energy increased with the bone temperature. The high-risk thermal necrosis zone was measured from the edge of burring (y-direction) at feed rates of 0.5, 0.9, 1.5 and 3.0 mm/s and was found to be 7.8, 7.3, 6.6 and 5.5 mm, respectively. When the burr rotational speed increased from 3,000 to 60,000 rpm, the high-risk zone for thermal necrosis increased from 4.5 to 8.1 mm. We concluded that both the friction energy and the bone temperature increased in proportion with the burr rotational speed. Reducing burr rotational speeds and/or increasing feed rates may decrease the rise in bone temperature, thus decreasing the potential for thermal necrosis near the burring site. Our model can be used to select the optimal surgery parameters to minimise the risk of thermal necrosis due to bone burring and to assist in the design of optimal orthopaedic drill handpieces.

Web-based computer adaptive assessment of individual perceptions of job satisfaction for hospital workplace employees.

BACKGROUND: To develop a web-based computer adaptive testing (CAT) application for efficiently collecting data regarding workers' perceptions of job satisfaction, we examined whether a 37-item Job Content Questionnaire (JCQ-37) could evaluate the job satisfaction of individual employees as a single construct. METHODS: The JCQ-37 makes data collection via CAT on the internet easy, viable and fast. A Rasch rating scale model was applied to analyze data from 300 randomly selected hospital employees who participated in job-satisfaction surveys in 2008 and 2009 via non-adaptive and computer-adaptive testing, respectively. RESULTS: Of the 37 items on the questionnaire, 24 items fit the model fairly well. Person-separation reliability for the 2008 surveys was 0.88. Measures from both years and item-8 job satisfaction for groups were successfully evaluated through item-by-item analyses by using t-test. Workers aged 26 - 35 felt that job satisfaction was significantly worse in 2009 than in 2008. CONCLUSIONS: A Web-CAT developed in the present paper was shown to be more efficient than traditional computer-based or pen-and-paper assessments at collecting data regarding workers' perceptions of job content.

Diagnostic accuracy, biohazard safety, and cost effectiveness-the Lodox/Statscan provides a beneficial alternative for the primary evaluation of patients with multiple injuries.

BACKGROUND: Lodox/Statscan is a new digital X-ray machine with a low dose of radiation exposure that provides rapid, whole-body scans. In the setting of acute trauma management, the importance of image study is well recognized. Here, we report the accuracy of diagnoses made using Lodox/Statscan in patients with multiple injuries. We analyze the cost effectiveness, biohazard safety, and detection rate for treatment using the Lodox/Statscan and evaluate whether it is a viable alternative to the conventional trauma X-ray. METHODS: We retrospectively reviewed patients who received a Lodox/Statscan between November 2007 and January 2009. All patients who had received both a Lodox/Statscan and a computed tomographic (CT) scan were enrolled. The CT scan was used to make the final diagnosis. The detection rate for treatment, sensitivity, and specificity of the Lodox/Statscan in diagnosis was analyzed. RESULTS: One hundred eighty-four patients were eligible for the study during the 15-month study period. The detection rates for treatment using the Lodox/Statscan for pneumothorax, pelvic fracture, cervical spine injury, and thoracic-lumbar spine injury were 95%, 96.0%, and 57.1%, and 100%, respectively. CONCLUSION: In our series, the Lodox/Statscan provided similar quality images and conventional series to the CT scans. Although the Lodox/Statscan missed some injuries, most of the subsequent treatments were not changed. Overall, there were several advantages to using this system, including the short interval of study, low-radiation exposure, and low cost. The Lodox/Statscan could therefore be used as an alternative to the traditional trauma X-ray for evaluation of acute trauma patients.