Computer navigation of parapedicular screw fixation in the thoracic spine: a cadaver study.

STUDY DESIGN: An in vitro study to investigate the advantages of computer assistance for the purpose of parapedicular screw fixation in the upper and middle thoracic spine. OBJECTIVES: To evaluate the feasibility and application accuracy of parapedicuar screw insertion with the assistance of an optoelectronic navigation system. SUMMARY OF BACKGROUND DATA: Because of anatomic limitations, thoracic pedicle screw insertion in the upper and middle thoracic spine remains a matter of controversy. The technique of parapedicular screw insertion has been described as an alternative, although the exact screw position is difficult to control. With the assistance of computer navigation for the screw placement, it might become possible to overcome these challenges. METHODS: Four human specimens were harvested for this study; 6-mm screws were inserted from T2 to T8 with the assistance of a CT-based optoelectronic navigation system. During surgery virtual images of the screw position were documented and compared with postoperative contact radiographs to determine the application accuracy. The following measurements were obtained: axial and sagittal screw angles as well as the screw distances to the anterior vertebral cortex and the medial pedicle wall. RESULTS: All 54 screws were inserted in a parapedicular technique without violation of the medial pedicle wall or the anterior or lateral vertebral cortex. The mean +/- standard deviation difference between the virtual images and the radiographs was 1.0 +/- 0.94 mm for the distance to the medial pedicle wall and 1.9 +/- 1.44 mm for the distance to the anterior cortex. The angular measurements showed a difference of 1.6 +/- 1.1 degrees for the transverse screw angle and 2.1 +/- 1.6 degrees for the sagittal screw orientation. CONCLUSION: With the assistance of computer navigation it is possible to achieve a safe and reliable parapedicular screw insertion in the upper and middle thoracic spine in vitro. The application accuracy varies for the linear and angular measurements and is higher in the axial than in the sagittal plane. It is important for the surgeon to understand these limitations when using computer navigation in spinal surgery.

Relations of work stress to alcohol use and drinking problems in male and female employees of a computer factory in Japan.

To examine the effects of work stressors on alcohol use and drinking problems as well as a model of stress-induced drinking in Japanese male and female workers, a total of 2581 employees of a computer factory were surveyed using mailed questionnaires. Five psychosocial work stressors, overtime, rotating shift, frequency of drinking, amount of alcohol consumed per drinking occasion, and drinking problems, and depressive symptoms were assessed. The hierarchical linear and logistic regression analyses were conducted in 1043 male and 255 female current drinkers aged 20 years or older. The results suggested that overtime and lack of intrinsic work rewards are main factors for heavy and problem drinking in Japanese male workers and that ambiguity about job future is a factor for heavy drinking in Japanese female workers. However, the model of stress-induced drinking was supported neither in males nor in females, suggesting that the effects of these work stressors on heavy and problem drinking are not mediated by depressive symptoms.

Prevalence and demographic correlates of alcohol-related problems in Japanese employees.

To examine the relationship of basic sociodemographic characteristics to alcohol-related problem in Japanese employees, a questionnaire survey was conducted of a total of 2,581 employees of a computer factory in a suburb of Tokyo. The questionnaires included items on gender, age, marital status, social class (i.e., education, family income and occupation), alcohol consumption, and the Kurihama Alcoholism Screening Test (KAST). Data from 1098 male and 265 female current drinkers aged 20 years or older were analyzed; 15% and 6% of the male and female subjects, respectively, were classified as having alcohol-related problems on the basis of the KAST score (13% and 4% of the entire study population, respectively). Multiple logistic regression analysis indicated that alcohol-related problems were more prevalent in the less educated, managers and those who had a high alcohol consumption. The results suggested that education and occupation are important factors related to alcohol-related problems in Japanese employees.