Safety entry point, size and direction for placement of thoracic pedicle screw--a cadaveric study.

BACKGROUND: Understanding of the pedicle anatomy is necessary for pedicle screw placement; however, there have been few Thai studies reporting on thoracic pedicle morphometry. OBJECTIVE: To determine important anatomical measurements for thoracic pedicle screw fixation. MATERIAL AND METHOD: T1-T12 vertebral pedicles were evaluated in 27 cadavers. The diameter angle, length and entry point of the pedicle were measured. RESULTS: The transverse diameter was smaller than the sagittal diameter at all levels. The narrowest transverse diameter was at the T5 level in males and T4 level in females. The pedicle diameter in males was statistically significantly greater than in females at all levels except at the T12 level. Most pedicles with a transverse diameter of 5.0 mm or less were found at the T4, T5, T6 and T7 levels. The transverse angle was widest at the T1 level; it faced medially at all levels. The sagittal angle was widest at the T12 level andfaced cephaladly at all levels. The axis length was shortest at the T1 level. Most entry points were at the inferolateral zone. CONCLUSION: A 4-mm diameter screw should be used carefully at the mid-thoracic levels for Thai people, especially females. Screw lengths of less than 30 mm are safe for placement at all levels. The safe zone for the pedicle entry point is in the inferolateral zone.

Gender difference in accumulation of calcium and phosphorus in the left coronary arteries of Thais.

To examine whether there were gender differences in compositional changes of the coronary artery with aging, the authors investigated the gender difference in age-related changes of elements in the left coronary arteries of Thais by direct chemical analysis. After ordinary dissections by students at Chiang Mai University were finished, the left coronary arteries were resected from Thai subjects. The Thai subjects consisted of 69 men and 34 women. The ages of the male subjects ranged from 25 to 87 years (average age = 62.6 ± 11.4 years) and of the female subjects from 24 to 86 years (average age = 59.4 ± 14.6 years). After incinerating the arteries with nitric acid and perchloric acid, the element content was determined by inductively coupled plasma-atomic emission spectrometry. The Ca and P contents tended to increase in the left coronary arteries of men with age, but the increases were not statistically significant. In the left coronary arteries of women, the Ca and P contents increased significantly and progressively with aging. In addition, the Na content increased significantly in the left coronary arteries of both men and women with aging. The differences in the average contents of Ca and P by age group were observed between the left coronary arteries of men and women. With Student's t test, significant gender differences in the average contents of Ca and P were found in both the 40s and the 70s. The Ca and P contents of the left coronary arteries in the 40s were significantly higher in men than in women. In contrast, the Ca and P contents in the 70s were significantly higher in women than in men. These results indicated that the accumulation of Ca and P in the left coronary arteries of Thais occurred at least 10 years earlier in men than in women, but a higher accumulation of Ca and P in old age occurred in the left coronary arteries of women compared with those of men. The present study revealed that there were significant gender differences in the left coronary arteries with regard to the accumulation of Ca and P with aging. It is reasonable to presume that taking clinical findings into consideration, the gender differences in the left coronary arteries may result from hormonal and/or genetic factors rather than lifestyle factors.

Age-related changes of elements in the tendons of the peroneus longus muscles in Thai, Japanese, and monkeys.

To elucidate compositional changes of the tendon of the peroneus longus muscle with aging, the authors investigated age-related changes of elements in the insertion of tendons of the peroneus longus muscle (peroneus longus tendons) in Thai, Japanese, and monkeys and the relationships among element contents by direct chemical analysis. After ordinary dissections at Chiang Mai University and Nara Medical University were finished, the peroneus longus tendons were resected from the subjects. The peroneus longus tendons were also resected from rhesus and Japanese monkeys bred in Primate Research Institute, Kyoto University. The wraparound regions of the insertion tendons of the peroneus longus muscle in contact with the cuboid bone were used as the peroneus longus tendon. After ashing with nitric acid and perchloric acid, element contents were determined with an inductively coupled plasma-atomic emission spectrometer. It was found that there were no significant correlations between age and the seven elements, such as Ca, P, S, Mg, Zn, Fe, and Na, in the peroneus longus tendons of Thai and Japanese. The Ca content higher than 10 mg/g was contained in seven cases out of 34 peroneus longus tendons of Thai (incidence = 20.6%) and in one case out of 22 peroneus longus tendons of Japanese (incidence = 4.5%), respectively. All of the peroneus longus tendons with the Ca content higher than 10 mg/g were found in Thai and Japanese men. In the peroneus longus tendons of monkeys, the Ca and P content increased suddenly at 2 years of age and reached to about 40 mg/g at 5 years of age. Thereafter, the Ca and P content did not increase in the peroneus longus tendons of monkeys at old age. Regarding the relationships among element contents, significant direct correlations were found among the contents of Ca, P, Mg, Zn, and Na in Thai and monkeys, whereas significant inverse correlations were found between S and element contents, such as Ca, P, Mg, Zn, and Na, in Thai and monkeys.