Objective: To define the occurrence rate, time course, and potential mechanism of hyponatremia in patients after Frankel Class-A acute cervical spinal cord injury. Methods: Analysis of data obtained from a retrospective review of blood and urine records of 35 hospitalized cases from 1992 to 1998. Results: Patients were admitted after (2.8±1.8) days postinjury and had been hospitalized for (52±13) days. Hyponatremia, the occurrence rate of which was 100%, developed at a mean time of (4.5±1.2) days postinjury, reached its nadir at the end of (14±3) days and recovered to normal at (39±10) days. Fifteen (42.88%) cases did not recover from hyponatremia in the hospitalized period. Patients were suffering from hypercapnia, hypernitremia, polyuria, and hyper-natriuresis besides kalemia. Conclusion: Severe and obstinate hyponatremia is a very common complication of cervical spinal cord injury. The mechanism may be related to the Cerebral Salt Wasting Syndrome.

BACKGROUND: The changes in trabecular bone microarchitecture in osteoporosis have aroused much attention. The decrease in the number of trabecular nodes and increase in the number of free ends are found in osteoporosis, but the mechanism is still unclear.OBJECTIVE: To observe the trabecular remodeling process in ovariectomized rats as the osteoporosis models electron microscopically, and to explore the reasons for the decrease in the number of trabecular nodes and increase in the number of free ends.DESIGN: Randomized and controlled animal trial.SETTING: Department of Orthopedics, Third Hospital of Peking University.MATERIALS: The experiment was conducted in the Animal Laboratory, Third Hospital of Peking University from September 1999 to February 2000. Thirty-six female Wistar rats of 3 months old and 240-280 g were selected and randomly divided into ovariectomized group and control group with 18 rats in each group. The rats were observed at 4,8, and 12 weeks postoperatively with 6 rats at each time point.METHODS: The rats of ovariectomized group were subjected to ovariectomy 1 week after feeding, but the control group was not. The changes of proximal tibia trabecular microarchitecture was observed under scanning electron microscope at 4, 8 and 12 weeks, respectively, and the osteoclast, osteoblast, and structure of cell organs were observed under transmission electron microscope.MAIN OUTCOME MEASURES: [1]The re modeling process after ovariectomy by electron microscope; ②morphological changes of trabecular bone.RESULTS: [1]Scanning electron microscope observation showed that trabecular bone remodeling was distributed in every region of trabecular microarchitecture, especially St and Nd-St region. After ovariectomy, the transverse trabecular was easier to be perforated and broken; the trabecular network was almost intact at 4 weeks, but gradually damaged at weeks 8 and 12; moreover, the collagen fibers on the surface of trabecular bone were scrappy, disorder and thinner. ②By the transmission electron microscopic study, the tibial osteoclast were found active at 12 weeks. When absorbing cancellous bone, osteoclast closely adhered to its surface, and digitations stretched into the cancellous bone. The shape and size of digitations were significantly different, and around them, lucent area was observed. Osteoclast was polynucleation with abundant kytoplasm, and there were plenty of Golgi complex, smooth endoplasmic reticulum and mitochondrium. Lysosome inclusion compounds with different sizes and electron density were found in cells. Osteoblast was rarely found, and cell edge was rough, with bone lacuna.CONCLUSION: Bone remodeling is significantly active in St and Nd-St region of trabecular bone in ovariectomized rats.This may be the reason for the decrease in the number of trabecular nodes and increase in the number of free ends.

Objective To investigate the clinical outcomes of three kinds oi internal fixations via posterior approach for treating adjacent two-segment thoracic and lumbar vertebral fractures.Methods A retrospective analysis was done on data of 34 patients with adjacent two-segment thoracic and lumbar vertebral fractures treated between 2003 and 2010.The treatments included three different pedicle screw fixations via posterior approach,ie,fixation with four verlebrae and four screws (Group Ⅰ,n ＝ 14),fixation with four vertebrae and six screws ( Group Ⅱ,n ＝ 11 ),fixation with four vertebrae and eight screws ( Group Ⅲ,n ＝ 9).The changes of spinal Cobb' s angle before and after operation and at the last final follow-up were statistically analyzed.Oswestry disability index (ODI) score,Denis pain scale and Denis work scale at the final follow-up were evaluated.Also,the recovery of neurological function was observed.Results The duration of follow-up was average 24 months (range,10-48 months).The neurological function of all the patients recovered to some degree.Two patients had pedicle screw breakage and one had spontaneous fusion of the collaprsed vertebra in Group Ⅰ.The Cobb' s angles of the three groups were decreased immediately after operation,but all obtained some degree of enhancement at the final follow-up.In Group Ⅰ,the mean Cobb's angle was (7.5 ±3.0)° postoperatively and then improved to ( 13.7 ±5.1 )°at the final follow-up,with correction loss of (6.2 ±2.1)°.In Group Ⅱ,the average Cobb's angle was( 1.4 ± 1.5) ° postoperatively and later increased to (4.5 ± 2.4)° at the final follow-up,with correction loss of (3.1 ± 1.1 )°.In Group Ⅲ,the mean Cobb' s angle was ( 0.0 ± 1.1 )° postoperatively but was increased to ( 1.3 ± 1.2 )° at the last follow -up,with correction loss of ( 1.3 ± 0.0 1 )°.The three groups showed statistical difference regarding the correction loss of Cobb' s angle ( P ＜ 0.05 ).Group Ⅱ and Group Ⅲ showed no significant differences in aspects of ODI score and Denis work and pain scale at the final follow-up,but the differences were significant when Group Ⅰ was compared with Group Ⅱ and Group Ⅲ (P ＜ 0.05 ).Conclusions The posterior transvertebral pedicle screw fixation with 4 vertebrae and 8 screws for adjacent two-segment thoracic and lumbar vertebral fractures is beneficial to gaining well reduction and fixation,maintaining deformity correction,preserving motion segment and releasing pain.The operation,a simple and convenient technique,has the prospect of clinical application.