[Relationship and risk factors of osteonecrosis of femoral head after internal fixation of femoral neck fracture with serum bone metabolism and vasoactive factors].

OBJECTIVE: To study the relationship between osteonecrosis of femoral head after internal fixation of femoral neck fracture and serum bone metabolism, vascular active factors, and analyze the risk factors. METHODS: Total 150 patients with femoral neck fracture who underwent reduction and internal fixation from April 2016 to April 2019 were selected, including 83 males and 67 females. According to whether there was necrosis of femoral head after operation, they were divided into necrosis group(32 cases) and non necrosis group (118 cases). Before operation and 1, 3, 5 days after operation, the serum levels of beta-C terminal cross-linked telopeptides of typeⅠ collagen(ß-CTX), N-telopeptide of typeⅠ procollagen(PINP), nitric oxide (NO), Endothelin-1 (ET-1) were measured. The clinical characteristics of the two groups were compared. The risk factors of postoperative femoral head necrosis were analyzed by logistic regression model. The value of serum indexes in predicting postoperative femoral head necrosis was analyzed by ROC curve. RESULTS: There was no significant difference in the levels of serum PINP and ß-CTX between necrotic group and non necrotic group before operation and 1, 3 and 5 days after operation(P>0.05). There was no significant difference in the levels of serum NO and ET-1 before operation and 5 days after operation(P>0.05). There were significant differences in the levels of serum NO and ET-1(P<0.05), fracture type, preoperative traction ratio and reduction quality (P<0.05). Logistic regression analysis showed that the decrease of serum NO content and the increase of ET-1 content at 1 day after operation, Ⅲ-Ⅳ fracture and Ⅲ-Ⅳ reduction were the risk factors of femoral head necrosis;ROC curve analysis showed that serum NO and ET-1 content at 1 day after operation had predictive value for femoral head necrosis, and the best cut-off points were 26.55 µmol / L and 7.785 µg / L, respectively. CONCLUSION: The content of serum NO and ET-1 on the first day after operation can predict the necrosis of femoral head.

Decreasing brown bear (Ursus arctos) habitat due to climate change in Central Asia and the Asian Highlands.

Around the world, climate change has impacted many species. In this study, we used bioclimatic variables and biophysical layers of Central Asia and the Asian Highlands combined with presence data of brown bear (Ursus arctos) to understand their current distribution and predict their future distribution under the current rate of climate change. Our bioclimatic model showed that the current suitable habitat of brown bear encompasses 3,430,493 km2 in the study area, the majority of which (>65%) located in China. Our analyses demonstrated that suitable habitat will be reduced by 11% (378,861.30 km2) across Central Asia and the Asian Highlands by 2,050 due to climate change, predominantly (>90%) due to the changes in temperature and precipitation. The spatially averaged mean annual temperature of brown bear habitat is currently -1.2°C and predicted to increase to 1.6°C by 2,050. Mean annual precipitation in brown bear habitats is predicted to increase by 13% (from 406 to 459 mm) by 2,050. Such changes in two critical climatic variables may significantly affect the brown bear distribution, ethological repertoires, and physiological processes, which may increase their risk of extirpation in some areas. Approximately 32% (1,124,330 km2) of the total suitable habitat falls within protected areas, which was predicted to reduce to 1,103,912 km2 (1.8% loss) by 2,050. Future loss of suitable habitats inside the protected areas may force brown bears to move outside the protected areas thereby increasing their risk of mortality. Therefore, more protected areas should be established in the suitable brown bear habitats in future to sustain populations in this region. Furthermore, development of corridors is needed to connect habitats between protected areas of different countries in Central Asia. Such practices will facilitate climate migration and connectivity among populations and movement between and within countries.