Objective To investigate the impact of aging and weight bearing on cartilage endplate morphology and chondrocyte apoptosis in rats. Methods The bipedal rat model (n=45) was developed by forelimb amputation and special breeding methods. The normal rats of the same age served as the control group (n=40). When the rats became 3, 6, 9, and 12 months old, 8 rats randomly selected from each group were sacrificed and paraffin-embedded mid-sagittal sections of the L4-5 spine were obtained. Sections were stained with hematoxylin and eosin and the TUNEL procedure was performed. The numbers of apoptotic cells and viable cells in the cartilage endplates of the intervertebral discs were counted, the thickness of the cartilage endplate was measured and the degree of impairment of the cartilage endplate was evaluated. Results Apoptosis first appeared in the cartilage endplate, then increased with aging and resulted in a remarkable decrease in cell density. The apoptotic rate of chondrocytes within the cartilage endplate of the bipedal rat model group was significantly higher than the control group at the 6-month time point. A statistically significant difference was observed in the bipedal rat model group between the 6-month time point and 9-month time point (P<0.05). Correlation analyses indicated that there was a highly negative correlation between the number of the viable cells of the cartilage endplate and the degree of the cartilage endplate degeneration (r=-0.97, P<0.05). Compared with the naturally aged group, the bipedal rat model group experienced more severe degeneration in the structure of the cartilage endplate, more obvious thickening of the cartilage endplate's calcified layer, and more defects in the structure of the cartilage. Conclusions Besides aging, weight bearing is probably a key factor of the increase of chondrocyte apoptosis and the degeneration of vertebral cartilage endplate.

Objective To summarize the epidemiological characteristics of ankle fractures and clinical outcome of open reduction and fixation for the treatment of posterior Pilon fracture with supporting plate. Methods From January 1st,2013 to December 31st,2016,the data of three hundred and twelve patients with ankle fracture in Jinshan Hospital of Fudan University were collected, and 21 cases of posterior Pilon fracture were treated with open reduction and fixation using supporting plate and were followed up,the ankle function was assessed by American Orthopaedic Foot and Ankle Society ankle hindfoot scale. Results There were 312 patients with ankle fractures,180 males,132 females. The age distribution of patients was as follows:1. 28%,12. 82%,14. 42%,24. 04%,28. 53%,11. 54%,6. 09% and 1. 28% in the following age group:≥18 and≤20 years of age,>20 and ≤30 years of age,>30 and ≤40 years of age,40> and ≤50 years of age,>50 and≤60 years of age,>60 and ≤70 years of age,>70 and ≤80 years of age and >80years of age. Traffic accidents (49%),sprains(31%),falling injury (11%),heavy pound(6%) were the main causes of ankle fractures. In terms of fracture types,238 (76. 2%) cases with lateral malleolus,235 (75. 3%) cases with medial malleolus fractures,161 (51. 6%) cases with posterior malleolus,and 105 (33. 7%) cases with trimalleolar fracture,21 (6. 8%)cases with posterior Pilon fracture. 21 patients with posterior Pilon fracture were followed up for 13. 0 to 56. 0 months,with an average of (31. 7±12. 6) months. Postoperative incision infection occurred in 3 patients,of which 1 cases had mild external leakage,and all wounds healed after dressing change. No fracture and screw prolapse occurred in all follow-up patients. The average score of AOFAS was (87. 2± 7. 1) points,of which 9 cases were excellent,10 cases were good,and 2 cases were fair. Conclusion Patients with ankle fractures were more common in males aged 60 and below,while in patients above 60 years old,the majority patients were females. In addition,patients aged 40 to 60 years old accounts for more than half of the population and the most common age group were between 50 and 60 years old. Traffic accidents and sprains are the common causes. The incidence of different fracture types in descending order were as follows: lateral malleolus fractures, medial malleolus fractures,posterior malleolus fractures and trimalleolar fractures. Pilon fracture was a common type of ankle fracture. Clinical outcome of open reduction and fixation for the treatment of posterior Pilon fracture with supporting plate was satisfied.