Preparation of peri-epiphyseal fracture models in young rabbits：cross-epiphyseal plate internal fixation affects epiphyseal growth? / 中国组织工程研究

ABSTRACT

BACKGROUND:There are various therapies for children limb fractures involving the epiphysis or the metaphysis. According to the different methods, studies on the growth of the epiphyseal plate are a lot, most of which focus on the effects of Kirschner wires with different diameters or holow screw internal fixation on the development of epiphyseal plate. However, there are rare studies on the influence of cross-epiphyseal plate internal fixation on the growth of epiphyseal plate as wel as the influence level. OBJECTIVE:To prepare a peri-epiphyseal fracture model in young rabbits and to observe the effects of cross-epiphyseal plate implantation and removal on the growth of epiphyseal plate. METHODS: Traverse fracture models were made 5 mm above the right femoral distal epiphyseal plate of 60 young rabbits, and then fixed with suitable “L” steel plate and four screws across the epiphyseal plate and peri-epiphyseal fracture line. The left side served as control. Eight rabbits were kiled and observed at 2, 4, 8, 12 weeks after modeling, respectively, to take out the femoral specimens for measurement of femoral length, thickness of the epiphyseal plate, and number of mastocytes per unit column. Histopathology observation was done and changes in mastocytes and thickness of the epiphyseal plate were detected. Another seven rabbits were selected to remove the metal plate, continued to feed for 2 weeks and finaly executed to observe the above-mentioned indexes. RESULTS AND CONCLUSION: (1) There were significant differences in the above indexes between the plate and control groups at 4, 8, 12 weeks after modeling (P 0.05). These findings indicate that within 2 weeks after cross-epiphyseal plate internal fixation, proper pressue has no remarkable influence on the growth of epiphyseal plate; but after persistent internal fixation (> 4 weeks), the growth of epiphyseal plate can be partialy or completed retarded. (2) At 2 and 4 weeks after modeling, the plate was removed, and 2 weeks later, the femoral length, thickness of the epiphyseal plate and mastocyte counting per unit column were improved to different extents, and there were no differences between the plate and control group (P > 0.05). At 8 and 12 weeks after modeling, the plate was removed, and 2 weeks later, the femoral length and thickness of the epiphyseal plate were shortened, and the number of mastocytes per unit column was decreased obviously, which significantly differed from the control group (P < 0.001). These findings indicate that the chondrocytes in the proliferative and hypertrophy layers lose the differentiation and proliferation abilities, and the femoral length and epiphyseal plate thickness are difficult to recover.