BACKGROUND: Clinically, children with metaphyseal and periepiphyseal fractures are more common. Internal fixation of the tarsal plate has a more important role in stabilizing the fracture. However, after a certain period of internal fixation, the fixator was taken out. After a certain period of observation, the recovery of the epiphyseal plate was rarely reported. OBJECTIVE: To design an animal model of epiphyseal plate fracture and observe the growth and inhibition of epiphyseal plate after removal of the transepiphyseal steel plate implanted with locking plate for a period of time. METHODS: The 5 mm fracture models of the distal epiphyseal plate of the right femur in 32 young rabbits were established. They were randomly divided into four groups with eight rats in each group. The same type of steel plate and screw was used. Internal fixation of transepiphyseal plate was conducted at periplate fracture line. The internal fixator was removed 2, 4, 8, and 12 weeks after operation. The rabbits were sacrificed after 2 weeks of observation. The femoral specimens were obtained, and the femoral length was measured. The thickness of epiphyseal plate and the number of mast cells were measured by pathological section. Morphological changes of mast cells and epiphyseal plate thickness were observed. The fracture model was used as the experimental group and the distal epiphyseal plate of the left femur was used as the control group. RESULTS AND CONCLUSION: (1) After 2 weeks of internal fixation, the steel plate was removed in the experimental group and the observation was continued for 2 weeks. There was no significant difference in femoral length, epiphyseal thickness and mast cell count between the experimental group and the control group. (2) In the experimental group, the internal fixator was removed at 4, 8 and 12 weeks and the plate was observed for 2 weeks. Compared with the control group, the femoral length, epiphyseal thickness and mast cell count in the experimental group were not completely restored to normal, and the difference was significant (P < 0.05). (3) On the premise that the internal fixator did not injure the epiphyseal plate, the transepiphyseal plate was taken out at the initial stage of internal fixation (≤ 2 weeks), and the plate was observed for 2 additional weeks. The growth and development of the epiphyseal plate were not significantly affected by appropriate pressure. (4) If the pressure limitation lasts for too long (≥ 4 weeks), the time of internal fixation for epiphyseal plate pressure limitation is too long. Although the plate is removed in time, the indexes such as limb length, epiphyseal plate thickness and mast cell count cannot be completely restored to normal, which can lead to partial or complete blockade of epiphyseal plate growth, resulting in limb deformity and stagnation of epiphyseal plate development.

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 orP< 0.001) but not at 2 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.