Establishing a rabbit model of peripheral partial growth plate closure by immediate filling after partial growth plate resection

Zhihong ZHU; Ruijiang XU

ABSTRACT

BACKGROUND:

Animal models of peripheral partial epiphyseal plate closure are commonly used in related trials.

OBJECTIVE:

To modify the original animal models of distal femoral partial epiphyseal plate closure.DESIGN, TIME AND

SETTING:

A self-controlled trial was performed at the Experimental Animal Center of General Hospital of Chinese PLA from March to October 2007.MATERIALS Twenty healthy New Zealand rabbits of 4-6 weeks old weighing 1.0-1.5 kg were selected.

METHODS:

A straight incision about 2 cm was made in lateral knee of 20 rabbits. The subcutaneous tissues and knee capsule were cut open to expose distal femoral condyle. The condylar plate line was clear. Two holes were drilled in the fight lateral condyle, about 3.0-4.0 mm deep, and partial normal epiphyseal plate (about 33%-44% of the total growth plate) was removed. An incision deep to periosteum was created in the left side and regarded as self-control.MAIN OUTCOME

MEASURES:

Femoral length, valgus angle of the distal femur, and femoral deformity were detected by X-ray photograph, and gross observation. Bone bridge formation of bilateral femora was observed by histological examination.

RESULTS:

One rabbit died of diarrhea 31 days after surgery, and 19 were included in final analysis. ①Radiographs showed that the mean length of left femur (control side) was significantly longer but valgus angle was significantly smaller than the right side (experimental side) 4 months after surgery (P ＜ 0.01). The left distal femur averagely grew for 2.27 cm,accounted for 57.6% of the overall femoral growth, and the right side averagely grew for 0.45 cm, accounted for 21.4% of the overall femoral growth.②Four months after surgery, femoral appearance of the control side was normal, with smooth and complete condylar and facies articularis patellae. While, the experimental side femur was significantly shortened, and severe vaigus deformity was observed in the distal femur. ③Five weeks after surgery, layer cells of the epiphyseal plate arranged regularly in the control side. Bone trabecula with many fibers was found in bone defect cavity of the experimental side, and the cell layer of the remnant epiphyseal plate was decreased. The epiphyseal plate was closed in the control side,and bone trabecula of the experimental side was thickened 10 weeks postoperatively.

CONCLUSION:

This modeling method is simple, efficient, and easy to manipulate; in addition, the bone bridge area is controllable. The models can meet the study demands for peripheral partial epiphyseal plate closure, and are significant for filling material selection during treatment.