Timing for removal of the external fixator without retraction of elongation zone during the mineralization stage in SD rat models of distraction osteogenesis
10.3760/cma.j.cn115530-20240302-00099
- VernacularTitle:大鼠牵张成骨模型拆除外固定延长器后牵张区回缩时限的实验研究
- Author:
Bin WANG
1
;
Jiale JIANG
;
Kang CHENG
;
Guizu GAO
;
Ling PENG
Author Information
1. 唐山市第二医院党政综合办，唐山 063000
- Publication Type:Journal Article
- Keywords:
Ilizarov technique;
Osteogenesis;
Distraction;
External fixators;
Rats;
Retraction of elongation zone
- From:
Chinese Journal of Orthopaedic Trauma
2024;26(12):1076-1083
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To explore the timing for removal of the external fixator without retraction of elongation zone during the mineralization stage in SD rat models of distraction osteogenesis (DO).Methods:Forty-two 12-week-old male Sprague-Dawley rats were randomly divided into 6 groups (groups A to F, n=7). The external fixator was removed at 1 to 6 weeks during the mineralization stage in groups A to F, respectively. To establish SD rat models of DO, after 4 threaded needles were inserted into the left femur horizontally and vertically, an external fixator was installed after osteotomy. A Kirschner wire was next inserted into the medullary cavity. After the incubation period (5 days), bone elongation lasted for 14 days until 7.0 mm was extended. Three rats were randomly selected from each group and sacrificed. After decalcification of the elongation zone, histological hematoxylin-eosin staining was performed. Radiographs were taken before removal of the external fixator and 5 weeks after removal of the external fixator for the remaining 4 rats in each group. The HE staining results, length of initial elongation zone, and retraction length of elongation zone were compared between groups. Results:HE staining showed large patches of fibrous tissue and a few immature small blood vessels in the elongation zone in group A, a small number of hypertrophic chondrocytes and fibrous junctions in the elongation zone in group B, some chondrocytes, osteocytes and fibrous tissue in the elongation zone in group C, a large number of chondrocytes on both sides of the elongation zone and fibrous connection in the center of the elongation zone in group D, a decreased number of mature hypertrophic chondrocytes and partial bone marrow in the elongation zone in group E, and a small number of chondrocytes and a partially recanalized medullary cavity with bone marrow in the elongation zone in group F. The lengths of initial elongation zone in groups A, B, C, D, E and F were, respectively, (6.98±0.14) mm, (7.02±0.18) mm, (7.02±0.08) mm, (7.02±0.11) mm, (7.01±0.18) mm and (7.00±0.12) mm, showing no statistically significant differences ( P>0.05). The lengths of retraction of elongation zone in groups A and B [(4.34±0.78) mm and (3.45±0.57) mm] were significantly longer than those in groups D, E and F [(0.16±0.17) mm, (-0.02±0.14) mm, and (0.03±0.82) mm] ( P<0.05). The timing for removal of the external fixator without retraction of elongation zone was the 4th week during the mineralization stage (group D); the healing index was 87 d/cm and the non-retraction index 67 d/cm in group D. Conclusion:In the SD rat models of DO, removal of the external fixator at 4 weeks and later during the mineralization stage may not lead to retraction of the elongation zone.
