Figure 1.
Diagrammatic illustration of the biological effects of VAC.
Figure 2.
An X-ray scan ensured the depth of decompression (A). A negative pressure connection tube was employed as shown in (B).
Figure 3.
H&E staining of samples from each experimental group.
Normal control group (A): Intact, dense, full trabecular bone, clearly visible bone cells in the trabecular bone (arrow), isolated and scattered empty lacunae, abundant bone marrow hematopoietic cells, relatively few fat cells and normal morphology. Model control group (D): Fractured trabecular bone with fragments, an absence of bone cells from some bone lacunae (→), an increased number of empty lacunae, disorganized or absent bone marrow structure and necrosis of a large number of bone marrow cells. Core decompression group, week 4 (B): New capillaries and a small number of ossification centers around a tunnel (→), swelling of the bone marrow compared with the normal control group, an increased number of fat cells, thinning and fractured trabecular bone, a slight increase in the number of empty lacunae and nuclear condensation of a small number of cells. Core decompression group, week 8 (C): An increased number of bone cells in the trabecular bone, an increased number of bone marrow hematopoietic cells (→) and a decreased number of empty lacunae. Negative pressure group, week 4 (E): Disarranged new trabecular bone and a large number of surrounding osteoblasts (→); trabecular bone fracture and necrotic bone marrow cells remain. Negative pressure group, week 8 (F): Intact trabecular bone, clearly visible bone cells in the trabecular bone (→), abundant bone marrow hematopoietic cells, relatively few fat cells and normal morphology resembling normal bone tissue.
Figure 4.
Immunohistochemical staining of VEGF in the femoral heads from each experimental group (200× magnification).
Model control group: Low VEGF expression in osteoblasts and vascular endothelial cells in the subchondral bone tissue of the femoral head (A). Normal control group: Some VEGF expression in osteoblasts and vascular endothelial cells in the femoral head (D). Core decompression group, week 4 and week 8: Strong VEGF expression in osteoblasts and vascular endothelial cells in the fibrous granulation tissue (B, C). Negative pressure group: Strong expression at both week 4 and week 8 (E, F), which was higher compared with expression in the core decompression group.
Figure 5.
Immunohistochemical staining of BMP-2 in the femoral heads from each experimental group (200× magnification).
Model control group: Low BMP-2 expression in osteoblasts and fibroblasts in the subchondral bone tissue of the femoral head (A). Normal control group: BMP-2 expression in the osteoblasts and fibroblasts of the femoral head (D). Core decompression group, week 4 and week 8: Strong BMP-2 expression in osteoblasts and fibroblasts (B, C). Negative pressure group: Strong expression at both week 4 and week 8, which is higher compared with expression in the core decompression group.
Figure 6.
TEM (15000× magnification) of the femoral heads from each experimental group.
Normal control group (A): Osteogenic cells were round or oval, large in size and rich in organelles. Model control group (D): Osteoblasts were flat with swollen mitochondria with degenerated vacuoles and relatively few rough endoplasmic reticula (rER) were present in the cytoplasm. Negative pressure group, week 4 (B) and week 8 (C): Osteoblasts were round or oval, the cells gradually increased in size and the number of rER increased in the cytoplasm and formed membranous tubes with attached ribosomes. In addition, there were numerous mitochondria. Nuclear staining was light and the structure was intact. Core decompression group, week 4 (E) and week 8 (F): ER and mitochondria numbers in the cytoplasm of the osteoblasts were increased, but increases were to a lesser extent compared with the negative pressure group at various time points.
Figure 7.
Femoral head microvascular ink staining images (100× magnification) from each experimental group.
In the model control group, the small number of ink-stained blood vessels were thin and presented primarily in the bone marrow cavity of the femoral head (Figure A). In the normal control group, there were relatively more ink-stained blood vessels with a thick vascular lumen in the bone marrow of the femoral head (Figure D). Compared with the model control group, the core compression group had more ink-stained blood vessels with a thicker vascular lumen in the bone marrow of the femoral head at week 4 (B) and week 8 (C). However, there was no significant difference between week 4 and week 8. In the negative pressure group, the number of ink-stained blood vessels with a thicker vascular lumen in the bone marrow of the femoral head was increased significantly at week 4 (E) and week 8 (F). Compared with week 4, there was significant improvement at week 8, and the parameters at both time points were superior to those of the normal control group.
Figure 8.
Comparison of femoral head microvascular density among experimental groups.
Each experimental groups was significantly different compared with the model control group (P<0.01, n = 8). The negative pressure group and the core decompression group were significantly different at weeks 4 and 8 (P<0.01, n = 8).
Figure 9.
VEGF and BMP-2 mRNA levels over time in the core decompression and negative pressure groups.
At weeks 1, 2, 3, 4, 5, 6, 7 and 8, VEGF and BMP-2 expression levels increased significantly and the peak expression levels lasted longer in the negative pressure group compared with the core decompression group (n = 6).