BoneKEy Reports | BoneKEy Watch
Poor vascularization may not be a factor in nonunion fractures
DOI:10.1038/bonekey.2012.41
It has generally been accepted that vascularization is essential for fracture healing, and Garcia et al. began this study with the hypothesis that inadequate levels of vascular endothelial growth factor (VEGF) and reduced angiogenesis resulted in an increased risk of nonunion fractures.
Their supposition was tested using mice with experimentally induced femur fractures that were maintained for 70 days with a gap size of 0.25 mm (union fractures) or 1.80 mm (nonunion fractures). Vascularization varied with time after fracture, but was similar in both groups at all time points (3, 7, 14, 21, 28 and 70 days). Surprisingly, vascularization and VEGF expression were greater in the nonunion group after 14 days, suggesting that nonunion fractures did not result from a failure of VEGF expression or of angiogenesis.
Analysis of other factors demonstrated a significantly decreased expression of bone morphogenetic factors 2 and 4, which altered the ratio of angiogenic to osteogenic growth factors. The authors propose that therapy for nonunion fractures should shift its focus and should stimulate osteogenesis rather than angiogenesis.
Editor's comment: This study revealed that normal VEGF expression and vascular response after fracture were similar in union and nonunion fractures. The conclusion that the vascular response is adequate in fractures that go on to become nonunion is against long-held orthopedic paradigms and needs confirmation in other models.
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