Bone blood flow response to surgical trauma

The evolution of bone plate design has been with a view to reducing the interface contact between the plate and the underlying bone thereby limiting the perfusion deficiency that develops. Little consequence, however, has been attributed to the drilling of holes in the steps prior to bone plate application; the work present herein attempts to define the vascular response of bone to the trauma of drilling holes. Anaesthetized sheep underwent the creation of drill holes in both tibiae and metatarsi. Animals were then heparinized and euthanatized. Utilizing femoral cannula, perfusion of the vasculature ensued; spalteholz (India ink), disulphine blue and radiocontrast material (barium sulfate). Decalcified histology was performed and correlated with the perfusion studies. Regions of perfusion deficiency were observed immediately adjacent to, and removed from, the drill hole site. Radiographic images showed substantial haematoma formation and vascular disruption in the vicinity of the drill hole site. Histologically, blood vessels immediately adjacent and distal to the drill hole site, contained a proteinaceous/cellular material occluding the vascular space. Our findings support the proposal of a short-term obstruction in cortical blood flow which may contribute to later adaptational osteopaenia following bone plate application. We have observed an acute vascular insufficiency in cortical bone directly related to the trauma of drilling screw holes.