Depression of bone blood flow after blunt trauma. A fracture study in the adult rabbit.

Delayed union of long bone fractures is commonly ascribed to deficient vascularity, but bone blood flow after fractures caused by blunt trauma has yet to be quantified. We have studied blood flow to the tibial diaphysis after such fractures, and compared the results with those found after osteotomy. 24 adult New Zealand White rabbits were studied. Fractures of the tibial shaft were produced under anesthesia by percussion and immobilized in a cast. Blood flow to the tibial diaphysis was measured at 1 and 2 weeks using the microsphere method. Cortical blood flow proximal to the fracture was increased at both time intervals, and distally at 2 weeks. Marrow flow was depressed distally at 1 week. Marrow flows at 1 week and distal cortical flows at 2 weeks were reduced in comparison with osteotomies studied previously. This depression of blood flow response by blunt trauma prompts further investigation of the role of vascular factors in delayed union.