Behaviour of an artery enclosed within a normal or hypertrophic callus of a long-bone fracture

The behaviour of the brachial artery enclosed in a hypertrophic or a normal callus was investigated in experimentally produced fractures of the humerus in 22 dogs. The brachial artery was displaced in a bony groove created at the fractured ends of the bone. The fracture was immobilized with a metal plate and four screws. The progress of the callus formation was studied and the patency of the artery was evaluated. In 15 out of the 22 animals a medium-sized or hypertrophic callus had developed that engulfed the brachial artery without obstructing its lumen and blood flow. In five dogs the fracture site was infected and the resultant osteomyelitis obstructed the artery. In the remaining two dogs the arterial lumen was extremely narrowed, due to breaking of the plate and formation of pseudarthrosis in one and injury of the artery in the other. Unless complicated by infection resulting in vascular occlusion, callus at the fracture site may engulf an artery without interference in its patency and blood flow. The possible involvement of a functioning artery within a callus or a mass of heterotopic ossification (myositis ossificans) should be kept in mind during surgical treatment of old fractures, hypertrophic callus with pseudarthrosis or extensive heterotopic ossification.