Effect of physical activity on muscle and bone blood flow after fracture. Exercise and tenotomy studied in rats

In male Wistar rats, a transverse osteotomy of the midshaft of the left femur was performed. The rats were allocated to three groups: 1) one that underwent a 4-week training program 4 weeks after the osteotomy, 2) one that had a tenotomy of the left Achilles tendon to prevent weight bearing, and 3) one that had normal function and activity. Eight weeks after the osteotomy, total bone, proximal diaphyseal, callus, and muscle blood flows were measured using the microsphere technique. Initial and final body weight, bone weight, and callus production were also recorded. There were no differences in bone or muscle blood flow between the three groups. An increase in total bone and muscle blood flows was seen on the osteotomized side. In weight-bearing rats, the callus area was more vascular as compared with the diaphyseal bone. No correlation between callus mass and callus flow was found. Our results support the concept that blood supply is mandatory for fracture healing; however, other factors seem to be decisive for the rate of healing.