The effects of roentgen therapy on the host acceptance of autogenous bone grafts in dogs.

Abstract

THE EXPERIMENTAL study reported herein was undertaken to determine the effects of radiation therapy on autogenous bone grafts. Before this research was instituted, an anterior cervical fusion had been accomplished with autogenous iliac bone in a patient to prevent spinal collapse in an area of Hodgkin's disease of the vertebral body. Radiation therapy was believed indicated, but little information regarding optimum time for such treatment in this circumstance could be found. Thus, the following study was undertaken. Experimental Study Materials and Methods: Eight mongrel dogs were employed in this study. In every animal the medial femoral condyle was approached surgically, and the periosteum of each femur was elevated over the condyle just proximal to the articular cartilage. A ½-inch trephine was used to remove from each femoral condyle a cortical plug of bone with the underlying cancellous bone attached. These two plugs were exchanged, being inserted into the defects: the plug from the left femoral condyle was inserted into the right femoral condyle defect and vice versa. The periosteum of each side was then closed with three-zero silk sutures. The vastus medialis was reapproximated also with three-zero silk sutures. The skin was closed with one-zero silk subcuticular sutures. No dressings were utilized. The 8 dogs were classified into two groups. The four dogs in Group 1 received 2,000 R directed to the right femoral condyle, beginning after the sixth postoperative week. In Group 2 the right femoral condyle received 2,000 R beginning after the second postoperative week. The dogs of Groups 1 and 2 were sacrificed during the fourth, sixth, eighth, or twelfth weeks after completion of the course of radiation. The femur on the right side was exposed to a generous field of radiation. The opposite femur was used as the control. Radiation of 2.4 mm Cu h.v.l. (peak of 250 kv) at a 50 cm distance was employed to deliver 2,000 R to the midplane of the femur in 10 equal increments during a period of fourteen days. Serial roentgenograms were obtained up to the time of death. At that time the aorta was injected with a mixture of “Micropaque” (aqueous suspension of barium) and Berlin blue. The distal femora with the grafts intact were decalcified in 10 per cent formic acid for four weeks. The femora were then split longitudinally through the grafts. The anterior halves were sectioned about 200 μg thick to show the vascularization. The posterior halves were processed by the Spalteholz technic for making bone transparent (Fig. 1). Results Serial roentgenograms demonstrate radiographic evidence of incorporation of each graft on the control and on the irradiated sides of each dog. The grafts on the irradiated sides, however, consistently show increased bone density appearing three weeks after the conclusion of the irradiation.