Irradiation of bone lesions in the presence of metallic intramedullary fixation.

Abstract

THE TREATMENT of pathologic fractures of the long bones, especially the femur, has been greatly forwarded by the use of the intramedullary nailing method of Küntscher (1940). The operation is simple, fixation is maintained without supplementary apparatus, immediate activity is usually possible, and there is a tremendous decrease in morbidity. Experience abroad has been confirmed in this country. A recent editorial by Cave (1949) acknowledges the great value of intramedullary fixation in stabilizing painful pathologic fractures of the femur. Pathologic fractures of the long bones resulting from both primary and secondary bone tumors have been treated satisfactorily by intramedullary nailing (Table I). It has been suggested that in the presence of bone lesions where spontaneous fracture appears to be imminent, intramedullary nailing be carried out as a prophylactic measure (Griessmann and Schüttemeyer, 1947). The majority of patients treated in this manner have received no further therapy. Occasionally irradiation has been given in order to control local tumor growth and promote recalcification and healing. It is the purpose of this paper to discuss the effect of the presence of a large metallic intramedullary nail upon the application of radiation therapy to primary or secondary bone lesions. Methods A femur was obtained from a freshly embalmed cadaver. This was incorporated into a wax model so constructed that it closely conformed in configuration and density to the normal soft tissues about the upper end of the femur. A roentgenogram of the completed model showed it to have a uniform consistency, without cracks or air bubbles. With the use of this model, a series of measurements was made before and after the insertion of a “cloverleaf” intramedullary nail (1 × 44 cm.) made from S.M.O. (Zimmer and Company). The nail was placed in the medullary cavity just as in the treatment of fractures. The model was irradiated through an anterior port 10 cm. square with a General Electric Maximar machine, at 220 kv., 15 ma., with 1.0 mm. copper and 1.0 mm. aluminum filtration, half-value layer 1.7 mm. copper, and a target-object distance of 60 cm. The field was defined with one layer of leaded rubber shields, and later with two layers. No difference was observed. Radiation was measured by means of a Victoreen thimble dosimeter (Fig. 1). All measurements were corrected for temperature and barometric pressure, and have been reduced to roentgens per minute for convenience of presentation. Readings were taken at four points, three areas on the posterior surface of the model and one immediately beneath the posterior cortex of the shaft of the femur (Fig. 2). Roentgenograms were made to demonstrate that the ionization chamber of the dosimeter, in the latter position, was completely shielded by the nail when it was in place.