Radioactive isotopes in fractures of the neck of the femur.

Many workers have over many years tried to find a reliable method of detecting damage to the blood supply of the femoral head soon after fracture of the neck of the femur. Up to now the most promising method has been that in which a radioactive isotope is given intravenously and the amount of it appearing in the femoral head and trochanter is measured. In 1950 Tucker published a preliminary report on the use of radioactive phosphorus. The isotope was given intravenously one hour before operation at which small samples of bone were removed with a hollow drill from the femoral head and trochanter. The dried ash of these samples was measured for its p32 content and the result was expressed as a ratio between the P32 contents of the trochanter and head. Before this, animal experiments had confirmed that the ratio was normally 1 O but that if all vessels to the head of the femur were divided a ratio of up to 14 was obtained; evidently some absorption of p32 into the head from the surrounding synovia and blood occurred. Tucker applied this method to thirteen patients, carrying out the investigation at the time of nailing the fracture. With a one to two years’ follow-up there appeared to be a good correlation between a normal or near-normal ratio and bony union. He found that a ratio of up to 30 could be regarded as indicating a satisfactory blood supply in the head. He found no harmful effects from the use of P32. Boyd in 1951 made a preliminary report on the use of this method in animals and in a few patients, taking direct measurements with a needle counter. Arden and Veall in 1950 reported on the use of P32 with bone sampling in twenty-two cases. They studied sixteen fractures of the femoral neck and six intertrochanteric fractures, following them up for six to twelve months. In all the five surviving patients with intertrochanteric fractures union occurred and the ratios were normal (04 to 20). In nine of the sixteen cases of fracture of the femoral neck the ratios were low (1 to 2 3) yet three of these failed to unite (possibly because of faults in the nailing technique). In 1955 Boyd, Zilversmit and Calandruccio published a more extensive series of cases in which the method had been used firstin dogs and then in patients. They found that in dogs the p32 level reached a plateau in about one and a half hours, in both the head and trochanter of the femur. Even if the blood supply to the head were damaged a plateau was stillreached in the head in about the same time but the ratio was altered by the P32 reading in the head being diminished. They found that in dogs the distribution of P32 in the normal femoral head varied and that counts in the posterior inferior segment of the head were higher than in the posterior superior segment. The weight-bearing portion of the head had the lowest count. Autoradiographs of femoral heads removed from patients showed patchy areas of radioactivity, the unexposed areas corresponding to zones of avascularity. They used the method in thirty-two patients with fresh fractures of the neck of the femur and in ten with fresh intertrochanteric fractures (controls). As far as possible they took readings from the weight-bearing area of the head in each case. The ratios in the cases of fracture of the femoral neck varied from 1 3 to 16 7 and in the cases of trochanteric fracture from 0 7 to 1 9. The period of observation was not long enough to permit a comparison between the clinical results and the ratios of radioactivity. The results of these studies are summarised in Table I. This paper records the results of an extended trial of the use of P32 for the measurement of the vascularity of the head of the femur after fracture of the femoral neck.