Cortisone-induced intrafemoral head pressure change and its response to a drilling decompression method

Intramedullary head pressure changes were studied in a group of cortisone-treated New Zealand white rabbits. In addition to femoral head pressure measurements, serum cholesterol levels were followed serially and pathologic specimens from cortisone-treated femoral heads were obtained. Surgical decompression by a drilling method was performed and pressures were remeasured at four weeks following decompression. Persistent increases in cholesterol levels and in intrafemoral head pressures were noted, particularly from six to eight weeks after initiation of steroid treatment. Cholesterol levels were elevated to four times control values and femoral head pressures averaged 2 1/2 times the control values (60 cm of water vs 24.6 +/- 5.5 cm of water). Surgical decompression by drilling effectively reduced the once elevated pressures to control values. A relationship between increased fat cell size, increased intramedullary pressure and decreased femoral head blood flow in steroid-treated rabbits is postulated. The applicability of these data to humans with steroid-induced ischemic necrosis of the femoral head has yet to be demonstrated.