Avascular necrosis of the proximal end of the dens. A complication of halo-pelvic distraction.

Roentgenographic evidence of avascular necrosis of the upper part of the dens was observed in thirteen of ninety-four patients treated for tuberculous kyphosis or non-tuberculous scoliosis using halo-pelvic distraction. Four patients had some residual loss of motion. A significant relationship was demonstrated between avascular necrosis and the amount of distraction visible on roentgenograms.