POSITIVE pressure causes bone fragments not only to be immobilized and held in contact but to be compressed together. This appears to result in union of cancellous bone in a shorter time than if the fragments were only approximated. The term "positive pressure" was used by one of us (Key1) in 1932, when such a method was described after its use postoperatively in arthrodesis of the knee. We continue to use and to advocate the method in arthrodesis of the knee joint but have not been able to satisfy our curiosity as to whether it is the contact, the more perfect immobilization, or the pressure of one fragment upon the other, or all three, which exert a favorable influence upon union.
Charnley * has used and described positive pressure as an adjunct in arthrodesis not only of the knee joint, but of the ankle, shoulder, hip, and interphalangeal joints. In