The theme of this work is the application of the engmeermg theory of frictional torque to total hip replacement. The author adhered tenaciously to this theory, involving the use of a small-diameter femoral head, throughout the epoch when the large-diame ter, metal-to-metal design dominated the field. During that considerable period general satisfaction with the early results rendered criticisms of the large-diameter head unwelcome. There was a formidable array of counter criticism: the small head would pierce a film of synovial fluid; the small head would wear the socket too rapidly; the...