and refinement that exists within the necessarily strict rules of the internal fixation method. In this way we seek to contribute to as weIl as to stimulate the search for rational solutions to surgical problems. It is assumed throughout that the reader is fa miliar with the technical fundamentals of internal fixation, and so these details are omitted. Instead, special indications and technical refinements are presented on the basis of case examples. Because an endless variety of situations can arise in orthopedic surgery (a circumstance that is attracting more and more surgeons to the field), we have taken ca re that our examples can readily be applied to novel situations. We now credit, in alphabetic order, those who contributed most to the techniques presented: R. BLATTER, A. BOITZY, C. BRUNNER, O. CECH, A. DEBRUNNER, F. MAGERL, G. SEGMÜLLER, G. STÜHMER, and B.G. WEBER. We thus express thanks to those colleagues in our clinic who agreed to having their ideas published. But we are also grateful to our illustrators, H. and K. SCHUMACHER, our photographer, M. SCHAFFNER, and our chief secretary, U. OETLIKER, who contributed so much to the preparation of the manuscript. Finally, we thank Springer-Verlag for their patience with us and especiaUy for their efficient work in bringing the book to press. St. GaU, Fall 1981 CH.F. BRUNNER B.G. WEBER Contents Lag Screws ............. .