Shaft fissures due to implantation of cementless total endoprostheses of the hip joint. An experimental study.

Since 1982, at the Orthopedic Department of the Pulmologic Center of the City of Vienna we have used the Zweymüller shaft system and the pyramidal threaded socket by Schwägerl when implanting cementless hip endoprostheses. Some patients repeatedly complained about pains in the shaft region within the first postoperative months, though these complaints could not be explained clinically or radiographically. On 15 human cadavers we implanted a total of 20 Zweymüller shafts and examined the femurs for ruptures of the shaft. Our special interest was the course of the fracture lines, their localization, and their display on roentgenograms. It appeared that fissures of the shaft are easily caused by the forced driving-in of the prosthesis. In about half of all cases the fissure cannot be seen on roentgenograms because of the site is covered by the implant itself. The fracture lines do not always begin intertrochanterally or from the calcar femoris; therefore, they cannot be recognized during surgery. This problem should be considered during implantation as well as during postoperative remobilization.