[Periarticular ossifications following implantation of cement-free total hip endoprostheses of the Zweymüller-Endler type]. 
Ectopic ossifications after 158 cementless implanted Total hip endoprostheses Type Zweymüller-Endler have been examined postoperatively within 12 months at the earliest.  The rate of ossification was 39.9%.  This range is higher than the mean range of cemented hip endoprostheses reported in the literature.  The higher range of ossification is found in low grade ossification grade CA I. Severe ossification of grade CA III occurred only in a low percentage.  The influence of various factors (as prophylaxis for thrombosis approach, duration of operation, sex, age, other diseases, complications) on the frequency of occurrence is examined.  There was no significant result concerning these parameters.  The main causes for ectopic ossification seem therefore to be dispositional and constitutional factors.  Male patients under the age of fifty show ectopic ossification in the highest degree.