[The dangerous blood clot in orthopaedic surgery (author's transl)].

104 patients who had been subjected to an orthopaedic procedure such as total hip prosthesis, knee prosthesis, or upper femoral osteotomy, have been studied by pre- and post-operative phlebographs. Calcium heparinate was given systematically after operation. It was noted that despite this regime, half of the patients showed thrombosis. The "dangerous" clot was situated in a main venous trunk and was unattached. Out of 79, 40 clots were said "dangerous". Four emboli were observed, of which one was fatal. Total hip prostheses were less dangerous than knee prostheses or osteotomies. A popliteal clot was more dangerous if traction was used post-operatively, and if the dose of heparin was only a preventive dose. Curative doses limited the extent of clots formed and decreased the likelihood of migration provided medication was started early. Pre-operative injection of heparin 2 hours before operation did not decrease the number of clots. Some other risks were also analysed. It was noted that early re-operation was accompanied by a very high risk. In such cases, preventive occlusion of the inferior vena cava may be justified.