[Clinical and radiological results with the spherical Mecring as acetabulum prosthesis in hip joint diseases]

The recent experiences which the university hospital in Heidelberg has made with the spherical Mecring must be valued positively. Clinical, radiological and subjective dates from 147 patients were worked up retrospectively. Indeed, the positive results must be considered as relative because of the short respectively medium-term period of control. Nevertheless, the repeated improvement in the second group after a period of postexamination on a average of 3.05 years lets hope for positive long-term results. In the period between 1985 and 1990 three sockets had to be changed. The reasons that the sockets loosened were not specific for the screwing but depending on the individual patients or on the implantations and technical circumstances. The negative results achieved by Engh et al. 1990 could not be recognized (8). He measured a radiological instability of 18% and a technical instability of 28%. What Engh did was measuring simple review photographs and extracting valuable material from them while using geometrical methods. This method shows various measuring mistakes. Therefore Engh's conclusion that the screwing should not be used for implantation because of its displacement in the bones is doubtful. The doubts seem to be supported by the results of our comparison of two series of X-ray photographs with defined different pelvis positions of the same patient. The screwing seemed to be significantly displaced in cranio-medial direction. This was proved by experimental photographs with a pelvis raised to 6 cm in contralateral direction. But the results were a matter of radiological illusion. Radiological migration of the screwing is only provable by complicated X-ray analyses steered with the computer. These big X-ray series are not accessible at the time.