[Recommendations for standardized radiologic follow-up of thrust plate endoprosthesis]

The thrust-plate endoprosthesis (TPE) is a cementless, total endoprosthetic replacement of the coxal femur with metaphysical anchorage. A combination of the TPE with an endoprosthetic cup component, which is also cementless, is recommended based on the concept of the TPE. The TPE requires a special radiological technique. In radiological follow-up examinations, the positioning area of the TPE, particularly on the resected femoral neck, is especially important. A gap-free, level positioning of the implant on the resected and flat-ground femoral neck is ideal. In order to be able to exactly judge the positioning area, the bony area and the TPE that lies on it should have no overlap in the anterio-posterior optical path of the X-ray and must be hit exactly orthogonally by the central X-ray beam. As radiological examinations of human femoral preparations show, this succeeds best with an inner rotation positioning of the femur from 10 to 20 degrees. According to our experience, especially in freshly operated patients, the positioning of the legs with the femur in a slightly abducted position (about 10-20 degrees) is better tolerated. Only when the positioning of the TPE cannot be exactly judged with the above-mentioned examination method should the examiner use an X-ray image intensifier. Experience has shown that this is only necessary in exceptional cases. In the present examination, the special problems of radiological examination of the TPE are discussed. Recommendations for standardized radiological examinations, as well as findings following TPE implantation, are given.