• B A Ishaque, S Wienbeck, E Basad, and H Stürz.
• Klinik für Orthopädie und Orthopädische Chirurgie der Justus-Liebig-Universität Giessen. BAISHAQUE@AOL.COM
• Z Orthop Ihre Grenzgeb. 2004 Jan 1; 142 (1): 15-24.

AimThe various radiological changes after implantation of the thrust plate prosthesis (TPP) are demonstrated and, with the help of a standardized radiological classification, divided in pathological and non-pathological findings.MethodThe radiological follow-ups of 167 TPP implanted between 1993 and 1998 was analyzed in this study. The follow-up examination was carried out postoperatively, after 6 months and subsequently every year. The radiological assessment was carried out in an exact a.p. view. We subdivided the images into four sectors: A corresponds to the femoral neck stump, B to the bony stock cranial (=1) and caudal (=2) to the mandrel of the prosthesis, C is the region above and under the bolt and D the cortical area around the lateral plate.ResultsRadiolucencies were especially seen in sector A (A 1 = 34.7 %; A 2 = 18%) and sector C (44 %). As a pathological finding, we saw progressive radiolucencies of sector B (6 %), which were interpreted to be a sign of loosening, when they showed a thickness of = 2 mm. Furthermore, in some cases we observed extended atrophy under the lateral plate, which was also judged to be a sign of loosening.ConclusionThe radiological changes of the bony stock of the TPP can be divided into physiological adaptation processes because of changed biomechanics and signs of loosening. As a stress-shielding phenomenon we see a progressive atrophy under the thrust plate and simultaneously a sclerosis of the spongious bone above the calcar femoris. An indication for a loosening of the prosthesis is a progressive radiolucency of sector B.

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