[Principles of fixation of the cementless modular revision stem Revitan].

AIM AND METHOD

To analyse the femoral fixation of a modular cementless revision endoprosthesis, eight prosthetic combinations of the Revitan-System (Centerpulse, Winterthur, Switzerland) were implanted in four cadavers. On three cadavers a curved revision Revitan stem was implanted by an endofemoral approach on one side and by a transfemoral approach on the contralateral side. On the fourth cadaver a straight Revitan stem was implanted on one side and a curved Revitan stem on the contralateral side using a transfemoral approach. Transversal slides of 7-8 mm thickness were performed at the fixation areas of each implant and the implant-bone contact was analysed macroscopically and using contact radiography.

RESULTS

The straight stem implanted by a transfemoral approach showed a double-conical press-fit fixation with cutting of the eight longitudinal fins into the cortical bone. The curved revision stems implanted by the same approach had a circular surface fixation similar to the press-fit fixation of the straight stem. In contrast, the curved stems implanted by the endofemoral approach (without a window) showed a three-surface fixation. Hereby the two distal fixation areas led to the primary implant stability by three of the four double edges of the octagonal cross-sectional area cutting into the cortical bone. At the proximal fixation zone the implant only had contact of two implant double edges to the cortical bone.

CONCLUSION

Different approaches for implantation lead to different fixation techniques of a curved revision stem. This should be considered by analysing postoperative sintering rates of cementless revision stems.