Die sphärische Pressfit-Pfanne Plasmacup als Revisionsimplantat beim Hüftendoprothesenwechsel. Mittelfristige klinische und radiologische Ergebnisse.

Background: A cementless component is currently used in most acetabular revisions. The present study gives the first report about the application of the Plasmacup from Aesculap, which is a hemispherical porous socket as a revision component. Methods: 72 cementless cup revisions were performed in the Frankenberg district hospital between 1st January 1996 and 31st December using one of three types of Plasmacup, each having identical main features Type P was used in 33 cases (46%), type S in 17 cases (24%) and type SC in 22 cases (30%). The mean follow up period was 7 years (range 0.5 – 12.5 years). The mean age of the patients at the index operation was 65.4 years. The pre-operative X-rays were used for grading the bone defects according to the Paprosky score. There were 9 Paprosky type 1, 40 type 2, 10 type 3a and 1 type 3b defects. Autografts were used in 20%, allografts in 10% and xenografts in 1% of the revisions. The fate of 68 cups (94%) could be followed up. 44 (41%) patients could be examined in person, 10 (14%) were interviewed by telephone by the means of a standardised questionnaire, 14 patients (19%) died, and therefore the relatives or the GP were interviewed. 336 X-rays were evaluable (74 of the hip and 262 of the pelvis) and analysed in respect of osseointegration of the cups and osteolysis according to the DeLee zones. Cup migration was checked with the help of the computer-program Wristing, with the teardrop as main reference point. For the clinical evaluation the Harris Hip Score and the WOMAC score were used. Results: At the final examination the mean Harris Hip Score was 88.5 points and the mean WOMAC score 18.5 points. 93% of the personally examined patients expressed their satisfaction with the result of the operation. During the follow up period no aseptic loosening could be observed and only one cup had to be removed due to infection. Regarding the acetabular implants as an entirety, no significant migration could be observed in the longitudinal and the transversal direction. The inclination showed a significant alteration of 3.5° (p < 0,001). There was no progressive radiolucency in the aseptic cases and the postoperative radiolucency which occured in 24% of the cups decreased. Neither the application of screws (done in 90% of type S and SC) nor grafting influenced the outcome. Conclusion: The Plasmacup is suitable for cementless cup revision. It achieves results comparable to cups from other manufacturers which have been well examined and described in the literature. A solid osseointegration can even be expected in the event of major bone loss.