[The bipolar cup Avantage in hip revision surgery]

Luxations in revision arthroplasty are a serious complication with an incidence of up to 30 percent. In particular in patients with previous operation and resection of bone and soft tissue, the instability increases significantly. The use of the bipolar revision cup Avantage has to be proven valuable to avoid recurrent luxation.

27 consecutive revisions of the bipolar acetabular component were performed. The mean age at the time of revision was 67 years (range 40-91 years). The mean rate of previous operations was 5.1 cases (range 1-14). In 11 hips (40.7%) the acetabular cup was revised, in 16 hips (59.3%) an additional stem revision was performed. In 10 cases the revision was performed by a proximal femur reconstruction, in one patient by a total femur reconstruction. The follow-up was short-term, at a mean of 20 months (range 13-29 months). The clinical results were evaluated prospectively by the Harris hip score (HHS) and the activity score according to Sutherland (aSL). The migration of the cup and the change of the inclination angle were calculated radiographically.

There has been one dislocation of the polyethylene liner in the recent follow-up, which could be treated conservatively by closed reduction. No patients required reoperation because of technical errors or loosening of the bipolar acetabular implant. The HHS improved from a mean of 40.5 (range 7-77.4) to 66.8 points (range 17.4-89.9). The modified Sutherland score improved to 5.9 (range 3-9) of 10 possible points. Radiographic follow-up revealed neither evidence of component loosening nor migration or polyethylene wear.

Use of this bipolar unconstrained component was successful in restoring stability in hip revision arthroplasty, e.g., in patients with severely unstable hips. It has to be observed carefully if there are any disadvantages of these devices because of higher polyethylene wear in the mid- or long-term follow-up. The possible disadvantages of dissociations between the inner liner from the outer liner or damage of the polyethylene liner limits the indication of this device to serious revision cases.