[The Zweymuller endoprosthesis in hip joint revision surgery]

The aim of the study is the verification of the applicability of the Zweymüller system of total hip replacement in dependence on the size of defects of acetabulum and femur and evaluation of early results in patients operated on in 1998 and 1999.

In 1998 and 1999 we reimplanted 125 total hip replacements. In 60 revision surgeries we used at least one component of Zweymüller Bicon Plus system. We prospectively followed defects of acetabulum and femur in DGOT classification. The size of the stem was planned, final indication of the cup was determined peroperatively.

During the implantation of the cup we tried to achieve primary stability of the implant. The cup was implanted in uni- and bisegmental defects. In total we implanted 50 Bicon cups, in 24 hip joints we applied morselized allograft in the defect. In tri-segmental defects we used twice the Burch Schneider cage and in 4 hip joints a bone allo-graft with a cemented cup in combination with SL-Plus stem. In one female patients after the implantation of Bicon cup in type 7 defect there occurred an early failure. When removing bone cement we preferred fenestration of the cortical bone of the femoral shaft. In 30 hips SL-Plus stem was used and in 13 hip joints SLR-Plus was applied. We checked 50 hip joints operated on by the method after Harris and by radiographs in two projections.

Fifteen patients are without pain, 14 patients take analgesics. The final result is excellent in 24% of patients, good result in 32%, satisfactory in 24% and poor in 20% of patients followed up. By comparison with HHS value prior to the surgery HHS got worse in two patients who are not satisfied with the result of the operation. Average score prior to surgery was 47.4 points (range, 23-82.6). Five times we encountered a radioluscent line of acetabular component in zone III. Radiograph signs of loosening of the cup or stem were not found in any of the hip joints.

Zweymüller system is applicable in revision surgeries of both cemented and cementless hip joint replacements. The cup may be applied in uni-segmental and bi-segmental acetabular defects under the condition of achievement of primary stability. Applied morselized bone allografts have a good potential for osteointegration and remodeling. The rectangular stem is suitable for the treatment of defects extending as far as 5 cm below the level of lesser trochanter. Bone cement was extracted from fenestration, transfemoral approach was not required in any of the patients. Even with the use of SLR (revision) stem we did not transfer fixation of the femoral component to the lower half of femur.