High medium-term survivorship and durability of Zweymüller-Plus total hip arthroplasty

Abstract

Background and purpose: The Zweymüller-Plus system (SL-Plus stem, Bicon-Plus threaded cup) for primary total hip arthroplasty (THA) was introduced in 1993, as a successor of the Alloclassic THA with a few modifications in the conical stem shape and a new biconical threaded cup with a spherical shape. The medium-term performance of this system is not well established. To better understand the potential impact these design changes have had on (1) survivorship, (2) implant stability and (3) periprosthetic osteolysis, we studied patients who underwent THA using the SL-Plus stem and Bicon-Plus.

Methods: We retrospectively reviewed the cases of 148 patients (153 hips) who underwent Zweymüller-Plus primary THA after an average of 11 years.

Results: With revision for aseptic failure of biological fixation as the endpoint, survivorship was 98% for the stem and 100% for the cup. Focal osteolysis was observed in 6.6% of cups and 29% of stems. Four hips (2.6%) were revised because of aseptic failure of the biologic fixation and three hips (1.95%) for deep infection. As much as 146 stems and 149 cups were evaluated to be stable.

Conclusion: Zweymüller-Plus THA resulted in high survivorship and durability at 11 years, although the rate of osteolysis around the stem indicated polyethylene wear.