Minimum ten-year results of total hip arthroplasty using an alkali- and heat-treated titanium Zweymüller-type stem

The Zweymüller femoral stem is a well-established design for cementless total hip arthroplasty (THA). However, long-term data are scarce on modified versions produced by different manufacturers. This study aimed to evaluate the ten year clinical and radiographic outcomes of the Elance stem, a modified Zweymüller-type prosthesis.

We retrospectively reviewed 82 primary THAs performed between 2013 and 2015 using the Elance stem. This stem features an alkali- and heat-treated bioactive surface and lacks the traditional trochanteric shoulder. The target roughness of the stem surface was 1.0 to 2.5 µm. The primary endpoint was survivorship with revision for any reason; the secondary endpoint was the rate of the aseptic loosening of the Elance stem.

The 10-year survivorship rate with revision for any reason was 53% (95% CI: 40-63%). Forty-one hips (50%) underwent revision surgery, with 40 of these revisions (98%) due to aseptic stem loosening. Additionally, four stems demonstrated radiographic loosening but had not yet undergone revision, resulting in a total stem loosening rate of 54%.

The Elance femoral stem demonstrated unacceptably low year survivorship. Design modifications, specifically the omission of the trochanteric shoulder and a lower surface roughness compared to the original Zweymüller design, likely compromised initial stability and long-term osseointegration. These findings emphasize that bioactive surface treatments cannot compensate for suboptimal stem design and that caution is warranted when adopting modified orthopaedic implants without robust long-term evidence.