Revision rates of one new and two established hemiarthroplasty heads: a comparative cohort study from the Swedish Arthroplasty Register.

Abstract

The anatomical Lubinus SPII-stem is commonly used in hemi-arthroplasty for femoral neck fractures (FNF), combined with either the bipolar Variocup, the Unipolar Head (UH) and a newly introduced unipolar Modular Trauma Head (MTH). Similar constructs like the MTH are reported to have risk of corrosion and wear. This is the first publication evaluating the MTH. To describe the revision rate of the SPII-stems/heads which were divided into 3 groups (Variocup, UH, MTH). The head types are compared by their rate of revision at 2 years, due to any cause and to dislocation. Revision and mortality rates up to 10 years are reported. This observational cohort study based on prospectively registered data from the Swedish Arthroplasty Register included 33,059 patients with hemiarthroplasty 2005-2021 due to FNF. SPII-stems combined with Variocup (<i>n =</i> 7,281), UH (<i>n =</i> 23,980), MTH (<i>n =</i> 1,798) were included. The follow-up ended at 10 years for Variocup and UH, for MTH at 2 years. Kaplan-Meier survival analyses was used, with a 95% confidence interval (CI). Patients were censored at death or at the end of the study (31 December 2021). The 2-year revision rate regardless of cause was similar between the groups: after Variocup 3.5% (CI, 3.1-4.0), UH 3.1% (CI, 2.9-3.4), MTH 3.5% (CI, 2.6-4.5).At 10 years, the Variocup and UH had similar revision rates; 4.6% (CI, 4.0-5.2) and 5.0% (CI, 4.4-5.6).For revision due to dislocation at 2 years Variocup 2.3% (CI, 1.9-2.7) had an inferior outcome compared to UH 1.5% (CI, 1.3-1.7). The MTH had an intermediate outcome, 1.7% (CI, 1.0-2.3). Variocup had a higher dislocation related revision rate, until the 10th year.The 2-year-mortality was 36% (CI, 35-37) after Variocup, 43% (CI, 42-43) after UH and 44% (CI, 41-47) after MTH. The hemi-heads have comparable revision rates within 2 and 10 years. The new MTH performs similar to the standard UH. The bipolar Variocup is associated with more revisions due to dislocation.