Faveere, Arnout, Milne, Lachlan P., Holder, Carl, and McDougall, Catherine (2025) Comparison of Rates of Aseptic Loosening in High versus Standard Offset Cementless Femoral Stems: An Australian National Joint Registry Cohort Analysis. Journal of Arthroplasty, 40 (12). pp. 3207-3214.

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Abstract

Background: Restoring femoral offset in total hip arthroplasty (THA) has several benefits including improved hip abductor strength and enhanced range of motion. Biomechanical studies have suggested that increased femoral offset may negatively impact initial stem stability. However, it is unclear whether this has a clinical impact. Using data from the Australian Orthopaedic Association National Joint Replacement Registry, the aim of this study was to determine the impact of stem offset and stem size for three frequently used cementless wedge taper THA prostheses revised for aseptic loosening. Methods: The study period was September 1999 to December 2022. The study population included all primary procedures for osteoarthritis with a cementless THA using three different stem systems (A, B, and C). Procedures were divided into small and large stem sizes, and by standard and high stem offsets for each stem system. Hazard ratios (HRs) from Cox proportional hazards models, adjusted for age and sex, were performed to compare revision for aseptic loosening for offset and stem size for each of the three femoral stems. Results: There were 62,358, 15,384, and 17,527 stems from stem A, B, and C, respectively, included in this study. There was a significant increase in revision for aseptic loosening with high offset, small size stem A (HR 1.84; 95% confidence interval 1.50 to 2.24; P < 0.001) and stem B stems (HR = 1.76 (95% confidence interval 1.22 to 2.53); P = 0.002). For stem C, there was a higher rate of revision for high offset, small size compared to large size stems only. There was no significant difference seen between standard and high femora offset stems in the large sizes for any of the stem designs. Conclusions: High offset is associated with increased revision for aseptic loosening, but this is both stem size and prosthesis specific. Highly porous stem surface treatments may be protective against aseptic loosening, and alternative stem designs should be considered when femoral anatomy dictates the use of a small sized, high-offset hydroxyapatite-coated wedge taper cementless femoral stem.

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