Journal of Joint Surgery and Research · Published 2025-09-23 · DOI 10.1016/j.jjoisr.2025.09.001
Purpose: The Promontory stem, a newly developed Zweymüller cementless femoral stem with a proximal fixation-enhancing fin, was introduced in Japan in 2022. This study aimed to evaluate its early clinical and radiological outcomes. Methods: This retrospective cohort study included 56 patients who underwent primary total hip arthroplasty using the Promontory stem between August 2022 and October 2023. Clinical scores (JOA, EQ-VAS, HOOS-JR, FJS-12) and radiographic findings (stem alignment, stress shielding, radiolucent lines, cortical hypertrophy) were assessed at a mean follow-up of 22.8 months. Multivariate logistic regression was used to identify predictors of stress shielding around the stem. Results: The mean patient age was 66.0 years and 71.4% were female. JOA scores improved significantly from pre-to post-operative time points in all domains; the total score increased from 42.9 to 82.3 at 2 years (p < 0.001). Mean EQ-VAS, HOOS-JR, and FJS-12 scores at final follow-up averaged 77.3 ± 17.6, 79.8 ± 15.7, and 63.5 ± 25.6, respectively. Radiologically, stress shielding was observed in 66.1%, with 17.9% having grade 2 or higher. Radiolucent lines were noted in 69.6% and cortical hypertrophy in 17.9%. No cases of aseptic loosening occurred. Complications included stem subsidence (3.6%), dislocation (3.6%), and periprosthetic fracture (1.8%). The 2 year implant survival rate was 98.2%. Multivariate logistic regression identified older age, female sex, and pre-operative lower bone mineral density of femoral neck as predictors of stress shielding. Conclusions: The Promontory stem showed favorable early outcomes with no major complications and high survivorship, despite frequent stress shielding and proximal radiolucent lines.
Abstract from DOAJ. Public domain (CC0 1.0).
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