The Migration Pattern of a Short-Tapered Femoral Stem Correlates with the Occurrence of Cortical Hypertrophies: A 10-Year Longitudinal Study Using Ein Bild Röntgen Analyse-Femoral Component Analysis.

Abstract

Background: Shorter hip stems have shown promising mid-term results but lack long-term data. High rates of distal cortical hypertrophy (CH) have been described, suggesting a more diaphyseal load transmission. This study aimed to determine patient-specific and surgery-related factors influencing CH and their impact on 10-year outcomes. Methods: It included 100 consecutive total hip arthroplasties (THAs) using the Fitmore stem (Zimmer, Warsaw, Indiana), with clinical and radiographic follow-ups at 1, 2, 5, and at least 10 years post-surgery. Results: No revisions were performed due to aseptic loosening after a mean of 11.6 years (range: 10-13.5 years). CH was observed in 26% of hips, primarily in Gruen zones 3 and 5. There was no significant difference in the Harris Hip Score between patients with and without CH. Larger stem sizes and greater axial subsidence significantly correlated with CH occurrence (OD 1.80, (1.13-1.92), p = 0.004; OD 1.47, (1.04-2.08), p = 0.028). The Fitmore stem demonstrated excellent survival rates and favorable outcomes over 10 years. Conclusions: Despite a lower CH rate compared to other studies, significant correlations with stem size and subsidence were identified. This study underscores the importance of patient selection and achieving high primary stability to maintain the metaphyseal anchoring concept.