The CFP stem represents a short collared neck-retaining stem with very proximal metaphyseal anchoring along the calcar combined with up-to-date metallurgy. Despite theoretical advantages, the stability and clinical outcome are unknown. We prospectively measured the migration pattern of this new stem and cup. Twenty-six patients (26 hips) with a mean age of 54 years (range, 40-66 years) underwent THA and were followed for 2 years with radiostereometry, radiographs, and clinical scores. The stem showed some early retroversion (mean, SEM 0.6 degrees, 0.3), but stabilized before 1 year. Subsidence (0.05 mm, 0.06) and varus-valgus tilting (0.03 degrees, 0.01) were low. We observed no bone loss in the calcar region. Factors related to patients, implant design, and implantation did not predict migration patterns. The two-dimensional wear of the ceramic/conventional articulation was 0.09 mm at 2-24 months. The low migration of this short neck preserving stem suggests a favorable long-term outcome but longer followup is needed to substantiate this prediction. This design might become an alternative to standard stems and hip resurfacing.
Level of evidence: Therapeutic Level IV. See The Guidelines for Authors for a complete description of levels of evidence.