Migration Pattern of a Short Femoral Neck Preserving Stem

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°, 0.3), but stabilized before 1 year. Subsidence (0.05 mm, 0.06) and varus-valgus tilting (0.03°, 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.