Relative Head Size Increase Using an Anatomic Dual Mobility Hip Prosthesis Compared to Traditional Hip Arthroplasty: Impact on Hip Stability

Smaller head sizes and head/cup ratios make cups smaller than 50 mm and larger than 58 mm, more prone to dislocation. Using computer modeling, we compared average head sizes and posterior horizontal dislocation distance (PHDD) in two 78-patient matched cohorts. Cup sizes were small (≤50 mm) or large (≥58 mm). The control cohort had conventional fixed bearing prostheses, while the experimental cohort had anatomical dual mobility (ADM) hip prostheses. ADM cups have larger average head sizes and PHDD than traditional fixed bearing prostheses by 11.5 mm and 80% for cups ≤50 mm, and 16.3 mm and 90% for cups ≥58 mm. Larger head sizes and increased head/cup ratio may allow the ADM prosthesis to reduce the incidence of dislocation.