Similar functional outcomes but different remodeling patterns: A minimum 5-years radiographic comparison of short fit-and-fill stem and quadrangular taper stem

Purpose: ACTIS and CORAIL are cementless titanium femoral stems with hydroxyapatite (HA) coating but differing macro-geometries: ACTIS features a variable triple-taper with a medial collar, whereas CORAIL is a straight double-tapered design available with or without a collar. We compared mid-term clinical and radiographic outcomes of these stems with a minimum 5-years follow-up.
Methods: We retrospectively reviewed 114 primary total hip arthroplasties using ACTIS (63 hips) or CORAIL (51 hips). Clinical outcomes and standardized radiographic parameters were assessed and compared between groups.
Results: The canal-fill ratio (CFR) was significantly greater at the proximal, middle, and distal levels in the ACTIS group. Spot-weld formation was more frequent with ACTIS than with CORAIL (58.7% vs 35.3%). In logistic regression, proximal CFR significantly predicted spot-weld formation for ACTIS, with an optimal cutoff of 66.2% (sensitivity 91.9%, specificity 72.0%). Rates of subsidence, radiolucent lines, and pedestal formation did not differ significantly between groups. No severe stress shielding was observed with ACTIS, whereas three CORAIL hips demonstrated severe stress shielding (0% vs 5.9%). Clinical scores improved significantly in both groups, with no significant between-group differences at final follow-up.
Conclusions: Both stems yielded favorable radiographic and clinical mid-term outcomes. In ACTIS, greater proximal canal fill was associated with radiographic osseointegration, suggesting proximal CFR as a probabilistic radiographic marker of stem ingrowth.