The fully hydroxyapatite-coated short-tapered stem demonstrates a more silent femoral bone reaction than the Tri-Lock bone-preserving stem in total hip arthroplasty

Purpose The aim of this study was to compare the midterm clinical and radiographic outcomes of total hip arthroplasty (THA) using the Tri-Lock Bone Preservation Stem (BPS) and the ACTIS fully hydroxyapatite (HA)-coated short-tapered stem. Methods A retrospective cohort of 155 consecutive THA patients (76 Tri-Lock BPS, 79 ACTIS stem) was analyzed. After 1:1 propensity score matching, 140 patients (70 pairs) with comparable demographic data were evaluated. The minimum clinical and radiographic follow-up period was 5 years (mean 5.6 years). Harris Hip Scores (HHSs) were compared between groups. Radiographic assessments included stress shielding, spot welds, and cortical hypertrophy according to Gruen zones and Dorr classification. Results No significant differences in pre- or post-operative HHSs were observed between groups. The Tri-Lock BPS group showed significantly more second-grade stress shielding and a higher overall incidence. In Dorr type B cases, Tri-Lock BPS demonstrated more second-grade and total stress shielding. Spot welds in Gruen zones 2 and 6 were more frequent in Tri-Lock BPS, whereas those in zones 4 and 5 were more frequent in ACTIS stem. Cortical hypertrophy in Gruen zone 3 and the total number of lesions were also higher in Tri-Lock BPS. Conclusions The ACTIS fully HA-coated short-tapered stem yielded clinical outcomes comparable with those of the Tri-Lock BPS while demonstrating fewer adverse femoral bone reactions, including stress shielding and cortical hypertrophy.