Periprosthetic strain-adaptive bone remodeling of conservative metaphyseal fitting versus conventional anatomic cementless femoral stem.

BACKGROUND: This study aimed to compare: (1) periprosthetic bone mass changes; (2) clinical results; (3) revision rates; and (4) survivorship of total hip arthroplasty (THA) in patients younger than 50 years. METHODS: This was a retrospective study in which 168 patients with conservative metaphyseal-fitting anatomic cementless (CMA) stems (201 hips) were identified, and then a separate group of 181 patients with conventional anatomic cementless (CA) stems (209 hips) were identified. Periprosthetic bone mass change was measured using DEXA. The mean follow-up was 20-22 years (range 20-24 years) in both groups. RESULTS: In the CA group, BMD decreased markedly in both Gruen zones 1 and 7 of the femur. Harris Hip Score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, and University of California, Los Angeles (UCLA) activity score improved significantly at the final follow-up in both groups. The survival rate was 97.5% (95% CI, 91-100%) in the CMA stem group and 97.1% (95% CI, 91-100%) in the CA group at 20 years of follow-up. CONCLUSIONS: At a mean follow-up of 20-22 years, both CMA and CA stems provided excellent clinical results. However, CA stems had significantly higher stress-shielding-related bone loss.