Straight stem and threaded cup total hip arthroplasty systems in patients under 60 years of age: outdated or still a benchmark? A report on a cohort of 75 patients after 28.8-30.2 years of follow-up

Abstract

Purpose: The goal of this retrospective observational study of one cohort was to evaluate the long-term outcome in patients younger than 60 years after total hip arthroplasty using a straight uncemented stem and an uncemented threaded cup. Methods: Between 1986 and 1987, 75 hips of 75 patients (mean age: 53.35±6.17 years) were consecutively implanted with an Alloclassic Zweymüller/Alloclassic SL stem and an Alloclassic CSF cup. 44 patients had died over the last 30 years. The remaining 31 patients (mean age: 82.9±6.4years) were reinvited for follow-up examinations. Clinical and radiographic evaluations were carried out. Results: At a mean follow-up of 29.5 (28.8-30.2), 4 patients (5.3%) were lost to follow up. For the endpoint aseptic loosening (defined as the removal of stem or the cup for 2 cases), the overall survival rate is 97.3%. For the endpoint revision for any reason (22 patients), the survival rate is 70.6%. Eleven patients needed an exchange of head and liner due to wear. The mean time from implantation until change of head and liner was 21.44 years (SD 5.92). Other reasons for revisons were septic loosenings (3 cases), aseptic loosening of stem and cup (1 case), aseptic loosening of stem (1 case), periprosthetic calcification (2 cases), implant fracture (1 case), periprosthetic fracture (1 case), intraoperative fissure of stem (1 case), total wear of liner including cup (1 case). Conclusion: The combination of a straight stem (Alloclassic) and a screw cup (CSF) shows excellent results in young patients under the age of 60 at ultra-longterm follow up at 30 years. Revisions due to wear of the polyethylene liner are more likely than in the older patients.