The prognosis of total hip replacement in patients younger than 55 years of age. Results of 28,480 primary replacements from the Nordic Arthroplasty Register Association

Introduction The aim of this study was to evaluate the patient and surgery related risk factors for revision following primary THR in patients younger than 55 years of age using the large population-based NARA dataset. Materials and methods Through the Nordic Arthroplasty Register Association (NARA) dataset we identified all primary THRs due to osteoarthritis in patients younger than 55 years of age performed in four Nordic countries from 1995–2011 ( n  = 28,480). We estimated overall risk for revision due to any reason, due to aseptic loosening, and risk for any revision within 2 years. We used Cox regression analyses to calculated crude and adjusted Hazard ratio as a relative risk (RR) and 95% confidence interval (CI) in order to study patient and surgery related risk factors for revision. Results Overall revision risk following primary THR due to any cause was 7.9% (2240 out of 28,480 primary THR), whereas the revision risk due to aseptic loosening was 4.2% (1192 out of 28,480 primary THR). No difference in any revision risk regarding sex and age was evident, but female had lower risk of revision due to aseptic loosening (RR = 0.86, 95% CI: 0.76–0.76). Uncemented implant had reduced risk for overall revision due to aseptic loosening (RR = 0.52, 95% CI: 0.45–0.59), whereas hybrid implants had higher risk for overall any revision compared with cemented technique (RR = 1.28, 95% CI: 1.13–1.45). However, overall differences were only observed during the period 1997-2003. Sex and age subgroup analyses reviled, that uncemented implants also had higher risk of any revision among females older than 45 years, whereas hybrid implants had particularly high risk for any revision among males older than 45 years. Conclusion Our large population-based study provides evidence that age, sex and calendar year of surgery were not risk factors for either overall any revision or revision due to aseptic loosening. In general, hybrid implant had higher risk for any revision, whereas uncemented implant had lower risk of revision due to aseptic loosening. However, the risk estimates for fixation technique were dependent on calendar year of surgery, as well as on age and gender.