Discontinuing the recommendation of hip precautions does not increase the risk of early dislocation after primary total hip arthroplasty using 36-mm heads: a population-based study from the Danish Hip Arthroplasty Register

Background and purpose — Dislocation is a severe complication following total hip arthroplasty (THA). Hip precautions have been recommended in the initial postoperative period but evidence supporting this practice is limited. We therefore conducted a population-based study to evaluate the association between discontinuing recommending postoperative hip precautions and the risk of early dislocation. Methods — This is a cohort study with data from the Danish Hip Arthroplasty Register and the Danish National Patient Register. We included patients who underwent primary THA for osteoarthritis in 2004–2019 in public hospitals in the Capital Region of Denmark. The cohort was divided into the hip precautions group, comprising patients operated on between 2004 and 2009, and the no-precautions group operated on between 2014 and 2019. The primary outcome was the difference in the absolute risk of dislocation within 3 months post-surgery. The secondary outcome assessed the same risk within 2 years. We evaluated the difference in absolute risk using absolute risk regression (ARR). Results — The cumulative incidence of dislocation within 3 months was 2.9% (confidence interval [CI] 2.5–3.3) in the hip precautions group and 3.5% (CI 3.1–3.9) in the noprecautions group. The risk of dislocation was higher in the no-precautions group but failed to reach statistical significance in the crude (ARR 1.2, CI 0.9–1.6) and multivariate model (ARR 1.4, CI 0.9–2.2). Conclusion — We found a higher but statistically insignificant increase in the risk of early dislocation in the noprecautions group. The lack of significance in the association may be explained by the increased use of 36-mm femoral heads after the guideline revision.