Do prior intra-articular injections impact on the risk of periprosthetic joint infection in patients undergoing total hip arthroplasty? A meta-analysis of the current evidences with a focus on the timing of injection before surgery.

Purpose: Intra-articular injection is a well-established and increasingly used treatment for the patient with mild-to-moderate hip osteoarthritis. The objectives of this literature review and meta-analysis are to evaluate the effect of prior intra-articular injections on the risk of periprosthetic joint infection (PJI) in patients undergoing total hip arthroplasty (THA) and to try to identify which is the minimum waiting time between hip injection and replacement in order to reduce the risk of infection. Methods: The database of PubMed, Embase, Google Scholar and Cochrane Library was systematically and independently searched, according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. To assess the potential risk of bias and the applicability of the evidence found in the primary studies to the review, the Newcastle-Ottawa scale (NOS) was used. The statistical analysis was performed by using the software 'R' version 4.2.2. Results: The pooling of data revealed an increased risk of PJI in the injection group that was statistically significative (P = 0.0427). In the attempt to identify a 'safe time interval' between the injection and the elective surgery, we conducted a further subgroup analysis: in the subgroup 0-3 months, we noted an increased risk of PJI after injection. Conclusions: Intra-articular injection is a procedure that may increase the risk of developing periprosthetic infection. This risk is higher if the injection is performed less than 3 months before hip replacement.