This study was unable to draw any correlation between the preoperative administration of intra-articular corticosteroid injections and an increased rate of postoperative complications of TKA, including PJI. The findings of this study mirror those of two 2014 meta-analyses that also reported no increased risk of postoperative PJI after preoperative corticosteroid injections. However, due to the underpowered and heterogeneous nature of many prior studies, both of these publications cited the need for increased larger-sized studies on the matter[14,15]. Since that time, additional studies seem to display dichotomy between relatively smaller, single center studies[16,17], such as this one, and larger database studies[9,11].
Works by Amin et al. found no significant difference in the infection rates of 783 patients who received an injection and 845 who did not. In a similar manner, Kokubun et al. found no significant difference in complication rates, infection rates, and short-term functional outcomes of 175 patients who received four or more preoperative injections and 267 who received three or less.In short, these single-center retrospective chart review studies contained similar patient numbers to our study and also observed no significant association between preoperative intra-articular corticosteroid injections and an increased postoperative infection rate.
Conversely, two larger studies utilizing administrative claims data have demonstrated a link between preoperative intra-articular corticosteroid injections and increased rates of postoperative infection. Cancienne et al. found a statistically significant increase in the rates of postoperative infection among 5,313 patients who had received an injection within three months of surgery and also in 8,919 patients who received an injection between three and six months before surgery compared to 13,650 matched controls who did not receive an injection. They reported no statistically significant increase in infection rate among 8,008 patients who received their injections between six and twelve months before surgery. In another study looking at 29,603 patients with an injection and 54,081 without, Bedard et al. found a statistically significant increased risk of infection with an injection before surgery. When the injection cohort was stratified into time periods, the association persisted for an injection within up to six months of surgery.Our study found no association of infection from injections at any time period prior to patients’ TKA (Table 3).
Both Cancienne’s and Bedard’s groups discussed the limitations of these large database studies, which included a dependence on proper coding, a lack of demographic data, and an inability to differentiate the specific site or contents of the injections. The advantage of our smaller, single-centered study is that we were able to address all of these issues.
The control group of this study was both older and contained a greater percentage of male patients. Though age alone has not been shown to be associated with an increased risk of PJI, male sex has been identified as a risk factor[20,21]. Despite this, binomial regression found that neither age nor sex were independent risk factors for PJI in this study. Hence, differences in sex between the two cohorts had no significant impact on the outcome of this study. A new meta-analysis including the more recent smaller scale studies could potentially overcome these limitations while evaluating a larger, more generalizable population.