Background: Recent studies have shown that intra-articular injections ≤3 months before total knee arthroplasty increase the risk of periprosthetic joint infection. We are aware of no previous study that has differentiated the risk of periprosthetic joint infection on the basis of the type of medication injected. In addition, we are aware of no prior study that has evaluated whether hyaluronic acid injections increase the risk of infection after total knee arthroplasty. In this study, we utilized pharmaceutical data to compare patients who received preoperative corticosteroid or hyaluronic acid injections and to determine whether a specific injection type increased the risk of periprosthetic joint infection. Methods: Patients undergoing unilateral primary total knee arthroplasty were selected from a nationwide private insurer database. Ipsilateral preoperative injections were identified and were grouped by medication codes for corticosteroid or hyaluronic acid. Patients who had received both types of injections ≤1 year before total knee arthroplasty were excluded. The outcome of interest was periprosthetic joint infection that occurred ≤6 months following the total knee arthroplasty. The risk of periprosthetic joint infection was compared between groups (no injection, corticosteroid, hyaluronic acid) and between patients who received single or multiple injections. Statistical comparisons were performed using logistic regression controlling for age, sex, and comorbidities. Results: A total of 58,337 patients underwent total knee arthroplasty during the study period; 3,249 patients (5.6%) received hyaluronic acid and 16,656 patients (28.6%) received corticosteroid ≤1 year before total knee arthroplasty. The overall infection rate was 2.74% in the no-injection group. Multivariable logistic regression showed independent periprosthetic joint infection risk for both corticosteroid (odds ratio [OR], 1.21; p = 0.014) and hyaluronic acid (OR, 1.55; p = 0.029) given ≤3 months before total knee arthroplasty. There was no increased risk with injections >3 months prior to total knee arthroplasty. Direct comparison of corticosteroid and hyaluronic acid showed no significant difference (p > 0.05) between medications or between single and multiple injections. Conclusions: Preoperative corticosteroid or hyaluronic acid injection ≤3 months before total knee arthroplasty increased the risk of periprosthetic joint infection. There was no difference in infection risk between medications or between multiple and single injections. On the basis of these data, we recommend avoiding both injection types in the 3 months prior to total knee arthroplasty. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

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Introduction: Femoral lengthening is performed by distraction osteogenesis via lengthening over a nail (LON) or by using a magnetic lengthening nail (MLN). MLN avoids the complications of external fixation while providing accurate and easily controlled lengthening. However, the increased cost of implants has led many to question whether MLN is cost-effective compared with LON. Methods: A retrospective review was performed comparing consecutive femoral lengthenings using either LON (n = 19) or MLN (n = 39). The number of surgical procedures, time to union, and amount of lengthening were compared. Cost analysis was performed using both hospital and surgeon payments. Costs were adjusted for inflation using the Consumer Price Index. Results: No difference was observed in the length of femoral distraction. Patients treated with MLN underwent fewer surgeries (3.1 versus 2.1; P < 0.001) and had a shorter time to union (136.7 versus 100.2 days; P = 0.001). Total costs were similar ($50,255 versus $44,449; P = 0.482), although surgeon fees were lower for MLN ($4,324 versus $2,769; P < 0.001). Discussion: Although implants are more expensive for MLN than LON, this appears to be offset by fewer procedures. Overall, the two procedures had similar total costs, but MLN was associated with a decreased number of procedures and shorter time to union. Level of Evidence: III