Who is at Risk for Implant Irritation After Fixation of a Tibial Tubercle Fracture? A Multicenter Study

Background: Tibial tubercle fractures are typically treated surgically with screws. Implant irritation is the most common complication. However, detailed investigation of this problem is challenging, since most research is limited to small, single-center studies. Understanding who is at the highest risk may improve patient counseling and potentially guide surgical techniques. The purpose of this study is to identify risk factors for implant irritation in patients undergoing fixation of tibial tubercle fractures. Methods: This retrospective cohort study included tibial tubercle fractures fixed with screws at 7 tertiary children's hospitals in the Tibial Tubercle Study (TITUS) Group. Exclusion criteria included age 18 years or older, primary fixation with nonscrew implants, or <6 months of follow-up. Demographic, perioperative, and postoperative data was collected. The primary outcome of interest was postoperative implant irritation. Univariable analysis was followed by multivariable regression to adjust for confounders. Odds ratios (OR) are reported with 95% CIs. Results: Of the 475 patients included, implant irritation was reported in 12.8% while 10.7% subsequently underwent unplanned removal. Patients weighing <70 kg reported more irritation than those weighing 70 kg or more (17.3% vs. 9.4%, P=0.01). However, in patients weighing <70 kg, there was no difference in the rate of symptomatic implants when stratifying by screw size. White patients reported more irritation than nonwhite patients (24.8% vs. 9.6%, P<0.001). Significant institutional variation in implant irritation rates was reported, ranging from 0% to 29% (P=0.004). Screw number, size, configuration, washer use, or pre-existing Osgood-Schlatter syndrome were not associated with symptomatic implants. When adjusting for confounders in multivariable analysis, white patients (OR: 3.2, 95% CI: 1.5-6.6; P=0.002) and those weighing <70 kg (OR: 2.2, 95% CI: 1.2-4.2; P=0.02) had higher odds of experiencing implant irritation. One of the 7 study sites was also independently associated with increased odds of symptomatic screws (OR: 7.8, 95% CI: 1.1-54.9; P=0.04). Conclusions: Implant irritation was reported by 12.8% of patients following screw fixation of a tibial tubercle fracture. Even when accounting for institutional variability, white patients and those weighing <70 kg had higher odds of symptomatic screws. This information can be used to enhance patient counseling and potentially adjust surgical techniques in some patients. Level of Evidence: Level III.