Background. Much effort has been aimed at strategies for patient optimization, perioperative standards of care, and postoperative risk stratification to reduce the incidence of SSI. Examples include, newer dressing modalities, antibiotic-impregnated bone cement, intra-wound powdered antibiotics, as well as novel suture types and techniques, all of which have shown great potential. However, the question remains as to whether these changes in practice have led to lower overall infections over the past few years. Therefore, the purpose of this study was to track the annual rates and trends of: 1) overall; 2) deep; and 3) superficial SSI following total hip arthroplasty (THA) using the most recent data (2012 to 2016) from a large nationwide database. Methods. The National Surgical Quality Improvement Program database was queried for all primary THAs (CPT code 27130) between 2012 and 2016, yielding 122,451 cases. Cases with reported superficial and/or deep SSIs were combined for an overall rate, and then independently analyzed as deep and superficial SSIs. The infection incidence for each year was calculated. After an overall 5-year correlation and trends, univariate analysis was also performed to compare the most recent year, 2016, with each of the preceding 4 years. Furthermore, a comparison of overall and deep SSI incidences from this study were compared to meta-analysis of pooled data from 2001 to 2011. Pearson correlation coefficients and chi-squared tests were used to determine correlation and statistical significance which was maintained at a p-value less than 0.05. Results. Over the 5-year period, 1,154 cases out of 122,451 (0.94% of all cases) were complicated by any SSI. The lowest incidence was in the latest year, 2016 (n=289, 0.81%), while the greatest was in the earliest year, 2012 (n=163, 1.12%). There was a significant inverse correlation between overall SSI rate and year (p<0.01). A 31% decrease in rate was found between 2016 and 2012 (0.81% vs. 1.12%, p<0.01). For deep SSI, the lowest incidence was in the most recent year, 2016 (n=82, 0.23%). The incidence over 5 years was 0.30% (364 out of 122,451 cases). The mean percent decrease in deep SSI incidence over the 5 years was 31%. There was a 49% decrease in deep SSI rate in 2016 compared to 2015 (0.23% vs. 0.38%, p>0.05). Additionally, there was an inverse correlation between deep SSI rate and year of surgery (p>0.05). The lowest superficial SSI incidence occurred in the most recent year, 2016 (n=204, 0.58%), while 2012 had the greatest incidence (n=121, 0.83%). There were a total of 796 cases out of 122,451 over 5 years, an incidence of 0.65%. A 31% decrease was observed between 2016 and 2012 (0.58% vs. 0.83%, p=0.001). There was a statistically significant inverse correlation between superficial SSI rate and year (p<0.01). A meta-analysis evaluating primary THA SSIs from 2001 to 2011 reported an overall SSI incidence of 2.5% (95% confidence interval [Cl], 1.4%-4.4%; P<.001; n=28,883), substantially higher (309%) than the 2016 incidence of 0.81% found in this study. Furthermore, the meta-analysis reported an incidence for deep SSIs to be 0.9% (95% Cl, 0.4%-2.2%; p<.001; n=28,883), also found to be markedly lower than the 2016 incidence noted here (0.23%), marking a 391% difference. Conclusion. The findings from this study suggest that the evolving standards of care have brought about improvements in SSI prevention following THA over time. Deep SSIs, which can pose substantial threats to implant survivorship, have decreased throughout the years. These results highlight the importance of following up-to-date clinical recommendations to reduce surgical site infections and substantially improve patient outcomes
