Time trends in total ankle arthroplasty in the USA: a study of the National Inpatient Sample

The objective of this study was to assess the time trends in utilization, clinical characteristics, and outcomes of patients undergoing total ankle arthroplasty (TAA) in the USA. We used the Nationwide Inpatient Sample (NIS) data from 1998 to 2010 to examine time trends in the utilization rates of TAA. We used the Cochran Armitage test for trend to assess time trends across the years and the analysis of variance (ANOVA), Wilcoxon test, or chi-squared test (as appropriate) to compare the first (1998-2000) and the last time periods (2009-2010). TAA utilization rate increased significant from 1998 to 2010: 0.13 to 0.84 per 100,000 overall, 0.14 to 0.88 per 100,000 in females, and from 0.11 to 0.81 per 100,000 in males (p<0.0001 for each comparison for time trends). Compared to the 1998-2000 period, those undergoing TAA in 2009-2010 were older (41 % fewer patients <50 years, p<0.0001), less likely to have rheumatoid arthritis as the underlying diagnosis (55 % fewer patients, p=0.0001), more likely to have Deyo-Charlson index of 2 or more (197 % more, p=0.0010), and had a shorter length of stay at 2.5 days (17 % reduction, p<0.0001). Mortality was rare ranging from 0 to 0.6 % and discharge to inpatient facility ranged 12.6-14.1 %; we noted no significant time trends in either (p>0.05). The utilization rate of TAA increased rapidly in the USA from 1998 to 2010, but post-arthroplasty mortality rate was stable. Underlying diagnosis and medical comorbidity changed over time and both can impact outcomes after TAA. Further studies should examine how the outcomes and complications of TAA have evolved over time.