The Impact of Transitioning From ICD-9 to ICD-10 on Reported Complications Rates Following Primary Total Knee Arthroplasty

Abstract Background In 2015, the healthcare system transitioned from International Classification of Diseases, Ninth Revision (ICD-9) coding to the Tenth Revision (ICD-10). We sought to determine the effect of this change on the incidence of complications following total knee arthroplasty (TKA). Methods The Humana administrative claims database was queried from 2-years prior to October 1, 2015 (ICD-9 cohort) and for 1-year after this date (ICD-10 cohort) to identify all TKA procedures. Complications occurring within 6 months of surgery were captured using the respective coding systems. Incidence of each complication were compared between cohorts using risk ratios (RR) and 95% confidence intervals. Results There were 19,009 TKAs in the ICD-10 cohort and 38,172 TKAs in the ICD-9 cohort. The incidence of each complication analyzed were significantly higher in the ICD-9 cohort relative to the ICD-10 cohort. PJI occurred in 1.9% vs 1.3% (RR 1.5, 1.3-1.9), loosening in 0.3% vs 0.1% (RR 2.7, 1.8-4.9), periprosthetic fracture in 0.3% vs 0.1% (RR 3.0, 1.6-4.5) and other mechanical complications in 0.7% vs 0.4% (RR 2.0, 1.5-2.5), respectively (p Conclusion The transition from ICD-9 to ICD-10 coding has altered the reported incidence of complications following TKA. These results are likely due to the added complexity of ICD-10 which is joint and laterality specific. It is important to understand the differences between coding systems as this data is used for quality initiatives, risk adjustment models and clinical research. Thoughtful methodology will be necessary when ICD-9 and ICD-10 data are being analyzed simultaneously.